Hand-book of household science: a popular account of heat, light, air, aliment, and cleansing in their scientific principles and domestic applications

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X

V

THE

HAND-BOOK

HOUSEHOLD SCIENCE.

A POPULAE ACCOUNT OF

HEAT, LIGHT, AIR, ALIMENT,
AND CLEANSING,

THEIR SCIENTIFIC PKINCIPLES AND DOMESTIC APPLICATIONS.
WITH NTJMEEOFS ULTJSTEATIVE DIAGRAMS.

ED^i^lgQ^. YOUMANS,

AUTHOE OF

"the class-book op chbmistbt," "chemical atlas" and "chabt,"
"alcohol and thh oonsto^ij^oh <oer*aSS.1f

NEW YORK :
D. APPLETON" & CO., 346 & 848 BROADWAY.

LONDON: 16 LITTLE BRITAIN.

1857.

Entered according to Act of Congress, in the year 1857, by

D. APPLETON & CO.,

In the Clerk's Office of the District Court of the United States for the

Southern District of New York.

An edition of the present loorJc has been issKecl,
arranged with Questions for the use of Academies, /Semi-
naries, and Schools.

OOI^TENTS

PART I.— HEAT.

PAGB

PREFACE, 1

INTRODUCTION, 11

I. Sources and Distribution of Terrestrial Heat, .... 17
II. Inflttencb of Heat upon the Living World, . . . . 19

III. Measurement of Heat — The Thermometer, 23

IV. Radiation and its Effects, ... - 27

V. Conduction of Heat, and its Effects, 34

VI. Heat conveyed bx moving Matter, 36

VII. Various properties and effects of Heat, 37

VIII. Physiological effects of Heat, 48

IX. Artificial Heat — Properties of Fuel, 49

X. Air-currents — Action and management of Chimneys, . . . 55

XI. Apparatus of Warming, 60

1. Open fireplaces, 62

2. Stoves 67

3. Hot-air arrangements, 70

PART II.— LIGHT.

I. Nature of Light — Law of its Diffusion, 76

II. Reflection of Light, 79

III. Transmission and Refraction of Light, 82

IV. Theory of Light — Wave movements in Nature, .... 84
V. Composition and mutual relation of Colors, 88

VI, Practical suggestions in combining Colors, . . . . 102

IV CONTENTS.

PAQB

VII. Peoduction of Artificial Light.

1. The Chemistry of Illumination, 105

2. Illumination by means of Solids, 103

3. Illumination by means of Liquids, 112

4. Illumination by means of Gases, 119

5. Measurement of Light, 124

VIII. Structure and Optical powers of the Eye, 126

IX. Optical defects of Vision — Spectacles, 131

X. Injurious action of Artificial Light, 137

XI. Management of Artificial Light, 146

PART III.— AIR.

I. Properties and composition of the Atmosphere, .... 150
II. Effects of the constituents of Air.

1. Nitrogen, . , . 154

2. Oxygen, 154

S. Moisture, 157

4. Carbonic acid, IGl

5. Ozone and electricity, . . " 164

III. Condition of Air provided by Nature, 165

IV. Sources of impure Air in Dwellings, 168

V. Morbid and fatal effects of impure Air, 174

VI. Rate of contamination within doors, 181

VII. Air in Motion — Currents — Draughts, 185

VIII. ARRi\jfGEMENTS for Ventilation, . 192

PART IV.— ALIMENT.

I. Source of Aliments — Order of the subject, 205

II. General properties of Alimentary Substances.

1. Principles containing no Nitrogen.

A Water, ... 207

B The Starches, 213

C The Sugars, 216

D The Gums, 223

E The Oils, . 223

F The Vegetable Acids, 225

2. Principles containing Nitrogen.

A Vegetable and Animal Albumen, 227

B Vegetable and Animal Casein, 223

C Vegetable and Animal Fibrin, 228

D Gelatin, 280

CONTENTS.

8. Compound Aliments— Vegetable Foods.

A The Grains, 231

B Leguminous Seeds, 241

C Fruits, 243

D Leaves, Leafstalks, etc., 244

E Roots, Tubers, Bulbs and Shoots, 245

4. Compound Aliments — Animal Foods.

A Constituents of Meat, 248

. 250

256

. 259

262
. 267

271
. 274

277
. 281

285
, 287

289

. 293

298

. 800

302

. 306

809
. 311

314
. 818

324
. 330

335
. 344

347
. 353

B Production and composition of Milk,
IIL CuLiNAET Changes of Alimentary Substances.

1. Combining the elements of Bread,

2. Bread raised by Fermentation,
8. Properties and action of Yeast, . . ...,,

4. Raising Bread without Fermentation,

5. Alterations produced in baking Bread,

6. Iniiuence of foreign substances upon Bread,

7. Vegetable Foods changed by boiling,.

8. How cooking changes Meat,

9. Preparation and properties of Butter,
10. Preparation and properties of Cheese, .

rV. Common Bevehages.

1. Properties and preparation of Tea, .

2. Properties and preparation of Coffee,

3. Cocoa and Chocolate,

V. Peeseevation of Alimentaet Substances.

1. Causes of their Changeableness,

2. Preservation by exclusion of Air,

3. Preservation at Low Temperatures,

4. Preservation by Drying, ....

5. Preservation by Antiseptics

6. Preservation of Milk, Butter, and Cheese,
VI. Materials of Culinaett and Table Utensils, .

VII. Physiological effects of Food.

1. Basis of the demand for Aliment,

2. Digestion— Changes of food in the Mouth, .

3. Digestion— Changes of food in the Stomach,

4. Digestion— Changes of food in the Intestines,

5. Final destination of Foods, ....

6. Production of Bodily Warmth,

Production of Bodily Strength, 360

VI CONTENTS.

PAGE

8. Mind, Body, and Aliment, 364

9. Influence of Special Substances.

A Saline Matters, 869

B Liquid Aliments, 874

C Solid Aliments 383

10. Nutritive value of Foods, 892

^ 11. The Vegetarian Question, 402

12. Considerations of Diet, 408

PART v.— CLEANSING.

I. Principal Cleansing Agents, 422

II. Cleansing of Textile Aeticles, 428

III. Cleansing of the Peeson, 431

IV. Cleansing of the Air, 436

V. Poisons, 441

APPENDIX 443

INDEX, 445

PKEFACE.

A DESiEE to prepare a better statement than has hitherto
been offered, of the bearings of science upon the economy of
the household, has led to the following work. The purpose
has been, to condense within the limits of a convenient manual
the largest possible amount of interesting and valuable scien-
tific information of those agents, materials, and operations in
which we have a concern, chiefly as dwellers in houses.

The subjects are treated somewhat in an elementary way,
but with constant reference to their domestic and practical
relations. Principles are universal; their applications are
special and peculiar. There are general laws of light, heat,
and air, but they may be studied in various connections.
There are many things about them which a person, as a resi-
dent of a house, cares little to know ; while there are others
in which he has a profound interest. To consider these, we
assume to be the province of household science. The question'
of moisture in the air, for example, is one of universal scien-
tific interest to meteorologists ; but it has also a special and
vital import for the occupants of stove and furnace heated
rooms. Different colors, when brought together, alter and
modify each other according to a simple and beautiful law ;
and the Painter, the Decorator, and the Dyer, have each a
technical interest in the principle ; but hardly more than the
Lady at her toilette or engaged in furnishing her house. The
Agriculturist is interested in the composition of food, as a
•producer ; the Householder equally, as a consumer. The

Vm PREFACE.

Doctor must know the constituents of air and its action upon
the living system for professional purposes, and he studies
these matters as parts of his medical education ; but for the
same reasons of life and death, the inhabitants of houses are
concerned to understand the same things.

These examples illustrate the leading conception of the
present work. Its preparation has been attended with grave
difficulties. Of course, a volume of this compass can present
only a compend of the subjects it considers. Heat, light, air,
and aliment are topics of large extent, wide and complex in
their principles, which are of boundless apph cation. We do
not profess to have treated them with any completeness,
but only to have brought distinctly forward those aspects
which have been formerly too much neglected. In deciding
what to state, and what to omit, we have been guided by two
rules ; Jirst^ to present such facts and principles as have the
directest bearing upon household phenomena ; and, second, to
bring into prominence many important things not found in
common books nor included in the ordinary range of school
study. As elementary principles may be found fully treated
elsewhere, we have been brief in their statement, thus gaining
opportunity for important hints and views not generally acces-
sible. Our chemistries are deficient in information of the
composition and properties of food, while the physiological
class-books are equally meagre in statements of its effects ;
we have accordingly dwelt upon these points with something
of the fulness which their importance demands. So with
heat, hght, and air. It is hoped that the following pages will
vindicate the fidelity with which we have labored to enrich the
volume with new and valuable facts and suggestions, not pro-
curable in our family manuals or school class-books. Many
of the subjects presented have recently undergone searching
investigation. They are rapidly progressive ; facts are multi-
plying, and views widening. We have spared no pains to
give the latest and most authentic results. Although the vol-
ume is to a great extent self-explanatory, and adajited for
family and general reading, yet in the proper order of school

PEEFACE. U

Study it will find its most appropriate place after a course of
elementary lessons in cliemistry and physiology.

We have striven to present the subject in such a manner
as to make reading and study both agreeable and instructive.
Technical terms constitute a formidable obstacle, on the part
of many, to the perusal of scientific books. This is a very
serious difficulty, and requires to be managed as best we can.
In works designed for general use they should be avoided as
far as possible, and yet it is out of the question to think of
escaping them entirely. If we would enjoy the thoughts of
science we require to learn at least a portion of the language in
which alone these thoughts are conveyed. The new objects
and relations must be named, or they cannot be described and
considered. We have studiously avoided obstructing the
course of the common reader with many technical words, yet
there are some which it was impossible to omit. The terms
carbon, oxygen, hydrogen, nitrogen, carbonic acid, and some
others, though hardly yet famiUarized ui popular speech, must
soon become so. They are the names of substances of univer-
sal interest and importance ; the chief elements of air, water,
food, and organized bodies by which Providence carries on
the mighty scheme of terrestrial activity and life. They are
the keys to a new department of intellectual riches — the latest
revelation of time respecting the conditions of human exist-
ence. The time has come when all who aspire to a character
for real intelligence, must know something of the objects
which these terms represent.

As respects the body of its facts and principles, any work
of this kind must necessarily be of the natm-e of a compilation.
We make no claim to discovery. The materials of the volume
— ^the result of laborious and life-long investigations of many
men — have been gathered from numberless sources, — from
standard books upon the various topics, scientific magazines,
original memoirs, personal correspondence, observation, house-
hold experience and laboratory examinations. Constant refer-
ence is made to authorities followed, and the language of
others employed whenever it appeared to convey the most
1*

X PKEFACE,

suitable statement. Exemption from errors can hardly be
expected m a work of this kind — errors of oversight and
errors of judgment. Besides, many of its questions are in an
unsettled state and involve conflicting views. Yet the utmost
care has been taken to make an accurate and reUable presenta-
tion of the subjects considered.

The Author desires to acknowledge his indebtedness to
his sister, Eliza A. Youmaks, for constant and invalua-
ble aid in the preparation of the work, not only in various
experimental operations incident to its progress, but also in
several parts of its hterary execution. To his friend Mr.
Richard H. Manning, who, though engaged in absorbing
mercantile pursuits, has yet found time for thought in the di-
rection of science and its appHcations, his thanks are due for
valuable suggestions and important manuscript corrections.

If the work shall serve, in however small a degree, to ex-
cite thought, to give additional interest to household phe-
nomena, and awaken a stronger desire for domestic improve-
ment, the labor of its preparation will not have been performed
in vain.

New Yoek, Augiist, 1857.

INTRODUCTION.

When a work is presented, claiming place in a systematic course of
Bcliool study, two questions at once arise in the mind of the discrimi-
nating educator : Jirst^ what is the nature, rank, and value of the
knowledge it imparts? and, second, what wiU be its general mfluence
upon the mind of the student ? In this twofold connexion there are
some thoughts to which we solicit the reader's earnest and considerate
attention.

The present volume has been prepared under a conviction that the
knowledge it communicates is first in the order of importance among
things to be considered by rational and civilized people. "Every
man's proper mansion-house and home," says Sir Henet "Wotton",
" is the theatre of his hospitality, the seat of self-fruition, the com-
fortablest part of his own life, the noblest of his son's inheritance, a
kind of private princedom ; nay, to the possessors thereof an epitome
of the whole worid." Nothing needs to be added in eulogy of the
household home, the place of life's purest pleasures and sweetest ex-
periences, the perpetual rallying point of its hopes and joys. What-
ever can render it more pleasant or attractive, or invest it with a new
interest, or in any way improve or ennoble it, is at once commended
to our sympathy and regard. To consider all the agencies which in-
fluence the course and character of household life, is far from the ob-
ject of the present work. Our concern is chiefly with its more mate-
rial circumstances and conditions. That we should understand some-
thing of the wonderful physical agencies which have control of our
earthly being, and which are so incessantly illustrated in the dwelling,
and be at least partially acquainted with those fixed natural ordi-
nances upon which our daUy welfare, comfort, health, and even life,
immediately depend, must certainly be acknowledged by all. One of
the most startling facts of man's history is, that placed in a world of
immutable order, and endowed with such exalted gifts of understand-

XU INTEODUCnON.

ing and reason, he should yet have contrived to maintain so dense and
perfect an ignorance of himself and the familiar objects by which he
is surromided. That exact knowledge of the ways of nature which puts
her powers at human command, and hears the daily fruit of substan-
tial improvement and universal beneficence, would seem to be the last
and noblest achievement of mind; a fruition of long intellectual
growth, the highest form in the latest time, after the prehminary and
preparatory experience of ages. In its earlier strivings we observe
the mind of man intently occupied with itself, and regarding material
nature with unutterable disdain. It wandered aimless and dissatisfied
in the misty regions of speculation. Its first great conquest was in
the reahn of abstraction, farthest removed from the vxdgarities of
mere matter — the discovery of mathematical principles. The earhest
application of thought to physical subjects was away in the distant
spheres, where imagination had revelled wildest from immemorial time,
to the luminous points and mysterious movements of the heavens,
which, according to Plato, were most admirably fitted .to illustrate
geometry. The skies were mapped and charted long before the earth.
OoPEENicTJS struck out the grand law of celestial circulation before
Haevet discovered that of the blood. The genius of Newton flashed
an immortal light upon the mechanism of the universe, many years
before Etjmfoed began his humbler domestic investigations. Centuries
have passed since the establishment of universal gravitation, while
there are men now living who may recollect the most gigantic stride
of modem science, the discovery of oxygen gas by Peiestly, and the
earliest analysis of the air we breathe. Chemistry, which is the name
given to the first serious grapphng of human intelligence with all
forms of common matter, belongs chiefly to our own century. This,
too, has been progressive, and in its course has conformed to the gen-
eral law we are indicating. Its earliest investigations were directed
to inert mineral substances, stones and rocks ; while the formal and
systematic elucidation of those conditions and phases of matter in
which we have the deepest interest — vegetable and animal compounds
and processes, agricultm*al, physiological, and dietetical chemistry — ^is
eminently an affair of our own day. Thus, the spirit of inquiry, at
first recoiling from matter, and circling wide through metapliysical
vacuities, gradually closed with the physical world, and now finds its
last and highest inquest into tlie material conditions of man's daily
life. The course of knowledge has been expansive, as weU as pro-
gressive ; from narrow views to universal principles ; from empty
speculations to world-wide utilities ; from the pleasure of a few to

rNTKODucnoN. xm

the advantage of the many ; from utter ignorance and contempt of
nature, to the revelation of all-embracing laws, and a beautiful and
harmonious order in the commonest objects and operations of daily-
experience. To the truth of this general statement, the existence of
the present book may be taken as a strong attestation. The mass of
its facts and principles are the result of recent investigation. A
hundred years ago such a work would have been, in all its essential
features, a blank impossibility; indeed, it had lacked its richest mate
rials if prepared for the last generation.

These facts should not be without their influence upon the schemt
of popular education. It is its first duty to communicate that infor-
mation which can be reduced to daily practice, and yield the largest
measure of positive good. If recent inquiry has opened new treasures
of available truth, it is bound to take charge of them for the general
benefit. It must report the advance of knowledge, and keep pace
with the progress of the human mind, or it is false to its trust. The
subjects of study should be so modified and extended as to afibrd the
largest advantage, intellectual and practical, of the labors of the great
expounders of nature, — especially in those departments where knowl-
edge can be made most useful and improving. A rational and com-
prehensive plan of education for all classes, which shall be based upon
man's iutrinsio and essential wants, and promptly avail itself of every
new view and discovery in science, to enlighten him in his daily rela-
tions and duties, is the urgent demand of the time. Nor can it be
always evaded. We are not to trundle round for ever in the old ruts of
thought, clinging with blind fatuity to crude schemes of instruction,
which belong, where they originated, with the bygone ages. He who
has surrendered his life to the inanities of an extinct and exploded
mythology, but who remains a stranger to God's administration of
the living universe ; who can skilfully rattle the skeletons of dead lan-
guages, but to whom the page of nature is as a sealed book, and her
voices as an unknown tongue, is not always to be plumed with the
supereminent designation of ' educated.'

There are many things, unquestionably, which it would be most
desirable to study : but opportunity is brief, and capacity limited ;
and the acquisition of one thing involves the exclusion of another. We
cannot learn every thing. The question of the relative rank of vari-
ous kinds of knowledge — what shall be held of primary importance
and what subordinate, is urgent and serious. As hfe and health are
the first of all blessings, to maintain them is the first of all duties,
and to understand their conditions the first of mental requirements.

XIV INTEODUCnON.

Shall the thousand matters of mere distant and curious concernment
be suffered to hold precedence of the solemn verities of being which
are woven into the contexture of familiar life ? The physical agents
■which perpetually surround, and act upon, and within us, heat, light,
air, and aliment, are hable to perversion through ignorance, so as to
produce suffering, disease, and death; or they are capable through
knowledge of promoting health, strength, and enjoyment. What
higher warrant can be asked that their laws and effects shall become
subjects of general and earnest study. It may seem strange that in
regard to the vital interests of life and health, man should be left
without the natural guidance of instinct, and be driven to the necessity
of reflection and study ; that he for whom the earth seems made
should be apparently less cared for in these respects than the inferior
animals. Nevertheless, such is the divine ordination. Neither our
senses, instincts, nor uninstructed faculties are sufficient guides to good,
or guards from evil, in even the ordinary conditions of the civilized
state. Things which most deeply affect our welfare, the senses fail to
appreciate. They can neither discern the properties nor the presence
of the most deadly agents. The breathing medium may be laden with
noxious gases to the peril of life, and the senses fail to detect the dan-
ger. Hunger and thirst impel us instinctively to eat and di'ink, but
they fail to inform us of the nutritive value of alimentary substances
or their dietetical fitness to our varying requirements. Tor aU those
things which are independent of man's will. Providence has taken
abundant care to provide ; while in the domain of voluntary action,
blind instinct is replaced by rational forecast. Whatever may have
been those original conditions of bare animal existence which some
yet sigh for, as the ' true state of nature,' we are far removed from
them now. They have been successively disturbed as, generation
after generation, intelligent ingenuity has been exercised to gain con-
trol of natural forces for the securing of comforts and luxuries, and
to liberate man from the privations and drudgeries of the uncivilized
condition. But unmingled good seems not permitted ; the benefits are
alloyed with evU. Thus, the introduction of the stove, while afford-
ing the advantage of economy and convenience in the management
of fire, was a step backward in the matter of ventilation. Gas-
lighting was a great advance on the methods of artificial illumination,
but there came with it augmented contamination of the breathing
medium and new dangers to the eyes. Against these and similai* in-
cidental mischiefs — ' residues of evil ' that accumulate against the pre-
dominating good, there is no other protection than intellect, instructed

rNTEODUCnON. xn

in the material conditions wMcli influence our health and life. For
these, and kiudred considerations of practical moment to all who oc-
cupy dwellings and assume civilized relations, we urge the study
of TiomeTiold science as an essential part of general education.

It deserves to be better understood, that the highest value of science
is derived from its power of advancing the public good. It is more
and more to be consecrated to human improvement, as a sublime re-
generative agency. Workiog jointly and harmoniously with the great
moral forces of Christian Civilization, we believe it is destined to effect
extensive social ameliorations. That it is not yet fully accepted in this
relation is hardly surprising. The work of presenting scientific truth
in those forms which may best engage the popular mind, is not to be
fairly expected of those who give their lives to its original development.
There is a deep satisfaction, an intrinsic compensating interest to the
discoverer in the naked quest of truth, which is largely independent of
any utility that may flow from the inquiry. In the exalted conscious-
ness of achievement, the man of science finds an intellectual remunera-
tion, so royal and satisfying that other considerations have compara-
tively little weight. Hence the indifference, to a great degree inevi-
table, with which original explorers contemplate the reduction of sci-
entific principles to practical use. Moreover, this utter carelessness of
results, where the mind is not biased, nor the vision blurred by ulterior
considerations, is far the most favorable for successful investigation.
Conscious that the effects of his labors are finally and always beneficial
in society, the enthusiast of research may be excused his indifference
to their immediate reception and uses. But the formal denial that the
allegiance of mind is supremely due to the good of society is quite
another affair. The sentiment too widely entertained in learned and edu-
cational circles, that knowledge is to be firstly and chiefly prized for its
own sake, and the mental gratification it produces, we cannot accept.
The view seems narrow and illiberal, and is not inspired of human sym-
pathy. It took origin in times when the improvement of man's con-
dition, his general education and elevation, were not dreamed of. It
came from the ancient philosophy, which was not a dispensation of pop-
ular beneficence, an all-diffusive, ennobling agency in society, but con-
fessed its highest aim to be a personal advantage, shut up in the indi-
vidual soul. It was not radiant and outflowing like the sun, but drew
all things inward, engulfing them in a malstrom of selfishness.

The baneful ethics of this philosophy have given place to the higher
and more generous inculcations of Christianity, which lays upon hu-
man nature its broad and eternal requirement, ' to do good.' From

XVI mTKODUCnON.

this authoritative moral demand science cannot be exempted. The
power it confers is to be held and used as power is exercised by God
himself, for pm*poses of universal blessing.

We place a high estimate upon the advantages which society may
reap from a better acquaintance with material phenomena, for life is a
stern realm of cause and effect, fact and law. To the poetic day-dreamer
it may be an affair of sentiment, an ' illusion,' or a ' vapor,' but to
the mass of mankind, life is a solid,- unmistakable reality, that will not
dissolve into mist and cannot be conjured out of its qualities. As such,
we would deal with it in education, giving prominence to those forms
of knowledge which will work the largest practical alleviations and
most substantial improvement throughout the community. But it is
wisely designed that those studies which may become in the highest
degree useful are also first in intellectual interest. It is a grievous mis-
take to suppose that the study of natural science martyrizes the more
ethereal faculties of the soul, and dooms the rest to painful toil among
th.e naked sterilities of commonplace existence. So far from being un-
friendly to the imagination, as is sometimes intimated, science is its
noblest precursor and ally. Can that be unfavorable to this faculty,
which infinitely multij^lies its materials, and boundlessly amplifies its
scope ? Can that be restrictive of mental sweep, which unlocks the
mysteries of the universe and pioneers its way far into the councils of
Omniscience ? Who was it that lifted the veil, and disclosed a new
world of exquisite order and beauty in all the commonest and vulgar-
est forms of matter, below the former reach of eye or thought ? Who
was it that dissipated the fabulous 'firmament,' which primeval igno-
rance had mounted over its central and stationary earth ; set the world
in motion, and unfolded a plan of the heavens, so appalling in ampli-
tude that imagination itself falters in the survey ? Who was it that
first read the handwriting of God upon the rocks, revealing tlie history of
our planet and its inhabitants through durations of which the mind had
never before even presumed to dream ? In thus unsealing the mysteries
of being — in turning the commonest spot into a museum of wonders —
who can doubt that science has opened a new and splendid career for
the play of the diviner faculties ; and that its pursuit aftbrds the most
exhilarating, as well as the healthiest and purest of intellectual enjoy-
ments ? Kor should we forget its elevating tendencies ; for in con-
templating the varied scheme of being around, its beauties, harmonies,
adaptations, and purposes of profoundest wisdom, the thoughts ascend
in unspeakable admiration to the infinite Source of truth and light.
We should educate and elevate our nature by these studies, storing our

rNTEODucnoN. xvn

minds with the richest materials of thought, enlarging our capacities
of henign exertion, and rising to a more intimate conmaunion with the
spirit of the Great Maker of all.

But heyond these considerations, physical science has another claim
upon the Instructor, in the kind and extent of the mental discipline it
affords. The study of mathematics has a conceded value in this rela-
tion, being eminently favorable to precision and persistence of the
mental operations — ^to steadfast concentration of thought upon ab-
stract and difficult subjects. But we hope not to incur the charge of
educational heresy,by expressing the opinion, that its training is some-
what defective — ^is neither sufficiently comprehensive, nor altogether
of the right kind. Its influence is limited to certain faculties only, and
the method to which it accustoms the mind is too little available in
grappling with the practical problems of life. The starting-point of
the mathematician is certain universal truths of consciousness, intui-
tive axioms — assumed without proof, because they are self-evident, and
therefore incapable of proof. From these, by various operations and
chains of reasoning, he proceeds to work out special applications. His
direction is from generals to particulars — it is inferential — deductive.
But when we come to deal with the phenomena of the external
world, and the actualities of daily experience, this plan fails, and we
are driven to the very reverse method. In the phenomenal world we
are without the eternal principles, settled and assumed at the outset ;
these become themselves the objects of investigation ; they have to be
established, and we must begin with particulars, special inquiries,
experimental investigations, the observation of facts, and from these
we cautiously proceed to general truths — to universal principles.
The process is an ascent from particulars — generalization — indiic-
tion. That the whole is greater than a part, or that two parallel lines
vdll never intersect each other, are irresistible intuitions, taken for
granted at once by all minds. But that matter attracts matter with
a force proportional to the square of its distance ; or that chemical
combination takes place in definite unalterable proportions, are truths
of induction — general laws, only arrived at after long and laborious in-
vestigation of particular facts. These are essentially opposite methods
of proceeding in different departments of inquiry, each correct in its
own sphere, but false out of it. The human mind started with the
mathematical method, and the greatest obstruction to the progress of
physical science for many centuries arose from the attempt to apply
it to outward phenomena ; that is, to assume certain principles as true
of the external world, and to reason from them down to the facts ; in-

XVIU rNTEODUCTION.

stead of beginning with the facts, and carefully evolving the general
laws. The splendid achievements of modern science are the fruit of
the inductive method. This should be largely joined with the mathe-
matical to secure a full and harmonious mental discipline. It edu-
cates the attention by establishing habits of accurate observation,
strengthens the judgment, teaches the supremacy of facts, cultivates
order in their classification, and develops the reason through the es-
tablishment of general principles. It is claimed, as an advantage of
mathematics, that it deals with certainties, and, raising the mind above
the confusions and insecurities of imperfect knowledge, habituates it
to the demand of absolute truth. That benefits may arise from this
exalted state of intellectual requirement, we are far from doubting,
and are conscious of the danger of resting satisfied with any thing
short of perfect certitude, where that 'can be attained. But here
again there is possibility of error. Mathematical standards and pro-
cesses are totally inapplicable in the thousand-fold contingencies of
common experience ; and the mind which is deeply imbued with its
spirit, is little attracted to those depai'tments of thought, where, after
the utmost labor, there still remain doubt, dimness, uncertainty and
entanglement. And yet, such is precisely the practical field in which
our minds must daily work. The mental discipline we need, there-
fore, is not merely a narrow deductive training of the faculties of cal-
culation,with their inflexible demand for exactitudes ; but such a sys-
tematic and symmetric exercise of its several powers as shall render
it pliant and adaptive, and train it in that class of intellectual opera-
tions which shaU best prepare it for varied and serviceable intellec-
tual duty in the practical afiairs of life.

There is still another thought in this connection which it is im-
portant should be expressed. It has been too much the pohcy of the
past so to train the mind as to enslave, rather than to arouse it. Edu-
cation, from the earliest time, has been imder the patronage of civU
and ecclesiastical despotisms, whose necessary policy has been tlie re-
pression of free thouglit. The state of mind for ever insisted on has
been that of submissive acceptance of authority. Instead of laying
open tlie limitations, uncertainties, and conflicts of knowledge, which
arise from its progressive nature, the spirit of the general teaching
has been that all tilings are settled, and that wisdom has reached its
last fulfilment. Instead of encouraging bold inquiry, and inciting to
noble conquest, the efltect lias rather been to reduce the student to a
mere tame, unquestioning recipient of established formulas and
time-honored dogmas. It is obvious on all sides that this state

INTRODUCTION. XLE

of things has been deeply disturbed. The introduction of Ee-
publicanism, with political freedom of speech and action; the
advent of Protestantism, with religious liberty of thought; and
the splendid march of science, which has enlarged the circle
of knowledge, multiplied the elements of power, and scattered social
and industrial revolution, right and left, for the last hundred years —
these new dispensations have invaded the old repose, and fired the
minds of multitudes with a new consciousness of power. Yet we
cannot forget that our education still retains much of its ancient
spirit, is yet largely scholastic and arbitrarily authoritative. "We
believe that this evil may be, to a considerable degree, corrected
by a frank admission of the incompleteness of much of our knowl-
edge; by showing that it ia necessarily imperfect, and that the
only just and honest course often involves reservation of opinion
and suspension of judgment. This may be consonant neither with
the teacher's pride nor the pupil's ambition, nevertheless it is
imperatively demanded. "We need to acquire more humility of
mind and a sincerer reverence for truth ; to understand that much
which passes for knowledge is unsettled, and that we should be
constant learners through life. The active influences of society,
as well as the school-room, teach far other lessons. "We are com-
mitted in early childhood to blind partisanships, — political and
religious, — and drive on through life in the unquestioning and unscru-
pulous advocacy of doctrines which are quite as likely to be false as
true, and are perhaps utterly incapable of honest definitive adjustment.
Science inculcates a different spirit, which is most forcibly illustrated
in those branches where absolute certainty of conclusion is diflacult of
attainment. Mr. Paget has urged the salutary influence of the study
of physiology in this relation. He says, " It is a great hindrance to the
progress of truth, that some men will hold with equal tenacity things
that are, and things that are not, proved ; and even things that, from
their very nature, do not admit of proof. They seem to think (and
ordinary education might be pleaded as justifying the thought) that a
plain ' yes ' or ' no ' can be answered to every question that can be
plainly asked ; and that every thing thus answered is to be maintained
as a point of conscience. I need not adduce instances of this error,
while its mischiefs are manifested every where in the wrongs done by
premature and tenacious judgments. I am aware that these are faults
of the temper, not less than of the judgment ; but we know how much
the temper is influenced by the character of our studies ; and I think
if any one were to be free from this over-zeal of opinion, it should be

XX INTKODUCnON.

one who is early instructed in an uncertain science such as physiology."
In the present work, the chief statements comprised under heat, light,
and air, may be regarded as settled with a high degree of certainty,
while much of the matter relating to food and its effects is less clearly
determined ; — its truth is only approximative, and we have stated it,
as such, without hesitation. While the reader is informed, he is at
the same time apprised of the incompleteness of his knowledge.

An important result of the more earnest and general pursuit of
science, by the young, vsdU be, to find out and develop a larger number
of minds having natural aptitudes for research and investigation. As
there are born poets, and born musicians, so also there are born in-
ventors and experimenters ; minds originally fitted to combine and
mould the plastic materials of nature into numberless forms of useful-
ness and value. It is a vulgar error that the work of discovery and
improvement is already mainly accomplished. The thoughtful well
understand that man has hardly yet entered upon that magnificent
career of conquest, in the peaceful domain of nature, to which he is
destined, and which will be hastened by nothing so much as a more
general kindling of the minds of the young with enthusiasm for science.
The harvest awaits the reapers — how strange that man should have
neglected it so long. Fuel, air, water, and the metals, as we see them
acting together, now, in the living, laboring steam-engine, have been
waiting from the foundation of the world for a chance to relieve man
of the worst drudgeries of toil. Long and fruitlessly did the sunbeam
court the opportunity of leaving upon the earth permanent impressions
of the things he revealed ; while the lightning, though seemingly a
lawless and rollicking spirit of the skies, was yet impatient to be
pressed into the quiet and useful service of man. Can there be a
doubt that other powers and forces, equally potent and marvellous,
await the discipline of human genius ? Not in vain was man called
upon, at the very morning of creation, to ' subdue the earth.' Already
has he justified the bestowmeut of the viceroyal honor : who shall
speak of the possibilities that are waiting for him in the future !

THE

HMD-BOOK OF HOUSEHOLD SCIENCE.

PAET FIEST.
HEAT.

I. SOUECES AND DISTRIBUTION OF TERRESTRIAL HEAT.

1. Ifatare of our Knowledge conceming Heat. — When we place the
hand upon a stove with a fire in it, a feeling of warmth is experienced,
while if it he made to touch ice, there is a sensation of cold. The im-
pressions are supposed to he caused in hoth cases by the same force or
agent ; in the first instance, the impulse passing from the heated iron to
the hand ; in the second, from the hand to the ice. "What the nature
or essence of this thing is, which produces such different feelings by
moving in opposite directions, and which makes the difference be-
tween summer and winter, nobody has yet discovered. It is named
heat. Some have conjectured it to be a kind of material fluid, exceed-
ingly subtle and ethereal, having no weight, existing diffused through-
out all things, and capable of combining with every known species of
matter ; and this supposed fluid has received the name of caloric.
Others thiok heat is not a material tlung, but merely motion : either
waves, or undulations produced in a universal ether, or a very rapid
vibration, or trembliag of the particles of common matter, which is in
some way contagious, and passes from object to object. Of the essen-
tial nature of heat we xmderstand nothing, and are acquainted only
with its effects: — our information is limited to its behavior. It resides
in matter, moves through it, and is capable of variously changing its
conditions. It is an agent producing the most wonderful results every
where ai'ound and even within us ; — a force of such tremendous energy,
such far-reaching, all-pervading influence, — that we may almost venture
to say it has been appointed to take control of the material universe ;

18 SOUECES OF TEEKESTEIAL HEAT.

wMle in the plan of the Creator, it is so disciplined to the eternal re-
straints of law, as to become the gentle minister of xmiversal benefi-
cence.

2. To what Extent the Earth Is wanned by the Sunt Heat comes
from the sun to the earth in streams or rays associated with light. It
has been ascertained by carefol measurement, that the quantity of
solar heat which falls upon a square foot of the earth's surface in a
year would be sufficient to melt 5400 lbs. weight of ice ; and as a
cubic foot of ice weighs 54 lbs,, the heat thus annually received would
melt a column of it 100 feet high, or a shell of ice enveloping our
globe 100 feet thick. As the sun turns aroimd once in 25 days, thus
constantly exposing different parts, we conclude that equal quantities
of heat are thrown from all portions of his surface, and are thus ena-
bled to calculate the total amount of heat which he imparts annually.
K there were a sphere of ice 100 feet in thickness completely sur-
rounding the sun, at the same distance from him as the earth's orbit,
his heat would be sufficient to melt it in the course of a year. This
quantity of heat would melt a shell of ice enveloping tJie sun's surface
38.6 feet thick in a minute, or 10.5 miles in thickness in a year. We
are, therefore, warmed" by heat-rays shot through a hundred million
miles of space, from a vast self-revolving grate having fifteen hundred
thousand miles of fire-surface heated seven times hotter than our
fiercest blast furnaces.

8. We get Heat also from the Stars. — Although the sun is the most
obvious and conspicuous source of heat for the earth it is by no means
its sole source. Of the enormous quantity of heat that streams away
in all directions from his surface, the earth receives but a small frac-
tion. But it is neither lost nor wasted ; he not only warms the earth,
but assists to warm the universe. Our globe catches a trifling portion
of his rays ; but the rest fly onward to distant regions, where all are
finally intercepted by the wandering host of orbs with which the
heavens are filled. And what the sun does, all the other stars and
planets are also doing. A mighty system of exchanges (32)* is estab-
lished among the bodies of space, by which each radiates heat to all
the rest, and receives it in turn from all the rest, according to the
measure of its endowments. The whole stellar universe thus contrib-
utes to our warmth. It is a startling fact, that if the earth were de-
pendent alone upon the sun for heat, it would not get enough to make
the existence of animal and vegetable life possible upon its surface.

* These numbers refer to paragraphs.

rrS UNEQUAL DISTEIBUnOK. 19

It results from the researchieg of Poutllet, that the starry spaces fur-
nish heat enough in the course of a year to melt a crust of ice upon
the earth 85 feet thick, almost as much as is supplied by the sun.
This may appear strange, when we consider how immeasurably small
must be the amount of heat received from any one of these distant
bodies. But the surprise vanishes, when we remember that the whole
firmament of heaven is so thickly sown with stars, that in some places
thousands are crowded together within a space no greater than that
occupied by the full moon. (Dr. Laedistee.)

4. Heat unequally Distributed upoa the Earth. — The quantity of heat
which the earth receives from the sun is very unequal at different
times and places. The earth turns around every day ; it is globular
in form, and is constantly changing the position of its surface in rela-
tion to the sun, as it travels about him in its annual circuit. The con-
sequence is, that we receive more heat during the day than at night ;
more at the equator than toward the poles ; more in summer than in win-
ter. "We are all aware that the temperature may fall from blood heat
at mid-day, to the point of frost or freezing at night ; and while at the
equator they have a temperature averaging, the year round, 81-5
degrees, at Few York (less than 3,000 miles north), the average annual
heat falls to 60 degrees ; and at Labrador (less than a thousand miles
farther north), the average temperature of the year sinks below freez-
ing. Nor do places at the same distance from the equator receive
equal amounts of solar heat. A great number of circumstances
connected with the surface of the earth, disturb its regular and uniform
distribution. Dublia for example, though between eight and nine
hundred miles farther from the equator than New York, has as high
a yearly temperature. Some places also experience greater contrasts
than others between the different seasons: thus while New York
has the summer of Rome, it has also the winter of Copenhagen.

II.— INFLUENCE OF HEAT UPON THE LIVING WOELD.

5. It Controls the Distribution of Vegetable Life. — ^It is this variable
quantity of heat received at different places and seasons, which deter-
miues the distribution of life upon the globe. Certain tribes of plants,
for example, flourish in the hot regions of the tropics, and cannot live
with a diminished^intensity of heat. Accordingly, as we pass to the
cooler latitudes, they disappear, and new varieties adapted to the new
conditions take their place. As we pass into stiU colder regions, these
again give way to others of a hardier nature, or which are capable of

20 nSTFLUENCE OF HEAT UPON THE LIVING WOELD.

living where there is less heat. As we proceed from the hot equator
to the frozen poles, or as we pass upward from the warm valley to the
snowy summit of a lofty mountain, we cross successive belts of varying
vegetation, which are, as it were, definitely marked off by the different
quantities of heat which they receive. " In the tropics wo see the
palms, which give so striking a characteristic to the forests, the broad-
leaved bananas, and the great climbing plants, which throw them-
selves from stem to stem, like the rigging of a ship. Next follows a
zone described as that of evergreen woods, in which the orange and
the citron come to perfection. Beyond this, another of deciduous
trees — the oak, the chestnut, and the fruit trees with which, in this
climate, we are so well acquainted ; and here the great climbers of
the tropics are replaced by the hop and the ivy. Still further advanc-
ing, we pass through a belt of conifers — ^firs, larches, pines, and other
needle-leaved trees — and these, leading through a range of birches,
which become more and more stunted, introduce us to a region of
mosses and saxifrages, but which at length has neither tree nor, shrub;
and finally, as the perpetual polar ices are reached, the red snow algae
is the last trace of vegetable organization."

6. Heat Regulates the Distribution of Animals. — It is the same also
with animal life. Difterent animated races are adapted to different
degrees of temperature, and belong within certain heat-limits, just like
plants. In going from the equator to the poles, different classes of
animals appear and fade away, as the temperature progressively de-
clines. Some are adapted to the alternations of winter and summer
by changes of their clothing ; and others, as birds, are pursued from
region to region by the advancing temperatures. Animals whose con-
stitutions are conformed to one condition of heat, if transported to
another, suffer and perish: while the lion is confined to his torrid
desert of sand, the polar bear is imprisoned in the frigid desert of ice ;
and, in both cases, the sunbeam is the chain by which they are bound.

7. Heat Influences Man's Physical DeTelopmcnt. — Nor does man fur-
nish an exception to these controlling effects of temperature. The
striking peculiarities of physical appearance and endowment, exhibited
by different tribes and communities of men, is well known ; and it has
long been understood that much of these differences is due to the all-
powerful influence of heat. " The intense cold, dwarfs and deforms the
inhabitant of the polar regions. Stunted, squat, large-headed, fish-
featured, short-limbed and stiff-jointed, he resembles in many points
the wolves and bears in whoso skins he wraps himself. As he ap-
proaches the sunny south, his stature expands, his limbs acquire shape

IT AFFECTS MIND AND CHAEACTEB. 21

and proportion, and his features are ameliorated. In the genial region,
he is heheld with that perfect conformation, that freedom of action
and intellectual expression, ia which grace and beauty consist."

8. Extremes of Dress in Diflfereut Localities. — The remarkable contrasts
of temperature which different races experience, is well illustrated by
their circumstances of dress. "While in the West Indian Islands a
single fold of cotton is often found to be an incumbrance, the Green-
lander wraps himself in layer after layer of wooUens and furs, fox-skins,
sheep-skms, wolf-skins, and bear-sMns, untU we might suppose him
well guarded against the cold ; yet with a temperature often a hundred
degrees below the freezing-point, he cannot always protect himself
against frozen extremities. Dr. Kane observes, " rightly clad, he is a
lump of deformity waddling over the ice: unpicturesque, uncouth,
-and seemingly helpless. It is only when you meet him covered with
frost, his face peering from an icy halo, his beard glued with frozen
respiration, that you look with inteUigent appreciation on his many-
coated panoply against king Death."

9. Temperatnre and Character. — The effect of cold is to benumb the
body and blunt the sensibihty ; whUe warmth opens the avenues of
sensation, and increases the susceptibility to external impressions.
Thus, the intensity with which the outward world acts upon the inward
through the sensory channels, is regulated by temperature. In cold
countries the passions are torpid and sluggish, and man is plodding,
austere, stolid, and unfeeling. "With the barrenness of the earth, there
is sterUity of thought, poverty of invention, and coldness of fancy.
On the other hand, the inhabitants of torrid regions possess feverish
sensibilities. They are indolent and effeminate, yet capable of furious
action ; capricious in taste, often ingenious in device ; they are extrav-
agant and wild in imagination, delighting in the gorgeous, the daz-
zUng, and the marvellous. In the medium heat of temperate climates,
these marked excesses of character disappear; there is moderation
without stupidity, and active enterprise without fierce impetuosity.
Society has more freedom and justice, and the individual more con-
stancy and principle : with loftiness of thought, there is also chastening
of the imagination. By comparing the effects of climate in the tor-
rid, temperate, and frigid zone, we observe the determining influence
of external conditions, not only upon the physical nature of man, but
over the mind itself. " We may appeal to individual experience for
the enervating effects of hot climates, or to the common understanding
of men as to the great control which atmospheric changes exercise,
not only over the intellectual powers, "but even on our bodily well-

88 TSTFLTTESCE OF HEAT UPON THE LIVING "WOELD.

being. It is within a narrow range of climate that great men have
been bom. In the earth's sonthern hemisphere, as yet, not one has
appeared ; and ia the northern, they come only \ri.thin certain paral-
lels of latitude. I am not speaMng of that class of men, who in all
ages and ia every conntry, have risen to an ephemeral elevation, and
have sunk agam into their native insignificance so soon as the causes
which have forced them from obscnrity cease, but of that other class
of whom God makes bnt one In a century, and gives hiTn a power of
enchantment over his fellows, so that by a word, or even by a look,
he can electrifv, and gnide, and govern mankind." — (Dr. Deapee.)

10. Inflaeaee of the Supply of Fuel. — The abundance or scarcity of the
snpply of fael, as it controls the amonnt of artificial heat, exerts a power-
fol influence upon the condition of the people in various ways ; indeed,
it may involve the health and personal comfort of whole nations, to
snch an extent, as even to contribute to the formation of national char-
acter. Where fuel is scarce, houses are small, and their occupants
crowded together ; the external air is as much as possible excluded ;
the body becomes dwarfed ; and the intellect duU. The diminutive
Laplander spends his long and dreary winter in a hut heated by a
smoky lamp of putrid oil ; an arrangement which afflicts the whole
nation with blear eyes. Scarcity of fuel has not been without its
effect in forming the manners of the polished Parisians, by transfer-
ring to the theatre and the cafe those attractions, which, in countries
where fuel is common and cheap, belong essentially to the domestic
hearth.

11. Temperature and Language. — AEBrmsroT suggested not only that
heat and air fashion both body and mind, but that they also have a
great effect in forming language. He thought the serrated, close
way of speaking among the northern nations, was owing to their
reluctance to open their mouths wide in cold air, which made their
speech abound in consonants. From a contrary cause, the inhabitants
of warm climates formed a softer language, and one abounding in
vowels. The Greeks, inhaling air of a happy medium, were celebrated
for speaking with the wide-open mouth and a sweet-toned, sonorous
elocution.

12. Man may Make his own Climate. — So controlling is this agent,
and yet man comes into the world defenceless from its invasions;
provided with no natural means of protection from its disturbing and
destructive influence. But in the exercise of that intelligence which
gives him command over nature, he has studied the laws, properties,
and effects of he.it, and the methods by which it may be produced

rr INFLUENCIS THE DIMENSIONS OF BODIES. 23

and regulated. He has devised the means of creating an artificial and
portable climate, and thus of releasing himself, in a great measure,
from the vicissitudes of temperature. We are to regard the production
and control of artificial climate, as an art involving the development
and expansion of mind and body, the preservation of health and the
prolongation of life. Such has been the thought expended upon this
subject, and so important the results to the well-being of man, that we
may almost venture to measure the civilization of a people, by the per-
fection of its plans and contrivances for the management of heat.

m.— MEASUKEMEIST OF HEAT. THE THEEMOMETEB.

13. Heat tends to Equal Siffasion. — "We have said that heat is a force,
or energy, existing everywhere throughout nature. Every kind of
matter which we know contaios heat, but all objects do not contain
equal quantities of it. If left to foUow its own law, heat would dis-
tribute itself through all the matter around, untU each body received
a certain share ; and it would then be in a condition of general rest, or
equal balance, (equilibrium.) It is to this state that heat constantly
tends. If a very hot body of any kind is brought into a room, we all
know it will at once begin to lose its heat, and that the temperature
continues to descend until it is the same as the surrounding air, walls,
and forniture.

14. How do we get acquainted with Heat?— But before heat can
tend to equilibrium, it must first be thrown out of this state. There
are forces which tend to disturb the equal lalance of heat, causing it
to leave some bodies, and accumulate in others in unusual or excessive
quantities. It is the passing of heat from body to body, from place to
place, — ^robbiug one substance of it and storing it up in another ; in
short, its motimi, and the effects it produces, which enable ns to
become acquainted with it. How, then, may we know when one. sub-
stance has been deprived of heat and another has received it ? or how
can we ascertain the quantity of it which a body possesses?

15. Heat aeemnnlating in Bodies, cnlai^es them.— -It is an effect of
heat, that when it enters into bodies it makes them larger ; it increases
their bulk, or expands them, so that they occupy more space than they
did before, A measure that will hold exactly a gallon in winter, will
be expanded by the heat of summer so as to hold more than a gallon.
The heat of summer lengthens the foot-rule and yard-stick. A pen-
dulum is longer in summer than in winter, and therefore swings or
vibrates slower, which causes the clock to lose time. Twenty-three

24 MEASUEEMENT OP HBAT,

pints of water, taken at the freezing point, wonld expand into twenty-
fonr by being heated to boiUng. The difference in the heat of the
seasons affects sensibly the bulk of liquors. In the height of summer,
Fig. 1. spirits will measure five per cent, more than in the

depth of winter. (Geaham.) "When 180 degrees of
"* ' heat are added to iron, 1000 cubic inches become

1045 ; 1000 cubic inches of air become 1365. Some
substances, however, in solidifying expand. This is
the case with water, which attains its greatest
density, or shrinks into its smallest space, at the
temperature of 38"8°, as seen in fig. 1. Prom this
point, either upward or downward, it enlarges ; and
greatest at freezing, or 32°, the expansion amounts to about
ensi y. j^^^ ^^ .^^^ bulk, Ico therefore floats upon the surface
of water. The wisdom of this exception is seen,
when we reflect, that if it sank as fast as it is formed,
whole bodies of water would be changed to solid ice.

16. Relation betweeu Heat and Expansion. — In the same manner, all
the objects about us are changed in their dimensions as heat enters or
leaves them. Different substances expand differently by the same
quantities of heat ; but when a certain measured amount is added to, or
taken from the same kind of substance, it always swells or shrinks to
exactly the same extent. The variation of size produced in solid sub-
stances, such as wood, stone, or iron, is very small ; we should not be
aware of it without careful measurement. The same proportion of
heat causes liquids, such as water, alcohol, and mercury, to vary in
bulk more than solids ; while heat added to gases, or airs, produces a
much greater expansion than it does in liquids. Although heat thus
causes bodies to occupy more space and become larger, yet it does not
make them heavier. The same substance weighs exactly the same, no
matter how cold or how hot it is ; hence heat is called imponderable.

17. Principle and Constrnction of the Thermometer. — ^If, then, when
a substance receives a certain quantity of heat, it undergoes a certain
amount of enlargement, we can use that enlargement as a measure of
the heat ; and this is what is done by the thermometer or heat-meas-
urer. A common thermometer is a small glass tube, with a firfo
aperture or hole through it, like that in a pipe stem, and a hollow
bulb on one end of it fig. 2. This bulb and part of the tube is fiUed
with the liquid metal mercury. By suitable means, the air is removed
from the empty part of the tube, and its open end sealed up. The
bulb is then dipped into water containing ico, and a mark is made

SCALES OP THEEMOlftETEES.

25

Fahrenheit's
Scale.

2120

1220

Centigrade
Scale.

lOOO

Zero.

upon the tube at the top of the mercurial column. This point of
melting ice is the same as that at which water freezes, and is hence
called the freezing point. The tube is then Fia. 2.

removed, and dipped into boding water.
The heat passes from the water, through
the glass, into the mercury, which rapidly
expands and rises through the narrow
bore. It passes up a considerable distance,
and then stops ; that amount of heat will
expand it no more. The height of the
mercury is again marked upon the tube,
and this is called the ioiling point of water.
The distance upon the tube between these
two points is then marked off into 180
spaces, which are called degrees, and
marked (°). Now, it is clear that the
amount of heat which runs the mercury
up tlirough these 180 spaces is precisely
the same quantity that changed the water
from the freezing to the boding point ; so
that we may say that the water in this
case received 180 degrees of heat. If we
mis a pound of water at the bodiug point with another pound at the
freezing point, the result wiU be a medium ; and if the thermometer
is plunged into it, the mercury wiU stand at the ninetieth space — that
is, it contatas 90 degrees of heat according to this scale of meas-
urement. And so, by dipping the thermometer into any vessel of
water, we ascertain how much heat it contains.

18. How Tbermometers are Graduated or Marked.— But this is not
the way that the scale of the common thermometer is actually marked.
Its inventor, Faheenheit, instead of beginning to count his degree3
upward from the freezing point, thought it would be better to begin
,to count from a point of the extremest cold. Accordingly, he mixed
salt and snow (55) together, and putting his thermometer in it, the
mercury feU quite a distance lower than the freezing point of water.
This he supposed to be the greatest cold it is possible to get, though
an intensity of cold has since been obtained 150° lower. Marking
off this new distance through which the mercury had fallen, in the
same way as above, he got 32 additional spaces or degrees. Calling
this point of least heat or greatest cold he could get, nought or zero,
he counted up to the fi-eezing point of water, which was 32°, and
2

Zero,

Thermometer.

26 MEASUEEMENT OF HEAT.

adding tWs to the 180 above, he got 213 as the boiling point of water.
This is the way we find the common thermometer scale marked (Fig.
2) upon brass plates, to which the glass tube is attached. The centi-
grade thermometer calls the point of melting ice zero^ and marks the
space up to boiling water into 100 degrees. In Eeaumur's thermometer,
the same space is divided into 80 degrees. Degrees below zero are
marked with the minus sign, thus — . It deserves to be remarked,
that the glass tube expands by heat as well as the mercury, but by no
means to so great a degree. And besides, there being a considerable
quantity of mercury in the bulb, it requires but a very small expansion
of it to push the quicksilver up the narrow tube, through a perceptible
space.

19. Exactly what the Thermometer indicates. — The word thermometer
is derived from thermo, heat, and metron, measure, and it therefore
signifies heat-measurer. But what does it measure ? That which is
measured we usually name quantity. But we must not suppose that
the thermometer indicates quantities of heat in any absolute sense.
For example, if we dip a giU of water from a spring in one vessel,
and a gallon in another vessel, a thermometer will indicate exactly
the same degree of heat in one as in the other ; but we cannot thence
infer that the absolute quantity of heat is as great in the gUl of water
as in the gallon. The thermometer shows us simply the degree of in-
tensity of the heat in its mercury ; and as this constantly tends to the
same point as that of surrounding bodies, we take its degree to be
their degree. If the thermometer suspended in a room stands at 70°,
we say the room is at 70°, because heat tends to equalization.
If by opening windows or doors the thermometer falls to 60°, we say
the room has lost 10° of heat, — speaking of it as a measured quantity.
The instrument indicates variable degrees of intensity, which are con-
verted into expressions of quantity. We shall shortly see that there
are certain conditions of heat which the thermometer totally fails to
recognize.

20. Importance of the Domestic use of the Thermometer. — As the ques-
tion of temperature is one of daily and hourly interest, not only of
the utmost importance in conducting numerous household operations,
but of the highest moment in relation to the maintenance of health,
it will at once be seen that a thermometer is indispensable. Every
family should have one, and accustom themselves to rely upon it as a
practical guide in relation to heat, and not to depend upon feeling or
guessing. Thermometers costing from fifty cents to a dollar and a half,
will answer all ordinary purposes. They are so mounted that the scale

THEEMOMETEES AM) THKEB INDICATIONS. 27

and tube may be drawn out of the frame, so that the bulb can be im-
mersed in a liquid, if required. They must be gradually warmed before
dipping in hot liquids to prevent fracture of the glass, and of course
need to be handled with much care. Their scales extend no higher
than the boiling point of water. There is usually some departure from
the accurate standard in the indications of the cheaper class of instru-
ments. Mr. Tagliabtje, a prominent maker of this city, states that these
variations rarely exceed from 1 to 2 degrees.

21. Interesting Facts of Temperature. — "We group together a few
points of temperature of familiar interest.*

Best temperature for a room 65°-68°

Lowest temperature of human body (in Asiatic cliolera) 67°

Mean temperature at the equator 81°

Heat of the blood 98°

Beefs tallow melts 100°

Mutton tallow melts 106°

Highest temperature of human body (in tetanus or lockjaw) .... 110°

Stearine melts 111°

Spermaceti melts 112°

Temperature of hot bath 110°-180°

Phosphorus inflames, Friction matches ignite 120°

Tea and coffee usually drank , . ISO'-liO'

Butter melts 130°-140°

Coagulation of albumen , 145°

Scalding heat . . , • , . . 150°

Wax melts 155°

Milk boils • . . . . 199°

Sulphur melts 226°

Cane sugar melts 320°

Baking temperature of the oven 320°^00°

Sulphur ignites 560°

Heat of the common flre 1000°

lY. EADIATION OP HEAT AND ITS EFFECTS.

22. Heat passing through Bodies.— Heat in motion around us is coil-^-
stantly passing through some substance, or from one material body to
another. But all substances do not behave alike toward it. They do
not aU receive, retain, or part with it in the same way. Through cer-
tain bodies it passes rapidly in straight lines, like rays of light, and is
then termed radiant heat, and this kind of heat-motion is called radi-
ation, and the substances which allow it to pass through them are said
to trammit it. We receive radiant heat from the sun and from arti-
ficial fires ; and the air is one of those substances which permit it to
pass through.

* For a further list of temperatures, see Appendix A.

28

RAT>IATIOK A]ST) ITS EFFECTTS.

23. Decrease in the Force of Heat-rays. — When heat radiates from
any source, as the sun, a stove, an open fire, or flame, it passes from
each point in all directions Fig. 3 ; it spreads out or diverges as it

Fig. 3.

V

N

Kadiation of heat.

Fig. 4

passes away so as to hecome weaker and much
less intense. It decreases in power at a regular
numerical rate, as seen in Fig. 4. It is commonly
said that the intensity of radiant heat decreases
inversely as the square of the distance ; that is,
if in standing before the fire at a distance of two
feet from it, we receive a certain amount of
heat, and then we step hack to twice that dis-
tance, we shall receive but one fourth the quan-
tity ; at thrice the distance, but one ninth ; and
at four times the distance, but one sixteenth the
quantity, as is shown in Fig. 4. But this state-
ment is only true when we consider the heat as passing from a single
point. When it flows from an infinite number of adjacent points, — that

is, a surface, which is the way
it is practically emitted, it does
not decrease at so rapid a rate.
24. Different kinds of Heat.—
We all know that some substan-
ces will let light pass through
them, and others will stop it.
It is just so with heat : but the
same substances which transmit
light, do not always transmit
heat. Air allows both to pass

Showin;; the rate at which radiant heat is without obstruction ; but water,
diffused and weakened. ^^.^^^ ^^ ^^.^^^^ ^^^^^^ ^^^ ^^^_

sage of light, has very little power to transmit heat. Eays of light,
passing through water, are strakied of nearly all their heat. But
there seems to be a difference in the source and nature of the heat
itself, as to its power of getting through various bodies. Glass allows
solar heat to go through it, but not artificial heat. A pane of glass
held between the sun and one's face will not protect it from the
heat ; but it may be used as a fire-screen. If we place a plate of
glass and of rock-salt before a hot stove, the dark heat -will pass
freely through the salt, but not through the glass. The glass is,
therefore, opaque to heat (if we may borrow the language of light),
while salt is tramparent to it, and is hence called the glms of heat.

CIBCUMSTANCES CONTKOLLINa IT. 29

Meloni has shown that if the quantity of dark, radiant heat transmit-
ted through air, be expressed by 100, the quantity transmitted through
an equal thickness of a plate of rock-salt will be 92 ; flint glass, 67 ;
crown glass, 49 ; alum, 12 ; water, 11.

25. Heat which does not go throngh is Absorhed. — ^When a substance
does not permit all the rays of heat which strike upon it, to pass
through, those which are detained, or lodged within it, are said to be
absorhed by it. Thus, fine window-glass transmits only 49 heat rays in
a hundred, the remaining 51 being absor'bed by it. Now it is clear,
that if all the heat pass through a substance, none can accumulate in
it to warm or heat it. It is the heat detained or lodged in a body that
warms it. The heating power is proportional to absorption. The
atmosphere lets the sun's heat all pass — does not absorb it ; it is there-
fore not warmed by it.

26. Conditioas of Radiation. — The power of a body to emit or radiate
heat, depends first, upon the quantity which it contains. Other things
being the same, the higher its temperature compared with the sur-
rounding medium, the more rapidly will it throw off its heat. As it
cools, the radiation becomes slower and slower. But aU subtances at
the same temperature, do not throw out their heat alike. The condi-
tion of surfaces exerts a powerful control over radiation. Eough,
uneven surfaces radiate freely, while smooth, polished surfaces offer a
barrier to heat, which greatly hinders its escape. Metals, as their sur-
faces are capable of the highest polish, are the worst radiators. Ac-
cording to Meloni, smfaces smoked or covered with lampblack, radi-
ate most heat. If the power of radiation of such a surface be repre-
sented by 100, that of glass wiU be 90 (it is therefore an excellent
radiator), polished cast-iron, 25 ; polished wrought iron, 23 ; polished
tin, 14 ; brass, 7 ; silver, 3. By tarnishing, or rusting metallic surfaces,
their radiating power is increased. Leslie has shown that, compared
with a smoke-blacked surface, as 100, clean bright lead is 19, whUe if
tarnished, it is 45. If the actual radiating surface is metallic, it matters
little what substance is under it. Glass covered with gold-leaf, is re-
duced in its radiating power to the condition of a polished metal. K the
bright, planished, metallic sm'face is in any way dulled or roughened,
as by scratching or rusting, its power of throwing off heat is greatly
increased. Indeed, if the polished surface is only covered, the same
effect is produced. Etjmfoed took two similar brass cylinders, cov-
ered one Avith a tight investment of linen, and left the other naked ;
he then fiUed each with hot water, and found that the same amount of

-Hi

Sa RADIATION AND ITS EFrECTa

heat which was thrown off by the covered cylinder in 36^ minutes,
required 55 minutes to radiate from the naked cylinder.

27. How Polishing affects Surfaces. — Dr. Laednee says "the diminu-
tion of radiating power, -vyhich ordinarily accompanies increased polish
of surface, is not a consequence of the polish in itself, hut of the in-
creased density of the outer surface^ produced by the act of polishing;
and the effect of roughening is to he ascribed to the removal of the
outer and denser coating."

28. Best Mode of Confining and Retaining Heat. — ^These principles show
us how best to enclose and retain heat when we wish to prevent waste
from radiation. Glass, porcelain, and stone ware surfaces, radiate
freely : vessels of these materials are not the best to preserve foods
and fluids hot at table. They should either be of polished metal, or
have bright metallic covers, which will confine the heat. Bright tea-
urns and coffee-pots are best to retain their contents hot ; and a tea-
kettle keeps hot water much more effectually if clean and bright, than
if covered with soot, though it is much harder to boil. Pipes intended
to convey heat should be bright and smooth, while those designed to
radiate or expend it, should be rough. For the same reason, polished
stoves and stove-pipes are less useful in warming rooms than those
with rougher surfaces.

29. Color of Surfaces does not influence Radiation. — It is very generally
supposed that the color of a substance influences the escape of heat
from it. But the experiments of Dr. Bache have shown that this is
a popular fallacy. He has proved that color exerts no control on the
radiation of non-luminous heat, or such as is unaccompanied with light.
A body will emit heat from a white or black surface with equal
facility.

30. Heat thrown off from Bodies. — Eadiant heat striking upon bodies,
if it is not permitted to pass instantly through them in straight lines,
is either absorbed or reflected. If reflected, it is instantaneously thrown
back from the surface of the body, and therefore does not enter to
warm it. If absorbed, it is gradually taken into the substance, and
raises its temperature. A bright metallic surface wiU reflect the heat
rays and itself remain quite cold. As heat cannot get out through a
bright surface, so it cannot get in through it. AU the heat that is
thrown upon such a body, is either reflected or absorbed ; that which is
not disposed of one way goes the other. If half of it is absorbed, the
other half will be reflected. Glass absorbs 90 per cent, and reflects 10,
while polished silver reflects 97 per cent, and absorbs but 3. A good
absorbing surface is a bad reflecting surface, and a good reflector is a

THEORY OF HEAT-EXCHANGES. 31

bad absorber. So a good radiating surface absorbs -well and reflects
badly, wbile a bad radiating sni-face absorbs badly but reflects well.
The density, or polish of a surface controls the admission as -well as
the escape of radiant heat. Two kinds of heat may thus pass in straight
lines from a body — radiant heat and reflected heat. The former comes
from within, and therefore cools it ; the latter strikes against it, and
rebounds without either warming or cooling it.

31. Color of Snrfaee inflaenees the admission of Heati — We have seen
(29) that color has no influence over radiating surfaces ; but the power
which bodies possess of alsorhing heat, depends very much upon color.
Feanklik spread differently colored pieces of cloth upon snow in the
sunshine. That of the black color sunk farthest below the surface ;
which showed that it melted the most snow, and consequently received
most heat. The blue piece sunk to a less depth, the brown stiU less,
and the white hardly at aU, which showed that it absorbed least heat.
Hence, by scattering soot over snow, its melting may be hastened : it
wiU absorb more of the solar heat. A dark-colored soil warms easier
in spring, is earlier, and has a higher temperature during summer, than
one in other respects similar but of a lighter color. Darkening a soil
in color, therefore, is equivalent to removing it farther south. Grapes,
and other fruits, placed against a dark wall, wiU mature or ripen
earlier than if against light-colored walls, because, for the same reason,
they are warmer. So, also, in the matter of clothing, white throws
off the solar heat, while black absorbs it.

32. Exchanges of Heat— it escapes from aO Snhstances. — It has been
stated that, down to 200° below the freezing point of water, substances
contain heat and may part with it : and as we know of no means by
-which heat can be absolutely enclosed or confined within bodies, all
are regarded as not only possessing the power of radiation, but as actu-
ally exercising it. Eays of heat pass away in every direction, from all
points of the surfaces of all bodies. "When several objects of various
temperatures, some cold and some hot, are placed near each other,
their temperatures gradually approach the same degree, and after a
time they will be found to have reached it. Now all these bodies are
supposed to be constantly radiating heat to each other, and hence con-
stantly exchanging it. If we place a cannon-ball at a temperature of
1000° or a red heat, beside another at 100°, it will part with its heat
rapidly to the latter, as illustrated by the radiant lines in Fig. 5. But
the ball at 100° also radiates its heat, although more slowly, and thus
returns a portion to the hotter ball ; so that there is an exchange estab-
lished. But if a baU of ice at 82° be placed beside the cannon-baU at

32 RADIATION Airo ITS EETECIS.

100°, the same thing takes place, only in a less iatense degree; and if
Fig. 5. an ice-ball from the

Arctic region at 100"
below the freezing
point, were placed be-
side another at 32°, ex-
actly the same thing
would occur. Thns all
bodies are constantly

Exchanges of heat ; it radiates from hodies at all temper- interchanging heat and

tending to equahzation.

S3. Starlight Jfiglits colder than cloudy Ones. — The various objects
upon the earth's surface, are not only continually radiating their heat
to each other, but also upward through the au* into space. If there
be clouds above, they throw it back again to the earth's surface ; but
if the sky is cloudless, the heat streams away into space, and there is
none returned. At night, therefore, when there is no heat coming
down from the sun, and no clouds to prevent its escape from the earth,
the temperature of the earth's surface and the objects thereon, falls.
Those which radiate best, cool fastest, and siuk to the lowest tempera-
ture. Clear, starlight nights are thus colder than cloudy nights ; and
although more pleasant and inviting for evening walks, require that
more clothing should be worn.

34. How Dew is Prodnced. — The cause of dew was not imderstood
untU lately. Many were persuaded that it came out of the earth;
while others thought it fell as a fine rain from the elevated regions of
the atmosphere. The alchemists regarded it as an esudation from the
stars. They believed dew-water contained celestial principles, and
tried to obtain gold from it. The problem was solved about forty
years ago, by Dr. Wells, who first considered it in connection with
the radiation of heat. The air contains moisture in the state of invis-
ible vapor ; if its temperature be high, it will hold more moisture, if
low,less (286). When, therefore, the air is sufliciently cooled, its moisture
is condensed, and appears as drops of water. These are often seen in
summer days upon the outside of the pitcher of cold water ; improp
erly called the sweating of the pitcher. The moisture that is seen
trickling down the window-pane in winter, is condensed from the
vapor of the air in the room, by the outward escape of heat from the
glass, and the consequent cooling of the air in contact with it inside.
When, therefore, by nightly radiation, any objects upon the earth's
surface have become so cold as to cool the aii' in contact with them,

rr EXPLAINS THE CAUSE OF DEW. 3S

sufficiently to condense its moisture, dew is formed, and the degree of
temperature at which this effect takes place, is known as the dew-point.
85. Conditions of the Deposit of Dew. — Every calm and clear night
the surface of the ground cools by radiation from lO'^ to 20°. But
this surface is composed of various objects, which radiate unequally.
Some part with their heat so rapidly as to cool the air down to the
point of condensation, and dew is deposited upon them. Others ra-
diate so slowly that their temperatures do not sink to the dew point,
and no dew is formed upon them. Good radiators become covered
with dew, while bad radiators remain dry. Grass, for example, is an
excellent radiator, and it receives dew copiously, while under the same
circumstances, stones, being bad radiators, are not moistened. Dew
is deposited from a stratum of air only a few inches thick, which is
condensed by contact with the cold body. If, however, that stratum
of air is moved away before it gets sufficiently cooled, no 'dew will be
formed. Hence, when the air is in motion, as on windy nights, there
is no dew. Fall of temperature always precedes the formation of dew,
and the greater the fall, the heavier the dews ; the quantity of moist-
ure in the atmosphere, m both cases being the same. Farmers very
well know that nights with heavy dews are very cold ; but the cold
is the cause^ not the effect^ of the dew. The moister the air is, with
the same descent of temperature, the more dew falls. Thus, arid
deserts are dewless, notwithstanding the intense nightly radiation.

36. Exchanges of Heat may prevent Dewt — ^We have noticed Peevost's
theory of the exchanges of heat, by which, all bodies are assumed to
radiate heat to each other constantly (32). This explains why little
or no dew is found under trees. "While the grass radiates upward, the
foliage radiates downward, and thus checks cooling. For this reason,
no dew is precipitated on cloudy nights. As objects radiate upward,
the clouds radiate back again, and prevent the falling of the tempera-
ture. More dew falls upon the summits of mountains, where objects
are most open to the sky, than in valleys, where the angle of radiation
or access to the open heavens is much less. Objects protected in an_,
way from exposure to the sky, are, to that extent, guarded from dew.

37. Frost Caused in the same way as Dew. — As a certain amount of
cooling, deposits moisture from the air, more still, freezes it ; and
hence, frost or frozen dew. This extreme cooling is often hurtful to
vegetation, and during the serene nights of spring, tender plants are
often killed, as is frequently the case with immature fruits aud grain
of autumn. Here, again, all circumstances which oppose radiation,
prevent the cooling. "Vegetables, sheltered by trees, suffer less than

34 CONDUCTION OP HEAT.

those not so protected. A thin covering of cloth or straw, preserves
plants, as may also fires that fill the air with smoke.

V. CONDUCTION OF HEAT AND ITS EFFECTS.

38. Heat creeps slowly tlirongh some Bodies. — If we place one end of
a bar of metal in a fire, that end becomes hotter than the other parts
of the bar. But this effect is only temporary ; the heat will gradually
;)ass through it, being communicated from particle to particle, until

Fig. 6. the other extremity becomes

heated. This is easily shown
by taking several marbles, and
sticking them to an iron or
copper wire with wax Tig.
6. If now heat is applied
to one end of the wire, it

The balls drop successively as the heat moves in, i i ,-,

along the rod. gradually travels along, the

wax is melted, and the marbles drop off successively. The heat in
this case is conducted by the metal.

39. Different Substances conduct at different Rates. — Heat diffuses in
this manner, at very unequal speed through different substances. If
we hold one end of a nail in a candle flame, it soon gets so hot as to
burn the fingers ; while we can fuse the end of a glass rod in a lamp,
although holding it within an inch of the melting extremity. Iron
thus conducts heat much better than glass. Those substances through
which heat is diffused most rapidly, are called good conductors, while
those through which it passes slowly, are iad conductors. In general,
the denser a body is, — that is, the closer are its particles, — the better
does it conduct heat ; while the more porous, soft, loose and spongy
it is, the lower is its conducting power. The metals, therefore, are the
best conductors, while bodies of a fibrous nature, such as hair, wool,
feathers, and down, are the worst conductors of heat.

40. Enmford's Scale of Conductors. — Rumfoed arranged bodies in
the following order, their conducting power progressively diminishing
as the list proceeds. Gold, silver, copper, iron, zinc, tin, lead, glass,
marble, porcelain, clay, woods, fat or oil, snow, air, silk, wood-ashes,
charcoal, lint, cotton, lampblack, wool, raw silk, fur.

41. Conducting Power of Building materials. — Bad conductors, — non-
conductors, as they are called, — afford the best barriers to heat, and
they are employed when it is desired to confine it. In winter, nature
protects the earth and crops from excessive cold, by a layer of non-

EFFECrrS OP NON-CONDUCmm SUBSTAITCES. 35

conducting snow. The birds, she prc)tects by feathery and downy plu-
mage ; quadrupeds, by hair, wool, fur ; — and even the trees, by porous,
non-conducting ^bark. In the management of heat, man finds the
variation in the conducting powers of bodies, of the highest import-
ance. In building houses, the worst conductors are the best materials
for the walls. WhUe they promote warmth in winter, by retaining
the heat generated by fires within, they are favorable to coolness in
suromer, by excluding the external heat. HuTCHrisrsoN examined
some building materials, and ascertained their conducting powers
to be as follows, omitting fractions. (Slate being taken as 100.)
Marble 75 to 58, fire brick 62, stock brick 60, oak wood 34,
lath and plaster 25, plaster of Paris 20, plaster and sand 18. The
hard woods conduct better than soft, and green woods better than
dry. Dry straw, leaves, &c., are good non-conductors, and are used
to cover tender plants in winter, but if wetted, they convey heat
much better.

42. Non-condaeting properties of Air. — Air is one of the most perfect
non-conductors; Etjmfoed thinks it is the best of all. The conduct-
ing power of air, however, is greatly increased by moisture. If we
represent the power of common dry air to conduct heat, by 80, its
power, when loaded with moisture, rises to 230, — it is nearly trebled.
For this reason, damp air feels colder to the body — ^it conducts away its
heat faster. Those substances which enclose and contain air, as pow-
dered charcoal, tan-bark, sawdust, chafi', &e., are good non-conductors
of heat. Sawdust is an excellent bar to heat ; it should not be too
much pressed together, as then, the particles, being in too close con-
tact, conduct better : — nor too loose, as the air circulates through it,
and thus conveys the heat. A layer of air between double windows,
checks the escape of heat, but we do not, in such a case, avail our-
selves of its perfect non-conducting power, otherwise we might use
it to enclose ice-houses, &c. It is easily set in motion (97), and thus
becomes a ready transporter of heat. Loose, porous bodies are filled
with it, and they act as non-conductors by preventing its motion,

43. Non-conducting Properties of Clotliing. — Winter apparel is made
of non-conducting woollen fabrics, which prevent the escape of heat
from the body. Cotton carries ofi" the heat faster than wool ; and
linen still faster than cotton. Linen is pleasantest in summer to re-
lieve the body of heat, but it cannot defend the system like flannel
against the sudden changes of temperature in an inconstant climate.
In local inflammation of the body, linen is the best for dressings and
applications, as it is a better conductor, and therefore cooler than cot-

36 CONVEYANCE OF HEAT.

ton.* The tigh, non-conducting power of the -woollens, is shown
hy the common practice of preserving ice in hot weather, by simply
wrapping it in flannel.

44. Oar Sensations of Heat depend upon Conduction. — The sense of
touch is an unreliable guide to the degree of heat, because substances
are so diverse in conducting power. The badly conducting carpet
feels warmer to the naked feet than the better conducting oilcloth,
because the latter will carry away the heat faster from the skin, al-
though both are at exactly the same temperature. This influence of
conduction over sensation, as also the remarkable difference of con-
ducting power among solids, liquids, and gases, may be shown in a
forcible manner. If the hand be placed upon metal at 120° it will be
burned, owing to the rapidity with which the heat enters the flesh.
"Water will not scald, provided the hand be kept in it without motion,
till it reaches the temperature of 150° ; while the contact of dir at
250° or 300° may be endured. Sir Joseph Banks went into a room,
heated to 260°, and remained there a considerable time without incon-
venience. The particles of air are so far asunder, that the heat crosses
their inter-spaces with difficulty ; and as but few of them can come
in contact with the body at once, the amount of heat that they can
impart is comparatively small.

VI. HEAT CONVEYED BY MOVINQ MATTER.

45. It is carried by Particles in Motion. — The freedom with which the
particles of liquids and gases move among each other, is another source
of the motion of heat. Water conducts heat but very imperfectly.
If a glass tube filled with water, be inclined over a lamp, so that the

^10- '''■ flame is applied at the upper end Fig. 7, the

water will boil at the top of the column, but
below the point where the flame is applied,
the temperature of the water will be but lit-
tle elevated in a long time. The conduction
of heat is not influenced by the position of the
body along which it passes. It moves through
a conductor as swiftly downward as upward,
or horizontally. Had the heat, in this case,

The water doea not conduct ■^. iii , ni

the heat downwards. been conducted^ it would have travelieQ as
readily down the water column as upward. Yet all understand that

* Linen is also best for dressing local inflammations, because its fibres are round and
smooth, and therefore, less irritating. The fibres of cotton are flat and angular, and of
woollen, rough and jagged, and consequently, uufit for this purposo (795).

ITS TEANSPOETATION BY WATEB.

37

a large amount of water may be heated by a small fire, if the beat
be applied at the bottom. The cause of this is, that the lower layer
of water in the vessel, being warmed, expands, becomes lighter, and
for the same reason that a cork would rise, ascends through the mass
of liquid above. Its place is taken by the colder liquid, which in
turn warms, expands and ascends ; and thus currents are formed, by
which the heat is conveyed upward, and diffused through the mass.
This mode of heat movement is hence called convection of heat.

46. How the Water-currents may be shown. — The circulation thus pro-
duced by ascending and descending currents, may be beautifully seen
by nearly filling a pretty large glass fiask with water, and dropping
into it a few small pieces of soHd litmus {a cheap^ Hue coloring sub-
stance), which sink through the liquid. On applying heat to the bot-
tom of the vessel by a small lamp, a central current of water, made
visible by the blue tint it has acquired from the litmus, is seen rising
to the surface of the liquid, when it bends ^ „

over m every direction like the branches of
the palm tree, and forms a number of descending
currents, which travel downward near the
sides of the vessel Fig. 8. Two causes
operate here to distribute the heat. The
warm liquid constantly conveys it away, and
at the same time, the colder particles are con-
tinually brought back to the source of heat,
at the bottom. Exactly the same thing takes
place when ak is heated ; it expands, becomes
lighter, rises in currents, and carries with it
the heat. "We shall refer to this principle
again, when speaking of the contrivances for __,

warming rooms. Currents produced in water

' by boiling.

VII. YAEIOUS PROPEETIES AND EFFECTS OF HEAT.
47. Heat added to SoUds, liquefies them.— Not only is the size of
bodies influenced by heat, but also their state, ovform. A§ heat enters
a solid body, its particles are forced asunder, until at length they lose
their cohesive hold of each other, and faU down into the liquid state.
The particles have become loosened and detached, and glide freely
among each other in all directions. Carbon and pure alumina are
the only substances that have not been Uquefied by any amount of
heat yet applied. Some solids, at a given point of temperature, enter

«8 VAEIOUS EFFECTS OF HEAT.

suddenly into the liquid state, and others pass gradually through an
intermediate stage of pastiness or softening.

48. Melting Points. — That degree of temperature which is required
to melt a substance, is called its melting or fusing point. The com-
mon temperature of the air is sufficient to melt some substances.
From this point all along up to the highest heat, at which carbon re-
fuses to liquefy, various substances melt at diiferent temperatures,
showing that each requires its particular dose of heat to throw it into
the liquid state. Thus, mercury is a liquid at common temperatures,
and is the only metal that exhibits this peculiarity. Phosphorus melts
at 108°, wax 142°, sulphm- 226°, sugar cane 320°, tin 442°, lead 612'',
zinc 773°, silver 1873°, gold 2016°, iron 2800°, Liquidity seems thus
to be produced by the combination of solids with heat. Take the
heat from a liquid and it sohdifies. Take away the heat from water
until it falls to 32°, and it becomes solid water, or ice. If kept per-
fectly stiU, it may be lowered below 32° before the atoms lock to-
gether into the crystalline or congealed state ; but if the water is
jarred or agitated, crystalline ice results at that temperature. Heat
taken from mercury until it falls to 39° below zero, causes it to harden
into a solid, ringing rnQisil— freezes it. - 180° of heat taken from alco-
hol, do not freeze, but make it thick and oily. As heat combined
with solids produces liquids, so heat combined with liquids produces
vapors or gases. Heat added to ice generates water — added to Avater
generates steam. The heat which converts solids into liquids, is called
caloric of fluidity, and as gases are known as elastic fluids, the heat
which changes liquids to gases is called calorie of elasticity.

49. What is meant by Specific Heat. — If we take equal weights of
different substances, and expose them to the same sources of heat,
they do not aU receive it with equal readiness ; in the same length
of time some will be much more warmed than others. If a lamp
flame of a given size wUl raise the temperature of a pound of spirits
of turpentine 50° in ten minutes, it wUl take two flames of the same
size to raise a pound of water through the same temperature in the
same time, or it will take the same flame twenty minutes, or twice as
long. It is clear that the water in this case, in being raised through
the same temperature, has received twice as much heat as the spirits
of turpentine. If a flame of a certain size wUl heat a pound of mercury
through a certain number of degrees in a certain time, it wUl take 30
flames of the same heating power, to raise a pound of water through
the same range of temperature in the same period ; to raise it through
the same number of degrees, therefore, water requires thirty times

WATER HOLDS LABGE QUANTITIES OF IT. 39

the heat that mercury does. This would seem to show that different
bodies have different capabilities of holding or containing heat, or, as
it is usually said, they have different capacities for heat : and, as each
substance seems to take a peculiar or particular quantity for itself,
that quantity is said to be its ' specific ' heat. The specific heat of
water is greater than that of any other substance. In ascending from
a given lower to a higher point, it takes into itself or swallows up
more heat than any other body ; and in cooling down through that
temperature, as it contains more to impart, so it gives out more heat
than any other body. If the specific heat of water is represented by
1000, that of an equal weight of charcoal is 241, sulphur 203, glass
198, iron 113.79, zinc 95.55, copper 95.15, mercury 33.32.

50. Why Water was made to hold a large amount of Heat. — ^When we
consider the extent to which water is distributed upon the earth, we
see the wisdom of the arrangement by which it is made to hold a
large amount of heat, and the necessity that it should slowly receive,
and tardUy surrender what it possesses. Suppose that the water of
oceans, lakes, rivers, and that large proportion of it contained in our
own bodies, responded to changes of temperature, lost and acquired
its heat as promptly as mercury : the thermal variations would be
inconceivably more rapid than now, the slightest changes of weather
would send their fatal undulations through aU living systems, and the
inconstant seas would freeze and thaw with the greatest facility. But
now the large amount of heat accumulated in bodies of water during
summer is given out at a slow and measured rate, the climate is
moderated, and the transitions from heat to cold are gradual and
regulated.

51. Why Water is so cooling when drank. — It is because water is
capable of receiving so much heat, that it is better adapted than any
other substance to quench thirst. A small quantity of it will go
much further in absorbing the feverish heat of the mouth, and throat,
than an equal amount of any other liquid. When swallowed and
taken into the stomach, or when poured over the inflamed skin, it is
the most grateful and cooling of all substances. For the same reason,
a bottle of hot water will keep the feet warm much longer than a hot
stone or block.

52. Concealed or latent Heat. — All changes in the densities of bodies
by which their particles are forced into closer union, or to greater
distances apart, are invariably accompanied by changes of heat..
Caloric is supposed to be contained in bodies, something as water is
held in a sponge — ^lodged in its cavities or pores. If a wet sponge is

40 VAEIOUS EFFECTS OF HEAT.

compressed, water is squeezed out ; but, when it expands again, it
will again imbibe tbe liquid. In like manner material substances,
when condensed into less space, give out heat, and, when dilated,
they take it in or absorb it. If a piece of cold iron is smartly ham-
mered upon an anvil, its particles are forced closer together, and its
heat is driven out of its concealment, the iron becomes hot. By
suddenly condensing the air as in the instrument called the fire-syringe,
Pj^ g , in which a close fitting piston is driven down a tube (Fig.
r- — -1 9), the condensed air gives out so much heat as to set fire
to tinder. Now, before condensing the iron, or the air, in
these cases, they appeared cold, the thermometer de-
tected in them no heat; yet they contained heat, and
condensation brought it out. As we cannot find it by
n] the ordinary test, we infer that it was concealed or latent
in the iron and air. Heat is capable, therefore, of be-
coming lost or hidden in bodies, and then of again
re-appearing under proper circumstances. "We call this
latent heat, because we must call it something, and the
term is convenient ; but we are probably very far from a

[r-^

t

a

Air condenser. . -, ,. i- j.t_ ^ j. • j.i

true explanation oi the tacts m the case.

53. now much Concealed Heat Water holds. — Whenever a solid ia
changed to a liquid, a certain amount of heat disappears — goes into
the latent state. If we take a lump of ice at zero, fix a thermometer
in it, and expose it to a source of heat, the mercury in the thermo-
meter will be seen to gradually rise up to 32 degrees. It then becomes
stationary, although the application of heat is continued. But another
change now sets in — the ice begins to melt. While this continues,
the thermometer does not rise, and the water at the end of the melting
is at exactly the same temperature that the ice was at its commence-
ment. As soon, however, as the ice is all melted, the mercury begins
again to ascend, and the water becomes warm. Now, all the heat
which entered the ice to liquefy it while the mercury was standing
still, went into retirement in the water which was produced — became
latent. It is very easy to find out how much heat becomes thus
hidden when ice changes to water. If we take an ounce of ice at
32°, and an ounce of water at 174°, and add them together, the ice
will melt and we shall have two ounces of water at 32°. The ounce
of hot water, therefore, parted with 142° of its heat, which has disap-
peared in melting the ice. 142° is thus the latent heat of fusion of
ice, which is hidden in the resulting water. The quantity of latent
heat absorbed by difierent solids in entering upon the liquid condition

STABILITY OF FOKMS PEESEEVED. 41

is variable, but a certain amount disappears in all cases. Thus, if a
mass of lead be heated to 594°, it will then become stationary, although
the addition of heat is continued ; but the moment the temperature
ceases to rise, it will begin to fuse, and the temperature will continue
steadily at 594° until the last particle of lead has been melted, when
it will again begin to rise. Those who have attempted to procure hot
water from snow for culinary purposes, know by the delay of the
result the great loss of heat which is involved. The heat necessary
simply to melt 100 pounds of ice, without raising its temperature a
single degree, would be sufficient to raise more than 80 pounds of ice-
cold water up to boiling.

54. Beneficial Effects of this Law. — This law of the latent heat of
liquidity, operates admirably to preserve the /orms of material objects
against the effects of fluctuating temperatures. The stability of bodies
is too important a circumstance, and their liquefaction too consider-
able an event, to be made dependent upon transient causes. If, when
ice is at 32°, the addition of one degree of heat would raise it to 33°,
and thus throw it into the liquid form, all the accumulated snows of
winter might be turned almost in an hour into floods of water, by
which whole countries would be inundated. But so large a quantity
of heat is required to produce this change, that time must become an
element of the process ; the snows are melted gradually in spring, and
all evil consequences prevented.

55. Principle of Artificial Freezing,— A solid may be changed to a
liquid without the direct addition of heat. Attraction or affinity may
produce the change. Yet the same amount of heat is required to go
into the latent state. Salts have a strong attraction for water. If we
put some common salt or saltpetre into water at the common temper-
ature, it will become colder. The salt in dissolving, that is, in assum-
ing the liquid state, must have heat ; it therefore takes it from the
surrounding water, which, of course, becomes colder. A mixture of
five parts sal-ammoniac and five of saltpetre, finely powdered, and put
in nineteen parts of water, will smk its temperature from 50° to 10° ;
that is, 40 degrees. When snow is mixed with a third of its weight of
salt, it is quickly melted. The powerful attraction of the salt forces
the snow into a liquid state ; but it cannot take on this state without
robbing surrounding bodies of the heat necessary to its fluidity. Ices
for the table are made in summer by mixing together pounded ice and
salt, and immersing the cream or other liquid to be frozen (contamed
in a thin metaUic vessel,) into the cold brine, produced by the melting
of the ice and salt. A convenient method of freezing a little water

42 VAEIOTJS EPrECTS OF HEAT.

without the use of ice, is to drench powdered sulphate of soda (glauher's
salt) with mnriatic acid. The salt dissolves to a greater extent in this
acid than in water, and the temperature may sink from 50° to zero.
The vessel in which the mixture is made, becomes covered with frost ;
and water in a tube, immersed in it, becomes speedily frozen.

56. Freezing liberates Heat. — If the change of a sohd to a liquid ab-
sorbs heat, the change of that liquid back again to the solid state, must
liberate it. If the liquefying process swallows up heat, the solidifying
process must produce the contrary effect — set it free again. As the
thawing of snow and ice in spring, is delayed by the large amount of
heat that must be stored away in the forming water, so the freezing
processes of autumn are delayed, and the warm season prolonged, by
the large quantities of heat that escape into the air by the changing of
water to ice. The same principle is made available to prevent the
freezing of vegetables, fruits, &c., in cellars during intense cold weather.
Pails or tubs of water are introduced, which, in freezing, give out
sufficient heat to raise the temperature of the room several degrees.
Freezing is thus made a means of warming.

57. Evaporation of Water. — "Water, at the surface, is constantly
changing into invisible vapor, and rising into the air, which is called
evaporation. It goes on at all temperatures, no matter how cold the
water is : indeed, evaporation constantly takes place from the surface
of ice and snow. The ice upon the window often passes off as vapor,
without taking on the intennediate form of water. Still, the rate of
evaporation increases as the temperature rises, so that it proceeds
faster from the surface of waters in temperate, than in higher latitudes ;
and more rapidly still at the equator. Evaporation into the air pro-
ceeds more rapidly when the weather is dry, and is checked when it
is damp. It is also hastened by a current. "Water will evaporate
much quicker when the wind blows, than when the atmosphere is
still, because, as fast as the air becomes loaded with moisture, it is re-
moved and drier air takes its place. Extent of surface also facilitates
evaporation. The same quantity of water will disappear much quicker
in shallow pans, than in deep vessels.

58. What occurs in Boiling. — "When water is gradually heated in a
vessel, minute bubbles may be seen slowly to rise through it. These
consist of air, which is diffused through all natural waters, to the ex-
tent of about four per cent., and which is partially expelled by heating.
As the temperature increases, larger bubbles are formed at the bottom
of the vessel, which rise a little way, and are then crushed in and dis-
appear. These bubbles consist of vaporized water, or steam, which la

CONDITIONS WHICH INFLUENCE BOILING.

43

formed in the hottest part of tlie vessel ; but as they rise through the
colder water above, are cooled and condensed. The simmering or singing
sound of vessels upon the fire just before boiling, is supposed to be caused
by vibratory movements produced in the liquid by the formation and
collapse of these vapor bubbles. As the heating continues, these steam
globules rise higher and higher, until they reach the surface and escape
into the air. This causes that agitation of the liquid which is called
boding or ebullition.

59. laflnence of the vessel in Boiling. — Different liquids boil at differ-
ent temperatures : but the boiling point of each liquid varies with
circumstances. The nature of the vessel has something to do with it,
which depends upon its attraction for the water. To glass, and pol-
ished metallic surfaces, it adheres with greater force than to vessels of
rough surfaces. Before the water can be changed to vapor in boiling,
this adhesion must first be overcome. Water upon the surface of oil,
boils two degrees below water in a glass vessel, in consequence of the
oU having no attraction for the water.

60. Measoring the Pressure of the Air.— Air has weight like visible
ponderable matter, and presses down upon the surface of water the
same as upon the ground. The pressure of the air is measured by a
J)arometer^ which is simply a glass tube about Fig. lo.

a yard long, closed at one end, filled with
mercury, and then inverted with its open
end in a vessel of mercury, as shown in
Fig. 10. The liquid metal in the tube, is thus
balanced against the air outside, and falls to
a point upon the scale, which exactly indi-
cates the pressure of the air. A column of
atmosphere from the ground to its upper
limit, is about as heavy as a column of mer-
cury 30 inches high. "We represent in the
figure, but a single column of air pressing
down upon the mercury; but we must re-
member that its surface is completely cov-
ered by such columns of air. Of course, the
empty space or vacuum in the upper part of the tube permits the mer-
cury to rise and fall without disturbance. From various causes the
weight of the atmosphere varies ; when it is heavier, it presses harder
upon the mercury, and drives it up ; when it is lighter, the mercury
falls. The ordinary fluctuations of atmospheric pressure, cause the
mercury to play along a scale of some two inches. As there is only a

Vacuum,
place of no
pressure. «..

Barometer tube.

44 VARIOUS EFFECTS OF HEAT.

certain quantity of air to press down upon the earth, in going up a
mountain we leave much of it below us : of course, what remains
above, is lighter, and presses with less weight. Hence, in ascending
a mountain, the mercury in the barometer sinks in proportion as we
rise higher.

61. Influence of Air-pressnTe upon Boiling. — It is reported by travel-
lers that, upon high mountains, meat cannot be cooked by the common
method of boUing. The reason is, that the boiling water is not hot
enough ; and the reason of that is that the pressure of the air being
partially taken off, the water finds less resistance to rising into vapor,
and a lower degree of heat produces the effect. The boiling point
thus fluctuates with the barometric column : the natural variations of
atmospheric pressure, at the same level, make a difference of 4| de-
grees in the boUing point of water.

62. Employment of the Principle in Refining Sugar.— It is often useful
to boil off liquids at low temperatures. In order to change coarse,
brown sugar into refined, white sugar, it has to be dissolved and
purified. It is then reproduced by evaporating away the water. But
the heat of the common boding point is too great. So the refiner
pumps out the air from above the boiling pans, by means of a steam-
engine. The pressure is taken off, and the water boUs away at a low
temperature, leaving the sugar crystals perfect.

63. Elevation of the Boiling Point. — If the weight of air pressing
upon a liquid affects its boiling point, for the same reason the weight
of the liquid itself, must affect it. When salts are dissolved in water,
they render it heavier, and its boiling point is always raised. Some
salts, however, raise it more than others. Water saturated with com-
mon salt (100 water to 30 salt), boils at 224° ; saturated with nitrate
of potash ( 100 water to 74 salt), it boils at 238° ; with chloride of
calcium, at 264°. Ether boils at 96° {blood heat); alcohol, at 174°;
turpentine, at 316°; mercury, at 662°. The viscidity of a liquid, or
the glutinous coherence of its particles is opposed to its free ebullition,

64. Spheroidal state of Water. — Water in contact with highly heated
metallic surfaces does not boil or vaporize. All may have noticed it
dancing or darting about in globules upon a hot stove. The reason
offered why a globule does not evaporate from a red-hot surface is,
that a stratum of steam is formed under it, which props it up, so that
it is not really in contact with the iron ; and steam being a noncon-
ductor, cuts off also the heat. Water enters upon the spheroidal state
between 288° and 340° of the hot surface : but when the temper-
ature falls, the steam no longer sustains the drop ; it is brought into

ITS RELATION TO BOILING.

45

contact with the iron, and is at once exploded into vapor. This prin-
ciple is made available in the laundry in judging of the degree of heat.
The temperature of the smoothing-iron is determined by its effects
upon a drop of saliva let fall upon it. If the drop adheres, wets the
iron, and is rapidly vaporized, the temperature is considered low;
but if it run along the surface of the metal, it is regarded as suf-
ficiently hot.

65. But little Heat reqnircd to maintaia Boiling. — If a liquid be con-
fined in a sufficiently strong vessel, so that its vapor cannot escape, it
may be heated to any desired point of temperature ; though at high
heats, vapors acquire such an expansive and explosive energy as to
burst vessels of the greatest strength. But if the liquid be exposed to
the air, it is impossible to raise its temperature above its natural boil-
ing point. All the heat that is added after boiling commences, is car-
ried away by the vapor. The rapidity with which water is raised to
the boiling point, depends upon the amount of heat which is made to
enter it. But when this point is reached, a comparatively small quan-
tity of heat will maintain it there just as well as more. Water boiling
violently, is not a particle hotter than that which boils moderately.
When water is brought to the boiling point, the fire may he at once
reduced. Attention to this fact would save fuel in many culinary
operations.

66. DouMe Vessels to Regulate Heat. — If we have a substance which,
placed directly over the fire, would receive an indefinite quantity of
heat, but which we desire to raise only to a Fio. ll.
certain temperature, we place it in a vessel
surrounded by another vessel ; the outer one
being filled with a liquid which boils at the
desired temperature. Heokee's farina ket-
tle. Fig. 11, is a culinary contrivance of
this kind. The outer vessel is fiUed with
water, while the inner one contains the
material to be cooked, which, of course, can-
not be heated higher than the boiling point,
and is therefore protected from burning. By
using any of the salt solutions mentioned
(63), higher heats may be communicated to
the internal vessel,

67. Why Paddings, Pies, &c., cool slowly. —
We have seen that water is a bad conductor of heat ; that is, heat does
not readily pass across its intervening spaces, from particle to particle,

Section of a culinary batli :
opening to introduce water.

46 VABIOUS EFFECTS OF HEAT.

and so become diffused through it. We do not, therefore, heat it by
conduction, but by currents produced within it (46), which distribute
and commingle the heat throughout its mass. It cools in the same
way. As the particles at the surface or sides lose their heajt, they fall
to the bottom, and others succeed them. If the particles of water
could remain stationary, it would be slow and difficult to heat, and
equally slow to cool. For this reason soups, puddings, pies, &c., which
contain large amounts of hot water, so enclosed and detained in their
places that they are not free to circulate, and therefore, are not in a
condition to lose their heat, keep hot longer, and cool slower than
equal bulks of simple fluids.

68. Concealed Heat of Vapor. — As the liquid state is the result of
heat combined with solids, the vaporous state is the further result
of heat combined with liquids. Enormous amounts of heat are
necessary to convert liquids into vapor, but the vapors are no hotter,
according to the thermometer, than the liquids were ; they are, there-
fore, reservoirs of insensible heat. All the heat which is necessary to
boil off a liquid, becomes latent in its vapor. The heat that thus
enters the boiling liquid without raising its temperature, must go
somewhere. It is not sensible in the vapor which ascends from its
surface, for that is no hotter than the liquid from which it came. It
is contained in the vapor, for it may aU be again recovered from it.
The quantity of heat which becomes latent in the process of evapora-
tion, is very large. "With the same intensity of heat it takes 5^ times
as long to evaporate a ponnd of water, as it does to raise it from
freezing to boiling ; it therefore receives 5^ times as much heat. If,
therefore, 180° were required to bod the pound of water, 1000° are
required to change it into a pound of vapor ; but, as the pound of
vapor is no hotter than the pound of Avater, 1000° of heat must of
course be concealed in it. The latent heat of steam is then 1000° ;
when condensed, it surrenders that 1000° of heat. The condensation
of a pound of steam wiU raise 5|- pounds of water from the freezing
to the boiling point. This fact makes steam a valuable agent for
transporting heat, as is done by means of steam pipes for warming
buildings (129). Wherever condensed, it liberates large quantities of
heat.

69. Cooling effect of Evaporation. — Evaporation is therefore a cooling
process — it buries or temporarily destroys active heat. For this reason
damp soils, although in all other respects like diy ones, are colder.
Evaporation dissipates the heat which falls upon them. The heat
poured down from the sun in torrid regions would be intolerable.

rrs EELATIOW TO EVAPOKATION. 47

were it not for the cooling effect of rapid evaporation. Apartments
are cooled in hot countries by evaporation, which proceeds from wet
curtains. The skin of the body contains millions of little microscopic
pores, through which water {perspiration) is constantly pouring out
to the surface. As it then evaporates into the air and absorbs
heat, it becomes a powerful cooling agency and regulator of bodUy
temperature ; while the vapor, which escapes from the breath, exerts
a cooling effect within the body. It is very interesting to observe
how the great capacity of liquid water for heat, makes it so gratefully
cooling as it enters the body ; and how its stUl greater capacity for
heat, when passing from the liquid state to the condition of vapor,
enables it so constantly to bear away from us the germs of fever as it
escapes from the system, in the form of insensible perspiration or
vapor. The cooling effect of fanning the face, is partly due to the
more rapid removal of the vapor of perspiration from the skin, and
partly to the conduction of heat by the particles of moving air.
Breezes cool us in the same way. Wet floors become a source of cold,
in rooms, through vaporization. The pernicious effect of wearing wet
clothing is caused by the rapid evaporation which proceeds from it,
thus robbing the body of large quantities of heat. "When a person is
obliged to remain in wet clothing, evaporation may be stopped by
putting on an outer garment, which cuts off the external air.

70. Season of " Mowing Hot and blowing Cold." — It was stated that
when air or gases are condensed, heat is set free ; on the contrary,
when they are expanded, their capacity for latent heat is increased,
it is absorbed, and cold is produced. This is a main cause of the
danger when streams of air reach us through cracks and apertures,
although a part of the mischief is caused by conduction. This peril
is expressed in the old distich —

"If cold air reach you through a hole,
Go make your will and mind your soul."

Air, spouting in upon us in this manner, not only cools by conduction
and evaporation, but, having been condensed in its passage through
the chink, it expands again, and thus absorbs heat. This is also
familiarly illustrated by the process of cooling and warming by the
breath. If we wish to cool any thing by breathing on it, the air is
compressed by forcing it out through a narrow aperture between the
lips ; as it then rarefies, it takes heat from any thing upon Avhich it
strikes. , If we desire to warm any thing with the brecth, as cold
hands, for example, we open the mouth and impel upon it the warm
air from the lungs without disturbance from compression.

48 rsnFLUElTCE OP HEAT UPON THE BODY.

VIII.— PHYSIOLOGICAL EFFECTS OF HEAT.

71. Local inflaence of Heat upon the Body. — It has been noticed that
the general effect of heat upon bodies is to expand them (15). It acts
in this way upon the living system, just as upon all other objects. The
pleasant sensation of warmth is occasioned by an expansion of the
vessels of the skin, and the liquids which they contain ; these are ren-
dered less viscid and thick by heat, and made to flow more readily,
which produces an agreeable feeling. If the application of heat to a
part be continued, the surface becomes red. The diameters of the
minute capillary blood-vessels are so expanded, that the red blood-disks
are enabled to enter tubes which would not previously admit them.
The temperature rises, and there is a slight sweUing or increase of the
volume of the part, owing partially to the dilatation of the solids and
liquids, but chiefly to the presence of an increased quantity of blood.
The living tissues at the same time become more relaxed, soft and
flexible, and allow rapid perspiration. More heat still produces greater
expansion. There is a sense of pain, the organic structure is decom-
posed, the liquids begin rapidly to dissipate in vapor, and the surface
becomes inflamed, blistered, and burned.

72. General influence of Heat upon the System. — The body is subject
to the action of two kinds of stimulants. Vital stimulants are those
external conditions, such as air, water, food and warmth, which are
necessary to the maintenance of life. Medicinal or alterative stimulants
are those agents or forces which produce temporary excitement within
the system, but ultimately depress and exhaust it. Now, in the pro-
portion that is necessary simply to maintain the system at its natural
temperature, heat is a healthful, vital stimulant; but beyond this it
becomes a disturbing, exhaustive, health-impairing agent. The first
effect in undue quantity is excitation ; the secondary effect, exhaustion.
In the first instance, sensibility is agreeably promoted, voluntary
muscular movement assisted, and the mind's action somewhat exalted ;
but to these effects succeed languor, relaxation, listlessness, indispo-
sition to physical and mental labor, and tendency to sleep. The body
possesses a powerful means of self-defence against excessive heat, in
tlie cooling influence of surface evaporation (69), but this power of the
system cannot be taxed with impunity. The rush of the circulation
to the surface, and the increased transpiration and secretion of the
skin, are accompanied by a necessary diminution in the activity of
some of the internal organs. As the exhalation from the skin rises,
the secretion of the kidneys and mucous membranes faUs. The pre-

EFFECTS OF SUDDEN CHANGES — ^FUEL. 49

vailing maladies of hot climates may be referred to, in illustration of
the effect of continued heat on the body. Fevers, diarrhoea, dysen-
tery, cholera, and liver diseases, may be regarded as the special mala-
dies of the burning, equatorial regions. — (Pereika.)

73. Consequences of snddea Cliangest — But the worst effect of exces-
sive heat, is not always the immediate stimulation, and consequent ex-
haustion which it iaduces ; it is the sudden exposure to various de-
grees of cold which often follows, when the system is iu a relaxed and
depressed condition, that accomplishes the most serious mischief, lay-
ing the traiQ for so many cases of afflicting disease, and premature
death. The effect of passing from an over-heated apartment out into
a freezing air bath, is suddenly to check the cutaneous circulation, and
drive the blood inward upon the vital organs, thus often engendering
fatal internal disease. It is thought that a temperature from 60° to
65° is, perhaps, the safest medium at which an apartment should be
kept, so that the individual may not suffer from transition to external
cold. If this temperature seem uncomfortably low, it is better to in-
crease the apparel than to run up the heat, and risk the consequences
of subsequent exposure.

IX. AETIFICIAL HEAT— PKOPERTIES OP FUEL.

74. Artificial heat may be produced in various ways, but the comr
mon method is by combustion^ which is a chemical operation carried
on in the air. All the heat which we generate for household purpo^
ees, is caused by the chemical action of air upon fuel. But what part
of the air takes effect ? The main bulk of the air is composed of
two elementary gases, oxygen and nitrogen. In every five gallons of
air, there are 4 of nitrogen and 1 of oxygen, mixed and diffused
through each other (281). Nitrogen, when separated, proves to have
no active qualities ; it cannot carry on combustion, — ^it puts out fire.
Oxygen, orr the contrary, when separated, proves to be endowed with
wonderful chemical energy. A fire kindled in it, burns with unnatu-
ral violence ; its chemical powers constitute the active force of tho
air. The nitrogen dilutes and weakens it, thus restraining its ac-
tivity.

75. Composition of Fuel,— Office of Carbon. — The fuel upon which
oxygen of the air takes effect in the burning process, consists of vari-
ous kinds of wood and coal. These are chiefly composed of three ele^
ments — oxygen, hydrogen, and carbon, in various proportions. The
oxygen they contain, contributes nothing to their value as fuel; tha^

3

so PROPERTIES OF FUEL.

depends upon the other elements : hence, the more oxygen, the less
there can be of these other substances, and, of course, the poorer the
fuel. Carbon exists largely in all woods and coals. Oxygen and hy-
drogen, when in their free state, — ^that is, uncombined, are always
gases ; they never appear as liquids or solids, and no one has yet been
able to force them into these states. Carbon, on the other hand, is
an unyielding solid. No chemist has ever yet been able to prepare
either liquid carbon or gaseous carbon. At the intensest white heat,
where nearly every other substance melts, or dissipates into vapor,
carbon remains fixed. It is the solidifying element of fuel, and it is
this property which makes our fires stationary.

76. Hydrogen, and its OfiSce in Fuel. — Hydrogen gas, the other ele-
ment of fuel, when set free is the lightest substance known, being 14
times lighter than air. It is of so light and volatile a nature, that it
will combine with solid carbon, and even iron, and carry them up with
it into the gaseous state. "When cembined with fuel, it is condensed
down iuto a solid state, but in the act of burning, it is released, and
escapes into the gaseous form. It therefore hums in motion, and it
is this which produces Jiame. In all ordinary combustion, the flame
is caused by the burning hydrogen, and the larger the quantity of this
substance in fuel, the greater the flame it wiU yield when burnt.

Y7. Why it is necessary to kindle a Fire. — Now, for these two sub-
stances, oxygen has powerful attractions, and combines with them,
producing combustion and heat. Yet atmospheric oxygen is every
where in contact with all kinds of fuel without setting them on fire.
"Why is this ? Because the natural attractions of these substances are
so graduated, that they do not come into active play at low tempera-
tures. If carbon combined with oxygen at common temperatures,
with the same readiness and force that phosphorus does, wood and
coal would be ignited like a match, at the slightest friction, and com-
bustive processes would be ungovernable. But as man, all over the
world, civilized and savage, is designed to develope and manage fire
through the agency of these substances, their energies have been
wisely restrained within the limits of universal safety. This makes it
necessary to resort to some means, as friction or percussion, to gener-
ate heat necessary to start conibustion, or kindle the fire.

78. Prodncts of Comlinstion. — "When the combustive process has
commenced, two things take place ; the fuel disappears, and the air is
changed. The substance of fuel is not destroyed, it only changes its
shape, takes on the invisible form, and mounts into the air. Oxygen
combines with carbon, both elements disappear, and a new product

ITS CHEMICAL CONSTmjElSrrS. 51

results — carbonic acid gas (293). As carbonic acid is thns given off
every where by combustion, it is a constant and universal constituent
of the atmospliere. It forms 1— 2000th of the air^ and would increase
in quantity, but it is ,. .nstantly withdrawn by plants. "When pure, it
extinguishes fire, and when mingled with the air it rapidly diminishes
its power of sustaining combustion. "When oxygen combines with the
hydrogen of fuel, it produces vapor of water, which rises with the
carbonic acid and disperses through the air.

79. Fuel is cbanged before it is burned. — In burning, oxygen does not
combine directly with hydrogen and carbon, changing them at once
to water and carbonic acid. The heat of combustion first decomposes
the fuel and re- combines its atoms, forming various compounds
under different circumstances, and it is with these that oxygen
unites. They consist mainly of hydrogen and carbon, and are
more abundant as the proportion of hydrogen in the fuel increases.
It is rare that these products, thus distilled out of fuel in the burning
process, are completely consumed by oxygen; a portion of them
escapes, constituting smoke.

80. Heating powers of Hydrogen and Carbon. — The proportion of
carbon in fuel is always very much greater than that of hydrogen, but
the amount of heat which they give out is not in proportion to their
relative weights, A given weight of hydrogen, when burned, will
produce three times as much heat as the same weight of carbon. A
pound of charcoal, which is nearly pure carbon, in burning, produced
sufficient heat to change 75 pounds of water from freezing to boiling ;
while a pound of hydrogen yielded heat enough in burning, to change
236.4 pounds through the same number of degrees. The heat is in
proportion to the oxygen consumed ; the pound of hydrogen united
with 8 pounds of oxygen ; while a pound of carbon took but 2| pounds
of it. The heating power of fuel thus depends upon chemical com-
position, but it is also influenced by other circumstances.

81. How Moisture affects the Value of Wood. — ^When wood is newly
cut, it contains a large quantity of water (sap), varying in different
varieties, from 20 to 50 per cent. Trees contain more water in those
seasons when the flow of sap is active, than when growth is suspend-
ed ; and soft woods contain more than hard. Exposed to air a year,
wood becomes air dried^ and parts with about half its water ; 15 per
cent, more may be expelled by artificial heat ; but before it loses the
last of its moisture, it begins to decompose, or char. The presence of
water in wood diminishes its value as fuel in two ways ; it hinders
and delays the combustive process, and wastes heat by evaporation.

52

PEOPEETEES OP FUEL.

Suppose that 100 pounds of wood contain 30 of water, they have
then but 70 of true combustive material. When burned, 1 pound
of the wood will be expended in raising the temperature of the water
to the boiling point, and 6 more in converting it into vapor ; making
a loss of 7 pounds of real wood, or J^ of the combustive force. Be-
sides this dead loss of 10 per cent, of fuel, the water present is an an-
noyance by hindering free and rapid combustion.

82, Heating Value of different kinds of Wood. — ^Equal weights of differ-
ent varieties of wood in similar conditions, produce equal quantities
of heat ; but it will not do to purchase wood by weight, on account
of the varying quantity of its moisture. It is sold by measure; but
equal measures or bulks of wood do not yield equal amounts of heat.
According to the careful experiments of Mr. Maeous Bttll, the rela-
tive heating values of equal bulks {cords) of several American woods,
are expressed as follows ; — shell-bark hickory being taken as 100.

Shell-bark Hickory
Pignut Hickory
White Oak
White Ash
Dogwood
Scrub Oak
Witch Hazel
Apple tree .
Bed Oak
White Beech
Black Walnut
Black Birch

100
95
81
77
75
73
72
70
69
65
65

Yellow Oak .

. . 60

Hard Maple

. 60

White Elm

. . 53

Eed Cedar

56

Wild Cherry

. 55

Yellow Pine

54

Soft Maple .

. 54

Chestnut .

52

Yellow Poplar

. . 52

Butternut .

. . 51

White Birch

. . 48

White Pine

42

83. Soft and Hard Woods. — Some woods are softer and lighter than
others, the harder and heavier having their fibres more densely packed
together. But the same species of wood may vary in density, accord-
ing to the conditions of its growth. Those woods which grow in for-
ests, or in rich, wet grounds, are less consolidated than such as stand
exposed in the open fields, or grow slowly upon dry, barren soils.

84. Wliy Soft and Hard Woods burn differently. — There are two stages
in the burning of wood : in the first, heat comes chiefly from flame ;
in the second, from red-hot coals. Soft woods are much more active
in the first stage than hard ; and hard woods more active in the
second stage than soft. The soft woods burn with a voluminous
flame, and leave but little coal ; while the hard woods pi-oduce less
flame, and yield a larger mass of coal. The cause of this is partly,
that the soft woods, being loose and spongy, admit the air more freely,
but it is chiefly owing to differences in chemical composition. Pure

BUKNING OF "WOOD AND COAL. 63

woody fibre, or lignin, from all kinds of wood, has exactly the same
composition ; a compound atom of it containing 12 atoms of carbon,
10 of hydrogen, and 10 of oxygen — or there is just enough oxygen in
it to combine with all its hydrogen and change it to water in burning.
But in ordinary wood, the fibre is impure ; that is, associated with
other substances which practically alter its composition. The hard
woods are nearest in composition, to pure lignin, but the softer woods
contain an excess of hydrogen. For this reason, they burn with more
vehemence at first ; more carbon is taken up by the hydrogen, in pro-
ducing flame and smoke, and the residue of coal is diminished. The
common opinion, that soft wood yields less heat than hard (equal
weights) is an error ; it burns quicker, but it gives out an intenser heat
in less time, and is consequently better adapted to those uses where a
rapid and concentrated heating effect is required.

85. Cbarcoal as Fnel. — Charcoal is the part that remains, when wood
has been slowly burned in pits or close vessels, with but a limited sup-
ply of air, so that all its volatile or gaseous elements are expelled.
Wood yields from 15 to 25 per cent, of its weight of charcoal ; the
more the process is hastened, the less the product. "When newly made,
charcoal burns without flame, but it soon absorbs a considerable por-
tion of moisture from the air, which it condenses within its pores.
When this is burned, a portion of the water is decomposed, hydi-ogeu
is set free, and there is produced a small amount of flame. Being very
light and porous, and its vacancies being filled with condensed oxygen,
(811) it ignites readily, and consumes rapidly. "Wood charcoal produces
a larger amount of heat than equal weights of any other fuel.

86. Mineral Coal as Fuel — Anthracite. — The pit coal which is dug from
beds in the earth, is a kind of mineral charcoal. It gives evidence of
having been derived from an ancient vegetation, which was by some
unknown means buried in the earth, and there slowly charred. Indeed,
the properties of the different varieties of coal, depend upon the degree
to which this charring operation has been carried. In anthracite,
which is the densest and stoniest of all, it has reached its last stage ;
the volatile substances are nearly all expelled, so that nothing remains
but pure carbon with a trace of sulphur, and the incombustible ash.
From its great density, when we attempt to kindle it, instead of
promptly taking fire, the heat is rapidly conducted away, so that the
whole mass has to be raised together to the point of ignition. "When
once tlioroughly fired, this coal burns with an intense heat for a long
time, though less freely in a grate than in a stove. It is diflicult in the
grate to keep the whole mass of coal in a state of vivid redness, as the

54 PKOPKRTIES OF FUEL.

air conveys away so much heat from the surface of the fire as to cool
it doAvn below the poiat of combustion (114). Anthracite burns without
flame, smoke, or soot, although with sulphurous vapors, which, when
the draught is imperfect, or when burned in a stove, are liable to
accumulate in the room, to the serious detriment of its inmates. The
anthracite fire is objected to by many as causing headache, and other
bad symptoms. Aside from its sulphurous emanations, the extreme in-
tensity of its heat, undoubtedly, has a share in producing these effects.
8V. Combustion of Bituminous Coal. — "When the great natural process
of underground charring is less advanced, the coals are Mtuminous ;
that is, they contain bitumen or pitch, a substance rich in hydrogen.
These ignite readily, and burn with much flame and smoke. Those
which contain the largest proportion of pitchy material, are known as
' fat' bituminous coal, and in burning, they soften or melt down into a
cake, {caking coal) and stop the draught of air. Those with less hy-
drogenous matter, are termed ' dry,' or ' semi-bituminous ' coal ;
they burn freely without cementing or caking. Bituminous coals fur-
nish illuminating gas by distillation in ii'on retorts ; a process of char-
ring with entire exclusion of air. The residue left after charring bitu-
minous coal, is called coke ; it is procured of the gas manufacturers
and used as fuel, burning quietly like anthracite, though, owing to
its sponginess, it is more easily kindled and yields less heat. Good
bituminous coal burns freely and pleasantly in an open fire, with an
agreeable, white flame, producing carbonic acid in large quantity, a
smaU proportion of svilphurous vapor, and the common carbonaceous
constituents of smoke (103). Its heat is mucli less violent than that
of anthracite.

88. Lignite or Brovrn Coal is that variety which seems to have been
least charred, and still retains the woody structure ; its combustive
value is low.

89. Heating Effects of the different Fuels. — The heating value of these
fuels, when burned under the same circumstances, have been deter-
mined as follows : One pound of wood charcoal wiE raise from the
freezing to the boiling point, 73 pounds of water. One pound of min-
eral coal wiU heat 60 pounds of water through the same number of
degrees ; and one pound of dry wood, 35 pounds of water in the same
way. These are the highest results obtained by careful experiments.
In practice, we do not get so great a heating effect ; and besides, the
circumstances under whicli the fuel is burned, whether it be in a stove
or fire-j^lace, makes considerable ditFerence in the result.

90. Amount of Air required to consume Fuel. — As the weight of air

ASCENT OF AIB THKOFGH CHIMNETS. 55

necessary to bum fuel is vastly greater than the fuel itself, and as air
is exceedingly light, it wiU be seen that immense bulks of it are con-
sumed in combustion. It requires 11.46 pounds of air to burn one
pound of charcoal; and as one pound of air occupies nearly 13 cubic
feet of space, the pound of charcoal will require about 150 cubic feet
of air. One pound of mineral coal is burned by 9.26 pounds of air, or
120 cubic feet ; and one pound of dry wood consumes 5.96 pounds, or
75 cubic feet of air. These are the smallest possible amounts that can
be made to effect the combustion; as fuel is usually burned, much
more is consumed.

91. Too much Air binders Comlmstion. — Yet if the object is simply to
produce heat^ the contrivances we employ should be adapted to admit
the least possible quantity of air beyond what actively carries forward
the combustion. Excess of air becomes detrimental to the burning pro-
cess, by conveying away heat which it does not generate, cooling the
fuel, and checking the rate of combustion. Indeed, so much air may
be projected upon a fire, as to cool it down below the burning point,
and thus put it out as effectually as water (114).

X.-AIR CURRENTS— ACTION AND MANAGEMENT OE CHIMNEYS.

92. Cause of the CMnmey Draught. — The candle flame tends upward;
its hot gases and the surrounding heated air rising in a vertical stream,
which illustrates the universal tendency of warmed air. No matter
how it is heated, it expands, because rarer and lighter, and is pressed
upward by that which surrounds it. Not that heated air has any
mysterious tendency to ascend, but there being less of it in the same
space, the earth does not attract it downward with the same force that
it does the denser and colder surrounding air. As the atmospheric
particles move among each other with the most perfect freedom, the
colder and heavier air takes the lower position, to which gravitation
entitles it, and thus drives the warmer air upward. This upward
tendency of rarified gases is the force made use of to supply our fires
with the large amount of air which they demand. The fire is kindled
at the bottom of a tube of iron or brick- work, called &Jlue or cMmney.
The atmospheric column within it is heated and rarified, and the outer
air drives in to displace it. This, in its turn, is also heated and ascends ;
a continuous current is established, and a stream of fresh air secured
to maintain the combustion. The chimney also serves to remove from
the apartment the noisome and poisonous products of combustion.

93. Conditions of the Force of Draught.— The force of the chimney

m ACnOBT AND MAN-AGEMENT OP CHIMIirETS.

draught depends upon the velocity of the rising curientj and that again
upon the diiference of weight between the column of air in the chim-
ney, and one of equal size outside of it. Three circumstances influ-
ence the force of draught : the temperature, length, and size of the air
column within the chimney. The hotter it is, the higher it is, and the
larger it is, within certain limits, the greater will be its ascensional
force. All high chimney stacks, with large channels, containing
highly rarified air, produce roaring draughts ; wliile if they be short
and narrow, and their temperature low, the draught is proportionally
enfeebled. Friction against the sides of \he chimney, especially if it
be small, operates powerfully to retard the draught. If the chimney
be contracted at the bottom, the velocity of the entering air will be
increased. If it be narrowed at top, the smoke and hot air wiU be
discharged above with more force, and hence be less likely to be
driven down by slight changes in the direction of the wind ; yet con-
tractions in the diameter of the chimney at any point, diminish the
total amount of air passing through. In practice, chimney-draughts
are influenced by several other circumstances, and are frequently so
interrupted, that they refuse to carry off the products of combustion,
and are then said to smoJce. Yet these general statements require
qualification. A chimney may be so high that the loss of heat through
its walls shall cool the current down to a point of equilibrium with,
the outer air ; the draught of a high chimney shafl has been greatly
augmented by enclosing it in an outer case to prevent radiation. Nor
is the current of air that passes through a chimney, strictly in propor-
tion to the degree of its heat. The draught, at first, increases very
rapidly with the temperature, but gradually diminishing, it becomes
constant between 480° and 570°, beyond which it diminishes, and at
1800° it is less than at 212°. The reason of this is found in the
great expansion of air at a high temperature, by which its volume is
so much increased, that, although the velocity may be Very great, the
quantity, when reduced to the temperature of the atmosphere, is less
than at a lower temperature. — Wtmait.

94. Winds eansc Chimneys to Smoke. — A high building, or a tree
standing close to a chimney aud overtopping it, often disturbs its
draught. The wind passing over these objects, tails down like water
over a dam, and stops the ascending current so that smoke is forced
back into the room ; or the wind mny strike against the higher object,
and, rebounding, form eddies, and thus beat down the smoke. "When
chimneys are not thus commanded by eminences in the vicinity, gusts
of air may still interfere with their draught. To prevent this, they

DISTURBANCES OP THE DKAUGHT.

57

are often mounted with turncaps, cowls, or ejectors (354) -wliicli are
so constructed that the eflFect of the passing wind is to draw off
the air from the chimney, forming a partial vacuum into which the
gases and smoke rush from below, and so establish an upward current.

95. New and Damp ChinmeySi — "When chimneys are new, the brick
and mortar being damp, are good conductors of heat, and take it
rapidly from the rising current of warm air. This condenses it,
obstructs its ascent, and if the fire below be very hot, the chimney
smokes. As it becomes dry, however, and is gradually covered with
non-conducting soot, this source of difficulty is removed.

96. Cold Exposures — Descending Draughts. — Chimneys in the north
end of a house, exposed to cold winds, often draw much less perfectly
than those on other sides, or in the stiU more favorable warm interior
of a building. The air in a chimney in the north or shaded side of a
house is liable to cool in summer, so as to have a downward, draught
when not used. If the temperature of the chimney be nearly the
same as that of the outer air during the day, the external cooling at
night may also create a descending current. When, therefore, the
smoke from the neighboring chimneys passes over tlie tops of those
that are drawing downwards, it is sucked in with the current and
fills the room below.

97. Currents connteracting each other. — We have seen that it is
only when the atmosphere is of a perfectly uniform temperature that
it is perfectly still ; the slightest inequality in its Fig. 13.
degree of heat, throws it promptly into movement.
We are apt to forget the exceeding dehcacy with
which the different portions of air are balanced
against each other. This may be easily shown.
If two tubes of unequal height be united by a third
(Fig 13), the candle in the longer tube wiU. over-
come that in the shorter, and create a downward
current in the latter; or if two tubes of equal
length, xmited by a third, as in Fig. 14, have a
candle in each, one is soon overcome by the other ;
and this may happen, even when an opening is made in the third
tube, admitting a limited supply of air. It is sometimes attempted to
make a current proceeding from a fire, traverse two flues, which join
again before discharging their smoke into the air. But this is
difficult, if not impossible ; for though currents may be commenced in
both routes, one quickly neutralizes the other, and but a single flue
's used.

58

ACTION AND MANAGEMENT OP CHIMNErS.

Fig. 14.

98. One Chimney OTerpowering another. — Wlien

there are two fire-places in a room, or in rooms
communicating by open doors, a fire in the one
may burn very well by itself; but, if we attempt to
light fires in both, the rooms are filled with smoke.
The stronger burning fire draws upon the shaft of
the weaker for a supply of air, and of course brings
the smoke down with it. This difiiculty may be
remedied by opening a door or window, so as to
supply both fires with the necessary air. The same
efiect may take place, even though the two rooms
be separated by a partition, when they communi-
cate atmospherically by the joints and doors. Some-
times, where the windows are tight, a strong kitchen fire may over-
power all the other chimneys in the house and cause them to smoke.

99. Upper and lower Flues — A current entering a chimney through
a flue horizontally^ may interrupt its draught ; in all cases of flues
entering chimneys, they should be so arranged that the smoke may
assume an upward direction corresponding to the course of the main
current. There is great danger of smoke when the flue of an upper
room is turned into the chimney of a lower room. If a fire is kindled
in an upper room when there is none below, the cold air in the main
shaft rises, and, mixing with the warm air, dilutes it, and thus checks
or obstructs the ascent j while if the lower fire only be kindled, the
cold air from the upper flue will rush into the shaft, and cooling it
down at that point, may cause the smoke to descend into both rooms.
The remedy is, either to keep a fire in both fire-places or to close one
with a fireboard.

100. Admission of too much Air. — Too large openings in fire-places
often occasion smoke by admitting so much air from the room as to
cool the upward current, and thus impair its ascensional force. If
the fire-place be too high or capacious, or its throat too large, the air
is drawn from a large space, or it may pass round behind the fire by
way of the jambs on both sides ; the current is thus impeded, and
the flame, which should be drawn backward, rises directly against the
mantel-bar and escapes into the room. The fire-place should be so
constructed as to compel all the air which enters it, to pass through
or close to the fire.

101. Admission of too little Air. — It is well known that a smoky
chimney is often relieved by opening a window or outer door ; where
this is the case, the difficulty is a deficiency of air to supply the

DEFICIENCY OP AIE-SUPPLT.

59

Fig. 15.

draught. "Want of a copious and regular supply of air is by far the
most common cause of smoky chimneys. However well constructed
and arranged may be the flues and fire-places, if they are not supplied
with a proper amount of air they will inevitably smoke. Of course
if the room be nearly air-tight, there is no air to supply a current, and
there will be no current, for as much air as escapes through the
chimney must be constantly furnished from some other source. In
such a case, the smoke not being carried off will diffuse through the
room. There may even be a double current in the
chimney, one upwards from the fire and another from
the top downwards, as shown in Fig. 15 ; these two
currents meeting just above the fire, part of the smoke
is driven into the room. To ascertain the quantity
needed to be brought in under these circumstances,
Dr. Feanklin's plan was to set the door open until
the fire burned properly, then gradually close it nntil
again smoke began to appear. He then opened it a
little wider, until the necessary supply was admitted.
Suppose now the opening to be half an inch wide, and
the door 8 feet high, the air-way wUl be 48 square
inches, equal to an orifice 6 inches by 8. The intro-
duction of this air is to be in some way effected, the
question being where the opentug shall be made. It
has been proposed to cut a crevice in the upper part
of the window-frame ; and, to prevent the cold air
from falling down in a cataract upon the heads of the . 'Double current

1 • 1 in • , 1 1111 . •. ^i* cbimney caus-

mmates, a thin shell is to be placed below it, sloping ing smoke,
upwards, which would direct the air toward the ceiling. The modes
of introducing air will be noticed in another place (351).

102. Draughts througli a Boom. — Currents of air through a room,
as from door to door, or window to window, when open, may coun-
teract the chimney draught ; or a door in the same side of the room
with the chimney may, when suddenly opened or shut, whisk a cur-
rent across the fire-place, to be followed by a puff of smoke into the
room.

103. Visible Elements of Smoke. — Smoke consists of all the dust and
visible particles of the fuel which escape unbnrnt, and which are so
minute as to be carried upward by ascending currents of air. It is
chiefly unconsumed carbon in a state of impalpable fineness, which is
deposited as soot along the fiue, or, swept upward by the air current,
is carried to a greater or lesser height, and finally falls again to the

60 APPAEATUS OF WARMING.

earth. Thus all that is visible of smoke is really heavier than air,
which may be shown by placing a lighted candle in the receiver of an
air-pump. By then exhausting the air, the flame is extinguished ;
and the stream of smoke that continues to pour from the wick, falls
Fig. 16. °^ *^® pump-plate, as is seen in Fig. 16, because there
is no air to support it. Often, in days when the wea-
ther is said to be ' close' we notice that the smoke
floats away from the chimney-top and falls instead of
rising ; so that the air, even within the zone of breath-
ing, becomes charged with the sooty particles. The
atmosphere is so rare and light that it cannot sustain
the heavy smoke. The common impression that the
air on these occasions is heavy^ which prevents smoke
from rising, is quite erroneous. The visibility of smoke is not entirely
due to sooty exhalations. Watery vapor is a large product of com-
bustion, and, when the air is warm and dry, it remains dissolved and
invisible ; but, when it is cold or saturated with moisture, it will
absorb no more, and that which rises from the chimney appears as a
vapor-cloud, and thus adds greatly to the apparent bulk of the smoke.

104. Other constitnents of Smoke. — Smoke contains many sub-
stances beside the carbonaceous dust, which vary with the conditions
of combustion and the kind of fuel used. Coal smoke is alkaline from
the presence in it of ammoniacal compounds, while wood-smoke is
acidulous fi'om the ligneous acids it contains. The smarting sensation
produced by wood-smoke in the eyes, is due to the highly irritating
and poisonous vapor of creosote formed in the burning process.

XI.— APPARATUS OF WARMING.

105. The various devices for warming are to be considered in a
twofold relation, as generating heat and affecting the breathing quali-
ties of the air. These topics are often treated together ; but, as we
desire to present the subject of air and breathing with the utmost
distinctness, a separate part wiU be assigned to it, and the heating
contrivances will then be reconsidered in respect of then* atmospheric
influences.

106. How Booms lose Heat, — Apartments lose their heat at a rate
proportional to the excess of their temperature above the external
air ; the higher the heat, the more rapidly it passes away. Large
quantities of heat escape through the thin glass windows. The win-
dow panes both radiate the heat outward, and it is conducted away

SOUECES OP THE LOSS OF HEAT. 61

by tlie external air. Glass is a bad conductor of beat, yet the plates
used are so tbin as to oppose but a very sligbt barrier to its escape ;
on tbe other hand, it is an excellent absorber and radiator, — so that,
in fact, it permits tbe escape of heat almost as readily as plates of iron
of equal thickness. Tbe loss of heat in winter, by single windows, is
enormous. Three-fourths or 75 per cent, of the heat which escapes
through tbe glass, would be saved by double windows, whether of
two sashes or of double panes only half an inch apart in the same
sash. Heat is also lost by leakage of warm rarefied air through
crevices and imperfect joinings of windows and doors, while cold air
rushes in to supply its place. Heat also escapes through walls, floors,
and cedings, at a rate proportioned to the conducting power of the
substances of which they are composed. Another source of loss is
from ventilation where that is attended to, whether it be by the chim-
ney, or through apparatus made on purpose, and it may be estimated
as about 4 cubic feet of air per minute for each person. This is the
lowest estimate ; authorities differ upon the point, the ablest putting
it much higher (325). The loss from this source is proportional to
tbe scale adopted. Much heat, besides, is conveyed away by tbe cur-
rents necessary to maintain combustion. To renew the heat thus
rapidly lost in these various ways, different arrangements have been
resorted to, which wdl now be noticed.

107. Onr Bodies help to Warm the Rooms. — In estimating the sources
of heat in apartments, we must not overlook that generated in our
own systems. Tbe beat lost by the body in radiation, is gained to the
apartment ; in the case of an individual, the amount is small ; but
where numbers are collected, tbe effect is considerable. In experi-
ments made upon this point, by enclosing different individuals succes-
sively in a box lined with non-conducting cotton, open above and be-
low, and suspended in the air, it was found first, that there is a current
ascending from the person on all sides ; and second, that the air was
found, on an average, 4° higher above the bead than below the feet.
In a dense crowd, air admitted slowly through the floor at 60°, rises
to 70° or 80° before reaching the head. The temperature of a lecture
room 9 feet high, and 34 by 23 square, occupied by 67 persons, and
the outer air at 32°, rose by the escape of bodily heat during the lea
ture, twelve degrees.

108. Ancient Method of Warming. — The chimney is a modern device,
coming into use only 500 or 600 years ago, with the mariner's compass,
the printing press, mineral coal, and that array of capital inventions
and discoveries which appeared with tbe daybreak of the new civili-

62 APPAEATUS OP WAEMESrCt*

zation that succeeded the dark ages. Previously to that time, houses
were heated as Iceland huts are now, — by an open fire in the middle
of the apartment, the smoke escaping by the door, or passing out
through apertures in the roof, made for this purpose. The Greeks and
Romans had advanced no further than this in the domestic manage-
ment of heat. They kept fires in open pans called hraziers. Those
of the Romans were elegant bronze tripods, supported by carved im-
ages with a round dish above for the fire. A small vase below con-
tained perfumes, odorous gums, and aromatic spices, which were used
to mask the disagreeable odor of the combustive products. The por-
tion of the walls most exposed were painted black, to prevent the
visible effects of smoke ; and the rooms occupied in winter had plain
cornices and no carved work or mouldings, so that the soj>t might be
easily cleared away.

1.— OPEN FIRE-PLACES.

109. Structure and Improvements. — With the chimney came the
fire-place, which is an opening on one side of its base. At first it was
an immense recess with square side- walls (jambs) and large enough to
contain several persons, who were provided with seats inside the
jambs. These fire-places were enormously wasteful of fuel, and Avero
in other respects very imperfect. They have been gradually improved
in various ways. By reducing their dimensions and greatly contract-
ing the throat, the force of draught is increased and the liability to
smoke diminished. By lowering the mantle or breast, the flow of
large masses of air which entered the chimney without taking part in
the combustion, was stopped ; while, by bringing the back of the fire-
place forward, the fire was advanced to a more favorable position for
heating the room. Rays of heat, like those of light, when they strike
on an object, are reflected at the same angle as that at which they
faU, — that is, the " angle of incidence is equal to the angle of reflec-
tion." Now, when the jambs were placed at right angles with the
back, that is, facing each other, they threw their heat by reflection
(and when hot by radiation) backward and forward to each other
across the fire. By arranging the jambs at an angle, they disperse
the heat through the room. Cottnt RujUfoed states that the proper
angle for the positions of jambs is 135 degrees with the back of the
fire-place.

110. How the open Fire-place warms the Eoom. — The heat of com-
bustion from the open fire is entirely radiant — thrown off directly
from the burning fuel, or reflected from the sides and back of the fire-

OPEN FIEE-PLACE8 WASTE HEAT.

63

place. It strikes upon tlie walls, ceiling, floor, and furniture of the
room ; a portion of it is reflected in various directions, and the rest is
absorbed. The objects which receive it are wanned, and gradually
impart their heat to the air in contact with them ; — gentle currents
are thus produced, which help to equalize the temperature of the
room. Those portions of the air which are in contact with the fire,
become heated by conduction, but they immediately rise into the
chimney, and are, therefore, of no use in heating the room. As a fire-
place is situated at the side of the apartment, and as radiant heat
passing from its source decreases rapidly in intensity (23), it is
obvious that the room will be very unequally heated. Near the fire
it wUl be hot, whUe the remote places will be in the opposite condi-
tion. There is a semicircular line around the fire-place, in which
persons must sit to be comfortable, within which .ine they are too
hot, and beyond which they are too cold. Of course, in this method of
warming, the body receives the excess of heat only upon one side at once.

111. Tlie open Fire not Economical. ^Fuel gives out its heat in

two ways, by radiation and by immediate contact. Peolet has shown,
by ingenious experiments, that the radiated heat from wood was i ;
from charcoal and hard coal about J, of the whole amoimt produced.
As a general result, those combustibles which burnt with the least
flame yielded the most radiant heat. As the radiant heat is thus the
smaller quantity, the arrangements in which it alone
is employed are by no means economical ; yet the open
fire-place heats entirely by radiation, and is therefore
the most wasteful of all the arrangements for heating.
It is said that in the earlier fire-places 7-8ths, and
KuMFOED says 15-1 6ths of aU the heat generated^
ascended the chimney and was lost. It is probable
that in the best constructed fire-place, from 1-2 to
3-4ths of all the heat is thus wasted. The fire-place
is greatly improved in economy and heating eflBciency
by so constructing it that it may supply a current of
heated air to the room. This is done in numerous
ways, as by setting up a soap-stone fire-place within \A}
the ordinary one, and leaving a vacant space between ^
them, into wbich cold air is admitted from without,
which is then thrown into the room through an open-
ing or register above. This is an excellent plan ; it is
executed with various modifications, but, if well done, out warmed by the
it answers admirably. Even a flue made of some thin ^''^-P^ace.

Fia. 17

64 APPABATUS OF WABMING.

material, and contained in the chimney, the lower extremity com-
municating with the external air, and the upper with the room
(Fig. 17), answers a most useful purpose. Heat is saved; abundance
of air is furnished to the room without unpleasant draughts, while a
common cause of smoke is avoided (101).

112. Franklin Stovct — Dr. Feanklin contrived a heating apparatus
of cast iron, which he called the Pennsylvania fire-place^ but which
is generally known as the FranTcUn stove. It otfers one of the best
methods of managing an open fire. It is set up within the room, and
the hot air and smoke from the fuel, instead of escaping from the iire
directly up the chimney, is made to traverse a narrow ani circuitous
smoke flue, which gives out its heat like a stove-pipe ; at the same
time air is introduced from out of doors through air-passages which
surround and intersect the smoke-flue, and, after being warmed, it is
discharged into the room by means of proper openings. This appa-
ratus warms, not only by radiation from the burning fuel like the
common fire-place, but also by radiation from the hot iron ; besides,
the air of the room is heated by contact with the metallic plates, and
there is still another source of warmth in the hot air brought in from
without.

113. Coal Gratesi — As coal contains more combustible matter in
the same space than wood, and produces a more intense heat, a much
smaller fire-place answers for it. A very narrow throat in the chim-
ney is Buflicient to carry off the smoke. The coal-grate is a more
economical contrivance for warming than the larger wood fire-place,
chiefly because it lessens the current of air which enters the flue. In
the wood fire-place a copious stream of warm air passes up the chim-
ney, which takes no part in combustion, but carries off with it much
heat, the place of the escaping warm air being supplied by cold air
from without. The coal-grate is closed, like the fire-place, on three
sides, the front consisting of metallic bars or grates, which, while they
confine the coal, suffer the heat to radiate between them into the
room. The sides and back of the grate should be formed of fire-brick,
soap-stone, or some slowly-conducting substance, and not of iron,
which conducts away the heat so fast as to deaden the combustion —
for a fire may be effectually extinguished by contact of a good con-
ducting solid body. For this reason, as Eumfoed first pointed out,
there should be as little metal about a grate as possible, the bars
being made as slender and as wide apart as practicable, so as to inter-
cept the fewest radiations from the burning surface.

114. Conditions of Comtustion in the Grate. — The form of the grate

COMBUSTION m GEATES. 65

should be such as to expose the largest surface of incandescent coal to
the apartment. If it has a circular front, there will be not only more
surface, but the heat may then be radiated in all directions ; yet, if too
great a surface is exposed to air, in extreme cold weather it carries
off the heat faster than combustion renews it ; and the coal, if it be
anthracite, grows black upon the exposed side and burns feebly. The
art of burning fuel to the best advantage in open grates, is to main-
tain the whole mass in a state of bright incandescence, by preventing
all unnecessary obstruction of heat, either by contact of surrounding
metal, or currents of cold air flowing over the fire. It is very difficult,
however, to expose a large fire-surface to the atmosphere, and at the
same time properly regulate the quantity of air admitted. It is pos-
sible for fuel to smoulder away and entirely disappear with the pro-
duction of very little sensible heat. To be burned with economy,
therefore, it must be burned rapidly under the most favorable condi-
tions of vivid combustion. The heat absorbed by the fuel, the sur-
rounding solids, or the rising vapor, is of course not available, but
only the excess which is emitted into the room. To cause this lively
and perfect combustion, aU the air which comes in contact with the
fuel must be decomposed and part with the whole of its oxygen.
Every particle of air passing up through the fire, which does not help
the combustion, hinders it, first by carrying off a portion of the heat,
and second by cooling the ignited surface so that it attracts the oxygen
with less vehemence, and thus causes the fire to languish. The air
should also be pure, that is, as little as possible mingled with tho
gaseous products of combustion. Air entering below a fire, rapidly
loses its oxygen and becomes contaminated with carbonic acid ; both
changes unfitting it for carrying on the process actively in the upper
regions of the fire. If, therefore, the mass of burning material is too
deep, the upper portions burn feebly and at least advantage ; yet if
the pieces of coal be large, scarcely any depth of fuel wUl be sufficient
to intercept and decompose the cold air which rises through the wide
spaces. If the coal be not large, perhaps a depth of four or five
inches wUl be found most economical.

115. Different kinds of Grate— The modifications and variations of
the fire-place and coal-grate are innumerable : and the multiplied de-
vices which are continually pressed upon public attention, are, many
of them, but reproductions of old plans. The use of a simple iron plate
for a fire-back, has been employed to warm an adjoining room situated
behind the fire-place. For the same purpose grates have been hung
upon pivots, so as to revolve, and thus warm two rooms, as library

66 APPARATUS OP WAEMESTG.

and bedroom alternately. In Golson's stove-grate, the fire is contained
in an urn or vase-sliaped grating, and is surrounded by a circular re-
flector whicb throws the rays, both of heat and light, into the room in
parallel lines. Ooal-grates are also constructed on the principle of the
double fire-place, by which warmed air is introduced into the room from
without. Dr. Feanexin devised an ingenious grate called the cirailar
fire-cage. It was so hung as to allow it to revolve. The coal was
ignited, as usual, at the bottom, and when the combustion was well
advanced, the cage was turned over so as to bring the fire at the top
By this means, the fresh coals at the bottom were gradually ignited,
and their smoJce having to pass through the fire above them, was en-
tirely consumed.

116. Arnott's new Grate. — Dr. Aenott has recently constructed a
new grate, in which the same benefit — the consumption of smoke, is
secured. The bottom of the grate is a movable piston, which may be
made to fall a considerable distance below the lower grate bar. A
large charge of coals is then introduced, which rests upon the piston
and fills the grate. They are lighted at the top, so that the heat passes
downward and consumes the smoke as it is formed below. As the
coals waste away at the top, the piston may be raised by the poker
used as a bar, and thus fresh coal is supplied to the fire from ieneath.
"When the first charge is consumed and the piston is raised to the bot-
tom of the grate, a broad, flat shovel is pushed in upon the piston
which supports the burning coals, and afibrds a temporary support for
the fire. The piston is then let down to the bottom of the box, and a
new charge of coal shot in. This arrangement is valuable for abating
the smoke nuisance where bituminous coal is burned. Much inge-
nuity has been spent upon contrivances to burn or consume smoke.
The thing however is impracticable. "When smoke is once produced
by fire, we can no more advantageously convert it to heating purposes
than we can the smoke of a badly burning candle to the purposes of
lighting. When smoke escapes from the ill-adjusted flame of a lamp,
we notice that the flame itself is duU and murky, with diminished light ;
but if it burn without smoke, the flame is white and clear. But we
do not say in this case, the lamp turitis its smoTce^ but that it hums
without smoTce. The aim should be, so to conduct the first combustion
that smoke shall be prevented.

117. Grates should not be set too low. — As the open fire warms by
radiation, it should be so placed as to favor this mode of diffusing heat.
The tendency of currents of heated an* to rise, secures suflBciently the
warmth of the upper portion of the room, so that the main object of

EFFECT OP TOO LOW EIEES.

67

Fio. 18.

the grate should be to heat the floor. If the fire is situated very low,
the radiation will be considerable upon the hearth, while but few heat-
rays will strike further back upon the floor. They will pass nearly
parallel along the carpet or floor, just as the solar rays, at sunrise,
dart along the surface of the earth. If, however, the fire be raised,
its downward radiations strike upon the floor and carpet at some dis-
tance back, with sufficient force to warm them, just as the sun's rays
are more powerful when he shines from a considerable distance above
the horizon. If a in (fig. 18), represent a radiating point or fire in a
room, and & c the floor, it will be seen
that no heat-rays fall upon it ; while
if the floor be at d e, it will receive
rays from the fire. " In such arrange-
ment it is seen by where the ray-lines
intersect this floor, that much of the
heat of the fire must spread over it,
and chiefly between the middle of the
room and the grate, where the feet of «|
the persons forming the fireside cir-
cle are placed. Striking proof of the ^^
facts here set forth, is obtained by

laying thermometers on the floors of rooms with low fires, and with
similar rooms with fires as usual of old, at a height of about 15 or 16
inches above the hearths. The temperature in the upper parts of all
these being the same, the carpets in the rooms with low fires are colder
by several degrees than in the others."

2.— STOVES.

118. How Rooms are warmed by Stoves. — The stove is an enclosure,
with us, commonly of iron, so tightly constructed as to admit through
an aperture or damper, only sufficient air to maintain the combustion
of the fuel, which may be either wood or coal. The heat generated
within is communicated, first to the metal, and then by that to the
apartment. It is usually situated quite within the room, the products
of burning being conveyed away by a fine or pipe. The stove imparts
its heat by radiation in all directions ; it also heats the air in contact
with it, which immediately rises to the upper part of the room, that
which is cooler taking its place in the same manner as heat is dis-
tributed through water in boiling (46).

119. Briek, Earthenware, and Porcelain Stoves.— Stoves made of these

68 APPAEATXrS OF ■wakmhstg.

materials are most common in Germany and Kussia. They are gen-
erally made to project into the room from one side, like a chest of
drawers or a sideboard ; the door for the fire being sometimes in an
adjoining apartment. These stoves heat more slowly, and conse-
quently give out their warmth for a longer time than those made of
iron, which are subject to rapid variations of temperature.

120. Self-regnlating Stoves. — These are stoves to which are appended
contrivances for regulating the draught. The principle employed is
the expansion of bodies by heat, and their contraction by cold. A
bar of brass or copper is so attached to the stove, that when the heat
within increases, it lengthens ; it then moves a lever and closes the
aperture which admits the draught. This checks the fire, and causes
the bar slowly to cool ; it now contracts, and again opens the aper-
ture of draught. Dr. Aenott produced the same result by means of
a column of air contained within a tube acting upon mercury which
moved a valve, and thus controlled the air-aperture. As the addition
and subtraction of heat cause gases to change their bulk m ore readily
than solids, a well constructed regulator of this kind woUd be more
sensitive and prompt in action than one of metal.

121. Air-tight Stoves. — The so called air-tight stoves are very
common. They are designed to admit the air in small and regulated
quantities, so as to produce a slow and protracted combustion. This
mode of generating heat is less economical than is generally supposed.
To become most perfectly available, heat must be set free at certain
rates of speed. The compounds formed by combustion at a low tem-
perature, generate much less heat than those which result from quick
burning. Indeed, in the low, smothered combustion, the fuel under-
goes a kind of dry distillation^ producing carburetted hydrogen gases
which escape into the chimney as unburnt volatile fuel, and are of
course lost. These gases are inflammable, and when mixed with air,
often cause explosions in air-tight stoves. Dr. TJee found that
while 3i pounds of coke evaporated 4^ pounds of water, from a cop-
per pan, when burned in a single hour^ yet that when the same
amount was burned in twelve hours, but httle over half that quantity
of water was evaporated. As has been previously stated, to evolve
the largest amount of heat from fuel it must bo burned rapidly, and
with a supply of air sufficient to oarry the oxidation at once to its
highest point, by the production of carbonic acid and water. Where
the fuel is quickly and completely burned, and the hot, escaping gases
are made to traverse a sufficient length of pipe to have parted with
nearly all their heat before entering the chimney, there remains noth-

POINTS SECUI5ED BY THE BEST STOVES. 69

ing to be desired on the score of economy. It is evident that all the
heat has been retained in the room, and in this case the stove becomes
the most efficient heating apparatus.

122. EflTect of Elbows ia Stovepipes. — The heating action of the sheet-
iron flue or stovepipe, is derived from the hot current of air within it.
In proportion therefore as it contributes to the warmth of the room,
this current of escaping air is cooled. That this cooling of air within
the pipe takes place rapidly, may be shown by the difference of tem-
perature at its connection with the stove, and where it enters the
chimney. The cooling takes place of course from without inwards ;
the outer stratum of the hot air current which is in contact with the
pipe cools faster than the interior portion, so that the centre of the
current is the hottest. Now it is well known that the effect of elbow-
joints in a pipe, is to make the same length of it much more efficacious
in warming a room, than it would be if straight. The cause of this is,
that the heated air, in making abrupt turns, strikes against the sides
with sufficient force to break up and invert its previous arrangement,
and so mingle it, that the hotter air from the interior of the current
is brought more into contact with the sides of the pipe, and more heat
is thus imparted. It also checks the rapidity of the current. As radi-
ation proceeds much slower at low temperatures than at liigh ones,
the pipe, as it recedes from the stove, becomes rapidly less and less
useful as a means of diffusing heat into the apartment ; it gives out
less heat, in proportion to what it contains^ than the hotter parts of the
pipe. There will, therefore, be little gained by greatly lengthening it.

123. Best qnalities of a Stove. — The desirable points to be secured in
the construction and management of stoves, are, Jirst^ ready contriv-
ances for regulating the draught; second^ accurate fitting in the joinings,
doors, dampers, and valves, to prevent the leakage of foul gases into
the room ; third, enclosure of the fire-space, with slow conductors, as
fire-brick or stone ; fourth, a high temperature, attained by the rapid
and perfect combustion of the fuel ; and fifth, to bring all the heated
products of the combustion in contact with the largest possible alsorl)-
ing and radiating metallic surface, so that the iron in contact with
the air may not be overheated, but give out its warmth at a low
temperature. Large stoves, moderately heated, are therefore most
desirable. The cooler the surface of the stove, or the nearer it is in
temperature to the air of the room, the more agreeable and salubrious
will be its influence. This desirable result is to be obtained only by
exposing the greatest quantity of heating surface to the least quantity
of fuel — a condition almost reversed in onr modern stoves.

^0

APPAEATUS OF WAKMING.

8. HOT-AIR ARRANGEMENTS.

124. Hot-air Furnaces. — Heating by Tiot air, as it is termed, has re-
cently come into very general use. In this case the heater is not situ-
ated in the apartments to he warmed ; hot air being conveyed from it
through air-flues to the rooms (fig. 19). The most common plan is a

hot-air furnace. It is construct-
^^' ' ed of iron, and usually lined with

fire-brick for burning anthracite,
and has a flue connecting it with
the chimney, to remove smoke.
It is enclosed in a case of iron or
brick- work, with an interval of
space between, forming an air-
chamber. Air is introduced into
this chamber, either directly
from the room, or by means
of a conduit, from without
the buUding. The furnace is
situated in the cellar or base-
ment, and the entering air heat-
ed to the required temperature,
by contact with the hot iron,
escapes upward from the air-
chamber through tin tubes,
which distribute it to aU parts
of the dwelling. It enters the
room through apertures called
registers, which may be opened
or closed at pleasure. This
method is commended by its
economy of space, the heating
machine being excluded from
the occupied apartments ; fuel
is also consumed more completely, and with better economy, in a
single furnace, than if burned in several stoves or grates. A disad-
vantage however, is, that the power of the furnace being gauged by
the requirements of a certain sized building, or number of apartments,
it is not easily accommodated to a fluctuating demand for heat.

125. DUTosiou of Hot Air tlirongh tlie Apartmcut.— There are serious

Manner of warming by Hot- Air Furnaces.

DISTEIBtrnON OF HEAT IN THE AIR OF ROOMS. '71

disadvantages attending the entrance of hot air in large streams
through registers in the floor. If it be very hot, it will ascend directly
to the ceiling, without imparting its heat to bodies around. In a
church, heated by two large hot-air stoves, delivering the air through
two large openings in the floor, we have found a difference, after the
heating process has been going on three hours, of more than 20° be-
tween the temperature near the ceiling and that of the floor. In some
public buildings, a stratum of air has been observed at the height of
20 or 30 feet from the floor, with a temperature above that of boihng
water, while below it has been disagreeably cool. In private houses,
with the hot-air furnaces, now in general use, air is usually introduced
at a high temperature. It rises directly to the ceiling, spreads out
upon it, and on reaching the walls, descends by them and the windows,
more rapidly by the latter (337), until it reaches the floor, along which
it is diflFased toward the register, when a part is again drawn into the
ascending current. Hence wo see that those assembling just around
the register, and not over it, are in the coldest part of the room.
That this is the case, we have also proved by the thermometer ; while
the air, midway between the floor and ceiling, in a moderate-sized
sitting-room, was at 74°, that near the register, was but 68°. — ("Wy-
MAN.) Even in a room heated by a stove, or any other apparatus
placed within it, and upon the floor, the air is found, after a time, to
arrange itself in horizontal layers, the temperatures of which decrease
from above downwards. In an experiment to ascertain the temper-
ature in a room 21 feet high, the following indications were obtained.

Level of floor, 65° 10. 5 80"

2. 1 foot, 6T° 12. 6 81°

4 2 " TO* 14. 7 86°

6. 3 " T2° 16. 8 90°

8.4 " 75° 19 94°

126. How we are wanned in Hot-air Rooms. — "We are to remember
that after all, it is less the contact of heated air which warms us in hot-
air apartments, than other agencies. We may enter a room in which
the atmosphere is at 70°, or even higher, and yet be chilly. Great
amounts of air contain but httle heat. The quantity of heat that will
raise 1 cubic foot of water 1 degree, would be so diffused as to raise 2,850
cubic feet of air one degree. — (Ajsnott.) From the amount of air that
comes in contact with our bodies, therefore, we cannot get suflacient
heat to warm us rapidly. If the walls, floors, and furniture of the
room are cold, though the air be warm, the individual radiates heat
to them, and is compensated by none in return ; while if they are

12

APPAEATUS OP "WARMING.

■warm, they become constant sources of radiant warmth. Hot air may
also become a direct source of cold if it be dry. K we moisten the
bulb of a thermometer, and expose it to the rays of a fire, it receives
the heat and rises ; but when moistened and exposed to the action of
warm, dry air, it will sink down several degrees, caused by the evap-
oration which carries off heat. In the same manner, over-dry air may
promote cooling by increasing bodily evaporation. "We shall refer to
the effects of hot air again.

127. Heating by Hot Water.— We have seen how water is put in
motion by heat ; the accompanying figure shows the working of the

Fig. 20. principle. As the lamp heats the water on one side

of the tube, it expands and ascends, the colder
water coming forward from below to take its place,
which establishes a circulation. As the hot water
passes round the circuit, it gradually parts with its
heat through the tube to the surrounding air. The
great specific heat of water (49) by which it holds a
large quantity of caloric, adapts it weU for the
transportation of this agent ; and, as it parts with
its large portion of heat but slowly, it is the most
constant and equable of all sources of warmth. We
have already referred to the significant fact that
when the heat of a cubic foot of water is imparted
to air, whatever be the number of degrees through
Circulation of water. ^i^[q]^ the water falls, it will raise through the
same number of degrees 2,850 cubic feet of air.

128. Two forms of Hot Water apparatus. — There are two methods of
warming houses by hot water. In one the mechanism is placed in
the cellar or basement, and heats air which is conveyed upward to
warm the apartments above, as in the case of furnaces. In this form
of the mechanism, the pipes do not ascend to any considerable height
above the boiler ; but, in the other plan, a system of small tubes is
distributed through the house, being laid along to fit any form and
succession of rooms and passages, or they are coiled into heaps in
various situations, and impart their heat by direct radiation. There
is a difference in the degi'ee of heat in these two plans. Water
exj)osed to fire, as we have seen, rises in temperature to the boiling
point and goes no higher, but this varies with depth and pressure.
In those arrangements, therefore, which are confined below, the water
hardly rises above the temperature of 212° ; while, in those which
extend through the dwelling, it ascends many degrees higher. A

STEAM-HEAT — ^DAITGEE OF FIEB. 73

good hot-water arrangement, from its constancy and regularity of
action, and when not heated above 200° or 212°, affords one of the
most agreeable modes of heating a dwelling, although it is at present
80 expensive as to place it beyond popular reach.

129. Steam Apparatas for Warming. — As steam contains a large
amount of heat (68), it becomes an available means of its transmission.
If admitted into any vessel not so hot as itself, it is rapidly condensed,
and at the same time gives its heat to the vessel, which may then
diffuse it in the space around. A system of tubes ascending from a
hoUer may be so arranged as to warm the air which is thrown into
the room through a register, or they may be wound into coils as in
the previous case (128), and dispense their heat by radiation. The
pipes are so placed, that the water from the condensed steam flows
back to the boiler, or the hot water may be drawn off into vessels
which are made to contribute to the heating effect. This mode of
heating requires a temperature always at 212° for the formation of
steam, and often much higher to drive forward the condensed water
and clear the pipes. A serious drawback to this mode of heating is
that the apparatus often emits a disagreeable rattling or clacking
sound, owing to the condensation within the pipes and the sudden
movements of steam and water. There is also a fundamental objec-
tion to the method of warming rooms by heat radiated from coils of
pipes, whether they be heated by steam or hot water. In respect of
the condition of the air, this is the worst of all methods of heating,
for it makes no provision whatever for exchange of air. All the
other heating arrangements involve more or less necessary ventilation,
but radiating pipes afford none at all.

130. Risk of Fire by these methods of Warming.— It has been supposed
that the employment of hot water, hot air, and steam pipes, as a
means of heating buildings, cuts off the common sources of danger
from fires, and is entirely safe. This is a serious error. Iron pipes
liable to be heated to 400°, are often placed in close contact with
floors skirting boards and wooden supports, which a much lower
degree of heat may suffice to ignite. By the long-continued applica-
tion of heat, not much above that of boiling water, wood becomes so
baked and charred that it may take fire without the application of a
light. A considerable time may be required to produce this change,
BO that a fire may actually be " hindling upon a mail's premises for
years," The circular rim supporting a still which was used in the
preparation of some medicament that required a temperature of only
300°, was found to have charred a circle at least a quarter of an inch

4

14: APPARATUS OF WAEMIN-G.

deep in the wood beneath it in less than six months. There are nu-
merous cases of buildings fired by these forms of heating apparatus.

131. Origin of Fires. — The Secretary of a London Fire Insurance
office stated that the introduction of lucifer matches caused them an
annual loss of $50,000. Of 127 fires caused by matches, 80 were
produced by their going off" from heat ; children playing with them,
45 ; rat gnawing matches, 1 ; jackdaw playing with them, 1. "Wax
matches are run away with by rats and mice, taken into their holes
and ignited by gnawing. These facts point to the indispensableness
of match-safes. In London, during a period of nine years, the pro-
portion of fires regularly increased from 1.96, at 9 o'clock, A. M., the
time at which all households might be considered to be about, to 3.44
at 1 o'clock, P. M ; 3.55 at 5 P. M., and 8.15 at 10 P. M., which is just
at the time that fires are left to themselves.

132. Benefits and Drawbacks of tlie various methods of Heating. — Each
plan of warming presents its special claims to attention, and vaunts its
peculiar benefits. Modifications of every scheme are numerous, and
stiU multiplying. As a result of this inventive activity, there is a
gradual but certain improvement. The aim of inventors has hitherto
been mainly to secure economical results ; a laudable purpose, if not
pursued at the sacrifice of health. As people generally become
better informed respecting the principles and laws which influence the
comfort and well-beiag of daily life, improvements will be demanded
in this direction also. Meantime, each method is to be accepted with
its imperfections, though we are not to forget that in their working
results much must depend upon proper and judicious management.
We recapitulate and contrast the chief advantages and disadvantages
of the various methods of heating. Some of the points referred to,
particularly those which relate to ventilation, have not been previ-
ously noticed, and will be considered when speaking of air.

ADVANTAGES OF OPEN FIEE-PLACES. DISADVANTAGES OF OPEN FIRE-PLACES.

They promote ventilation — afford a They are uncleanly — ^require frequent

cheerful fireside iniJnence — warm objects, attention — are not economical — are apt to

without disturbing the condition of the air strain the eyes — heat apartments unequally

— and may furnish warm air from without — are liable to smoke.

ADVANTAGES OF STOVES. DISADVANTAGES OF STOVES.

They cost but little — are portable — are They afford no ventilation — if not of

quickly heated— and consume fuel eco- heavy metal-plates, they quickly lose thoir
nomically heat — ^yield fluctuating temperatures — are

liable to overheat the air — are liable to
leakage of gases— and are not cleanly.

HOT-WATEE APPARATUS. ^5

ADVANTAGES OF HOT-AIR DISADVANTAGES OF HOT-AIR

FURNACES. FURNACES.

They are out of the way and save space They are liable to scorch the air— cannot

— are cleanly — giye but little trouble — may be easily adapted to heat more or less space

afford abundant ventilation — need waste — are liable to leakage of foul gases — and

but little heat — and warm the whole house, they dry and parch the air if copious moist-
ure is not supplied.

ADVANTAGES OF HOT-WATER DISADVANTAGES OF HOT-WATER

APPARATUS. APPARATUS.

They do not burn or scorch the air — They aro expensive in first cost — if
give excellent ventilation — do not waste adapted for an average range of tempera-
heat — and they warm the whole house, ture, they may fail in extreme cold weather
These remarks do not apply to those which (as may also furnaces) — and may give a dry
heat rooms by radiation from coils of pipe and parched air if moisture be not supplied.
(129).

PART SECOND

LIGHT.

I. NATURE OF LIGHT— LAW OF ITS DIFFUSION.

132. How the oatward and inward Worlds Commonicate. — We sit at

the window, and have report of the world without. That intelligent
consciousness which has residence in the chambers of the brain, holds
intimate communion with the external universe, by means of a com-
pound system of telegraphing and daguerreotyping, as much superior
in perfection to the devices of art, as the works of the Most High
transcend the achievements of man. We lift the curtains of vision,
and a thousand objects, at a thousand distances, of numberless forms
and clad in all the colors of beauty, are instantaneously signalled to
the conscious agent within. Each point of all visible surfaces darts
tidings of its existence and place, so that millions upon millions of de-
spatches which no man can number, enter the eye each moment. A
landscape of many square leagues sends the mysterious emanation,
which, entering the camera-box of the eye, daguerreotypes itself upon
the retina vrith the fidelity of the Infinite. Fresh chemicals are
brought every instant, by the little arteries, to preserve the sensitive-
ness of the nerve-plate, while those that have been used and spent,
are promptly conveyed away by the veins. As impressions are thus
continuously formed, they are transmitted, jjerhaps by a true electric
agency, along the line of the optic nerve, to be registered in the brain,
and placed in charge of memory. By the magic play of these
wonderful agents and mechanisms, the world without is translated
within, and the thinking and knowing faculty is brought, as it were,
into immediate contact with the boundless universe. Let us inquire
further then, into the nature and properties of this luminous principle,
and how we are related to, and aifected by it.

133. Exhilarating Agency of Light. — Light is a stimulus to the ner-
vous system, and through that, exerts an influence in awakening and

OLDEE NOTIONS OP ITS NATUKE. ^'J

quickening tlie mind. The nerves of sense, the brain and intel-
lect, have their periods of repose and action. The withdrawal of
light from the theatre of eifort is the most favorable condition, as well
as the general signal, for rest ; while its reappearance stirs us again
to activity. There is something ia darkness soothing, depressing,
quieting ; while hght, on the contrary, excites and arouses. It is com-
mon to see this illustrated socially ; — a company assembled in an apart-
ment dimly lighted, will be dull, somnolent and stupid ; but let the
room be brightly illuminated, and the spirits rise, thought is enlivened,
and conversation proceeds with increased animation. " Most delicate
and mysterious is the relation which our bodies bear to the passing
light! How our feelings, and even our appearance change with every
change of the sky ! "When the sun shiaes, the blood flows freely, and
the spirits are hght and buoyant. "When gloom overspreads the heav-
ens, dulness and sober thoughts possess the mind. The energy is
greater, the body is actually stronger, in the bright light of day, while
the health is manifestly promoted, digestion hastened, and the color
made to play on the cheek, when the rays of sunshine are allowed
freely to sport around us."

134. Ancient Conceptions of Light.— Light is that agent which reveals
the external world to the sense of sight. The ancients believed it to
be something born with us — an attribute or appendage of the eye.
They thought that the rays of light were set into the organ of vision,
and reached or extended away from it, so that we see in the same man-
ner as a cat feels by the whiskers which grow upon its face, — ^by a
kind of touching or feeling process.

135. Newton's View of its Nature.— Modern science regards light as
an agent, or force, originating in luminous bodies, and flowing away
from them constantly and with great rapidity, in all directions. But
how ? The human mind is never satisfied with the mere appearances
of things. It demands a deeper insight into their nature, — an explana-
tion of their causes. The first scientific attempt to explain the nature
of light, and the cause of vision, likened the sense of sight to that
of smell. We know that to excite the sensation of smell, material
particles, emanating from the odorous body, pass through the air and
are brought into contact with the olfactory nerve of the nose. It was
supposed that light affects the eye as odors do the nose ; that it con-
sists of particles of amazing minuteness, which are shot from the lu-
minous source, and entering the eye, strike directly upon the optic
nerve, and thus awaken vision. This was the view of Newton, but
it is now considered untenable and is generally rejected. It is at pres-

HOW LIGHT IS DIPFUSKD.

ent thought that light is motion rather than matter, and that the eye
is influenced by a mode of action resembling that of the ear rather
than that of the nose. We omit further reference to this question
here, as the analogy wiU be more fuUy traced when we come to speak
of colors (150).

136. Light loses Intensity as it is Diffased. — The rays of light proceed-
ing from any source, a candle for example, spread out or diverge, as we
notice nightly. As light thus diffuses from its source, the same quan-
tity occupies more and more space, and it becomes rapidly weaker or
less intense. This takes place at a regular rate. Its power decreases
from each point of emission, in the same proportion that the space
through which it is diifused increases, exactly as occurs in the case of
radiant heat ; and this is as the square of the distance. The light
which at one foot from a candle occupies a given space, and has a
given intensity, at two feet is diffused through four times the space,
and has but one fourth the intensity ; at three feet it spreads through
nine times the space, and therefore has but one-ninth the intensity ;
following the law of radiant heat, as is shown in Fig. 21. If we are
reading at a distance of three feet from a lamp, by removing the book
one foot nearer to it, more than double the quantity of light wiU fall
Fi<^- 21. upon the page ; and if we carry

it a foot closer, we shall have
nine times the amount of light
to read by that we did at firpt.
This effect, however, may be
modified by the light reflected
back from the walls, and which
is always more, the whiter they
are. Whitewashed walls and
light-colored paper economize
light, or give it greater effect
than dark walls, which absorb or waste it.

137. How Bodies receive the Luminous Principle. — When light falls
upon various kinds of matter, they behave toward it very differently.
Some throw it back {reflection) ; some let it pass through them {trans-
mission) ; some swallow it up or extinguish it {absorption) ; and some,
as it were, split it to pieces {decomposition). All bodies, according to
their nature and properties, affect light in one or more of these modes,
producing that infinite variety of appearances which the universe
presents to the" eye.

ITS EBLATION TO SUEPACES.

79

Reiliettnr

II, EEFLECTION OP LIGHT.

138. Those bodies which will not allow the light to pass through
them, are called opaque. When the rays of light strike an opaque
body, a portion of them, according to the quahty of the surface, is
absorbed, and the remainder are thrown back into the medium through
which they came. This recoil, or return of the rays, is called reflec-
tion of light.

139. The Law of Reflected Light.— "When a ray of light strikes per-
pendicularly, or at right angles, upon a reflecting surface, it is thrown
back in exactly the same path or line. If a &, Fig. 22, be a ray of
light falling perpendicularly upon a reflecting Fig. 22.
surface, it will be thrown back in the same
direction 5 a. But if the ray fall upon such
a surface in a slanting or oblique manner, it
glances off or is reflected, at exactly the same
angle, as shown by the arrows. The angle
of rebound is equal to the angle of striking ; *

or, as it ia commonly said, — the angle op eefleotion is equal to

THE AiraLB OF rNCrDEITOE, THE EEFLEOTED EAT IS ON THE OPPOSITE
SIDE OF THE PEEPENDICTJLAE, AND THE PEEPENDICULAE, THE INCIDENT
AND THE EEFLEOTED EATS AEE ALL IN THE SAME PLANE, Place a

looking-glass upon a table, in a dark room. Let a ray of light,
entering through a hole in a window shutter, strike upon its re-
flecting surface, it will be thrown off at an equal angle, and both the
incident and reflected rays wiU be made visible by the particles of dust
floating in the room.

140. How Reflected Light is scattered.— Parallel rays fallmg upon a
plane eurface, are reflected parallel, as shown in Fig. 23 ; but sepa-
rating rays falling upon such a surface are reflected divergently, or
scattered. The beams of light from a candle Fig. 24 diverge before
falling upon a mirror ; and as each single ray makes
the angle of incidence equal to that of reflection, it
is clear that the rays must continue to diverge when
they are reflected, as in the dotted lines in the
figure. Thus when a burning candle is placed before a looking-glass,
its diverging rays strike the mirror surface, and being reflected in
divergent lines, are dispersed through the room.

141. The Image in the Looking-glass.— A highly polished metallic
smface, called a speculum^ is the most perfect reflector. Mirrors,
or looking-glasses, consist of glass plates coated with metal. It is

Fig. 23.

80

PEODUCTION OF IMAGES.

Fig. 24.

Fia. 25.

not the glass, in looking-glasses, that reflects the light, hnt the
metallic coating behind it. K we place any illuminated object before
a plane mirror, rays of light pass from all points of
its sm-face, and convey an image of it to the mirror.
But the polished surface does not retain the image ;
it reflects or throws it back, so that the eye per-
ceives it. The light which enters the eye comes
from the real object, which appears behind the
glass, because the angle or bend in the ray is not
recognized. The light from an object may be re-
flected many times, and make a great number of short
turns, but it will seem as if the rays came straight
from the object, and it wUl always appear in the
direction in which the last reflection comes to the
eye. This will cause the image to appear as far
behind the glass as the object is before it, as
the accompanying diagram (Fig. 25) shows. A
perfectly plane surface reflects ob-
jects in their natural sizes and propor-
tions ; but if the form of the reflecting
surface be altered, made hollow {con-
cave)^ or rounded {convex)^ they cause
the image to appear larger or smaller
than the objects ; or the image is dis-
torted in various ways, according to
the figure of the surface. "We see this
linaje constantly illustrated in the images of
the face, formed by the bright metallic
looking-glass. surfaces of domestic utensils.

142. A perfect Reflecting Surface would be luvisible.— If the surface
of an opaque body could be perfectly polished, it would perfectly
reflect all objects placed before it, so that the images would appear as
bright as the realities; but, in such a case, the reflecting surface
would be itself invisihle, and an observer looking at it could see
nothing but reflected images. If a large looking-glass, with such a
surface, were placed at the side of a room, it would look like an
opening into another room precisely similar, and an observer would
be prevented from attempting to walk through such an apparent
opening, by meeting his image as he approached it. If the surfaces
of all bodies had this property of reflecting light, they would be
invisible, and nothing could be seen but the hghts, or sources of illumi-

Chjhri:

How the image appears behind the

TWO KESTDS OF REFLECTED LIGHT. 81

nation, and their multiplied images. Upon the earth's surface nothing
would be visible but the reflected images of the sun and stars, and in
a room, nothing except the spectres of the artificial lights, thrown
back by one universal looking-glass. But perfect polish is impossible ;
there are no surfaces which in this manner reflect all the light.

143. Itt what manner Light makes objects Visible. — It is by reflected
light that nearly every object is seen, No surfaces are perfectly flat ;
they may appear so, but, when closely examined, they are found to
consist of an infinite number of minute planes, inclined to each other
at all possible angles, and therefore, receiving and reflecting the light
in aU possible directions. K a ray is let into a dark room, and falls
upon a bright metallic surface, a brilliant spot of light will be seen
from certain points, but the reflecting surface will be almost invisible
in other directions, and the room will remain dark. If, now, a sheet
of white paper be substituted for the mirror, it can be seen in all
directions, and will slightly illuminate the apartment. The surface
of the paper scatters the light every way, producing an irregular
reflection. It is this scattered and diffused light which makes the
surfaces of objects visible. Thus light irregularly reflected exhibits to
us real objects^ while light regularly reflected discloses only semblances
and images. "We see the image in a looking-glass, by light regularly
reflected ; we see the surface of the glass itself, by the light scattered
by the minute inequalities of its surface. This irregularly reflected
light diverges from each point of every visible surface in all direc-
tions, so that the object may be seen from whatever point of view we
look at it, provided other light does not interfere (144). It followa
the law of radiation, that is, it flows from each point as a focus, but
it does not conform to the principle of regular reflection, which has
just been noticed. The direction of the reflected rays is independent
of each of tJie incident rays. In this manner light is radiated from
surface to surface, so that in the immediate absence of any original
luminous fountain, there is a reverberation of light from object to
object, through an endless series of reflections, so that we hav"^
general and equal illumination.

144. Management of Light in hanging Pictures. — ^The foregoing prin-
ciples are variously applicable ; hanging pictures upon the walls of
rooms may be taken as an illustration. As it is irregularly reflected
light that reveals to us the picture, it should be so placed that from
the most natural point of observation that light reaches the eye, and
not regularly reflected light. If the light fall upon a picture from a
window on one side of it, and we stand upon the other side, as at & (Fig.

4*

BELATION OP PICTUKES TO LIGHT.

Pio.26.

Windov/

Fia. 27.

26), the eje is filled witli the glare of the regularly
reflected light, while the picture itself can hardly
be seen. In such a case, the true position of the
observer is perpendicular to the plane of the picture,
as at a in the figure. As pictures are often sus-
pended higher than the eye, they require to be
inclined forward, and the degree of their inclination
should depend upon their height and the distance
of the point at which they may be best observed.
They should be inclined until the line of vision is
perpendicular to the vertical plane of the picture. "With the eye at a
and the picture at l (Fig. 27), its proper inclination would be to c ;

but if it were elevated to <Z, it should
fall forward to e. "We will farther re-
mark that pictures should be placed as
nearly as possible in the same relation
to light as when they were painted;
that is, if the shadows fall to the right,
the illumination should come from the
left to produce harmonious effects.

145. Light scattered by the Atmosphere.
— ^By this kind of irregular reflection,
the atmosphere diffuses and disperses
the light, — each particle of air acting as
a luminous centre, radiates light in every
direction. If it were not for this, the sun's light would only enter
those spaces which are directly open to his rays, so that, shining
through the window of an apartment, that portion only where the
beams passed would be enlightened, and the rest of the room would
remain totally dark. This secondary radiation occasions the mild and
softened light which we experience when the heavens are screened
with clouds, instead of the intense and often painful glare of a cloud-
less summer day. In the same manner the atmospheric particles
scatter the rays and diffuse a subdued illumination at morning and
evening twilight, while the sun is below the horizon.

III.— TRANSMISSION AND REFRACTION OF LIGHT.

146. When light falls upon transparent objects, as air, water, glass,
it passes through or is said to be transmitted. Bodies vary greatly
in this power of passing the light, or transparency. The metals are
least transparent, or most opaque, yet they are not entirelv so ; thin

LIGHT BEFEACTED OK BEOKEN.

83

gold leaf, for example, transmits a greerdsli light. Nor are there any
bodies which transmit all the light ; the most transparent detain or
absorb a part of it. A considerable portion of the sun's light is ab-
sorbed in the atmosphere ; it does not reach the earth ; and it has
been calculated that if the atmospheric ocean were TOO miles deep, the
solar light would not pass through it, and the earth would be in dark-
ness. The purest water of a depth of seven feet, absorbs one half the
light which falls upon it, and of 700 feet depth, extinguishes it.

147. Fracture or Refraction of the Rays. — "When light passes from
one substance to another of a different density, as from air to water,
it is liable to be turned out of its straight course. If it pass from one
medium to another in a line perpendicular to its surface, as a & (Fig.

28), it will not be diverted ; but if it fall at an angle,
as at c d^ it wUl not continue straight to (Z, but will be
as it were broken or refracted and proceed to c. If
[ the refracting medium have parallel surfaces, the ray
on leaving it is again bent back to its original course,
as is shown in the figure. For this reason common
window panes, which consist of plates of glass with
parallel surfaces, unless they contain flaws, produce no
distortion in the appearance of the objects seen through them. When
light passes obliquely from a rarer to a denser medium, as from air to
water, it is turned toward a perpendicular ; when from a denser to a
rarer medium, as from water or glass to air, it is turned /rom a per-
pendicular, as shown in Fig. 28.

148. How Refractiou may be shown. — A stick, with half its length
placed obliquely in water, appears bent at the surface ; this is because
the rays are bent, so that those which come from that portion of the
stick which is in the water, show it in a false place. Put a coin in
any opaque dish upon a table, and step back, until the edge of the
vessel just hides it from view. Now, if water be carefully poured in,
without disturbing its position, the coin will become visible (Fig. 29) ;

the rays of light coming from it, which before
passed above the eyes of the observer, are
now, as they come into the air, bent down-
ward/rom the perpendicular. Bodies possess
different degrees of refractive power. When
we look through a mass of water, as in a pond
or stream, the rays are so altered that it
appears only thi'ee-quarters as deep as it really
is. Cases of drowning have happened through ignorance of this

Fig. 20.

84

WAVE THEOET OF LIGHT.

Fig. so.

Fis. Si.

illusion. The degree to whicli any substance bends the light from its
straight course is called its index of refraction. Each transparent
body has its refracting index, which is one of the properties by which
it may be known.

149. Effect of Lenses upon Light.— This power which bodies have, of
bending hght from its straight course,
is employed when we desire to gather
it to a point or focus, or to concentrate
it ; or when it is wished to disperse and
difiuse it. Pieces of glass, cut or ground
into various shapes, are commonly used
for this purpose, and are called lenses-
A plane convex lens (Fig. 30), or a
double convex lens (Fig. 31), collect
the rays of light; while a plane-con-
cave lens (Fig. 32), or a double-concave
lens (Fig. 33), separate them, or spread
them out into a greater space. Com-
mon spectacle glasses are examples of
these forms of lenses (248).

Double-convex
Lens.

Fig. 33.

Plane-concave
Lens.

Double-concave
Lens.

IV. THEORY OF LIGHT— WAVE MOVEMENTS IN NATURE.

150. Light not Matter but Motion. — Thus far we have considered light
as if it were simple, without inquiring if it be reaUy so, or compounded
of difierent elements. There is another way in which the objects of
nature receive and dispose of it, which brings us to the question of
composition, and the subject of color. But what is color ? and what
is light, in nature and essence ? Or what opinion has been formed of it,
by those who have thought upon the subject most deeply? In its
cause and mode of movement, light is believed to resemble sound ;
it is propagated, not by moving particles of matter, but by impulses
of motion, wliich progress unaccompanied by any material substances.
Let us note how wave-motions take place, and the known extent of
theu' occurrence in nature.

151. Visible Ware Motions in Nature. — If we fasten one end of a cord,
and holding the other strained tight, move the hand sharply up and
down, or from side to side, icares will be formed, wliich proceed along
the string. The real motion, in this case, is at riglit angles to the di-
rection of the string, the apparent motion is forward. The particles

SOUND PRODUCED BY AIE-WAVES. 85

composing the cord make excursions right and left, or up and down,
■which gives rise to forward wave-impulses. All have noticed what
takes place in a field of grain when the wind blows. A succession of
waves appear to pass over the field ; but it is not the grain that moves
along over the ground ; every staUc keeps its place, and only bows its
head. Yet wave-motions are seen to flow successively forward. If
we toss a stone into perfectly still water, the surface wiU be thrown
into agitation, and waves will pass rapidly from the point where it
struck, outward, in all directions. The water in this case does not
move forward any more than the grain did. This is proved by the
circumstance that any objects which may be seen floating upon the
water are not carried along by the advancing waves, but only move
up and down in their places. Thus, particles of water, moving verti-
cally, cause wave-motions to travel horizontally.

152. Sound the result of Waves in the Air. — Air is the medium which
conveys sound to the ear. If a bell be rung in a vacuum, we cannot
hear it. The air in some way transmits or convoys the sound from
point to point. How is it done ? There is no passage of air-particles,
no current or breeze moving from the sounding body to the ear ; the
atmospheric medium is thrown into vibratory motion, and it is air-
waves only which move forward. We all know that sonorous bodies
vibrate when struck, and that sound results. A harp-string, when
struck by the fingers, swings rapidly backward and forward for a
certain time, producing a sound as long as the vibration lasts. A
piece of steel wire, or a pin held between the teeth, utters a sound
as often as the free end is inflected. By touching the teeth with the
prongs of an excited tuning-fork, we can feel the vibrations. Sound
is thus not only motion, but it is moratory motion, and its transmission
to the ear is due to the flight of air-waves, which, striking against the
auditory drum, communicate sensations of sound to the brain through
the auditory nerve.

153. Upon what the diflferences of Sound depend. — If sounds are thus
caused by vibrations, it would seem that the quality of sound should
depend upon the quality of the vibrations ; which is the fact. The
first distinction among sounds is into high and low, or acute and
grave ; it is a difierence of pitch. Slow vibrations produce grav'_>
sounds of a low pitch. In the case of strings, for example, the larger
they are the heavier they are, and the looser they are the slower are
their vibrations, and the deeper are their sounds; while, on the other
hand, the shorter, lighter, and tighter they are the quicker are their
vibrations, and the higher and sharper the sounds they give. Each

^6 WAVE-THEOET OP LIGHT.

sound, therefore, that can be made, is the result of a certain numher
of air vibrations, and to that pitch of sound always belongs that num-
ber. Sataet contrived a machine by which the number of pulsations
which belong to each tone has been determined by actual experiment.
A thin plate of metal was struck by each tooth of a revolving cogged
wheel, the motion of which was easily measured. In this way he de-
termined the exact number of vibrations in the tones forming the
usual musical scale.

154. Harmonic Ratios of the Musical Scale.-- It was found, experimen-
tally, that the orchestra pitch note A, of the treble cleff, is produced
by 853 vibrations per second. The number of pulsations in each note
of the octave is as follows :

Katio of Haemonio Sounds.
^ 0 D E F q A B I c I

^^^^1^^

No. of Vibrations 512, 576, 640, 682, 768, 853, 960 1024,

Intervals 64, 64, 42, 86, 85, 107, 64.

It will be seen that in the highest note of this scale there are just
twice as many vibrations as in the lowest ; the interval which they
comprise is called an octave. The difference between the number of
pulsations in any note, and the same note in the octave above, is as 1 to 2.
Hence, by halving the numbers of any scale we obtain the numerical
value of the octave below; while by doubling them we have the
number of vibrations made by the notes in the scale above. The
lowest note of a seven octave piano is made by 32 vibrations in a sec-
ond, and the highest by 7,680. Two tones having exactly the same
number of vibrations are said to be in unison. When their numbers
are not the same, but are in some simple relation, a concord is pro-
duced. If one has twice as many as the other an octave results, which
is the most pleasing of all concords. The simpler the numerical ratio
between the vibrations which generate a sound, or the air-waves
which reach the ear, the more perfect and sweet the concord. When
the difference is such that the proportion cannot readily be recognized
by the ear, discord is the result. The whole phenomena of music thus
resolve themselves into certain harmonious numerical ratios among
air-waves, by which impressions are produced in a certain exact order,
upon a mathematically constituted organ — the brain.

SCALE OF THE LUMINOUS VIBBATIONS. 87

155. Light and Colors result from Wave Motion. — As all sound and
music are thus due to measured wave movements in the air, it is
thought also that light has a similar origin. This view assumes, that
throughout the universe there exists a subtle, aU-pervading and in-
finitely elastic ether^ and that vision is the result of vibrations or wave
movements sent thraugh this ether, from the source of light to the
nerve of the eye ; and as different musical sounds are produced by
varying rates of vibration in the air, so it is suspected that different
colors are due to the different rates of vibration in the luminous ether,
and philosophers have gone so far as even to measure the wave-lengths
of the different elements of light. By wave-length is meant the dis-
tance from the top or crest of one wave to that of the next ; and it
is inferred from certain interesting experiments made by Newton, that
the length of waves, although exceedingly small, differs in the different
colors, red being largest and violet smallest. In an inch length of a
ray of red light there are 37,640 vibrations; in an inch of yeUow
light, 44,000; and in an inch of the violet ray, 59,756. K the minute-
ness of the wave excite surprise, it may be replied that this is by no
means the strongest illustration of the smallness of the scale upon
which nature's works are often constructed. Indeed, in this case it
has been even outstripped by art. M. IsTobeet, of France, has ruled
lines upon glass, for microscopical test-purposes, but the -.j-xsto <^f ^^
inch apart.*

156. Vibrations per second of the Inminons Ether. — But the demon-
strations of science carry us into far profounder regions of wonder.
The speed of light has been measured ; the velocity with which it
moves is in round numbers 200,000 miles per second. That is, when
we look at any thing, an agent or force sent from the illuminated body
streams into the eye at the rate of 200,000 mUes in a second. Know-
ing the rate at which light moves, and the number of waves in an
inch for any particular color, it is easy to ascertain the number of
vibrations made by each in a second. In two hundred thousand mUes
there are a thousand millions of feet, and, therefore, twelve thousand
millions of inches. In each of these inches there are forty thousand
waves of red light. In the whole length of the red ray, therefore,
there are four hundred and eighty millions of millions of waves.
Now as this ray enters the eye in one second, and the retina
pulsates once for each of these waves, we arrive at the astonishing
conclusion, that where we behold a red object the membrane of the
eye trembles at the rate of four hundred and eighty millions of mil-
lions of times between every two ticks of a common clock. Of yellow

* See Appendix B.

88 COMPOSITION AND MUTUAL INFLUENCE OF COLOES.

light five hundred and thirty-five millions of millions of waves enter
the eye, and beat against the nerve of vision in the sixtieth part of a
minute ; "if a single second of time he divided into a million of equal
parts, a vrave of violet light trembles or pulsates in that inconceivably
short interval seven hundred and twenty-seven millions of times."
"Vision is undoubtedly the result of something done within the eye,
the effect of an active external agent, and the reaction of the mechan-
ism ; the chemical constituents of nervous matter, — perhaps the atoms
of carbon or phosphorus are in some way changed or influenced by
nerve impulses in infinitely rapid succession, the sensations of vision
and color being the consequence. If it be objected that the foregoing
statements are incredible, we reply that they are generally accepted
by the most sober and cautious scientific thinkers. But they are really
no more strange or impossible than many other of the miracles of being
which science is constantly unfolding around us. We should observe
a due modesty in criticising and assigning limits to the wonders and
perfections of God's works. Dismissing the more purely theoretic or
explanatory aspect of the subject, we now proceed to notice those
properties and relations of colors which are the result of actual ex-
amination.

v.— COMPOSITION AND MUTUAL mFLUENCE OF COLOES.

157. White Light taken to pieces. — If a ray of common white light

be admitted, through a small aperture, into a dark room, and be made

to strike upon a triangular piece

of glass (j>rism)^ the white ray

disappears ; it is turned from its

course, and there falls upon the

opposite wall an oblong colored

image called the solar spectrum.

It consists of seven bright colors,

always found in a certain order,

a 4.- e v<- r 1,+ • + -NT r 1 ^s showu in Fig. 34: but they

Separation of white ii^at into Newton s seven ° ' •'

prismatic colors. pass into each other gradually, so

that it is difficult to tell where one ceases and another begins. New-
ton assumed, as the result of this experiment, that white light is, a
compound principle, consisting of these seven colors, which he called
primary, and taught that all other colors whatever are the result of
various commixtures of these. For convenience of representing the
relations of colors, we may represent white light by a circle, and the

NTTMBEE OF PEIMAKIES.

89

Fia. 35.

colors wliicli compose it by divisions of the enclosed space. In that
case the seven primaries of Newtox will be shown as in Fig. 35.

158. Newton's explanation of Colored Surfaces.
— White light falls upon objects, and thej ap-

)ear colored : how is this ? Newton replied :
oodles have not only the power of reflecting
and transmitting light, but they can also de-
compose and absorb it. A body appears
white because it reflects back to the eye the
white light that falls upon it, unaltered. When
white light falls upon a surface and it appears
'blacky it is absorbed and lost in the substance,
and therefore does not return to make an impression upon the eye.
But the blackest surfaces do not really absorb all the light, for then
they would be invisible, and appear like dark cavities, presenting no
surface. If the surface appears colored, it is because the white light
is split up, or decomposed, one part being absorbed and lost, whUe
the other is reflected to the eye, so that the object appears of the re-
flected color. For example, grass absorbs all colors but green, which
it reflects to the eye ; and in the same way the sky absorbs all but
blue, and reflects that to the eye. Difierent surfaces reflect the pri-
mary colors mixed in aU manner of ways, and hence the endless
modifications of color that meet the eye.

159. Bttt three Primary ColorSt — A more simplified view of the com-
position of colors has been propounded by Sir D. Beewstee, and
generally received. He considers
that instead of seven, there are
but three elementary colors, red,
yellow, and blue, and that the
others are compounds of these.
We cannot produce red, yellow,
or blue, by the mixture of any
other colors ; but we can pro-
duce aU others by the various com-
binations of these three. Beews-
tee maintains, that even the colors
of the spectrum are not absolutely
pure, but that each of the three
exists throughout its whole extent, although greatly in excess at the
diflferent points where they are visible. Blue, yellow and red being
primaries, violet, indigo, green and orange are' secondaries derived

90

KELATION AND MUTUAL IISTFLUENCE OP COLOES.

FiQ. 8T.

from them. The separation of the impure or compound colors from
the spectrum, leaving the three from which
they are derived, is illustrated in Fig. 36.
Orange is derived from the mixture of red
and yellow ; green from yellow and blue ;
and indigo and violet from blue and red. So
that we have white hght at last composed
only of the three colors, as represented in
Fig. 37.

160. What are Complementary Colors. — The eflfect of a colored surface
is to decompose the white light which falls upon it, reflecting one
portion, and absorbing or extinguishing the rest. "We do not see any

colored surface, except
by the seperation of the
light which falls upon it
into two colored parts,
the one visible, the other
absorbed. Now it is evi-
dent that the rays ab-
sorbed, added to those
Avhich are reflected,make
up the ordinary light.
Hence, whatever be the color reflected, that which is not reflected,
and which is, therefore, wanting to complete the full set of colors which

form white, and make
out the full complement,
is called the com^ple-
mentar y colov. The part
absorbed, or which does
not appear, is the com-
plementary of the color
seen. This may be made
perfectly clear by the
circular diagram. If we
look, for example, upon a red surface supposed to be presented in
Fig. 38, yellow and blue are seen to be the colors necessary to com-
plete it to white ; they are therefore the complement of red ; but
yellow and blue form green, as shown in Fig. 39, which is therefore
the true complement of red, that which it lacks to make white. If we
look upon a yellow surface (Fig. 40), blue and red are deficient ; blue

Fig. 41.

A NEW SYSTEM OF AERANGnfG THEM. 91

and red produce violet, therefore violet is the complementary of yel-
low, as seen in Fig. 41. ^.^^ ^2. Fig. 43.
Again, we look upon
blue (Fig. 42) ; red aad
yellow are required to
complete the circle into
whiteness ; but red and
yellow make orange,
therefore orange is the
complement of blue, as
is shown in Fig. 43.

161. Tints and Shades, Tones and Scales. — These terms have formerly
been employed in the most loose and indefinite way ; they have, how-
ever, now acquired a kind of scientific precision. The tones of a color
are those aspects which it presents when altered from its maximum
of brightness or highest intensity, by mixing with it either white or
black : if we take the purest and brightest red as a standard, say car-
mine, and mingle various proportions of black with it, we of course
darken it and get deeper tones of red. If we mingle white with it,
we lighten it and get lighter tones of red. By the addition of black
the red is said to be shaded^ by the addition of white it is tinted.
Each color, in this case, is a tone of red, and the whole series of tones
constitute a scale — ^the red scale. It may consist of ten, twenty, or
fifty tones, according to the quantities of black and white successively
added. In the same manner we make tones of orange and get an
orange scale, tones of blue and get a blue scale, and so each color has
its scale, in which it moves in two directions, from its normal or
standard point, towards black and towards white.

162. Wliatare Hues? — ^A hue is the result of the movement of a
color, not in the direction of black or white, but of some other color
out of its scale. If a little blue be mingled with red so as to change
it slightly, the red still predominating, a hue of red is produced. So
if blue be tinged in a similar manner by any color, hues of blue re-
sult. In the same way are produced hues of orange, yellow, violet,
green, &g.

163. Chevreul's scheme for showing the relation of Colors. — A plan has
been suggested by M.. Cheveettl, of France, for representing the com-
position and relations of colors, in an extremely simple and effective
way. It clears the mist from the subject, and not only discloses it in
a beautiful order, but is very valuable for practical purposes. It is
represented by the diagram (Fig. 44). The outer circle represents

92

EELATION ANT> MUTUAIi INFLUENCE OF COLORS.

black, the centre white. The radial lines passing from the centre to
the circumference represent scales of color, each dot indicating a tone.
Each scale comprises ten tones. Take the red scale for example. The
larger dot at h represents the place of its normal, or type of the purest
red ; from that point toward the circumference it is shaded down to
black, and in the other direction it is tinted up to white. The same

ELIOW

Orange

RED

Plan of CHEVEErL's Cheomatio Ciboles, illustrating the principle of complementary
colors, tints, shades, tones, hues, and scales.

with yellow ; its normal is at a, and that of blue at c. From these three
primaries all the rest are derived. Midway between yellow and blue is
the scale of green, which results from their combination in equal pro-
portions, half blue and half yellow. Midway between green and blue
is a scale that we might call a greenish blue. It is only one-quarter
of the distance from blue to yeUow, and therefore is three-quarters

HOW THEY MAT BE EXHIBITED. 93

"blue, and one-quarter yellow, — a hue of blue. Space or distance
represents proportions of color. It will be seen that colors may be
altered in two ways, that is, may move in two directions — along their
scales, by admixture with white or black, producing tones^ and out of
their scales, in the direction of the circles, producing hues. The dia-
gram represents twelve scales, with ten tones on each scale, giving
an arrangement of 120 colors, each having a definite, known compo-
sition. With 24 scales, and 24 tones on each scale, we should have a
scheme of 576 colors.

164. Making a Chart with the real Colors. — An instructive exercise is
to produce such a chromatic chart with the actual colors. Make a
circle upon paper a foot in diameter, designed for twelve scales of ten
or twelve tones. From a box of paints select carmine for the normal
red, gamboge for the normal yellow, and Prussian blue for the normal
blue. By mixing the blue and red with a pencil brush in equal pro-
portions, the violet is produced, and by varying the proportions all
the hues between blue and red are obtained. By mixing blue and
yellow, green, greenish-yellow and yellowish-green are made ; and by
mingling red and yellow, orange, orange -yellow and yellow-orange
are made. Thus all the hues are obtained. By mixing each with
black and white, increasing the proportion of black regularly as you
proceed outwards, and white as you go inwards, the scales will be
formed. Familiar colors would at once locate themselves upon such
a chart, so that we should understand their exact composition. For
example, the crimson will be found near the red, but in the direction
of blue, that is, it is red slightly blued, while scarlet is red, moved
slightly in the opposite direction, toward yellow. So indigo is blue
just started toward red.

165. — How the Diagram shows Complementary Colors. — We determine
the complementary of any color in a moment, by a glance at the sys-
tem of circles. For example, we want the complementary color of
red ; this is formed by the union of blue and yellow, producing green.
Green, therefore, which is the complement of red, is placed exactly
opposite to it on the diagram. So, opposite blue we see its comple-
ment orange, and opposite yellow, violet, which is its complement, and
also the contrary ; the complement of green is red ; of orange, blue ;
of violet, yellow. So of all the scales, no matter how many are
formed, their complements are seen on exactly opposite lines of the
circle. The. complement of red-orange is observed to be blue-
green ; of a reddish-violet, it is greenish-yellow, and so on round the
whole circle. We may even say that the complement of black is

94 RELATION AND MUTUAL ESTFLUENCE OP COLOES.

white, and of -white, black, — of a deep tone on one side, it will be a
light tone on the other. Thus the complementary color of a deep
tone of green will be a correspondingly light tone of red ; of a light
tone of violet, it will be a deep tone of yellow. By means of the dia-
gram, therefore, the complementary of any of the one hundred and
twenty colors can be found by any one in an instant ; a fact of much
practical importance, as we shall soon have occasion to see.

166. — What is meant by Complementary Contrast. — By a glance at the
diagram it will be seen that the complementary of any color is its
exact opposite. It is the color which differs from it the most possi-
ble ; therefore it is in strongest contrast to it. Complementary colors
are, hence, contrasted colors, and their relation is commonly indicated
by the term complementary contrast.

167. Lnmlnons and sombre Colors. — It will be noticed that the three
normals (Fig. 44) of red, yellow, and blue (represented by the larger
dots), are not all located at equal distances from the circumference
or centre. The reason of this is obvious. Yellow is a light, and blue
a dark color. The natural position of yellow, therefore, at its height
of intensity, is nearer to the white than to the black, and the natural
position of bright blue is much nearer to the black than to the white,
while red is intermediate. For this reason it requires more tones to
shade yellow down to black than it does blue, and more also to tint
blue up to white than it does yellow. Colors are thus divisible into
luminous and somlre. Those into which yellow enters most largely,
belong to the first class, and those consisting mainly of blue, to the
second, red forming a medium color.

168. Grays and Browns ; Pure and Broken Colors. — Grays resiilt from
the simple mixture of black and white. Browns are the result of
mixing black with the various colors. The deeper tones of all the
scales upon the diagram are browns. A color which has no black in
it is said to be pure^ while the addition of black produces a l)roTcen
color. The browns are therefore all broken colors. A color may be
broken, however, without directly adding black ; the three primaries
mixed in certain proportions produce this effect. If a little blue, for
example, be added to orange, it neutralizes a pprtion of the yeUow
and red, breaking the color and starting it towards black.

169. No Colors perfectly pure. — We must guard against the error of
supposing that in practice we meet with any such thing as a pure or
perfect color. Even those of the spectrum or rainbow are not per-
fect ; Beewster has shown that the very brightest is contaminated by
others. But when we leave the spectrum, and begin to deal with the

EFFECTS OF COMPLEMENTABIES. 95

commoner aspects of colors, paints, dyes, &c,, their imperfections be-
come mucli more obvious. We are to regard a red surface as reflect-
ing to the eye, not a simple and perfect red, but along with the red a
certain portion of the other colors of the spectrum, which have the
eflfect of weakening and lowering the red. The true statement is, that
the sensation of red is the result only of the predominance of that
color. It is the same with all the colors we see ; others are more or
Jess mixed with them, which impair their brightness.

170. How Colors mntnally improve each other. — The action of colors
upon each other is not a matter of hap-hazard, and although it was
long inexphcable, and half suspected to be a field where nature ca-
priciously refused to be curbed by rules, yet science has at length dis-
covered the reign of law in the domain of colors. Some combinations
of colors are pleasing to the eye, and others disagreeable ; some are
harmonious, and others discordant. The harmonies of color are of
several kinds, but the fundamental and most important one is the har-
mony of complementary contrast. If a purchaser be shown succes-
sively a dozen pieces of bright-red cloth by a shopkeeper, those last
seen will be declared much inferior in intensity of color to the first,
such being the actual appearance which they present to the purchaser's
eye. If now the buyer's attention be directed by the merchant to
green stuffs, they wiU appear extremely bright, unnaturally so ; and
if the eye recur again to the reds, they will look much finer than
before. Eed and green viewed in this way have the mutual effect of
improving each other. It is the same if the two colors be placed side
by side and observed together ; they will so heighten each other's in-
tensity as to appear much brighter and purer than when they are
viewed separately, that is, when the eye cannot be directed from one
to the other. If now we take yellow and violet, or blue and orange,
or violet-red and yeUow-green, and observe them in the same manner,
we shall get the same result ; their brOliancy and clearness will be
mutually heightened. But these colors are complementaries of each
other; complementaries then, when viewed together, improve each
other. They are the most opposite or contrasted, and therefore the
pleasing effect they produce upon the eye is denominated Harmony of
Complementary Contrast. These effects are experimental facts which
may be verified by any one. Take six circular pieces of paper, say
an inch and a half in diameter, and color them respectively red, orange,
yellow, blue, green, and violet. Place each one separately on a sheet
of white paper, and then, with a thin wash of color, tint the white
paper around each circle with its complementary color, gradually

96 EELATION AND MUTUAL INFLUENCE OP COLOES.

weaker and weaker as the tint recedes from the colored circle. If
now the red circle be placed upon the sheet that is colored green, it
will be made to appear greener ; so if the green circle be placed upon
the reddened sheet, the latter color wUl be at once brightened. It wUl
be found upon trial, that each color when viewed with its comple-
mentary, increases its intensity or improves it. "We get by such exper-
iments two kinds of result ; first, a successive change where one color
is viewed after another ; and, second, a simultaneous change when
both colors are seen at once and together. Both these effects require
to be explained, and first of successive contrast.

171. Colors exert an inflnence npon the Eye. — Colors appear to exist
upon the surfaces of external objects, but we must not forget that
their real seat is in the eye itself ; that is, external bodies so modify
the light, that it produces within the eye different effects, which we
name colors. Colors are sensations, or nerve-impressions, the result
of something accomplished within the optic organism. Thus we say
snow is white, and blood is red ; meaning thereby that snow so influ-
ences the light, that it originates within the organ of vision a sensa-
tional effect which we style white ; while blood so modifies the light
falling upon the nerve of the eye as to cause the perception of red.
As color thus finally resolves itself into different modes of affecting
tJie eye J we might naturally expect that both the agent and its organ
would react upon each other, — colors producing changes in the eye,
and the eye producing changes in colors, more or less considerable,
according to circumstances. The eye being a part of the bodily sys-
tem, and governed by general physiological laws, is subject to the
same vicissitudes of varying activity, acute and blunted susceptibility,
as other parts. We shall now notice the change that takes place, only
so far as colors are themselves affected ; deferring to another place an
examination of the influence of colored light upon the eye in refer-
ence to its health (253).

172. Daration of Impressions npon the Retina. — ^Impressions continue
upon the nerve of the eye about one-sixth of a second after the object
is removed. For this reason, a torch whirled swiftly roimd appears
as a continuous streak or ribbon of fire. But the eye continues to be
affected for a much longer time ; although it is not, as we might at
first suppose, by a feeble, lingering impression left upon it, which
gradually fades out after the object is withdrawn from sight. If there
were a continuance of the perception of an object after its removal,
the effect of viewing another object would be the mixture of two
colors. For example, if a bright blue object were seen, and then the

THEY AFFECT EACH OTHER THEOUGH THE EYE. dl

eye suddenly directed to a red, the effect would be a perception of a
mixture of the two, or violet, and this would remain until the first
impression, or blue, faded away from the retina, after which the red
object alone would be perceived. But such is not the case.

173. The Eye loses its sensibility to Colors, and demands tMr Comple-
mentaries. — The influence of any color upon the eye is to diminish or
deaden its sensibility to that color ; it gets fatigued in looking at one
color for some time, so that it appears less bright. If, for example,
the gaze be directed for a time upon a bright red object, that part of
the retina upon which the image is impressed, becomes exhausted by
the action of the red color, and partially blinded to its brightness ;
just as the ear may be deafened for a moment by an overpowering
sound. But the effect does not stop here. If the eye be averted from
the red and directed to white, the red contained in the white will not
produce its natural effect, whUe the balance of the colors in white,
blue, and yellow, make their proper impression upon the eye, pro-
ducing green. Thus the eye, dulled to one color, has a tendency to
see its complementary. If we place a red wafer upon a sheet of white
paper, and fix the gaze upon it steadfastly for some time, and then toss
it off, we shall see a spectral image of the wafer upon the paper, hut it
will te green. The wafer so extinguished the sensibility to red upon
a certain portion of the retina, that when it was removed, the eye
saw the white, minus the red, that is, green. In like manner, if the
eye be impressed with green, it loses its sensibility for it, so as again
to decompose white and see red. If blue is observed, the impressi-
bility of the nerve of sight is lowered for that color, so that white
light is seen without its blue, and orange appears, which is the com-
plementary of blue. In like manner the observance of yellow creates
a tendency to see violet, and in the same way the effect of any color
whatever, is to dispose the eye to see its complement. If we gaze at
the sun at sunrise, when of a ruddy appearance in consequence of his
rays being strained of their blue and yellow as they pass through the
damp atmosphere near the ground, an image wUl be generated by the
eye formed of these missing rays, and, therefore, green. When he
has ascended higher and become of an orange yellow color, the image
will be dark violet. It is well known that in looking at the sun
through colored glasses at the time of an eclipse, spectres of the solar
disk are sometimes produced which continue for a time before the eye.
The color of these is always complementary to the color of the glass
through which the sun was viewed.

174. Simaltaneons contrast of Colors. — But colors placed side by side,

5

98 RELATION AND MUTUAL INPLUENCE OP CO'LOES.

exert upon eacii other, simultaneoudi/, an influence that can hardly be
accounted for by the theory which explains successive contrast. The
effect is of the same kind, — contrasted colors are augmented in bright-
ness, but it results from the equal action of both colors upon the eye
at the same time. It has been stated that surfaces reflect to the
eye rays of other colors beside those which appear. No surface can
so perfectly analyze the white light which falls upon it, as to absorb
all of one color, and reflect all of another. It appears of the color
of the predominating ray, though more or less of the remaining colors
of white light are reflected also, and diminish its purity. We look
upon a red ; it is not perfect, because other colors not red, but the
opposite of red, are mingled with it and reduce its effect. We gaze
separately upon green ; it is vitiated by rays coming from it that are
not green, but its opposite. Now if we could clear away or destroy
these vitiating rays, we should improve both colors, and this is ac-
tually done by placing them side by side. The reducing colors, which
are active when the surfaces are viewed separately, seem to be, in
some way, neutralized when they are brought together, and the com-
plementary of each is thrown upon the other.

175. How associated Colors injure each other. — If certain combina-
tions of color alter each other for the better, it is easy to see how
other combinations must act in other ways for the worse. If the
mutual effect of colors most contrasted be to intensify and exalt each
other, it follows that if those most nearly alike are associated to-
gether, they will vitiate and injure each other. What the exact effect
wiLl be, may be seen at once by inspecting the chromatic diagram.
The complement of violet is yellow. If violet be associated with
yellow, therefore, the only effect it can produce is to make it yellower ;
but suppose it be placed beside other colors, the result must be a ten-
dency to yellow them all. Violet placed beside green drives it out of
its scale (see diagram) toward yeUow. It was hah" yellow before, but
the effect of violet is to increase the proportion of this element, and
thus produce a new hue of yellowish-green. If violet be placed
beside orange, which is also half yellow, it is moved out of its scale
in the same direction as before toward yellow, a hue of yellowish
orange being produced. As orange and green are already half yeUow,
it is obvious that the effect of adding to them a little more yellow will
not be so marked as when this color is cast upon those which do not
contain it. Violet, beside blue, stains it of a greenish hue ; while
beside red it changes it to scarlet. By tracing these effects out upon
the diagram we at once get at the general law of the mutual influence

HOW THEY ARE CHANGED BY CONTRAST.

99

Fig. 45.

of colors. A color placed beside another tends to make that color as
different as possible from itself. In the case of violet just alluded to,
by reference to the diagram it will be seen that the color naturally
farthest from it, by its very constitution indeed exactly opposite to it,
is yellow. Now if bright violet be placed beside the yellow scale, it
will drive every tone of that scale one or two steps back, away from
itself, by making them all still yellower, and you will notice that the
effect of violet upon the other colors, by throwing yellow upon them,
is to start every one of them away from itself in the direction of its
antagonist, which is the yellow. If traced out it wiU be seen that the
effect of any other color is precisely the same. The complementary
of any color thrown upon another renders it more unlike, or increases
the difference between them.

176. Contrast of Tone. — The effect of viewing white and black to-
gether is to heighten the contrast between them, and so with the in-
termediate tones of a scale of white and black. The accompanying
wood-cut (Fig. 45) affords an im-
perfect illustration of this effect.
It consists of five bands, shaded
successively deeper and deeper
from left to right. As the eye
glances at the scale, the bands
appear darker at their left bor-
ders and lighter at their right.
But this appearance is an effect
of contrast ; for if we take two
slips of paper with straight edges,
and cover all the diagram but
any single band, its surface will be seen to be perfectly uniform. When
viewed together, however, there is a heightening of the real differences,
the light tones seem lighter and the dark tones darker, almost as if
the intention was to represent fluting. It is so with the different
tones of any color which has been shaded with black or tinted with
white. If we place two different tones of the same color together,
they always alter each other's intensity ; dark tones making adjacent
light ones appear still lighter, and light ones making dark tones seem
still darker. This is, perhaps, because the absence of light in the
dark color renders the eye more sensitive to the white light of the
lighter color, and on the contrary the dark color appears darker, be-
cause the white light of the lighter color destroys the effect of the
small amount of white light reflected by the other. Thus if we place

Illustrating the effect of contrast of tone.

100 RELATION AND MUTUAL INFLUENCE OF COLORS.

a dark red beside a light rose-color, or a deep yellow iu contact "witli
a straw-color, they will, as it were, push each other further apart, the
light tones in both cases appearing lighter, and the deep ones deeper,
so as to deceive the eye in regard to the real depths of their colors.
Thus for tones as well as hues the law of Cheteetjx holds good. " In
the case where the eye sees at the same time two contiguous colors., they
will appear as dissimilar as possiile, ioth in their optical composition
and the height of their tone^

177. Harmonies of Analogy. — The employment of glaring or intense
colors in many cases, as often in dress, is not admissible by the rules
of cultivated taste. It is chiefly among the rude and nncultured
that we remark a passion for gaudy and flaunting colors. With the
progress of a refined civilization there is a tendency to the employ-
ment of more subdued colors in personal and household decoration.
Not by any means that good taste requires the total rejection of bright
colors, but only that they be used with skill and discretion — ^be ameli-
orated by combination, so as not to produce staring and stunning effects,
or strong and deep contrasts which often offend the eye. Harmonies of
complementary contrast are to be first and chiefly sought in chromatic
arrangements ; but these are comparatively limited, and in the demand
for variety, othei" concords are found, which, although less striking,
often give beautiful results. In studying the best arrangement of
colors to produce a harmonious grouping, regard must be had to the
kind of effect required, whether lively, medium or sombre. In one
case, bold striking contrasts will be sought, in another mild ones ; and
again, rejecting contrasts altogther, we may get an agreeable effect by
grouping together similar or analogous colors. Harmonies of analogy
may be produced in three ways. First^i we may arrange the different
tones of a single scale in a series, beginning with white and terminating
with brown black, leaving as nearly as possible equal intervals be-
tween them. This will produce a pleasing result. The greater the
number of tones the finer will be the effect. Second, we may asso-
ciate together the hues of adjacent scales, all of the same tone, and
often produce an agreeable analogy. But sometimes colors of near
scales mutually injure each other, as blue and violet ; the complemen-
tary of blue, which is orange, being thrown upon violet gives it a
faded and blackened appearance ; while tlie complementary of violet,
which is yellow, falling upon blue turns it to green. Sometimes when
one color is injured we may sacrifice it to give prominence or relief to
another. Tliird, a pleasing harmony of analogy is produced by view-
ing groupings of various colors through a colored medium that casts

EFFECTS OP DIFFERENT GEOUPINGS. 101

its own peculiar hue over tlie whole, as when we view a carpet in
light that comes through a stained glass window.

178. Circumstances which disturb the influence of Colors. — Various con-
ditions exert a modifying effect upon the mutual action of colors.
The result may he greatly influenced by the shape of the object, and
the manner of its exposure to light. The surface of a red curtain,
for example, hung in folds, appears of different hues, the parts most
exposed to the light being changed in the direction of scarlet, while
those more protected from it are shaded so as to approach a crimson.
The condition of surfaces is also important. When they are glossy
their colors affect each other much less, and a bad association may be
concealed or overlooked where the elegance of symmetry of the
object, or the light and shade are so related, or our ideas are in some
way so associated with it as to draw the attention from the ill effects
of the colors. It is often thus that flowers present bad associations,
yet our feeling concerning them is such that we are not offended as
when we see the same upon flat unglossed surfaces. The flower of the
sweet pea, for instance, gives us the alliance of red and violet, which
mutually injure each other, though the green leaves set off the red
and help the result.

179. Effect of associating Colors with White. — All colors appear
brighter and deeper when associated with white, because its superior
brilliancy renders the eye insensible to the white light which accom-
panies and weakens the color. At the same time the white is tar-
nished by the complementary of the color falling upon it. "White is
BO intense that in all its arrangements with color, except perhaps light
tones of yellow, there will be contrast. It may often be interposed
with advantage between colors which injure each other. All the pris-
matic colors gain by grouping them with white, but not in an equal
degree, for the height of tone of the color makes a decided difference
in the result. The deep tones of blue, red, green, and violet, contrast
too strongly with white, while the light tones of the same colors form
with it the pleasantest contrasts we can obtain. Orange, the most
brilliant of the colors, is almost too intense with white, while the
deeper tones of yellow appear well with it.

180. Effect of associating Colors with Black and Gray. — Black is agree-
able if associated with almost any color. With their light tones it
contrasts well, making them appear lighter, and being itself darkened,
while their sombre complementaries thrown upon the black scarcely
affect it as its surface reflects so feebly. With the deep tones of the
Bcales it forms harmonies of analogy, although their luminous com-

102 PKACnCAL SUGGESTIONS EST COMBIOTNG COLORS.

plementaries, especially those of blue and violet when falling upon
black, deprive it of its vigor, and tend to make it look faded. Gray
being intermediate between black and white, it is used where white
gives too strong a contrast, and black makes the combination too
sombre, as with orange and violet, green and blue, green and violet.

YL— PKACTICAL SUGGESTIONS IN COMBINING COLOKS.

181. Articles of Dress. — A recollection of the foregoing principles
may enable us to avoid gross errors in combining colors. Thus a lady
would hardly trim a violet bonnet with blue flowers, or an orange
with yellow ribbon, while she would do well to trim a yellow bonnet
with violet or blue, and a gi-een one with rose-red or white, and to
follow the same general rule in arranging the colors of a dress. We
are not to overlook the effect of contrast of tone as well as color. A
black coat that is much worn, will appear well in summer in contrast
with white pantaloons ; but if put on over new black pants, it will
appear older, rustier, and more threadbare than it really is. Stains
upon garments are less apparent where there is considerable difference
among the colors of the various articles of apparel, than where they
are more uniform, the contrast among the colors rendering that be-
tween the stain and the surrounding cloth less conspicuous. Colored
articles of dress produce a deceptive effect in reference to the size of
the wearer. The influence of dark or black colors is to make the per-
son wearing them seem smaller, while white or light dresses causes the
figure to appear larger than the real size. Large figures or patterns
upon dresses and horizontal stripes make the person look short, while
narrow vertical stripes on a dress cause the wearer to seem taller.

182. Inflncnce of Colors npoa the Complexion. — Any colored objects,
as bonnet trimmings or draperies, in the vicinity of the counteiyjnce,
change its color ; but clearly to trace that change we must know what
the cast of complexion is. This varies infinitely, but we recognize
two general sorts, light and dark, or Monde and Irunette. In the
blondes or fair-complexi(?ued the color of the hair is a mixture of red,
yellow, and brown, resulting in a pale orange brown. The skin is
lighter, containing little orange, but with variable tinges of light red.
The blue eye of the blonde is complementary to the orange of the
hair. In brunettes the hair is black, and the skin dark, or of an
orange tint. The red of the brunette is deeper or less rosy than that
of the blonde. Now the same colors affect these two styles of com-
plexion very differently. A green setting in bonnet or dress throws

HOW THEY APTECT THE COMPLEXION. 103

its complement of red upon the face. If the complexion be pale and
deficient in ruddy freshness, or admits of having its rose-tint a little
heightened, the green will improve it, though it should be delicate in
order to preserve harmony of tone. But green changes the orange
hue of the brunette into a disagreeable brick-red. If any green at all
be used, in such case it should be dark. For the orange complexion
of brunette the best color is yeUow. Its complementary, violet, neu-
tralizes the yellow of the orange and leaves the red, thus increasing
the freshness of the complexion. If the sMn be more yellow than
orange, the complementary violet falling upon it changes it to a duU
paUid white. Blue imparts its complementary orange, which im-
proves the yellow hair of the blondes, and enriches white complexions
■ and light flesh tints. Blue is therefore the standard color for a
blonde, as yeUow is for a brunette. But blue injures the brunette by
deepening the orange, which was before too deep. Violet yellows the
skin, and is inadmissible except where its tone is so deep as to whiten
the complexion by contrast. Eose-red, by throwing green upon the
complexion, impairs its freshness. Eed is objectionable, unless it be
sufiiciently dark to whiten the face by contrast of tone. Orange
makes light complexions blue, yellow ones green, and whitens the
brunette. White, if without lustre, has a pleasant efiect with light
complexions ; but dark or bad complexions are made worse by its
strong contrast. Fluted laces are not liable to this objection, for they
reflect the hght in such a way as to produce the same effect as gray.
Black adjacent to the countenance makes it lighter.

183. Arrangement of Flowers in a Bouquet. — In grouping flowers, com-
plementary colors as far as possible should be placed side by side, blue
with orange, yellow with violet-red, and rose with the green leaves.
On the contrary we should avoid combining pink with scarlet or
crimson ; orange with orange-yeUow ; yellow with greenish-yeUow ;
blue with violet or violet-blue ; red with orange, or pink with violet.
If these are to be inserted in the same nosegay, white should be inter-
posed between them, as it prevents colors from acting injuriously upon
each other while it heightens their tone.

184. Best colors for Paper Hangings. — ^Dark paper for the waUs is bad,
because it absorbs too much light, and the room is not sufficiently
luminous : this is especially true of rooms with a northern aspect
where the sun never enters, for such apartments paper of the lightest
tints should be used. "We have seen that the complementaries of red
and violet are bad for the complexion (181), red and violet are there-
fore objectionable as wall colors. Orange and orange yeUow are

104 PEACnCAL SUGGESTIONS IN COMBINING COLORS.

fatiguing to the eye. Among the simple colors light blue, light green
(314), and yellow, seem fittest for hangings. Yellow is lively, and ac-
cords well with dark furniture and brunette complexions, but it hardly
appears well with gilding. Light green is favorable to pale skins,
deficient in rose, and suits with mahogany furniture. Light blue goes
well with mahogany, is excellent with gilding, and improves blonde
complexions. White and light gray, with velvet patterns the same
color as the ground, are well adapted to a wall to be decorated with
pictm-es. In selecting a 'border we should seek for contrast, so that
it may appear, as it were, detached from the hangings with which it
is associated. If there is a double border, an interior one of flowers
and an exterior one, the last must be deep in color and much smaller.
Yellow hangings shoiild be bordered with violet and blue mixed with
white. Green will take any hue of red as a border. White hangings
should have orange and yellow. Gray uniform hangings admit of
borders of all colors, but no strong contrasts of tone ; gilt borders do
well with them. If the gray be colored, the border should be com-
plementary. The neutral tints of paper, drabs, stones, &c., are par-
ticularly appropi'iate for picture-galleries, — they produce good effects
in other rooms with weU chosen borders and mouldings.

185. Pictures, Frames, and Gilding. — ^As the picture itself is the valu-
able object upon which we wish to fix attention, it is not in good taste
to divert or distract it by gaudy and conspicuous surroundings and
ornaments ; hence simple framings, just enough to isolate or separate
the picture, are preferable. Gilt frames will do with large oil-pictures,
particularly if there is no gilding represented in the picture. Gilt
frames also answer well for black engravings and lithographs, but a
little margin of white should be left around the subject. Black
frames, by their strong contrast of tone, tend to lighten the aspect of
the picture, and often spoil a good engraving by taking the vigor from
its dark colors. Gray frames are good, especially if the picture have
a leading color, and the gray be slightly tinged with its complementary.
As a rule, neither the frame nor the border within it should ever be
suffered by their brightness, color, or ornaments, to injure the colors,
shadows, or lights of the picture. The best ground for gilt ornaments
is blue, because its complementary intensifies the color of the orna-
ments ; hence shrewd shopkeepers who sell gilt articles line their show-
cases with blue. A bright green ground reddens and improves gilt
objects. Eed and orange pervert the gilt tint, and black lightens and
weakens it (144).

186. Assortment of Colors for Fnrnitnre. — In determining the colors

COMBESTATIONS IN HOUSE-FUENISHIKG. 105

to be used in furnishing a room, the amount of light is an important
consideration ; dark colors, as dark blue, crimson, &c., require much
light to be seen distinctly. Eed curtains redden the transmitted light
of day, and impart this color to the countenances it falls upon. But
by artificial or reflected light, red curtains and fm-niture dispose the
eye to see green in the countenances of people in the room, while
green curtains make the countenances rosy. Chairs and sofas, when
complementary to the paper upon the wall, are most favorable to dis-
tinct vision ; but for collective effect, when we desire to present the room
as a unit, bold and complementary contrasts are iuadmissible, as they
fix the attention too much upon distinct and separate objects. It is
better, therefore, in arranging for chairs and hangings to seek contrast
of scales, or hues and harmonies of analogy. In trimming chairs and
sofas, vivid reds should never be used with mahogany, for they are so
bright that the mahogany loses its beauty, and looks no better than
oak or black walnut. Crimson velvet is often used with mahogany
because of its durability ; but the colors are so nearly allied, that a
strip of green or black galloon should be used as a border to the stuff,
or a narrow cord of golden yellow with gilt nails. Green or green
grays are best suited to trim mahogany and red-colored woods. In
using differently colored woods we can assort the colors of their trim-
mings according to the rule previously laid down. The carpet should
be selected with reference to the other furniture of the room. K
mahogany is used, the carpet should not have a predominance of red,
scarlet, or orange in it. If the furniture exhibit various and vivid
colors, the pattern of the carpet should be simple and sober, as green
and black for example, whUe if the furniture is plain the carpet may
be gay.

VII.— PEODUCTION OF ARTIFICIAL LIGHT.
1. The Chemistet of Illtjmination.

187. Natural and Artificial Light. — As respects its sources, light is o '
two kinds, natural light, or that which comes from the sun, moon
and stars ; and artificial light, or that which man obtains at will by
various means. Artificial light may be procured by electricity, gal-
vanism, and phosphorescence ; but the ordinary method is by tliat
kind of chemical action which is termed comdustion, the nature of
which has been explained when speaking of heat.

188. Light emitted by ignited Bodies. — AU solid substances shine
when sufficiently heated. The temperature at which they become

5*

106 PKODUCnON OF AETIFICIAL LIGHT.

luminous, according to Dr, Deapee, "wlio has lately investigated the
subject, is 977° F. He enclosed a number of different substances
with a mass of platinum in a gun barrel ; upon heating and looking
down the tube, he saw that they all commenced to shine at the same
moment, and this, even though, as in the case of lead, the melted con-
dition had been assumed. The color of light emitted from ignited
substances was found to depend upon the degree to which they were
heated. Dr. Draper showed that as the temperature rises, the
colored rays appear in the order of their refrangibility, first red, then
orange, yellow, green, blue, indigo and violet, are emitted in succes-
sion. At 2130° all these colors are produced, and from their commix-
ture the substance appears white-hot. The same Investigator also
found, that as the temperature of an ignited solid rises, the intensity
of the light increases very rapidly ; platinum at 2600° emitting almost
forty times as much light as at 1900°.

189. All onr illnmination comes from bnrning Gas — The foregoing ex-
periments were made upon solid substances, but their results do not
hold true for gases. These require to be heated to a much higher
temperature before beginning to shine ; and when they do become
luminous they emit but a feeble light. If we hold a piece of fine iron
wire in the hot air which streams up above a lamp flame it wUl
quickly become red, showing that a degree of heat which makes the
metal shine does not make the air luminous. And yet all ordinary
illumination comes from the combustion of gases. "We use those ma-
terials for lighting, which in burning produce flame ; and flame is
burning gas. All substances which can be used for light must be
capable of conversion into the gaseous state. The process is essentially
the same, whether we burn the illuminating gas which is brought to
our dwellings in underground pipes, or the liquid oil, or solid sperma-
ceti. In the first instance the gas is manufactured on a large scale
from solid bituminous coal or resin ; in the latter cases the liquid oil
and solid tallow or wax are converted into gas at the time of hurning.
In all cases the light proceeds from a rising stream of gaseous matter
which is lighter than the air, and therefore tends to ascend.

190. What takes place in the Lnminons Flame. — The materials used
for illumination contain hydrogen and carbon, and the gas they yield
consists of these elements more or less pure. Hydrogen, as we have
before stated, is the lightest and most ethereal of all substances (76).
Tlie gas which gives rise to flame in illumination is therefore com-
pound— a hydro-carbon. In burning, the oxygen of the air combines
with these two elements, but it is not attracted to them equally. It

CHEMISTEY OF ILLUMINATION.

107

Fi&. 46.

Fig. 47.

seizes upon the hydrogen first, burning it with an intense heat, and
the production of water. As the hydrogen combines with oxygen, it
abandons the carbon, which is thus set free
in a pure state. F ow pure carbon is always
a solid. As the hydrogen leaves it, therefore,
it is set free in the form of exceedingly mi-
nute solid particles in the midst of the heated
space, — those heated to redness, yellowness,
or whiteness, become luminous, and are the
real sources of the light. The carbon par-
ticles remain suspended in the flame but for an instant ; they are
themselves quickly burned and converted into carbonic acid.*

191. How these facts may be shown. — If we hold a piece of clean
cold glass a short distance above a candle flame (Fig. 46), a fine dew
will be seen deposited upon it, which is the water generated within
the flame. If a piece of white
earthen be lowered over the
flame the combustion is in-
terrupted, and the uncon-
sumed particles of carbon are
deposited upon the white
surface, thus proving that
they exist free in the flame.
K an inverted tumbler be
held above a flame, so that
the rising current may enter
it (Fig. 47), and then it be
closed with a card, set down, and a little clear lime-water poured into
it and shaken, it will become milky from the combination of the car-
bonic acid with the lime, which shows that the former substance was
generated within the flame.

192. Admirable simpUcity of the Laws of lUnmination.— There is a
wonderful simplicity and beauty in this chemistry of iUumination.
The same active prmciple of the air which animates the living body
and nourishes the fires which warm us, is also the awakener of light.
All artificial illumination that we employ is due to the chemical energy
of oxygen gas. The hydro-carbon compounds, upon which oxygen
acts, are not only universal as life itself, being produced in all kinds

* See the author's Atlas of Chemistry and Chemical Chart of Colored Diagrams,
iUustrating combustion and illmnination.

108 PEODTJCTIOlSr OF AETIFICIAL LIGHT.

of plants and animals, but the very crust of the glohe is stored with
endless accumulations of them. The hydrogen combines with and
condenses a much larger amount of oxygen than any other element,
and consequently produces a great heat. But the burning of these
pure gases, although the heat is so high, hardly creates a perceptible
light. To get illumination, solid matter is required. Accordingly the
lightest and most subtle of aU gases, hydrogen, is associated with car-
bon, the most refractory of aU solids, which remains fixed without
melting or vaporizing at the intensest heat whicli art can produce.
These carbon atoms are set free, and shining brilliantly for an instant
pass to the verge of the flame, and there unite with atmospheric
oxygen, forming carbonic acid gas. The two products of combustion —
vapor of water and carbonic acid — are both entirely transparent and
invisible, so that although constantly formed within and around the
flame, they do not eclipse or obscure it, but let the light pass freely
in all directions. If oxygen were equally attracted to hydrogen and
carbon, so as to burn them both at once, no solid particles would be
liberated in the flame, and consequently there could be no light. It
is the successive combustion which takes place, — first the hydrogen
burning and then the carbon, which gives rise to the luminous eflfect.

193. Threefold form of Ulnminatiiig Substances. — The modes of burn-
ing illuminating materials are various, depending upon their forms and
properties. If capable of being used in a solid condition, they are
moulded into a cylindrical or rod-like shape, and are called candles.
If liquid, they are consumed from suitable vessels known as lamps;
and if gases, they are simply jetted from minute orifices, by pressure
upon the gaseous fountains. There are several things with respect to
each of those methods of illumination which it is important to under-
stand.

2. Illtjminatioit by means of Solids.

194. Adaptation of Tallow for Candles. — Tliose fatty and waxy bodies,
which are sufficiently hai'd and solid to be handled, are worked into
candles. They are made from tallow, stearine, spermaceti, and wax.
There has been no way devised for burning those softer, fatty and
greasy bodies which lie between the liquid oils and these firmer sub-
stances. Tallow derived from beeves or sheep is most universally
employed for candles. If they are mixed there should not be too
great a proportion of mutton tallow or suet, as this contains a peculiar
principle called Mixin^ Avhich causes ii sometimes to give a disagree-
able smell, especially in hot weather. When of the best quality tallow

ILLUMINATION BY TVfEANS OF SOLIDS. 109

is white, firm and brittle. Alum is often put witli it to harden it.
The bad quality of tallow candles is chiefiy owing to their adulteration
with hog's fat and cheap soft grease, which makes them smell, gutter
and smoke. Good tallow candles will resist decomposition for two
years, and are better after being preserved six or eight months. They
should be kept from the atmosphere, and may be well preserved by
being covered with bran. The place for their preservation should be
cool and dry, as dampness mildews and damages them. Light turns
them yellow.

195. Candles made from Stearic Acid. — The fats and oils are believed
to consist of acids combined with a base ; at all events they are capa-
ble of being decomposed and separated into those substances. The
common base which exists in all fats and oils is, when set free, a sweet
liquid called glycerin. The substances combined with it are stearic
acid, margaric acid, and oleic acid. Stearic acid, combined with
glycerin, forms stearin. Margaric acid, with glycerin, yields mar-
garin ; and oleic acid, with glycerin, produces olein. Oleic acid, or
olein, is the more liquid portion of oleaginous bodies ; it predominates
in the fluid oils. Stearic acid, on the contrary, abounds in the hard
fats and tallows ; it is their chief solidifying element. Margaric acid
is less solid, being intermediate between stearic and oleic acids. The
intermixture of these, in various proportions, gives rise to all the
various grades of softness and solidity which the endless oU and fat
tribe exhibit. Tallow contains seventy to seventy-five per cent, of
stearic acid, and olive oil but twenty-five. Candles were at first made
from stearin, and were much superior to tallow ; but they are now
manufactured from stearic acid, which is more infusible. This sub-
stance does not feel greasy to the touch, and is firm, dry, and brittle.
It makes hard and briUiant candles, which are considered nearly equal
to wax.

196. Spermaceti and Wax. — Spermaceti is a kind of stearine existing
in the oil taken from cavities in the skulls of certain species of whales.
It is manufactured into candles, which are of a beautiful silvery white
aspect, translucent like alabaster, and having a high lustre. The wax
of which bees construct their honeycomb is also used for candles. It
is purified and bleached to a pure white. It burns with a clear and
beautiful light, and is the most expensive material employed for illu-
mination. Owing to its high price it is often adulterated, "White
lead, oxide of zinc, chalk, plaster, and other earthy bodies may be
detected by boiling the wax in water, when these substances will
separate and faU to the bottom. If starch or flour has been used, they

no

PEODtrCTION OF AETrPICIAL LIGHT.

Fig. 48.

may be detected by boiling and adding a solution of iodine, •wMcli
will yield a beautiful blue color, the test for starcb. Yellow bees'-wax
is often adulterated with resin, pea and bean meal, and many other
substances. The former may be detected by the smell, and the latter
by the iodine solution.

197. Structare of Candles— Office of the Wick. — The common burning
candle affords a beautiful illustration of the general principles of illu-
mination. If we should attempt to burn solid taUow or wax in the
lamp to produce light, it would be found very difficult to set it on fire,
as it would melt away long before it could ignite. But if at length
made to burn, a much larger amount of the combustible would be on
fire than the air would perfectly consume ; there would therefore be
a thick smoky flame instead of a clear white light. Some contrivance

is hence needed to avoid this result and regulate the com-
bustion, and this is secured by placing cotton fibres within
the combustible, which form the wicTc. These fibres are
placed parallel in the axis or centre of the candle. "When
the wick which protrudes at one end is set fire to, it ra-
diates heat downwards, so as to melt the material of the
candle, and form a hollow cup filled with the liquid com-
bustible around the wick-fibres (Fig. 48). The flame is
fed from this cup or cistern by the wick, which draws or
sucks up the oily liquid exactly as a sponge or towel
draws up water, by what is called the force of capillary

attraction, or the attraction of small tubes for liquids.

from^the"dstern ^^ this case the spaces between the fibres act as tubes,
of oil below. ^^^ attract upward the liquid fat or wax.

198. The hnraing Caadle a miniature Gas-Factory. — "We thus see that
the caidle is a kind of lamp which constantly melts its own combus-
tible. From the reservoir the wick draws up the liquid material to
the centre of the flame. Here, in the midst of a high heat, and cut

off from the air, it undergoes another change
exactly as if it were enclosed and heated in
the gasmaker's retort, — it is converted into
gas. The candle-flame is not a solid cone of
fire. If we lower a piece of wire-gauze or
broken wiadow-glass over the flame (Fig. 49),
we shall see that the interior is dark, and that
what we regard as the flame is really but a
thin, hollow, luminous shell of fire surrounding
This space is filled with the hydro-carbon gas

Fig. 49.

The candle-flame hollow.

the dark inner space.

ILLUMINATION BY MEANS OP SOLIDS. Ill

manufactured from the liquid tallow, stearine, spermaceti, or wax,
drawn up by the wick. This may be directly shown. If one end of a
glass tube, having a bore ^ of an inch, be introduced into a candle-flame,
as seen in Fig. 50, the gas will be conveyed away r a 50

through it, and may be lit at the other end, thus
exhibiting a miniature gas manufactory, pipe and
jet. "When a candle is blown out, gaseous pro-
ducts of distilled and burnt tallow continue to
rise, emitting a disgusting odor, and the candle
may be re-lit by applying a light to the smoky
stream of combustible gas which will convey
the flame back to the wick. It is the hydro-
carbon gas that is really burnt and produces the
light, the hydrogen and carbon being successively
consumed, as we have seen, at the surface, or The interior of the candle-
where the air comes in contact with the gas. ^^^ ® ^^ ^^'

199. Interfereace of the Wick with Light. — As the candle consumes
downward, the wick of course rises into the flame. In a short time
it becomes so much lengthened as to interrupt the combustion and
interfere with the light. Particles of unconsumed carbon are gradu-
ally deposited upon the wick, forming a large spongy snuff which
nearly extinguishes the light. Peclet found that if the intensity of
the light from a freshly snuffed candle be represented at 100, if left
without being snuffed, its brightness is reduced in 4 minutes to 92, in
10 minutes to 41, in 20 minutes to 32, and in 40 minutes to 14, al-
though the consumption of the candle remained the same. Rumfoed
found that the brilliancy of an unsnuffed candle was reduced f in 29
minutes. To prevent this annoyance and the necessity of frequent
snuffing, wicks are sometimes so plaited and twisted, or are so slender
that they bend over to the side of the flame, and coming in contact
with the air are consumed (Fig. 48). This however is only practicable
with the more infusible candles, stearine, wax, and spermaceti. Tallow
melts so easily, that if the wick were bent over, the candle would melt
down on that side and burn badly.

200. Influence of the melting point. — Tallow melts at 100°, spermaceti
at 112°, stearine at 120°, stearic acid at 167°, and bleached wax at
155°. Candles made from those materials which are most infusible of
course melt slowest ; the liquid which is formed in the cup being smaller
in quantity may be drawn upward to the flame with a smaller wick.
Hence the wicks of wax and spermaceti candles are smaller than those
used for taUow. A slender wick in a tallow candle would melt the

112 PEODUCnON OP AETiriCIAIi LIGHT.

combustible faster than it could consume it, the liquid would overfill
and overflow the cup, which takes place in what is called the guttering
of candles. For this reason candles of softer materials require larger
wicks,

3. iLLTUrnSTATION BY MEANS OF LlQUIDS,

201. Argand's great ImproTemcnt, — Lamps are vessels of various
forms and appearances for burning light- producing substances in the
liquid condition. They generally have wicks to feed the flame, which
may be either solid round masses of fibre like those of the candle, or
fibres arranged flatwise so as to produce a long thin flame, or they
may be circular. Dr. Feanklust showed that two small wicks placed
in two candles and burnt side by side, will give more light than if they
were combined and placed in one candle, as there is a greater burning
surface ; hence the advantage of spreading the wick-fibres out, and
using them in some other form than condensed in a solid mass. Very
large wicks of this kind convert the oil into gas faster than the air can
completely burn it, and the consequence is that the flame smokes. To
remedy this evil, the most important improvement yet made in lamps
was contrived in the year 1789 by Ami Aegand of Geneva, and since
called after him the " Argand Burner." He made the wick hollow,
so as to burn in a ring or circle, and thus admitted a current of air to
the inside of the flame, by which the central core of dark nnburnt
gases is avoided, and a double burning surface secured. By means of
sheet-iron chimneys set above the flame (which were soon replaced by
those of glass), a strong upward draught of air was secured, which
heightened the combustion and greatly intensified the light. The
wick was raised and depressed either by means of cogwork {racTc and
pinion) or by a screw ; the supply of oil is thus regulated to that of
the air, and smoking prevented. An important advantage gained by
the Argand burner is the great steadiness of the light caused by the
chimney. "When a draught of air strikes an unprotected flame, its
force and cooling influence check the combustion,* and produce flicker-
ing and smoke. In Argand burners, on the contrary, the supply of
air is self-regulated, and the cylinder prevents any interruption of the
flame by outside currents,

202, Improvement upon the Argand Burner, — The cylinder that Ae-
GAND employed was straight, or had vertical sides. This allowed a
much larger amount of air to rise within it than could take part in
the combustion, and this excess had the partial effect of cooling the
flame. M. Lange, a Frenchman, improved the form of the chimney-

ILLUMriSrATION BY MEANS 01' LIQUIDS. 113

tube, by contracting its size and constructing it with a shoulder at
such a point (JFig. 51 i), that the rising air striking against it was de-
flected inward and thrown directly upon the flame. This had a power-
ful efiect in increasing the combustion and heightening the intensity
of the light. Another improvement consisted in mounting a button
just above the circular opening within the burner, so that the current
of air that comes up from within, will be deflected outwards, as shown
in fig. 54 a, and thus strike directly upon the inner surface of the
flame. The main point to be considered in the structure ^^^ ^^^
and management of lamps upon the Argand principle, or
with chimneys, is the relation between the current of air
and the flow of oil. This is controlled by the movable
wick, the movable button, and the width and height of
the chimney. As chimneys of glass only can be used, ^---J I _g
they are apt to be made large to lessen the liability to <^^
fracture, though the danger is generally overrated. As i,™

a consequence more air is conducted to the flame than is
demanded for vivid combustion, while the excess, by rapidly convey-
ing away the heat, lowers the temperature of the flame, and thus
diminishes its luminous intensity. Dashing a surplus of air against
the flame is also unfavorable to that successive combustion which is
essential to illumination (192).

203. Points to be secured iu the structure of Lamps. — ^Lamps are made
in a great variety of ways suited to burn different kinds of oily matter,
and adapted to avoid, as far as possible, certain difficulties which are
incident to this mode of lighting. The distance from the burning
part of the wick to the surface of the reservoir from which the oil is
derived should remain unchanged, so that an equal quantity of oil
may be drawn up at all times, and the reservoir should be so shaped
and placed that its shadow will occasion the least inconvenience. If
the wick is supplied from a reservoir below, it is obvious that just in
proportion as that is exhausted, the distance from its surface to the
flame is increased ; the wick-fibres elevate less oil, and the light grows
faint and dim. To remedy this, the reservoir in some cases is made
to have a large surface of oil that will fall but little distance, although
a considerable amount is withdi-awn. To avoid the objectionable
shade thrown by such a large cistern close to the wick, the astral
lamp had its reservoir constructed in the form of a narrow circular
vessel or ring, which threw but a small shadow. The sinumbra lamps
had this ring so shaped and mounted as to produce still less shade.
Sometimes there is a fountain of oil placed on one side higher than

114 PEODUCnON OP AETIFICIAL LIGHT.

the wick, "witli a self-acting arrangemeiit by which the reservoir is fed
from it, and its height constantly maintained at the same point. The
shadow cast, in this case, upon one side, is objectionable, and limits its
use to that of a study lamp (Fig. 67). In the Oaecel lamp, or mechani-
cal lamp, clockwork is applied to pump up the oil through tubes in a
constant stream to the wick, thus keeping it thoroughly soaked, while
the excess of the oil drops back into the cistern, which is situated so
far below as to cast no shade. It is moved by a spring, and wound
up like a clock. It runs sis or eight hours, maintaining a constant and
equal flow of oil, and a bright and steady flame. These lamps are ex-
cellent, but expensive, costing from fifteen to seventy-five doUars, and
requiring mach care.

204, Hot-Oi! Lamps. — One great obstacle to the use of lamps lies ia
the viscidity, or thickness and consequent sluggish supply of the oil to
the wick ; this becomes a very serious difficulty with common lamps
during the winter. Dr. Uee made some experiments to ascertain the
relative viscidity or fluidity of different liquids, and of the same liquids
at different temperatures. He introduced 2,000 water-grain measures
of the liquid to be tested in a cup, and then drew it off with a glass
syphon of \ inch bore, having the inner leg 3, and the outer one 3j
inches long. If the weight or specific gravity of two liquids, and
their consequent pressure upon the syphon were the same, their dif-
ference of viscidity would be determined by the different time they
would require to flow off through the tube. He found that 2,000
grain-measures of water at 60° ran off through the syphon in 73 sec-
onds ; but when heated to 180°, they ran off in 61 seconds. OU of
turpentine and sperm oil have very nearly the same specific gravity ;
yet 2,000 grain-measures of oil of turpentine ran off in 95 seconds,
while that quantity of sperm oil took 2,700 seconds, being in the ratio
of 1 to 28| ; so that the fluidity of od of turpentine is 28^ times greater
than that of sperm oil. Sperm oil, when heated to 265°, ran off in
300 seconds, or one-ninth of the time it took at a temperature of 64°.
Hence lamps have been advantageously constructed to heat the oU
before burning, either by means of a copper tube which receives heat
from the flame, and conducts it downward to the reservoir, or stiU
better by means of a cistern placed above the flame. Paekee's Eng-
lish Economic Lamp has its oil heated in this latter way, and is said
to perform admirably.

205. Compositlou of Oils. — The oils in general use in these lamps are
those derived from fish, chiefly whales, and known as sperm-oU and
train-oil. Lard-oil is also much employed. It is the more oily portion

ILLUMINATION BY MEANS OF LIQUIDS. 115

of hogs'-fat separated by artificial means. The chemical composition
of these oils is quite similar to that of the harder substances which
are wrought into candles. Sperm-oil consists in 100 parts — of carbon
78, hydrogen 12, and oxygen 10 ; mutton tallow, of carbon 'J'S'IO,
hydrogen 11*70, and oxygen 2'30 ; wax, of carbon 80'4, hydrogen
11'3, and oxygen 8'3.

206, Properties of Spirits of Turpentine or Campliene. — In addition to
these substances a new class of compounds, the basis of which is de-
rived from the turpentine of the pine tree, have latterly come into use.
By distillation of the turpentine pitch, it is separated into a thin trans-
parent liquid, spirits of turpentine or oil of turpentine, and a hard
brittle residue known as common resin. The crude spirits of turpen-
tine when rectified, that is, separated as completely as possible from
resinous matter by repeated distillation, is burnt in lamps under the
name of camphene. It differs from the substances just mentioned in
its extreme liquidity (being, as we have seen, 28^ times more fluid
than sperm oil) ; in its powerful pungent odor, and in chemical compo-
sition, as it contains no oxygen, and consists of 88'46 parts in a hun-
dred of carbon to 11*54 of hydrogen, and is therefore called Tiydro-
carion. Oil of turpentine is also much more highly inflammable, and
is volatile and explosive.

207. Conditions required for its Combustion. — Oil of turpentine is a
superior illuminating substance, but it contains so large a proportion
of carbon, that if burned in the ordinary way, it smokes excessively.
Lamps designed to burn it require to be so constructed as to supply to
the flame a large and powerful draught of air, to effect the complete
combustion of its elements. Camphene burns with a flame very much
whiter and brighter than any of the substances we have yet noticed,
and which displays the natural colors of objects, as flowers or pictures
in their true tints, much more perfectly than the light of candles and
oil lamps. Although more luminous, the camphene flame is smaller
than the oil flame. This is explained by the fact that camphene con-
sists entirely of carbon and hydrogen, whUe the fat oils contain 10
per cent, of oxygen. This oxygen, already existing in the oil, neu-
tralizes a portion of its carbon and hydrogen, so that there is really
but 85 or 86 per cent, of hydro-carbon to sustain the combustion ; and
not only this, but the other 15 per cent, of incombustible matter acts
to hinder the combustion. On the other hand, the oil of turpentine
consists of pure combustible matter, burns entirely, and contains
nothing to retard the activity of the burning process. A hundred
parts of fat-oil consume only 287 parts of atmospheric oxygen, while

116 PRODUCTIONS OF AETTPICIAL LIGHT.

100 parts of camphene consume 328 of oxygen. From its extreme
fluidity, the oil of turpentine is also supplied copiously and constantly
to the flame by the simple capillary or sucking action of the wick.

208. Why Camphene soon spoils. — Camphene, if exposed to the air,
cannot be preserved pure. It belongs to a , class of bodies known as
essential oils, which by combination with oxygen are changed into
substances of a resinous nature. Under the influence of oxygen, oU
of turpentine undergoes this change, and becomes deteriorated by
solid resinous impurities. When employed for illumination, therefore,
it should be procured in small quantities fresh from the manufacturer.

209. Nature and properties of Bnrning Fluids. — There is another
method by which oil of turpentine may be employed for illumination,
which is generally much preferred, as it avoids the liability and trou-
ble of smoke. It consists in mixing it with alcohol, so as to form
what is known as lurning fluid. Alcohol burned alone produces only
a feeble bluish-white light, as it is deficient in the necessary quantity
of carbon. It has the opposite defect of oU of turpentine, as that has
too much carbon ; the alcohol has an excess of hydrogen. By mixing
them, a compound is formed which supplies the deficiencies of both,
yields a good light, and may be burned in lamps of the simplest con-
struction. These mixtures are commonly burned with wicks, but
there is a lamp so made that the liquid is vaporized by the heat of the
burner, and escaping in jets through minute orifices, is burned without
a wick, like common illuminating gas. Owing to the large propor-
tion of expensive alcohol which must be used in making it, and which
gives but vei-y little light, burning fluid is a very costly source of illu-
mination (230).

210. In what way Burning Fluids are Explosive. — Both alcohol and oil
of turpentine are very volatile ; that is, when exposed to the air or
not confined, they rapidly evaporate or rise into the gaseous state. In
a lamp reservoir containing burning fluid, as it is gradually consumed,
vapor rises from its surface and flUs the upper space. In all vessels,
whether lamps, cans, or jugs, if but partially fllled with fluid, the re-
maining space is occupied with its vapor, which may or may not be
mixed with air. Or when exposed to the air in open vessels, vapor
rises and charges the atmosphere immediately above. Now the liquid
oil of turpentine and alcohol are both inflnitely more inflammable than
the fat oUs. These cannot be set fire to at common temperatures ;
they must be heated very hot before they will catch fire. But the
more volatile liquids, on the contrary, wiU take fire at any time
when exposed, though cold, and burn with great violence. But the

ILLTJMINATIOK BT MEAISTS OP LIQUIDS. 117

case is made much, -worse on account of the invisible vapor which they
exhale. This mixes with the air, and at the approach of the slightest
spark or flame, ignites explosively. "When pure hydrogen is mixed
with the air and ignited, it explodes with a sharp report like a pistol ;
the cause is the sudden combination of the hydrogen with the oxygen
of the air. Now when vapor of turpentine or alcohol, or any volatile
hydro-carbon is mingled with air and fired, an explosion takes place
in the same way.

211. Conditions under wMch Explosions Oficur. — The burning fluid
itself^ although excessively inflammable, is not explosive. It does not
go off like gunpowder when set on fire, nor with a sudden noise or
report, such as its vapor produces. But it is always accompanied by
the invisible treacherous gas which catches fire at a distance, and this
ignites the fluid. Most accidents that occur with these compounds
result from attempts to fill or replenish lamps while they are lit, or
where there is a light near by. The vapor of the opened lamp, jug or
can, is fired ; it explodes with more or less violence and concussion,
setting the liquid on fire, and perhaps scattering it upon the clothing
of the person present, who is severely or fatally burned, while the
house is very liable to be set on fire. If the lamp have a screw cap
and be perfectly tight, heat may be conducted downwards from the
flame through the metal, and increase the evaporation. There being
no vent but through the interstices of the wick-threads, if these are
close, the pressure wiU increase and force out the fluid and vapor so
as to burn irregularly, and sometimes occasion little explosions in the
flame. If the wick is loose, and the lamp be agitated so as to dash
the liquid against the hot screw-cap, vapor is suddenly formed, and
being pressed out the flame streams up, often producing alarm. If the
pressure become too great, and there be no vent, the lamp may ex-
plode. Dr. Hats says, it is a uniform result of numerous trials con-
nected with experiments on closed lamps, that no lamp is safe which
has a closed cap, unless there are openings for the escape of vapor.
It would be wise to substitute metallic lamps for those of glass, on
account of the danger of fracture. "When these substances are em-
ployed for light, they should not be committed to the charge of those
ignorant of their properties ; and it is the only safe rule, when they
are used in ordinary lamps, never to open any vessel containing them
when there are lights burning near by.

212. How Burning Fluids may be used with safety — ^IVewell's Lamps. —
The advantage which these liquids have over oils and candles in re-
spect of simplicity, cleanliness, and greater brilliancy of light, makes

118

PEODUCriON OF AETTPICIAL LIGHT.

Fig. 52.

it eminently desirable that some safe way be devised to consume them.
This has been done by Mr. John Newell, by applying to them the
principle of Davy's Safety Lamp. Hydro-carbon gases are often
generated in coal mines, and when mixed with common air, are
exploded by the lamp which the miners use. By surrounding these
lamps with fine wire-gauze, they could be lit and carried into the dan-
gerous mixtures without exploding them. The inside of the gauze
would be filled with burning gas, but the fine wire texture has the
efifect of cooling the flame, so that it cannot pass through and ignite
the gases outside. Hence, by ingeniously mounting his lamps with
this gauze, Mr. Newell prevents the possibility of explosion from
camphene and burning fluids. The can also for containing the fluid
has a sheet of the gauze inserted under the lid, and another fixed in
the spout. These do not prevent pouring; but if vapor or fiuid
escaping through them were lit, the flame could not enter the
vessel.

213. Eerosene Oil as an Illamiiiator. — This is a
product of the distillation of bituminous coal,
and has come lately into use as a source of
light. It is rich in carbon, and requires to be
burned in peculiar lamps adapted to its properties.
It produces a bright and beautiful light, which
we have used with much satisfaction. It does not
vaporize, and is therefore not explosive. The
proprietors make large claims on the score of its
economy (230), and are entitled to credit for hav-
ing prepared a variety of elegant lamps for burning
it. Fig. 52 represents one of their style of parlor
lamps. The cistern is narrow, and so far below
the wick as to cast but little shadow. When not
burning, the oil emits a kind of empyreumatic gas-
odor, to which many object ; but the smell is net
perceived during combustion.

214. Liglit from Sylvic Oil. — This is a cheap oil
from resin. It gives a vivid light, but it contains
so much carbon that it is difficult to burn it with-
out smoking ; this may, however, be done with

ArgandLamp for Kero- Pi'^'P^^i' care in Van Bensohoten's lamp.
Bene Oil.

rLLUMESTATION BY MEANS OF GASES. 119

4. Illttmcstation by Gases.

215, Conditions of the Gas Mannfacture. — The last source of illumi-
nation to be noticed is gas^ which gives the cheapest and brightest of
all the generally employed artificial lights. It has come into use en-
tirely within the present century, and has been very widely adopted
in cities. It was first employed in London in 1802, and its use has
extended until 408,000 tons of coal have been consumed in a single
year by the establishments of that city alone ; producing four thou-
sand millions of cubic feet of gas, and yielding an amount of light
equal to that which would be produced by eight thousand millions of
tallow candles, of six to the pound. How wonderful, that sunbeams
absorbed by vegetation in the primordial ages of the earth's history,
and buried in its depths as vegetable fossils through immeasurable eras
of time, until system upon system of slowly -formed rocks have been
piled above, should come forth at last at the disenchanting beck of
science, and turn the night of civilized man into day.

216. Materials used for making it. — Gas is chiefly produced from the
bituminous varieties of coal (87), those which are rich in the pitchy
elements containing hydrogen. It is also made from tar, resin, oils,
fats, and wood.

21Y. Products of the distillation of Coal. — If coal is used, it is placed
in tight cast-iron vessels called retorts, which are fixed in furnaces and
heated to redness by an external fire. The high heat decomposes the
enclosed coal, productag numerous gaseous and liquid compounds.
The principal products of this destructive distillation are coTce, or the
solid residue of the coal, a black oily liquid known as coal-tar ; water
or steam, various compounds of ammonia, among others that with
sulphuroiis acid, sulphuretted Tiydrogen, carbonic acid and carbonic
oxide, light carburetted hydrogen, heavy carburetted hydrogen or
defiant gas, and a small proportion of vapor of sulphur et of carbon.
There are also variable traces of many other substances.

218. Purification of the Gas. — This heterogeneous mixture is totally
unfit for illuminating purposes until purified. The liquid and gaseous
products, as they are set free, flow out from the retort through a tube
into a receiver caUed the hydraulic main, in which the liquid products
of the distillation — coal-tar and ammoniacal liquor — are to a great
extent separated from the gaseous products. But being hot they still
retain various matters in a vaporous state, which would be deposited
and clog the pipes ; these are still farther separated by passing through
the condenser, which consists of iron tubes surrounded by cold water.

120 PRODUCTION OF AETITICIAL LIGHT.

The gas is then passed through a mixture of lime and water (milk of
lime), or tlirough layers of damp slacked lime, which absorb the car-
bonic acid and sulphuretted hydrogen. It is then sometimes freely
washed with water, which removes all its ammonia, when it passes
into a large receiving vessel, the gasometer^ from whence it is dis-
tributed in pipes to the places where it is to be consumed.

219. Compositioii of Iliuminating Gas. — This is very variable, but it
mainly consists of olefiant gas, light carburetted hydrogen, carbonic
oxide, with free nitrogen and hydrogen, and sometimes other substan-
ces in small amounts. It takes its value from the proportion of olefiant
gas which it contains, as this is the chief light-producing compound.
Olefiant gas consists of 86"21 per cent, carbon to 14-79 per cent, hy-
drogen. Several other substances which burn with much light are
liable to be associated with olefiant gas, as Butylene, Propylene, vapor
of Benzole and Naphtha. Olefiant gas burns with a vrhite and re-
markably luminous flame ; but it would hardly answer to burn it alone,
as its proportion of carbon is so large, that if the combustion were at
all imperfect, there would be liability to smoke. Light carburetted
hydrogen is the same as the marsh gas, which is generated in the
organic mud of stagnant pools, and rises upward in bubbles. It con-
tains less carbon, and is richer in hydrogen ; its composition being 75
per cent, of the former to 25 of the latter. It burns with a dim yel-
low flame, giving but little light. Carbonic oxide and hydrogen both
burn with a faint blue, hardly luminous flame. Mtrogen takes no
part in the burning process, except to hinder it by diluting the gas, an
eflfect which is also produced by both carbonic, oxide, and hydrogen.
The gas that comes off from a charge of good coals consists, when the
retort is first raised to a vivid cherry-red heat, of 18 per cent, of ole-
fiant gas, 82-5 carburetted hydrogen, 3-2 carbonic oxide, and 1*3 of
nitrogen. After five hours the gas that continued to escape gave 7
per cent, of olefiant gas, 56 of carburetted hydrogen, 11 of carbonic
oxide, 21*3 of hydrogen, and 4'7 of nitrogen. Towards the end of the
operation, or after about ten hours, it contained 20 parts of carburetted
hydrogen, 10 parts of carbonic oxide, 60 of hydrogen, and 10 of nitro-
gen. The best gas therefore is that which is produced first.

220. Gas derived from other sources. — Crude and refuse oil, which is
unfit for burning, is sometimes converted into gas. It is made to
trickle into a retort, containing fragments of coke or bricks heated to
redness. The oil, as it falls upon these fragments, is instantly decom-
posed and changed to gas. It contains no sulphur products, and needs
no purification. It is very rich in olefiant gas, and has double the

ILLUMmATlON BY MEAIfS OF GAS.

121

Fig. 53.

illuminating power of the best coal gas, and treble that of ordinary
coal gas. Eesin also, by being melted and treated in a similar way,
yields a highly illuminating gas. But in point of economy, neither oil
nor resin can compete with coal as a source of light. A pound of coal
yields from three to four cubic feet of gas ; a pound of oil, 15 cubic
feet ; of tar, 12 ; and of resin, 10.

221, How Gas is measured. — Gas is sold by the cubic foot, or by the
thousand cubic feet. From the underground pipes (mains) that run
through the street, a pipe branches off leading to the dwelling to be
illuminated. Before being distributed through the house the gas is
made to pass through a self-acting instrument called a meter^ which
both measures and records the quantity consumed in a dwelling. The
meter consists of an outer stationary cylindrical case, enclosing an
inner and smaller cylinder which revolves upon its axis. Both cylin-
ders are closed at the ends, water-tight and gas-tight. The inner one
is divided into four compartments with crooked partitions, and the
gaspipe passes into its centre or axis, and, turning up at the end, de-
livers to them its contents successively. The meter is kept about two-
thirds filled with water, which the gas
constantly displaces as the cylinder turns.
The principle will be understood by the
aid of the diagram (Fig. 53), which ex-
hibits the meter as if seen endwise, with
the ends of the drums removed. A A A A
is the outer cylinder ; B B B B the four
compartments of the inner one ; c is the
gaspipe supplying one of the apartments.
As it enters the partition E rises, and the
water passes out at the slit Z>, into the
space between the two cylinders. The in-
ternal one revolves from left to right, the
gas passing in the direction of the arrows,

first displacing the water and filling the compartments, and then
passing out into the space between the two drums, where it is con-
veyed away by a tube not shown in the figure. The revolving drum
is connected with clockwork, which shows by an index the number
of revolutions made, and the capacity of the compartments being
known, the quantity of gas which passes through is correctly deter-
mined. The meter reports the amount of gas that actually passes
through it ; but its indications are by no means to be taken as infalli-
ble proofs of honesty on the part of the gas company. Their tempta-
6

Meter for measuring the flow of
Gas.

122 PEODUCnONS OP AETTFICIAL LIGHT.

tion is, to put on pressure and crowd more gas through than is neces-
sary, or than can be burned with economy, for increased consumption
of gas does not at all involve a corresponding increase of light (222).
Nor do meters afford any indication whatever in reference to the
quality of the gas ; the companies control this, and may do quite as
they please, the customer being unprotected. "We do not intimate,
however, that the gas-companies ever yield to the evil temptations
with which they are beset.

222. How Gas is 'biirned. — From the fountain of distribution — the
gasometer — the gas flows away through the branching system of tubes
under the influence of pressure. "When little openings are made in
the pipes, this pressure drives out the gas in jets or streams, and it is
these which produce the light when ignited. The orifices are from
■^-gih to the -s^ih of an inch in diameter. Eecent experiments by the
French tend to show that wider openings are more economical with
the best kinds of gas. The openings are made in various ways. A
circle of them round a large central orifice forms an Argand burner
(201). Two holes drilled obliquely, so that the flames cross each other,
produce what is called a swallow-tail jet. A slit gives a continuous
sheet of flame, called a iat-wing jet. Other flgures are also produced,
as the '■^fan-jet,'''' '■'■fish-tail jet^''"' &c. The quality of light depends much
upon the mode of burning as well as the composition of the gas ; a
good article may be spoiled by mismanagement. Its illuminating
power is impan-ed when burned too rapidly to allow the separation
and ignition of the carbon particles (190). The order of the combus-
tion, upon which aU illumination depends, is destroyed, by excess of
air, as when we move a lighted candle rapidly through the atmosphere,
the hydrogen and carbon are both burned at once, and we get only a
feeble blue flame. This occurs when gas issues with considerable ve-
locity from a minute orifice, and by expansion gets intimately mixed
with a large proportion of air. When the current of gas does not
ignite at a considerable distance (several lines) from the aperture,
and then burns with a faint blue flame, the gas-stream is too rapid, it
is improperly mingled with the air and consumes wastefuUy, — that is,
to the luyer. If chimneys are used, and the draught becomes too
strong, for the same reason the light almost vanishes, yielding only a
dull blue flame. On the other hand, too smaU a draught of air is
equally injurious, not only from incomplete combustion which causes
the flame to smoke, but also because the highest illuminating power
of the flame is obtained only when the carbon atoms are heated to
whiteness, which requires a considerable amount of air. We have

rLLUMINATION BY MEANS OF GAS. 123

before seen how rapidly light is evolved by the addition of small
quantities of heat at high temperatures (188).

223. Influence of the length of the Flame. — The dimensions of the gas-
flame may be controlled with perfect facility by simply turning a stop-
cock, although its extent depends upon the width of the orifice and
the amount of pressure. It was found that if the light from a flame
2 inches long were represented at 100, at 3 inches it became 109, at
4 inches 131, at 5 inches 150, at 6 inches 160, with an equal consump-
tion of gas in each case.

224. How mach, Gas-bnrning contaminates the AiTi-^The active source
of light in this kind of illumination, as has been stated, is defiant gas
and other compounds abounding in carbon. But these could not be
burned alone even if it were possible to procure them. A diluting
material is therefore necessary to give the flame sufficient bulk, and
separate the particles of carbon so far asunder as to prevent the risk
of imperfect combustion and smoke. Now the three substances found
in gas — light carburetted hydrogen, carbonic oxide, and free hydro-
gen— are all equally well adapted for this purpose. So far as light is
concerned, it is of little consequence which of these is associated with
the oleflant gas. But in other respects this becomes a matter of im-
portance. The two objections most commonly urged against the use
of gas in our apartments are, firsts the heat which it communicates to
the air ; and, second^ the contamination of it by carbonic acid. Now, in
these particulars, the three diluting substances have very different in-
fluences. One cubic foot of hght carburetted hydrogen consumes in
its combustion two cubic feet of oxygen, and generates one cubic foot
of carbonic acid, — a portion of the oxygen being consumed in the for-
mation of water with hydrogen. This produces a suflQcient amount
of heat, according to Dr. Feanxland, to raise 2,500 feet of air from
60° to 80"8°, while a cubic foot of hydrogen burned under the same
circumstances produces no carbonic acid, and yields heat capable of
raising 2,500 cubic feet of air 60° to 66"4°. One cubic foot of carbonic
oxide consumes in burning half a cubic foot of oxygen, and generates
one cubic foot of carbonic acid. The light carburetted hydrogen,
therefore, is the worst diluent and hydrogen the best, as it produces
no carbonic acid, and excites least heat. We saw that at different
stages of heating, the coals in the retort yielded at one time a gas, rich
in illuminating constituents, and at another time a gas deficient in
these, but rich in hydrogen (216). Advantage has been taken of this
fact to mingle the products of the retorts at different stages of heat-
ing, by which the olefiant gas is diluted with hydrogen, and a mixture

124 PEODucnoNS op aeteficial light.

produced of superior illuminating qualities and the least injurious
effects.

225. Disadvantages of Gas-lighting.^ — The chief obstacle to the use of
gas-lights in private houses is, that the burners are stationary, and
cannot be placed in positions available for all purposes. Candles and
lamps ai-e movable, but a gas-light, even where iiexible india-rubber
tubes are used, is more or less a fixture. The burners being usually
situated high for general illumination, and calculated for giving more
light than is required for one or two persons, cannot be reduced to the
limits of the strictest economy of consumption. Hence, although gas
is the cheapest of all sources of illumination, this apparent necessity
for consuming it in large quantities prevents the real saving that might
otherwise be expected. "We have just spoken of the effects of burning
gas upon the air, and shall notice it again, as also the prejudices against
its use (275).

226. Care of Gas-fixtures. — Air, when mixed with gas, exerts upon
it a slow change, tending to produce fluid and soUd bituminous bodies
by oxidation. Now if air gets access to the tubes and mingles with
the gas, as it does constantly between the burner and the stop-cock,
when the gas is not burning, the pipe becomes coated and obstructed,
and hence requires periodical cleaning, which should be done with in-
struments that ought to be furnished gratuitously by the gas com-
panies. Gas of high value contains six per cent, of its volume in
vapor, which can become fluid in the pipes when they are exposed to
the temperature of freezing water. Hence depressions in the pipes
soon collect fluids, unless they decline towards instead oi from the
meter, and the flow of gas to the burner is irregular, producing fluc-
tuation or what is called 'jumping' of the flame. When the burners
are long out of use, as sometimes in summer, the pipes are liable to
become deranged and clogged, and as gas acts on and solidifies all oily
and lubricrating substances hitherto used, the keys of stop-cocks of1;en
become fixed. — Hays. The ventilation of gas-burners will be de-
scribed when treating of air (360).

5. Measueement of Light.

227. Can Light be Measured 1 — It is sometimes of importance to de-
termine the cost of light produced in different ways and from different
materials. There is no method known by which light can be directly
measured ; that is, we have no mode of estimating the absolute quan-
tity of light emitted by a flame, but we can ascertain how much more

MODE OF ITS MEASUEEMENT.

125

Fig. 54.

or less light one flame produces than another, and thus arrive at useful
comparative results. All flames are not equally bright, — of two flames
of equal size, one may be much more brilliant and emit more light
than the other. Wo do not judge of the intensities of diff"erent lights
by direct comparison, but by the comparison of their shadows, on the
principle that the greater the flluminating power of the hght the
deeper is the shadow which it casts.

228. How Light is Measured. — Before a piece of board, covered with
unglazed white paper at a distance of two or three inches, let an iron
rod be placed which has been previously blackened by holding it in
the candle. Now if it is desired to cotnpare two lights, they are to
be placed opposite the
board at the same
height, and each will
cast a shadow upon
the paper as illustra-
ted in Fig. 54. The
lights should be so sit-
uated that the shad-
ows will fall close to
each other, and the
stronger flame should
be so far removed, or
the weaker idvauopd I'l'otometer or contrivance for measuring the intensity of ligM.

that both shadows will appear equally deep. To ascertain their
luminous intensities we measure the difierence from their centres to
the shadow : if these are equal, their illuminating powers are equal ;
but if one casts an equal shadow at a greater distance than the other,
its light must be more intense, or its illuminating power greater. The
difference in the degrees of light is not proportional to the distances
of the luminaries from their shadows, but to the squares of these dis-
tances, in accordance with the law of radiation before explained (136).
If one light at two feet, and another at six, give equal shadows, their
difference is not as six to two, but as the square of 6, which is 36 to
the square of 2, which is 4 ; that is, 36 to 4, or 9 to 1. The luminary
at 6 feet gives nine times as much light as the one at 2 feet.

229. We liave no unit for measuring Light. — This plan, modified in va-
rious ways, affords a ready means of comparing the relative amount
of light emitted by two flames. But we have not been able yet to
reap the practical advantages which this success at first appears to
promise. If we can measure light, why not establish the exact iUumi-

128 STEUCrUEE AITD OPTICAL POWERS OF THE EYE.

nating values of the various lighting materials, so that we may know
precisely how far a dollar will go in buying light when the substances
are at given prices. Something has been done in this way, but we
have no results that command implicit trust. The composition of the
materials is variable, and the same materials in different trials give
different results. "We are without an accepted unit to serve as a stand-
ard for a scale of values. It has been proposed to make the sperma-
ceti candle (6 to the lb.), burning 120 grains to. the hour, the unit of
measure. If this were satisfactory, we could compare other lighting
materials with it. A burner consuming a certain amount of gas per
hour would equal a given number of candles, and any variation in its
quality would be easily detected. "We should speak of it as 10 candle-
gas, 15 candle-gas, and 20 candle-gas, according to its gi*ade, and so
of the various illuminating substances. But these candles have been
found to burn variably, and do not perfectly answer. Some unit wiU
probably be fixed upon by which the comparative values of lighting
materials may be determined and expressed.

230. Photometric Bcsnlts of Ure and Kent.. — Dr. Fee gives the follow-
ing as the cost of an equal amount of light per hour from several
sources, according to his experiments.

Pence.

Carcel Lamp, -with Sperm Oil IJ

Wax Candles 6

Spermaceti Candles 5i

Stearic Acid Candles 4i

Moulded Tallow Candles 2^

E, N. Kent, of the U. S. Assay OflBce, experimented on various
lighting materials with the following results :

Retail price of Cost of an equal

Matei-ials. Lamp osed. Oil per gallon, amount of light.

Kerosene Oil Kerosene $1 00 $4 10

Camphene Camphene 63 4 85

Sylvic Oil Pvosin Oil 50 6 05

Eape Seed Oil Mechanical 1 50 9 00

Whale Oil Solar 1 00 12 00

Lard Oil Solar 1 25 IT 00

Sperm Oil Solar 2 25 26 00

Burning Fluid Large Wick 8T 29 00

VIII.— STRUCTURE AND OPTICAL POWERS OF THE EYE.

231. Value of the sense of Vision. — The eye is perhaps the most im-
portant organ of sense. By it the mind is put into the widest com-
munication with the external world. Although it may be said that
this organ only recognizes light and colors, yet through it we become
acquainted with the forms, magnitudes, motions, distances, directions
and positions of all objects, whether immediately around us, or re-

THE IKIS AND PUPIL, AND THEIR USES. 127

motely distributed tlirougli tlie distant universe. In its adaptation to
the agent whicli is designed to act upon it, the eye is a miracle of
beauty and wise design. For this reason alone we might well afford
to devote a little space to it ; but when we consider that it is an organ
of exquisite delicacy, and greatly liable to abuse from the domestic
mismanagement of Hght, as well as other causes, and remember how
tedious and distressing are its disorders, and what a lamentable life-
disaster is its loss, it becomes of the first importance to assist in diffus-
ing any suggestions that may lead to its better care. Our previous
study of light and colors will moreover aid us materially in forming
correct ideas upon the subject.

232. Sclerotic Coat and Cornea, and their uses. — ^When the eye is re-
moved from its socket and dissected, it is found to consist of several
coats. The outer one forms the wMfe of the eye ; it is a tough, re-
sisting membrane, and serves both to sustain the delicate parts within,
and also to give insertion to those outer muscles which roll the eye-
ball. It is called the sclerotie coat^ or briefly tJie sclerotic. As light
is to enter the eye, and as, from the nature of the organ, it could not
be admitted through a hole, it became necessary to have a wuidow in
the eye-ball. In the front part of the globe there is a circular open-
ing in the sclerotic, which is closed by a thin and perfectly transparent
membrane called the cornea, the front window of the structure. The
cornea bulges out somewhat like a watch-glass ; that is, it is more
convex than the general surface of the eye-ball, as may be felt through
the closed lid. It covers that portion of the eye which is colored, and
is attached round the edge of the colored part to the sclerotic coat,
with which it is continuous. The cornea is very hard, tough and
horn-like, the word being derived from the Latin cornu, which signi-
fies horn. The general arrangement of the parts we are describing is
shown in the accompanying view of the section of the eye (Fig. 55).

233. The Iris and Pnpil, and their uses. — Behind the cornea
there is a small space or chamber filled with a perfectly clear and col-
orless liquid, which consists chiefly of pure water, and is called the
aqueous humor. This chamber is divided by a thin partition known
as the iris, in the centre of which there is a circular aperture called
the pupil. The pupil is simply, therefore, a hole through the iris ; it
is the round black spot which we see surrounded by a colored ring.
That colored ring is the iris. It is black behind, and on the front
or visible side, it is of different colors in different individuals. The
color of the iris is observed to be, in some measure, connected with
the color of the hair. The iris has the remarkable property of con-

128 STEUCTUEE AND OPTICAL POWEES OP THE EYE.

Vtlnotii

humouf

Ch Of Old

coat

.Reti.Tia

Cornea

tracting and dilating under the influence of light, by which the pupil
is enlarged and diminished. If the light he strong, the iris contracts
and reduces the size of the pupil, so as to esclude a portion of the

light ; if the light be weak, the iris
expands so that more light is ad-
mitted. This moderates and equal-
izes the illumination of the organ,
the delicate sensibility of whicb
might otherwise be injured. The
play of this mechanism may easily
^^^^ be seen by bringing a candle near to
neni'e ~~^ the eye while gazing upon its im-

Eelation and names of the several parts age in a looking-glass. These move-

^^' ments are involuntary, the eye reg-

ulating the quantity of light it will receive, independent of the choice
of the mind.

234. Crystalline Lens and Vitreous Hnmor. — Behind the little chamber,
of which we have spoken, and bounding it on the back side, is a sub-
stance in the form of a double convex lens, called the crystalline lens.
It is situated immediately behind the pupil, very near it, is a little
larger than that opening, and is very convex, its thickness being al-
most equal to its diameter. It is supported by a ring of muscles called
the ciliary process. The crystalline has about the consistence of hard
jelly, and is purer and more transparent than the finest rock-crystal.
It is this part which becomes diseased in cataract. The space behind
the crystalline lens constitutes the main body of the eyeball, and
is filled with a clear gelatinous fluid, very much resembling the white
of es,g^ and called, from its apparent similarity to melted glass, the
mtreous humor.

235. The Choroid Coat, and how it is Colored. — There is a second coat,
lining the interior of the sclerotic, which consists of minute vessels,
arteries, and veins, closely internetted, and is called the choroid. It
extends around to the cornea, and supports the ciliaiy process. The
inside of the choroid is covered with a slimy matter of an intensely
black color, called the figmentum nigrum (blaclc pigment). This
gives to the interior of the eye a jet-black surface, which absorbs and
stifles the light, so as effectually to prevent reflection.

236. Optic Nerve and Retina. — At the back part of the eye, the scle-
rotic coat is formed into a tube which leads inwards to the brain.
This tube contains the optic nerve. As it enters the globe, it spreads
out over the inner surface of the choroid, in the form of a most deli-

THE KETINA SUPPOSED TO FEEL THE PICTURE.

129

Fig. 56.

cate network of nervous filaments, called, from its reticulated struc-
ture, the retina. The retina is therefore the extended and diffused
optic nerve. In dissection it is easily separated from the choroid. It
is absolutely transparent, so that light and colors penetrate and pass
through it perfectly, and therefore fall upon the dark surface beneath.
To prevent the delicate and transparent nerve tissues of the retina
from being stained by the black pigment, a very thin film is interposed
between them called JacoVs membrane.

237. How Vision is Produced. — From every object which we see,
rays of light pass into the eye, penetrating the successive transparent
media, the cornea, the aqueous humor, the crystalline lens, and the
vitreous humor, and falling upon the retina, form there an image of
the visible object, the impression of which is carried by the optic
nerve to the brain.
The diagram (Fig.
66) shows how, in
the perfect eye, the
image is made to
fall accurately upon
the retina. It is
seen to be inverted.
The pictures in the
eye, of everything
we behold, are upside down, although there is no confusion, and we
are unconscious of it. "We have said that the image is formed upon
the retina, and this is the common mode of expression, but that is
perfectly transparent, so that the colored image is formed, not proper-
ly ti2:>c>?i it^ but upon the black surface of the choroid coat behind it.
It is maintained that the retinal membrane is affected by the colored
image in the same manner that the sense of touch is affected by ex-
ternal objects. It is supposed to touch or feel, as it were, the image
on the choroid, and transmit the impression to the brain, something
in the same way that the hand of a blind person transmits to the or-
gan of consciousness, the form of an object which it touches. This
view seems to be confirmed by the fact, that at that portion of the
retina where the optic nerve enters the eyeball, which therefore has
not the black choroid behind, it is insensible, and produces no per-
ception. It has been proved by experiment that images made to fall
upon that spot, are instantaneously extinguished.

238. Wonderful Minuteness and Distinctness of tlie Images.— Nothing
is more calculated to awaken our astonishment than the perfect dis-

6*

How the Images are formed in the perfect Eye.

130 STEUCTUEE AND OPTICAL POWEES OF THE EYE.

tinctness of the pictures upon tlie retina, compared with their magni-
tude. The diameter of the picture of the full moon upon the retina
is but the 2I0 P^^* of an inch, and the entire surface of the picture is
less than the ^-aWo P^^* ^^ ^ square inch. And yet we are able to
perceive portions of the moon's disc, whose images upon the retina are
no more than the 15,000,000th part of a square inch. The figure of a
man 70 inches high, seen at a distance of 40 feet, produces an image
upon the retina the height of which is about the yV part of an inch.
The face of such an image is included within a circle whose diameter
is about Yz *^f ^-^^ height, and therefore occupies on the retina a cir-
cle whose diameter is about ^\ part of an inch ; nevertheless, within
this circle, the eyes, nose, and lineaments are distinctly seen. The
diameter of the eye is about —^ that of the face, and therefore, though
perfectly visible, does not occupy upon the retina a space exceeding
the l-4,000,000th of a square inch. If the retina be the canvas on
which this exquisite miniature is delineated, how infinitely delicate
must be its structure, to receive and transmit details so minute, with
such wondrous precision ; and if, according to the opinion of some,
the perception of these details be obtained by the retina feeling the
image formed upon the choroid, how exquisitely sensitive must be its
touch. (Lardnee.)

239. Adaptation of the Eye to Intensities of Light. — The susceptibility
of the eye under great variations of intensity in the light which en-
ters it, is most wonderful. We can read a book either by the light of
the sun or of the moon, yet sunlight is more than a quarter of a mil-
lion times more brilliant than moonlight. "The direct light of the
sun has been estimated to be equal to that of 5,570 wax candles of
moderate size, supposed to be placed at the distance of one foot from
the object. That of the moon is probably only equal to the light of
one candle at a distance of twelve feet, hence the light of the sun is
more than 300,000 times greater than that of the moon." "WoUaston
estimated the light from Sirius, one of the largest fixed stars, as twenty
thousand million times less than that of the sun.

240. Conditions of the System aflfect the Eye. — The eye is thus an opti-
cal contrivance which challenges our wonder continually for the ex-
quisite beauty and perfection of its parts. Yet we must not forget
that it is a living organ of the body made up of vessels, membranes,
muscles and nerves, and nourished by the vital blood-stream like any
other organ. It is therefore liable to be influenced in numberless
ways by conditions of the system. When in use, it acts, expends force,
exhausts itself and becomes fatigued. Dr. Wharton Jones remarks :

STATES OF THE BODY AFFECTING THE EYES. 131

" Much exertion of the eyes operates more prejudicially to the sight
under some circumstances than under others. Exertion of the sight
is especially prejudicial immediately after a full meal; after the use of
spirituous drinks ; while smoking ; when the body is in a recumbent or
stooping posture, when dressed in tight clothing, especially a tight
neckcloth ; tight corsets ; and even tight boots or shoes ; in close and
Ul-ventilated apartments lit with gas ; after bodily fatigue ; during men-
tal distress ; late at night when sleepy ; after a sleepless night ; while
the bowels are much confined ; during convalescence from debilitating
illness. Though during recovery from severe disease the eyes cannot
bear much exertion, yet, for want of other employment, it is not un-
common for convalescents to read even more than when in health.
Many persons have much injured then* sight in this way. Young
growing persons, at the age of puberty, persons of weakly constitu-
tions, are incapable of supporting much exertion of the eyes without
injury to the sight." Sudden suppression of the perspiratory action
of the skin, or any cause which determines a pressure of blood to the
head, is also liable to afi'ect the eyes injuriously,

241, Beading and Writing. — In this reading age, with such strong
and insidious temptations to overuse and bad management of the eyes,
it may be well to make some suggestions concerning this mode of
exercising vision. The closer the eye is confined to the page, the
more of course it is strained, Novel reading is worse than science,
history, or any grave subjects, because in the first instance we read
fast and uninterruptedly, while in the latter cases thinking alternates
with the use of the eyes in reading. Eeading from a broad page with
the lines long and the print small, is very tiresome, as it is difiicult
for the eye always to take up the next line. "Writing down our own
thoughts is easy for the sight ; but copying is hard, as we have both
to read and write, and look backward and forward in addition.
Eeading when in motion, as in riding or walking, or in the brightness
of sunshine, or under a tree, where from the motion of the leaves by
the wind lights and shadows fly over the page, are all severe upon the
eyes, and liable to injure them. But perhaps the most serious mischief
to which we are exposed in reading, comes from the bad quality of
artificial light, which we shall notice particularly farther on.

IX.— OPTICAL DEFECTS OF VISION— SPECTACLES.

243. Limits of perfect Vision. — The transparent portions of the eye,
the cornea and included humors, act as lenses (149), which bend or
refract the light from its straight course as it passes through them,

132

OPTICAL DEFECTS OF VISION — SPEOTACLES.

Fig. 57.

bringing it to a point or focus at the back of the eye. TVTiere the
vision is perfect, the rays are so bent that the image, in its utmost
distinctness of outline and color, falls exactly upon the retina, as shown
in rig. 56. If the eye were a fixed or rigid mechanism, as if made
of glass, only objects at certain precise distances would come to a
point upon the retina, all others would produce their images either
before or behind it, and thus give rise to imperfect vision. But the
organ possesses a power of adjustment by which objects at different
distances may be seen clearly. How this occurs ia not understood.
Perhaps the crystalline lens is capable of slightly varying in position
and curvature. The limits of perfect vision in the normal eye vary
somewhat in different persons ; but in general they may be put down
as between nine and fifteen inches.

243. Cause of Far-sightedness. — -The eye is a system of lenses beau-
tifully arranged to bend light to a point. But its bending or con-
vergent powers may be too MgTi or too low^
producing imperfect vision in either case.
This converging or refractive power de-
pends upon the curvature of the lenses.
The rounder they are, the stronger they are ;
the flatter they are, the weaker they become.
"^%i^v ■^^ persons advance in life, there is a ten-
dency to loss of fluids, which fill and dis-
tend the body, and a consequent shrinking
of the flesh and wrinkling of the skin. Th(
Far-sighted Eye^^witli flattened ^y^ participates in this natural change of
tissue, its contents seem to shrink, and the
cornea becomes flattened or loses something of its convexity, appear-
ing as shown in Fig. 5Y. This -pvodnces far-sightedjiess, in which per-
sons can see objects distinctly only when they are at a very consider-
able distance from
the eye, such as
holding the book
at arm's length in
reading. In this
state of the eye
the rays tend to a
focus at a point

behind the retina,
Far-siKhted Eye — the focal point thrown too far back. , . -, ,■■

° ■' ^ on which, there-

fore, they strike in a scattered state, forming an indistinct image. In

Fig. 58.

COEEECTION OP FAE-SIGHTED EYES. 133

Fig. 58 the object a has its focal point thrown back to 5, making a
confused picture upon the retina at c. The further an object is from
us, the less divergent or more parallel are the rays coming from it ;
and the less divergent are the rays vyhich enter the eye, the easier are
they brought to a focus by it. This is the reason that to the far-
sighted, distant objects are distinct, and near ones confused. The far-
sighted see minute objects indistinctly at every distance, because when
near they are out of focus, and when remote from the eye, they do not
reflect sufficient light to make a strong impression. They hence strive
to increase the light upon the object, as we often see when attempting
to read by candlelight, they place the candle between the book and
the eye, and both at arm's length. It is but rarely that eyes recover
naturally from this defect, yet much may be done to preserve the
sight by care. When the eyes begin to fall, all over-exertion, as
minute work or reading by badly arranged artificial light, should
be avoided. As soon as the eyes begin to feel fatigued or hot they
should have rest.

244. How Glasses help the Far-sighted. — The remedy for this defect
is convex lenses, which are so selected and adapted to the eye as ex-
actly to compensate for the want of refracting power in the organ
itself. These len- -^^^ 5g_

ses gather the rays
to a point at vari-
ous distances de-
pending upon their
curvature. The
greater the curve,
the nearer the fo-
cus and the higher
the power • while Far-sighted Eye corrected by double convex glasses,

with less curvature, and a more distant focus, there is lower power.
The refractive power of a glass is expressed by the distance of its
focal point in inches. A 10-inch glass, or a No. 10, collects the rays
to a point at a distance of 10 inches, a No. 5 at 5 inches, and a No.
20 at 20 inches. The higher numbers express the lower powers, and
the lower numbers the higher powers. Fig. 59 shows the far-sighted
eye, with its internal focus, properly adjusted by a convex glass.

245. Management of far-sighted Eyes. — "When the sight begins to fail,
and glasses are sought, those of the lowest power, which wiU bring
objects within the desired distance, should be chosen. But they
should be comfortable and not cause headache, nor strain or fatigue

134

OPTICAL DEFECTS OF VISION — SPECTACI^S.

the eyes ; if they do this, they are too convex. If practicable, it is
well to get two or three pairs from the optician, as nearly correct as
possible, and try them leisurely at home before deciding which to take.
If the eyes only see clearly at a wry great distance, the No. of the
glass required will be the same as the number of inches at which it is
desired to read. But the moderately far-sighted do not require such
strong glasses. If they can see small objects distinctly at 20 niches
distance, for example, and wish to be able to read at 12, the power of
the desired glass may be obtained by multiplying the two distances to-
gether, and dividing the product, 240, by the difference between them,
viz. 8 ; the quotient, 30, is the focal length in inches of the glasses re-
quired. The intensity of the light influences the power of the glasses
used ; it is commonly found that those a degree more convex are re-
quired by artificial light, than by daylight. Many suppose that glasses
of certain focal lengths correspond to certain ages, but no rule of this
kind is safe. The nearest average relation between the age and the
focal length of the convex glass is as follows:

Age in Tears 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90.

Focal Length in Inches...... 86, 30, 24, 20 16, 14, 12, 10, 9, 8, T.

246. Near-sightedness. — This is the opposite defect; the cornea is
too rounded and prominent, as shown iu Fig. 60. The rays of light
which fall upon it are consequently too powerfully refracted, and ar-
riving at a focus before reaching the ret-
ina, cross, and are in a scattered state
when they do fall upon it, as illustrated
in Fig. 61, where a is the object, 5 the
focus, and g the confused rays falling
upon the retina. In this condition of
vision, persons can see objects with per-
fect distinctness only when they are at a
short distance from the eyes ; if they
_ bring minute objects closer than ten

Near-sighted Eye, with its Protrud- inches they are usually accounted near-
ing ornea. sighted. By bringing the object nearer

it is distinctly seen, because the rays of light from it which enter the
eyes, being more divergent than when it was distant, are not so soon
brought to a focus. The near-sighted eye retains its power of adjust-
ment to distances ; the nearest distance may be from 2 to 4 inches,
while the greatest is from 6 to 12. Short-sighted people see minute
objects more distinctly than other people, because from their nearness

Fig. 60.

COEEECnON OF NEAE-SIGHTEDITESS.

135

Fig. 61.

they are viewed under a larger angle and in stronger light. They can
see better than others with a weak light, and hence can read small
print with a feeble illumination. To persons who are occupied with
minute objects, short-sightedness, unless extreme, is rather an advan-
tage, as they can
observe all the
details of their
work very ac-
curately, while
for distant vis-
ion they can get
ready help from
glasses. Yet if
an eye be at first

Near-sighted Eye, the focus falling too far forward.

perfect, the constant employment of it upon small objects tends to
produce near-sightedness, which is hence a common defect of vision
among the educated classes, and those who do much minute work.
On the contrary, the habitual exercise of the eyes upon distant objects
improves their power in that direction. If young persons have a ten*
dency to nearness of sight, and are designed for vocations in which
lengthened vision is required, they should avoid much exertion of
the eyes on small objects, and exercise them frequently in scenes in
the open country. It is an error that the near-sighted acquire perfect
vision as they advance in life. "We often see old people who are com-
pelled to use near-sighted glasses ; indeed, this state of the eyes some-
times occurs in old persons whose vision was previously at the usual
distance.

247. Management of Near-siglitedncss. — Concave glasses extend the
vision of the near-sighted by separating or diverging the rays of light
before they enter
the eye, so that
they may be less
quickly brought
to a focus, and
the image formed
further back, as
shown in Fig. 62.
The powers of

. J? j.T^ " Near-sighted Eye, corrected by double concave glass.

near-sighted are expressed in a manner contrary to those for the far-
sighted (245). They are numbered 1, 2, 3, &c., No. 1 having the

Fig. 62.

136 OPTICAL DEFECTS OP VISION — SPECTACLES.

smallest convexity and the smallest power, and being therefore adapted
for those that are least near-sighted. In selecting glasses, the near-
sighted should choose the lowest or weakest powers that will answer
the purpose, and the best plan is to make trial of a series, as was sug-
gested to the far-sighted. If the glasses make objects appear very-
bright, or glaring, or small, or produce fatigue, strain, or dizziness and
confusion of vision after being laid aside, they are too concave. If
glasses are wanted for reading or to behold near objects, the power of
the required glass may be determined as foUows : Let a person multi-
ply the distance at which he is able to read easily with the naked eye,
say four inches, by the distance at which he wishes to read, say 12
inches, and divide the product, 48, by the difference between the two,
which is 8 ; the quotient, 6, is the focal length of the glasses required.
The far-sighted have to change their glasses as the sight progressively
fails, but near-sightedness usually continues much the same through
the greater part of life, so that the same glass gives assistance a much
longer time. It is well for both the far-sighted and near-sighted to
employ glasses of various grades for different purposes. Thus the
near-sighted need glasses adapted to distant objects, and as they are
much inclined to stoop in reading and writing, they might remove the
eye further from the page by using glasses of slight concavity. ISTear-
sigbtedness may be occasioned by other causes than the one just no-
ticed. There may be a declining sensibility of the retina, which makes
it necessary to bring objects nearer to the eye ; this is called nervoits
sTiort-sightedness, and although objects are seen better close by, yet
they are not seen so distinctly as in true or optical short-sightedness.
Such persons seek strong light, to get a more vivid impression, and use
convex glasses to increase the light upon the retina. This use of glasses
is perilous (266). Short-sightedness is sometimes a symptom of com-
mencing cataract. This disease is not, as is commonly supposed,
something growing over the sight on the outside of the ball. It is a
change in the crj'stalline lens, by which it loses its transparency, and
becomes more or less opaque, so as to confuse, scatter, or stop the
light, and destroy the distinctness of the image. Children often shorten
their vision at school by stooping over their desks and poring over
bad print, combrued with the debihtating action of extreme heat and
bad air, a result which should be carefully guarded against by parents
and teachers.

248. Important Suggestions in selecting Spectacles. — "Whatever be the
defects of vision which spectacles are designed to remedy, there are
certain points which should always be observed, both by the maker in

SUGGESTIONS COKCEENING SPECTACXES. 137

mounting the glasses, and by the buyer in selecting the frames. It ia

essential that the lenses be so framed that their axes shall be exactly

parallel, so as to couacide with the axes of vision when the eyes look

straight forward. Frames are often made so light and flexible as

readily to bend in clasping the head, so that the glasses cease to be in

the same plan, and then- axes lose their parallelism. This is shown in

Fig. 63, where the axes of the len-

ses, c (?, instead of comciding with

the axes of vision, a &, are altered in | /

their direction, and become conver- :;

gent. Again, the most perfect vision Y''''~°'''''''f=^aaagB-__-a,»g

with spectacles is produced when the / / i

eye looks through the centre, or in / / ■

the direction of the axis of the \ ^ h

lens. Where the eye turns from the I

axial centre of the glass, and looks I j

obliquely through it, the view is less \ /

clear and perfect. For this reason \ /

persons wearing spectacles general- \ - /

ly turn the head, where those with- Tie axes of the glasses, c <f, should coin-
'' ' cide with the axes of vision, a o.

out them generally turn the eye.

The distance between the centres of the lenses should be exactly equal
to the distance between the centres of the pupils. As the clearest vision
is through the centres of the glasses, the eyes wiU have a constant
tendency to look in that direction. Hence, if the lenses be too far
apart, the eyes, in striving to accommodate themselves, will acquire a
tendency to an outsquint ; whUe if the glasses are too near together,
there will be, for a similar reason, a tendency to an insquint. The
frames should not only correctly adjust the glasses, but should main-
tain them firmly and steadily before the eye. The lenses should be
free from veins or small bubbles, be ground to an exact curvature, and
be perfectly polished and free from flare, or what is technically called
curdling. "What are called 'pebble-glasses,' or 'pebbles,' are some-
times used ; they are cut from Brazilian rock-crystal, and have the ad-
vantage of being more transparent than glass ; they are also much
harder, do not scratch, take a higher polish, and consequently trans-
mit more light.

X.— INJUKIOUS ACTION OF ARTIFICIAL LIGHT,

249. Artificial Light not White, but Colored.— Artiflcial light differs
from daylight in composition ; it is colored, while dayhght is of a pure

138 INJTJEIOUS ACTION OF AETEPICIAL LIGHT.

■wMte. We have seen that white light is a compound, consisting of
three simple colors, red, yellow, and blue (159). There is no means
of positively determining the proportion in which these colors combine
to produce white, although it is commonly stated to be, red 5, yellow
8, blue 8. Whatever may be the measured quantities in which they
combine, we know that any disturbance of those quantities destroys
whiteness and produces a colored light. Now our common artificial
lights are not really white ; they appear so from want of a pure white
to contrast with them. They are more or less deficient in blue, and
consequently appear of the tints which result from a mixture of what
remain, yellow and red ; these combined produce orange, so that arti-
ficial luminaries produce in a greater or less degree yellow or orange-
colored light.

250. How the fact may be shown. — To become assured of this fact,
it is only necessary to observe both daylight and candlelight under
circumstances favorable for comparison, which may be done in the
following manner. If a lighted candle be placed in a bos, with a
round hole cut in one side so that the rays may pass through and form
a luminous circle on a sheet of white paper ; and if then a second
luminous circle be formed on another part of the paper by a beam of
daylight admitted through an opening in a closed window-shutter, the
orange- yellow tint of the candlelight, contrasted with the whiteness
of the other circle, will then be strikingly apparent.

251. Order of deviation of different Lights from Whiteness. — ^The red-
colored light is produced by the slowest and most imperfect combus-
tion (188) ; as the burning becomes intenser orange and yellow appear,
and lastly, at the highest temperature, blue, which by mingling with
the other colors produces whiteness. The different illuminating sub-
stances yield lights of various tints, from a dingy red up to white, ac-
cording to their composition and the various circumstances of combus-
tion which we have noticed. Dr. J. Hunter arranges the lights of
illuminating substances as degenerating from whiteness nearly in the
following order. Oil-gas, naphtha ; sperm oil ; coal-gas from the
best coal ; wax, spermaceti, and stearine candles ; vegetable oils ;
moulded tallow candles ; coal-gas from inferior coal ; coarse oil and
dipped tallow candles. Oamphene and kerosene oil wUl probably
rank with the best gas, and a good quality of burning fluid with
spermaceti candles.

252. Alteration in Colors seen by Artificial Light. — It is well known that
colors appear differently when illuminated artificially than when seen
by daylight. This is a necessary consequence of the difference in the

ITS EFFECTS UPON THE EYES. 139

rays wMch fall upon them. As sunlight contains a large proportion
■of hlue rays, and artificial light an excess of yellow rays, they must
inevitably influence the color of surfaces in a different manner. In
artificial light green has a yellow hue, and blue turns green from the
excess of the yellow rays ; dark blue becomes purple and nearly black ;
orange, by reflecting its own constitutent rays, appears very bright ;
yellow appears white, from there being no really white light to con-
trast it with, and red has a tawny color from the excess of yellow ; at
the same time all the colors except the orange are much impaired in
brilliancy, and many of the deeper shades become quite black and
sombre, from there not being any pure white light reflected from their
surfaces, as in daylight, when even the gravest colors have a remark-
able degree of clearness and purity. Of course the appearance of
colors by artiflcial light will depend directly upon its quality. The
whiter and purer and nearer to daylight it is, the more bright and
natural will they be ; whUe the more colored and dingy the light, the
more chromatic disturbance and perversion will it produce.

253. How Artificial LlgM affects the Eyes. — But the eye itself is
affected by the use of artificial light, as is shown by the following
simple experiment, suggested by Dr. James Hunter. " Tie up the
left eye, and with the other look steadily and closely for about a
minute at some small object placed upon a sheet of white paper, and
strongly illuminated with ordinary daylight, but not exposed to the
direct rays of the sun ; then uncover the left eye and look at some
distant white object or surface, such as the celling of the room, first
with the left eye and then with the right. It wiU be found that there
is not much difference in its appearance as seen by one eye or by
the other, though in general it will be a very little brighter to the left
eye. After this, darken the room by closing the shutters, tie up the
left eye again, and then with the right one look at the same object
placed on a sheet of white paper as formerly, but illuminated by a
large tallow candle or oU lamp, so that it shall be seen as distinctly as
it was in daylight. Keep the right eye fixed on this object for about
a minute, so as to examine it closely and narrowly, then extinguish
the candle or lamp, open the shutters, and uncover the left eye.
"When both eyes are now turned to the ceiling, it wiU appear some-
what dim and indistinct ; and on looking at it first with the one eye,
and then with the other, the difference will be very remarkable. To
the left eye, which had not been exposed to the action of the artificial
light, it wiU appear unchanged, or sometimes of a pale yeUowish-
white color ; but to the right eye it will be very dim and of a darh

140 INJUpiOUS ACTION OF AETIFICIAL LIGHT.

hlue or purple color. The effect produced npon the right eye in this
experiment soon goes oif ; and though it always takes place to a cer-
tain extent when artificial light is used, it is not much observed,
because as both eyes are equally affected, the contrast is not very
striking. But if any one will read or write by candlelight for some
hours with one eye closed, he will be rendered fully sensible of its
very injurious action, when he afterwards compares the state of one
eye with that of the other.

254. Explanation of these eflTects. — We shall understand these effects
by recalling what has been said of complementary colors (173). "When
the nerve of vision is exposed to a colored light, it is unequally excited.
The equilibrium of its action seems to be disturbed. It becomes less
sensitive to the observed color, and when the eye is afterwards turned
to white objects, they do not appear white but tinged with the com-
plementary to the one seen first. The continued action of one color
seems to paralyze the retina to its influence, and produce an unnatural
sensibility to the other colors, which, combined with that, compose
white light. In the preceding experiment, the eye, stimulated by
candlelight, in which orange-yellow is in excess, temporarily lost its
power of discerning white, and saw in it only the complementary of
orange-yellow, blue or dark violet.

255. How this may injnre the Retinai — Now the effect of this over-
stimulating the nerves of vision through excess of red and yellow
r^s, on the jjart of those who use their eyes much by artificial light,
is often to produce at certain points of the retina a total insensibility
to those rays. The consequence of this is, that in daylight dark films
of a blue or purple color, which are complementary to the orange or
yellow color of the artificial light, appear before the eyes. The pecu-
liar color of these films is not very obvious, unless they are seen in
contrast with a yellow or orange surface, and over them they appear
very sombre and almost black ; because, in the peculiar state of the
eye that gives rise to their appearance, there always coexists a certain
degree of diminished sensibility to all the rays composing white
light.

256. Popular recognition of the effect of different Colors. — There is a
difference in the effect of different colors upon the eye, which is
generally recognized and variously expressed. Thus blue is said to be
a very soft, cool, retiring color ; green is cool, though less so than
blue ; yellow is warmer and advancing ; orange still Avarmer, and red,
fiery^i JiarsTi^ and exciting. This agrees with the view which regards
blue and green as least hurtful, and yellow, orange and red as more

ITS ASSOCIATED HEAT. 141

irritating and injurious to tlie eyes. An explanation of these different
effects is found in the wave theory of light and colors, which has
been previously noticed (155). Vibrations of the red ray are larger
and more forcible than those of the yellow, and the yellow than those
of the blue, just as the large and slow heavings of a swell upon the
ocean are more violent and irresistible than the smaller and quicker
ripple-waves.

257. Heat aceompanying Colors — The above current phrases in refer-
ence to the coolness and warmth of color, correspond perfectly with
the distribution of measured heat among the several colors of the
spectrum. We all know that heat is associated with light ; but it is
not equally associated with each color that composes the light.
When the colors of the sunbeam are separated and spread out as in
the spectrum, it is found that the heat is least intense at the blue, and
constantly increases through the green, yellow, orange, and is most
intense in the red color. Thus Englefield found that while the blue
rays were at a temperature of 66°, the yellow were at 62°, and the
red at 72°. Thus the orange and red of common artificial light are
actually more fiery and exciting than the absent blue rays. This ac
companying heat is apt to be much more injurious in artificial than in
natural light. The sun's rays are seldom, if ever, allowed to fall
directly on a near object on which the eyes are to be employed for
any length of time, without having previously undergone repeated
reflections from the atmosphere and clouds, or from the surface of the
ground and walls and furniture of the apartment, which absorb a
great portion of their accompanying heat. But owing to the non-
diffused and concentrated character of artificial light, the rays must
be generally allowed to fall directly on the object looked at, from
which they are reflected to the eye along with nearly the whole of
their accompanying heat.

258. The Lnminons Matter being imperfect, more must l»e used. — The
luminous effect, or as it is termed the defining power of light, that
quality by which we are enabled to see minute objects with the most
distinctness and ease, is much less in artificial light than in the white
light of day. This lower defining power of orange-colored light
makes it necessary to increase the amount of the inferior rays ; we
attempt to compensate for deficient quality by excess in quantity. In
reading by daylight the black ink is strongly contrasted with the pure
Ivhite paper ; but by artificial light, as the paper has an orange or yel-
low hue, the contrast is not so marked, and so to aid vision, the quantity
of light is increased. In severe, long-continued, and nightly exercise,

142 kstjurious action of aetificial light.

as in reading, writing, sewing, type-setting, &c., the injurious conse-
quences of impure light are apt to be heightened by its excessive use,

259. Carbonic Acid affects the Eyes. — Sunlight does not poison the
air, artificial light does. In proportion to its brilliancy and abundance,
the insidious narcotic agent, carbonic acid gas, is generated and set
free. The effects of breathing this substance wiQ be described when
treating of the air and ventilation (293) ; but it may be remarked, that
by its special influence in deranging and disordering the nerves, it is
fitted to concur with those influences which impair the action of the
retina.

260. Unsteadiness of Artificial Light Injnrions. — Sunlight never wavers
or flickers ; its action upon the eye is equable and unvarying. But in
artificial illumination, as it is impossible perfectly to regulate the sup-
ply of air and of combustible material, the light is fiickering and un-
steady. The glass chimney of the Argand burner, however, produces
the most constant and unchanging flame. The bad effects of these
sudden and continual alterations in the brightness of artificial light,
may be shown by supposing that a minute object can be seen in light
of 8, 9 or 10 degrees of intensity, but that the intermediate degree of 9
is best .Now if sunlight be used, as it flows in a perfectly uniform man-
ner without sudden variations, the retina and pupil adapt themselves
to its quantity, and the eye may be long used without fatigue. But if
artificial light of 9 degrees be used, it may at one moment rise to 10,
and at the next fall to 8 degrees, from the fiickering of the fiame, so
that the retina and pupil have not time to accommodate themselves to
the change, and a degree of temporary blindness or impaired distinct-
ness of vision, results, which is very straining and fatiguing to the
eye. To remedy this, the light is increased in intensity. If it be
raised, say to 14 degrees, then it may be reduced to 13 or rise to 15
degrees, without immediate inconvenience to the eye ; there being
abundance of light, its variations are less sensible. This relief, how-
ever, is fraught with iiltimate danger ; for the retina is too much
excited by this increase of one-half in the quantity of light admitted
to it ; and this state of excitement is but the prelude to an opposite
state, in which the sensibility to light is greatly, and perhaps perma-
nently diminished (265). Unsteadiness of the object viewed, if the
eye be long and closely directed to it, is a source of injury. It is thus
that much reading in railroad cars, where the trembling or incessant
movement of the print keeps the image in constant motion upon the
retina, has a bad influence upon the eye.

261. All Light iiyarions but that from the objects viewed. — The distinct-

THE EYE BLINDED BY EXTEANE0U8 BAYS. 143

ness of vision is interfered with, and the eyes made to suffer by an-
other important circumstance — tlie admission of light into the eye
from other sources than objects to which sight is directed ; in other
words, the introduction of extraneous light into the eye. Impres-
sions upon the retina may be diminished and obliterated by other
rays falling upon it, which excite the nerve more strongly. The moon
at night, as we all know, produces a vivid impression upon the nerve
of visual sense. It produces precisely the same impression in the
daytime, but then the luminous image is extinguished by the over-
powering light of the sun, so that we are not conscious of it. "Wlien
we are using the eyes upon any object, all light which enters them,
except from that object^ is injurious ; that is, it has a blinding effect.
This is shown by the greater clearness of objects seen through a tube,
where aU the diffused and side-light is excluded, on the same principle
that persons see stars from the bottom of a weU in the daytime.* Or it
may be shown in another way. Let a person stand before a gas-light
in such a position, that in reading a book a considerable number of
the direct rays from the flame shall enter the eye. Let him then
cautiously reduce the light by turning the stop-cock until the letters
can be no longer distinguished. If he now shade his eye by inter-
posing his hand or a screen, so as to cut off the direct rays, the words
will again become visible, and again disappear when the hand or
screen is removed. This proves that when the eye is protected from
the direct rays, small objects can be seen with less light, and conse-
quently with less injury to the nerve of vision.

262. PreTalence of this source of injury. — Upon this point Dr. Hun-
tee remarks : " Though the injurious action of artificial light, in con-
sequence of its improper position, can be easily obviated ; it is aston-
ishing how little it is attended to, and how generally it is in operation.
For the express purpose of satisfying myself on this point, I have
visited a great many workshops, printing-houses, tailors' rooms, and
other places, and in almost every instance I found the artificial lights
placed close to, and directly opposite the eyes of those engaged in fine
work, requiring the excessive exertion of the sight, and frequently the
mischief was increased by concave metallic reflectors, placed behind
instead of around the light. Now that gaslight is so generally em-
ployed, its improper position is a most serious evil : for as its intensity
can be so easily increased in proportion as the sensibility of the eye
becomes impaired, few persons, particularly those who are igno-
rant of the harm they are doing, can resist the temptation to use a

♦ Humboldt, however, questions if stars are ever thus seen.

144 IN^JUEIOUS ACTION OF AETIPICIAL LIGHT.

stronger and stronger light, till at last their eight ia permanently
weakened or even quite destroyed."

263. Bad Light may inflame the Eyes. — The continued action of im-
proper light upon the eye is liable to inflame it. The first symptom
is a reddening of the lining membrane of the eyelids, which in health
is of a white or pale rose-color. This may be observed by gently
drawing down the lower lid, when its surface will be seen injected
with blood and of a deep red color. At first there may be but little
uneasiness in the daytime, but at night, when the eyes are employed
on objects illuminated by a candje, they become hot, watery, and
irritable, the lids feeling dry, stifi", and itchy, and causing the patient
constantly to rub them. The dryness, after a time, may give place to
a copious flow of burning tears, which suffuse the eyes, and pour over
and scald the cheek. Sometimes there is an excess of gummy and
adhesive secretions, which dry at night and glue together the lids so
hard as to require long bathing with warm water before they can be
opened. If this incipient inflammation be unchecked, it may increase
and run on to various forms of disorganization, or it may take the
shape of a chronic or unmanageable afiection of the eyes without pro-
ducing blindness.

264. Unnatural increase in the sensibility of the Retina* — In the preced-
ing case, the disease is located in the external or image-forming por-
tions of the eye, but the bad management of artificial light is apt to
engender a far more dangerous and intractable form of disease, which
fixes itself upon the image-feeling parts — the retina and optic nerve.
The excessive use of impure light, by its unequal action, excites and
stimulates the nerves of vision, producing an unusual irritability to
light, and a low degree of inflammation of the retina. Moderate light
becomes unpleasant, and the individual, after looking steadily at some
object for a few minutes and then closing the eyes, or putting out the
light, appears to see still before him quite a distinct representation or
image of the object, which may last for two or three minutes, and be
variously colored or pass through a succession of colors. It moves,
but its motions are in opposite directions to those of his eye, for it
passes upwards when he looks downwards, and sinks downwards when
he rolls his eyeballs upwards. It is caused by the morbidly increased
sensibility of the retina, which retains the impressions of light for a
greater length of time than when it is in a healthy condition. This
state of the eye is accompanied often during the daytime by a dull,
heavy feeling in the forehead, hardly amounting to pain, but causing
the patient frequently to pass his hand across his brow, and ia read-

ITS MOEBID EFFECTS UPON THE EETTNTA. 145

ing or writing at night, there is an unpleasant sense of distension in
the or hits, with an increased flow of tears and frequent twittering or
quivering of the eyelids. BriUiant flashes of fire are seen, particu-
larly when the eye is touched, on lying down, and after reading, writ-
ing, or sewing for some time by artificial light.

265. Decrease in nervons sensibility— Appearance of dark films. — This
condition of excessive irritability may continue for months, and then
be followed by others totally different, and indicating a diminished
sensibility of the nerves of vision. This is evinced by the appearance
of dark spots or films floating in the air. At first but one film appears
before each eye, which is seen only for a moment, and then darts away,
shortly to reappear. But afterward their number is increased, they
appear oftener, are larger, darker, more opaque, and continue longer
visible than at first. They sometimes look like cobwebs, or flakes of
soot, or bunches of fur-down. They often resemble large-sized leaden
shot, or minute and transparent globules, looking lite drops of oil upon
the surface of water, and, connected with each other like the links of
a chain, float slowly through the air. These appearances are known
by the doctors as musece wUtantes; they are probably connected with
morbid conditions of the nerves, but how we do not know.

266. Paralysis of the nerve of vision — imanrosis. — These appearances,
in their less marked form, are quite common, many eyes being subject
to them, and they may occur for a long time without getting worse,
and unaccompanied by positive disease. But when they appear as a
dense, opaque, stationary film, which interrupts and obscures vision,
the symptoms become very alarming ; there is danger of palsy of the
retina producing nervous blindness, or amaurosis. To the casual ob-
server, the eye, under the influence of this malady, appears perfectly
well, there being no external evidence of disease. But when once
seated, its effects may be seen in the irregular shape of the pupil,
which loses its roundness while the motions of the iris under the in-
fluence of varying light, become sluggish and imperfect, or are alto-
gether lost. Objects appear clouded in a thick mist, and the air some-
times seems filled with sparkling, glittering points. In the final
stages of amaurosis the pupil is very much dilated, the sight is impaired
or quite gone, and the eye has a lustreless, dead appearance. As the
disease advances pain ceases, the light, instead of being disagreeable,
as at first, can hardly be procured of sufiicient intensity. The patient
resorts to spectacles of a high magnifying power, which condense a
great quantity of light upon the palsied nerve of vision ; these may
afford transient aid, but do ultimate injm-y. This disease may require

7

146 MATS-AGEMEIJT OF AETEFICIAL LIGHT.

from a few months to several years to run its course, but amaurotic
blindness is regarded as incurable.

267. Who are most subject to amaurotic disease. — Amaurosis may arise
from otber causes than the improper use of artificial light, but Dr.
Elliott states that nearly two-thirds of aU the cases of this disease
which are met with in practice, occur in those who use their eyes
much by artificial light, such as literary men, students, compositors,
tailors, seamstresses, shoemakers, engravers, stokers, glass-blowers,
&c. He also remarks that some individuals ai'e more liable than others
to sufier from the injurious action of artificial light, particularly those
of a fair complexion and with gray or light blue eyes.

XI.— MANAGEMENT OF ARTIFICIAL LIGHT.

268. Effect of gronnd glass Shades.— "We have stated (261) that all
light which is more intense than that coming from the object viewed,
dazzles the eye and weakens the impression of the object, causing it
to appear less clear and distinct. To cut off these blinding rays from
the flame itself, translucent screens of groimd glass, called shades^ globe-
shaped, or of any other desirable figure, are made to surround the lu-
minary, and have the efiect of deadening the light in a surprising man-
ner. The outline of the fiame disappears, while the rays of light come
from the surface of the globe, which thus appears self-luminous, and
emits a difi'used and softened light. As the rays cross each other at
aU points, and are scattered in all directions, objects near by throw
only short, indistinct shadows, and there is a general and equal illumi-
nation. These shades should be used whenever it is desired to reveal
to the best advantage the objects of a room, but where the vision is to
be specially exerted upon particular things, their use is unfavorable,
as by diffusion there is considerable loss of light. Objection has been
made to the employment of ground glass and semi-transparent white
ware shades, on the ground that by scattering the light they expand
the impression over a larger surface of the retina ; but as the image en-
larges in area, it diminishes in intensity, which is desirable, unless the
eye is constantly engaged in the scrutiny of minute objects.

269. How to collect the Light — Eeflectors. — It is apparent that the ra-
diation of light in all directions, is favorable to the equal illumination of
objects distributed in all parts of the room. But when we desire to
view closely minute objects, as in reading, writing, sewing, &c., it is
necessary to concentrate upon the point of observation the light which
would be otherwise wasted by general diffusion. To collect the rays,

EMPLOYMENT OF SHADES.

U1

and direct them to tlie part where they are required, (50oir<il shades or
reflectors, of tin, paper, or some other opaque substance, acd usuall,-
pohshed or whitened on the inside, are made to surround tho flame,
These not only protect the eyes from the glaring rays, but direct down
wards that which would escape in other directions and be lost.

270. Blue Shades to supply the missing rays. — To remedy the defect*
which arise from the bad composition of artificial light, several expe-
dients have been suggested. It is proposed to surround the flame with
a conical shade, the inner side of which is sky-blue. As the light that
passes upward, falls upon this surface, its red and yellow colors are
absorbed, and the few blue rays which it contained, being thrown
downward by the sloping sides of the reflector, mtagle with the
orange light, proceeding directly from the flame, and improve the bad
color by imparting to it a higher degree of whiteness. As in this
case a portion of the reddish yellow rays are absorbed, there is a loss
of light. If a common white reflector is used, more luminous matter
is thrown down than with the blue shade, and a stronger illumination
is produced. But, with a blue reflector, although there is less bril-
liancy, the light is whiter, purer, and has a higher defining power,
while it is cooler, more agreeable, and less injurious to the eyes.*

271. Structare and moonting of these Shades. — Shades of bristol-board,
or strong paper, or sUk, may be made by
any one. The material is to be cut into
the shape exhibited in Fig. 64, and then
the edges, a a and 5 5, are to be united
to each other, which gives rise to the
conical structure shown in Fig. 65. This
may be mounted upon a wire frame,
which is to be hooked on to the glass
chimney, or ground shade, or in the ab-
sence of these, a wire framework may be supported by the body of
the lamp. If the reflector be made of metal, as tin or copper, it may
be sustained either in the way described or by a three-branched sup-
port, screwed on to the burner. Eeflectors are
adapted to candles by attaching to the candlestick
an upright brass rod, on which the reflector slides,
being fixed at any point by a thumb-screw. This
is shown in Fig. 66.

272. How blue Reflectors should be colored. — The
most pure and michangeable blue color is ultramarine, and this is best

Fig. 64

Fig. 65.

• E. V. HAUGirworT, of 490 Broadway, N. T., furnishes these shades.

148

MANAGEMENT OF AETTFICIAL LIGHT.

Fig.

Candlestick with,
shade.

adapted for painting the inner surface of shades. Prnssian-hlue de-'
composes and turns green by exposure to the heat, and other coloring
matters are hable to fade or change. The colored
surface should be smooth, but without gloss or var-
nish, the surface appearing dead, or, as it is techni-
cally termed, ' flat.'

273. Artificial Light wMt«ned by absorption. — Blue,
transparent media absorb the yellow and red rays,
and transmit only those of blue. If the glass chim-
ney of a lamp be tinted lightly and evenly with a
mixture of ultramarine and mastic varnish, the of-
fensive orange will be separated from the light as it
passes through, but at the expense of its brilliancy;
there will be much less of luminous matter. But if
a polished tin or silvered reflector be employed to
collect the rays, it will throw downward a beautiful
soft white light. If the light from a luminary which
is surmounted by a white or polished reflector (Fig.
61) be made to pass through a glass globe filled with
water which has been slightly blued, its color will be
improved, while to compensate for the loss of luminous matter ab-
sorbed, the spherical form of
the water-bottle wUl serve to
converge or gather the rays so
as greatly to increase their Hlu-
miaating power, at the point
upon which they fall. Mello-
Ni has proved that when the
rays of artificial light are passed
through even a very thin stra-
tum of water, their heatiug
power is diminished by eighty-
nine per cent., but with little
increase in the temperature of
the water, in consequence of its
great capacity for heat (49).
The water-globe thus transmits
a cooler as weU as a whiter and
purer light. Lamp-globes made
of glass, slightly blued in its composition, would be very desirable.
274. Colored glasses for Spectacles. — The indiscriminate use of these

Whitening the rays and straining them of
their heat.

COLORED GLASSES — MISUSE OP GAS. 149

is altogether objectionable. They place the eyes in very unnatural
conditions as regards the light, and if their employment is persisted in,
it impairs their sensibility to the true relations of color, and otherwise
injures them, as we have just seen that artificial colored light is able
to do (253). If we look through a glass of any color, the effect is, that
when it is withdrawn, the eye sees all objects tinged by its comple-
mentary. As the colored glass cuts off a large quantity of light, its
removal produces a sudden and injurious impression. Faint blue
glasses may be serviceable in using artificial light. Colored glasses
absorb and accumulate the heat so as in many cases to be disagreea-
ble. Their bad effects are more marked, as it is for ' weak' eyes that
they are generally commended. They may, at times, be of service to
protect the eye from an intense glare, as of snow or the surface of
water in sunshine. Gray glasses, or what is called a ' neutral tint, '
that is no particular color, are perhaps best ; they should not be of too
dark a shade.

275. Is Gas-liglit injnrions 1 — There is a prejudice against gas-light,
as being the most injurious form of artificial illumiDation. As against
the proper and well-regulated use of gas, this prejudice is entirely
groundless, but there can be little doubt that from its abuse and bad
management it is really doing more mischief than any other kind of
light ; its very excellencies are turned to bad account ; its extreme
cheapness, compared with other sources of illumination, naturally leads
to its use in excessive quantities ; floods of light are poured forth, so
that persons may read and sew for hours together in the remotest cor-
ners of the room. The air is heated by the excessive combustion, and
poisoned by large quantities of carbonic acid, which there are no means
of removing. The eye is unprotected from the glare by screen or shade ;
extraneous light is freely admitted, which obscures the impression and
strains the nerve of vision, and in proportion as the sensibihty of the
eye is impaired, stronger light is used, which gives temporary relief,
but with danger of ultimate and permanent injury to the sight. On
the other hand, good, well purified gas, judiciously controlled in ac-
cordance with the hints we have given, and others to be offered in the
next part, is perfectly harmless (360).

PART THIRD.

AIK.

I.— PROPERTIES AND COMPOSITION OIJ' THE ATMOSPHERE.

276. Part it plays in the scheme of Nature* — It is impossible to con-
template the wonderful properties of the atmosphere without a feeling
of profound amazement. Whether we regard it as the grand medium
of water circulation, through which rivers of vapor lifted from the
oceans are carried landward, to be condensed and channel their way
back again to the sea ; or as the scene of tumultuous storms, generating
the lightnings within its bosom, and taking voice in the reverberating
thunders ; whether as hanging the landscape with gorgeous cloud-
pictures, or as the vehicle through which aU melody and beauty and
fragrance are conveyed to the portals of sense — it is alike strange and
interesting. But when we glance at its deeper mysteries, those inti-
mate relations to life which have been disclosed to modern science ;
when we consider that the vegetable kingdom not only has the same
chemical composition as the air, but in its mass is actually derived
from it ; that the whole architecture and physiology of trees, shrubs,
and plants, are conformed to atmospheric nutrition, so that in literal
truth the forests are but embodied and solidified air, the subject rises
to a still higher interest. And more startling yet is the surprise when
we recollect not only that the materials of our own bodily structures,
derived from vegetation, have the same atmospheric origin ; but that
active life, the vital union of body and spirit, and all the powers and
susceptibilities of our earthly being are only maintained by the action
of air in our systems ; — air which we inhale incessantly, day and night,
from birth to death. There is an awful life-import in these never-
ceasing rhythmic movements of inspiration and expiration, this tidal
flux and reflux of the gaseous ocean through animal mechanisms.
Shall we question that it is for an exalted purpose ? Science has many

IT CONSISTS OF PONDEEABLE MATTER. 151

things to say of the relations of air to life, but it can add nothing to
the simple grandeur of the primeval statement, that the Creator
"breathed into his nostrils the breath of life, and man became a
living soul."

277. Air a material reality — Its pressure. — The atmosphere is so thin
and invisible, and so totally unlike the objects that present themselves
to our most impressible senses, that we are half inclined to forget that
it is a reality, and are too apt to think of it as being mere empty space.
Yet it consists of ponderable matter, and is heavy, just like the solid
resisting objects which we see and handle, and it presses down upon
the ground with a force propoi-tional to its weight. Upon every
square inch of the earth's surface there rests about 15 lbs. of air.
Upon the body of a medium-sized man, having a surface of 2,000
square inches, the atmosphere exerts an external crushing force of
30,000 lbs. But there is air also within the system which exerts an
equal outward pressure, and thus prevents injury. The pressure of
air upon the body is not the same at aU times. There are tides in it,
just as there are in the ocean, great atmospheric waves which regu-
larly sweep over the earth and cause the weight of the atmosphere to
vary. Winds and storms produce similar effects. These variations in
atmospheric pressure are measured by the barometer (60), and they
are so considerable that a man's body may sometimes have from one
to two thousand pounds more pressure upon it than at others. Of
com-se, as the pressure upon the air increases from above, more of it
is crowded into the same space, and it becomes more dense. The
maximum height of the barometric column, therefore, corresponds to
the greatest density of the air, and a low condition of the mercury to
rarity of the air.

278. Weiglit of varions masses of Air, — As the air is thus ponderable,
it is desirable to obtain definite ideas of the proportion between its
bulk and weight. A cubic foot of air weighs 538*1 grains, or some-
thing more than an ounce. 13 "06 cubic feet weigh 1 lb. About 65
cubic feet of aii" furnish 1 lb. of oxygen. An apartment 8 feet high,
12 wide, and 13 long, contains about 100 lbs. of air ; and a room 40
feet square and 18 feet high contains about a ton. The atmosphere is
estimated to be 45 or 50 miles high, but the great mass of it lies close
to the earth, as it grows very rapidly thinner and rarer in ascending
from the earth's surface. Indeed if it were all the way up of the
same density as that which we breathe, it would be only about five
miles deep, just sufficient to cover the highest mountains.

279. Effects of varyii^ pressure <rf tlie Air. — ^Every variation of at-

152 PEOPEEITES AND COMPOSITION OP THE ATMOSPHEEE.

mospheric pressure must decidedly influence the state of the body,
modifying, as it were, the tension of tlie whole fahri«, affecting the
pores of the skin, the cells of the luugs, and the circulations within
the system. The constitutions of many invalids, especially the asth-
matic and consumptive, are undoubtedly much influenced by changes
of atmospheric density. As the barometer falls and the air becomes
lighter, the tendency to evaporation from all surfaces, and the amount
of expansion in all the more compressible tissues increases. As the
lungs have a constant capacity, and consequently receive the same
bulk of air at all times, it is clear that the quantity taken into these
organs to act upon the blood will vary with its density, there being of
course more matter in a chest-full of dense air than in a chest-full of
light air. Such changes, which powerfully influence the general rate
of action within the system, must affect the mind as well as the body,
and assist to explain the fact that "persons are often joyful, sullen,
sprightly, hopeful and despairing, according to the weather, while
there are days in which the faculties of memory, imagination and
judgment, are more acute and vigorous than others." Every alter-
ation of an inch in the mercury of the barometer adds or removes a
weight of 1,080 lbs. from the average weight which a man of common
stature sustains. The effects of sudden alterations of this pressure, as
when the barometer is subject to rapid and extreme variations, often
appear in the shape of headache and apoplexy (779). Yet in this, as
in numerous other cases, it is remarkable to what different states the
system can habituate itself. Saussttee, at the summit of Mont Blanc,
had scarcely sufficient strength to consult his instruments ; while at
heights scarcely inferior. South American girls wiU dance all night.
The influence of fluctuating pressure of the air is of great importance
to the inhabitants of low, swampy, malarious districts of country.
The amount of exhalation and effluvia which rise from the ground
depends much upon atmospheric pressure. When the air is heavy,
these substances are, as it were, confined to their sources, that is, they
are liberated at the slowest rate ; but as the barometer falls the pres-
sure is taken off, and the miasmatic emanations rise much more
freely (301).

280. Of what the Air is composed. — ^Now we can study all about at-
mospheric pressure, and many other things concerning the air, without
ever asking what it is made of; but before we can know why it
is that animals breathe, we must understand its chemical properties.
We have referred to the constituents of air in connection with the
subject of combustion (74) ; we are now to examine its composition

KBLATIVE PKOPOETION OF ITS CONSTITUENTS.

153

and endo-wments more fully in relation to life. The atmosphere con-
sists of four substances, — a pair of elements^ nitrogen and oxygen,
and a pair of compounds^ carbonic acid gas and vapor of water. Dry
air contains by weight very nearly 77 per cent, of nitrogen to 23 of
oxygen. The proportion of moisture in the atmosphere varies with
the temperature ; when saturated at 60°, it contains about 1 per cent.,
and it has an average of about l-2000th of carbonic acid. These pro-
portions are thrown into visible form by the diagram (Tig. 68). In
addition to these definite and stable elements, of which the atmosphere
ia universally composed, various gaseous exhalations from the earth

Nitrogen, or the diluUng constituent
of the Air.

Oxygen, or the active constituent of
the Air,

Moisture, or the variable constituent
of the Air.

Carbonic Acid, or the poisonous con-
stituent of the Air.

The areas of blackened surface represent the rela-
tive proportions by weight of the constituents of
the Air.

constantly enter it, though so minutely as generally to elude detection
and identification. LiEBia has shown that a trace of ammonia is
always present in it (299).

281. Intermktnre, or diffasioa of Gases. — These gases have different
weights. The oxygen is slightly heavier than the nitrogen ; the watery
vapor is much lighter than either, and the carbonic acid about half as
heavy again as the air itself It might seem, then, that if they were
mingled together they would gradually separate and arrange them-
selves in distinct layers, the heaviest at the bottom and the lighter
above. Some works on ventilation have actually stated such to be
the case, and that when we breathe out vapor of water and carbonic
acid, the former rises while the latter descends. One of them re-
Tiarks : "were these different portions of air as they come from the
7*

164 EFFECTS OF THE CONSTITUENTS OF AIR.

lungs, of different colors, we should, in a perfectly still atmosphere,
see the stream divided, part of it falling and part ascending." This,
of course, is not true. If such were the fact, if gases tended to
arrange themselves in the order of their gravities, and there were no
universal and inflexible law to prevent it, the carbonic acid of the air
might slowly sink to the earth, and form a deadly stratum 10 or 15
feet deep over its entire surface, or fill up aU its valleys with treacherous
invisible lakes of aerial poison. But such is not the tendency of
things. Gases brought together, no matter what their different
weights or varying proportions, diffuse throughout each other so as
to become perfectly and equally commingled. Heavy gases wiU rise
up to mix with lighter ones, and lighter gases descend to mingle with
those that are heavier. As a consequence of this important law, the
proportions of the atmospheric gases to each other are kept extremely
miiform, being scarcely, if at aU, influenced by season, climate, wind,
weather, or even the salubrity of the air. How benign and admirable
is this provision of nature, by which, without being aware of it, we
are relieved at every instant of a deadly though invisible poison, the
process continuing as well during sleep as while awake, and taking
place as perfectly for the unconscious babe as for the matured man.
This great law secures the unity of the atmosphere. Its ingredients
are perfectly mingled and equally diffused throughout each other, but
not chemically combined, so that in breathing, although we separate
the constituents of the air, we do not have to chemically decompose
it. When we speak of air we mean the mass of commingled gases
acting together ; yet as each constituent preserves its identity, and
produces its peculiar effects, it is necessary to consider them
separately.

II.— EFFECTS OF THE CONSTITUENTS OF AIE.

1. NiTEOGEN.

282. This gas seems to take no active part in breathing; it
passes out of the body as it entered it, without being changed. A
fire cannot be kindled in it, and an animal breathing it quickly dies,
though not from any positive noxious effect which it produces, but
rather from want of something else. Nitrogen is a negative or inert
substance, its chief use being to dilute or temper the other active in-
gredients of the air to a proper degree of strength.

2. OXTGEN-.

283. How the System Is ebarged with Oxygen. — Of the wonderful in-

OXYOEK — HOW IT ENTEEB THE SYSTEM.

155

Fig. 69.

fluence of this agent we can here speak bnt briefly, as the subject will
have to be considered again more fully in treating of the action of
foods. "We have noticed that oxygen is the active agent in combus-
tion, so it is also in breathing. It is on account of what it does in our
system that we respire the atmosphere. The air enters the lungs
through the windpipe and bronchial tubes or air passages, as seen in
Fig. 69. It fills and distends the numberless little cavities or air-cells,
which are enclosed by these membranes, and overspread with the finest
network of capillary blood-vessels. Oxygen then penetrates or passes
through the delicate membrane and enters the blood, imparting to
it a bright crimson color, and rushing forward with it through what
is called the pulmonary vein (Fig. 70) to the heart. It is estimated that
the lungs contain, on an average, 220 cubic inches of air, with an
inner membrane surface of 440
square feet, nearly thirty times
greater than the whole exterior of
the body.* This vast extension of
surface is to secure the largest and
most perfect opportunity of action
and reaction between the air and
blood. From the heart the blood
passes by the arteries to aU portions
of the body. These arteries divide
and subdivide until they are reduced
in size to the finest hairlike tubes,
which are densely interlaced through-
out all the tissues of the body.
The arterial channels thus represent
streams of oxygen flowing from the
lung fountains to every portion of
the system. In this way each mi-
nute part of the living fabric is in
direct communication with the ex-
ternal air, that it may receive from
it the agent upon which it imme-
diately depends for the performance
of its vital offices. This system of

arterial currents, bearing oxygen /rom the air to every portion of the
system, implies a set of counter-currents to drain off the poisons gen-
erated within the body, back into the air. This is the duty of the veins
OP venous system. In the accompanying diagram (Fig. 70), the fine

* Dr. Addison estimates the number of air-cells in the two Inngs at 1,744,000,000,
«nd the extent of the membrane at 1,500 square feet.

<:7/

Human Lung.
a the larynx; 6 wirxipipe ; e c o bron-
chial tubes or air passages ; e lung.

156

EFFECTS OF THE CONSTITUENTS OP AIE.

vessels at the top represent the lungs, and those at the bottom the
capillaries of the whole body. The double circulation is shown, and
how the heart is related to it. The vessels on the right side represent
the arteries carrying blood charged with oxygen, and those on the left
side, the veins, conveying carbonic acid.

Fig. 70.
Lesser or Pulmonary Circulation.

Pulmonary
Artery.

Heart.
Eight Auricle.

Eight Ventricle.

Vena Cava.

Pulmonary
Vein.

Left Auricle.

Left Ventricle.

- Aorta.

Greater or Systemic Circulation.

284. What Oxygen does In the hody. — The purpose of this incessant
inflowing stream of oxygen, is to carry forward the great operations
of the vital economy. Oxygen has a wide range of chemical attrac-
tions, and combines with other elements with intense energy. It is
the ever-laboring, tireless Hercules of the atmosphere. As it kin-
dles and maintains the combustion of our fires, so it does our bodily
vitality. The muscles are called into action through decomposition
by oxygen, and as with the muscles in the manifestation of mechani-
cal force, so with the brain in the exercise of intellectual power. This

INTLUBNCE OF OXYGEN — MOISTURE. 157

organ is on an average only about ^ the -weiglit of the whole body,
yet it receives from jth to -j^th of the entire oxygenated stream from
the Imigs and heart. A torrent of oxygen is thus poured incessantly
into the material apparatus of thought to carry forward certain physio-
logical changes upon which thinking depends. If the arterial stream
be cut off from a muscle, it is paralyzed ; if it be stopped from the brain,
unconsciousness occurs instantaneously. In proportion to the activity
of muscle is its demand for the destructive agent ; in proportion also
to the activity of the mind is the brainward flow of arterial blood.

285. Eflfccts of varying the quantity of respired Oxygen. — If an animal
be deprived of this gas, it dies at once. If man undertake to breathe
a less proportion than that naturally contained in the air, the effect is
a depression of all the powers of the constitution, physical and mental,
to an extent corresponding with the deficiency. If the natural amoun"t
be increased, there is augmented activity of all the bodily functions,
the life-forces are exalted, and the vital operations are driven at a
preternatural speed. If pure oxygen is respired, the over action and
fever become so great that life ceases in a short time. Nitrous oxide
(laughing gas) is a compound rich in oxygen, and when presented to
the blood it absorbs a much larger proportion of it than of pure oxygen.
Hence, when this gas is breathed, the blood drinks it up rapidly, and
the system becomes so saturated with it as to produce the most remark-
able effects. The muscular energy is so aroused that the inhaler is
often impelled to extraordinary feats of exertion, and the intellectual
powers are excited to a delirious activity.

3. MOISTUEE.

286. How mncli moistnre the Air contains. — The third constant ingre
dient of the air is moisture, derived from evaporation upon the earth's
surface. The quantity which the air wiU hold depends upon its tem-
perature, and hence fluctuates greatly. At zero a cubic foot of aii
will hold but •18 of a grain of watery vapor ; at 32° it wiU contain 2'35
grs.; at 40°, 3-06; at 50°, 4-24; at 60°, 5-82; at 70°, 7*94; at 80°,
10-78; at 90°, 14-38; at 100°, 19'12 grains, and as the temperature
goes higher still, the capacity for moisture also increases (308). After
the air has imbibed its due quantity of vapor, at a given temperature,
it is then said to be saturated, and wiU receive no more unless the heat
be increased. To better appreciate how rapidly the capacity for moist-
ure augments, as the temperature ascends, we will state the propor-
tions in another form. A quantity of air absolutely saturated at 32°,

158 EFFECTS OP THE CONSTITUENTS OF AIR.

holds in solution an amount of vapor equal to the ^fo part of its
weight; at 59°, ^V; at 86°, ^\; at 113°, ^V; and at 140°, ~,\.

287. Conditions of the drying power of the Air. — If, when the air is
saturated, its temperature falls, a portion of its moisture is precipitated,
that is, it does not remain dissolved, but appears in drops of dew.
Thus a cubic foot of air, saturated at 90°, if cooled 10° would deposit
3 -5 grains of water. Until it is saturated, air is constantly absorbing
moisture from all sources whence it can procure it. A cubic foot
of air at 90°, and containing but 8 grains of moisture, is capable of
absorbing 6*3 more, and this is the measure of its drying power.
Watery vapor is lighter than the air, and when mingled with it in-
creases its levity in a degree proportional to its temperature. This is
one of the causes of the ascent of breath expired by the lungs, at the
temperature of the body. In drying-rooms and laundries, if the open-
ings for the escape of hot air be at the bottom, as the air gets saturated
with vapor it becomes lighter, and rising, fills the room and stops
the evaporation. If the opening be at top the loaded air rises and
escapes, and the drying wiU be observed to commence at the bottom.

288. Moisture lathe Air of Rooms— Dew-point. — It has been explained
that the temperature at which air is saturated, and begins to condense
its moisture in drops, is called the dew-point (34). "When air contains
so much moisture that its temperature needs to decline but little be-
fore water appears, the dew-point is said to be high ; when it must
lose much heat before drops are produced, its dew-point is low. Air,
with a high dew-point, is therefore moist, while that with a low dew-
point is always thirsty and drying. A simple means of finding out
the dew-point, and ascertaining the drying power of the air, is as
follows : — Note the temperature of the air by a thermometer, taking
care that the instrument is not influenced by the radiation of any
heated body in its vicinity. Then introduce it into a glass of water
and gradually add a little ice, carefully watching for the first ap-
pearance of moisture on the outside of the tumbler. The tempera-
ture at which the deposit commences is the dew-point ; and the
difference between it and the temperature of the air, expresses its
drying power. If the air is at 60° and moisture begins to be con-
densed at 40° its drying power is 20 degrees. Mason's hygrometer
is a little instrument which indicates the dew-point without trouble.
It has two thermometers, one of which gives the temperature of
the air, and the bulb of the other, connected constantly with a
reservoir of evaporating liquid, is kept cooled, and gives the dew-
point ; so that the amount of humidity in the air is seen at a glance

MOISTURE — ITS PEESBEVATION IN THE BOOM. 159

by comparing the two scales ; — cost, from 3 to 5 dollars. From obser-
vations made at ■Washington through June, July, August, and Sep-
tember, from 9 to 3 o'clock of the day, the dew-point was, on an
average, 11° below the temperature of the air, and sometimes more
than 20° below. The air is always dampest near the ground; a
difference in height of 60 feet, in the same exposure, has been known
to make a difference of 10^ degrees in the dew-point. In our houses,
we are to imitate as far as possible the external conditions of the air.
As the temperature of freshly drawn well water is about 50°, a vessel
containing it should receive a deposit of moisture when brought into
our rooms, if they have a temperature above 65°. It is very rare that
any such deposit is seen in apartments heated by a hot-air furnace,
even if a considerable quantity of water is evaporated.

289. How doable Windows affect the moistnre of Eooms. — Glass sky-
lights often drip moisture upon those below, and we see it copiously
condensed in winter upon the windows and trickling down the panes.
This is often mistaken for a symptom of abundant humidity in the air,
but it may occur when the air is extremely dry. "When, as often
occurs, air within a room is at 70° or 80°, while just outside the
window-glass it is down to freezing, or below ; the inner layer of au*
next the glass will rapidly deposit its water, and then falling to the
floor will be succeeded by other air (337), so that the window acts as
a perpetual drain upon the moisture of the apartment. It is often
impossible to maintain the air properly humid on this account. Peo-
ple are misled by this copious deposit of dew upon the glass, and it is
hard to convince them that the air is deficient in moisture when they
can see it condensed upon the windows. We have referred to double
windows as a means of saving h^eat, and we might have added that
they are equally serviceable in summer to exclude its excess of heat ;
the enclosed air acting just as well to bar out the heat of the warm
season, as to confine it within, in cold weather.* But double win-
dows also prevent the deposit and loss of moisture from the air in
rooms, and in this respect they are most useful. Glass is not essential
to their construction, where we require only a diffused light ; white
cotton cloth stretched upon a suitable frame and rendered impervious
to air by linseed oil or other preparation, will answer equally as well
for preserving heat, and be much less expensive.

290. Rate of Eraporation. — ^When dry air is exposed to a source of
moisture, a considerable time must elapse before it will become satu-

* If double windows are to be retained in summer, tbey cannot be used for airways,
lis single windows are made to do; there must be independent means of ventilation.

160 EFFECTS OF THE CONSTITUENTS OF AIR.

rated. The diffusion of vapor into hot air is much more rapid than
into that which is lolder, but it is not at all instantaneous. Mr.
Daniell observed, that a few cubic inches of dry air, continued to
expand by the absorption of humidity for an hour or two, when ex-
posed to water at the temperature of the surrounding air. In cold
regions there is much less moisture in the air than in hot, and less
in winter than in summer. It is also subject to a regular diurnal
variation. As the sun warms the air during the day, evaporation is
increased, and the humid element rises into the atmosphere ; but as it
declines toward evening, cooling begins, and at night the watery vapor
again falls, and is deposited upon the earth. "We are not to infer that
because there is an absence of rain, therefore the air is dry ; on the
contrary, in long droughts the air is often heavily charged with mois-
ture.

291. How moist Air aflfects the System. — The skin relieves the System
of moisture in two ways ; by insensible perspiration, and by sweating.
Under common circumstances, the loss is six times greater by the
former than by the latter process. The skin, as well as the lungs, is
an excreting organ ; it contains, packed away, some 28 miles of micro-
scopic tubing, arranged to drain the system of its noxious matters,
carbonic acid, &c., which, if retained in the body, become quickly in-
jurious. The perspiration given off in this climate amounts to 20 oz. per
day, and in hot countries to twice that quantity. But air which is al-
ready saturated with moisture refuses to receive the perspiration which
is offered to it from the skin and lungs ; the sewerage of the system
is dammed up. Much of the oppression and languor that even the
robust sometimes feel in close and sultry days, is due to the obstruc-
tion of the insensible perspiration by an atmosphere surcharged with
humidity. Not only are waste matters generated in the system thus
unduly retained, but malarious poisons introduced through the lungs
by respiration, are prevented from escaping ; which would lead us to
anticipate a greater prevalence of epidemic diseases in damp than in
dry districts. Sucli is the fact, as we notice in Cholera, which follows
the banks of rivers, and revels in damp, low situations. Moisture
joined with warmth is most baneful to the system. The American
Medical Association report that during the remarkable prevalence of
Sun-stroke in the city of Few York in the summer of 1853, which al-
most amounted to an epidemic, the heat of the atmosphere was ac-
companied by great humidity, the dew-point reaching the extraordi-
nary height of 84°. In Buffalo, in the summer of 1854, the progress
of cholera to its height was accompanied by a steady increase in at-

MOISTURE — CAEBONIC ACID. 161

mospheric humidity. Air whicli is warm and moist, has a relaxing and
weakening influence upon the body. The siroco is invariably charged
with moisture, and its effects upon the animal economy illustrate but
in an exaggerated degree the influence of damp warm weather. When
it blows with any strength, the dew-point is seldom more than four or
five degrees below the temperature of the air. The higher its tempera-
ture, the more distressing its effects, owing to the little evaporation it
produces. This, connected with its humidity, is the principal cause of
all its pecuUarities — of the oppressive heat — of the perspiration with
which the body is bathed — of its relaxing and debilitating effects on
the system, and its lowering and dispiriting effects upon the mind.
— Wtma]!?. Damp air at the same temperature as dry air has a more
powerful cooling effect, producing a peculiar penetrating chilling feel-
ing, with paleness and shivering, painfully known to New England
invalids as accompanying the east winds of spring.

292. Effects of dry Air. — Dry air favors evaporation. By promoting
rapid transpiration from the pores of the skin, it braces the bodily
energies and induces exhilaration of the spirits. Cold dry air is
invigorating and reddens the skin, with none of the distressing symp-
toms of cold moist air. If very dry, it not only accelerates perspira-
tion, but desiccates and parches the surface, and deprives the lining
membrane of the throat and mouth of its moisture so rapidly as to pro-
duce an uncomfortable dryness, or even inflammation. Dry climates
which quicken evaporation, are best adapted for relaxed and languid
constitutions with profuse secretion, as those afiQicted with humid
asthma, and chronic catarrh with copious expectoration. The Ha/r-
mattan, a dry wind from the scorching sands of Africa, withers,
shrivels, and warps every thing in its course. The eyes, lips, and
palate become dry and painful. Yet it seems to neutralize certain
conditions of disease. "Its first breath cures intermittent fevers.
Epidemic fevers disappear at its coming, and smaU-pox infection
becomes incommunicable."

4. Oaebonio Aoid.

293. Physiological effects of Carltonic Acid. — The fourth constant in-
gredient of the atmosphere is carbonic acid ; a transparent, tasteless,
inodorous gas. It takes no useful part in respiration, indeed it exists
in the air in so small a proportion that its effects upon the system are
inappreciable. Its sources are the combustion of burning bodies, fer-
mentation and decay, the respiration of animals ; and it is also gener-
ated within the earth, and poured into the air in vast quantities from

162- EFFECTS OF THE CONSTITUENTS OF AIE.

volcanoes, springs, &c. It may be set free more rapidly than it will
dissolve away into air ; it then accumulates, as sometimes in weUs,
cellars, rooms, «&c. and becomes dangerous. "When breathed pure, it
causes suffocation by spasmodically closing up the glottis of the throat.
When mixed with air in small quantities, it is admitted to the lungs,
and then acts as a rapid narcotic poison. The symptoms of poisoning
by carbonic acid gas are throbbing headache, vdth a feeling of fulness
and tightness across the temples, giddiness, palpitation of the heart, the
ideas get confused and the memory falls. A buzzing noise in the ears
is next experienced, vision is impaired, and there is strong tendency to
sleep. The pulse falls, respiration is slow and labored, the skin cold
and livid, and convulsions and delirium are followed by death. This
gas has been often employed as a means of suicide. A Son of the
eminent French chemist, Bertholet, under the influence of mental de-
pression, retired to a small room, locked the door, closed up every
crevice which might admit fresh air, carried wi'iting materials to a table
on which he placed a seconds watch, and then seated himself before
it, described his sensations, and was found dead upon the floor.*

294. Effects ia small qnaatities. — The proportion of carbonic acid ne-
cessary to produce a poisonous atmosphere is very small ; so much so
that in attempts at suicide by burning charcoal in an open room, the
people who entered it have found the air quite respirable, although the
persons sought were in a state of deep insensibility {coma). From 5
to 8 per cent, of carbonic acid in the au" renders it dangerous to
breathe, 10 to 12 makes it speedily destructive to life. The natural
quantity in the air is so small that it may be multiplied 20 times before
it rises to 1 per cent. Air containing one per cent, of this gas is
soporific, depressing, takes from the mind its cutting edge, tends to
produce headache, and is most injurious. That proportion of carbonic
acid which nature has placed in the atmosphere, we assume to be

* " I light my farnace, aBil place my candle and lamp on the table with, my watch. It
is now 15 minutes past ten. The charcoal lights with difficulty. I have placed a funnel
on each furnace to aid the action of the fire. 20 minutes past ten. The funnels fall : I
replace them ; this does not go to my satisfaction. The pulse is calm, and beats as usual.
10 h. 30. A thick vapor spreads itself by degrees in the chamber. My candle seems
ready to go out. My lamp does better. A violent headache commences. My eyes are
filled with tears ; I have a general uneasiness. 10 h. 40. My candle is extinguished, the
lamp still burns. The temples beat as if the veins would burst. I am sleepy. I suffer
horribly at the stomach ; the pulse beats 40 per min. 10. 50. I am suffocated. Strange
ideas present themselves to my mind. I can hardly breathe. I shall not live long. I
have symptoms of madness. lOh. 60. [Here, he confounds the hours with the minutes.]
I can hardly write ; my vision is disturbed ; my lamp flickers ; I did not believe we suf-
fered 60 much in dying. 10 h. 62 m. [Hero were some illegible characters]."

THEIK HAKM0NI0U8 AND BENEFICENT ACTION. 163

entirely inoffensive, but the more it is increased beyond that amount,
the less it is fitted for respiration. Precisely so with the body. Car-
bonic acid is continually generated within it and continually poured
out from the lungs into the air ; a certain amount in the blood is com-
patible with health, but if that quantity be slightly increased, it at
once begins to act as a poison. Any cause, therefore, which hinders
the escape of this gas from the lungs, tends to accumulate it in the
blood and produce injury, and this is exactly the effect, if there be
considerable carbonic acid in the air we breathe. Its exhalation from
the lungs is retarded if the outer air already contains more than its
usual amount of carbonic acid.

295. Why then does the Air contain Carbonic Acid? — But if this gas be
useless, or positively detrimental in animal respiration, why is it made
a constant and essential ingredient of the atmosphere ? The plan of
nature requires it. As it is formed in all animal bodies, and breathed
out into the air, and also by all combustions, its presence there is un-
avoidable, while it is the great source of nom'ishment to the whole
vegetable world, which drinks it in through innumerable pores in every
green leaf, and thus keeps the proportion down to the point of safety
for animals.

296. Effect of these Ingredients combined. — Such are the constant con-
stituents of the air, and such, so far as it has been possible to determine
it, is their separate influence upon man. The effects of the atmosphere
we breathe are the resultant of these agents acting together. "We see
that it exerts an all-controlling influence upon the human constitution.
To say that it is useful or important, gives us no adequate conception
of the facts ; it is the first condition of vital activity — what the stream
is to the water-wheel or fire to the steam-engine — ^the immediate im-
pelling power of life. Any one of its elements breathed alone would
be fatal ; any other proportions than those in which they are com-
mingled would be dangerous or deadly. Its elements taken alone are
poisonous and excoriating, but properly mingled and neutralized, how
bland, how balmy, how innocent they become. Pressing upon us with
the weight of tons, bathing the sensitive breathing passages — distend-
ing the filmy membranes of the air cells, flashing through into the
blood and swept forwai'd to the inmost depths of the system, corroding
and consuming in its progress the living parts — and yet with such
marvellous delicacy are aU these things accomplished, that we remain
profoundly unconscious of them. Unspeakable indeed are these har-
monies of life and being, and how adorable the Power, Wisdom and
Love from which they emanate.

164 effects of the constituents of air.

5. Ozone and Eleoteioitt.

297. Ozone in the Air. — Our view of the properties of the atmo-
sphere would be incomplete without reference to these agencies. At-
tention has latterly been drawn to the interesting and significant fact
that the chemical elements are capable of existing in different states,
with widely different pi-operties and powers. We see this in the case of
carbon, which assumes several states, as charcoal, lampblack, diamond.
Sulphur, phosphorus, and indeed many of the other elements are found
capable of this change of state, wiich is -known as allotropism. It has
been discovered also that the remarkable element oxygenhas its double
condition, its ordinary state and another of extreme activity, in which
it seems to acquire new energies ; in this heightened form of action it
is called ozone. It may be readily changed from the common to the
superactive state, acquiring bleaching and oxidizing energies which it
had not before. Ozone is extensively formed in the atmosphere, by the
operations of nature, although under precisely what circumstances we do
not know. It is found more abundantly in some locahties than in
others, and may be generally recognized in air which has swept over
the ocean, although usually absent in that which has traversed large
tracts of land. There has been much speculation as to how the air is
affected by its presence, in relation to health and disease. It is said
that when present in excess diseases of the lungs, especially influenza,
prevail ; when deficient, fevers and all those diseases which are sup-
posed to depend upon a kind of fermentation in the blood are com-
mon,— it being thought that ozone oxidizes or burns away the exciting
fermentable matter, thus acting as a purifying agent. It has been
stated that in cholera ozone is entirely absent from the air.

298. Atmospheric Electricity. — "I cannot tell," says Dr. Faraday,
" whether there are two fluids of electricity, or any fluid at all ;" such
is our profound uncertainty in relation to this mysterious agent. Yet
it is commonly assumed to be a subtle fluid, distributed through all
substances, and lying buried beneath their surfaces in a condition of
equilibrium, or rest. Various causes may disturb this state, producing
electrical excitement^ when the fluid is supposed to accumulate in
some substances to excess, which are then said to be positively electri-
fied,— while in others it is deficient, and these are negatively electrified.
Some substances, as the metals, allow electricity to pass through them
freely ; these are called good conductors; others refuse it a ready passage,
and are termed non-conductors^ as silk, glass, air. "When from any cause
excitement has taken place, and a body has been charged with electri-

ELECTEICITT — ATMOSPHERIC CONTAMINATIONS. 165

city, or robbed of it to a certain degree, there is an escape ; if a good
conductor be presented to it, it flows off quietly ; if a bad conductor, it
dashes through it, producing fire, light sound, and perhaps violent
rupture {disruptive discharge). The friction of unlike bodies against
each other creates electrical excitement. If we slide rapidly over a
carpet, the body becomes so excited that it may yield a spark which
will light the gas. The friction of masses of air, of different temper-
atures, or containing different degrees of moisture, by rubbing against
each other, or grinding against the earth, developes electricity. So,
also, does evaporation. If a saucer of water be suspended by non-
conducting silk cords (insulated)^ evaporation goes on as usual at first,
but is soon checked. It gives off positively electric vapor, while the
saucer remains negatively electrified. If it be connected with the
ground by a conductor, active evaporation is resumed. Combustion
produces electricity ; the escaping carbonic acid being positive, while
the burning body is negative ; the vapor of the expired breath is also
positive. The air is generally electrified positively, especially in clear
■weather ; but during the fall of rain, fogs, snow, and storms, it may be
negative. The electricity of the atmosphere appears to have a daily
ebb and fiow, like the tides of the sea, twice in every 24 hours. It is
feeble at sunrise, increases in intensity during the forenoon, declines
again in the afternoon, until about two hours before sunset ; it then
advances until perhaps two hours after sunset, and again diminishes
until morning. It has become fashionable, latterly, to offer electricity
in explanation of all obscurities, material and spiritual. Beyond doubt
it is profoundly involved in the phenomena of our being, but we as
yet understand but httle about it. In connection with the air, we can
only say, that when it is clear, and electricity is rapidly developed, the
spirits are more buoyant, and the feelings more agreeable, than when
the atmosphere is in the opposite state.

III.— CONDITION OF AIR PROVIDED BY NATURE.

299. Impurities of the external Air.— There are natural causes which
tend to make the atmosphere impure, but they act with variable in-
tensity in different localities. Animal respiration and combustion exert
a contaminating influence upon the atmosphere, but considering its
vast mass, the general effect is but trifling, and besides is perfectly
neutralized by growing vegetation, which evermore absorbs from the
air carbonic acid, and returns to it pure oxygen in the daytime. The
decay of organic matter, vegetable and animal, generates numer-

166 CONDITION OF AIR PROVIDED BY NATURE.

ous substances which are prejudicial to health. Liebig has lately
shown that ammonia from these sources is continually present in
the air. Its quantity is so minute that it cannot be directly de-
tected, but it may be traced in rainwater, having been washed
out of the air in its descent (371). The exhalations and eflBuvia
arising from active decomposition in wet lands, swamps, marshes,
&c., especially in hot seasons and locahties, are prolific sources
of disease. Minute microscopic germs, both vegetable and animal,
exist in the atmosphere, and the course of winds has been tracked
across oceans by the peculiar organic dust which they carried.
Not only do plants and flowers exhale continually their peculiar fra-
grances, but even mineral matters and earths have also their odors, which
rise and mingle with the air. Indeed, we must conceive of the air as
the grand reservoir into which all volatile matters escape. Professor
Gbaham contends that malarious and contagious bodies are not strictly
gaseous, but are highly organized particles of fixed or sohd matter,
which find their way into the atmosphere, like the pollen of flowers,
and remahi for a time suspended in it. The inconceivable minuteness
of exhalations difiiised through the air, which are yet sufficiently
active to impress the senses, is forcibly illustrated by the foIlo"\ving
fact, which we give on the authority of Dr. Oaepentee. " A grain
of musk has been kept freely exposed to the air of a room, of which
the doors and wiadows were constantly open for a period of ten years,
during all which time the air, though constantly changed, was com-
pletely impregnated with the odor of musk ; and yet, at the end of
that time, the particle was found not to have sensibly dimhiished in
weight."

300. Effects of Exposnre, Foliage, aad Soil. — The salubrity of the ex-
ternal air is influenced by elevation, trees, and soU. The exposed hUl-
top ensures atmospheric purity. It is often surprising what effect
a small difference in the elevation has upon the healthfulness of a par-
ticular spot. A rise of 16 feet within 300 yards has been known to
produce an entire change from a relaxing to a bracing air. The lower
place was completely enveloped in foliage and without drainage, while
the higher was comparatively free from trees, and besides, had a good
fall for surface-water and sewerage. Dense foliage around a dwelling
may be injurious, by causing dampness and stagnation of air, especially
if the situation be protected from winds. If the ground be loaded
Avith putrefy' ng matter and soaked with refuse water, the air above it
cannot be pure. The ground below and around the dwelling should
be dry. A soil absorbent and retentive of moisture, always damp, is

IMPUBinES NEAR THE GROUND AT NIGHT. 167

unfit to live on nnless thorougHy drained. Sand or gravelly ground
is best, provided it be not locked in by a surrounding clay basin, with
no outlet for the rainfall.

301. Cause of the unwholcsomeness of Night Air. — There is ground for
the common belief that night air is less healthful than that of the day.
It is known that the deadly tropical fevers affect persons almost only
during the night. Yet the poisonous miasms from the rotting substan-
ces of the ground vrhich cause those fevers, is produced much faster
during the intense heat of the day than in the colder night. But in
the daytime, under the hot tropical sun, the air heated by contact
with the burning ground expands and rises in an upward current, thus
dUuting and carrying away the poisonous malaria as fast as it is set
free. The invisible seeds of peStUence, as they ripen in the festering
earth, are lifted and dispersed in the daytime by solar heat ; but as no
such force is at work at night, they then accumulate and condense in
the lower layer of the atmosphere. Now although fatal fever poison
may not be generated, yet decomposition of vegetable matter yielding
products which are detrimental to health take place every where upon
the surface of the ground ; and though dissipated during the day, they
are concentrated and confined so close to the earth at night as to affect
the breathing stratum of the air.

302. Upper Rooms least affected by Night Air. — It will hence be seen
that the different stories of a house are differently related to this
source of injury : the upper ones being situated above the xmwhole-
some zone, are most eligible for sleeping chambers, while the ground-
floor is more directly exposed to the danger. Dr. Kxjsh states, that
during the prevalence of yeUow fever in Philadelphia, those who oc-
cupied apartments in the third story were far less liable to attack than
those who resided lower. Low one-story houses, in which the inhab-
itants sleep but three or four feet from the ground, and are therefore
directly exposed to the terrestrial exhalations, must be considered
more objectionable than loftisr sleeping apartments. Sleeping in low
rooms is perhaps worse in the city than in the country.

303. The Atmosphere Self-purifying. — In aU healthy localities the pro-
portion of impurities is so small that their effect is imperceptible.
When noxious exhalations are set free from any source, they are dif-
fused through the vast volume of the atmosphere, so as not to be
detectable by the most refined means of chemistry. The law of
gaseous diffusion, aided by winds and storms, secures dispersion and
universal intermixture. Oxygen finally takes effect upon these baneful
emanations, destroying and burning them as truly as if they had been

168 SOURCES OF IMPURE AIE IN DWELLINGS.

consumed in a furnace. The atmosphere thus secures its own puri-
fication on the grandest scale, and its vital relation to animal life re-
mains undisturbed.

304. Air within Doors. — But when we enter a dwelling the case is
altered. It is as if the boundless atmosphere had ceased to exist, or
had been contracted within the walls of the apartment we occupy.
Causes of impurity now become a matter of serious consideration.
They are capable of affecting, in the most injurious manner, the little
stock of air in which we are confined ; and it is therefore, on every
account, important that we have a clear idea of the nature and extent
of the common causes which vitiate the air of our dwellings.

IY._SOURCES OF IMPURE AIR IN DWELLINGS.

305. Breathing and Gomhastion. — By breathing, the burning of fuel
and combustion for light, large quantities of oxygen are removed from
the air, while at the same time carbonic acid in nearly equal bulk
takes its place. In the case of fuel, if the combustion is perfect, the
air that has been changed is immediately removed up chimney by the
draught. But not so in respiration and illumination ; the air spoiled
by these processes remains in the room, unless removed by special
ventilating arrangements.

306. Leakage of bad Gases from Heating Apparatus. — While, in point
of economy, stoves are most advantageous sources of heat, yet in their
effects upon the air they are perhaps the worst. We saw that in the
stoves called air-tight^ the burning is carried on in such a way that
peculiar gaseous products are generated (121). These are liable to
leak through the crevices and joinings into the room. Carbonic oxide
gas is formed under these circumstances, and recent experiments have
shown that it is a much more deadly poison than carbonic acid. The
slow, half-smothered burning of these stoves requires a feeble draught,
which does not favor the rapid removal of injurious fumes. Besides,
carbonic acid being about half as heavy again as common au', must be
heated 250° above the surrounding medium to become equally light,
and still higher before it will ascend the pipe or fine. If the com-
bustion of the fuel is not vivid, and the draught brisk, there will be
regurgitation of this gaseous poison into the apartment. Dr. Uee
says, " I have recently performed some careful experiments upon this
subject, and find that when the fuel is burning so slowly as not to heat
the iron surface above 250° or 300°, there is a constant deflux of car-
Ionic acid into the room.'''' Probably all stoves, from their imperfect

HOW AIR IS ALTERED BY HEAT. 169

fittings, are liable to this bad result. Hot-air farnaces, also, have the
same defect. They are cast in many pieces, and however perfect the
joinings may be at first, they cannot long be kept air-tight, m conse-
quence of the unequal contraction and expansion of the different parts
under great alterations of heat. Combustion products are hence
liable to mingle with the stream of air sent into the room,

307. Air aflFected by Hot-irou Surfaces. — But if stoves become a source
of contamination to the air at low temperatures, neither are they free
from this objection when made hotter ; at high heats (and they are
often red-hot), they seriously injure it in other ways. It is well known
that iron highly heated causes disagreeable effects upon the air of
rooms, producing a sensation ascribed to hurnt air^ but the nature of this
change is not fully understood. The common method of explaining it,
that the iron decomposes the air and robs it of oxygen, is in no degree
satisfactory, as the quantity of oxygen thus removed must be extremely
small, and besides, a portion of this very small amount comes from
the decomposition of atmospheric moisture, its hydrogen being set
free. The minute particles of dust, myriads of which fill the air, as
seen when a ray of light is admitted into a darkened room, and which
consist of aU kinds of vegetable and animal matters, settle upon the
hot stove, and are roasted or burnt with the escape of gaseous impu-
rities. In the stove metal itself there is always, beside the cast-iron,
more or less carbon, sulphur, phosphorus and arsenic, and it is possible
that the smell of air, passed over it in the red-hot state, may be owing
to the volatilization or escape of some of these ; because it is to be re-
membered that a quantity of noxious efl3uvia, too small to be seized
and measured by chemical means, may yet affect the sense of smell
and the pulmonary organs.

308. Composition of Air altered by Iieating it. — It is a capital advan-
tage of the methods of warming by fireplaces and grates — simple ra-
diation— that they do not heat the air : it remains cool while the
heat rays dart through it to warm any objects upon which they fall.
The sun pours his floods of heat through the atmosphere without
warming it a particle. Air is made to be hreathed^ and we again dis-
cover Providential Wisdom in the arrangement by which the sun
warms us, without disturbing, in the slightest degree, the respiratory
medium. But if we heat the air itself^ we at once destroy the natural
equilibrium of its composition, and so change its properties that it be-
comes more or less unpleasant and prejudicial to health. "We have
noticed the bad effects upon the system of dry heated air, and it was
shown that the state of dryness does not depend upon the actual

170

SOUECES OP IMPUEE AIR IN DWELLINGS.

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w

..

|T

;

;

;

■

■

B

■

■

m

■

The length of the bars indicates the relative propor-
tions of moisture that a cubic foot of air will hold at
the different temperatures.

amount of moisture present, but upon the temperature. Witli the
same quantity of aque-
ous vapor^ it will be
moist and humid at a
low temperature, while 100
at a high one it will be
parched and greedy of
water. The accompa-
nying diagram (Fig. 71)
exhibits the relative
amount of moisture that
air contains when satur-
ated at the temperatures
mentioned. Suppose that air at 32° be heated to 100° (and it often is
much higher), and be then thrown into the room. The difference in
the length of the bars opposite these two numbers expresses its de-
ficiency of moisture, and hence its drying and parching power. Air
thus changed is apt to produce unpleasant feelings and painful sensa-
tions iu the chest, which are often attributed to too great heat. " In
very dry air the insensible perspiration will be increased, and as it is
a true evaporation it will generate cold proportional to its amount
(69). Those parts of the body which are most msulated ia the air,
and furthest from the heart, will feel this refrigerating influence most
powerfully ; hence that coldness of the hands and feet so often expe-
rienced. The brain being screened by the skuU from this evaporating
influence, will remain relatively hot, and wiU get surcharged besides
with the fluids which are expelled from the extremities, by the con-
traction of the blood-vessels caused by cold." In close rooms, not
well ventilated, stoves exert this baneful influence upon the air in an
eminent degree. This objection lies against Jieated air, no matter how
heated. Stoves and air-furnaces, with their red-hot surfaces, are un-
doubtedly worse for the air than hot-water apparatus, which never
Bcorch it ; yet they, too, may pour into our apartments a withering
blast of air at 150°, which may be potent for mischief. The only way
that hot-air can be made healthful and desirable is by an effectual plan
of artificial evaporation, which will be noticed among the means of
preserving atmospheric purity (347).

309. CotttaminatioE of Air from the Hnman Being. — It is a common
belief that the human system is distinguished by its vital power of re-
sisting, during life, the physical agents which would destroy it ; but
that after death it is abandoned to these forces, and falls quickly into

EXHALATIONS FEOM THE LTVTKG BODY. 171

putrefaction. This is an error. Under the influence of physica]
agency decomposition is constantly going on throughout the body, and
is indeed the fundamental condition of its life (624). There is the
same decay and chemical decomposition taking place in the animal
fabric during life as after death ; the difference being, that in the dead
body the decomposing changes speedily spread throughout the mass,
while in the living system they are limited and regulated, and pro-
vision is made for the incessant and swift expulsion of those effete
and poisonous products of change, which if retained within the organ-
ism for but the shortest time, would destroy it. Streams of subtile
and almost intangible putrescent matter are, all through life, exhaling
from each living animal body into the air. The fluid thrown from the
lungs and skin is not pure water. It not only holds in solution car-
bonic acid, but it contains also animal matter^ the exact nature of
which has not been determined. From recent inquiries, it appears to
be an albuminous substance in a state of decomposition. If the fluid
be kept in a closed vessel, and be exposed to an elevated temperature,
a very evident putrid odor is exhaled by it. Leblano states that the
odor of the air at the top of the ventilator of a crowded room, is of
so obnoxious a character that it is dangerous to be exposed to it, even
for a short time. If this air be passed through pure water, the water
soon exhibits aU the phenomena of putrefactive fermentation.

310. Dr. Faraday's Testimony apou this point. — " Air feels unpleasant
in the breathing cavities including the mouth and nostrils, not merely
from the absence of oxygen, the presence of carbonic acid, or the ele-
vation of the temperature, tut from other causes depending on matters
communicated to it from the human heing, I think an individual may
find a decided difference in his feelings when making part of a large
company, from what he does when one of a small number of persons,
and yet the thermometer give the same indication. "When I am one
of a large number of persons, I feel an oppressive sensation of closeness,
notwithstanding the temperature may be about 60° or 65°, which I
do not feel in a small company at the same temperature, and which I
cannot refer altogether to the absorption of oxygen, or the inhalation
of carbonic acid, and probably depends upon the effluvia from the many
present ; but with me it is much diminished by a lowering of the tem-
perature, and the sensations become m.ore like those occurring in a
small company."

311. Air of Bedrooms.— The escape of offensive matters from the liv-
ing person becomes most obvious when from the pure air we enter an
nnventilated bedroom in the morning, where one or two have slept

172 SOUECES OF IMPURE AIE EST DWELLESTSS.

the night before. Every one must have experienced the sickening and
disgusting odor upon going into such a room, though its occupants
themselves do not recognize it. The nose, although an organ of ex-
quisite sensibility, and capable of perceiving the presence of offensive
matters where the most delicate chemical tests faD, is nevertheless
easily blunted, and what at the first impression feels pre-eminently dis-
gusting, quickly becomes inoffensive. Two persons occupying a bed for
eight hours, impart to the sheets by insensible perspiration, and to the
air by breathing, a pound of watery vapor charged with latent animal
poison. Where the air in other inhabited rooms is not often changed,
the water of exhalation thus loaded with impurities, condenses upon
the furniture, windows, and walls, dampening their surfaces and run-
ning down in unwholesome streams.

312. Pnrity the Intention of Nature. — Yet we are not to regard the
human body as necessarily impure, or a focus of repulsive emanations.
The infinite care of the Creator is seen nowhere more conspicuously
than in the admirable provision made for the removal of waste matters
from the system, the form in which they are expelled, and the prompt
and certain means by which nature is ready to make them inoffensive
and innq?ious. " The skin is not only," as Biohat eloquently observes,
" a sensitive limit placed on the boundaries of man's soul, with which
external forms constantly come in contact to establish the connections
of his animal life, and thus bind his existence to all that surrounds
him ; " it is at the same time throughout its whole extent densely
crowded with pores, through which the waste substances of the system
momentarily escape in an insensible and inoffensive form, to be at once
dissolved and lost in the air if this result le alloxced. It is not by the
natural and necessary working of the vital machinery that the air is
poisoned, but by its artificial confinement and the accumulation of
deleterious substances. If evil results, man alone is responsible.

313. Other sources of Impurity. — Gaseous exhalations of every sort
escape from the kitchen, and are diffused through the house as their
odors attest, and the darkening of walls and wood-work painted with
white lead shows that poisonous sulphuretted hydrogen from some
source has been thrown into the air, its sulphur combining with the
lead and forming black sulphuret of lead.* From the imperfect com-
bustion of oil and tallow for lighting, and the defective burning of gas
jets there arise emanations often most injurious to health. The vapor
of a smoky lamp, if disengaged in small quantities, and the fumes of
the burning snuff of a candle, may fill the room with disgusting odors

♦ White zinc paint does not tlius turn black.

INFLUENCE OF CELLAES AND BASEMENTS. lYS

and excite severe headache. It may be well here to correct the com-
mon fallacy that cold air is therefore pure, and that apartments need
less ventilation in winter than in summer. People confound coolness
with freshness, and disagreeable warmth with chemical impurity;
whereas these properties have necessarily nothing to do with each
other. Cold air may be ii-respirable from contamination and warm air
entirely pure.

314. Poisonons Colors on Paper Hangings. — Attention has lately been
called to the poisonous influence of green paper hangings upon the air.
Cases are mentioned of children poisoned by chewing green colored
hanging paper, and of persons sickened by breathing air in rooms in
which certain green papers have been mounted. The basis of the bright
green colors used for staining paper-hangings is the poisonous arsenite
of copper^ a combination of arsenic and copper. This, however, is not
volatile, and does not create poisonous fumes or vapors, unless perhaps
by being dusted fine particles are loosened and set afloat in the air.
Nevertheless, though it do not vaporize and get into our systems
through the lungs, arsenite of copper is a deadly poison, and when
spread over paper-hangings, utterly spoils them/br dietetical purposes,
either for children or adults. Professor Johnson, of New Haven, states
that the most beautiful of all green pigments is the aeeto-arsenite of
copper^ and that this compound, in damp weather and humid situations,
exhales deadly poisonous vapors supposed to contain arsenuretted
hydrogen. This gentleman has given an account of a family poi-
soned by sleeping in a room where the paper was colored with this
pigment.

815. Fonl Air generated in Cellars. — The air in our houses is also liable
to contamination from various organic decompositions, if vigilant
precaution is not taken to prevent it. Cellars are commonly con-
verted into reservoirs of pernicious airs, by the reprehensible custom
of using them as receptacles for the most perishable products. But
even where large masses of organic matter are not left to undergo
putrefactive decay, and generate unwholesome miasms, serious injury
is liable to occur from the damp and stagnant air of basements and
cellars. It is not necessary that the lower spaces of a house should
be half filled with rotting garbage to generate foul air. The surface
of the earth is filled with decomposable substances, and whenever air
is confined in any spot in contact with the ground, or any changeable
organic matter, it becomes saturated with various exhalations which
are detrimental to health. If air is to be confined, unless it is so
sealed up as to touch nothing but dry, glassy or mineral substances,

174 MORBID AND FATAL EFFECTS OF IMPUEE AIE.

it will certainly degenerate. Even dry rooms and closets in the upper
part of tlie house, become mouldy and musty to a most disagreeable
extent, if not often aired. To be pure and healthy, air requires con-
tinual circulation; but cellars are very rarely either ventilated or
made absolutely dry by water-proof walls or floors. They are usually
damp, cold, uncleanly, and mouldy. " The noxious air generated in
cellars, basements, and under-floor spaces, reaches the inhabitants of
upper apartments in so small quantities, that instead of producing
any marked and sudden process of disease, it operates rather as a
steady tax upon their income of health ; so uniform in its depressing
effects as not to be appreciated. Yet many an invalid, who fancies
himself improved by a change of air, in going to another residence,
is really relieved by escaping the mouldy atmosphere which comes
from beneath his own ground-floor." *

V. MORBID AND FATAL EFFECTS OF IMPURE AIR.

316. Sources of danger in Breathing — The constituent of the atmo-
sphere are mingled in such perfect proportions, that its temper is ex-
actly suited to the necessities of the healthy system ; any alteration
in its composition, therefore, however slight, must result in physi-
ological disturbance. So direct is the access that respiration aflDords
to the inmost recesses of the body, that any gas mingled with the re-
spired air, is at once admitted, and takes prompt control of the system.
When aliment is taken into the stomach, it is submitted to a long
process of preparation and sifting, before it can gain admission to the
blood, those parts which are useless or obnoxious being rejected;

* " The reports of the Eegistrar-Genera of England disclose to us some very startling
facts in reference to the slow influences of different states of air in affecting length of
life. If any one were to select from among all the different occupations the healthiest
men of a nation, he would probably choose the farmers and the butchers. Both arc-
usually stout in frame, and ruddy in complexion. Both are actively employed, have
plenty of exercise and abundance of food. In one point, therefore, their circumstances
widely differ. The farmer breathes the pure air of the country ; the butcher inhales the
atmosphere of the shambles and the slaughter-house, tainted with putrefying animal
effluvia. The result is an instructive lesson as to the value of pure air. The rate of deaths
stated among the farmers, between the ages of 45 and 55, was 11'99 per thousand
(annually). The butchers at the same age died at 231 per thousand, so that their mor-
tality is about double that of the farmers. These two classes, indeed, occupy nearly the
extremes of the table of mortality. The farmer is the healthiest man on the list, while
there is but one worse off than the butcher — the innkeeper. Any one who knows how
large a proportion of taverns are mere grogshops, reeking with impurities and environed
in filth, will not be surprised that the mortality among this class ascends to 2S'84 in the
thousand."

rr PREPAEES THE WAT FOE PESTILENCE. 175

but the Inngs exercise no sucli protective or selective power, they
cannot guard the system by straining the air, or barring out its in-
jurious gases. Besides, air both pure and impure is alike transparent
and invisible, so that the eye cannot detect the difference. The
causes of vitiation are also gradual and insidious in their action,
so that their effects steal imperceptibly over the system. Unlike
heat, deleterious air announces its presence by no sensation ; indeed,
its effects are of that stupefying kind that makes a person insensible
to them. A bedroom, as we before remarked, may be so foul from
loathsome exhalations, as to nauseate a person who enters it from the
pure air, and yet its inmates will feel quite unconscious of any thing
disagreeable. Without intelligent and thoughtful precaution, there-
fore, we are constantly liable to the evil effects of foul air, and to im-
minent danger from various forms of disease.

317. The System prepared to receive Contagion. — Eespiration of im-
pure air, is a prolific source of disease, which appears in numerous
forms and all degrees of malignity. The effect of breathing a con-
fined and unrenewed atmosphere, is not only to taint the air, but by a
double influence, to taint also the blood. It is an office of oxygen in
the body, as we have seen, to throw the products of waste into a
soluble state that they may be readily excreted, but if its quantity be
diminished in the air, this work is imperfectly performed in the body ;
and the vital current is encumbered with putrescent matter. The
increase of carbonic acid in the air, by offering a barrier to exhalation
from the lungs, conspires to the same result. Accumulation of these
morbid products in the blood, greatly heightens its susceptibility of
being acted upon by atmospheric malaria, the causes of epidemics.
The blood is supposed, under these circumstances, to acquire a fer-
mentable state, forming, as it were, a ready prepared soil for the seeds
of infection. Atmospheric malaria seem not capable alone of producing
epidemic disease. From those in real robust health, with perfect
sanative surroundings, the arrows of contagion rebound harmless.
The miasmatic poison mmt jindL some morbidity in the system to co-
operate with, — some unhealthy condition induced by intemperence or
debauchery, bad food or drink, bodily exhaustion, mental depression,
or the discomforts of poverty — upon which it may take effect. But
of all these predisposing agencies, none invite the stalking spectre of
pestilence with so free and deadly a hospitality, as corrupt, con-
taminated air.

318. Blnstration in the case of Cholera. — Of the tendency of an at-
mosphere charged with the emanations of the human body, to favor

176 MORBID AND FATAL EFPECTS OF IMPUEE ATR.

the spread of contagious disease, the illustrations that might be quoted
are innumerable. Take an instance of cholera, for example. It is
■well known to those who have had the largest opportunities of study-
ing the conditions which predispose to this malady, that overcroioding
is among the most potent. In the autumn of 1849, a sudden and
violent outbreak of cholera occurred in the workhouse of the town
of Taunton (England), no case of cholera having previously existed,
and none subsequently presenting itself among the inhabitants of
the town, though there was considerable diarrhoea. The building
was badly constructed, and the ventilation deficient ; but this was
especially the case with the school-rooms, there leing only about 68
cubic feet of air for each girl, and even less for the boys. On Nov. 3d
one of the inmates was attacked with the disease ; in ten minutes
from the time of the seizure, the sufferer passed into a state of hope-
less collapse. "Within the space of 48 hours, from the first attack, 42
cases and 19 deaths took place; and in the course of one week, 60
of the inmates, or nearly 22 per cent, of the entire number were
carried off; whilst almost every one of the survivors suffered more
or less, from cholera or diarrhoea. Among the fatal cases were those
of 25 g iris and 9 boys, and the comparative immunity of the latter, not-
withstanding the yet more limited dimensions of their school-room,
affords a remarkable confirmation of the principle we are indicating,
for we learn that " although good and otedient in other respects, the
hoys could not ie Tcept from hreaMng the windoics,^'' so that many of
them probably owed their lives to the better ventilation thus established.
In the jail of the same town, in which every prisoner was allowed
from 800 to 900 cubic feet of air, and this continually renewed by an
effcient system of ventilation, there was not the slightest indication
of the epidemic influence. (Dr. Oaepeisttee.) It is in confined spaces
thus charged with putrescent bodily exhalations, that pestilence revels ;
they resemble in fatality those localities where the air is poisoned
by effluvia from foul drains, sewer-vents, slaughter-houses, and manure
manufactories.

319. Fevers originate ia Impure Air. — As with cholera, so also with
fevers ; foul air not only augments their malignity, but also calls them
into existence. "Writers on pestilence, observes Dr. Geiscom, note two
distinct species of virus applied to the body, through the medium of the
air. First, that arising from the putrefaction of dead animal and vege-
table matter — the accumulations of filth around dwellings and in cities,
and the exhalations of swamps, grave-yards, and sewers, called marsh
miasm. This is supposed to give rise to yeUow, remittent, bilious,

rr PEODUCES fevees and sceofula. 177

and intermittent fevers, dysentery, and perhaps also cholera. And
second, exhalations from the human body, confined and accumulated
in ill -ventilated habitations, sometimes termed typhoid miasm, and
which usually gives origin to common typhus and low nervous fevers.
It . would thus appear, that the very type and character of febrile
disease is determined by the Hiid of impurity which is breathed.
Prof. Smith, of New York, says, "Let us suppose the circumstances
in which typhus originates, to occur in summer, such as the crowd-
ing of individuals into small apartments badly ventilated, and ren-
dered offensive by personal and domestic filth ; these causes would
obviously produce typhus in its ordinary form. But, suppose there
exist at the same time, those exhalations which occasion plague, and
yellow fever, or remittent and intermittent fevers; tinder such cir-
cumstances we would not expect to see any one of those diseases fully
and distinctly formed, but a disease of a new and modified character.
It is, therefore, beyond probability that a few deleterious gases are
quite sufficient to produce an infinite variety of pestilential and con-
tagious maladies."

320. Scrofnla, or Struma, the consequence of Impure Air. — There is a
diseased condition of body known as scrofulous or strumous, which
manifests itself in various forms, and in all parts of the system. It
seems to be a result of deficient nutrition ; that is, not a want of
material for nutricious purposes, but a failure of power to produce
healthy and perfect tissue from the elements of food. Various causes
have been assigned as tending to produce scrofulous habits of body,
such as hereditary tendency, bad diet, depressing passions, too late,
too early, or in-and-in marriages, sedentaiy occupations, want of ex-
ercise, deficient clothing, bad water, &c., and these, under different cir-
cumstances, may each contribute to the result ; but imperfect respira-
tion is probably the most efficient and universal cause. An eminent
French Physician, * who has made this subject a matter of extensive
study, says, "Invariably it will be found on examination, that a truly
scrofulous disease is caused by a vitiated air, and it is not always neces-
sary that there should have been a prolonged stay in such an atmosphere.
Often a few hours each day is sufficient, and it is thus that persons may
live in the most healthy country, pass the greater part of the day in
the open air, and yet become scrofulous, because of sleeping in a
confined place, where the air has not been renewed." The same ob-
server goes further, and affirms that the repeated respiration of the
same atmosphere, is a primary and efficient cause of scrofula, and

* M. Baudoloqub.

178 MOEBID AND FATAL EFFECTS OF IMPUEB AIR.

that, " if there be entirely pure air, there may be bad food, bad cloth-
ing, and want of personal cleanliness, but that scrofulous disease can-
not exist." In 1832, at Norwood School in England, where there
were 600 pupils, scrofula broke out extensively among the children,
and carried oflE" great numbers. This was ascribed to bad and inef-
ficient food. Dr. Arnott was employed to investigate the matter, and
immediately decided that the food "was most abundant and good,"
assigning " defective ventilation, and consequent atmospheric im-
purity " as the true cause.

321. Consnmptioa indaced by Impure Air. — When scrofula localizes
itself in the lungs, there \s pulmonary or tubercular consumption. The
essence of the nutritive process consists in the vital transformation of
albumen (678) into fibrin and organized tissue. Now the tubercles
which in this disease make their appearance in the pulmonary
organs, consist of crude, coagulated, half organized masses of albumen
— the abortive products of incomplete nutrition. In this manner,
bad air, by producing the strumous condition, becomes a cause of con-
sumption. It seems natural to expect that the organs with which
the foreign gaseous ingredients of the atmosphere come more im-
mediately into contact, and whose blood-vessels they must enter on
their passage into the system, should feel, in a distinctive manner,
their noxious influence ; and this expectation is strengthened by
observation, and experiment upon both men and animals. It has
been observed that when individuals habitually breathe impure air,
and are exposed to the other debilitating causes which must always
influence, more or less, the inhabitants of dark ill-ventilated dwellings,
scrofula, and consumption, as one of its forms, are very apt to be
engendered.

322. State of the Air influences Infant Mortality. — The same malign in-
fluence of the air of unventilated rooms is seen in the mortality of
infants. That the new-born and tender child should be infinitely sus-
ceptible to the influence of contaminated air is what we might well
expect. We are, therefore, not surprised, that in the foul and stifling
air of Iceland habitations, two out of three of all the children should
die before twelve days old. Opportunities have been afibrded in hos-
pitals, to compare the effects of pure and vitiated air, and it has been
invariably found that a neglect of atmospheric conditions was accom-
panied by high rates of infant mortality, which promptly disappeared
with the introduction of efficient ventilation. " On the imagination of
mothers, educated as well as ignorant, the feeling still seems to be
Btereotyped, that the free, pure, unadulterated air of heaven falls upon

IT BEEAKS DOWN CONSTlTUTlONAIi VIGOE. 179

the brow of infancy as the poppies of eternal sleep, and enters the
lungs and circulates as a deadly poison ; and still the ' shawls and
blankets,' sleeping and awake, are pretty generally employed to de-
prive the objects of the most rapturous paternal solicitude, of what
was originally breathed into the nostrUs of the great archetype of the
human race as the ' breath of life.' "

323. Bad Air nndernunes the Vital Powers. — And yet the fatal effects
of mephitic air are by no means confined to those terrible maladies,
Cholera, Fevers, Consumption, and Infantine disease, by which the
earth is ravaged ; by undermining the health it paves the way for aU
kinds of disorders. The human system is armed with a wonderful
protective or conservative power, by which it is able to resist the in-
vasion of morbific agencies. Indeed, this power of resisting disease is
perhaps a more correct measure of the real vigor of the body than its
outward appearance of health. Individuals may often continue for
years to breathe a most unwholesome atmosphere without apparent
ill-effects ; and when at last they yield, and are prostrated, or carried
off by some sudden disease, the result is attributed to the more ob-
vious cause, the long course of preparation for it by subtle and insidi-
ous poisoning being entirely overlooked. The mass of mankind refuse
to recognize the action of silent, unseen causes. Our youth in the
morning of their days, and men in the meridian of their strength,
pass abruptly away, and we wiU be satisfied with no solution of the
problem which refers the mournful result to reprehensible human
agency.* " The action of contaminated confined air has been shown,
to be the most potent and insidious of mortiferous agencies. Any ad-
dition to the natural atmosphere that we breathe must be a deterio-
ration, and absolutely noxious in a greater or less degree ; and health

* " It is evident that the depressing effects of foul air are not confined to those cases In
which the immediate results of its poison are seen. Because it requires a given quan-
tity of carbonic acid in the air to exhibit decided effects, it does not follow that a much
lower proportion does not seriously impair the vital energies, and especially the power
of resisting disease. We are firmly convinced that many a case of scarlet fever or of
measles proves fatal on account of an unperceived depression of the little sufferer's
Btrength by previous continued exposure to an atmosphere tainted with carbonic acid
and other exhalations from his own lungs. We know that all diseases of low grade, such
as typhoid and typhus fever, prevail to a very great extent in ill ventilated houses ; we
know that an epidemic inflammation of the eyes has been frightfully prevalent in the
Irish work-houses, and that it has been traced to imperfect ventilation, the eye-disease
being merely the index of the general depression of the vital powers ; we know, too,
that in one of the Trans-Atlantic Hospitals, the mortality went down from forty in a
thousand to nine, upon the adoption of a proper system of ventilation, and that it rose
again to 24 on the subsequent abandonment of that system. These are only illustra-
tions ; hosts of similar facts could be cited from the records of medical science."

180 MOEBID AND FATAL EFFECTS OF IMPURE AIR.

would immediately suffer, did not some vital conservative principle
accommodate our functions to circumstances and situation. But this
seems to get weaker from exertion. The more we draw on it, the less
balance it leaves in our favor. The vital power, which in a more
natural state would carry the body to seventy or eighty years, is pre-
maturely exhausted, and like the gnomon shadow, whose motion no
eye can perceive, but whose arrival at a certain point in a definite time
is inevitable, the latent malaria, which year after year seems to inflict
no perceptible injury, is yet hurrying the bulk of mankind, with un-
deviating, silent, accelerating rapidity, to an unripe grave. It should
never be overlooked, that by breathing pent-up effete air, all the ad-
vantages of an abundance of fuel, and every blessing of a genial sky
are utterly thrown away, and though the habitation were on the hill-
top, fanned by the sweetest bi'eezes of heaven, it would become the
focus of contagious and loathsome disease, and of death in its most
appaUing aspect. On the other hand, even in the confined quarters oi
a crowded city, rife in malaria, and where pestilence is striking whole
families and classes, ventilation and warmth, with cleanliness, thei?
usual attendant, like the sprinklings on the lintels and door-posts of--
the Ilebrew dwellings, stand as a sign for the destroying angel, as hs
passes over, to stay his hand, for in the warm, fresh-aired chamber
none may be smitten." — (Beenan.)

324. Morbid Mental Effects of Bad Air. — Dr. Robeetson remarks-
" The health, the mental and bodily functions, the spirit, temper, dis-
position, the correctness of the judgment and brilliancy of the imagin-
ation depend directly upon pure air." This is strongly put, but it is not
an overstatement. As the inflowing stream of air is the imminent and
instant condition of physical life, so it is the immediate material agent
charged with the exalted function of establishing and maintaining the
connection of mind and body. It is air acting definitely and quauti-
tively through the bodily mechanism, that sustains the order and ac-
tivity of the mind's faculties. Mind is thus physiologically condi-
tioned, and one of the mighty tasks to which science must gird itself in
the future is to work oxit the analysis of these conditions. Mr. Paget,
the eminent English physiologist, remarks : " The health of the mind,
so far as it is within our own control, is subject to the same laws as is
the health of the body. For the brain, the organ of the mind, grows,
and is maintained according to the same methods of nutrition as every
other part of the body ; it is supplied by the same blood, and through
the blood, like any other part, may be affected for good or ill by the
various physical influences to which it is exposed. But I will not

MENTAL DISTUKBANCE AND DEPRESSION. 181

dwell on this more than to assert, as safely deducible from physiology,
that no scheme of instruction or of legislation can avail for the im-
provement of the human mind, which does not provide with equal
care for the weU-being of the human body. Deprive men of fresh air
and pure water, of the light of heaven, and of suflBcient food and rest,
and as surely as their bodies will become dwarfed, and pallid, and dis-
eased, so surely will their minds degenerate in intellectual and moral
power." The immediate effect of breathing impure air is to cloud the
mind's clearness, to dull its sharpness, and depress its energy. All the
mental movements are clogged, each faculty suffering restraint and
perversion. The wings of the imagination are clipped, reason loses its
keenness of penetration, and the judgment its acuteness of discernment
and perspicacity. When we breathe bad air, the impressibility of the
mind is diminished ; if we undertake to study, we can neither under-
stand so clearly, nor remember so well as if the air were pure. So-
cially we become less interesting, the spirits fall, conversation flags,
dulness supervenes, we get impatient and irritable, and there is too
often a resort in these circumstances to artificial exhilarants, and stim-
ulants to afford relief, which would be better secured by freshness and
purity of the atmosphere.

VI.— RATE OP CONTAMINATION WITHIN DOORS.

325. Oxygen withdrawn by Respiration. — Any scheme for the removal
of foul air from an apartment, and the introduction of fresh air in its
place, involves the previous inquiry, how rapidly ought this change to
be made ? Our next question, then, is at what rate does the air in
dweUings become contaminated ? The amount of air taken into the
system by different ii.dividuals, varies greatly according to age, capa-
city of lungs, rate of exercise, and many other circumstances. Hence
there is much discordance in the results of inquiries made by different
physiologists. The disagreement is also much owing to the difficulties
attending this kind of experimenting. If we take as the basis of our
calculation Coathtupe's estimate, the lowest that we can find, we shall
assume as an average, that there are 20 respirations in a minute, and
at each respiration, 16 cubic inches of air pass in and out of the lungs.
This is equal to 320 cubic inches per minute, 19,200 per hour, 460,800
cubic inches or 266 1 cubic feet per day of 24 hours. Yieroedt makes the
quantity 306f cubic feet, ScHAULiifa 361 cubic feet ; and YALENTra- as
high as 398| cubic feet per day. As ^ of the air is oxygen, there will be
four cubic inches of this gas taken into the lungs at each inspiration. Of

182 BATE OP CONTAMINATION WITHIN DOOES.

this quantity, very nearly one half is absorbed and enters the blood.
We may safely assume that 35 per cent, of the oxygen is thus absorbed
at each breath, or 7 per cent, of the entire air. The quantity of oxygen
consumed will be 22 to 24 cubic inches per minute, 1344 cubic inches or
3-4ths of a cubic foot per hour, and 18"6 cubic feet per day. A person,
therefore, robs of all its oxygen nearly four cubic feet of air per hour,
and diminishes its natural quantity 5 per cent, in 80 cubic feet per
hour, or li cubic feet per minute.

326. Proportioa of Carbonic Acid exhaled by Respiration. — ^When carbon
is completely burned in pure oxygen, the carbonic acid gas produced
occupies exactly the space that the oxygen did before burning. If all
the oxygen absorbed by respiration was converted into carbonic acid
in the system, the volume of this compound gas restored to the air
would be exactly equivalent to the oxygen withdrawn. But a portion
of oxygen unites with hydrogen and sulphur, forming water and sul-
phm-ic acid, while a small part of the carbonic acid generated within
the body escapes into the air through the pores of the skin. The con-
sequence is, that the bulk or volume of carbonic acid expelled from
the lungs is not quite equal to that of the oxygen absorbed. Assuming
the quantity of carbonic acid in the expired air to be 5 per cent., it
will be one hundred times greater than the natural amount in the at-
mosphere (280). A person, therefore, by breathing adds 1 per cent,
of carbonic acid to 55^ cubic feet of air in an hour, or would vitiate
to this extent nearly one cubic foot in a minute.

327. Oxygen withdrawn by Combustion. — The amount of combustion
varies so widely with the kind of fuel used, the mode of burning it,
the quantity of heat required, and other circumstances, that we can
approach nothing like an average estimate of its influence upon the
air in a given time. It is known with certainty how much oxygen
given weights of the different fuels require for combustion, but the
amount withdrawn from the air of a room depends entirely upon the
rapidity with which it is consumed. A pound of mineral coal requires
the oxygen of 120 cubic feet of air to burn it (90). If five pounds
are consumed in an hour, at least 600 cubic feet of air must be re-
moved from the room. Combustion of fuel, however, does not, like
respiration, decompose the air, separating the life-sustaining element,
and leaving the residue in the apartment. If properly conducted, it
removes the air from the room unchanged, and having decomposed it
in the fire, dismisses the contaminated product through the flue. Very
often, however, when fires get low and draughts feeble, there is a re-
fluence of foul gases into the apartment (121).

BY LIGHTING AISTD LOSS OF MOISTURE. 183

328. Air Titiated by Eluminating Processes. — The case is different when
combustion is employed for illuminating purposes, as in the burning
of candles, oil, and gas ; these, like the body in respiration, alter the
air within the room. A candle (six to the pound) wiU consume one-
third of the oxygen from 10 cubic feet of air per hour, while oil
lamps with large burners will change in the same way 70 feet per hour.
As the degree of change in the air corresponds with the amount of
light evolved, it is plain that gas-illumination alters the air most
rapidly. A cubic foot of coal-gas consumes from 2 to 2|- cubic feet of
oxygen, and produces 1 to 2 cubic feet of carbonic acid. Thus every
cubic foot of gas burned imparts to the atmosphere 1 cubic foot of
carbonic acid, and charges 100 cubic feet with 1 per cent, of it, making
it unfit to breathe. A burner which consumes 4 cubic feet of gas
per hour, spoils the breathing qualities of 400 cubic feet of air in
that time (224).

329. Inflaence of Moisture upon the quantity of Air required. — It has
been noticed that air which is either very dry, or very moist and
damp, is disagreeable and unwholesome. It should not contain so
little moisture as to dry and stimulate the skin ; nor so much that it
wiU not readily receive the insensible perspiration which constantly
flows to the surface. The amount of watery vapor emitted from the
body has been stated at from 20 to 40 ounces per day. Estimates
upon this point vary. If one of each sex be taken, the mean exhala-
tion win be about 23 grains per minute. ITow let us suppose the air
of a room to be at 70°, and that it has to be cooled 20° before it
begins to deposit moisture, that is, its dew-point is at 50°. The cubic
foot of air at 50° contains 4'6 grains of moisture, and at 70° it will
hold 8*4 grains, so that it is capable of dissolving 3*9, or nearly 4 grs.
of water. Of air in this state, it will require about 6 cubic feet per
minute to dissolve and remove the insensible perspiration from the
skin. If the dew-point be lower, the air will take up more water, and
less of it will be required to evaporate the moisture of the body.
But if the dew-point be higher, the air will receive less moisture, and
the system will require a larger supply. If the dew-point is at 60°
and the temperature of the air at 70°, a cubic foot of it wUl become
saturated by the addition of 2*17 grains, so that 10 feet per minute
would hardly carry off the cutaneous exhalation. To be pleasant, air
must not be deficient in moisture ; if it be nearly saturated, it can im-
bibe but little, and consequently much of it must be brought in con-
tact with the system ; and this necessarily involves large provision for
change of air.

184 BATE OF CONTAMINATION WITHIN DOOKS.

330. Air vitiated by one person in a niinnte. — These sources of impurity
are capable of measurement in their rate of effect, hut there are other
influences so irregular in action that the results they produce cannot
be estimated. The whole quantity of air tainted by emanations from
the person, and which requires removal, is variously stated by different
authorities at from 3^ to 10 cubic feet per minute. We are of opinion,
that for the restoration of its lost oxygen, the removal of carbonic
acid, insensible perspiration, and the peculiar effluvia of the living
body, there are required, at the lowest estimate, 4 cubic feet of air
in a minute, or 240 per hour. But this may be much too low.
It is evident that the nearer the air breathed within doors, approaches
in purity and freshness to the free and open atmosphere, the better
will it conduce to health, strength, and length of life. As far as pos-
sible we ought not to limit ourselves to that supply which the consti-
tution can bear or tolerate, but to that amount which will sustain the
highest state of health for the longest time. And yet, as Dr. Eeid
remarks, the question of the amount of air to be supplied may be con-
sidered in some respects in an economical point of view, in the same
manner as the table any one can afford to sustain, the house in which
he may dwell, or the clothing he may put on. Although pure air is
the most abundant of all things, yet in our plans of living it is by no
means free of cost (363),

381. InHncnce of size of Apartments, — The smaller an occupied room,
the sooner, of course, will the stock of pure air contained in it be ex-
hausted and replaced by foul air. Three persons sitting in a tight
room 8 feet high, and 12 by 14 square, will vitiate all its air in two
hours. If they use lights, the air wiU be spoiled much quicker.
Twelve persons sitting in a parlor 16 by 20 and 9 feet high, will make
its air unbreathable without the assistance of either fire or lights in a .
single hour. Two persons sleeping in a close bedroom 10 feet square
by 8 high, wiU render all its air unfit for respiration in less than two
hours. In actual practice, the cases are not quite so bad as this, for
with the utmost perfection of carpentry there will be cracks for the
passage of air, though perhaps in small quantities ; and the opening
and closing of doors cause intermixture and currents, and this some-
what delays the result. Where the rooms are capacious, the reservoirs
of air are more slowly contaminated, and if no means are taken to
remove the foul air and introduce that which is pure, large-sized rooms
are of the utmost importance. But no apartments of ordinary or prac-
ticable dimensions will enclose sufl&cient air for the agreeable and whole-
some use of their occupants. This must be attained in another way.

MOTIVE POWEB IN VKNTI LATION. 185

332. Influence of Plants upon the Air of Rooms. — The general action
of plants upon the air is antagonist to that of animals. In the day-
time, under the influence of light, they absorb carbonic acid from the
atmosphere by then* leaves, decompose it, and return pure oxygen to
the air, thus tending by a double action to purify it. The rate at
which these changes occur corresponds with the activity of growth.
The plant, however, derives a portion of its carbonic acid from the
soil, especially if it be rich, in decomposing organic matter, like the
garden mould of flower-pots. Compared with the ordinary rate of
contamination in occupied apartments, the purifying effect of the few
green plants usually kejDt, is but small. In the absence of light, the
peculiar actions of the leaves are suspended, nay, reversed; they
now rather absorb oxygen, and give off carbonic acid, like ourselves.
Hence, in sleeping-rooms, their tendency would be to impurity of the
air, though the action is probably very slight. As respects moisture
plants are also like animals, constantly exhaling it through the pores
of their leaves. According to Hale's experiment, a sunflower weigh-
ing 3 lbs. exhaled from its leaves 30 ounces of water in a day. Plants
may therefore be a useful means of supplying dry air with the requisite
humidity.

VII.— AIR IN MOTION— CUERENTS— DRAUGHTS.

333. Two methods of purifying the Air. — Pure air may be secured iu
two ways : first and most perfectly by the removal of the vitiated at-
mosphere of the apartment, and its replacement by fi-esh air from out
of doors. This is the mechanical method, and is known as venti-
lation^— a term derived from the Latin word signifying wind. The
air may also be more or less perfectly cleansed by means of substances
which absorb, decompose and destroy its noxious ingredients. This
is the cJiemical method. It is useful only under certain circumstances,
and is not applicable in common cases (802).

334. Motive Power employed.— As ventilation consists in the move-
ment of masses of air, it implies some kind of moving force. On a
large scale, as for public buildings, revolving fans, pumps, bellows, &c.,
driven by steam-engmes or water-power, have been used to impart
movement to air. But these contrivances are impracticable for
dwellings. Wind power is often used as an aid in ventUation, but its
unsteadiness prevents us from depending upon it. The force gener-
ally resorted to in private residences to secure exchange of air
is heat.

186

AEB m MOTION — CUKRENTS — DEAUGHTS.

Fig. 72.

335. Currents of Air In Close Apartments. — Changes of temperature
externally give rise to unceasing commotions in the air — breezes,
"winds, and hurricanes. The same thing occurs within doors ; any
portion of air heated becomes lighter and causes an ascending current ;

any portion cooled becomes denser
and causes a descending current.
If a candle be lit in the middle
of a room (Fig. 72) where the
doors, windows and flues are
closed, and the air is motionless,
a set of currents wiU rise in the
centre of the room, spread out
near the wall, to its sides, then
descend and return along the floor
to the centre again. The arrows
in the diagram show the direction
of the currents in a section of the
apartment. Fig. 73 shows the
dkection of the currents along the floor, that is, on a plan, as it
is termed. If the arrows (Fig. 73) were reversed, they would show
the course of the currents at the top of the room. If a lump of ice
be substituted for the candle, currents are again produced, but they
are exactly reversed in direction (352). The air descends from the

cold ice, and the currents on the
floor run outwards. In each of these
cases, the currents above and below
are opposite. AU local disturbances
of temperature tend to produce simi-
lar effects, although the currents are
commonly much interrupted by dis-
turbing forces. Of course several
lights would occasion several cur-
rents, which would mutually inter-
fere with each other. A stove in
the centre of the room produces just
such a movement of air as we have
seen established by the candle ; but
if placed at one side, the hot-air ascends on that side and descends on
the opposite.

836. Natural Ventilation of the Person. — The warmth of the human
body imparts itself to the layer of surrounding air, expands it, and

Fig. 73.

DOWNWAED CUEEENTS IN WINTEE FEOM WrNDOWS. 187

Fig. 74

causes a rising current (lOY). "When the temperature of the room is
65°, the body is 33° warmer, while 4° added to the circumjacent air
will cause it to ascend and escape above the head. The simple
presence of an individual in a room is therefore sufficient to throw
the air into movement and cause currents. The body thus acts pre-
cisely in the same way as a stove, and the presence of persons dis-
tributed through a room wUl add much complexity to the movements
of the air, and to a small extent counteract the stove-currents.

337. Windows, thoagb tight, produce Currents. — Windows, in cold
weather, though entirely tight, so that no air passes their crevices, are
always sources of descending curfents of air, with a corresponding
ascending movement (Fig. 74). When between the internal warm air
and the external cold air there is only one thin film of window-glass,
the heat escapes through it so fast that the air within is rapidly
cooled, condensed, and becomes heavier, so that a sheet of it is con-
stantly falling to the floor. This cascade
of cold air is frequently so sensible in
winter that persons are apt to suppose
it comes from some opening about the
window. These winter window currents
are often most injurious. If there be
draughts through the room, produced by
a fire or any other cause, they throw the
window current out of its direction more
or less to one side, so as frequently to
fall upon persons who suppose them-
selves to be safely away from any such
source of discomfort. Large windows
in public rooms, in vsdnter, should on
this account be carefully avoided, as the
cataract of cold air which they pour down upon the body is a fre-
quent cause of rheumatism, colds, and inflammations. Such sheets of
air often fall with mischievous effect upon sleepers, where beds are
placed near windows. It may be remarked that in summer these
currents are reversed; the heat, passing from without through the
window glass, rarefies the air in contact with it, which rises so that the
current passes in a contrary direction (289).

338. Tlie Air of rooms arranged in strata. — But the effect of currents
is not to cause a perfect intermixture with uniformity in the condition
of the air throughout the room. Indeed, the very cause that gives
rise to them is the tendency of cold air to fall into the lower place,

Currents produced in winter by
single windows.

188

AIK IN MOTION — CURRENTS — DEATJGHTS.

while it presses upward that which is warm and lighter. Hence, not-
withstanding its constant motion, the air is in fact arranged in layers
or strata, according to its temperature, the hotter air collecting near
the ceiling, and the layers decreasing in temperature downwards as
was previously stated (125). The difference of these temperatures is
Bometimes so considerable that flies will continue to liv;e in one stratum
which would perish in another. Now the warm and rarefied air which
rises to the upper part of the room contains also the impure air which
has been generated within it. The breath which escapes fi'om the
lungs, 20° or 30° warmer than the surrounding air, slowly rises above
the head, while ascending currents from the body carry upward all
its exhalations (334). So also the heated poisonous products of illu-
mination mount rapidly to the ceiling. The effect of currents is, to a
certain extent, to diffuse the foul gases throughout the apartment, but
chemical tests show the same stratification of impurities that the
thermometer indicated in regard to heat, the best ah* being below and
the worst above. In a room having a fireplace, the cold air may enter at
the top and bottom of a window, faU towards the floor and move
along near it to the flue, where it is discharged. In its progress, it
may even blow strongly upon a bed made on the floor, while all the
air above, enveloping a bedstead of ordinary height, remains loaded
with carbonic acid and aqueous vapor. In all ordinary rooms the
floor is swept by draughts of cold air, and is unfit for a sleeping place,
especially if the apartments have open fireplaces.

339. Simple openings do not produce Currents. — If an apartment be
opened to the external air, various movements are liable to occur, or

there will be
no motion at
all, according
to circum-
stances. It
by no means
follows that
because a
commimica-
tion has been
opened be-
tween a room

and the outer air, therefore currents wiU set in and an active inter-
change take place. Air will not leap out of a bottle because we ex-
tract the cork, nor out of a window simply because we open it. Cur-

FiG. 75.

Fig. T6.

50°

-^60-

-5&-

60'

Conditions in which openings in rooms do not produce
eschanire of air.

rNTERCHANGES THROUGH WINDOWS AND DOOES.

189

Fig. 77.

Fia. 78.

rents cannot be produced unless their causes are brought into action.
If a room be opened below, and the temperature within be higher
than that without, as represented in Fig. Y5, the outer, heavier air,
pressing harder than that withio, will confine it, no movement wiU
take place, and the strata wUl retain their relative positions undis-
turbed, as in the figure ; or, if the room be opened above, and the
external air be warmer than the internal (Fig. 76), the lighter air with-
out cannot press down to displace the inner, heavier air, which re-
mains without movement or disturbance of its arrangement.

340. Ciirreiits between rooms and external Am — If there be an open-
ing at the lower part of a room, and the external air be warmer
than that within, interchange takes place, the outward air displacing
that within by currents running as the arrows show (Fig. Y7), the
heavier air within falling or flowing out. If the opening be above,
and it be
warmer in-
side than
out, the light
air inside
wiU escape
upward, and
thecold,hea-
vy air with-
out flows in,
as shown in
Fig. 78. If

there be but a single opening to a room, although all other condi-
tions are favorable for a change, yet the counter currents meeting in
the passage conflict, and to a certain extent obstruct each other.
There should, therefore, be separate openings for currents of ingress
and egress.

341. Friction of counter-cnrrents of Air. — The importance of having
two independent openings to an apartment, if we desire to secure a
change of air, is shown by the following simple experiment : Take a bot-
tle with the bottom removed, or a lamp chimney (Fig 79), place under it
a short piece of burning candle in a shallow dish of water, so that no
air can get in from below ; now, although the stopper be removed so
that the inside of the bottle has direct communication with the outer
air, the candle will go out. Although there is a tendency of the
burnt air to escape and of the fresh air to rush in, yet they cannot
pass each other at the open mouth ; the currents conflict and the

Conditions in which openings in rooms produce exchange of air.

190

AIE m MOTION — CURKENTS — DBATJGHTS.

Fig. T9.

Fig. 80.

exchange does not take place. Yet, if a slip of paper be inserted in
the mouth of the bottle or lamp-glass, as seen in Fig. 79, thus dividmg
it into two distinct apertures, the lit candle will con-
tinue to burn. The foul air will pass out on one side
of the pasteboard and the pure air enter on the
other, as may be shown by the smoke from the snuff
of a candle held near ; it will be drawn in on one side
and carried up on the other. The purity of the air
within is thus secured. "When the opening, how-
ever, is sufficiently large, the currents pass without
difficulty, as is easily illustrated. If the door of a
warm apartment be opened, and a candle placed
^toe\S:%uwent°^ ^^ar it on the floor, the flame wiU be blown in-
wards ; if it be raised nearly to the top of the door
it will be blown outward, as illustrated in Fig. 80. The warm air
flows out at the higher openings. If the air of the room be warmer

than that without, it enters by all the
crevices near the bottom, and escapes
. by those near the top, and the reverse
if it be colder.

342. Currents throngli Windows. —
Draughts through windows and doors
are often not effectual in removing all
the air of rooms. In the case just
.instanced (Fig. 80), of the open door,
the cold air below enters and expels
^an equal portion of the warmer air,
' but only that will flow out which lies
below the level of the door-top. The
mass of air above this level will not
be displaced. If, however, the temperature of the room were at 60°,
and that of the outer air at 70°, an open door would evacuate the
room entirely of its airy contents ; the colder air in the room tending
to fall would pour out at the bottom, and the warm air enter at the
top to take its place. If a window be situated in the upper part of
the room and opened, its action is different, and in a manner opposite
to that of the door. "When the air is cold without and wann within,
and the window opened above and below, the apartment is emptied
and refilled as in Fig. 81. If the external air is warm and that within
cool, aU above the window sill is removed (Fig. 82), but the cold air
below that level continues undisturbed. By thus imderstanding the

Counter-currents in the doorway.

rNTERCHANGES THEOUGH WINDOWS AND DOOES.

191

Fig. 81.

Condition in wliich the air escapes
above.

conditions of inflow and outflow, we are enabled to regulate windows
having both sashes movable, and which are often valuable for venti-
lating private rooms. Although the interference of other causes is
liable to modify, and perhaps often
confuse and divert these movements,
yet they are quite sufficient to show
that the motion and rest of air are
controlled by laws as definite and reg-
ular as those which govern the mo-
tion and rest of water. Though infi-
nitely more light, mobile, and easily
agitated, yet it is never thrown into
commotion except by adequate and ap-
preciable causes.

343. How cnrrents of Air affect the Sys-
tem.— The sensations produced upon
the body by gently-moving currents of
air in proper conditions of temperature and moisture are extremely
agreeable, but in many cases streams of air directed against the per-
son become most injurious. Air at low temperatures of course has a
cooling efiect. We lose no more heat by radiation in moving air than
in still air, but by conduction we lose heat
in proportion to the velocity of the cur-
rent or the number of particles which
come in contact with the body. The cur-
rent also drives the cold air through the
clothing, displacing the warm air which
was entangled in its pores. Increased
evaporation, proportional to the dryness
and speed of the air, is also a further
source of cold. If the whole surface of
the body is exposed to the current, the
eflfect will be simply a general cooling
without any necessarily injurious effects.
But if the draught fall only upon some
one part of the body, it is hable to produce serious mischief, disturb-
ing the circulation and producing febrile movements, which may be
directed to the part exposed to the draught or even to remote organs,
iu either case often laying the foundation for serious and fatal disease.
This point should be particularly considered in introducing air in sum-
mer which has been artificially cooled (352) ; its diffusion should be

Fig,

Conditions in which the air
escapes below.

192 AEHAlfGEMENTS FOE VENTILATION.

very extensive and its velocity hardly perceptible. Of course we can-
not have ventilation without movement of air, but the motion should
be so moderated that we are not aware of it, and is always to be con-
sidered in connection with the two important conditions of tempera-
ture and moisture. We have made several trials to determine the ve-
locity which, as a general rule, with a proper regard to other condi-
tions, wiU not be found unpleasant, and give as the result about two
feet per second. It is evidently no greater than that with which we
should pass through still air when walking with the same velocity.
(Wyman.) Yet it is important that we be exposed to currents. Few
things are more favorable to taking cold than the confined and stag-
nant air of unventilated apartments. Just in proportion as we habit-
uate ourselves to such still, stagnant air, do we become sensitive to at-
mospheric changes, against which it is impossible perfectly to protect
ourselves on going out. The effect of a free internal circulation of air
in our rooms is therefore most salutary ; the more we are accustomed
to it, the safer we are in the vicissitudes of changing weather.

VIII.— AREANGEMENTS FOR VENTILATION.

344. The open Fireplace. — The mechanical expedients for securing
exchange of air in dwellings are numerous, but they are chiefly con-
nected with arrangements for heating. Wherever there is active com-
bustion in stove or fireplace, there must be a stream of air passing
out of the room through the chimney. If the room be absolutely
tight, so that no air can enter it, none will ascend, and if the fire be
kindled the chimney will smoke. A draught through a chimney im-
plies openings somewhere for air to enter the room, and thus there is
some ventilation as a matter of necessity. In noticing the heating ef-
fect of the fireplace, we saw that the open space above the fire con-
veys away a large amount of warmed air from the room, which took
no part in the combustion and wasted much heat. But this fault was
an advantage in respect of ventilation. The magnitude of the open
space above the fire represents the ventilating capacity of the chim-
ney. But it is from the air below the level of the mantel — the purest
in the apartment — that the fireplace is supplied. Only so much of
the foul imprisoned air above as gradually cools and descends, be-
ing swept into the chimney. When the weather is quite cold, the
briskness of the fire that is demanded, occasions a powerful draught
and produces annoying currents. So powerful were these draughts in
old times, that they were compelled to use a settle, a long bench with

ACTION OP FIREPLACES AND STOVES. 193

a high •wooden back, to protect the body from currents and retain the
radiant heat in order to keep warm. " It would be well for those who
question the importance of ventilation, because our forefathers lived
to a good old age without even understanding the meaning of the
word, to remember their fireplaces, the kind of dwellings they occu-
pied, and the quantity of air which must have passed through their
houses." It cannot be doubted that the changes which have of late
years been effected in the structure of the fireplace to secure the
greater economy of fuel — ^the contraction of its dimensions and the
lowering of the chimney-piece, by dimiaishing the amount of air that
was forced through the room to fill the capacious chimney, and by
bringing the foul-air space down more completely within the zone of
respiration — have been altogether unfavorable ; although, even in their
newer construction, open fires may be considered as affording a toler-
able amount of ventilation. Fresh air is well secured by the double
fireplace, which warms and introduces into the room a steady stream
of air from without. (111.)

345. Ventilation by Stoves. — As respects the condition of the air, the
exchange of even the low and contracted fireplace for the close and
stifling stove, has been eminently promotive of discomfort and disease.
Stoves afford the least ventilation of all our means of heating. They
take little more air than just sufficient to consume the fuel, and that
is withdrawn from the purer portion near the floor. In most cases of
the use of stoves, no provision whatever is made for the removal of
bad air. They may be made subservient to ventilation in several
ways ; first, by allowing air to pass through tubes in the body of the
stove ; second, by admitting it between the stove and an external
casing ; and third, by simply allowing it to strike upon the external
surface of the stove. In either case the entering air will be warmed,
rise toward the ceiling, and afterward gradually descend as the air
below is drawn off, producing a downward ventilation through the
whole apartment. Mr. Exjttan, of Coburg, 0. "W., has devised a plan
of heating and ventilating, strongly recommended by those who have
used it, although we have had no opportunity of seeing its operation.
He locates his 'au'-warmer' in the haU, or where required, brings in
the air from below, heats and transmits it through the building. For
the best working of his arrangement it is important that the house be
built with reference to it ; indeed, he insists that the general failure to
ventilate is because the architects fail to provide the necessary lungs
in the original construction of dwellings (362).

846. Ventilation by Hot-Air ArrangenientSi — Sources of warmth be-
9

194 AKEAKGEMENTS FOE VENTILATION.

come tlie most effective means of ventilation when air itself is made
the vehicle for conveying heat into the room, as in the use of hot-
water apparatus, furnaces, &c. The hot current enters through a
register, or guarded opening, and streams up at once to the ceiling ;
and by diffusion through the apartment, displaces the air already
present, which must find escape somewhere, and thus the renewal of
the breathing medium is constantly secured. Apartments warmed in
this manner require a chimney or other place by which air may escape.
The fireplace answers perfectly ; but under the impression that rooms
heated by air-currents require no channel of escape, houses have been
constructed with no flues at all. The air ought to be projected into
the room horizontally or at different points, so as to be weU diffused
(125). It should always be derived from perfectly pure sources, and
never used a second time. But the chief difificulty and danger, as
before noticed, is to be found in that condition of the air itself, which
results from its being suddenly heated (305).

347. The supply of Moisture. — The provision for supplying moisture
by evaporation is rarely any thing like adequate, a supply of 35 cubic
feet of air per minute introduced at the temperature of freezing and
heated to 90", is capable of taking up an ounce of water per minute,
or four pounds in an hour. Dr. Eeid states, that in ventilating the
English House of Commons, when it was crowded, he often exposed
the air furnished to 5,000 feet of evaporating surface, to impart the
necessary moisture, and sulsequently made the air flow through jets
of water. The artificial supply of moisture to air in the exact quan-
tity required, involves grave difficulties. The common method of
supplying humidity by simmering water in an open vessel, is glaringly
insufficient. A pan of water is placed in a furnace,* but of the torrent
of air that rushes through, how little is brought into contact with the
water. We place a vessel upon a stove with a few square inches of
water-surface, and fancy all is right, but the air may still be parching
dry. Where air in cold weather is introduced, suddenly rarefied by
heat, and actively changing, we have little conception of the amount
of moisture which must be artificially added to give to it soft and
balmy qualities. The best thing to be done of course is, to obtain the
largest possible evaporating surface. To accomplish this, a piece of
linen or cotton cloth dipped in a vessel of water, may be hung in folds
from any convenient framework or support. The cloth, by sponging

* Walker's furnace, manufactured by S. B. Jameb, No. T7 White street, New Yort,
Has large provision for evaporation, whlcli the proprietors offer to increase to any
extent that individuals may demand.

HEATING CONTEIVANCES THAT BEST EFFECT IT. 195

up the water is always wet, and gives out its moisture to the air. If
previously dipped into a solution of potash, which is very absorbent
of water, it continues more perfectly wet. If it be unsightly, the sus-
pended cloth may be concealed from view by any graceful screen, as
by a tower-shaped cover of porcelain, open above and below to admit
the passage of air. "Where hot-air is used, it may even become neces-
sary to mingle with it the vapor of boiling water.

348. Best method of Warming and Ventilation. — If we would have the
pleasantest mode of warming and ventilating a dwell ing-house, with-
out regard to trouble or expense, we should certainly combine the
open fireplace with air-heating apparatus, which should never exceed
in temperature 212°. The first is desirable for its pleasant light and
radiant heat, while the second gives to the entries and chambers a
mild atmosphere, which prevents cold di'aughts from open doors, and
at the same time, through an opening in each apartment, moderately
warms it, and likewise supplies air for the ventilation going on by the
fireplace. The fireplace also has its influence upon the introduction
of the warmed air. The heat of the chimney establishes a current
which draws from the air-heating apparatus a large supply of air at a
lower temperature than would otherwise enter the apartment. We
know of no single apparatus which warms and ventilates a dwelling-
house in so healthy and comfortable a manner as is accomplished by
this combination. — Wtman. Yet it can only be had by very few ; for
the mass of the people it is entirely out of the question from expen-
siveness.

349. Supply of Air by loose Joinings, CrcTices, &c. — Hot-air con-
trivances of any kind, although coming more into use, especially in
cities, are by no means general. Grates and stoves are the nearly
universal sources of heat, and the latter of these cannot be said to
ventilate at all. Fo provision is made for the entrance and exit of
air. The use of doors to rooms is for the admission of their occu-
pants, windows are for the entrance of light, and it would certainly
seem, both from its importance and peculiar properties, that air also
is entitled to an entrance of its own. Yet in most cases we treat the
air as if it had no business in our dwellings. It has to avail itself of
the mechanics' botch-work or the chance shrinkages of time, and
creep through any crevices and wind-chinks that there may happen
to be, or dodge in and out at the casual opening of windows and
doors. These cracks and loose joinings afford a kind of imperfect
accidental ventilation, which, by effecting the purpose in a partial

196 AKEANGEMENTS FOE VENTILATION".

degree, has prevented mankind from discovering the vrant of any
thing better.

350. Fonr points to be secured in Ventilation. — Tliat ventilation may
be complete, and do for us its best service, four things must be at-
tended to.

First. Pure air must be introduced.

Second. The foul air must be removed.

Third. The supply must be sufficiently copious.

Fourth. There must be no offensive currents.

Now as things usually are, none of these points are certainly se-
cured. There is no constant and regulated supply of air, this being
left entirely to chance. There is no provision for the exit of the
vitiated gases. All the air that is drawn off from the apartment is
taken from its lower and purer portion by the draughts of the stove
and fireplace, while that which should escape stagnates above. The
quantity furnished is therefore variable and usually stinted, while in-
jurious draughts are notoriously common. Independent and effective
methods of changing the air, by which these enumerated benefits may
be gained, are on every account desirable.

851. Modes of iBtrodncing pure Air from without. — In summer the
free opening of doors and windows ensures a supply of air. It is a
good plan to have light door-frames fitted to the outer entrances, and
covered with wirecloth or some loose fabric, as millinet, through
which the air will pass readily, but in a diffused manner. In winter
the air should always, if possible, be warmed before being thrown
into the apartment. For introducing more fresh air than accidental
fissures will admit, the readiest way is to lower the top window sash,
although the stream of cold air which presses in and is both unpleas-
ant and unsafe, falls to the floor and glides to the stove or fireplace
without being suflficiently commingled with the general atmosphere to
serve the purpose of ventilation. It becomes a mere feeder of the fire.
To disperse cold currents of air from above, a plate of zinc perforated
with numerous holes is made to replace the pane of glass furthest from
the fireplace and in the upper row of the window. Louvres made
either of tin, zinc or glass, with horizontal openings and slats like
Venetian blinds, are also substituted for window panes. A small tin
wheel or whirligig, which revolves and scatters the inflowing current,
is sometimes mounted in the window ; it is often noisy and rattling.
In arranging openings for the entrance of air, several circumstances
are to be borne in mind. The air should always be fresh from with-
out and not, as is too often done where hot-air furnaces are used,

INTEODUCnON OF AIR INTO DWELLINGS.

197

taken from cellars or basements, or what is still worse, used over and
over again. If there be local sources of impurity in the Adcinity,
apertures should not be placed favorably to its admission. "Where
dust is an annoyance, or from any cause there is contamination of air
near the ground, the supply may be brought from the top of the house.
Openings are made under the caves, or in some eligible place near the
summit, leading to channels left in the walls, called fresh-air venti-
ducts^ which pass down and open into the room in any convenient
manner. The prevailing direction of the wind should also be noticed,
as it is desirable to command its aid as far as possible ia forcing air
into the building. Emeeson's injector (Fig. 83) causes a downward
current from whatever quarter the wind may
blow upon it. All outer apertures should be
guarded with valves. Air entering them and
led along proper passages, either in tin tubes
or air-tight wooden boxes, is admitted into
the room at various points. There may be
an air passage made along behind the base or
mop-board, communicating with the room by
innumerable minute openings, through which
the air passes. Or the inflowing currents
may be received through registers or made to
rise through small apertures in the floor.

352. The downward Current.— Air once breathed must not be again
brought within the sphere of respiration, but should it be removed
downward or upward ? The air thrown from the lungs escapes hori-
zontally from the mouth and downward from the nostrils ; it may
then be swept without difficulty by the ventilating current in either
direction. In cases where hot air is thrown into the room, it first rises
to the ceiling, and then, as it is gradually cooled, falls, and is mainly
drawn off by the fireplace below the plane of respiration. This is in
effect a downward current, but it is hardly strong enough to carry the
breath down with it. It ascends, is diluted by the upper air, and fall-
ing again is liable to be reinhaled. A descending current of air arti-
ficially cooled has been employed for ventilation ; in fact, rooms can
be as effectually ventilated in summer by the aid of coolers placed
above them, as they are in winter by the heater lelow them. Lyman's
ventilator (Fig. 84), consists of a reservoir of ice — A^ the bottom of
which is an open grate ; ^ is a gutter to catch the water from
the melting ice ; {7 is a pipe or flue, through which a stream of
cold condensed air falls constantly, as shown by the course of

Emerson's Injector.

198

ABEAITGEMEWTS FOE VENTILATION.

Fig. 84.
J)

^

the arrows; I), a wire gauze box filled with char

coal, which prevents the waste of ice by radiation,

and disinfects and purifies the descending air. The

force of the current depends on the length of the cold

air flue and its temperature, compared with the outer

air. In hot weather the breeze continues quite brisk.

This arrangement, on a small scale, has been mounted

on secretaries, to secure a cool and refreshing air whUe

writing ; over beds, to cool the air while sleeping ;

and over cradles, to furnish pure air for sick children

(341).

353. The ascending Cnrrent most IVatnrali — We have

T , 1^ • noticed that by a beautiful provision of nature, venti-
liyman s cold air ■' ^ '

flue. lation of the ferson is constantly taking place. The

exquisite mechanism of the human system would have been created to
little purpose if it had been left to smother in its own poison. A gentle
and insensible current constantly rises from the body, which carries
all that might be injurious into the higher spaces. Vitiated air would
thus constantly escape from us if it could. But in our houses we de-
feat the benign intentions of nature by enclosing the spaces above us,
so that the detrimental gases accumulate in the upper half of the
room, surrounding the head and corrupting the respiratory fountain.
It is thus evident that if we desire to aid nature in her plans, we must
remove or puncture the air-tight covers of our apartments, so that the
ascent and complete escape of foul air shall not be obstructed.

354. Ventiducts and Ejectors. — Openings for the escape of these bad
gases above are indispensable. Each room fifteen feet square, for the
accommodation of six or eight individuals, should have a flue for the
escape of foul air, either in the chimney or elsewhere, of at least 100
inches area. A bedroom should have an outlet of nearly the same
dimensions. But in practice a serious difficulty is encountered here.
If we make an opening out from the top of the room, either by low-
ering the top sash of a window or by carrying up a duct through the
roof, instead of the foul air escaping through them, a flood of cold air
rushes in from without. Tubes or ventiducts, connecting the room
with the top of the house, may be made to act exhaustively, and drain
the apartment of its polluted air, wTien the wind blows, by surmount-
ing it with Emerson's Ejector (Fig. 85), and as the air is almost con-
stantly in more or less rapid motion, this arrangement becomes very
serviceable.

355. Opening into the Chimney— Arnott's Valve. — But the force of

AENOTT'S SKLF-ACTINa VALVE.

199

Fia.

draught in the chunney is after all to be the main reliance in convey-
ing away foul air. Its necessary action is that of a drawing or suck-
ing pump, which exhausts the room of large quantities of air. As the
velocity of smoke in a chimney with a good fire is estimated to be
from 3 to 4 feet per second, its exhaustive power is amply suflBcient
to make it serve the secondary purpose of a ventilating flue. Hence,
if we make a hole into the chimney, by knock-
ing out two or three bricks near the ceiling, the
foul gases will rush in, and mingling with the
ascending current will escape. Yet these ven-
tilating chimney openings are liable to the se-
rious and even fatal objection, that when from
any cause the current in the chimney is inter-
rupted, smoke is driven into the room. An
ordinary register, requiring personal attendance
to open and close it, would be of no service. To Emerson's Ejector,
remedy this inconvenience. Dr. Aenott has contrived a self-acting sus-
pension valve. It is so placed in the aperture, and so mounted, that a cur-
rent of air passing into the chimney opens it, while a current in the con-
trary direction closes it. It is so delicately suspended that the slight-
est breath of air presses it back, while
any regurgitation of the chimney current
shuts it, and thus prevents the backward
flow of smoke into the room. It is shown
in Fig. 86. Owing to the unsteadiness of
the currents, the valve is constantly vibrat-
ing or trembling, and would be noisy but j
that it is made to strike against soft
leather. A modification of this valve Arnott's Vaive.

consists of a square piece of wire gauze set in the opening, with a cur-
tain of oiled silk susj-ended behind it. The current into the chimney
pushes back the pendant flap, while a reversed current drives it against
the gauze, and thus closes the aperture against the admission of fire-
fumes and smoke. These are easily placed in fire-boards used to close
the fronts of chimneys.

356. Importance of Aruott's Valve. — The value of this valve to the
public can hardly be exaggerated. Mr. Teedgold expressed what
many have felt, when he said that all the plans he had seen or read ol
for drawing oS the air from the top of a room are objectionable, either
from being wholly inefficient or from causing the chimney to smoke.
This valve first meets the difficulty. It is cheap, easily inserted, may

Fia,

200 AEBANGEMENTS FOE VENTILATION".

be managed with trifling care, and drains the room eflfectively of its
gaseous pollutions. In the thousands of stifling, stove-heated rooms,
where palor of countenance, headache, and nervousness, bear painful
witness to the perverted and poisoned state of the air, this simple me-
chanical contrivance might bring happy relief. It is much used in
England, but has not been made sufiiciently known in this country.
We have inquired for it in vain at many establishments. It is manu-
factured by S. B. James & Co., 77 "White street — ^price, $2 50 to $5,
according to size. If the orifice in the chimney be deemed unsightly,
it may be screened from view by placing a picture before it.

357. CMmney Currents in Sammer. — The air in the chimney is usually
somewhat warmer than the external air, even when there is no fire,
and this will occasion a slight draught, so that if there be an aperture
in the upper part of the room into the flue, and the fireplace be
closed, the vitiated air above will be removed. This exhaustive ac-
tion of the chimney without fire, is aided by winds blowing across its
top, which exert a slight suction influence, or tendency to form a
vacuum within it. This effect of the wind will be much increased if
the chimney be mounted with an ejector (354). A slight fire in a fire-
place, even when not wanted for warmth, is often desirable for ven-
tilation. Lamps have been sometimes introduced into flues for the
purpose of exciting currents.

358. An additional Ventilating Fine. — If an extra flue be constructed
adjoining the chimney, warmed by it and opening into the top of the
room, there wiU be a draught through it, and it may be devoted ex-
clusively to ventilation. It would seem that such a secondary flue
would not be liable to refluent smoke, and might have connected
tubes extending to remote rooms, thus effectually ventilating the
whole building. But practically such shafts do not well succeed.
Double outlets in the same apartment rarely work satisfactorily. The
chimney is liable to convert the extra flue into a feeder of the fire,
and thus, if it be of the same height as the chimney, to suck back the
smoke into the room. " Such cases have occurred, and the ventilating
flue has been closed in consequence. This evil can be remedied by
providing a free supply of air for both air and smoke flues. But the
air which enters must be warmed, or it wiU not be tolerated, and if it
is too much warmed, as compared with the air of the room, it wiU
rise immediately to the ceiling and escape through the ventilator, and,
not mingling with the air of the room, it will greatly diminish or en-
tirely prevent any change of air where most wanted."

359. Ventilation of Bedrooms. — The bedroom, the place where wo

SPECIAL DEMANDS OF THE BEDKOOM. 201

spend nearly lialf of our lives, in its general condition and manage-
ment is the opprobrium of civilization. No place in the house should
be more copiously supplied with air to guard us against the injurious
agencies to vs^hich we are nightly exposed. The materials of which
bedding is composed have a strong tendency to attract moisture from
the air and become damp. Not only are the textile fibres highly hy-
groscopic, or absorbent of atmospheric moisture, but the coldness of
rooms in which beds are usually placed, favors the deposit of moisture
when the air is charged with it. They are also saturated with bodily
perspiration. Beds should, therefore, be often and thoroughly aired.
Their injurious effects when damp are much more dangerous than
those of wet clothes. As the body is at rest while we sleep, there is
no exercise to warm the surface and throw off the Ul effect, as can be
done with damp clothes. Moreover, as the vital activity is depressed
during the state of slumber, the system is more open to the malign in-
fluence of cold or other causes. Many and fatal diseases, inflamma-
tions, rheumatisms, catarrhs, asthmas, paralysis and consumption, are
induced by a want of precaution in this particular. Yet with all these
demands for capacious drying air-space, bedrooms are apt to be scan-
dalously small and low, damp and unwholesome. They do not usually
contain fireplaces to drain off the bad air, and the lack of all ventila-
tion is made worse by the popular dread of draughts, which prevents
the opening of windows. There is urgent necessity for the adoption
of some means of relieving them. Opening the window
above and below is very serviceable; lowering the upper
sash, with an opening over the door, and currents in halls>
also gives relief. But if the bedroom have no fireplace, it
should be connected by tubes with the chimney flue, the
aperture being guarded by an Arnott's valve.

360. Ventilating Gas-bnincrs. — As we before remarked, the
common mismanagement of gas is a forcible illustration of
the effect of ignorance or thoughtlessness, in often turning
the best things to the worst account. Gaslight is cheap,
brilliant and convenient, the very qualities we want ; and so
we turn it on and enjoy the flood of light. But bad air and
headache supervene, and then gas-lighting is condemned,
though the real fault is lack of ventilation. The use of gas-
light greatly heightens the necessity for effective change of air ; it
generates poison exactly in proportion to its brilliancy. Dr. Faea-
DAT adopted the following successful plan to ventUate gas-burners

202 AURANGEMENTS FOE VENTILATION.

He placed a metallic tube about an incb in diameter over tbe lamp-
glass, dipping down into it (Fig. 87) one or two inches, and connect-
ing by its other extremity with a flue. But this was thought to be an
ungraceful appendage to the chandelier, and has not come into use.
He devised another, by which the tube carrying off the products of
combustion, returned parallel with the supply pipe, but we have not
seen it. There is report also of a stiU more elegant and successful
English contrivance, but it cannot yet be found in this country.

361. Ventilation of Cellars. — It was seen that cellars are fountains
of offensive air, which ascends through crevices in the floor, doors,
windows, and stairways, often infecting the upper apartments with
the noxious cellar atmosphere. If cellars are to be tolerated under
our houses, they should be thoroughly ventilated. Perhaps the best
plan is to extend a flue from the chimney down into the cellar, by
which the fire-draught above shall constantly drain it. A tube or
passage from the cellar to the top of the building, mounted with an
ejecting cowl, answers a good purpose. Some go for abolishing cellars
altogether.*

362. Ventilation should be provided for in Bnilding. — There can be
little question that the whole policy of warming and ventilating
dwellings is yet in an unsettled and transition state, although this
affords no apology for neglecting the subject. Much is known, and a
great deal may be done about it to promote health and preserve life.

* " While I woDld condemn cellars and basements entirely, the common plan of build-
ing, in their absence, must bo condemned also. The house being built above the surface
of the earth, a space is left between the lower floor and the ground, which is even closer
and darker than a cellar, and which becomes, on a smaller scale, the source of noxious
emanations. Under-floor space should be abolished as well as cellars and basements.
The plan that I have adopted with the most satisfactory success, to avoid all these evils,
is the following : Let the house be built entirely above the ground ; let the lower floor
be built upon the surface of the earth, at least as high as the surrounding soil. If filled
up with any clean material a few inches above the surrounding earth, it would be better.
A proper foundation being prepared, make your first floor by a pavement of brick, laid
in hydraulic cement, upon the surface of the ground. Let the same be extended into
your walls, so as to cut off the walls of your house with water-proof cement, from all
communicatiou with the moisture of the surrounding earth. Upon this foundation build
according to your fancy. Your lower floor will be perfectly dry — impenetrable to moist-
ure and to vermin ; not a single animal can get a lodgment in your lower story. By
adopting this plan, your house will be dry and cleanly ; the atmosphere of your ground-
floor will be fresh and pure ; you will be entirely relieved from that steady drain upon
life, which is produced by basements and cellars, — and if you appropriate the ground-
floor to purposes of storerooms, kitchen, &c., you will find that the dry apartments thus
constructed are infinitely superior to tlie old basements and cellars. And if you placi
your sitting and sleeping rooms on the second and third floors, you will be as thoroughly
exempt from local miasma as Architecture can make you." — Dr. Buchanan.

WHY THEY ARE NOT UNIVEKSAL. 203

Provision should be made for ventilation in the first construction of
dwellings, as it may then be efiectually and cheaply accomplished.
The introduction of adequate arrangements, after the building is
finished, is costly and difiicult. The necessity is absolute for including
ventilating provisions in houses as well as those for heat. Architects
and Builders should make them a primary and essential element of
their stractural arrangements, and design in accordance with the prin-
ciples of ventilation as an established art. It is to be regretted that
too many in those professions to which a careless public commits its
interests in this particular, are prof&undly unconscious of the just
claims of the subject, and totally unqualified to deal with it properly.
This is hardly a matter of surprise when we recollect how recent it is
that science has thrown its light upon the physiological relations of
air. It is almost within the memory of men still living that oxygen
gas was first discovered^ and it is withia twenty years that Liebeo an-
nounced the last constant ingredient of the atmosphere (280). Archi-
tecture on the contrary rose to the dignity of a regular art thousands
of years ago, when men had little more intelligent understanding of
the real import of the breathing process than the inferior animals.
"We have therefore little cause for amazement when a book appears
upon the subject of Architecture, of more than a thousand pages, and
dispatches the whole matter of ventilation in ten lines — and that, too,
with a sneer. Our buildings are hence commonly erected with less
reference to healthful comfort than outside show, and ventilation is
too much looked upon as a mere matter of tin tubes and knocking
out bricks, that may be attended to at any time when it may be
thought necessary.

363. Ventilatiott involves necessary loss of Heat. — The real practical
difliculty in ventilation is its cost. Although the atmosphere is every
one's property, and is the cheapest of aU things, yet a supply of pure
air in dwellings is by no means free of expense. To ensure ventilation
we must have motion of air, and to produce motion demands force,
which is a marketable commodity. Whatever will produce available
force has value in it. "Whether it be fans and pumps driven by steam-
engines, or upward currents set in motion by naked fire, in both cases
there is expenditure of fuel. It is true we may use the fire that must
be kindled to produce warmth, and thus secure the additional result
of ventilation, apparently without additional cost. But in most cases
foul air is also warm air, and in escaping conveys away its heat, which
is thus lost. Contrivances have been proposed, by which the outflow-
ing warm air may be made to impart its heat to the incoming cold

204 AEEAiiTGEMENTS FOR VENTILATION.

air, but tliey are not yet reduced to practice. Until that is done, heat
must continue to be lost by ventilation, just in proportion to its extent.
Hence, as was before remarked, ventilation may be classed with food
and apparel, and it becomes a question of how much can be afforded.
But there is this important difference, that whUe economy in the
latter — a plain table and coarse clothing — are at least equally favorable
to health with more expensive styles of eating and dressing, economy
of ventilation on the contrary, that is, any cheapening or deterioration
of the vital medium of breathing, is injurious to health. One of the
worst evils of scarce and expensive fuel is, that the poorer classes feel
compelled to keep their rooms as tight as possible to prevent the
escape of warm air and the consequent waste of heat.

PAET lOIJRTH.

ALIMENT.

I.— SOUECE OF ALIMENTS— OKDER OF THE SUBJECT.

364. Yiew of the origin of Foods. — The ground thus far traversfid has
farnislied abundant illustration of the close alliance between man and
the material universe, and of his subjection to physical influences ; but
we are now to see that he is composed of exactly the same materials
as the solid globe upon which he dwells. Eocks, corroded by the
agencies of time and crumbled into soils, join with the ethereal ele-
ments of the atmosphere, to furnish the substances of which the
living body is composed. But rocks, soils, and air are not food. They
are unorganized, lifeless matter ; and can neither nourish the body,
nor have they the power of uniting themselves together into nutritive
compounds. The forces which play upon terrestrial atoms, throwing
them into movement, arranging them into vital groups, and endowing
them with the capability of becoming parts of animal systems, are
shot down from the heavens. The impulses of organization and
growth are not inherent powers of our earth, residing in air and soil.
In the plan of the universe the Sun, a star among the stellar systems,
is the architect of living forms, the builder of terrestrial organization,
the grand fountain of vitality. His rays are streams of force, which,
after travelling a hundi'ed millions of miles through the amplitudes
of space, take effect upon the chemical atoms of the earth's surface —
its gases, waters, miaerals, and combine them into nutritive, life-sus-
taining compounds. The vegetable world is the laboratory wher«
this subtle chemistry is carried forward, and matter takes on the
properties of organization. Such is the ultimate source of all our
food. The solid materials which we perpetually incorporate into the
bodily fabric, originated in plants, under the direct agency of the sun-

206 SOUECE OF ALIMENTS — OEDEE OP THE SUBJECT.

beam. The vegetable leaf is the crucible of vitality, the consecrated
mechanism appointed to receive the life-forces which God is per-
petually pouring through his universe. In partaking of the bounties
of the table, are we not, then, consummating a purpose to which
planetary systems are subservient ? We repair the failing textures of
animal life, but it is with tissues woven in a loom of invisible airs by
the flying shuttles of light. That a single grain of wheat may be
ripened — that its constituent starch, gluten and sugar may be per-
fected, this ponderous orb must shoot along the ecliptic at the rate
of 68,000 miles per hour, from Taurus to Libra, whirling perpetually
upon its axis as it flies, that all parts may receive alike the vitalizing
radiations. When therefore we contemplate the grandeur of the
operations by which the Creator accomplishes the problem of life in
this state of being, the subject of foods rises to a transcendent interest.
The consideration of these questions, however, the forces that control
vegetable groAvth and give rise to organic compounds, pertains to
chemistry and vegetable physiology ; neither our plan nor our space
will allow us to consider them here. We direct attention flrst to the
general properties of foods, as we find them already produced and
presented for preparation and use.

365. How Foods may te considered. — A systematic presentation of
the subject of aliments, that shall be quite free from scientific objec-
tion, appears in the present state of knowledge to be impossible. We
shall adopt an arrangement which aims only to be simple and popular.
All articles of diet are composed of certain substances, which are
known a.?, alimentary principles^ — simple aliments, ajid proximate prin-
ciples. These are not the ultimate elements, carbon, oxygen, hydro-
den, nitrogen, sulphur, &c., but are formed by combinations of tliese.
They differ from each other in properties, exist in very different
proportions in various kinds of food, and are capable of being sepa-
rated from each other and examined independently. These require to
be first considered. ISText in order we shall speak of the products
which these simple principles form when united together. Thus
starch, sugar, gluten, &c., are simple aliments; while grain, roots,
meats, &c., are made up of them, and are therefore called compound
aliments. We shall give the composition of these, and as much of
their history and preparation as may be necessary to understand their
properties, and then trace the changes which they undergo in culinary
management. The principles involved in various modes of preserving
alimentary substances will next be described, and the subject closed
by an examination of their physiological effects and nutritive powers.

WATBK — ITS SOLVENT PROPERTIES. 207

366. Division of Alimentary Principles. — The simple alimentary prin-
ciples are separated into two important divisions, based on their com-
position ; first, the non-nitrogenous aliments, or those containing no
nitrogen in their composition ; and second, the nitrogenous aliments,
or those which do contain this element. The first group consists of
starch, sugar, gum, oO, and vegetable acids ; whUe the second com-
prise albumen, fibrin, gluten, casein. Of these two classes the first
is simpler in composition and much more abundant in nature than the
other class ; we shall hence consider them first. There is, however,
another alimentary substance of peculiar properties, and of the first
importance — water, which cannot be ranked strictly with either group.
It is not a product of vegetable growth, but is rather a kind of univer-
sal medium or instrument of all sorts of organic changes. As the
most abundant and indispensable of all the principles of diet, it claims
our first attention.

II.— GENEEAL PKOPERTIES OP ALIMENTARY SUBSTANCES.

1. PEIIfOIPLES OONTAINIKra NO NlTEOaEN.
A.— "Water.

867. Solvent Powers of Water. — One of the most important proper-
ties of water is its wonderful power of dissolving many solids ; that
is, when placed within it they lose their solid form, disappear, and be-
come diffused through the liquid. Such a combination is called solu-
tion. It is the result of a mutual attraction between the liquid and
the solid, and it becomes weaker between the two substances as this
attraction is satisfied. The action of water upon soluble substances is
very powerful at first, but as solution proceeds the action gradually de-
creases, until the water will dissolve no more; it is then said to be
saturated. Water saturated with one substance, may lose a portion of
its power to dissolve others, or its solvent energy may sometimes be
increased ; this depends upon the compound which it contains in solu-
tion. "With some substances it combines in all proportions, and never
gets saturated. Water does not dissolve all substances ; if a fragment
of glass and a piece of salt be put into it, the glass will be unchanged,
while the salt will vanish and become liquid. Nor does it dissolve
alike all that it acts upon ; a pound of cold water will dissolve two
pounds of sugar, while it will take up not over six ounces of common
salt, two and a half of alum, and not more than eight grains of lime.
Heat influences the solvent powers of water, most generally increasing
it ; thus, boiling water will dissolve 17 times as much saltpetre as ice

208 GENERAL PEOPEETIES OE ALIMENTAUT SUBSTANCES.

water. This it seems to do by repelling the particles of the solid body
from eacb other, thus assisting the water to insinuate itself among
them, by which its action is helped. But there are exceptions to the
rule, of which lime is an example ; sixty-six gallons of water at 32°
dissolves one lb. of lime, but it takes 75 gallons at 60°, or 128 at 212°,
to produce the same effect, so that ice-cold water dissolves twice as
much lime as boiling water.

368. How test to hasten Solution. — Solids should be crushed or
pulverized, to expose the largest surface to the action of the solvent
liquid. Substances which in the lump would remain for days undis-
solved, when reduced to powder are liquefied in a short time. When
a solid, as common salt or alum, is placed in a vessel of water to dis-
solve, it rests at the bottom. The water surrounding it becomes sat-
urated, and being heavier, remains also at the bottom, so that the solu-
tion proceeds very slowly. By stirring, the action is hastened, but this
takes up much time. The best plan is to suspend the salt in a colan-
der, basket, or coarse bag, at the surface of the liquid. As the parti-
cles of water take up the particles of salt, they become heavier and
sink ; other particles take their places, dissolve more of the salt, and
sink in turn, so that the action of a constant current of liquid is kept
up on the suspended crystals, and always at that portion most capable
of dissolving them.

369. Solution of Gases — Soda-water. — Water also dissolves or absorbs
vai'ious gases, some more and some less. It may take 780 times its
bulk of ammonia, an equal bulk of carbonic acid, or Jj its bulk of
oxygen. The quantity is, however, controlled by heat and pressure ;
heat acts to expel the gases, so that as the temperature rises, the water
will hold less and less, while with increased pressure, on the contrary,
it will receive an increased amount. Soda-water is thus by pressure
overcharged with carbonic acid gas, which escapes with violent effer-
vescence when the pressure is withdrawn. The effect is the same,
whether the gas is forced into the water from without, or generated in
a tight bottle or other vessel, as is the case with fermented liquors.
The gas gradually produced is dissolved by the water, which, escaping
when the cork is withdrawn or the vessel unclosed, produces the foam-
ing and briskness of the liquor.

370. DiflTerent varieties of Water. — In nature water comes in contact
with a great number of substances which it dissolves, so that there is
consequently no perfectly pure, natural water. The substances which
it takes up are numerous, and differ under various circumstances and
conditions, and as these foreign substances or impurities which the

THE GASES DISSOLVED IN WATER. 209

■water acquires, communicate their properties to the liquid, it results
that there are many varieties of natural water, as for example, spring-
water, river-water, sea-water, rain-water, &c.

371 . Rain-water and Snow-water. — Rain-water is the least contami-
nated of all natural waters, yet it is by no means perfectly pure. As
it faUs through the air, it absorbs oxygen, nitrogen, carbonic acid
and ammonia, with which it comes in contact, and it also washes out
of the atmosphere whatever impurities it may happen to contain.
Thus, in the vicinity of the ocean, the air contains a trace of common
salt ; in the neighborhood of cities, various saline, organic, and gaseous
impurities, while dust is raised from the ground and scattered through
it by winds, and these are all rinsed out of the air by rains. The
water which falls first after a period of drought, when contaminations
have accumulated in the air for some time, is most impm-e. Rain fall-
ing in the country, away from houses, and at the close of protracted
storms, is the purest water that nature provides. It differs from dis-
tilled water only in being aerated^ that is, charged with the natural
gases of the air. Falling near houses, it collects the smoky exhala-
tions, and flowing over the roofs it carries down the deposited soot,
dust, &c. "Water from melted snow is purer than rain-water, as it de-
scends through the air in a solid form, incapable of absorbing atmos-
pheric gases. When melted, the water which it produces is insipid
from their absence, and should be exposed for a day or two to the at-
mosphere, that it may absorb them.

372. The Gases contained in Water. There is an atmosphere diffused
through all natural waters. It is richer in oxygen than is the upper
atmosphere ; in the latter there is but 23 per cent., while in the air of
water there is 33 per cent. The animals which dwell in water absorb
this oxygen by breathing, just as land animals do from the air, while
water-plants in the same manner live on the carbonic acid it contains.
These absorbed gases also influence its taste, giving it a brisk and
agreeable flavor. If it is boiled they are driven off, and the liquid be-
comes flat and mawkish. The presence of as much oxygen as water
wiU hold, improves it as a beverage, as this gas is necessary to the ac-
tive performance of several of the most important vital functions.
Water that is quite cold contains more oxygen than that which has
been made warm in any way, as by exposure to the sun or the warmth
of a close room, which causes a portion of it to escape.

373. Organic Contaminations of Water. — From the dust and insects
of the air, the wash of the ground and the drainage of residences,
from mud and decayed leaves, the decomposing bodies of dead ani-

210 GENERAL PROPERTIES OP ALIMENTARY SUBSTANCfES.

mals, and a variety of other causes, waters are liable to contain or-
ganic impurities, or those vestiges of liviag structures which are
capable of decomposition and putrefactive change. The effect of this
organic matter may be shown by taking a little of the sediment that
has accumulated at the bottom of a cistern, and placing it in a bottle
of perfectly pure distUled water, when in a short time, if the weather
be warm, it wiU begin to smell offensively. This kind of contamina-
tion may be either suspended mechanically in water as solid particles,
or it may be dissolved in it so that the water shall stUl have an appear-
ance of purity.

374. The lining Inbaltitants of Water. — Under certain favorable con-
ditions of warmth, access of air, light, &c., countless numbers of living
beings, both plants and animals, make their appearance in water.
They are nourished upon the dead organic matter which the water
may happen to contain, and belong either to the animal kingdom as
animalcula or infusoria, or are of a vegetable nature, as fungi.
There are other conditions which influence the Tcind of life which ap-
pears in water. If the liquid be slightly alkaline, animalcula will be
produced, while if it be a little acid, fungi or microscopic plants wUl
appear. This maybe shown by diffusing ahttle white of egg through
water in a wine glass, and keeping it in a warm place. If it be made
in a small degree alkaline, it wiU swarm with animalcula in a few days ;
if, on the contrary, it be slightly acid, vegetable forms will be princi-
pally originated. It is important to notice also that the alkaline solution
wiU run rapidly into putrefaction, and yield a putrescent smell, while
the acid fluid will scarcely alter at all, and emit no unpleasant odor.
It is hence obvious that these two kinds of water have different rela-
tions to human health, the slightly acid being more favorable to it
than alkaline waters. These living inhabitants are never found in
freshly fallen rain-water, caught at a distance from houses, nor in
spring or well-water, but they more or less abound in cistern water,
reservoir water, and marsh, pond, and river waters.

375. Use of living beings in impnre Water. — The presence of living
tribes in impure water, fulfils a wise and beneficent purpose. If the
large amount of organic matter present in many waters could be re-
moved only by the common process of putrefaction, and the forma-
tion of injurious compounds and offensive gases, immense mischief
would be the consequence. To obviate this, nature has ordained that
some of the organic matter of impure water, in place of undergoing
decomposition, shall be imbibed by living beings, and these dying that
others shall take their place and fulfil the same important office. The

MTNEEAL MATTEB DISSOLVED BY WATER. 211

living races thus exert a preservative influence upon water, although
this is more especially true of aquatic vegetation,

376. Water dissolves variable quantities of Mineral Matter. — Rain
which falls upon high ground filters through the porous soil and strata
of the earth until stopped by impenetrable clay or rock; it then passes
along the surface of the bed until it finds an opening or crevice,
through which it is forced up to the surface of the ground, producing
a spring. Water which has thus leached through the mineral mate-
rials of the earth, dissolves such portions of its soluble materials as it
meets with, and carries them down to the lower levels, so that they
ultimately collect in the sea. The amount of mineral matter thus dis-
solved is extremely various. The water of the river Loka, in North-
ern Sweden, which flows over impervious, insoluble granite, contains
only Jg of a grain of mineral matter in a gallon weighing 70,000
grains. Common well-waters, spring- water and river-water, contain
from 5 to 60 grains in a gallon, but generally, in waters of average
purity, which are employed for domestic purposes, there are not pres-
ent more than 20 or 30 grains of mineral matter to the gallon. When
the dissolved substances accumulate untU they can be tasted, a mineral
water results. The celebrated Congress water, at Saratoga, contains
611 grains to the gallon. Ocean water has as much as 2,500 grains of
saline substances, and the water of the Dead Sea the enormous quan-
tity of 20,000 grains in the gallon. Of the two natural waters — those
of the river Loka and the Dead Sea — the latter contains 400,000 times
more saline matter than the former,

377. Rinds of Mineral Matter dissolved by Water. — The mineral sub-
stances dissolved in spring and well waters, are chiefly iron, soda,
magnesia and lime, combined with carbonic and sulphuric acids, and
forming salts^ which are compounds of acids with alkalies or bases ;
sulphates and carbonates, together with chloride of sodium or common
salt. Iron, mixed with carbonic and sulphuric acids, is present in
most waters which percolate through the ground; soda and magnesia
also often exist in these waters, but their most universal and important
ingredient is lime. This exists in almost aU soils in combination with
carbonic acid as carbonate of lime, or powdered limestone, and it is
also very common in the shape of sulphate of lime, or plaster. Most
of these substances are soluble in pure water, but this is not the case
with the widely diffused carbonate of lime. The power of dissolving
this substance depends upon the presence of free carbonic acid con-
tained within in the water. If charged with this gas, water becomes
a solvent of limestone.

212 GENERAL PKOPEKTIES OF ALIMEISTTAEY SUBSTANCES.

378. Hard and Soft Water. — The presence in water of these dis-
solved mineral substances, though in extremely small proportion, pro-
duces important changes in its properties. Compounds of lime and
magnesia give it hardness^ while rain and snow-water, and that from
some springs which are free from these mineral matters, are called
soft. This distinction of waters into hard and soft is usually connected
with its cleansing qualities and its behavior towards soap, which we
shah consider in another place. It is also important dietetically (533),

379. Water in contact with Lead. — There has been much contradic-
tion among scientific men in regard to the effects of storing water in
leaden vessels, or transmitting it through leaden pipes. It was known
that some kinds of water would corrode or dissolve the lead and be-
come poisonous ; but what waters ? Dr. Oheistison said those which
were soft^ while hard waters would form a crust in the interior surface
of the lead, and thus protect it from corrosion. But later experi-
menters declare hard waters to be even worse than soft in their action
upon lead. It may be remarked that water can act upon lead, cor-
roding it without becoming itself actively poisonous, if the compound
formed be insoUible ; it is only when the lead is dissolved that the
water containing it becomes dangerous. When ordinary water is
placed in contact with lead, the free oxygen it contains combines with
the metal, forming oxide of lead ; water immediately unites with that
producing hydrated oxide of lead, which is nearly insoluble in water.
There is also more or less carbonic acid existing in all natural waters ;
this combines with the oxide of lead, forming carbonate of lead,
which is also highly insoluble. But if there be in the water mucJi
carbonic acid, a hicarbonate of lead is formed, which is very soluble,
and therefore remains dissolved in the water. Hence waters which
abound in free carbonic acid, as aiso those which contain bi carbonates
of lime, magnesia, and potash, are most liable to become poisoned by
lead. Water containing common salt acts upon this metal, forming a
soluble, poisonous chloride of lead. On the other hand, water con-
taining sulphates and phosphates is but little injured, these salts exert-
ing a protective influence on the lead. "From a review therefore of
the whole of the arguments and experiments now advanced, respect-
ing the action of different waters on lead, we deduce the following
general conclusions : That while very soft water cannot be stored for
a lengthened period, with impunity, in leaden vessels, the danger of
the storage of hard water under the same circumstances is in most
cases much greater. This danger, however,-is to be estimated neither
by the qualities of hardness or softness, but altogether depends upon

SOFT WATEE — STAECH.

213

the chemical constitution of each different kind of water ; thus, if this
be ever so soft, and contain free carbonic acid, its action on lead will
be great ; whereas if it be hard from the presence of sulphates and
phosphates principally, and contain but few bicarbonates, &c., little
or no solution of the lead will result." — Dr. Hassall. Water is
powerfully corrosive of iron when conveyed through this metal in
pipes, but the compounds formed are not injurious. Galvanized iron
pipes, which have received a coating of tin (610), are coming much
into use instead of lead for the conveyance of water.

380. Supply of Soft Water, — Wells and springs are often inacessible,
or the water furnished is bad. In such cases the heavens furnish an
unfailing resource, which, with well-constructed cisterns, filters, and
ice, leave little to be desired in the way of aqueous luxury. Taking
the annual rainfall at 36 inches, we have 3 cubic feet of water falling
upon a square foot of surface in a year. A cubic foot contains 61-
gallons, BO that we get 18J gallons upon each surface foot annually.
A house 25 by 40 has a thousand feet of surface, and collects nearly
19,000 gallons of water annually, which if stored in cisterns of suf-
ficient capacity, will furnish more than 50 gallons per day throughout
the year.

B.— Tbe Starcbes.

381. Whence oI)tained, and how separated. — Starch, when pure, is
seen to be a fine snow-white glistening powder. It is found univer-
sally distributed in the vege-
table kingdom in much
greater quantity than any
other substance formed by
plants for food. It exists
in grain, peas and beans ; in
all kinds of seeds ; in roots,
as potatoes and carrots, and
in the stem, pith, bark, and
fruit of many plants. When
wheat flour is mixed up into
a dough, and washed (Fig.
88), on a Unen cloth with
clean water, a milky liquid * O ii k^ |||

passes through containing ^ . „ , „ , ,

, , , , ^ Separating Starch from flour by Tvashmg.

wheat starch, which grad-
ually settles to the bottom of the vessel. If raw potatoes are

214 GENERAL PK0PERTIE3 OV ALIMENTAKY SUBSTANCES.

grated, and the pulp treated in a similar manner, potato starcli is
separated.

882. Proportions in Tarions substances. — The variable proportion of
starch in different articles of food is as follows, in decreasing order :

starcli per eent*

Eice flour 84 to 85

Indian corn 77 to 80

Oatmeal 70 to 80

Wheat flour 39 to 77

Barleyflonr 67 to 70

Kye flour 50 to 61

Buckwheat 52

Pea and bean meal 42 to 43

Potatoes, containing 73 to 78 water, 13 to 15

383. Starch Grains — their size. — Starch consists of exceedingly small
rounded grains. They cannot be distinctly seen with the naked
eye, and are so extremely minute that the finest wheat flour, which
has been ground to an impalpable dust, contains its starch grains
mostly unbroken and perfect. The granules of potato starch aro
largest, while those of wheat and rice are much smaller (Fig. 89), end
those of turnips and parsnips still smaller, varying all the way from

Fig. 89.

starch-grains of potatoes. Starch-grains of plantain. Starch-grains of rico.

the l-300th to l-10,000th of an inch in diameter. Assuming tho
grains of wheat starch to be 1-lOOOth of an inch in diameter, a thou-
sand million of them would be contained in a cubic inch of space.

384. Their Appearance and Structure. — Viewed under a high mag-
nifier, starch grains from various sources exhibit marked peculiarities
in form as well as in size. Several kinds have a ringed or grooved
aspect, as seen in Fig. 89, which appearance is explained by the fact
that they consist of concentric layers or membranes, like the coats

DIPFEKENT VAEIEriES OP STARCH. 215

cf an onion. The grains of potato starch are ovoid or egg-shaped.
Many of the grains of pea starch are hollowed or concave in the direc-
tion of their length, while wheat starch consists of dull, flattened,
lens-shaped grains, sticking together when not perfectly dry, on
which account the wheat starch of commerce always comes in loose
lumps. Thus each variety of starch-grain has some peculiar appear-
ance of its own, hy which the practical microscopist is enabled to
identify it. He can hence detect adulterations of the more valuable
with the cheaper varieties, as wheaten flour or maranta arrow-root
with potato starch.

385. Sago Starch is procured from the pith of several varieties of
the pahn tree. It comes in various forms. Sago meal or flour is a
whitish powder. Pearl-sago, the kind in general use for domestic
purposes, consists of small pinkish or yellowish grains, about the size
of a pin's head. Common or brown sago consists of much larger
grains, which are of a brownish white color, each grain being brownish
on one side and whitish on the other. As aU. the kinds of sago contain
coloring matters, they are considered inferior to those varieties of
starch, as arrow-root and tapioca, which are perfectly white.

386. Tapioca is a variety of starch which comes from South Ameri-
ca, and is obtained from the root of a plant containing a poisonous
milky juice. When it appears as a white powder, it is called Brazil-
ian arrow-root. The term tapioca is commonly applied to that form
of it which appears in small irregular lumps, caused by its having
been dried on hot plates, and then broken up into fragments.

387. Arrow-roct. — A root growing in the West Indies (the Maranta
arundinacea), contained a juice supposed to be capable of counter-
acting the effects of wounds inflicted by poisonous arrows. This root
yielded a starch which took the name of maranta arrow-root. But
afterward starches from other plants which had a resemblance to
maranta starch, took also the name of arrow-roots. Thus there is
Tahiti arrow-root, Manihot arrow-root, from the plant which yields
tapioca, and potato arrow-root, or British arrow-root, as it is some-
times called. Maranta arrow-root, which is a very pure white starchy
powder, is the most prized of all the varieties, but it is often adulter-
ated with other and cheaper kinds.

388. Com Starcb. — This is a preparation of the starch of Indian
corn, which has been separated as perfectly as possible from the other
constituents of the grain. Chemical means are used to effect the
separation. The starch is freed from the glutinous, oily and hgneous
elements of the seed, by the aid of alkaline solutions, and by grinding

216 GEaSTEEAL PKOPEBTIES OF AXrMENTAUT SUBSTANCES.

and bolting the corn in a wet condition. The grain is reported to
yield from 30 to 35 per cent, of pure starch, which bears a general
price, about one-third greater than wheaten flour. The culinary
changes of starch and its effects upon the system will be considered
under these topics (516).

389. CIiemLcal Composition. — Starch consists of three elements, —
carbon or charcoal, oxygen, and hydrogen. The two latter are found
in starch in exactly the same proportions that they exist in water, so
that the composition of this substance may be given as simply char-
coal and water. A compound atom of starch consists of twelve atoms
of carbon, combined with ten of oxygen and ten of hydrogen, or
twelve atoms of carbon to ten of water.

C— Tlie Sug'ars.

390. Proportion in varions Snlistances. — This is the sweet principle
of food, and is produced by both plants and animals. It exists in
milk, and it has lately been shown that it is generated in the animal
liver. But our supplies come entirely from the vegetable world,
where it is produced in great abundance, both in the sap and juices
of plants, and stored up in their fruits and seeds. The following is
the proportion of sugar obtainable from various sources :

Per cent, of Sugar.

Juice of Sugar cane 12 to 18

Beet root 5 to 9

Wheat flour 4 to 8

Barley meal 5'3

Oat meal 4'8

Cow's milk 8-3

Eye meal 3-2

Peas 2

Indian corn ^ 1"5

Rice -2

There are several varieties of sugar, but we are practically concerned
with but two, cane sugar and grape sugar.

391. Grape Sngar or Fruit Sugar. — The white sweet grains of raisins
or dried grapes take the name of grape sugar. Most other fruits,
however, as apples, pears, plums, figs, cherries, peaches, gooseberries,
currants, &c., grow sweet in ripening, which is owing to the same
kind of sugar which exists in the grape. It may be readily extracted
from fruits, but this is rarely done.

392. Sugar Artificially Produced. — If starch be boiled for some time
in water which has been soured by adding to it one or two per cent.
of sulphuric acid, the solution gradually acquires a sweet taste. If,

PEODUCnON AND COMPOSITION OF HONEY. 217

now, by suitable means, the acid be neutralized and removed, and the
solution boiled down, it yields a rich sirup or a solid sugar. This
comes from the transformation of starch ; the acid taking no direct
part in the change, but only inducing it by its presence. Potatoes
treated in this way, it is said, will produce ten per cent, of their weight
of sugar. But what is still more singular, the fibre of wood may also
be converted into sugar. Paper, raw cotton, flax, linen and cotton
rags, and even sawdust, may be changed to sugar by the same agency.
The boiling with acid must, however, in this case, be continued longer,
as the woody matter has first to be changed to starch before it be-
comes sugar. This product, known as starch sugar^ has the same
nature and properties as grape sugar.

393. Hoaey. — This is obtained by bees from the juices found in the
nectaries, or honey-cups of flowers. They collect it in the crop, or
honey-bag, which is an enlargement of the gullet, and when filled is
about the size of a pea. Laden with its sweet treasure, the insect
retm-ns to the hive and disgorges it into a previously prepared cell of
the honeycomb, which it then caps over by a thin covering of was.
To procure it in the purest liquid form, and of the best flavor, the
plan is to unseal the cells by removing a slice from the surface of the
comb, after which it is laid upon a cullender to drain. It is some-
times warmed, to facilitate the flowing, but this is said to injure the
delicacy of its flavor. It is more commonly pressed. This increases
the quantity, and saves time ; but it is then contaminated by traces
of wax, and fouled by the juices of crushed bee-maggots, which may
happen to be in the comb.

394. Properties and Composition. — Honey, in different localities, differ-
ent seasons, and from different flowers, varies very much in color, flavor,
and fragrance. That from clover, or from highly fragrant flowers, is far
superior to that from buckwheat ; spring-made honey is better than
that produced in autumn. Virgin honey, or that made from bees
that never swarmed, is finer than that yielded by older swarms ; and
while some regions are renowned for the exquisite and imrivalled
fiavor of their honeys, that made in some other places is actually
poisonous. "We can hardly suppose honey to be a simple vegetable
liquid. It probably undergoes some change in the body of the insect
by the action of the juices of the mouth and crop, as when bees are
fed upon common sugar alone they produce honey. Honey is an in-
tensely sweet sirup, varying in color from nearly white to a yellowish
brown. It consists of two sorts of sugar. One of these remains always
in a liquid or sirupy condition, and the other is liable to crystallize or

218 GENEEAL PEOPEETIES OF ALIMENTAEY SUBSTANCES. '

change to solid grains {granulate)^ this is grape sugar. The lightest
colored and most valuable honeys contain the most of it, and hence
are most liable to granulate and grow thick. Honey contains an
acid, and aromatic principles, which together with its uncrystallizable
sweet part, are not very well understood.

395. Cane Sugar — ^its Sources, — Our common sugar is obtained, as is
weU known, from the sugar-cane. Eleven-twelfths of aU the sugar
of commerce has this origin. That which is procured from the as-
cending sap of the maple, the descending sap of the birch, and also
from the walnut and other trees ; from the juice of beets, carrots,
turnips and melons, from green corn-stalks, and the unripe seeds of
grain, is identical in essential properties with that of the sugar-cane,
and they are all distinguished as cane sugar.

396. Cane and Grape Sugars, diflferent conditions of origin. — It is neces-
sary to understand clearly the difference between cane sugar and grape
sugar. "We have seen that the agency of acids is employed to convert
starch into grape sugar, and they have the same effect upon cane
sugar. This change takes place even in the interior of growing
plants. Those plants and fruits which possess sour or acid juices, yield
gi-ape sugar, whUe those which contain little or no acid in their saps,
contain generally cane sugar. Grape sugar may be produced by art,
while cane sugar cannot.

397. Cane and Grape Sugars, clienucal differences. — Sugar, like starch,
consists only of carbon and water ; but these two sugars differ in the
proportion of these elements, WhUe cane sugar contains twelve
atoms of carbon to eleven of water, grape sugar contains twelve atoms
of carbon to fourteen of water. Grape sugar is therefore less rich in
carbon than cane sugar, and cane sugar may be transformed into
grape sugar by the addition of chemically combtaed water. It is an
essential property of sugar, that under the action of ferments, they are
decomposed ; converted into carbonic acid and alcohol. Grape sugar
is most prone to this change ; and cane sugar, before it can undergo
fermentation, must be first changed into grape sugar. Cane sugar
passes into the solid state much more readily than grape sugar, taking
on the form of clear, well defined crystals of a constant figure ; grape
sugar, on the contrary, crystallizes reluctantly and imperfectly, with-
out constancy or form. Crystals of cane sugar are regular six-sided
figures, while those of grape sugar are ill-defined, needle-shaped
tufts.

898. Difference of solubility and sweetening powers. — Pure cane sugar
remains perfectly dry and unchanged in the air, while grape sugar

t PRODUCTION OF COARSE SUGAR. 21^

attracts atmospheric moisture, becoming mealy and damp. Yet cane

sugar dissolves in water mucli more readily than grape sugar. While
a pound of cold "water will dissolve three pounds of the former, it will
take up but two-thirds of a pound of the latter. Cane sugar will,
therefore, make a much thicker and stronger sirup than grape sugar,
dissolving also more freely in the juices of the mouth, (a property
upon which taste depends). Cane sugar possesses a higher sweetening
power than the other variety. Powdered grape sugar has a floury
taste when placed upon the tongue, and very gradually becomes
sweet and gummy or mucilaginous as it dissolves. Two parts by
weight of cane sugar are considered to go as far in sweetening as
five of grape sugar. To make them economically equal, therefore,
five pounds of grape sugar should cost only as much as two of cane
sugar ; and hence the mingling of grape with cane sugar is a serious
deterioration of it.

399. How Raw, or Brown Sugar is produced. — The sugar of commerce
appears in various forms, and is sold at various prices. It is impor-
tant to inquire into the source of these differences which involves a
reference to the manufacture. Cane-juice contains vegetable albu-
men, a substance which has a strong tendency to fermentation (488),
hence, when left to itself in warm climates, it is rajjidly changed ; the
acid of vinegar being generated ; — twenty minutes is, in many cases,
sufficient to produce this effect. To neutralize any acid that may be
thus formed, and partially to clarify the crude juice, lime, which has a
powerful attraction for organic matter, is added. The juice is then
boiled, the water being evaporated away until a sirup is produced.
The liquid is then drawn off into shallow vessels and stirred. As it
cools the sugar granulates, or appears in the form of small irregular
grains or crystals, which are kept from uniting together by some of
the sirup (which has been so altered by the heat that it refuses to
crystallize), and is known as molasses. The product is then placed in
suitable circumstances to drain, when a large portion of the molasses
flows away, and is collected in separate vessels. The sugar, packed in
hogsheads, is then sent to the market as raw or muscovado, or as it is
more commonly known, as 'brown sugar.

400. Of what Brown Sugar consists. — The article when packed by
the sugar-boiler, consists of sugar more or less browned and dampened
by molasses, according to the completeness of the draining and dry-
ing process. It contains more or less vegetable albumen, lime from
the added lime-water, minute fragments of crushed cane-stalks, often
in considerable quantity, with grit or sand from the unwashed canes,

220 GE]!irEEAL PEOPEETIES OF ALIMENTAET SUBSTANCES.

or which may have been introduced into the granulating vessels by
careless management.

401. Brown Sngar undergoes a slow fermentation, — We have stated
that albumen is a very changeable substance, and by its own decompo-
sition, when in contact with sugar, tends to alter that also. Cane
sugar, it transforms into grape sugar. Hence, in nearly all raw sugars,
there is an incipient, slow fermentation going forward, by which a
portion of cane sugar is converted into grape sugar. Dr. Hassall,
perhaps the highest authority in matters pertaining to alimentary im-
purities, states that nearly aU samples of brown sugar contain also
grape sugar, and that its proportion is greater where there is most
vegetable albumen. This change, of course, just according to its ex-
tent, lowers the value of brown sugar.

402. Living contaminations of Brown Sugar. — We had occasion, when
speaking of water, to correct that common impression of the iU-in-
formed, that swarms of animalcules are present In every thing we eat
and drink. On the contrary, they exist only in certain circumstan-
ces, and when they do occur, of course impair the value of food for
dietetical use. As aU animal structures, from the largest to the

^ „„ smallest contain nitrogen, one

Fig. 90. PIT

of the conditions of the exist-
ence of animalculse is the pres-
ence of nitrogeneous matter
upon which to feed. Now pure
sugar contains no nitrogen, and
therefore cannot sustain animal
life. But in brown, coarse
sugars the existence of vegeta-
ble albumen offers nourishment
to these beings, and accordingly
they are commonly found in-
fested with minute insects called
sugar-mites. In general, the
more the sugar is contaminated
with albumen, the more numer-
ous are these disgusting insects.
They may be detected in the
less pure sugars by dissolving two or three tea-spoonfuls in a large
wine-glass of tepid water. After standing at rest an hour or two, the
animalculfB will be found, some on the surface of the liquid, some ad-
hering to the sides of the glass, and some in the dark sediment at

Sugar-mlte, as seen iipon a fragment of cane,
magnified 130 diameters.

MOLASSES — SUGAB-EEPrNTlSrG. 221

the bottom, mixed with cane-fragments, grit, and dirt. The mite is
visible to the nalied eye, as a mere speck ; the microscope, however,
exhibits its appearance, and history, from the egg state to the per-
fectly developed animal, which is represented in Fig. 90.

403. Properties and Compositioa of Molasses. — Common molasses is a
dense brown liquid, the drainage of the brown sugar manufacture. It
contains a portion of sugar that has been burnt and darkened in boil-
ing ; another part that has been so changed to the mucilaginous state,
by boiling, that it does not crystallize, together with a quantity of
crystallizable sugar. It is strongly absorbent of water ; indeed, many
kinds of raw sugar melt into sirup when exposed to the air. Chemi-
cally considered sugar is an acid substance, and combines with bases,
as potash, soda, magnesia, to form salts called saceharates. Molasses
contains a portion of saccharine matter, combined with the lime used
in the sugar manufacture (399) ; also with small quantities of the alka-
lies. Molasses itself is also acidulous. It has a peculiar strong taste,
which Cadet states may be removed by boiling for half an hour with
pulverized charcoal. Sugar-house molasses and sirups are the residue
which remains uncrystallized in purifying and refining brown sugar.

404. Refined Sngan — To cleanse it of impurities and improve it in
color and taste, crude sugar is refined. It is melted and has mingled
with it a small portion of albumen (ox-blood), which clears it of me-
chanical contaminations. The sirup is then filtered through a bed of
animal charcoal (burnt bones crushed), by which it is decolorized, and
lastly, it is crystallized, by boiling at a low temperature in vacuum-
pans, in which the atmospheric pressure is removed (62). The discol-
oring and darkening principle in the various grades of sugar is the
molasses which has not been removed, but which remains in the crys-
tallized mass.

405. Sugar-candy and how it is Colored. — "When the pure sugar is melted
or dissolved, it forms a clear liquid, and when allowed to cool or dry
without disturbance, it crystallizes into a transparent solid, like glass.
When threads are suspended in the sugar solution, crystals of extreme
hardness collect upon them, which are known as rock-candy. The
cause of whiteness in refined sugar is that the crystals are small, con-
fused, and irregular. To make candy white, the sugar, while cooling,
is agitated and worked (pulled)^ which breaks up the crystals and ren-
ders the mass opaque. Candy is commonly adulterated with flour,
and frequently with chalk. Various colors are given to sugar-confec-
tionery by adding paints and dies expressly for the purpose. Some of
these are harmless and others poisonous. Those which are least inju-

222 GElOaiAL PEOPBETIES OP ALIMEfTTAET SUBSTANCES.

rious are the vegetable and animal coloring matters, but these neither
form so brilliant colors nor are they so lasting as the mineral com-
pounds, which are far the most deadly. The following are the chief
coloring substances used by confectioners to beautify their sugar
preparations :

( Oxide of lead (red lead).

Eeds J Bisulplmret of mercury {DermiUon).

( Bisulpliuret of arsenic (red orpimenf).

I Gamboge.

Yellotts. . . •< Chromate of lead (chrome yellow).

( Sulphuret of arsenic (yelloio orpiTntnt).

( Ferrocyanide of iron (Prussian dlue).

I Cobalt.

Bltjes J. Smalt (fflass of codalf).

> Carbonate of copper (verdiier).

I. Ultramarine.

( Diacetate of copper (verdigris).

Greens ■< Arsenite of copper (emerald green .

( Carbonate of copper (mineral green).

Whites Carbonate of lead (white lead).

PuEPLEB Formed by combining blues and reds.

From an examination of 101 samples of London confectionery, Dr.
Hassall found that 59 samples of yellow were colored with chromate
of lead and 11 with gamboge. That of the reds 61 were colored with
cocTiineal.! 12 with red lead., and 6 with vermilion. Of the blues, one
sample was colored by indigo, 22 by Prussian Hue, and 15 by ultra-
marine. Of the greens 10 were colored by a mixture of chromate of
lead and Prussian dlue, 1 with carbonate of copper, and 9 with arsen-
ite of copper. These colors were variously combined in the diiferent
cases, as many as from three to seven colors occurring in the same
parcel, including three or four poisons.

406. Their daEgerons and fatal Effects. — The Dr. remarks: "It may
be alleged by some that these substances are employed in quantities
too inconsiderable to prove injurious, but this is certainly not so, for
the quantity used, as is amply indicated in many cases by the eye
alone, is often very large, and sufficient, as is proved by numberless re-
corded and continually recurring instances, to occasion disease and
death. It should be remembered, too, that these preparations of lead,
mercury, copper, and arsenic, are what are termed cumulative, that is,
they are liable to accumulate in the system, httle by little, until at
length the full effect of the poisons become manifested. Injurious con-
sequences have been known to result from merely moistening wafers
with the tongue ; now the ingredients used for coloring these include

GUMS AND OILS. 223

many that are employed in engar confectionery. How mucli more in-
jurious, then, must the consumption of sugar thus painted prove when
these pigments are actually received into the stomach."

D.— Tlie Gums.

407. Properties of the Gums. — The juices of many plants contain
substances which ooze out through the bark, forming rounded trans-
parent masses of gum, as we often see upon cherry, plum, peach and
apple trees. The gums differ considerably in properties. Cherry-tree
gum is insoluble in cold water, but dissolves readily in boiling water,
while gum-arabic dissolves in cold water, and gum-tragacanth dissolves
in neither, but only sweUs up into a kind of mucilage. The solutions
of gums are clear and tasteless, and have a glutinous and sticky nature,
which adapts them for paste.

408. Artificial Gum. — "When common starch is heated to 300 degrees
in an oven, or boUed in water made sour by a little sulphuric acid, it
is so altered as to dissolve in cold water, forming a clear, viscid solu-
tion. The substance thus produced from the starch has the properties
of gum, and is known as dextrine.

409. How Gum is Composed. — In chemical composition, gum and
dextrine do not differ from starch; they consist of 12 atoms of
carbon combined with 10 of water. Gum exists in grains, and many
vegetables, and hence is a widely-diffused element of food, although it
does not occur in large quantities. Its dietetical value, as shown by
its composition, is the same as starch and sugar, and hence it is
grouped with the saccharine alimentary principle.

£.— Tbe Oils.

410. Distinction between Volatile and Fixed Oils. — Oils are of two
classes : 1st, those which, when smeared upon paper, produce a stain
or grease spot, which does not disappear by time or warmth, and
hence called Jixed oils; and, 2d, such as wiU vanish from paper,
under such circumstances leaving no permanent stain, and there-
fore called volatile oils. The former is a xmiversal and important
element of diet, the latter presents itself chiefly among condiments,
and wiU be there considered.

411. Sonrces and Forms of Oily Bodies. — Oil is largely procured both
from plants and animals, and from both sources it is chemically the
same thmg. It exists in many parts of vegetables, but is chiefly
stored up in their seeds, from many of which it is obtained by pressure

224 GENEKAIi PEOPERTIES OP ALIMENTARY SUBSTANCES.

in large quantities. In animal bodies it is deposited in the sacks or
cavities of cellular tissue, and becomes accumulated in large quanti-
ties in different parts of the body. Oils and fats are chemically iden-
tical, differing only inconsistence, and this quaUty depends upon tem-
perature. Lowering the temperature of a liquid oil sufficiently,
changes it to a solid, while raising that of a solid tallow converts it
into a flowing oil. That which, in the hot climate of Africa, is liquid
palm oil, is with us solid ^aZm 'butter. Those oils, however, which at
ordinary temperatures are not perfectly fluid, but have what is called
an oily consistence, become much thinner and completely liquid when
heated.

412. Proportion of Oil in Articles of Diet. — The proportion of oily
matter from many sources is variable, as in the case of meat, which
may more or less abound in fat. Nor has its amount in many vege-
tables been determined with sufficient certainty. The following are
the quantities given by the later authorities : '

Yolk of Egg 28-75 per cent.

Ordinary Meat (Libbig) 14-03 "

Indian Corn 9' "

Oatmeal (husk excluded) 6" "

CoVe Milk 3-13 "

Eye Flour 8-5 "

Wheat Flour 1 to 2 "

Barley Meal 2- "

Potatoes (dried) 1* "

Eico "8 "

Buckwheat "4 "

^13. Its Composition. — Oleaginous bodies are distinguished from
all the other alimentary principles, by their chemical composition, and
the resulting properties. They resemble the preceding substances
which we have been considering in containing three elements, carbon,
hydrogen and oxygen ; but they differ from all of them in this im-
portant respect, that they are composed almost entirely of hydrogen
and carbon, with but a small proportion of oxygen. The composition
of hogs-lard, as given by Oheveeul, may be taken as an example of
the general structure of this alimentary group. It consists of carbon
79, hydrogen 11, oxygen 10 parts in a hundred. We have seen that
hydrogen and carbon are the active flre-producing elements of fuel
(80). As the oils are so rich in these, they rank high as combus-
tibles, burning with great intensity, and yielding much heat. It has
been also noticed that oils may be decomposed into several acid and
basic principles (196).

THE ACIDS FOUND IN FRUITS. 225

F.— The Vegetable Acids.

414. Combination and Composition, — The sourness of fruits and suc-
culent vegetables is due to various acids produced in the plant, and
which they contain usually in quite smaU proportions. They exist in
two states : 1st, as pure acids, or free, when they are strongest ; and,
2d, combined with bases, as potash, lime, &c., by which they are
partially neutralized, and thus rendered less pungent to the taste. In
this case they exist as acid salts (691). The vegetable acid group con-
sists of but three elements, carbon, oxygen, and hyorogen, like the
starch and oil groups, but it is distinguishable from them by contain-
ing but a small share of hydrogen and a large proportion of oxygen.
The composition of the different vegetable acids is quite variable, but
they all agree in possessing less hydrogen and more oxygen than any
other class of organic alimentary principles. Their nutritive value is
very low.

415. Acid of Apples — Malic-Acid, — This is the peculiar acid of apples,
and it is also found la numerous other fruits. Thus, it exists free in
pears, quinces, plums, peaches, cherries, gooseberries, currants, straw-
berries, raspberries, blackberries, elderberries, pineapples, grapes,
tomatoes, and several other fruits. It exists very abundantly in green
apples, causing their extreme acidity, and diminishes as they ripen.
The wild crab-apple is much richer in malic-acid than the cultivated
fruit, and generally speaking, in proportion as we obtain sweetness by
culture, we deprive the apple of its malic-acid. No use is made of
this acid in the separate state.

416. Acid of Lemons — Citric- Acid — Gives their sourness to the lemon,
orange, citron, and cranberry. Mixed with malic-acid, it exists also
in the gooseberry, red-currant, strawberry, raspberry, and cherry.
Citric-acid is separated from lemon juice, and sold in the form of crys-
tals, which may be at any time redissolved in water, and by flavoring
with a little essence of lemon, an artificial lemon juice is produced,
which is used like the natural juice in the preparation of refreshing
and cooling beverages.

417. Acid of Grapes — ^Tartaric-Acid, — This acid in the free state ex-
ists in the grape, and is found besides in some other fruits. It also
exists abundantly in the grape in combination with potash, as acid,
tartrate of potash, or cream-of-tartar. Tartaric-acid is prepared and
sold in the crystalline form as a cheap substitute for citric-acid, or
lemon juice. It does not absorb moisture when exposed to the air
like citric-acid, but is inferior to it in flavor. The commercial efter-

10*

226 GENERAL PEOPEETTES OF ALIMENTAET SUBSTAJ!fCES.

veacing, or soda powders^ consist of 30 grains of bicarbonate of soda,
contained in a blue paper, and 25 grains of tartaric acid, in a white
paper, to be dissolved in balf a pint of water.

418. Oxalic-Acid — ^Exists in sorrel, and also in the garden rhubarb
or pie-plant, combined with and partially neutralized by potash or
lime. It is a prompt and mortal poison when pure, and fatal results
frequently occur from mistaking its crystals for those of Epsom salts,
which they much resemble.

419. YcgetaWe Jelly, Pectine or Pectic-Acid. — This is obtained fi*om
the juice of apples, pears, quinces, currants, raspberries, and many
other fruits ; also, from turnips, carrots, beets, and other roots. It is
composed similarly to the vegetable acids, having an excess of oxygen.
Vegetable jelly is thought not to exist exactly as siich in the plant-
juices, but to be produced from another substance in the process of its
separation. The substance from which it is obtained is soluble in the
vegetable juices, but the jelly itself is scarcely soluble in cold water.
Boiling water dissolves it, but it coagulates again as the water cools.
It is commonly prepared by mixing sugar with the juice, and suffering
it to stand for some time in the sun, by which a portion of the water
is evaporated ; or it may be boiled a short time. But when long
boiled, it loses the property of gelatinizing by cooling, and becomes of
a mucilaginous or gummy nature. This is the reason that in making
currant or any other vegetable jelly, when the quantity of sugar is not
sufficient to absorb aU the water, and consequently it becomes neces-
sary to concentrate the liquor by long boiling, the mixture often loses
its peculiar gelatinous properties, and the jelly is of course spoiled.
It differs from animal jeUy in containing no nitrogen, and although
readily digestible, it is supposed to be but slightly nutritive. Isinglass
is often added to promote the stiffening of vegetable jellies, and sugar
also has a similar effect. They form cooling and agreeable articles of
diet for those sick with fevers and inflammatory complaints. Jams
consist of vegetable pulps preserved with sugar. They are very simi-
lar in their uses and effects to the fruit-jellies, from which they prin-
cipally differ in containing a quantity of insoluble, and therefore indi-
gestible ligneous matter (or vegetable membranes, ceUular-tissue and
sometimes seeds), which in the healthy state of the system contribute
by their mechanical stimulus to promote the action of the bowels, but
in irritable conditions of the alimentary canal, sometimes prove injuri-
ous. (Pereiea.)

420. Acetic Acid, or Vinegar. — The acid in most general use for diet-
etical purposes is the acetic, or acid of vinegar, which we obtain by

TE[E ALBUMINOUS PEINCIPLES. 227

fermentation (491). Good strong vinegar contains about four per cent.
of the pure acid. Vinegar may be easily made at any time by adding
ferment, or yeast, to water sweetened with sugar or molasses, or any
sweet vegetable juice, and exposing the whole for a reasonable time to
the air in a warm place. Vinegar itself added to the mixture will act
in the way of yeast to start the operation. There accumulates in old
vinegar a thick, ropy matter, called mother^ because it is capable of
producing the acetous change in a sugary solution. It consists, like
yeast, of vegetable cells (496). The juices of most fruits contain all
the elements necessary for fermentation and souring. Apple and grape
juice, at first, undergo the vinous change producing cider and wine, and
the process continued converts them both into vinegar (cider-vinega/r
and wine-vinegar), which are prized, on account of the fruity aroma
which accompanies them.

2. — PRESrOIPLEa CoKTAIUXNa NlTEOGEHr. '
A.— Vegetable amd Animal Albumen.

421. It exists in both organized Kingdoms. — We are aU familiar with
albumen or white of eggs, and recollect the remarkable change it un-
dergoes by heat, being coagulated or altered from a transparent liquid
to an opaque, white, brittle solid. This substance exists in smaJl pro-
portions dissolved in the juices of plants. If such juices are clarified
and then boUed, the albumen coagulates in thin flakes, and may be
separated from the liquid. The same substance exists also in small
quantities, laid up dry and solid in seeds and grains, but its exact pro-
portion in various parts of plants has not been ascertained. Albumen
exists also in animals, and is a much more abundant constituent of
these than of plants. It constitutes, according to EEG^yfAirxT, about 19
per cent, of healthy human blood, and is therefore found in large
quantities in all parts of the system. It exists in the pecuhar animal
juices, in the glands, nerves, brain, and around the muscular fibres of
flesh.

422. Composition of Aibnmen. — In composition, albumen differs widely
from the aliments we have considered ; it contains not only the ali-
ments they contain — carbon, oxygen, and hydrogen, — but in addition,
a large proportion of nitrogen, and also a minute amount of sulphur.
The chemical structure is thus complex. The result of the latest
analysis is, that a compound atom of albumen consists of 216 carbon,
189 of hydrogen, 68 of oxygen, 27 of nitrogen, and 2 of sulphur.
The albumen of eggs, however, contains a slightly larger proportion

228 GENEEAL PEOPERTIES OF ALIMENTAET SUBSTANCES.

of sulpliTir. Vegetable and animal albumen are essentially the same
thing in properties and composition, differing no more upon analysis
than two samples from the same source.

423. General Properties of Albnmen. — It exists in two states — soluble
and insoluble, or coagulated. The coagulation is effected by simple
heat ; but there is much confusion of statement among different writers
as to the point of temperature at which it sohdifies. This depends
upon circumstances. A moderately strong solution of pure albumen
in water becomes turbid at 140°, and completely insoluble at 145°, and
separates in flakes at 167°. When excessively diluted, no turbidity
can be produced by a less heat than 194°, and it will only separate in
solid masses after it has been boUed a considerable time. As a general
rule, albumen coagulates with greater difficulty in proportion to the
quantity of water in which it is dissolved. Coagulated albumen
refuses to dissolve in cold water, merely swelling up in it. There are
many substances which, if mixed with it, coagulate albumen when
cold, as alcohol and corrosive sublimate, the mineral acids, and many
salts, while the presence of alkalies hinders its coagulation. The
change of coagulation does not alter or disturb its composition.

SS.— Veg'dal>le and Animal Casein.

424. Sonrce and CompositioDi — The water in which flour has beea
washed or difl^used, as in separating starch, contains a small portion
of a dissolved substance, which is coagulated by the addition of an
acid, and may be then separated. It is called vegetable casein^ and is
found in the largest proportion in peas and beans, constituting from
20 to 28 per cent, of their weight. This substance is identical in
properties Avith the curd of mUk, which is known as animal casein,
and is the chief ingredient of cheese. The identity of vegetable and
animal casein is well illustrated by the fact that the Chinese make a
real cheese from peas. They are boiled to a thin paste, passed through
a sieve, and coagulated by a solution of gypsum. The curd is treated
like that formed in milk by rennet. The solid part is pressed out,
salted, and wrought into cheese in moulds. This cheese gradually
acquires the smell and taste of milk cheese ; and when fresh, is a
favorite article of food with the people. The composition of vegeta-
ble and animal casein is nearly if not quite identical with that of
albumen (422).

C— "Vegetable and Animal Fibrin.

425. The Blood and Vegetable Jiiic«s. — When blood is drawn from

FIBEm AND GLUTElsr.

229

Fig. 91.

Fibres of lean meat magnified.

the living body, in a short time it clots ; that is, a net-work of fibres is
formed within it. These fibres consist of animal fibrin, which was
dissolved in the blood, and then took on the solid form {spontaneous
coagulation). Vegetable juices, as those expressed from turnips, car-
rots, beets, &c,, also contain the same kind of matter which they deposit
on standing, that is, it spontaneously coagulates^ and this is known
as vegetable fibrin. If a piece of
lean beef be long washed in clean
water, its red color, which is due to
blood, gradually disappears, and a
mass of white fibrous tissue re-
mains, which is known as animal v^
fibrin. The accompanying diagram
(Fig. 91) shows its structure as seen
under the microscope. The paral-
lel fibres have cross markings, wrinkles, or striaa. By the contraction
of a muscle in the living animal the stri« are made to approach each
other, become less distinct, and the fibre increases considerably in
breadth and thickness.

426. Glnten. — If wheat flour be made into a dough, and then
kneaded on a sieve or piece of muslin under a stream of water
(Fig. 92), its starch is
washed away, and there
remains a gray, elastic,
tough substance, almost
resembling a piece of ani-
mal skin in appearance.
"When dried it has a glue-
like aspect, and hence its
name, gluten. "When thus
produced, it consists chiefly
of vegetable fibrin ; but it
contains also a little oil,
with albumen and casein.
That from other grains is
dilferent in the proportion
of these constituents ; rye
gluten, for example, con-
sists largely of casern, and has less of the tenacious fibrmous princi-
ple. By acting upon crude gluten with different solvent agents, it
is separated into four principles as follows :

Fig. 92.

230 GENERAL PEOPEETTES OP ALIMENTAEY SUBSTANCES.

Vegetable fibrin 72 per cent

Gluten 20 "

Casein (mucine) 4 "

Oil 87 «

Starch (accidental), small quantity

Total 99-7 "

427. Animal Fibrin, — The muscles or lean meat of animals are prin-
cipally composed of this substance, its proportionate quantity being
greatest in flesh that is dark-colored, and belongs to animals that have
attained their full growth. Its characters vary somewhat in different
animals, and in the same animal at different ages. Its color is vari-
able ; in beef and mutton it is red ; in pigeons and many kinds of
game it is brownish ; pink in veal, salmon color in pork ; in fish, white
or semi-trausparent, though aU animals yield it on various colors.
When washed free from blood and other foreign substances, pure
fibrin is white and opaque, but darkens by drying.

428. Properties of the Sitrogenons Principles. — Whatever their form or
source, these substances are identical in composition, a fact of great
importance in connection with animal nutrition. They present varia-
tions of aspect and physical properties, and different solubilities, albu-
men and casein being soluble in water, while the others are not ; and
while fibrin coagulates or solidifies spontaneously, albumen is altered
in the same manner by heat, and casein by acids. It is possible tliat
some of these conditions may be influenced by the mineral phosphates
which these substances contain in variable amount, but this point is
not yet determined. These substances are decomposed by heat, and
exhale a pungent odor like that of burnt feathers. They may be long
preserved when dried, or even in the moist state when cut off from
the atmosphere ; but in contact with air and moisture they quickly
decompose, putrefy, and call into existence a host of microscopic ani-
malculae. We shaU consider these substances again (678).

D.— Gelatin.

429. Its Sonrces, Properties and Uses. — There exists in the bone, carti-
lages and various membranes of animal bodies, a principle rich in ni-
trogen, called gelatin. It is not identical in composition with the ni-
trogenous class which we have been considering, nor is it like them
produced in the vegetable kingdom ; but it is supposed to be derived
from them in the animal system. It dissolves in hot water, and when

cooled, forms a white jelly. It is the universal principle of animal
jellies. Common glue consists of gelatin, but in this form it is not

DIFFERENT NAMES OP THE OTTE0GEN0U8 PEmCIPLES. 231

used dietetically. Isinglass is a preparation of gelatin in various forms
to be used as food. It is mainly procured from the air-bag or bladder
of fishes. Tour parts of isinglass convert 100 of water into a trem-
bling jelly. Gelatin is also extracted from calves' feet, in forming calves'
foot jelly ^ and calves' heads are also employed to furnish jelly in mak-
ing mock turtle soup. Gelatin is used not only to produce jellies, but
to thicken and enrich gravies and sauces, and also as a clarifying or
' fining ' agent to clear coffee or other mixtures.

430. Different Names applied to these Substances. — The recent rapid
progress of organic chemistry, has brought this class of substances for-
ward into new and highly interesting dietetical relations, and there
has been a confusion in the terms applied to them, which, though
perhaps inevitable, is at first very embarrassing to unscientific readers.
As they all contain nitrogen^ they are called nitrogenous alimentary
principles ; and as one of the names of nitrogen is azote, they are call-
ed azotized compounds. As they have all (except gelatin) the same
composition as albumen, and are convertible into it, they are often
called albuminous substances. As they form the material from which
the body is nourished and built up, Liebig named them plastic ele-
ments of nutrition ; they are also called nutritive principles, the^esA-
forming and blood-malcing substances. Muldee supposed that a com-
mon principle could be separated from all of them by getting rid of
sulphur, (of which they contain variable traces,) and he called this
principle ^rc»^^w, and hence the group has been gs^qH protein or pro-
tcinaceotis compoxmds. Mitlder's peculiar views are abandoned, but
his terms are stUl in current use.

3. Compound Aliments. — Vegetable Foods.

431. Our common articles of diet consist of the alimentary princi-
ples which have just been noticed, combined together and forming
what are known as compound aliments. They are naturally divided
into vegetable foods and animal foods ; of the former first.

A.— The Grains.

432. Composition of Wheat. — We begin with wheat, the prince of
gi'ains. It consists of gluten, starch, sugar, gum, oil, husk, and water,
with salts that are left as ash when it is burned. It is maintained by

• some that there is really no sugar present in the ripe grain, especially
in wheat, but that it is produced by the action of air and water upon
the starch during the process of bread making, or analysis. The
proportion of constituents in wheat is liable to considerable variation.

232 GENERAL PKOPERTIES OF ALIMENTARY SUBSTANCES.

from many causes, as variety of seed, climate, soil, kind of fertilizers,
seed, time of harvest, &c. We give five analyses.

"VVater

YArQUELIN.

Dumas.

Beck.

Flinty
Wheat.

Soft
Wheat.

Flinty
Wheat.

Soft
Wheat.

Genesee
Wheat.

12-00
14-60
56-50
8-50
4-90
2-30

10-00
12-00
62-00
7-40
5-SO
1-20

12-00

14-55

56-50

8-48

4-90

2-30

10-00
12-00
62-00
7-36
5-Sl
1-29

12-40
11-46
70-20

|-5-20

Gluten

Starch

Gum

Total

98-80

98-40

98-73

98-46

99-26

433. Proportion of Gluten in Wheat. — It will be shown when we come
to speak of the physiological influence of foods, that the most valuable
portion, the strictly nutritious part, is that containing nitrogen, and
that therefore 'gluten,' the properties of which have been noticed
(426), is of the first importance in examining the grains. From an
analysis of six samples of wheat, made by VAUQUELiisr, we get an aver-
age of 11"18 per cent, of gluten ; Dumas, from three samples obtain-
ed an average of 12 '50 per cent. ; and Dr. Lewis 0. Beck, -who made
an investigation of the subject, at the direction of the Federal Govern-
ment, and of 33 samples of wheat, gathered from all parts of the coun-
try, procured an average of 11 "72 per cent, of this constituent, the
specimens ranging from 9*85 to 15'25 per cent. The mode of exam-
ination, however, adopted by Dr. Beck — that of washing away the
starch by a stream of water (426) — is not the most accurate. A por-
tion of albumen and casein, with small particles of gluten, are carried
away by the stream — which would make the remaining quantity an
under-statement of the true proportion of nitrogenous matter. This
loss is assumed to be compensated for by the oil retained in the gluten,
and the result is thus to a certain degree guessed at. Hoesfoed pro-
ceeded more accurately, by making an ultimate analysis of the wheat,
and calculating the amount of nitrogenous matter by the quantity of
nitrogen finally obtained. Six samples of wheat thus treated, yielded
15 -14 per cent, of gluten. Quantities of gluten are mentioned by
Davy and Boussingalt as high as 20 or 30, and even 35 per cent., but
these are probably erroneous over-statements. For general purposes
we may adopt Dr. Beck's results — 11-72 of gluten, or in even num-
bers 12 per cent.

434. Quality of the Glnten of Wheat. — But not only do wheats differ
in the proportion of gluten, but also in its quality. In some it is more
tough and fibrous, or ' sounder ' and ' stronger, ' than in others.

THE GLUTEN AND WATER OF WHEAT. 233

Moreover, any injury or damage that flour may sustain, is most
promptly manifested by a change in the gluten ; it is both reduced in
quantity and diminished in tenacity. Flour dealers and bakers deter-
mine the quality of flours by making a few grains into a paste with
water, when its value is judged of by the tenacity of the dough, the
length to which it may be drawn into a thread, or the extent to which
it may be spread out into a thin sheet. M. Boland has invented an
instrument for determining the quality of gluten. A little cup-shaped
copper vessel, which will contain about 210 grains of fresh gluten, is
secured to a copper cylinder of three -fourths inch diameter and six
inches long. It is then heated to about 420° in an oil bath. The
gluten swells, and according to its rise in the tube so is its quality.
Good flours furnish a gluten which will augment to four or five times
its original bulk, while bad flours yield a gluten which does not swell,
but becomes viscous and nearly fluid, adhering to the sides of the tube,
and giving off occasionally a disagreeable odor, whilst that of good
flour merely suggests the smell of hot bread. — (Mitchell.)

435. Macaroni and Vermicelli are pastes formed from wheaten flour,
and made to take various shapes by being passed through holes in me-
tallic plates. Those flours are best adapted for this preparation which
make the toughest paste ; those, therefore, which are richest in gluten,
and where this element is of the best quality. The wheat of southern
or warm climates is said to abound most in gluten, and hence to be
better fitted for this production. Our chief supplies of macaroni are
from Italy. The English have attempted the manufacture by separat-
ing the gluten of one flour and incorporating it into another. Their
success has been but indifferent, nor have we succeeded satisfactorily
with it in this country. The best macaroni should retain its form, and
only swell after long boiling, without either running into a mass or
falling to pieces.

436. Water ia Wlieat. — The wheat grain consists of a solidified veg-
etable mUk. As the grain ripens, evaporation of water takes place,
and the mUk condenses into a hard mass. Wheat ripened under the
hot sun of this diy climate evaporates much of its water, and dries
harder, with a tendency to shrivel in the berry ; while in the cooler
and damper climate of England longer time is allowed for ripening,
and evaporation is slower, so that the same variety of English wheat
presents a larger and plumper berry than if grown In this country.
Dr. Beck's examination gave an average of 12-78 per cent, of water,
the range being from 11-75 to 14-05. Different wheats, however, are
stated to vary in their natural proportion of water so widely as from
5 to 20 per cent.

234 GENERAL PROPERTIES OP ALIMENTARY SUBSTANCES.

437. Grinding of Grain. — Grain is converted into flour by being
ground between two horizontal stones, the upper of which revolves,
while the lower is stationary. The mill-stones (buhr-stones) are com-
posed of a peculiar hard and porous sand-stone, so that the working
surfaces consist of an infinite number of minute cutting edges. There
is an opening in the centre of the upper revolving stone through
which the grains are dropped. The lower stone is convex and the
upper one is concave, so as to match it ; but they do not perfectly
join or fit. From the centre outwards, they approach closer together,
so that the grain is first coarsely crushed, and then cut finer and finer
as it is carried to the circumference by the centre-flying (centrifugal)
force. The crushed grain, as it leaves the stones, is not an absolutely
uniform powder, composed of equal sized particles, but consists of
parts which have been diff'erently aff'ected by the grinding process.
Some are coarser, and others flner, so that it becomes possible to
separate them. The ground mass is therefore conveyed away and
bolted ; that is, passed through a succession of sieves, and separated
into several parts, fine flour, coarse flour, bran, &c.

438. Stractnre of the Grains. — When we consider wheat or other grain
with reference to its grinding and sifting capabilities, the proportion
and quality of its separated products, several things require notice in
regard to the structure of the kernel or berry. Each grain consists of
a farinaceous body, enclosed in a membranous husk or skin. This
husky envelope varies in properties ; in some wheat it is thin, smooth,
and translucent ; in others, rough, thick, and opaque ; in some fight-
colored, in others dark ; in some tough, in others brittle ; and in some
it peels or flakes off readily under the stones, and in others it is very
adherent to the kernel. The other elements of the seed, albumen, glu-
ten, starch, and oil, and the salts which it leaves as ash when burned
(446), are not equally distributed throughout its mass. Immediately
beneath the incrusting husk, is a layer of matter of rather a darkish
color, and not very easily reduced to an impalpable powder. It is
rich in gluten, and contains oil, which exists in minute drops enclosed
in cells. Underneath this is the heart of the seed, which is whiter
and more readily crumbles to a fine dust. This part consists more
purely of starch, and forms the finest and whitest flour. There is
a certain degree of interdiffusion of these elements throughout the
body of the seed, yet, upon dissection, they are each found in excess
in the parts indicated.

439. Anatomy of Grains Illnstratcd. — An idea may be gathered of this
distribution of substances throughout the cereal seeds, by the accom-

STEUCrUEE OF THE CEEEAL GEAINS.

235

panying section of a grain of rye highly ^^^ ^^

magnified (Fig 93) : a represents the outer _; - -_. "^'^ — -

investing seed-coat, consisting of three s?C^]£f-— ^^'Ci^oc n
rows of cells; &, an inner membrane or cS'^j," ' '^TiBliMIB''
seed-coat, composed of a single layer of te^^45%)^^^^^^^^^^
cells ; c, a layer of cells containing gluten. ^^^M^^i^^^&l^
These three form the bran ; d, cells con- j^^^^^^Kl^^^^Jf^
tainiug starch grains in the interior of ^^^li^\^/^^^M'^^
the seed. Fig. 94 represents a ceU con-
taining starch, more highly magnified, and Fig. 95, the appearance of
the grains of rye starch viewed by a still stronger power.

440. Parts Separable by Sifting. — These several portions oppose un-
equal resistance to the pulverizing force of the mill-
stones. The outer fibrous portion which forms the bulk
of bran is least afiected ; the tough coherent gluten is
divided stiU finer, while the brittle starch, of which the yC^v
grain is mainly composed, is crushed most completely. |">pS|
As the particles of these substances, therefore, are of Iji^^jiP'fiS!)
different sizes, they may be separated by a bolting cloth,
having different degrees of fineness of texture. The
product is divided by the miUer according to custom or
fancy, fom* or five grades being often established, which, of course,
vary much in composition and properties.

441. Properties and Composition of Bran. — ^From what has been said
of the husk, it will appear that the quantity of bran yielded by differ-
ent wheats, is liable to variation (438). As the

husk is detached with different degrees of ease, it

is evident that it may carry with it more or less

adherent matter of the grain, by which its com- ,;. '-/-x-i^ wvv

position will be made to fluctuate. Johnstoit '^^'^^^

states, that in good wheat the husky portion

amounts to between 14 and 16 per cent, of its it((fl^

whole weight. The same authority found six

wheats to yield bran of an average composition,

as follows :

Water 13-1

Nitrogenized matter 19'3

OU 4T

Husk, and a little starch 55-6

Saline matter (ash) 7-3

100

236 GENERAL PEOPEETIES OP ALIMENTAET SUBSTANCES.

This discloses the nitrogenous matter, the oil, and the salts, in larger
proportion than they exist in the interior of the seed. The excess
of oil existing in the husks of Avheat, helps to protect it against the
penetration of moisture, and enables it to be washed (which ought al-
ways to be done before grindiug), without wetting the inner part of
the grain.

442. White and dark-colored Flonrs. — In separating flour into dif-
ferent grades, the finest and whitest will contain the largest quantity
of starch, while the coarser will more abound in gluten, and present
a darker color. From the soft wheats the bran peels off readily under
the stones, and separates perfectly in bolting; and as these varie-
ties contain least gluten, they yield the whitest or superfine flours.
But the outer coating clings so closely to the hard or flinty sorts, that
much of it is ground up finely with the flour, imparting to it a dark
color, an effect which is also heightened by the larger proportion of
gluten existing in the harder kinds. It is thus apparent that white-
ness is not an indication of nutritive value of flour, but rather the
reverse. "We may add here, that flour of the first quality holds
together in a mass when squeezed by the hand, and shows impressions
of the fingers and even the marks of the skin much longer than when
it is of inferior grade. The dough made with it is gluey, ductile,
and elastic, easy to be kneaded, and which may be drawn out into
long strips, or thinly flattened without breaking.

443. Loss of Weight by Evaporation. — "When wheat is kept for several
months, it loses water by evaporation, becomes denser, and one or
two pounds a bushel heavier. "When ground it gets hot, and stiU
more of its moisture is evaporated, so that the flour and bran,
although twice as bulky as the wheat, weigh some two or three per
cent. less.

444. Injnrions changes in Flour. — ^Wheaten flour becomes whiter
with age, but it is at the expense of gradual deterioration of flavor,
sweetness, and nutritive quality. Beegs kept various samples of
flour, and found that the second and third qualities, which contained
most gluten^ were completely spoiled, after keeping only nine months,
though preserved in casks in a cool, airy, and dry warehouse. Mit-
CHERLicn and Keockee showed that wheat in which sugar was proved
to be absent before sending it to the miU, yielded, after being ground,
4 per cent, of it. Starch was thus transformed into sugar, which could
not be done otherwise than through the internal action of the gluten
aided by air and superabundant moisture (4Y3). The mutual action
of the gluten, and the natural moisture of the flour, seem often capa-

THE GEAESrS — WHEAT. 237

ble, at common temperatures, of slowly bringing about this injurious
change. But when the flour comes out hot from the friction of the
stones, and is left to cool gradually in large heaps, decomposition quickly
sets in, starch is changed to sugar, and perhaps sugar to alcohol, and
even alcohol to vinegar ; so that the process advances rapidly to the
souring stage. This action always takes place in the middle of the
heap first, and proceeds towards the surface, the air enveloped in
the flour, and the heat produced by chemical action, favoring the
change most in the centre. Flour, as soon as ground, should therefore
be conveyed to properly- constructed chambers, and quickly cooled, or
if it be desired to preserve it for some time, it should be dried at a
low heat. The amount of damaged flour thrown into the market is
immense. Large quantities of it are due to careless and imperfect
cooling, by which chemical changes are commenced, which time con-
tinues. Sometimes, to separate the bran most perfectly and procure
the whitest flour, the miUer moistens the grain previously to grinding ;
but if such flour is packed in barrels or sacks without artificial drying,
it rapidly moulds and sours. From these considerations, we infer
the desirableness of procuring flour for household use, freshly ground,
and frequently from the mill, where that is practicable.

445. Farina. — A wheaten preparation under this name has come
recently into general use, the same formerly known as 'pearled
wheat.' It consists of the inner portion of the kernel of the flnest
wheat, freed from bran and crushed into grains, {granulated,) the fine
floury dust and smaller particles being all removed. In cooking, it
absorbs much water or mUk, and forms an easily-digestible prepara-
tion, readily permeable by the juices of the stomach. In consequence
of containing nitrogenous matter, it is greatly superior in nutritive
power to cornstarch, arrowroot, tapioca, as a diet for invalids and
children (746). Prof. J. 0. Booth of Philadelphia, analyzed Hecker's
Farina with the following results: Starch 60'4, nitrogenous matter
11"6, gum 2-9, sugar 2'41, bran 2-1, water 9'9. Professor Booth re-
marks : " The analysis is sufiicient to show the excellent qualities of
the farina, whether as a simple diet for invalids, or as an excellent
food for the healthy."

446. What Minerals exist in Wheatt — "When wheat is burned, there
is left about 2 per cent, of ash, which consists of various mineral in-
gredients. An average of 32 of the most recent and reliable analyses
gives the leading constituents, as foUows: Phosphoric acid 46 per
cent., (nearly half its weight,) potash 29'97, soda 3-30, magnesia 3*35,
Bulphuric acid '33, oxide of iron '79, and common salt -09. Phoa-

238 GENEEAL PE0PEKTIE3 OP AlilMENTAEY BUBSTANCES,

phoric acid is the characteristic and predominant element, potash and
magnesia occurring next in the order of quantity. These mineral sub-
stances are unequally diffused throughout the seed. Johnston has
shown by an analysis of six samples of wheat, the ground product of
which was divided into four qualities, that the mineral substances ai'e
distributed as follows. "We give the average: — ^fine flour 1*08 per cent,
next grade 3*8, coarser still 5-2, bran 7*2. The ash of bran contains
considerable sUica. The presence of these mineral substances is far
from accidental, as was formerly supposed ; we shall point out some
of their important uses in the system when considering the physio-
logical effects of food (690).

447. Properties and Compositton of RyCi — This graia ranks next to
wheat in bread-making and nutritive qualities. It produces a larger pro-
portion of bran than wheat, yielding less flour, and that of a decidedly
darker color. It contains more sugar than wheat, which accounts for
the sweet taste which is peculiar to new rye-bread. Its husk has an
aromatic and slightly acidulous flavor, which renders it agreeable to the
palate. The bran should not, therefore, be entirely separated from
the flour ; for if the grain be ground fine and divested entirely of the
husk, the bread will be deprived of much of its pleasant taste. The
gluten of rye flour, although sufficiently tenacious to make good bread,
is less tough and fibrous than that of wheat. Indeed it is more prop-
erly a kind of casein (424), or 'soluble gluten,' for when rye dough
is washed with water, instead of remaining together in an adherent
mass, its gluten diffuses itself throughout the liquid. Rye is generally
stated to be less rich in the nutritive nitrogenous constituents than
wheat. It has not been so thoroughly examined as that grain, but the
analyses that have been made would seem to show that it is very
little, if at all, inferior to it in nutritive power. Botjssikgatjlt obtain-
ed from the grain of rye 24 per cent, of bran, and 76 of flour. He
separated by drying 17 per cent, of moisture, and the dry flour gave of

Eye (Bocssinqadlt). Rye (Poggaile).

Gluten, albumen, &c 10'5 Nitrogenous matters 8'790

Starch 64'0 Starcli and dextrin 65'533

Gum 11-0 Fatty matters 1-992

Fatty matter 8"5 Lignin 68S3

Sugar 3-0 Mineral matters 1'772

Epidermis and salts C'O "Water 15'530

Loss 2-0

A sample of rye di'ied in Prof. Johnston's laboratory, lost 14"50 per
cent, of water. Hoksfoed examined four samples of European rye,

THE GBAINS — ^INDIAN COEN — OATS. 239

and obtained an average of 14 per cent, of water, and 13*79 per cent,
nitrogenous compounds.

448, Indian Cora or Maize. — This grain is distinguished chemically by
containing a larger proportion of oily or fatty matter than any other.
It is quite rich in nitrogenous constituents, though less so than wheat.
Its peculiar protein element takes the name of zein (from zea maize,
the botanic name of Indian corn) ; it is not of a glutinous, adhesive
nature, and hence maize flour or meal wiU not make a dough, or fer-
mented bread. It is prepared in several forms. Its composition is
given as follows :

Maize (Payen), Yellow Maize (Fosgxilb),

Starch fi7"55 Nitrogenous matters 9-905

Gluten or zea 12-50 Starch, dextrin, sugar 64-535

Dextrin or gum 4-00 Fatty matter 6-6S0

Fatty matter 8-80 Lignin and coloring matter 8-968

Celulose 5-90 Mineral 1-440

Saltscrashes 1-25 Water 13-472

100-00

HoESFOED obtained 13*65 of nitrogenous matter from maize meal, and
14'66 from maize grain. Samp is Indian corn divested of its outside
skin or bran, and of its germinal eye, the grain being left whole or
nearly so. In Tiominy each grain is broken up into a number of small-
er pieces. The meal of Indian corn, in consequence of its excess of
oily matter, attracts much oxygen from the air, and is hence very
prone to change, and does not keep well. This is the serious draw-
back of this most valuable grain ; though cheap, nutritive and health-
ful, it is difficult to transport and preserve its meal, especially in warm
seasons or climates.

449, Oats. — This grain is not employed to any considerable extent
as an article of diet for man, in this country. The oat varies greatly
in weight, ranging from 30 to 40 lbs. per bushel. In grinding, 30 lbs.
give 16 of meal and 14 of husk, while a bushel weighing 40 lbs. yields
23 lbs, 6 oz. of meal and 16 lbs. 10 oz. of husk — the largest proportion
of bran yielded by any grain, yet different varieties give different re-
sults. Oat flour stands before all other grains in point of nutritive or
flesh-producing power, being first in its proportion of the nitrogen-
ous element. It is also distinguished by its large quantity of fat or
oil, ranging in this particular next to Indian corn. The following
table gives the result of an analysis of Prench oats, by Boussingaitlt,
and the average of four samples of Scotch oats, by Prof. Norton.

240 GENERAL PKOPEBTIES OP ALIMENTAET SUBSTANCES.

(Boussingault). (Noktou).

starch 46-1 Starch 65-10

Sugar 6-0 Sugar 2-49

Gum 8-S Gum 2-22

Oil 6-7 Oil 6-55

ATenin.. \ Avenin 16-50

Albumen I 13-7 Albumen, 1-42

Gluten . . ) Gluten 1-67

Husk, ash, and loss 23-7 Epidermis 2-17

Alkaline, salt, and loss 1-84

100-0

99-96

Noeton's analysis, the most accurate we have, thus gives 19*59 per
cent, of nitrogenous compounds. Again, from nine samples of dry
oats he obtained 16"96 per cent, of protein compounds, the specimens
ranging from 14 to 22 per cent. Prof. Hoesfoed obtained from three
samples an average of 12-83 per cent, water, and 16*59 protein con-
stituents. From the dried grain he got 21*5 per cent, of these com-
pounds. If oatmeal be mixed with water, it does not form a dough
like wheat flour, and if it be washed upon a sieve, nearly the whole
will be carried through, only the coarse parts of the meal remaining
behind. The chief portion of the nitrogenized matter of the oat re-
sembles casein more than gluten, and has received the name of avenin
(from avena, the oat). Oatmeal, the ground and sifted flour of the
grain, is not so white as wheaten flour, and has a somewhat bitterish
taste. Under the husk of the oat there is a thin cuticle or integu-
ment, surrounding the central part, which is ground up with the meal,
and not being sifted out, gives it a rough and harsh taste, and although
the oatmeal gruel be strained, still a quantity of the sharp fragments
of cuticle escape through the strainer. Grits, or groats, are oats in
which the outer husk and cuticle are ground off and removed, so that
grit gruel is 'smoother,' as it is termed. It is chiefly made into
cakes, porridge, and gruel.

450. Barley. — The composition of barley is represented as follows :

Fine Barley Meal (Johnston). Barley (Poggaile), later.

Starch 68 Nitrogenous matters 10-655

Fatty matter 2 Starch and dextrin 60-330

Gluten, albumen, &c 14 Fatty matters 2-384

Water 14 Lignin 8779

Ash 2 Mineral substances 2-623

Water 15-229

100

Einhof's analysis represents it as containing 4*62 of gum and 5*21 of
sugar. Its husk or bran forms from 10 to 18 per cent, of its weight.

GRAINS — ^LEGUMINOUS SEEDS. 241

The composition of barley has not been very carefully examined. It
is reported to contain a good share of nitrogenous matter, but of what
nature is not known. It is deficient in true gluten and behaves like
oatmeal when washed with water. When stripped of its husk or
outer skin by a mill, it is called Tiulled or pot-larleij^ and is used for
making broth. After a considerable portion more of the kernel has been
ground off", the rounded and polished grains are known as pearl-iarley.

451. Rice is remarkable for being richest in starch and most de-
ficient in oil of all the cultivated grains. Its flesh -producing elements
are low, much lower than wheat or Indian com, and less than half
that of oats. Analysis gives the following results :

Rice (Paten). Rice (Poggaile).

Starch 86-T Starch, dextrin, sugar T4-4T0

Gluten, &c 7'5 Nitrogenous matters T-SOO

Fatty matter 0'8 Fatty matters 2-235

Sugar and gum 0'5 Mineral -SZS

Epidermis (skin) 3'4 Lignin 3-345

Saline matter (ash) 0-9 "Water lT-730

Prof. Johnston found five varieties to contain an average of 13"4 per
cent, of water and but •41, that is less than half of one per cent, of
ash. Mr. Hoesfoed separated from some rice 15 "14 per cent, of water,
and 6'27 per cent, of nitrogenous matter in its ordinary state, and 7.4
per cent, in its dry state. It is usually presented to us in market
hulled, or freed from its husk, and is used whole, being but rarely
ground into flour.

452. Buckwheat. — The composition of this grain has not been satis-
factorily elucidated; there remains considerable discrepancy in the
results of its analysis. Zenneok found that in the dry state it con-
sisted of —

Husk 26-9

Gluten, &c 10-7

Starch 52-3

Sugar and gum 8-3

Fatty matter 0-4

The gluten is here supposed to be estimated too high. Hoesfoed ob-
tained from buckwheat flour in the natural state (that is, not dried) :

"Water 15-12

Starch 65-05

Protein 584

B.— liCg-iiininous Seeds.

453. Composition of Peas.— Seeds obtained from pods are called
leguminom. Of this class we are only concerned with peas and

11

242 GENEEAL PBOPEETTES OF ALIMENTAEY SUBSTANCES.

beans. They resemble much in composition the cereal grains, but are
more highly nutritive ; indeed, they afford the most concentrated form
of vegetable nourishment. The roasted cMclc-pea of the East is con-
sidered to be more capable of sustaining life, weight for weight, than
any other kind of food ; hence, it is preferred by travellers about to
cross the deserts, as the least bulky and heavy form of diet. Accord-
ing to HoESFOED and Keookee :

A Table Pea yielded : A Field Pea gave !

Albumen and casein 28-03 Albumen and casein 29-18

Starch 88-81 Starch 66-23

Gum 28-50 Gum 66-23

Skin 7-65 Skin 6-11

Ash 8-18 Ash 2-79

According to PooaAiLE, field peas that had been deprived of 9*50 of
envelope, contained :

Nitrogenous matters 21-670

Starch, dextrin, and sugar 57-650

Fatty matters 1-920

Lignin 8-218

Mineral 2-802

Water 12-740

He found also in very soft green peas :

Nitrogenous matters 38-35

Older than the above 34-17

Eipened 27-72

Prof. Johnston states that the proportion of nitrogenous, or flesh-
forming matter, in both peas and beans, is on an average about 24 per
cent., and of oil about two per cent. The nitrogenous element of
peas and beans is not glutinous, and consists chiefly of vegetable
casein. They are hence incapable of making bread. From their
high proportion of nitrogenous constituents, peas and beans are ex-
tremely nutritious, ranking first among concentrated strength-impart-
ing foods. They are considered difficult of digestion, and of a con-
stipating quality, which requires to be corrected by admixture with
other kinds of food. The varieties are numerous, with wide differen-
ences of flavor and softness when cooked, and they probably differ
equally in composition. "We have before stated, that in consequence
of its fibundance of casein, the Chinese make it up into a kind of
vegetable cheese (424).

454. Composition of Beans. — The composition of beans varies but
little from that of peas. The authorities above cited (Hoesfoed and
Keookkr) give tbe following results ;

LEGFUMINOUS SEEDS — FRUITS. 243

Beans (Hoksfoed and Keockek). Table Bean. Large White Bean.

Vegetable casein and albumen 2S-54 29-31

Starcb ST-50 66-lT

Gum 29-20 66-lT

Skin 4-11 4-41

Ash 4-38 4-01

The peas and beans in this analysis were dried at 212°, and lost an
average of 15.53 per cent, of moisture.

455. Bone-prodacittg material in Peas and Beans. — By reference to the
preceding analytical results, it wUl be seen that the ash, or mineral
constituents of peas and beans, from which the earthy part of bones
is derived, is considerable, but larger in beans than in peas.

Will and Fkesinids' analyses of the ash o£ Three analyses of the ash of beans gave the
peas gave : following average result :

Potash 89-51 Potash 29-62

Soda 3-98 Soda 13-31

Lime 5-91 Lime 6-11

Magnesia 6-48 Magnesia 8-95

Oxide of iron 1-05 Oxide of iron 0-98

Phosphoric acid 34-50 Phosphoric acid 4-84

Common salt 3-Tl Chlorine 1*18

Sulphuric acid 4-91 Sulphuric acid 1-43

Silica 5-34

C— Fruits.

456. Their General Composition. — Although fruits are extensively
used as articles of diet, yet as staple sources of nutrition they bear no
comparison to the grains. They consist of pulpy masses, which are
nearly all water, and are prized far more for those properties which
relate them to the taste than for nourishing or strengthening power.
They generally consist of from 75 to 95 per cent, water, from 1 to 15
or 20 per cent, fruit sugar, organic acids in variable proportions (414)
in combination chiefly with lime and potash, pectiae, or the jelly-
producing principle, ligneous skins and cores, with peculiar aromatic
and coloring principles of infinite shades of diversity. The unripe
fruits contain a larger proportion of water and acid, and a less amount
of sugar than the natural fruits. As they contain so great a proportion
of watery juices, they are very prone to change, and thus exhibit little
constancy of composition. From this circumstance, and the number-
less varieties of fruits that are catalogued, and also from the fact that
comparatively little attention has been given to this branch of organic
chemistry, our knowledge of the exact composition of fruits is very
imperfect.

457. Composition of Apples.— Every one will understand that the

244 GENERAL PBOPEI^IES OP AUMENTAHY STIBSTAIirCES.

various sorts of apples differ mucli in composition, yet in an average
condition 100 lbs. of fresh apples contain about 3-2 lbs. of fibre, 0*2
lbs. of gluten, fat, and wax, 016 of casein, 1-4 of albumen, 3-1 of
dextrine, 8-3 of sugar, 0-3 of malic acid, 82-66 of water. Besides the
above mentioned bodies, the apple contains a small quantity of tannic
and gallic acid — ^most in the russets. To these acids apples owe their
astringency of taste, and the blackening iron or steel instruments used
to cut them. The following is the proportion of water and dry matter
in several varieties of apples, according to Sallsbuey's examination.

Talman Sweeting.

Greening.

Swarr Apple.

Roxbury Russet.

Englisli Ruaaet.

Water 81-52

82-85

84-75

81-35

79-21

Dry Matter.. 18.48

lT-15

15-25

18-65

20-79

Muskmelon.

Cucumber.

90-98

96-36

9-01

3-63

The percentage of ash in the apple is small, yet it is rich in phosphoric
and sulphuric acids, potash, and soda. The proportions of water and
dry matter have also been determined in the following substances :

Watermelon.

Water 94-89

Dry Matter 5-10

The dry matter of melons contains quite a large percentage of albumen,
casein, sugar, and dextrin, with a small quantity of acid.

©.— Licaves, JLeaf-Stalks^ &c.

458. Many kinds of leaves abound in principles adapted for animal
nutrition, as is shown by the extent to which cattle are grown, sus-
tained and fattened upon the grasses, Man makes use of leaves in his
diet to but a limited extent. Professor Johnston remarks, "leaves
are generally rich in gluten ; many of them, however, contain other
substances in smaller quantity associated with the gluten, which are
unpleasant to the taste, or act injuriously upon the general health, and
therefore render them unfit for human food. Dried tea-leaves, for
example, contain about 25 per cent, of gluten ; and therefore if they
could be eaten with relish and digested readily, they would prove as
strengthening as beans or peas."

459. The Cabbage. — The same authority says of this vegetable : " It
is especially nutritious. The dried leaf contains, according to my
analysis, from thirty to thirty-five per cent, of gluten ; and is in this
respect, therefore, more nutritious than any other vegetable food
which is consumed to a large extent by men and animals. I know,
indeed, of only two exceptions, — the mushroom, which in its dry mat-
ter contains sometimes as much as 56 per cent, of gluten, and the
dried cauliflower in which the gluten rises, as high as 64 per cent."

LEAVES, LEAP-STALKS, ROOTS, ETC. 245

The cabbage and cauliflower lose in drying more than 90 per cent, of
water ; and the dried residue, according to Peeeiea, is remarkably-
rich in sulphur as well as nitrogen. The plant decays quickly, and
gives out a strong odor of putrefaction, owing to its nitrogenous and
sulphurous compounds. Decayed cabbage leaves should therefore
not be allowed to remain in cellars, or lie about in the vicinity of
dwellings.

460. Lcttnco Leaves are much used at table as a salad. The young
leaves contain a bland, cooling juice ; but as the plant advances, its
milky juice becomes bitter, and is found to contain opium. In this
stage it has a slight tendency to promote sleep. The water-cress^ leaves
of white mustard and of common cress, probably owe their pungency
to a minute portion of sulphurized volatile oil, analogous to that found
in horseradish. The stalks of many kinds of leaves, as spinach,
turnip-tops, potato-tops, cowslips, &c., are used as greens, but their
peculiar characters have not been ascertained. The stalks of rhubarh,
used for pies, puddings, &c., like apples and gooseberries, contain
much malic and oxalic acid in combination with lime and potash.
The proportion of water, dry matter, and ash, in the rhubarb stalk,
celery, and vegetable oyster, is as follows :

Rhubarb Stalks. Celery. Vegetable Oyster.

■Water 89-50 88-22 84-46

Dry Matter 10-50 11-77 15-54

Ash 1-13

Half the dry matter consists of malic, tartaric, and oxalic acids, with
fibre, sugar, albumen, and casein.

£.— Roots, Tubers, Bulbs and Sboots.

461. Composition of Potatoes — Wsiter. — This is the most widely culti-
vated and important for dietetical purposes of aU the root tribe, and
has been more carefully examined than any other. Like fruits and
leaves its leading constituent is water, which composes about three-
quarters of its weight. Young, unripe potatoes contain more water
than those fully grown, and it has been found that the ' rose ' end of
the potato, or that part from which the young shoots spring, contains
more water than the ' heel ' or part by which it is attached to the
rootlet. KoETE examined 55 varieties of potato and found them to
contain 75 per cent, of water and 25 of solid matter. Professor
Johnston gathered from 27 analyses made in his laboratory tlie fol-
lowing results. Greatest proportion of water in young potatoes, 82
per cent. ; largest proportion in fuU grown potatoes, 68"6 per cent.

246 GENERAL PEOPEETIES OF ALIMENTAEY SUBSTANCES.

He gives the mean of 51 determinations upon potatoes of all ages — as
water 76 per cent, dry matter 24.

462. Starch in Potatoes. — A large part of the solid matter in potatoes
consists of starch. Johnston states as the results of numerous expe-
riments, that the proportion is in the natural state 64-20 per cent.
Siemens ascertained the proportion of starch in 66 varieties to range
between 19'25 and 11*16 per cent. ; the average being 15'98. These
proportions, however, vary with the kind of potato, soil, season,
and other circumstances. The heel end usually contains more starch
than the rose end. The weight of potatoes and their proportion of
starch diminishes by keeping. Paten found the same variety to yield
of starch in

October 17'2 per cent. February 15"2 per cent.

Kovember 16-8 " March 15 "

December 15-6 " April 14-5 "

January 15'5

Other experiments would seem to show that there is rather an increase
after digging ; but aU examinations agree, that as vegetation becomes
active in the spring, the buds begin to grow at the expense of the
starch contained in the tuber, and hence at this season potatoes are
less mealy, and not so much esteemed for table use.

463. Flesh-prodacing constituents of Potatoes. — The potato contains a
considerable proportion of nitrogenous matter in the threefold form
of albumen, casein, and gluten, as it exists in the grains. They exist
dissolved in its juices. There is more of the casein than of the other
elements. Johnston gives the average of these constituents at l-4th
per cent, in the natural state, and 5-8th.per cent, when freed from
water. But he acknowledges his mode of separating them to be liable
to error, so that the figures are probably too low. Hoesfoed, by a
more accurate method, found the percentage of these compounds
in the dry matter of potatoes to be — in white potatoes 9 "9 6 per
cent., in blue 7*66 per cent. He found also that not only is the pro-
portion different in different varieties, but that it is greater in young
potatoes than in old ; and Botjssingaxjlt also found the proportion of
the protein compounds to diminish the longer the potato is kept.

464. Woody Fibre, Sugar, Gum. — The proportion of fibre in the
potato varies from 1\ to 10 per cent., and may be said to average
about 3. The fatty matter is also variable, but may be stated at about
1 per cent. Sugar in the natural state about 3 '3, gum 0"55, or in the
dry condition, sugar 1347, gum 2 "25.

465. Average Composition of Solid or Dry Matter of Potato. — This is
summed up by Professor Johnston in round numbers as follows :

THE POTATO AND ONION. 247

etarch 64

Sugar and gum 15

Protein compounds e 9

Fat 1

Fibre 11

Total 100

The dry potato, therefore, is about equal iu nutritive value to rice, and
is not far behind the average of our finer varieties of wheaten flour.
The juice of potatoes is acid ; it was fornaerly supposed to contain
citric acid, but it is now ascertained to be due to malic acid, and per-
haps the sulphuric and phosphoric found in the ash. Potatoes also
contain a small portion of asparagin, the peculiar principle of asparagus.
When potatoes are freed from their large excess of water, so as to
bring them into just comparison with the grains in composition, they
are found to contain quite a large percentage of mineral matter left as
ash — the average of six determinations giving 3 '92 per cent. The
constituents of these six samples give an average as foUows :

Potash 5575

Soda 1-86

Magnesia 5*28

Lime ,... 207

Phosphoric acid 12-57

Sulphuric acid 13-64

Silica 4-23

Peroxide of iron 0-52

Common salt » 7-01

The carbonic acid, which was from 6 to 12 per cent., was deducted.
The mineral matter of the potato seems to be thus distinguished from
that of the grains by its large proportion of potash, sulphuric acid,
and common salt, and its lesser quantity of phosphoric acid and mag-
nesia.

466. The Onion,' — This bulbous root abounds in nitrogenous matter;
when dried, it has been found to yield from 25 to 30 per cent. It
is therefore highly nutritive. It contains a strong-smelling sulphur-
ized oU, the same tliat gives its powerful odor to the garlic. The con-
stituents of the onion are thus stated by Peeeiea :

VolatUe oil, Woody fibre,

Uncrystallizable sugar, Pectic and phosphoric acid,

G-um, Phosphate and carbonate of lime,

Vegetable albumen, Iron.

467. Beets, — The varieties of beets of course differ in composition,
but they all contain much sugar. Their nutritive qualities are not
well determined. Beetroot is represented as containing 81 per cent

248 GENEEAL PEOPEKnES OP ALIMENTARY SUBSTANCES.

of water, 10"20 of sugar, and 2'03 of nitrogenous matter. In tlie long
blood-beet tbere is 89"09 per cent, of water, and 10"90 of dry matter.
468. Turnips, Carrots, ParsnipSi — Chemistry has hitherto cast but
an uncertain light upon the composition of this class of substances. It
appears from the best determinations, that the proportion of solid mat-
ter in several roots is as follows :

White Turnips lOJ

Yellow do IBi

Mangel-wurzel 15

Carrot 14

The dry substance of these roots is much lower than that of the pota-
to, which ranges at 25 per cent. Yet the flesh-forming constituents
of dried turnips much exceed those of the potato, as the following com-
parison shows.

Protein Compounds.

The dried potato 8 per cent.

Yellow turnip 9J do.

Mangel-wurzel l&J do.

The nitrogenous matter of di'ied mangel-wurzel being nearly twice
as great as in the dried potato. In the carrot the proportion of water
is 85 "YB, and dry jnatter 14'22. According to Oeome, the parsnip
contains —

starch 1-8

Albumen 21

Gum 61

Sugar 5'5

Fibre 51

Water T9-4

Total lOO'OO

4. CoMPOTiN"D Aliments — Animal Food.
A.— Constituents of WLea,t.

469. — ^Various parts of animal bodies contribute materials for diet ;
the flesh and fat chiefly, but nearly aU other portions, blood, intestines,
membranes, bones, and skin, more or less. The staple constituents
of animal food are fibrin, albumen, gelatin, fat, salts, and water, and
in the case of milk, casein and sugar.

470. Composition of Flcsh-mcat.— This is generally unders'^ood to sig-
nify the muscular or lean parts of cattle, surrounded by fat, and con-
taining more or less bone. The muscles consist of fibrin ; they are
separated into bundles by membranes, and into larger separate masses
by cellular tissues, in which fat is deposited. The fleshy mass is pene-

CONSTrrUENTS OF MEAT. 249

trated by a network of blood-vessels and nerves, and the whole is dis-
tended by water, which composes about three-fourths of the weight
of the meat. The composition of the muscular flesh of different ani-
mals, according to Mr. Beande, is as follows :

Water. Albumen and Fibrin. Gelatin. Total solid matter.

Beef 74 20 6 26

Veal 75 19 6 25

Mutton 71 22 T 29

Pork 76 19 5 24

Chicken 73 20 T 27

Cod 79 14 7 21

These results give an average of very nearly 75 per cent, water.
LiEBiG assumes it at T4, with 26 per cent, of dry matter. The ratio of
water in meat, fowl, and fish, is quite uniform, ranging from YO to 80
per cent., but the proportion of the other constituents, muscular fibre,
fat, and bone, exhibits the widest possible diversity. In some animals,
more especially wild ones, as deer, &c., there may be hardly a traco
of oily matter, whUe swine are often fed until the animal becomes one
morbid and unwieldy mass of fat. The pure muscular flesh of ordi-
nary meat, with aU its visible fat separated, is assumed by Knapp and
LiEBiG to contain still about 8 per cent, of fat. In beef and mutton,
such as is met with in our markets, from a third to a fourth of the
whole dead weight generally consists of fat. — (Johnston.)

471. Juice of Flesh. — The true color of the fibrin of meat is white,
yet flesh is most commonly of a reddish color (flesh-color). This is due
to a certain portion of the coloring matter of the blood, by which it is
stained. Yet the liquid of meat is not blood ; when that has been
withdrawn from the animal, and the blood-vessels are empty, there
remains diffused through the muscular mass a peculiar liquid, known
as the juice of flesh. It consists of the water of flesh, containing about
5 per cent, of dissolved substances, one-half of which is albumen, and
tlie other half is composed of several compounds, not yet examined.
The juice of flesh may be separated by finely mincing the meat, soak-
ing it in water, and pressing it. The solid residue which remains after
all the soluble matter has been thus removed, is tasteless, inodorous,
and white like fish. The separated juice is uniformly and strongly
acid, from the presence of lactic and phoshporic acids, hence it is in
the opposite state to that of the blood, which is invariably alkaline.
The juice of flesh contains the savory principles which give taste to
meat, and which cause it to differ in different animals. It also con-
tains two remarkable substances, called Tcreatine and Tcreatinine^ nitro-
genous compounds, which may be crystallized. The quantity yielded

11*

250 GENERAL PEOPEETIES OF AUMENTARY STTBSTANCES.

is variable in different kinds of flesh, but in all is extremely small.
Kreatine is a neutral or indifferent substance, wbile kreatinine is a
powerful organic base, of a similar nature witb tbeine and cafeine of tea
and coffee.

472. Blood, Bones, and Internal Organs. — ^The leading constituents of
blood are the same as flesh ; it contains only some three per cent, more
of water. Its nitrogenous matter, however, is chiefly liquid albu-
men. Blood has been called liquid flesh, and flesh sohdified blood.
About half the weight of bones is mineral matter, lime combined
with phosphoric acid, forming phosphate of lime — ^the substance that
we have seen to abound so greatly in the ash of grains. The other
half of bones is gelatm, the thickening principle of .soups (glue). It
is sometimes partially extracted for this purpose by boiling. Marrow
is a fatty substance, enclosed in very fine cellular tissue within the
bone. Skin, cartUage, and membrane, yield much gelatin. The
tongue and heart are muscular organs, agreeing in dietetical proper-
ties with lean flesh. Beacoonnot's analysis of the liver gives 68 per
cent, of water, and 26 of nitrogenous matter; it also contains oU.
The Irain is a nervous mass, containing 80 per cent, water, some al-
bumen, and much of a peculiar phosphoric oily acid. The stomacM
of ruminating animals which yield tripe, are principally composed of
fibrin, albumen, and water.

473. Composition of Eggs. — The eggshell is a compound of lime, not
the phosphate as exists in bones, but chiefly carbonate of lime. It is
porous, so as to admit of air for the wants of the young animal in
hatching, and usually weighs about one-tenth of the entire egg. The
white of egg consists of water containing 15 or 20 per cent, of albumen.
The yolk is water and albumen, but contains, also, a large proportion
(two-thirds of the dried yolk) of a bright yellow oil, containing sulphur
and phosphoric compounds. A common-sized hen's-egg weighs about
a thousand grains, of which the shell weighs 100, the white 600, and
the yolk 300. The composition of its contents is :

Water 74

Albumen 14

Fat 10-5

Ash (salts) 1-5

Total 100

B.— Production and Composition of Milk.

474. What it Contains. — This familiar liquid consists of oil or butter,
sugar, casein or the cheesy principle, and salts, with a large proportion
of water. The sugar, casein, and salts are dissolved in the water.

PEODUCTTON AND COMPOSITION OF MILK. 251

while the butter is not, hut exists diffused through the Kquid in the
form of numberless extremely minute globules. They cannot be seen
by the naked eye. "When the liglit falls upon them they diffuse it in
aU directions, so that the mass appear opaque and white. Viewed
by a microscope, the globules appear floating in a transparent liquid.
In respect of its sugar, casein, and salts, milk is a solution; but with
reference to its oily part, it is an emulsion. It is heavier than water
in the proportion of about 103 to 100, although it differs considerably
in specific gravity. When first drawn it is slightly alkaline and has a
sweetish taste, which is due to the sugar of milk.

475. Proportion of its Elements. — This is variable. It generally con-
tains about 86 per cent, water, 4 to 7 of casein, 3 "5 to 5 '5 of butter,
and 3 to 5-5 of sugar of milk and salts. The following are analyses
by Henet and Ohevaliee :

Cow. Woman.

Casein 4-4S 1-52

Butter 313 8-55

Milksugar 4-47 6-50

Salts -60 0-45

Water 8T-02 8T-98

The following are Hadlein's results : — The second column is thai
average of two analyses.

Cow's Milk, Woman's Milk.*

Butter 8 2-351

Sugar of milk and salts soluble In alcohol 4-6 8.75

Casein and insoluble salts 5-1 2-90

Water 87-3 90-50

476. Circnmstances Influencing the Quality of Milk. — ^Both the quantity
and quahty of milk are influenced by various conditions apper-
taining to the animal. Its food exerts a powerful control in this
respect. Green succulent food is more favorable to the production of
milk than dry, and E. D. Thomson's experiments go to show that of
dry food, the richest in nitrogenous matter best promotes the milk
secretion. Platfaie was led, by his brief experiments, to conclude
that food low in nitrogenous matters (as potatoes) yielded a large
quantity of milk which was rich in butter, and that quiet {stall feed^
ing) had the same effect, whilst cows grazing in the open air upon
poor pasture, and consequently obliged to take much exercise, yielded

* The milk of -women from 15 to 20 years of age, contains more solid constituents
than of women bet-ween 30 and 40. Women with dark hair also give a richer milk than
-women with light hair. In acute diseases the sugar decreases one-fourth, and the curd
increases one-fourth ; -while in chronic affections the butter increases one-fourth, and
the casein slightly diminishes. In both classes of diseases the proportion of saline matter
diminishes. — (Johnston.)

252 GENEEAL PROPEETEES OP ALIMENTARY SUBSTANCES.

milk rich in casein. It appeared from Thomson's observations, that
the produce of miLk of a cow, with uniform diet, gradually diminished,
and increased again by a change of diet. It is well known that a cow
fed upon one pasture will yield more cheese, while upon another it
will give more butter. Hence the practice in dairy districts of al-
lowing the animal to roam over a wide extent of pasture to seek out
for itself the kind of herbage necessary to the production of the richest
mUk ; hence, also, the propriety of adding artificial food to that de-
rived from grazing. Plants and weeds found scattered in many
pastures are apt to affect, injuriously, the quality and taste of the milk.
Butter is especially liable to be deteriorated in this way. An observ-
ing dairy -manager remarks as follows : " If a cow be fed on ruta-baga,
her butter and milk partake of that flavor. If she feeds on pastures
where leeks, garlicks, and wUd onions gi-ow, there wUl be a still more
offensive flavor. If she feeds in pastures where she can get a bite of
brier leaves, beech or apple-tree leaves, or any thing of the kind, it
injuriously affects the flavor of the butter though not to the same
extent, and would scarcely be perceptible for immediate use. So
with red clover. Butter made from cows fed on red clover is good
when first made, but when laid down in packages, six months or a
year, it seems to have lost all its flavor, and generally becomes more
or less rancid as the clover on which the cow fed was of rank and
rapid growth." — (A. B. Dickinson.)

477. Distance from the time of calving. — The colostrum^ or first milk
which the cow gi^es for several days after the birth of her young,
differs from normal mUk. Geegory states that it contains from 15 to
25 per cent, of albumen, with less casein, butter, and sugar of milk
A much larger quantity of milk is yielded in the first two month?
after calving, than at the subsequent periods ; the decrease is stated
as follows, according to Atton :

Quarts per day, Qimrta.

. First 50 days 24 or in all 1200

Second "

Third "

Fourth "

Fifth "

Sixth "

and at the end of ten months, they become nearly or altogether dry.

478. Time of year, age and condition of the animal. — In spring, milk is
finest and most abundant. Moist and temperate climates and seasons
are favorable to its production. In dry seasons the quantity is less,
but the quality is richer. Sprengel states that cool weather favors
the production of cheese and sugar in the milk, while hot weather

20 "

" 1000

14 "

" 700

8 "

" 400

8 "

" 400

6 "

" 800

PKODUCTION AND COMPOSITION OP MILK. 253

increases the product of butter. The poorer the apparent condi-
tion of the cow, good food being given, the richer, in general, is the
milk ; but it becomes sensibly poorer when she shows a tendency to
fatten, A state of comparative repose is favorable to all the impor-
tant functions of a healthy animal. Any thing which frets, disturbs,
torments, or renders her uneasy, affects these functions, and among
other results, lessens the quantity, or changes the quahty of the mUk.
Such is observed to be the case when the cow has been newly de-
prived of her calf — when she is taken from her companions in the
pasture-field — when her usual place in the cow-house is changed —
when she is kept long in the stall after spring has arrived — when she
is hunted in the field, or tormented by insects, or when any other
circumstance occurs by which irritation or restlessness is caused,
either of a temporary or of a permanent character. — (JoffisrsTow.)

479. Prodaction and Composition of Cream. — "We have stated that
butter exists in mUk, as a fatty emulsion ; that is, not dissolved, but
floating as exceedingly minute globules throughout the watery mass.
These butter globules are lighter than water, and hence, when the
milk is suffered to stand undisturbed, they slowly rise to the sur-
face, forming cream. The oil-globules of cream do not coalesce or
run together, they are always separated from each other, and sur-
rounded by the soluble ingredients of milk ; while at the same time,
the body of the milk never becomes perfectly clear by the complete
separation of these globules. Hence, cream may be viewed as milk
rich ia butter, and skimmed milk as containing little butter. It is
supposed by some, that the butter particles are in some way invested
or enclosed with casein ; at all events, a quantity of cheesy matter
rises with the oU-globules. Its proportion in cream depends upon the
richness of the milk, and upon the temperature at which it is kept
during the rising of the cream. In cool weather, the fatty matter will
bring up with it a larger quantity of the curd, and form a thicker cream.

480. Conditions of tlie Formation of Cream. — The globules of butter
being extremely minute, and but slightly lighter than the surround-
ing liquid, which is at the same time somewhat viscid or thick, they
of course ascend but slowly to the surface. The larger globules of
butter, which rise with greater ease, mount first to the surface. If
the first layer of cream, consisting of these largest particles, be taken
off after 6 or 12 hours, it affords a richer, fresher, and more palatable
butter than if collected after 24 or 30 hom-s standing. Milk is, there-
fore, sometimes skimmed twice, and made to yield two quahties of but-
ter. The deeper the milk, the greater the difficulty with which the

S54 GENERAL PEOPEKTIES OP ALIMENTARY SUBSTANCES.

oily matter ascends througli it ; hence, it is customary to set the milk
aside in shallow pans, so that it may not he more than two or three
inches in depth ; hence, if it is desired to prevent the formation of cream,
the milk should be kept in deep vessels. Temperature powerfully in-
fluences the formation of cream, or the rapidity with which it rises.
Heat, by increasing the thinness and limpidity of the liquid, and the
lightness of the oil-globules, favors their ready ascent ; while cold, by
thickening the liquid, and solidifying the oU, greatly retards their sepa-
ration. Hence it is said, that fi-om the same milk an equal quantity of
cream may be extracted, in a much shorter time during warm than dur-
ing cold weather ; that, for example, mUk may be perfectly creamed

In 36 hours when the temperature of the air is 50° F.

"24 " " " 55°

" 18 to 20 " " " 68°

" 10 to 12 " " " 7r

while at a temperature of 34° to 37° (two to five degrees above freez-
ing), milk may be kept for three weeks, without throwing up any
notable quantity of cream. — (Speengel.)

481. Blilk Creams before it is taken from the Cow, — This spontaneous
tendency of milk to separate itself mechanically into two sorts or
qualities, explains the remarkable difference in the richness of milk
withdrawn at different stages of the milking process. The glands in
the teats of the animals, which secrete the milk, are vessels interlaced
with each other in such a way as to form hoUow spaces or -reservoirs
which distend as the milk is secreted. In these reservoirs the same
thing takes place as occurs in an open vessel, and with still more
facility as the temperature is up to blood heat (98°) — the rich creamy
portion rises above, while the poorer milk falls below. Hence that
which is first drawn is of an inferior quality, while that which is last
drawn, the strippings or afterings^ abounds in cream. Professor An-
DEESON states, that compared with the first milk the same measure of
the last will give at least eight, and often sixteen times as much cream.
The later experiments of Reiset show, that where the milkings are 11
or 12 hours apart, the quantity of butter in the last drawn milk is
from three to twelve times greater than that obtained from the first
drawn milk. Where the milkings were more often, the difference
became less. As milk before being taken from the cow is already
partially separated — its richer from its poorer parts — the dairy man-
ager should take advantage of tliis circumstance, and not commingle
in the same vessel the already half-creamed milk, if the object is the
separation of butter. It has been shown that more cream is obtained

PEODUCnON AND COMPOSITION OF MILK.

255

3

by keeping the milk in separate portions as it is drawn, and setting

these aside to throw np their cream in separate vessels, than when

the whole milking is mixed together. Moreover, the intimate mixture

of the richer and poorer portions not only reduces the fig. 96.

quantity of cream that may be separated, but much delays

the operation which, in hot weather, when mUk soon

sours, is objectionable. ^=^ltp

482. Determining the valne of Milk. — Its value is propor-
tional to the amount of its solid alimentary constituents,
and is liable to variation, according to circumstances. If
butter is to be manufactured from it, that is most valuable
which contains most oily matter ; if cheese is desired,
then that which contains most casein. Milk is heavier
than water, and the richer it is the heaver it is ; hence it
has been attempted to make the latter quality a guide
to the former. Its weight compared with water, or spe-
cific gravity^ is determined by the hydrometer (Tig. 96). A A —
tin or glass cylinder is filled with milk to be tested, and —
the hydrometer, a glass bulb with a stem above, is placed ^ ''**™^ °'"'
in it ; the lighter the milk, the deeper it sinks ; the heavier it is, the
higher it floats. A scale is marked upon
the stem, which indicates at once how
far the weight of the mUk rises above
pure water. Yet the results of the instru-
ment are to be received with caution.
Milks, though pure, differ naturally in
specific gravity ; while it is easy to add
adulterating substances that shall in-
crease their weight, thus causing the (^M^^s. J [^T

hydrometer to report them rich. Yet
as giving an important indication it has
value, and with experience and judgment,
may be made useful.* An instrument
called the lactometer (milk measurer)
has been used to determine the propor-
tion of cream. It consists of a glass
tube ten or twelve inches long, marked

off and numbered into a hundred spaces. [ --all ""^^ ^ -Jl

The tube being filled with milk to the \^

top space, is suffered to stand until the Lactometer.

Fig. 97.

* Made by Tagliabcte, of Now York,

256 CUUNAET CHANGES OP ALIMENTABT SUBSTANCES.

cream rises to the surface, when its per cent, proportion is at once
seen. It will answer if only the upper portion of the tube be marked
as shown in Fig. 97. The percentage of cream, that is, the thickness
of its stratum at the top of the tube, varies considerably. "We have
found the average to be 8|- per cent., although samples are liable to
range much above and below this number.* If the milk has been
mixed, say with one-third water, the cream will fall to 6, if with one-
half, it may fall to 5 per cent.

483. Mineral Matter in Milk. — The proportion of salts in mUk
averages about half per cent. ; that is, 200 lbs. when dried and burned
will yield 1 lb. of ash. The composition of this ash is shown by the
analysis of Haidlein, who obtained from 1000 lbs. of milk

1 s

Phosphate of lime 2-31 lbs. 8-44 lbs.

Phosphate of magnesia 0'42 " 0"64 "

Phosphate of peroxide of iron 007 " O'OT "

Chloride of potassium 1-44 " 1-83 "

Chloride of sodium 0-24 " 0-34 "

Free soda 0-42 " 0-45 "

Total 4-90 6-T7

III.— CULINAKY CHANGES OP ALIMENTARY SUBSTANCES.
1. Combining the Elements of Beead.

484. General Objects of Culinary Art. — We have seen that the ma-
terials employed as human food consist of various organized substances
derived from the vegetable and animal kingdoms, grains, roots, stalks,
leaves, flowers and fruit, with flesh, fat, milk, eggs, &c. &c. But few of
these substances are best adapted for food in the condition in which they
occur naturally. They are either too hard, too tough, insipid or injuri-
ous, and require to undergo various changes before they can be properly
digested. Most foods, therefore, must be subjected to processes of
manufacture or cookery before being eaten. In their culinary prep-
aration, numerous mechanical and chemical alterations are effect-
ed, in various ways; but the changes are chiefly wrought by means of
water and heat. "Water softens some substances, dissolves others, some-
times extracts injurious principles, and serves an important purpose
in bringing materials into such a relation that they may act chemically
upon each other. Heat, applied through the medium of water, or in va-
rious ways and degrees, is the chief agent of culinary transformations.
Another proper object of cooking is the preparation of palatable dishes,

* The number given by the lactometer will, from the nature of the case, be somewhat
under the truth, as the butter globules do not all ascend through the long column of milk.

COMBINTKrG THE ELEMEtJTS OF BREA.D. 257

from tlie crude, tasteless, or even offensive substances fumislied by
nature. This involves, not only the alterations produced by water and
heat, but the admixture of various sapid and flavoring ingredients,
■which increase the savory qualities of food. The cereal grains, con-
verted into flour and meal, are to be prepared for mastication, mixture
with the saliva, and stomach digestion. This end is best accomplished
by converting them into bread, while at the same time they assume a
portable and convenient form, and are capable of being preserved for
a considerable time. Bread is made, as is well known, by first incor-
porating water with the flour, and making it into dough, and then by
various means causing it to rise, that is, to expand into a light, spongy
mass, when, after being moulded into loaves, it is finally submitted to
the action of heat in an oven, or baked. "We shall consider the suc-
cessive steps of this important process, in the order of their occurrence ;
and as the flour of wheat is the staple article in this country for the
manufacture of bread, it wiU occupy our first and principal attention.
485. Water absorbed iu making Dongh. — The addition of laauch water
to fiour forms a thick liquid, called batter ; more flour admixed stiffens
it to a sticky paste, and still more worked through it produces a firm
dough. The water thus added to flour does not remain loosely associ-
ated with it, but enters into intimate combination with its constitu-
ents, forming a compound, and is not all evaporated or expelled by
the subsequent high heat of baking. In the dough, the liquid performs
its usual office of bringing the ingredients into that closer contact which
is favorable to chemical activity. As water is thus made to become a
permanent part of solid bread, it is important to understand in what
proportion, and under what conditions, its absorption takes place.
Baked bread that has been removed from the oven from 2 to 40 hours,
loses, by thorough drying at 220,° from 43 to 45 per cent, of its
weight, or an average of 44 per cent. If we assume the flour to con-
tain naturally 16 per cent, of water, 10^ lbs. of the 44 that was lost
belonged to the flour itself, while 33|- lbs. were artificially added m
making the dough. Thus —

Dryflo^r 56 )

Water in flour naturally lOJ j ^

Water added in baking 83^^

100

Ten pounds of flour would thus absorb 5 lbs. of water, and yield 15
lbs. of bread. The best flours absorb more water than those of infe-
rior quality. The amount with which they will combine is sup-
posed to depend upon the proportion of gluten. In dry seasons flour

258 CULINAET CHAITGES OP AUMENTAEY SUBSTANCES.

will bear more water than in wet, and a thorough process of kneading
will also cause the dough to absorb a larger quantity without becoming
the less stiff on that account. Certain substances added to flour aug-
ment its property of combining with water (521).

486. Effects of the Kneading Process. — The purpose of water inter-
mingled with flour is to combine with and hydrate the starch, to dis-
solve the sugar and albumen, and to moisten the minute particles of
dry gluten, so as to cause them to cement together, and thus bind the
whole into a coherent mass. But, as only a certain limited quantity
of water can be employed to produce these results, it is obvious that
it must be carefully and thoroughly worked throughout the flour — this
is called hieading the dough, and is generally performed with the
hands. The process is laborious, and attempts have been often made
to accomplish it by machinery, but hitherto without success. Flours
differ so much in their dough-making properties, that judgment is re-
quired in managing them. As the eye cannot penetrate into the ulte-
rior of the- doughy mass to ascertain its condition, we have no guide
equal to the sense of touch. Differences of consistence, foreign sub-
stances, dry lumps of flour, are readily distinguished by the hand of
the kneader, who is also by feeling able to control the gradual and
perfect admixture of water, yeast, and flour, better than any machine
yet devised. Much of the excellence of bread depends upon the
thoroughness of the kneading, the reasons of which will soon be
apparent. At first the dough is very adhesive, and clings to the fin-
gers, but it becomes less so the longer the kneading is continued, and
when the fist upon being withdrawn leaves its perfect impression in
the dough, none of it adhering to the hand, the operation may be dis-
continued.

487. Bread from plain Flour and Water. — ^When dough, made by
simply working up flour and water, is dried at common temperatures,
a cake is produced, not very hard, but which is raw, insipid, and indi-
gestible. If baked at 212° (ordinary steam heat), a portion of the
starch becomes soluble, but the cake is dense, compact, and very diffi-
cult of digestion. If baked at a still higher heat, and afterward sub-
jected to prolonged drying, we have the common sMp-lread or sea-
lisGuit, which is made in thin cakes and never in large loaves, and
which is very dry, hard, and difficult to masticate, although it has an
agreeable taste, derived from the roasting of the surface of the dough.
Bread prepared in this manner lacks two essential characters, — sufficient
softness to be readily crushed in the mouth or chewed, and a looseness
of texture or sponginess by which a large surface is exposed to the

BEEAD RAISED BY FERMENTATION. 259

action of the digestive juices in the stomach. To impart these quali-
ties to bread, the dough is subjected to certain operations before bak-
ing, which are technically called raising. The capability of being
raised is due to the gluten. JBy the mechanical operation of kneading,
the glutinous parts of the flour are rendered so elastic that the mass
of dough is capable of expanding to twice or thrice its bulk without
cracking or breaking. Yarious methods are employed for this nur-
pose, which will now be noticed ; and first of fermentation :

2. — ^Beead Raised by Feementation.

488. Substances capable of Putrescence. — ^It is a remarkable property
of the nitrogenous alimentary principles, that when in a moist state,
and exposed to atmospheric oxygen, they speedily enter upon a state of
change or rapid decay. They are of very complex composition (422),
the attractions of their atoms being so delicately adjusted that
Blight disturbing forces easily overturn them. Oxygen of the air
seizes upon the loosely held atoms, breaks up the chemical fabric, and
produces from its ruins a new class of substances — the gaseous pro-
ducts of putrefaction. Thus, it is well known that flesh, blood, milk,
cheese, dough, bread, all of which are rich in nitrogenous substances,
will preserve their properties in the air only a short time, but pass
into a state of putrescence, becoming sour and nauseous, and sending
forth offensive exhalations. This change is called putrefaction, and
the compounds which are liable to it, putrefiable substances.

489. The Putrefactive change Contagious. — The other class of alunents,
the non-nitrogenous, are in this respect of a very different nature.
They contain fewer atoms, lack the fickle element nitrogen, and have
a simpler and firmer composition. "When pure starch, gum, sugar, or
oil, ai'e exposed to the air in a moistened state, they exhibit little ten-
dency to change, and give rise to none of the effects of putrefaction.
Yet if placed in contact with putrefying substances, the change proves
contagious; they catch it, and are themselves decomposed and de-
stroyed. Hence, when the putrefiable substances are considered, with
reference to the effects they produce upon the other class, they take a
new name, and are cai^Qdi ferments. The communication of that con-
dition of change from one class to the other, is called fermentation^
and the substances acted upon are named fermentable compounds.
Thus, if some sugar be dissolved in water, and a portion of putrefying
dough, meat, or white of egg be added to it, fermentation sets in; that
is, the change is commimicated to the sugar, the balance of its affini-
ties is destroyed, and two new substances— one alcohol, containing all

260 CUXINAUY CHA]!TGES OP AlIMENTAEY SUBSTANCES.

the hydrogen of the sugar, and the other carhonic acid, contaming
two-thirds of its oxygen — are produced.

490. Conditions of Fermentation. — When matter capahle of putre-
faction begins to change, decomposition rapidly spreads throughout
the mass. If a small portion of putrefying substance be added to a
large quantity, in which it has not commenced, the change extends
until the whole becomes alike affected. But it is not so in fermenta-
tion. The sugar cannot catch the infection and then go on decompos-
ing itself. It can only break up into new compounds as it is acted,
upon, and when the limited quantity of ferment made use of is ex-
hausted, or spent, the effect ceases, no matter what the amount of
fermentable matter present. Two parts by weight of ferment decom-
pose no more than one hundred of sugar. Temperature controls the
rate or activity of fermentation. At 32° no action takes place; at 45°
it proceeds slowly ; at Y0° to 86°, which is the proper range of warmth,
it goes on rapidly. The operation may be stopped by the exhaustion
of either the ferment or the sugar, by di-ying, by exposure of it to a
boiling heat, and by various chemical substances, as volatile oUs, sul-
phurous acid, &c.

491. Different kinds of Fermentation. — "When nitrogenous matters
are just beginning to decompose, the action is too feeble to establish
the true alcoholic fermentation in solutions of sugar. Yet even in this
early stage they can change the sugar, not breaking it to pieces so com-
pletely, but splitting each of its atoms into two equal atoms of lactic
acid, the sour principle of milk. This process is called the lactic acid
fermentation, while that in which alcohol is produced is the mno^ls or
alcoholic fermentation. If this be not checked, the process is liable to
run on to another stage ; the ferment is capable of attacking the alco-
hol itself, and converting it to acetic acid, the active principle of vine-
gar. This is the acetous fermentation. There are several conditions
of this acetous change. First, a spirituous or alcoholic solution ; second,
a temperature from 80° to 90° ; third, a ferment to give impulse to
the change ; and, fourth, access of air, as oxygen is rapidly absorbed
in the process, combining with and oxidizing the alcohol.

492. Dougli raised by Spontaneous Fermentation. — Now dough, as it con-
tains both gluten and sugar, when moistened is capable of fermentation
without adding any other substance. If simple flour and water be
mixed and set aside in a warm place, after the lapse of several hours it
will exhibit symptoms of internal chemical action, becoming soiu- from
the formation of lactic acid, while miaute bubbles appear, which are ow-
ing to a gas set free within the dough. The changes are irregular and un-

BKEAD RAISED BY FEEMENTATION. 261

certain, according to the proportion and condition of the constituents
of the flour. They also proceed with greater or less rapidity at the
surface or in the interior, accordingly as the parts are exposed to the
cooling and oxidating influence of the air. Bread haked from such
dough, is sour, heavy, and altogether bad. Yet the true vinous fer-
mentation may be spontaneously established in the dough, by taking
measures to quicken the action. If a small portion of flour and water
be mixed to the consistency of batter (its half-fluid state being favor-
able to rapid chemical change), and the mixture be placed in a jar or
pitcher and set in a vessel of water, kept at a temperature from 100°
to 110°, in the course of five or six hours decomposition will have set
in, with a copious production of gas bubbles, which may be seen by
the appearance of the batter when stirred. If this be now mixed and
kneaded with a large mass of dough, moulded into loaves and set
aside for an hour or two in a warm place, the dough will swell, or ' rise '
to a much larger bulk ; and when baked, will yield a light spongy bread.
A little salt is usually added at first, which promotes the fermenta-
tion, and hence, bread raised in this manner is called 'salt raised
bread.' Milk is often used for mixing the flour, instead of water ;
the product is then called ' milk-emptyings bread.'

493. Wliat makes the Dongh rise 1 — The cause of the rising is the
vinous fermentation produced by the spontaneous change of the gluten
or albumen which acts upon the sugar, breaking it up into alcohol and
carbonic acid gas. If the fermentation is regular and equal, the knead-
ing and intermixture thorough, and the dough kept sufiiciently and
uniformly warm, the production of gas will take place evenly through-
out the dough, so that the bread when cut will exhibit numberless
minute cavities or pores, equally distributed throughout. For its capa-
bility of being raised, dough depends upon the elastic and extensible
properties of its gluten, which is developed by the admixture of water
with flour. Hence the proper quantity of water is that which im-
parts to the gluten the greatest tenacity; an excess of it lowering
the adhesiveness of the glutinous particles. The toughness of the
gluten prevents the small bubbles of gas from uniting into larger ones,
or from rising to the surface. Being caught the instant they are pro-
duced, and expanding in the exact spot where they are generated, they
swell or raise the dough. All rising of bread depends upon this prin-
ciple— the liberation of a gas evenly throughout the glutinous dough.
No matter what the mode of fermentation, or what the substances or
agents employed instead of it, they all bring about the result in the
same way.

262 CUIilNAET CHANGES OF ALIMEISTTAEY SUBSTAlirCES.

494. Raising Dongh by Leayen, — But the mode of raising dough by
spontaneous fermentation (492) is not suiEciently prompt and conve-
nient ; we require some readier means of establishing immediate de-
composition. If Tve take a piece of dough which has been kept suffi-
ciently long to ferment and turn sour, and then knead it up thoroughly
with a large lump of fresh dough, the whole of the latter will shortly
enter into a uniform state of fermentation ; and if a little of this be re-
served for the next baking, it may be worked into a fresh mass of dough,
and in this way, active fermentation may be induced at any time.
Fermenting dough thus used is called leaven. It may be made from
any sort of flour, and is improved by the addition of pea and bean
meal, which ferment easily. When properly made, leaven may be
kept weeks or mouths fit for use, and by adding a portion of dough
to the leaven, as large as that reserved for the bread-maker, the
stock of leaven is always kept up. Although leaven when added
to dough, awakens the true alcoholic fermentation, yet being in a sour
state, it produces a portion of lactic acid, and often acetic acid ; the
latter being mostly driven off in the process of baking, whUe the
former remains in the bread. Hence, bread made with leaven always
has a distinctly sour taste, partly caused by the acid of the leaven it-
self, and partly by the sour fermentation which it induces in the
dough. It is difficult to manage, and requires much skUl to produce
a good result. Leaven is but little used in this country, bread be-
ing almost universally raised by means of yeast.

3. Peopeeties and Action of Yeast.

495. Production of Brewer's Teast. — When grains are placed in the
proper conditions of germination, that is, moistened and exposed to
atmospheric oxygen at the proper temperature, a portion of their glu-
ten is changed to the state of ferment, and acquires the property of
transforming starch into sugar. Hence, seeds in germinating become
sweet. Barley placed in these conditions, begins to germinate, swells,
softens, and turns sweet ; it is then heated and dried, by which the
process is stopped. The barley is then called malt. It is next crushed
or ground and infused {mashed) in water at 160° so as to extract all
the soluble matter it contains. The liquid {sweet-wort) is then boiled
to coagulate the excess of vegetable albumen. Hops are added, to
impart a bitter taste to the product (beer), and also to regulate the
subsequent fermentation. The cooled wort is then run into the fer-
menting vat, and yeast is added. " In three or four hours, bubbles of
gas will be seen to rise from all parts of the liquid ; a ring of froth,

PKOPEETIB» AND AC!TION OF YEAST. 263

forming at first around its edge, gradually increases and spreads till it
meets in the centre, and the whole surface becomes covered with a
white creamy foam. The hubbies of gas (carhoniG acid) then rise and
break in such numbers, that they emit a low hissing sound, and the
white foam of yeast continues to increase in thickness, breaking
into little pointed heaps, which become brownish on the surface and
edges ; the yeast gradually thickenilig until it forms a tough, viscid
crust." Although a portion of the yeast was spent in the operation,
yet a much larger quantity has been produced from the nitrogenous
matter of the grain in the solution.

496. Appearance of Yeast — It is a Plant. — Yeast, as usually procured
from the brewer, is a yellowish gray or fawn-colored frothy liquid,
of a bitter taste, and which shrinks in a few hours into one-fourth
the space it occupied at first. "When fresh, it is in constant move-
ment, and bubbles of gas escape frorn it. When dried it loses 70 per
cent, of its weight, becomes solid, horny-looking, half- transparent, and
breaks readily into gray or reddish fragments. The nature of yeast
was for a long time matter of doubt and speculation, but the micro-
scope has at length cleared up the question, and showed t^^at it is a
true plant belonging to the Fungus tribe. Under a powerful magni-
fier, it is seen to consist of numberless minute rounded or oval bodies,
which are true vegetable cells. Each little globule consists of an en-
veloping skin or membrane, containing a liquid within. Such cells
are the minute agencies by which all vegetable growth is affected.
The leaves and pulpy parts of plants are built up of them, as a wall
is built of bricks. All the numberless substances produced by plants,
are generated within these little bodies. They grow or expand from
the minutest microscopic points and seem to
bud oif fi'om each other, as shown in Figs. 98
and 99. The little grains from which they
spring or germinate are shown, and how they
multiply by budding. They are of amazing
minuteness, a single cubic inch of yeast, free
from adhering matter, containing as many
as eleven hundred and fifty-two millions
of them. In what manner yeast acts to
decompose sugar is not known. The yeast
is destroyed or expends itself in producing
the effect, yet it furnishes none of its sub- Teast cells, showing how tiiey
stance to join with the sugar, in producing SSJ 'o^r t't "esc'apini
alcohol and carbonic acid. Liebig supposes *^°°^ ^^^^ interior.
the efiect to be dynamic^ that is, produced by an impulse of force ; the

264 CULIN'AET CHANGES OF AUMENTAET SUBSTANCES.

Fia.

motions of the atoms of the decomposing ferment, being commnni-
cated to the atoms of sugar, set these also in motion, by which the
sugar structure is, as it were, jarred and shaken to pieces, its atoms
falling into new arrangements and forming new substances,

497, Domestic preparation of Yeast — ^Fowne's method. — But, as
many have no access to breweries, it is desirable to know how
to make yeast at home. If common wheaten flour be mixed
with water to a thick paste, and
exposed slightly covered, and
left to spontaneous change in a
moderately warm place, it wUl,
after the thu-d day, begin to
emit a little gas, and to exhale
an exceeding disagreeable sour
odor. After the lapse of some
time this smell disappears ; the
gas evolved is greatly increased,
and is accompanied with a dis-
tinct agreeable vinous odor ; this
will happen about the sixth or
seventh day, and the substance
is then in a state to excite fer-
mentation. An infusion of crush-
ed malt (wort) is then boiled
with hops, and when cooled to
90° or 100°, the altered dough,
above described, after being
thoroughly mixed with a little
lukewarm water, is added to it,

, ,T. , , 14., V „ A developed yeast plant, the numbers indi-

and the temperature kept up by eating the successive stages of growth,
placing the vessel in a warm situ-
ation. After a few hours fermentation commences, and when that is
complete, and the liquid clear, a large quantity of excellent yeast is
formed at the bottom.

498. Yeast from Potatoes.— Boil half a dozen potatoes in three or
four quarts of water, with a couple of handfuls of hops placed in a
bag. Mash the potatoes and mix with the water, adding and stirring
in a little salt, molasses and flour, until it is of a battery consistence.
Then mix in a couple of spoonfuls of active yeast. Place before the
fire, when it will soon begin to ferment. In a cool place it may
be kept for weeks.

PROPERTIES AND ACTION OP YEAST. 265

499. Action of Hops in Teast-making. — Hop-flowers contain about 8
per cent, of a brownish yellow bitter volatile oil, upon which its pecu-
liar odor depends. The hop has been long known for its soporific or
sleep-producing properties, which are supposed to be duo to this
volatile narcotic oil. When dry hop-flowers are beat, rubbed and
sifted, they yield about 8 per cent, of fine yellow dust — an aromatic
resin, which has an agreeable odor, and a bitter taste. "When taken
internally it has a soothing, tranquillizing, sleep-provoking influence.
It is caUed lupulin. Hops also contain a considerable proportion of
another strong bitter principle, which is said not to be narcotic. In
brewing, the chief use of hops is to impart an agreeable bitterness to
the beer, but it also has the effect of arresting or checking fermenta-
tion before all the sugar is converted into alcohol, and then prevent-
ing the production of acid. It is also well-known that in the domestic
preparation of yeast, hops serve to prevent the mixture from souring,
though Jiow this is affected we cannot tell.

500. Yeast preserved by drying. — The liquid, or active yeast, is liable
to turn sour and spoil in warm weather, losing its properties and im-
parting to bread a most disagreeable flavor. Drying has therefore
been resorted to, as a means of preserving it. On a large scale, it is
pressed in bags and dried at a gentle heat, until it loses two-tbirds of
its weight of water, leaving a granular or powdery substance, which,
if packed and kept from the air and quite dry, may be preserved a
long time. It is curious that mechanical injury kills or destroys yeast.
Falls, bruises, a rough handling spoils it, so that great care is required
to remove it from place to place. LiEBia remarks that simple pressure
diminishes the power of yeast to escite the vinous fermentation.
Yeast is also preserved by dipping twigs in it and drying them in the
air. Or it may be worked round with a whisk untU it becomes
thin, and then spread with a brush over a piece of clean wood and
dried. Successive coats may be thus applied, until it becomes an inch
or two in thickness. "When thoroughly dried, it can be preserved in
bottles or canisters. Yeast is also commonly^-eserved by adding to it
maize meal, and making it into a dough which is wrought into cakes
and dried. They may be kept for months and are ready for use at
any time, by crumbling down and soaking a few hours in warm water.
We add minuter directions for making yeast-cakes. Eub three ounces
of fresh hops until they are separated, boil half an hour in a gallon of
water, and strain the liquid through a fine sieve into an earthen vessel.
While hot, stir in briskly 3i lbs. of rye flour. Next day, thoroughly
mix in 7 lbs. of Indian meal, forming a stiff dough ; knead it well, roll

12

266 CULTNAET CHANGES OF ALIMENTAEY SUBSTANCES.

it out a third or half an inch thick, cut into cakes and dry in the sun,
turning every day and protecting from wet. If preserved perfectly
from damp they will keep long.

501. Bitterness of Yeast— how corrected. — Yeast is often so bitter as to
communicate a most disagreeable taste to bread. This may be de-
rived from an excess of hops. To rectify this, mix with the yeast a
considerable quantity of water, and set it by to rest for some hours,
when the thickest part will fall to the bottom. Pour off the water
which will have extracted a part of the bitter principle, and use only
the stiff portion that has fallen to the bottom. But yeast sometimes
acquires a bitter taste from keeping, which is quite independent of that
derived from the hops. One method of remedying this, consists in
throwing into the yeast a few clean coals freshly taken from the fire,
but allowed to cool a little on the surface. The operation appears to
depend in principle upon the power of freshly burnt charcoal to ab-
sorb gases and remove offensive odors (811).

502. Acidity of Teast— how corrected, — In country places, where it is
customary to keep yeast for some time, and especially during the
warmth of summer, it is very liable to sour. In such case, it may
be restored to sweetness, by adding a little carbonate of soda or car-
bonate of magnesia, only so much being used as may be necessary to
neutralize the acidity.

503. Dough raised by Yeast. — How fermentation lightens dough, has
been shown (493). Yeast produces these changes promptly and effec-
tually. It is mixed with a suitable portion of water, flour, and salt,
to form a stiff batter, which is placed near the fire for an hour or two,
covered with a cloth. This is called setting the sponge. An active fer-
mentation is commenced, and the carbonic acid formed in the viscid
mass, causes it to swell up to twice its original size. If not then quickly
used iifalls^ that is, the accumulated gas within escapes, and the dough
collapses. Yet after a time it may again rise, and even fall a second
time and rise again. This, however, is not allowed. When it has fully
risen, much more flour is thoroughly kneaded with the sponge, and
the dough is left for perhaps an hour and a half, when it rises again.
It is then again kneaded and divided into pieces of the proper size foi
loaves. The loaves should be moulded with care, as too much hand-
ling is apt to cause the escape of the enclosed gas, and make the
bread heavy.

504. Correction of Acidity in Dongh. — Dough is frequently sour
from an acid condition of the flour. It may be in this condition from
a sour state of the yeast, or the fermentation may be so feeble as to

KAISrNG BREAD WITHOUT FEEMENTATION. 267

produce acid (476), or it may be too active and rapid, if too much or
too strong yeast lias been used ; or in hot weather when the dough is
liable to sour by running into the acetous fermentation. If the diffi-
culty is too sluggish a change, it should be hastened by securing the
most favorable warmth. If, on the contrary, it is too violent, it may be
checked by uncovering the dough, and exposing it to the air in a cool
place. If the dough be already sour, it may be sweetened by alkaline
substances. Carbonate of soda will answer this purpose. Carbonate
of ammonia is perhaps better, as it is a volatile salt, and is raised in
vapor and expelled by the heat of the oven (510). If too much be used,
a portion of the excess is driven off by the heat, and in escaping assists
in making the bread lighter. Caution should, however, be employed
to use no more alkali than is really necessary to neutralize the acid.
"When the acidity is but slight, it may be rectified by simply kneading
the dough with the fingers moistened with an alkaline solution.

505. The Sugar of Flour all decomposed in Dough. — It is at the ex-
pense of sugar destroyed that fermented bread is raised, but how much
sugar is thus decomposed is variously stated, and depends upon the
activity and continuance of fermentation. Experiments would seem
to show, that all the sugar present is rarely, if ever, destroyed.
The raised dough and bread both contain sugar, often nearly as much
as the flour before it was used. This is explained by remembering
that one of the effects of fermentation is to change starch to sugar.

506. How much Alcohol is produced iu Bread. — Of course the quantity
of alcohol and carbonic acid generated in bread is in exact proportion
to the amount of sugar destroyed, which, as we have said, is by no
means constant. In an experiment, a pound of bread occupied a space
of 60 cubic inches, 26 of which were solid bread, and 34, cell-cavi-
ties; consequently 34 cubic inches of carbonic acid of the heat of the
oven were generated to raise it, which implied the production of about
15 grains of alcohol, or less than one-quarter of one per cent, of the
weight of bread. It has been attempted to save this alcohol, which
is vaporized and driven off into the air by the baking heat, but the
product obtained was found to be so small as not to pay cost. It is
also a current statement, that alcohol exists in the bread, contributing
to its nutritive qualities. "We have never found it there, and never
saw a chemical analysis of bread that enumerated it as a constituent.

4. Kaising Bkead withotjt Fermentation.

507. Objections to raising by Ferment. — Two or three objections have
been urged against raising bread by fermentation. First, the loss of

268 CULINAEY CHAKGES OF ALIMENTAEY SUBSTANCES.

a portion of the sugar of tlie flour which is decomposed ; this loss, how-
ever, is trifling, and the objection futile. It is said, secondly, that as
a destruction or incipient rotting process has been established in the
dough, bread made from it cannot be healthful. This is only /ancy,
experience is wanting to show that well-made fermented bread is ia-
jurious. Thirdly, it is said that the fermenting process is not only-
uncertain, but slow, and requires more time than it is often convenient
to allow. There is such force in this latter objection, that means have
been sought to replace fermentation by some quicker and readier
method of raising the dough.

508. How it is done without Ferment. — As the lightening and expan-
sion of the dough are caused by gas generated within it, it would seem
that we may adopt any means to produce such a result. It is com-
monly done in two ways ; either by mixing chemical substances
with the flour, which, when brought into contact and wet, act
upon each other so as to set free a gas, or by introducing into the
dough a volatile solid substance, which, by the heat of baking, ri^es
into the state of gas. In the first case, substances are used which set
free carbonic acid ; in the second case, a compound of ammonia.

509. Raising Bread with Chemical Substances. — Bicarbonate of soda and
hydrochloric acid are used for raising bread. The soda is mixed inti-
mately with the flour, and the acid is added to the water requisite to
form dough. Peeeiea indicates the following proportions :

Flour 1 lb.

Bicarbonate of soda 40 grains.

Cold water, or any liquid necessary ■§■ pint.

Hydrocliloric acid 50 drops.

The soda and flour being mixed, the acidulated water is added gradu-
ally, with rapid stirring, so as to mix speedily. Divide into two loaves,
and put into a hot oven immediately. The acid combining with the
soda, sets free its carbonic acid, which distends the dough. Both the
acid and the alkali disappear, are destroyed, and the new sub-
stance formed by their union is chloride of sodium, or common salt;
so that this means of raising bread answers also to salt it. If the in-
gredients be pure, the proportions proper, and the mixture perfect, no
other substance will remain in the bread. If the acid be in excess, there
wUl be sourness ; and if there be too much alkali, or if it be not en-
tirely neutralized, unsightly yellow stains in the bread crumb will be
apparent, accompanied by the peculiar, hot, bitter, alkaline taste, and
various injurious efiects. The changes that take place are thus shown.
"We begin with —

RAISING BEEAD WITHOTJT FEEMENTATION. 269

Bicarbonate of soda; J ^ ,
{solid,) and r .^^l^>

Carbonic acid;

Water ;

{liquid,) and
Common salt ;

{solid.)

Bread is also raised "with soda powders ; — tartaric acid, and bicar-
bonate of soda, ■which are the active ingredients in effervescing draughts.
The changes are these

Bicarbonate of soda; ^ ■^y.r.A^^a C Carbonic acid;

{solid,) and ( P[° the } (^«^') '^""^

Tartaric acid; ( ^„ „i, ) Tartrate of soda;

{solid,) ) ^°'^S'^> ( {solid.)

Cream of tartar, consisting of tartaric acid combined with and partly
neutralized by potash, is also used with soda, one being mixed with
flour, and the other dissolved in water. Double the quantity of cream
of tartar to soda is commonly used, but of tartaric acid only an equal,
or slightly less quantity. In these cases tartrate of soda is formed in
the bread, which, in its action upon the system, is hke cream of tartar
— gently aperient. Preparations which are known as egg-powder,
baking-powder, and ctista/)'d-powders, consist of bicarbonate of soda and
tartaric acid, mixed with wheat flour or starch, and colored yellow
with turmeric, or even poisonous chromate of lead. The diflicnlty Avith
these powders, is to get them in perfect neutralizing proportions.
This may be ascertained by dissolving them in water ; the mixture
should be neutral to the taste, and produce no effervescence by
adding either alkali or acid. Sour milk, or buttermilk, are often used
with soda or saleratus. In these cases the lactic acid they contain
combines with the alkali, forming lactate of soda, or potash, and set-
ting carbonic acid free, which lightens the dough, just as in all the
other instances.

510. Sesquicarbonate of Ammonia. — The perfect theoretic conditions
of raising bread without ferment would be, to find a solid substance
which could be introduced into the flour, but which would entirely es-
cape as a gas during baking, raising the bread, and leaving no trace of
its presence. Carbonate of ammonia complies with the first of these
conditions ; it is a solid which, under the influence of heat, is decom-
posed entirely into gases. Tlius —

Sesquicarbonate of

in baking

Ammonia; l m "^J^mg

(solid \ i produces,

(solid,)

Ammonia ;

{gas,)
Bicarbonate op
Ammonia ;

{gas,)
Carbonic acid,

(gas.)

270 CULINAKT CHAITGES OP ATJMENTABY SUBSTANCES.

Yet practically these gases do not all escape in baking ; a portion of
them is apt to remain, communicating a disagreeable hartshorn flavor.
All these methods have one common and serious disadvantage — the
gas is set free too suddenly to produce the best effect. Alum and car-
bonate of ammonia are sometimes used ; they act more slowly, but
leave an unwholesome residue of alumina and sulphate of ammonia in
the bread.

511. Important Cantion in reference to the Chemicals used. — The class
of substances thus introduced in the bread are not nutritive but me-
dicinal, and esert a disturbing action upon the healthy organism.
And although their occasional and cautious employment may perhaps
be tolerated, on the ground of convenience, yet we consider their ha-
bitual use as highly injudicious and unwise. This is the best that can
be said of the chemical substances used to raise bread, even when
pure, but as commonly obtained they are apt to be contaminated with
impurities more objectionable still. For example, the commercial mu-
riatic acid which is commonly employed along with bicarbonate of
soda, is always most impure — often containing chlorine, chloride of
iron, sulphurous acid, and even arsenic, so that the chemist never uses
it without a tedious process of purification for his purposes, which are
of far less importance than its employment in diet. "While common
commercial hydrochloric acid sells for 3 cents per pound wholesale,
the purified article is sold for 35. Tartaric acid is apt to contain lime,
and is frequently adulterated with cream of tartar, which is sold at
half the price, and greatly reduces its efficacy ; while cream of tar-
tar is variously mixed with alum, chalk, bisulphate of potash, tartrate
of lime, and even sand. Sesquicarbonate of ammonia is liable by ex-
posure to air to lose a portion of its ammonia. It is hence seen that
the substances we employ are not only liable to injure by ingredients
which they may conceal, but that their irregular composition must
often more or less defeat the end for which they are intended. "We
may suggest that, in the absence of tests, the best practical defence is
to purchase these materials of the druggist rather than the grocer. If
soda is desired, call for the licarionate of soda ; it contains a double
charge of carbonic acid, and is purest. Soda-saleratus is only the
crude, impure carbonate — soda-ash. The cream of tartar should appear
white and pure, and not of a yellowish tinge (698).

512. Raising Dongh with Oily Snbstanccs and Eggs. — If dough be mixed
with butter or lard, rolled out into a thin sheet, and covered with a
thin layer of the oily matter, then folded, rolled and recoated from 2
to 10 times, and the sheet thus produced be submitted to the oven, the

ALTEEATIONS PEODUCED EST BAEING BREAD. 271

heat causes the disengagement of elastic vapor from the water and
fatty matter, which, heiag diffused between the numerous layers of
dough, causes them to swell up, producing the flaky or puffy appearance
which is seen in pastry. This kiad of lightness must not be confound-
ed with that produced by the other methods described ; for, although
the layers are partially separated, yet the substance of each stratum
is dense and hard of digestion. The albumen of eggs, when smartly
beaten, becomes frothy and swells, by entangling much air in its
meshes. If then mixed with dough, it conveys with it air bubbles,
which are expanded in baking. From its glairy, tenacious consistence
when mixed with dough or pudding, it encloses globules of gas or
steam, which are generated by fermentation or heat. In this way egga
contribute to the lightness of baked articles.

513. Kaising Gingerbread. — Gingerbread usually contains so much
molasses that it cannot be fermented by yeast. But the molasses is of
itself always acidulous, and takes effect upon the saleratus, setting
free carbonic acid gas. Sour mUk, buttermilk, and cream, are also
used, which act in the same way upon the carbonate of soda or potash,
and thus inflate the dough. Dr. Colquhoxtn has found that carbonate
of magnesia and tartaric acid may replace the saleratus (and alum
also, which is sometimes used), affording a gingerbread more agreeable
and wholesome than the common. His proportions are, 1 lb. of flour,
■i oz. carbonate of magnesia, \ oz. of tartaric acid, with the requisite
molasses, butter, and aromatics.

5, AxTEEATioNS Peodtjoed ht Bakin& Beead.

514. Temperature of the Oyen.— Bread is usually baked by heat radi-
ated or conducted from the brick walls or iron plates of which ovens
are made. The oven should be so constructed that the heat may be
equal in its different parts, and remain constant for a considerable
time. If the heat be insufiicient, the bread will be soft, wet, and
pasty ; if on the other hand the heat be too great at first, a thick,
burnt crust is produced, forming a non-conducting carbonaceous cov-
ering to the loaf, which prevents the heat from penetrating to the
Interior. Hence a burnt outside is often accompanied by half-raw
dough within. If, however, the temperature be proper, the heat
passes to the interior of the loaf and produces the necessary changes
before the outside becomes thickly crusted. If we cut open a well
baked loaf, immediately from the oven, and bury the bulb of a ther-
mometer in the crumb, it wiU rise to 212°. This heat is sufficient to

2V2 CULINABY CHA2TGES OF AXIMENTART SUBSTANCES.

carry on the iimer chemical changes of baking, and it is obvious that
the heat cannot rise above this point so long as the loaf continues
moist (65.) Bread might be baked at a temperature of 212° (by
steam), but then it would lack that indispensable part, the crust. The
baking temperature of the oven ranges from 360° to 450° or 500°, and
bakers have various means of judging about it. If fresh flour strewn
upon the oven bottom turns brown, the heat is right, if it chars or
turns black, the heat is too great.

515. Heat causes a loss of Weight. — The loaf loses a portion of its
weight by evaporation. The quantity thus lost depends chiefly upon
the size and form of the loaf. If it be small or thin, it will part with
more water in proportion than if of cubical shape. Something de-
pends upon the quality of the flour and the consistence of the dough.
"Various experiments would seem to show that bread parts with from
one-sixth to one-tenth of its weight in baking. In those places where
bread is required by law to be of a certain weight, this loss must be
calculated upon and a proportionate amount of additional flour used.
Peechtl states from experiment that loaves which, after baking and
drying, weigh one pound, require that an extra weight be taken, in
dough, of six ounces ; if the loaves are to weigh three pounds, twelve
ounces additional must be taken, and if sis pounds, sixteen ounces.

516. How Heat enlarges the Loaf. — When the loaf is exposed to the
heat of the oven, it swells to about twice its size. This is owing to
the expansion of the carbonic acid gas contained in its porous spaces,
the conversion of water into steam, and the vaporizing of alcohol,
which also rises into the gaseous form and is driven off, as is shown
by the spirituous odor yielded in the baking process.

517. Chemical Changes in prodneing the Crust. — The heat of the oven
falling upon the surface of the loaf causes first the rapid evaporation
of its water, and then begins to produce a disorganization of the
dough. The starch-grains are ruptui-ed (530) and its substance con-
verted into gum; as the roasting continues chemical decomposition
goes on, and organic matter is produced of a brown color, an agreeable
bitter taste, and soluble in water, which has received the name of
assamar. The formation of hard crusts on the loaf may be prevented
by baking it in a covered tin, or, it is said, by rubbing a little melted
lard over it after it is shaped and before it is set down to rise.

518. Chemical Changes in producing the Crumb. — As the temperature
within the loaf does not rise above 212°, no changes can go on there
except such as are produced by the heat of the aqueous vapor. This
is sufficient to stop the fermentation, destroy the bitter principle of

AITEEATIONS PEODUCED IN BAKING BREAD. 273

the yeast, and kill the yeast plant. In baking about one-fourteenth of
the starch is converted into gum, the rest is not chemically altered, as
may be shown by moistening a little bread-crumb and touching it with
solution of iodine, when the blue color will prove the presence of
starch. The gluten, although not decomposed, is disunited, losing its
tough, adhesive qualities. The gluten and starch-paste are intimately
mixed, but they do not unite to form a chemical compound.

519. Moisture contained in Bread. — In newly-baked bread the crust
is dry and crisp, while the crumb is soft and moist, but after a short
time this condition of things is quite reversed. The brown products
of the roasting process attract moisture and the crust gets daily softer,
while the crumb becomes dry. Bread, two or three days old, loses
its softness, becoming hard and crumbly. But this apparent dry-
ness is not caused by evaporation or loss of water, for it may be
shown by careful weighing that stale bread contains almost exactly
the same proportion of water as new bread that has become com-
pletely cold. The change to dryness seems to be one of combination
going on among the atoms of water and bread. That the moisture
has only passed into a state of concealment may be shown by exposing
a stale loaf in a closely covered tin for half-an-hour to a boiling heat,
when it will again have the appearance of new bread. The quantity
of water which well-baked wheaten bread contains amounts, on an
average, to about 45 per cent. The bread we eat is, therefore, nearly
one-half water. It is, in fact, both meat and drink together. One of
the reasons why bread retains so much water is, that during the
baking a portion of the starch is converted into gum, which holds
water more strongly than starch does. A second is, that the gluten
of flour when once thoroughly wet is very difficult to dry again, and
that it forms a tenacious coating round every little hollow cell in the
bread, which coating does not readily allow the gas contained in the
cell to escape, or the water to dry up and pass off in vapor ; and a
third reason is, that the dry crust which forms round the bread in
baking is nearly impervious to water, and, like the skin of the potato
we bake in the oven or in the hot cinders, prevents the moisture from
escaping. — (Johnston.)

520. Qualities of Good Bread, — In baking bread, it is desirable to
avoid the evils of hardness on the one hand and pastiness on the other,
nor should it be sour, dense, or heavy. It should be thoroughly and
uniformly kneaded, so that the carbonic acid wiU not be liberated in
excess in any one place, forming large hollows and detaching the
crumb from the crust. The vesicles should be numerous, small, and

12*

274 CULINAET CHANGES OF ALIMENTARY SUBSTANCES.

equally disseminated ; nor should the crust be bitter and black, but of
an aromatic agreeable flavor. " If the yeast be so diffused throughout
the whole mass as that a suitable portion of it will act on each and
every particle of the saccharine matter at the same time, and if the
dough be of such consistency and temperature as not to admit of too
rapid a fermentation, then each minute portion of saccharine matter
throughout the whole mass will, in the process of fermentation, pro-
duce its little volume of air, which will form its little cell, about
the size of a pin's head and smaller, and this will take place so nearly
at the same time in every part of the dough, that the whole will be
raised and made as light as a sponge before the acetous fermentation
takes place in any part. And then, if it be properly moulded and baked,
it will make the most beautiful and delicious bread, perfectly light and
sweet, without the use of any alkali, and with all the gluten and nearly
all the starch of the meal remaining unchanged by fermentation." —
(Geaham.)

6. IlSTFLTJENOE OF FoEEIGN SuBSTANCES TJPON BeEAD.

521. Common Salt, ilum, &c. — It has been found that certain mineral
substances influence in a remarkable degree the aspect and properties
of bread, causing that made of inferior flour to resemble, in appear-
ance, bread made from the best quality. Common salt produces this
effect in a decided degree. It whitens the bread and causes it to
absorb and retain a larger amount of water than the flour would
otherwise hold. In consequence of this influence and under cover of
the fact, that salt is a generally admitted element of diet, it is often
introduced into bread more freely than is consistent with health (697).
Alum has exactly the same effect on bread as common salt, but in a
much more marked degree. A small quantity of it wUl bring up a
bad flour to the whiteness of the best sort, and wiU enable it to hold
an extra dose of water. It is much used for this purpose, and the
baker who employs it not only practises upon the consumer a double
imposition, but drugs him with a highly injurious mineral into the
bargain. Mitchell detected in ten four-pound loaves 819 grains of
alum, the quantity in each loaf ranging from 34 to 116 grains. Sul-
phate of copper (blue vitriol), in exceedingly minute proportions,
exerts a striking influence upon bread in the same manner as alum.
Carlonate of magnesia has a similar effect, and its use in so large
quantities as from 20 to 40 grains to the pound of flour has been re-
commended on scientific authority.* This substance has been also

* Dr. C. Davy.

ESTFLUENCE OF FOEEIGN SUBSTANCES UPON BEEAD. 2V5

recommended for correcting acidity in yeast, dough, &c., instead of
soda, and because it is less powerfully alkaline. But from its diffi-
cultly soluble earthy nature, it tends to accumulate in the system in
the highly objectionable shape of concretions and deposits.

522. Lieliig recommends Lime-water in Breadi — However it is to be
lamented, it is nevertheless a fact, that enormous quantities of flour,
more or less deteriorated, are purchased in the markets of this country ;
and if there be any method of improving its condition by means that
are not essentially injurious, they are certainly most desirable. Indeed,
it is well known that flour is injured by time alcne, so that freshly
ground flower is always more prized than that which is several months
old. The scientific reason is apparent. Vegetable gluten in contact
with water becomes chemically changed, and loses its peculiar tough
elastic properties. As these are essential to bread-making, flour that
has been altered in this way necessarily makes a bad dough, Now,
flour is ia a high degree a water-absorbing substance, so much so that
it attracts and combines with the moisture of the air, and is thus
injm-ed. This can only be avoided by artificial drying and protecting
thoroughly from the air. The eflect of the substances noticed in the
previous paragraph is to combine with the gluten thus partially
changed, and in a measure to restore its lost properties. Upon inves-
tigating this subject, Liebig found that lime-water is capable of pro-
ducing this effect, and thus of greatly improving old, or low grade
flour.

523. How Lime-water Bread is prepared. — To make lime-water
chemists usually employ water that has been distilled; very pure
soft water, as clean rain water, may, however, be used. Mix a quarter
of a pound of slacked lime in a gallon of such cold water in stoppered
bottles or vessels kept tight from the air. The mass of the lime falls
to the bottom, leaving the liquid above, which has dissolved l-600th
its weight of lime, clear and transparent. This is to be poured off
when required for use and replaced by pure water. Liebig recom-
mends 5 lbs. or pints of lime-water to every 19 lbs. of flour, although
this quantity of lime-water does not suffice for mixing the bread,
and of course common water must be added, as much as is requisite.
" If the lime-water be mixed with flour intended for the dough, and
then the yeast added, fermentation progresses in the same manner as
in the absence of lime-water. If at the proper time more flour be
added to the risen or fermented dough, and the whole formed into
loaves and baked as usual, a sweet, beautiful, fine-grained elastic
bread is obtained of exquisite taste, which is preferred by aU who have

|Pr

276 CULINARY CHANGES OF ALIMENTARY SUBSTANCES.

eaten it for any length of time to any other." — (Liebig.) The use of
lime-water removes all acidity from the dough, and also somewhat
augments the proportion of water ahsorbed.

524. Its Physiological claims. — The quantity of lime introduced into
the system by the use of this bread, is by no means large. A pound
of lime-water sufl&ces for 4 lbs. of flour, which with the common water
added, yields 6 lbs. of bread ; and as the pound of lime-water contains
but l-600th of lime, with this artificially added the cereal grains
still contain less of it than peas and beans. Indeed, Liebig ha-s sug-
gested that expex'ience may yet prove the cereal grains to be incapable
of perfect nutrition, on account of their small proportion of the bone-
forming element.

525. Different kinds of Bread. — Eice flour added to wheaten flour
enables it to take up an increased quantity of water. Boiled and
mashed potatoes mixed with the dough cause the bread to retain
moisture, and prevent it from drying and crumbling. Rye makes a
dark-colored bread, and is capable of being fermented and raised in
the same manner as wheat. It retains its freshness and moisture
longer than wheat. An admixture of rye flour, with that of wheat,
decidedly improves the latter in this respect. Indian corn bread is
much used in this country. Mixed with wheat and rye, a dough is
produced capable of fermentation, but pure maize meal cannot be fer-
mented so as to form a light bread. Its gluten lacks the tenacious
quality necessary to produce the regular cell-structure. It is most
commonly used in the form of cakes, made to a certain degree light
by eggs or sour milk and saleratus, and is generally eaten warm.
Indian corn is ground into meal of various degrees of coarseness, but
is never made so fine as wheaten flour. Bread or cakes from maize
require a considerably longer time to be acted upon by heat in the
baking process than wheat or rye. If ground wheat be unbolted, that
is, if its bran be not separated, wheat meal or Graham flour results, from
which Graham or dyspepsia bread is produced. It is made in the same
general way as other wheaten bread, but requires a little peculiar man-
agement. IJpon this point Mr. Geaham remarks : " The wheat meal,
and especially if it is ground coarsel}^, swells considerably in the
dough, and therefore the dough should not at first be made quite so
stiff as that made of superfine flour; and when it is raised, if it is
found too soft to mould well, a little more meal may be added." It
should be remarked that dough made of Avheat meal will take on the
acetous fermentation, or become sour sooner than that made of fine
flour. It requires a hotter oven, and to be baked longer. Puddings

VEGETABLE FOODS CHANGED BY BOILING. 27*7

in whicli flour is an ingredient are changed by the baking process in
the same way as bread. They are usually mixed with milk instead
of water, and made thinner than dough. Yeast is not used to raise
them, eggs being commonly employed for this purpose, and sometimes
other substances.

526. White and Brown Bread— A new French Plan. — ^M. Moueies, of
Paris, has announced some new views of bread making, theoretic and
practical, upon which a commission of the French Academy has just
reported favorably. He claims the discovery of a nitrogenous sub-
stance called eerealine, which is a very active ferment, rendering
starch soluble, altering gluten to a brown substance, and actively pro-
ducing lactic acid instead of carbonic acid and alcohol. It resides
near the surface of the wheat-grain, so that in grinding, it is nearly all
separated in the bran, leaving but little in the white flour. M. Mou-
eies states that in bread made from unbolted flour, the tendency to
sourness, the softness, crumbliness, and want of firmness of the crumb,
and the 'brown color also of the bread, are due to cerealine. He says
cerealine ferment wHl make a brown bread of the whitest flour,
whereas, if it be neutralized, a white bread can le made from a darh
flour containing bran. He grinds wheat so as to separate it into about
Y4 per cent, of fine fiour, 16 of brown meal, and 10 of bran. The
brown meal is then so acted on by yeast as to neutralize the cerealine.
The product in a liquid form is used to mix white flour into dough,
which is baked as usual. The claims of this method are, a larger
economy of ground products, making a white bread from dark mate-
rials, preventing the liability to acidity, and a yield of the finest,
lightest, and sweetest bread, comprising the largest portion of farina-
ceous materials.

7. — Vegetable Foods changed by Boiling.

527. Its General Effects.— Boiling dificrs from baking in several re-
spects. First, the heat never rises above the boiling point, and the
changes of course are such only as may be produced by that tempera-
ture. Second, the food is surrounded by a powerful solvent, which
more or less completely extracts certain constituents of the food. Veg-
etable acids, sugar, gum existing in the organic matter, and gum
formed from starch, with vegetable albumen, are all soluble in water,
and by boiling are partially removed. The tougher parts are made
tender, the hard parts softened, and the connections of the fibres and
tissues loosened, so as to be more readily masticated, more easily pen-
etrated by the saliva and juices of the stomach, and hence more

278 CULINAET CHANGES OF ALIMENTAEY SUBSTANCES.

promptly and perfectly digested. Perhaps we may here most con-
veniently consider the specific effects of heat npon the chief constitu-
ents of which vegetable foods are composed.

528. Changes of Woody Fibre. — A constituent more or less abundant
of all vegetable substances is woody fibre. We find it in the husk or
bran of grains, the membrane covering beans and peas, the vessels of
leaves and leaf-stalks, the skin of potatoes, the peel and core of apples
and pears, the kernels of nuts, and the peel of cucumbers, melons, &c.,
&c. "We are hardly justified in ranking woody fibre, as Peeeiea has
done, among aliments. Indeed, he remarks, " although I have placed
ligneous matter among the alimentary principles, yet I confess I am
by no means satisfied that it is capable of yielding nutriment to man."
Yet it is important to understand how it may be affected by the heat
of culinary operations. Boiling in water does not dissolve it ; but
by dissolving various substances with which it is associated, it only
renders it the more pure. Yet woody fibre seems capable, by the joint
action of heat and chemical agencies, of being converted into nutritive
matter. If old linen or cotton rags, paper, or fine sawdust, be boiled
in a strong solution of alkali, or moistened with pretty strong sulphu-
ric acid, the woody substance is changed, being converted first into
gum or dextrin, and then into grape sugar. By such modes of treat-
ment old rags may be made to yield more than their weight of sugar.
But weak solutions of acid or alkali do not produce any such effect.
For will strong vinegar. TVe may therefore assume that woody fibre
remains totally unchanged by exposure to culinary agencies and ope-
rations. Professor AuTE^rrjETH, of Tubingen, announced some years
since, a method of preparing bread from wood-powder or wood-flour,
which was changed into nutritive matter by successive heatings in an
oven. "We are not aware that his experiments have been confirmed,
while it is suspected that whatever nutritive value his bread may have
possessed, was due to starch associated with the wood.

529. Changes of Sugar. — Sugar, dissolved in cold water, or boiled
to a sirup, has very diflerent properties, as is well known to those
who feed it to bees in winter. In the first case, the warmth of the
hive will dry up the water and leave the sugar in hard crystals which
the bees cannot take ; but by boiling, the water and sugar become so
intimately united that the mixture does not become dry, but retains
the consistence of sirup. If melted sugar be kept for some time at
350°, it loses the property of crystallizing when redissolved in water,
its properties being in some way deeply altered. If dry sugar be
heated to a little above 400°, it loses the sugar taste and becomes not

VEGETABLE FOODS CHANGED BY BOILING.

279

Fia. 100.

only very soluble in water, but also very absorbent of it {deliquescent)')
turns of a deep brown color, and is used to stain liquids of a dark red,
or wine color, under the name of caramel. Sugar itself is slightly
acid, and forms compounds with bases which are of a salt nature, and
known as saccharates. Caramel is more decidedly acid, and if the
sugar be heated still higher it is converted into still stronger acid pro-
ducts with inflammable gases.

530. Breaking np of the Starch Grains. — The structure of starch grains
has been described (384). They consist of layers or coats arranged
concentrically around a point called the Mlum. If
one of these grains be strongly compressed between
two plates of glass it breaks apart into several pieces,
as seen in Fig. 100, and all the planes of rupture
generally pass through the hilum as if the substance
were less resistent at that point. But under the joint
action of heat and water, the grains break up differ-
ently. Their membranes are torn apart, or exfoliated
by internal swelling, as shown in Fig. 101.

531. Changes of Starch. — Starch is but slightly acted througTits hUum.^
upon by cold water. "When heated with water it

does not dissolve ; but the grains swell, forming a viscid mucUaginous
mass, a kind of stiff, half opaque jelly. When starch is diluted with
twelve or fifteen times its weight of water,
the temperature of which is slowly raised,
all the grains burst on approaching the
boiling point, and swell to such a degree as
to occupy nearly the whole volume of the
liquid, forming a gelatinous paste. If a
pint of hot water be poured on a table-
spoonful of arrow-root starch, it imme-
diately loses its whitenes and opacity, be-
comes transparent, and the entire matter °'
passes into the condition of a thick jelly. If a little of this be diffused
through cold water and examined with the microscope, it will be seen
that the starch grains are greatly altered. They have increased to
twenty or thirty times their original size ; the concentric lines are
obliterated (384) ; the membrane of the grain is ruptured, and its inte-
rior matter has escaped. A cold jelly of starch and water, left to stand,
either closed or exposed to the air, gradually changes, first into gum
(dextrin), and then into sugar. The process, however, is slow, and
months must elapse before the whole of the starch is thus transformed.

Fig. 101.

starch grain ruptured by boil-

280 CULESTAET CHANGES OF ALIMENTAET SUBSTANCES.

By being boiled in water for a considerable time, it undergoes the
same change, and if the water be acidulous the change is quickened.
When dry starch is gradually heated to a temperature not exceeding
300°, it slowly changes, acquires a yellow or brownish tint, and be-
comes entirely soluble in cold water. It is changed to dextrin or
gum (British gum).

532. How Potatoes are changed by Cooking. — By referring to the
statement of the composition of potatoes (461), we shall notice that
a pound contains about three-quarters of a pound of watery juice, to
two ounces, or two and a half, of starch. "When examined by the
Yia. 102. microscope, the tissue of the potato is found

to consist of a mass of cells, containing starch
grains. Each cell contains some 10 or 12
grains, loosely situated, as shown in Fig. 102,
and surrounded by the potato juice, which
contains albumen. If potatoes be of good
quality, they boil dry, or mealy ^ as it is term-
ed. But their water or juice does not sepa-
rate, or boil out. It is absorbed by the starch
Starch grains of potato before grains, which form a compound with it, and
°' swell up so as completely to fill, and even

burst the cells, as seen in Fig. 108. The albumen at the same time
coagulates, so as to form irregular fibres, which are seen among the
starch grains. When the juice of the potato is
only partially absorbed by the starch, it is said to be
watery, waxy, or doughy. Potatoes by boiling in
water do not form a jelly, like common starch, be-
cause the starch grains in the tubers are protected,
partly by the coats of the cells in which they are
contained, and partly by the coagulated albumen.
"Potatoes steamed or roasted — or if boiled, mash-
ed so as to extract all hard lumps, are in the best
condition for digestion. Frying them, toasting
Btarch grains of potato them, baking them, or broAvning the surface, dries
ater oi ing. ^^ ^^^ starch into a hard, half-charcoally mass,
which, except in most powerful stomachs, must act as a foreign body."
533. Quality of the Water for Culinary Pnrposes. — Soft water, or that
which is free from dissolved mineral matter, makes its way into, or is
imbibed by organized tissues, with much more readiness and facility
than hard water. It also exerts a more powerful solvent or extractive
action, and thus is a better vehicle for conveying alimentary sub-

FiG. 108.

HOW COOKESTG CHANGES MEAT. 281

stances into the living system. In culinary operations where the
object is to soften the texture of animal and vegetable matter, or to
extract from it and present in a liquid form some of its valuable parts,
as in making soups, broths, stews, or infusions, as of tea or coffee, soft
water is the best. But there are cases in which the solvent action of
soft water is too great, as sometimes upon green vegetables, which it
makes too tender, destroying the firmness that is essential to the
preservation of their juices, which are dissolved and extracted, making
the substance proportionately tasteless. In those cases, therefore,
when we do not desire to dissolve out the contents of a structure, but
to preserve it firm and entire, hard water is better than soft. To pre-
vent this over-dissolving action, common salt is often added to soft
water, which hardens it. This fact also explains why it is impossible
to correct and restore the flavor in vegetables that have been boiled
in soft water by afterwards salting them. It is weU known that peas
and beans do not boil soft in hard water. This is owing to the efiect
which salts of lime, especially the sulphate or gypsum, exert in hard-
ening or coagulating casein which abounds in these seeds. Onions
furnish a good example of the influence of quality in water. If boiled
in pure soft water, they are almost entirely destitute of taste ; though
when cooked in salted water, they possess in addition to the pleasant
saline taste, a peculiar sweetness, and a strong aroma ; and they also
contain more soluble matter than when cooked in pure water. The
salt hinders the solution and evaporation of the soluble and flavoring
principles.

8. How CooKiNa changes Meat.

534. Action of Heat upon the Constitncnts of Flesh.. — If the pure fibrin
of meat is exposed to a moderate heat, it parts with a large portion of
its water, which it held like a sponge, and loses the power of taking
it up again. It consequently shrivels and shrinks. If the heat be
carried high, further decomposition and charring take place. The eflfect
of boiling upon fibrin, is not to make it more tender, but to increase its
hardness and toughness. A low degree of heat changes liquid albumen
to the solid condition ; altering remarkably aU its physical properties.
It neither dissolves in water, hot nor cold, and is impenetrable to it.
If diffused through one or two hundred times its weight of water, it
coagulates, forming fine fibrous meshes throughout the liquid sufficient
to entangle any mechanical substances that may be floating in it, and
bring them to the surface or carry them to the bottom. In this way
albumen is used as a clarifying agent. If its proportion be much

282 CULINAET CHANGES OF ALIMENTABT SUBSTAKCES.

larger, the entire water may combine with it and pass into the solid
state. The egg, for example, contains 74 per cent, of water and 10 of
oil, yet its contents are all solidified by boiling through the action of
14 per cent, of pure albumen. Fat is liquefied, of course, by the action
of heat, and at a high temperature it is resolved into various acid and
acrid bodies. The effect of heat upon flesh in the mass, has been in-
vestigated by LiEBiG, with his usual acuteness and with highly inter-
esting and practical results.

535. Properties of the Liquid and Solid parts of Flesh. — When mus-
cular flesh or lean meat is chopped fine, and steeped or leached with
cold water, there remains a solid residue consisting of the muscular
fibres, tissues, vessels, &c. If this be boiled, it is tasteless, or indeed
slightly nauseating ; it cannot be masticated, and even dogs reject it.
All the savory constituents of the flesh were contained in its juice ;
and were entirely removed by cold water. The watery infusion thus
obtained, is tinged red by some of the coloring matter of the blood.
~ If it be boiled, this coloring matter separates, leaving the liquid clear
and of a pale yellowish color. This liquid has the aromatic taste,
and all the properties of soup made by boiling the flesh. When
evaporated and di-ied, a soft brown mass amounting to 12 or 15 per
cent, of the weight of the original dry flesh is obtained, having an
intense flavor of roast meat. This extract of flesh is soluble in cold
water, and when dissolved in about 32 parts of hot water, with salt,
it gives to this water the taste and all the properties of an excellent
soup. The liquid extract retains the peculiar taste of the flesh from
which it was derived; so that if we add the concentrated juice of
venison or fowl to exhausted beef, the latter at once acquires a venison
or fowl taste,

536, Loss of Weight ia Cookiag. — The first effect of applying a
strong heat to a piece of fresh meat, is to cause the fibres to contract,
to squeeze out a portion of the juice, and partially to close the pores so
as to prevent the escape of more. Heat is applied to meats chiefly in
three ways, 'boiling^ roasting^ and laTcing. During these operations,
fresh beef and mutton, when moderately fat, lose on an average
about as follows :

In boiling. In baking. In roasting.

4 lbs. of beef lose 1 lb. 1 lb. 3 ozs, 1 lb. 5 ozs.

41bs. of mutton lose 14 ozs. lib. 4 ozs. 1 lb, 6 ozs.

The greater loss in baking and roasting, arises chiefly from the greater
quantity of water evaporated, and of fat which is melted out during
these two methods of cooking.

537. Best method of cooking Meat. — In preparing meat for the table,

HOW COOKING CHANGES MEAT. 283

we sliall discover it to be most desirable that the ingredients
of its juice should remain in it; and this wiU depend much upon
the method of culinary procedure. If the piece of meat be in-
troduced into the water when IrisMy foiling, the albumen at its
surface, and to a certain depth inward, is immediately coagulated;
thus enclosing the mass in a crust or shell which neither permits its
juice to flow out, nor the external water to penetrate within, to dis-
solve, dilute, and weaken it. The greater part of the sapid consti-
tuents of the meat are thus retained, rendering it juicy and well-
flavored. It should be boiled for only a few minutes, and then kept
for some time at a temperature from 158° to 165°. Meat is under-
done or bloody, when it has been heated throughout only to the
temperature of coagulating albumen (140°) ; it is quite done or cooked,
when it has been heated through its whole mass to 158° or 165°, at
which temperature the coloring matter of the blood coagulates. As
in boUing, so in baking or roasting ; for whether the meat be sur-
rounded by water, or in an oven, as soon as the water-proof coating
is formed around it, the further changes are effected alike in both
cases, by internal vapor or steam. In roasting or baking, therefore, the
fire should be at first made quite hot, until the surface pores are com-
pletely plugged, and the albuminous crust formed. Hence, a beef-
steak, or mutton-chop, is done quickly over a smart fire that the richly-
flavored natural juices may be retained.

539, Objection to the common method. — The fibrin of meat, in its
natural state, is surrounded by an albuminous hquid. In coagulating,
it becomes firm and hard, but at the same time, brittle and tender.
If the albumen be coagulated within the meat, it forms a protective
sheath around the fibres, and thus prevents them from being shrivelled,
toughened, and hardened by boiling. This explains why the flesh of
young animals, which is richer in albumen than that of old ones, is
also more tender. If the meat be placed in cold water, and the
temperature slowly raised to boiling, a portion of the savory and
nutritive juices is dissolved out, and the meat becomes proportion-
ally poorer for the loss. At the same time the fibres lose more or
less of their shortness, or tenderness, and become tough. The smaller
or thinner the piece of fiesh is, the greater is its loss of savory con-
stituents. If, in baking, the meat be exposed to a slow fire, its pores
remain open, there is a constant escape of juice from within, and the
flesh becomes dry and unsavory.*

* The flesh of old animals often yields no more than 1 or 2 per cent, of albumen, that
of young animals as much as 14 per cent — Liebig.

284 CULrfiTAET CHAISTGES OF ALIMENTARY SUBSTANCES.

540. Soup, Beef-tea, Mntton-broth, &c. — In the i)reparation of these
our object is the reverse of that which has just been considered. We
desire to take the nutritive and savory principles out of the meat, and
get them into a hquid or sokible form. To obtain a liquid extract of
meat, in the form of soup, broth, or tea, the flesh is finely chopped
and placed in cold water^ vphich is then slowly heated and kept boiling
for a few minutes, when it is strained and pressed. In this manner
we obtain the very strongest and best flavored soup which can be
made from flesh. " When one pound of lean beef, free of fat, and sepa-
rated from the bones, in the finely-divided state in which it is used for
beef-sausages or mince-meat, is uniformly mixed with its own weight
of cold water, slowly heated to boiling, and the liquid after boiling
briskly for a minute or two is strained through a towel from the coag-
ulated albumen and fibrin, now become hard and horny, we obtain an
equal weight of the most aromatic soup of such strength as cannot be
obtained, even by boiling for hours, from a piece of flesh." — (Liebig.)
To make the best article, it is desirable not to boil it long, as the ef-
fect is to coagulate and render insoluble that which was extracted by
cold water, and which should have remained dissolved in the soup. It
is obvious from what has been said, that a piece of meat introduced
undivided into boiling water, is in the most unfavorable condition pos-
sible for making good soup. It is customary in soup-making to pro-
tract the boiling for the purpose of thickening and apparently enrich^
ing the soup. This is efiected by the gelatin, which is gradually
extracted from the tissues, bones, and other parts, but in a nutritive
point of view this ingredient is a fiction, as will be shown in the proper
place (717). Soup-making is a kind of analysis of alimentary sub-
stances used in its preparation — a part is taken, and a residue usually
rejected. Yet it is clear that we shall have the completest nourish-
ment by taking both parts, as the fibre of meat and the softened beans
and peas of their respective soups.

541. A new Broth for Strengtliening the Sict. — In certain maladies (as
typhus fever, for example, at particular stages), the greatest difiiculty
met with by the physician, lies in incomplete digestion, or inability
promptly to reinforce the exhausted and bankrupt blood. To meet
this difficulty Liebig prepared, as follows, a nutritive liquid, which
has been used at Munich with the best results. Take half a lb. o^ per-
fectly fresh meat (beef or chicken), cut it in small pieces, add to it Ij
lb. of distilled (pure soft) water, with four drops of muriatic acid, and
half a drachm of common salt ; mix the whole well together, and after
standing an hour, strain through a common hair sieve, letting it pass

PEEPAEATION AJSTD PROPEETIES OF BUTTER. 285

without pressing or squeezing. The portion passing through first be-
ing cloudy, it is again poured through the sieve, and this process is
repeated until it becomes perfectly clear. Upon the residue of meat
remaining in the sieve, half a pound of distilled water is poured in
small portions. In this manner a pound of cold extract of meat is ob-
tained, of a red color, and pleasant meat-broth taste. It must not be
heated, and is administered cold, by the cupful, according to the pa-
tient's inclination. It is difficult to make it in summer, on account of
its liability to ferment and change. Perfectly cold vrater must be
used, and refrigeration with ice wiU guard against decomposition,

9. Peepaeation and Peopeeties of Buttee. ii^

542. Actiou of Heat npon Milk and Cream. — The gradual heating of
milk facilitates the rising of its cream. The oil globules are broken,
liquefied, run together, and ascend to the upper part of the vessel.
There is always a trace of albumen in milk ; when boiled this is coag-
ulated and rises to the surface with oil globules, and forms there a
pelicle or skin, which is increased by evaporation. The layer thus
formed prevents the escape of steam, causing the liquid to boU over
if the vessel is not removed from the fire. If cream be heated for
some time nearly to boiling, its fat-globules melt together and collect
upon the surface, as a fluid oil. When this is cooled it forms a very
pure butter, which will keep long without being salted or becoming
rancid, but has neither the fine flavor nor the firm consistence of
churned butter.

543. Butter separated mechanically. — If either milk or cream be beat-
en or agitated mechanically for a time, the oil globules coalesce and
form a mass of butter. It is believed that each little fat-globe is en-
closed in a thin film of casein, which is ruptured by agitation. How-
ever this may be, the oil-cells have sufficient resistance to require
considerable mechanical violence to break them up, which is effected
by churning. During this operation oxygen is absorbed from the air,
the temperature rises, the cream or mUk, if not already acid, turns
sour, and gases are set free, which escape from under the cover, or
when the churn is opened.

544. Rate of Motion in Chnrnuig. — In churning cream, which is usu
ally thick and uneven, the agitation should at first be slow, until it has
become completely broken into a uniform mass. As it becomes thin-
ner the motion is easier and may be slightly increased, and continued
until a change in the §opnd from a low and smooth to a harsh tone is

286 CULINAEY CHANGES OF ALIMENTAKY SUBSTAJSuJiS.

observed. It may then be again slightly increased, nntil the bntter
Degins to form, when it is collected or 'gathered' by a slower move-
ment. If the rate of motion in churning is too rapid, the cream is
liable, especially at high temperatures, or in hot weather, to lurbt^ as
it is called, while the butter is soft, frothy and bad.

545. Time and Temperature. — "With different churns, and at dif-
ferent rates of speed, butter may be produced in from 10 minutes to 3
or even 5 hours. Dr. Muspeatt assigns from 45 minutes to an hour as
the best time for cream, while Prof. Ayton states for cream an hour
and a half, and for whole milk from two to three hours. Dickenson
says it is no matter if we are six hours in churning sweet milk. It
is, however, the well established result of experiment, that the more
quickly milk or cream is churned, the paler, softer, and poorer is the
butter. It is said also that in over-churning, that is, when the opera-
tion is too long continued after the butter is produced, it is apt to
be softened and lightened in color, although the quantity may be
somewhat increased. We have had frequent occasion to notice the
controlling influence of temperature over the changes of matter, and
we find it again illustrated here. Cream, when put into the churn,
should never be wai'mer than 53° to 55°. It rises during churning
from 4° to 10°. Johnston states that when the whole milk is churned,
it should be raised to 65°. The careful regulation of the temperature
is of the first importance, so that a thermometer is indispensable to
the proper management of the operation. Some churns have them
attached, which is an excellent plan. The temperature of the cream
is increased or diminished by mixing with hot or cold water, but many
strenuously object to this. In some churns there is an outer chamber
or vessel, which is separated from the cream by a thin sheet of metal,
through which heat or cold readily passes from water contained in the
chamber. This is a good arrangement, although the metal commonly
used {zinc) is not quite free from objection (611).

546. Compositiou and properties of Butter. — The mass of butter is a
tasteless and inodorous fat ; its pleasant aromatic flavor being due to
a compound existing in it in very small quantity, namely, hutyric acid,
combined with oxide of li2Jyle. First quality butter has a pleasant
peculiar aroma, is of a fine orange-yellow color, solid, and of a waxy
or grained texture, exposing a different surface when cut from fat or
grease. This granular quality results from the peculiar mode of its
production, which is by the mechanical coherence of minute butter-
particles or grains. Were butter separated like lard, by melting, it
would not present this appearance. Between good ordinary butter

PEEPAEATION AND PEOPEETEES OF CHEESE. 287

and a first-rate article there is a wide difference ; the former is com-
mon, the latter is but rarely seen. Cream and butter are both highly-
absorbent of unpleasant odors, and are extremely susceptible of taint
from this cause. The air of the dairy -house must be " sweet as that
wafted from the rose itself. A common farm cellar with meat, fish,
and vegetables, would spoil the best package of butter ever made in
sixty days." The cows should be kept on rich, tender, high-flavored
grasses, — timothy, white clover, blue grass, red-top, with which the
ground is to be thickly swarded over to protect it from sun and
drouth. May, June and September are the best months, July and
August being too hot ; while after frost appears, the grass becomes
insipid and bitter, and will not yield butter of the best quality.
Almost every kind of butter, however, is good when newly made.
The vital considerations of its manufacture are connected with its
quality of keeping, which will be noticed when we reach the subject
of preservation (599).

10. Peepaeation and Peopeeties of Cheese.

547. Spontaneons Cnrdling of Milk. — When milk is left to itself for a
time, which is shorter in warm or stormy weather, it sours and
curdles, that is, its casein changes from the dissolved to the solid state.
This is brought about by a series of interesting and beautiful changes
originating in the unceasing activity of atmospheric oxygen. Casein,
in itself, is insoluble in water. But it is of an acid nature, and is ca-
pable of combining with potash or soda, and forming a compound
which dissolves in water. Soda is the alkali which holds the casein
of milk in solution. Now when fresh milk is exposed to the air, its
oxygen acting upon a portion of the nitrogenous casein, changes it to
a ferment ; and this takes effect upon the milk sugar, converting it
into lactic acid, which causes the sourness of milk. "When sufficient
of the lactic acid is thus formed, it seizes upon the soda, takes it away
from the casein, and forms lactate of soda. The casein thus set free
shrinks in bulk, and gathers into an insoluble, curdy mass, the opera-
tion being aided by a gentle warmth.

548. Artificial Curdling with Acids. — In making cheese the milk is
curdled artificially, and in different countries various substances are
used for this purpose. But they all produce the effect in precisely the
same way, that is, an acid substance is employed to neutrahze the
soda of the milk, by which the casein assumes the coagulated state.
Almost any acid will have the effect of curdling milk. Muriatic acid,
weakened with water, vinegar, tartaric acid, cream of tartar, lemon
juice, and sour milk, are each used for the purpose.

288 CULnfAKY CHAISTGES OF AUMENTARY SUBSTAN-CES.

549. Artificial Cardling with Rennetf — The salted and dried stomacli
of the unweaned calf, lamb, or pig, is called rennet. If a small piece
of this be soaked in water for a time, and the infusion be mixed with
milk at a temperature of 90° or 95°, curdling shortly takes place. It
was once supposed that it is the acid of the gastric juice of the stomach
which produces the change ; but this cannot be, as the membrane acts
with equal promptitude, though it has been thoroughly washed free
from every thing of an acid nature. The change is due to the action
of the animal matter itself. It is said that the rennet should never be
■used unless ten or twelve months old. During this period, by exposure
to the air, a portion of the membrane has undergone decay and become
soluble in water. This decomposing animal matter acts upon the
sugar of milk, changing it to lactic acid, which produces curdling ex-
actly as in spontaneous coagulation (547). There is much about the
action of rennet that is not yet explained. Its condition seems to
exert a decided influence on the quality of the cheese. The result im-
probably much influenced by the state of decay of the animal matter,
as the decomposition may be so far advanced as to induce putrefaction
in the milk.

550. Conditions of the preparation of Cheese. — By the action of curd-
ling agents the milk is divided into two parts ; first the curd, com-
prising all the casein, a large portion of oil and a ti-ace of sugar of
milk, with some water ; and second, the wJiey or fluid part containing
the bulk of water, the sugar of milk, and a small but variable propor-
tion of oily matter. Of the saline matter in milk, the phosphates of
lime and magnesia exist in the curd, vvhile the remaining salts are
found in the whey. The curd, separated from the whey and prepared
in various ways, and then pressed, forms cheese. The properties of
cheese are influenced by a great number of circumstances. Pure
casein makes a cheese poor, hard, and horny. The admixture of the
oil or cream of the milk enriches it in proportion to its quantity. The
most inferior cheeses therefore are made from milk that has been re-
peatedly skimmed and deprived of all its oil, while the richest cheeses
are those made directly from cream (cream cheeses), and which hence
contain an excess of oily matter. Between these extremities there
are all grades of quality, which depend upon the proportion of the
constituents. Thus if we use the new milk of the morning, mixed
with the previous evening's milk that has been deprived of its cream,
we get a cheese of a certain quality ; if we use the tcTiole milJc of the
previous night, the cheese will of course be better ; and if we use only
the cream of the previous evening's milk, the cheese will be still

PEOPEETIES AND PEEPAEATION OP TEA. 289

richer. All tlie conditions wliicli influence the properties of the milk
itself (334) affect also the quality of the cheese. The heat, in curd-
ling, should not be too high, as it is apt to give excessive oiliness to
the fatty portion of the milk. A thermometer affords more reliable
indications than the sense of feeling. As soon as coagulation is com-
plete, the curd should be separated, as the longer it stands the harder
and tougher it is. Much judgment is required to know the proper
quantity of rennet to be used ; if there is too little, the process is too
slow, and time is given for the butter to separate itself fi'om the curd,
while too much rennet makes the curd tough, and otherwise affects
disagreeably the subsequent changes and flavor of the cheese. The
mode of separating the curd from the whey, its subsequent prepara-
tion, and the degree and duration of the pressure applied, together
with a great variety of other circumstances known to the skUfuI
cheese-maker, have a powerful influence upon the quality of the arti-
cle produced. We shall refer to cheese again when speaking of preser-
vation (604).

IV.— COMMON BEVERAGES.
1. Peopeeties and Peepaeation op Tea.

551. The Tea Shrub, — Tea consists of the prepared leaves of the
tea-plant, a hardy shrub which grows from 3 to 6 feet high, chiefly in
China. The plant is propagated from the seed, and matures in from
two to three years, yielding usually three crops of leaves each season.
"When a year old, the young bushes are planted out in rows 3 or 4
feet apart, and being cropped down so as to grow thick and bushy, the
tea-field resembles a garden of gooseberry bushes. The leaves are
picked by hand in May and June, and the plant yields leaves from
four to six seasons.

552. What causes different Tarieties of Tea. — Many varieties of tea of
all grades of quality are known in market. These differences depend
first upon the soil, climate, culture, &c., of the locality where it is
grown. Second^ upon the time of picking ; the young unexpanded
leaves that are gathered first being tender and delicate, while the sec-
ond and third gatherings are more bitter, tough, and woody. Tliird^
the mode of treatment or preparation, which consists in drying, roast-
ing, and rolling in the hand, by which the leaves acquire their twisted
appearance, and finally sifting and winnowing. The methods of hand-
ling are various, and much depends upon them.

558. Difference between Green and Black Teas. — All the different
varieties of tea are classed as either green or hlach. What constitutes
13

290

COMMON BEVERAGES.

GREEN TEA.

1. Cultivated in manured soils.

2. Leaves are steamed, 'witliered and
roasted almost immediately after gather-
ing.

8. They are dried quickly after the
rolling process ; the whole operation being
brief and simple.

the real difference between these two sorts has long been a matter of
doubt. It was at first supposed that they came from totally different
species of plants ; but the latest accounts agree that they are both de-
rived from the same plant, the difference being in conditions of growth
and modes of dealing with the leaves. They may be thus contrasted :

BLACK TEA.

L Grown chiefly on the slopes of hiUs
and ledges of mountains.

2. Allowed to be spread out in the air
for some time after they are gathered.

8. They are tossed about until they be-
come soft and flaccid.

4. They are now roasted for a few min-
utes, and rolled.

5. They are exposed to the air for a few
hours in a soft moist state.

6. Lastly, they are dried slowly over
charcoal fires.

It is by lengthened exposure to the air in the process of drying, ac-
companied perhaps by a slight heating and fermentation that the dark
color and distinguishing flavor are given to the black teas of com-
merce. The oxygen of the atmosphere acts rapidly upon the juice of
the leaf during this exposure, and changes chemically the peculiar
substances they contain, so as to impart to the entire leaf the dark
hue it finally acquires. The precise nature of these changes has not
been chemically investigated. — (Johnston.) The unchanging green
color of green teas is produced, says Knapp, by employing steam to
wither the fresh leaves, it being well known to collectors of plants,
that many which inevitably turn black when simply dried, preserve
their green color brilliant and permanent, when they are killed by
steam, previously to drying. The same authority remarks, that green
tea gives up much less of its juice in the drying process ; a circum-
stance which fully explains its more energetic action upon the nervous
system.

554. Varieties of Green and Black Tea. — The most important teas of
commerce may be thus arranged, beginning with the lowest qualities.
Annexed is an approximative scale of the prices per pound paid for
them in Canton.

Green Teas.

Twangay 18 to 27 cts.

Hyson Skin 18 to 80 "

Young Hyson 27 to 40 "

Hyson 40 to 56 "

Imperial 45 to 58 "

Gunpowder 45 to 60 "

BlBck Teas.

Bohea 12 to 18 eta.

Congou 22 to 25 "

Campoi 22 to 30 "

Souchong 20 to 85 "

Caper 20 to 40 "

Pekoe 85 to 75 "

PEOPERTIES AND PEEPAEATION OF TEA. 291

Ticangay is the coarsest and most inferior of the green teas. The
Hysons are of a better quality, and are more widely used. The word
' Hyson ' is derived from Hee-chun, the name of a celebrated Chinese
tea-maker. Hyson-skin is composed of the light, inferior leaves, sepa-
rated from Hyson by winnowing. Young-Hyson^ Hyson, and Impe-
rial, consist of the second and third crops; while Gunpowder, the
finest of the green teas, consists of the first leaves, or leaf-buds, of
the vernal crop. It is called 'gunpowder,' from the fancied resem-
blance of its small rounded leaves to gunpowder grains. Bohea is the
poorest and cheapest of the black teas, and takes its name from being
largely produced on the Bohea mountains ; Congou, from cong-fou,
' made with care,' and Souchong, from se-ou-chong, " a very little
sort," are better varieties. Gaper comes in little balls or grains, made
up in the form of capers. Pekoe is the best of all the black teas, and
corresponds to gunpowder among green teas. The word ' Pekoe,' or
Pak-Ho, means ' white down,' and is applied to the first downy leaves
of the spring growth. It is often called the Flowery Pekoe, which is
erroneously supposed to refer to the blossom of the tea-plant ; but the
tea flower itself has little fragrance, and although sometimes used in
China, is not imported.

555. Composition of Tea. — The analysis of tea shows it to be com-
posed of four principal constituents. First, an aromatic, volatile oil,
which produces the peculiar odor and flavor. It is of a citron yellow
color, floats on water, and when exposed to the air is quickly convert-
ed into a solid resin by atmospheric oxygen. It has such a powerful
taste, that when placed on the tongue it spreads over the entire throat,
and exerts a painfal action upon the nerves. It does not exist in the
fresh or natural leaves, but is produced during the roasting process.
A hundred pounds of tea yield only a single pound of the oil. Second,
tea contains a peculiar principle called thein, a substance rich in nitro-
gen, and classed among 'vegetable alkalies. Stenhottse states that or-
dinary tea contains about two per cent, of thein; but Peligot has
found as much as 6 per cent, in certain green teas, although this quan-
tity is very unusual. Thein has a slightly bitter taste, no smell, and
dissolves in hot water. An infusion of tea, therefore, contains dis-
solved thein : and if the leaves be of good quality, an ounce will yield
about 10 grains. Third, tannin or tannic acid, a substance so named
because it is the ingredient in oak and hemlock bark, which combines
with leather in the operation of tanning. If a compound of iron (sul-
phate of iron — copperas, for example), be introduced into an infusion of
tea, it turns it to an inky blackness, by precipitating its tannic acid.

2^2 COMMON BEVEEAGES.

This substance is a po-werful astringent, and gives to tea its astringent
taste and properties. It forms from 12 to 18 per cent, of the weight
of tea. When tea is steeped, the three foregoing constituents are com-
Jmunicated to the water; they hence give its active properties to the
ordinary beverage. But tea leaves contain, fourthly, another constit-
uent, namely, gluten — which, not being dissolved by hot water, is
usually lost with the dregs or grounds. The proportion of this sub-
stance is stated to be as high as 25 per cent., so that the leaves, after
exhaustion by steeping, are still highly nutritive. In some localities
it is customary to eat them.

556. How Tea is best made. — The Chinese method is to throw some
tea into a cup, and pour boiling water over it ; they cover the cup
with a shallow saucer, and let it rest for some time. After it has
stood sufficiently long, they pour the clear liquid into a saucer, and
drink it hot. Various methods are pursued in different countries, but
a knowledge of the composition and properties of tea is the best guide
in preparing its infusion. It is desirable to obtain from the leaves the
largest possible amount of matter which water wiU extract, and retain
them in the liquid. The thein of tea is in combination with tannic acid,
forming a compound which requires boiling water to dissolve it. But,
on the other hand, the aromatic oil of tea is volatile, so that the boil-
ing tends to drive it off with the steam into the air. If lukewarm
water is used, the most important element of tea, its thein, is not ob-
tained ; while, by boiling, its fragrant aroma is wasted. The plan to
be pursued, therefore, is to pour boiling water upon the tea, in close
vessels, so that its active ingredients may be dissolved, and at the same
time the volatile oil retained in the mixture. In cooling, a good de-
coction of tea becomes slightly turbid, the tannate of thein being no
longer held in solution, is precipitated and rises, forming a skin upon
the surface,

557. What remains in the Grounds, or residne. — If tea be steeped in
water below the boiling temperature, an infusion is obtained, having
the peculiar tea-taste, but the thein is not obtained ; a second infusion
of the leaves with boiling will extract the thein, and tannic acid,
60 that, although it may be less fragrant, it will be more active. The
leaves which have been used of course vary in composition, according
to the completeness of the first exhaustion. By the common method
of extraction, the entire quantity of thein is never dissolved, about
one-third being left in the leaves. Mulder found hot water to ex-
tract from six specimens of black tea, from 28 to 38 per cent, of their
weight ; of the same number of kinds of green tea, from 34 to 46 per

PKOPERTIBS AND PEEPAEATION 01" COFPKB. 293

cent. Peligot procured from black tea an average of 38 per cent.,
and from green, 43 per cent. Yet the quantities are by no means con-
stant, as different samples of the same color and name ia the market
yield very different proportions of soluble matter. Teas prepared from
young leaves furnish more soluble matter than the older leaves ; while
green teas give more of light-colored, and black of dark-colored ingre-
dients. The gluten, in which tea leaves are rich, is not dissolved by
boding water ; but water made slightly alkaline dissolves gluten. It
has therefore been recommended that a little soda be added to the
water, which would have the effect of making the tea slightly more
nutritious.

558. Adulterations of Tea. — Teas of aU sorts are liable to the grossest
adulterations. The green teas are extensively stained or painted by
the Chinese, to heighten their green color. For this purpose they use
Prussian blue, indigo, turmeric, gypsum, and Ohina-clay. With these
ingredients they glaze or face the surface of the leaves, to such an ex-
tent, that it is affirmed we nevier get pure green tea. Other leaves are
also often mixed with those of the tea-plant, by the Chinese. In Eng-
land, the leaves of the sloe and thorn are much mixed with tea. The
Chinese also make a crude and worthless preparation of sweepings,
dust, sand, leaves, and various impurities of the tea warehouses, cement-
ed with gum or rice-water, which they honestly call lie-tea^ and employ
it extensively to mix with other teas. In England, exhausted leaves
are bought up, their astringent property restored by the addition of
catachu (a concentrated tanning extract), and colored with black lead,
logwood, &c., are sold again as genuine tea. Another fraud of great
prevalence consists in mixing inferior qualities of tea with the better
sorts, and cheating the purchaser by selling the compound at the price
of the best article. To detect indigo or Prussian blue in tea, let a por-
tion of it be shaken with cold water and thrown upon a bit of thin
muslin, the fine coloring matter will pass through the muslin, and
settle to the bottom of the water. When the water is poured off, the
blue matter may be treated with a solution of chloride of lime. If it
is bleached, the coloring matter is indigo. If potash makes it brown,
and afterwards a few drops of sulphuric acid make it blue again, it is
Prussian blue. — (Johnston-.)

2. Peopeeties and Preparation of Coffee.

559. The Coffee Tree and its Seeds. — Coffee is the product of a plant,
grown extensively in warm climates. The natural height of the tree,

294 COMMON" BEVERAGES.

varies from 10 to 30 feet ; but it is usually pruned down to 5 or 6 feet,
to increase the crop of fruit. All are familiar -witli the structure
of coffee seeds ; they are of an oblong figure, convex on one side,
and flat, with a little straight furrow, on the other. They are en-
closed in a pulpy berry of a red color, which resembles a cherry, and
are situated within it with their flat sides together, and invested by a
tough membrane called the parchment. The seeds are separated by
fermenting the berries, crushing them under heavy rollers, drying,
grinding, and winnowing.

560. Varieties of Coffee. — The best coffee is the Arabian; that
grown in the province of Mocha {Mocha coffee) is of the finest quality.
It may be known by having a smaller and rounder berry than any
other, and likewise, a more agreeable smell and taste. It is of a dark
yellow color. The Ja'oa and Ea^st Indian coffees are larger and of a
paler yeUow, while Ceylon^ West Indian, and Brazilian coffees are of
a bluish or greenish gray tint.

561. Composition of Coffee. — The raw coffee, as it comes to market,
is but slightly aromatic ; its odor is faint, while its taste is moderately
bitter and astringent. In this state its composition, according to
Paten, is as foUows :

Water 12

Gum and Sugar 15'50

Gluten 13

Cafein 00T5

Fat and Volatile Oil 13

Tannic Acid 5

Woody Fibre 34

Ash 6-75

Dr. Stenhouse states that it contains 8 per cent, of cane sugar. Oof-
fee, it vrill be seen, contains tannin, the same astringent principle aa
tea, but in much smaller proportion ; and the substance itself is of
a somewhat different chemical nature. They both contain much
gluten ; but the most remarkable point of similarity between tea and
coffee, is found in the fact, that the cafein of coffee is a vegetable
alhali, with the same composition and properties as thein of tea. A
direct analysis of the two substances gave the following result :

Carbon. Nitrogen, Hydrogen,- Oiygen,

Thein 50-1 29-0 5-2 15T

Cafein 49-8 28-8 5-1 16-2

The proportion of cafein in coffee is probably somewhat higher
than the preceding analysis indicates. It is of course variable ; but
is about half that of thein in tea (555). Coffee, however, is not used

PEOPERTIES AOT) PEBPAEATION OF COFFEE.

295

Fia. 104

in the raw or natural state; like tea, it is first altered by heat or
roasted.

562, Effects of roasting Coffee.—

The operation of roasting, produces
several important changes in coffee.
In the first place, the raw coffee-
berries are so tough and horny,
that it is very difficult to grind, and
pulverize them sufficiently fine, that
water may exert its fuU solvent
effect upon them. Boasting ren-
ders them yielding and brittle,
so that they may be more readily
ground ; while, at the same time, it
increases the amount of matter so-
luble in hot water. If we examine
the raw coffee seed with the micro-
scope, it will be found to consist of
an assemblage of cells, in the cavi-
ties of which are seen small drops
of the aromatic volatile oil of cof-
fee. This appearance is shown in
(Fig. 104). K now we place a
fragment or section of roasted cof-
fee under a magnifier, it wUl be
observed that these drops of oD.
in the cells are no longer visible
(Fig, 105). They have, in part,
been dissipated by the heat, and
in part, become more generally dif-
fused throughout the mass of the
seed; a portion being driven to the
surface. It is obvious, that roasting
produces certain chemical changes
in coffee, which alter its flavor and

taste, and bring out the peculiar 'Oi'^^^^^^^
and highly esteemed aroma for YJ'ts

^ i . 1 ,■,. 1 • T i." • T. Appearance of roasted coffee berries.

which this beverage is distinguish-

ed. Johnston states that the peculiar aromatic principle which gives
flavor to coffee, exists in extremely minute quantity, (one part in fifty
thousand,) and is generated in the roasting process. The heat also

Appearance of nnroasted coffee-berries
magnified, showing the size and form of
the cells, and the drops of oil contained in
their cavities.

FiQ. 105.

-296 COMMON BEVEEAGES.

sets a portion of the cafein free from its combination with tannic
acid, and evaporates it. The temperature is suflSciently high to de-
compose the sugar, and change it to brown, burnt sugar, or caramel.
Coffee darkens in color during roasting, swells much in bulk, and
loses a considerable portion of its weight, by evaporation of its water
and loss of other constituents. Coffee roasted to a reddish Irown,
loses in weight, 15 per cent., and gains in bulk, 30 per cent. To a
chestnut trown, it loses 20 per cent, in weight, and gains 50 in
bulk. To a darTc irown, it loses 25 per cent, of weight, and gains
50 in bulk.

563. Hints concerning the Eoasting Process. — The roasting of coffee
is an operation of considerable nicety; more, perhaps, depending
upon it than upon the variety of the article itself. Coffee is roasted
by the dealers, in hollow iron cylinders or globes, which are kept
revolving over a fire. As the first effect is the evaporation of a consid-
erable amount of water, if the vessel be close this is retained, and the
coffee roasted in an atmosphere of its own steam. This is not thought
to be the best plan, and if the operation be carried on at home, it is
recommended that the coffee be first dried in an open pan over a
gentle fire, until it becomes yellow. It should then be scorched in
a covered vessel, to prevent the escape of the aroma ; taking care,
by proper agitation, to prevent any portion from being burnt ; as a
few charred grains communicate a bad odor to the rest. It is impor-
tant that just the right temperature should be attained and kept. If
the heat be too low, the aromatic flavor is not fully produced, and if
it be too high, the rich oily matter is dissipated, leaving only the
bitterness and astringency of the charred seeds. The operation should
be continued until the coffee acquires a deep cinnamon or chestnut
color, and an oily appearance, and the peculiar fragrance of the roasted
coffee is sufficiently strong. It may then be taken from the fire,
and allowed to cool without exposure to the air, that the aromatic
vapor may condense and be retained by the roasted grains. Coffee is
very apt to be over-roasted, and even a slight excess of heat greatly
injures its properties.

564. Effects of Time upon Coffee. — Coffee berries undergo a change
called ripening, by keeping; that is, they improve in flavor. The
Arabian coffee ripens in three years, and it is said that in ten or a
dozen years the inferior American coffees become as good, and acquire
as high a flavor as any brought from Turkey. — (Ellis.) But it is differ-
ent after the coffee is roasted and ground. Its flavoring ingredients
have a tendency to escape, and it should therefore be confined in ves-

PEOPEETIES AND PEEPAEATION OF COITEE. 297

sels closed from the air. It should not be exposed to foreign or dis-
agreeable odors, as it has a power of imbibing bad exhalations, by
which it is often injured. Many cargoes of coffee have been spoiled
from having been shipped ■with, or even put into vessels which had
previously been freighted with sugar. A few bags of pepper are suffi-
cient to spoil a whole ship-load of coffee. — (Noemandt.)

565. Mode of Preparing the Bercrage. — To prepare the coffee, it
should be roasted and ground just before using, no more being ground
at a time than is wanted immediately. Of course the finer it is re-
duced the stronger will be the extract from a given weight of coffee,
one-fourth more soluble matter being obtained from coffee ground to
the fineness of flour than from the ordinary coarse powder (Knapp).
If a cup of good coffee be placed upon a table, boiling hot, it will fill
the room with its fragrance. Its most valuable portion is thus liable
to be exhaled and lost. Hence the same difficulty is encountered as
in tea making ; boUing dissipates the much-prized aroma ; but a high
heat is necessary to extract the other important ingredients of the
coffee. It should therefore be steeped rather than boiled, an infusion,
and not a decoction being made. Some make it a rule not to suffer
the coffee to boil, but only to bring it just to the boiling point. Yet, a
few minutes' boiling undoubtedly increases the quantity of the dis-
solved, bitter, exhilarating principle. Dr. Donovan recommends that
the whole of the water to be used be divided into two parts, one half
to be put on the fire with the coffee, and, as soon as the liquor boUs,
taken off, allowed to subside for a few seconds, and then poured off as
clear as it wiU run. Immediately the remaining half of the water, at
a boiling heat, is to be poured on the grounds ; the coffee pot is to be
placed on the fire and kept boiling three minutes, and after a few mo-
ments' settling, the clear part is to be poured off and mingled with the
first. The mixture now contains a large share of the qualities of the
coffee, both aromatic and bitter.

566. Alkaline Water for Coffee-making. — It is observed, that some
natural waters give a stronger and better flavored coffee than others,
and this has been traced as in Prague, to the presence of alkaline mat-
ter in those which give the most agreeable infusion. Hence, to obtain
a more uniformly strong and well-flavored coffee, it is recommended
to add a little soda to the water with which the infusion is made.
About forty grains of dry, or twice as much of crystallized carbonate
of soda, are sufficient for a pound of coffee. — (Johnston.)

567. Adulterations of Coffee. — Ground coffee is very extensively
adulterated. Various substances are employed for this purpose, as

13*

298 COMMON BETEEAGES.

roasted peas, beans, and corn, and dried and roasted roots, sucli as tur-
nips, carrots, potatoes, &c. But the most common adulterant is cUccory,
a plant of the dandelion tribe, which has a large, white parsnip-like
root, abounding in a bitter juice. The root is mashed, sliced, dried,
and roasted with about two per cent, of lard, until it is of a chocolate
color. A little roasted chiccory gives as dark a color and as bitter a
taste to water, as a great deal of coffee ; and, costing only about one-
third ae much, the temptation is strong to crowd it into ground coffee.
So common has the use of chiccory with coffee, become, that it has,
in fact, created a taste for a solution of unmingled chiccory, as a bever-
age, although it is destitute of any thing corresponding to the cafein,
or exhilarating principle of coffee. As an illustration of the extent of
adulteration, and how one fraud opens the door to another, it is found
that pure chiccory is almost as diflBcult to be met with in market as
unadulterated coffee. Venetian red is employed to impart to it a true
coffee color, while brick dust is used by the painter to cheapen and
modify the shade of his Venetian red.

568. How the Cheats in Coffee may be Detected. — When cold water is
poured upon coffee the liquid acquires color only very slowly, and it
does not become very deep after prolonged soaking; even when
boding water is employed, the infusion, although somewhat deeper,
still remains clear and transparent. "When, however, cold water is
poured upon roasted and ground chiccory root, it quickly becomes of
a deep brown, and in a short time is quite opaque ; with boiling water
the result is still more prompt and marked. We may therefore detect
chiccory in a suspected sample of coffee by placing a little in cold
water. If it be pure the water will remain uncolored ; if chiccory be
present it will be strongly discolored. It may be remarked, however,
that if the coffee should be adulterated with burnt sugar, it will pro-
duce a similar coloration of the water. It may be further noticed that
particles of coffee float upon water, and, owing to their oiliness, are
not melted, while chiccory absorbs water and sinks. The admixture
of burnt and ground beans, peas, and grain, is not so readily shown.
The most certain method of detecting these is by microscopic exami-
nation.

3. CoooA AND Chocolate.

569. Source and Composition of Cacao Seeds. — These beverages are
prepared from the cacao beans, which are derived from a fruit resem-
bling a short, thick cucumber, grown upon the small cacao tree of the
West Indies, Mexico, and South America. The beans are enclosed in

COCOA AOT) CHOCOLATE. 299

rows, in a rose-colored, spongy substance, like that of tlie wateianelon.
When shelled out of this fleshy part, they are surrounded by a thin
skin or husk, which forms about 11 per cent, of their weight. The
cacao bean is brittle, of a dark brown color internally, cuts like a rich
nut, and has a slightly astringent, but decidedly bitter taste. In pre-
paring it for use, it is roasted, in the same way as coffee, until the
aroma is fully developed. The bean is now more brittle, lighter
brown in color, and less astringent and bitter than before. The fol-
lowing is its composition, according to Lampadius :

Fatty matter, 53-16

Albuminous brown matter, containing the aroma of the bean, 16-70

Starch, 10-91

Gum, 7-75

Lignin, -90

Eed coloring matter, 2-01

Water, 5-20

Lobs, 3-43

The largest constituent is a fatty substance, called 'butter of cacao^ of
the consistence of tallow, white, of a mild, agreeable taste, and not
apt to turn rancid by keeping. Cacao beans have also been found to
contain a substance, in minute proportion, not included in this analysis,
called theobromine a nitrogenous body, similar in nature and properties
to thein, of tea, and cafeine of coffee.

570. Forms of Preparation. — It is prepared in three ways. First.
The whole bean, after roasting, is beat into a paste in a hot mortar, or
ground between hot rollers. This paste, mixed with starch, sugar, &c.,
forms common cocoa, sold under various names, as ' rich cocoa, '
' flake cocoa,' ' soluble cocoa,' &c. These are often greatly injured
from the admixture of earthy and other matters, which adhere to the
husk of the beans. Second. The bean is deprived of its husk, and then
crushed into fragments. These form commercial cocoa nibs, the purest
state ia which cocoa can be obtained from the retail dealer. Third.
The bean, when sheUed, is ground at once into a paste by means of
hot roUers, mixed with sugar, and seasoned with vanilla, and some-
times with cinnamon and cloves. This paste forms chocolate. —
(Johnston.)

571. How these preparations are v&tA,— First, the chocolate is made
up into sweet cakes, sugar confectionery, &c., and is eaten in the solid
state as a nutritious article of diet, containing in a small compass much
strength-sustaining capability. Second, the chocolate or cocoa is
scraped into powder and mixed with boiling water, and boiling milk,
when it makes a beverage somewhat thick, but agreeable to the pal-

300 PEESERVATION OF AXIMENTART SUBSTAlSrCES.

ate, refreshing to tlie spirits, and highly nutritious. Third, the nihs are
boiled in water, with which they form a dark brown decoction, which,
like coflfee, is poured off the iasoluble part of the bean. "With sugar
and milk this forms an agreeable drink, better adapted for persons of
weak digestion than the entire bean. The husk is usually ground up
with the ordinary cocoas, but it is always separated in the manufac-
ture of the purer chocolates.

572. Adnlteration of Chocolate. — Pure or genuine chocolate should
dissolve in the mouth without grittiness, and leave a peculiar sensation
of freshness, and after boiling it with water, the emulsion should not
form a jelly when cold ; if it does, starch or flour is present. Many
of the preparations of the cocoa-nut, sold under the name of chocolate
powder, consist of a most disgusting mixture of bad or musty cocoa-
nuts, with their shells, coarse sugar of the very lowest quality, ground
with potato starch, old sea-biscuits, coarse branny flour, animal fats
(generally tallow). I have known cocoa-powder made of potato
starch moistened with a decoction of cocoa-nut shells and sweetened
with molasses ; chocolate, made of the same materials, with the ad-
dition of tallow and ochre, a coarse paint. I have also met with
chocolate in which brick-dust, or red ochre, had been introduced to
the extent of 12 per cent. — (Noemandt.) The temptation to fraud in
these preparations seems to be as irresistible as in the case of ground
coffee. There is no easy means of detection short of refined micro-
scopic and chemical examination, so that the only practicable means of
self-defence for the purchaser, is to deal only with traders of unques-
tionable integrity, where such can be found.

v.— PKESERYATION OF ALIMENTARY SUBSTANCES.
1. Causes of their Changeableness.

573. Why is it Necessary that Foods should he Perishable ? — As in the

plan of nature the production of force depends upon change of matter,
and as the fundamental purpose of animal life is the evolution of pow-
er, it is apparent that matter which is to act as food, must be capable
of ready and rapid transformation. This inherent facility of change,
by which alimentary substances are conformed to the deep require-
ments of the animal economy, renders them extremely transient and
perishable. If they are designed for change loitMn the body, they
must be subject to change without. In order that the gluten of flour,
for example, may pass readily through the successive changes of the
animal organism, being converted first into blood, then into muscular

CAUSES OP THEIE CHANGEABLENESS. 301

fibre, and then decomposed for the development of contractile force, it is
necessary that this substance should be so loosely buUt up, the attrac-
tions amongst its atoms should be so feeble, that slight causes become
capable of breaking down its chemical structure.

5T4. Change of Nntrient Matter withiu and without the Body. — ^It was
formerly taught that the living body is the domain of a peculiar vi-
tal power, which suspends the ordinary destructive play of chemical
aflBnities and physical forces, but that at death the vital energy ceases,
and those forces resume their natural activity, causing the speedy dis-
organization of the inanimate organism. But this is hardly correct.
The vital force, or whatever we may name the presiding agency of
the living system, does not suspend physical and chemical laws, but
only regulates, and as it were uses them. "We have already seen that
strictly chemical changes go on constantly in the body, and shall
shortly have occasion to notice their extent (624). They are of the
same kind {oxidations)^ are carried on by the same agent (atmospheric
air), and yield the same final products (carbonic acid, water and am-
monia), in both conditions. In the living fabric the decompositions
are measured ; while in the lifeless body they are uncontrolled, and
quickly spread through the entire organic mass.

575. Conditions of the Perishableness of Foods. — Alimentary substances
are by no means alike changeable ; some keep longer than others un-
der the same circumstances. There are certain specific causes of or-
ganic decomposition, and accordingly as these act conjointly, or with
variable intensity, is the rate of putrefactive change. In chemical
composition, vegetable and animal substances are much more compli-
cated than mineral compounds, and hence they are less permanent.
Generally, mineral substances are combined in the simplest and
most stable way, containing but few atoms, and consisting of pairs of
elements, with nothing to disturb their direct attraction for each other.
On the contrary, organized substances, in some cases, contain several
himdred atoms, and consist of three, four or five different elements,
joined by complex afiinities into delicate and fragile combinations.
We have seen, in speaking of fermentation, that albuminous substan-
ces are, from this cause, most changeable, and are universally present
in substances designed for food. Water is a large constituent of
all alimentary bodies, in their natural state, and is highly promotive
of chemical changes; indeed, it is indispensable to them. Tem-
perature exerts an all-controlling influence — warmth favoring, and
cold retarding, or arresting, these transformations. The atmospheric
medium, which is in contact with every thing, contains an element

302 PRESEEVA-TION OP AUMENTAET SUBSTAITCES.

whicli is the ever-active and eternal enemy of organization. The in-
satiable hunger of oxygen gas for the elements of organic substances,
is a universal cause of decomposition — it is the omnipresent destroyer,
consuming alike the li ving and the dead (662). Putrefactive decay may
also be prevented by certain chemical substances which are used for the
purpose. A knowledge of the laws and conditions of organic decom-
position, has led to various practical methods of controlling it, which
constitute the art of preserving.

2. Peeseevation by Exolttsion of Aie.

576. Oxygen as an exciter of decay, — Other conditions being favor-
able, that is, moisture being present and a proper temperature, access
of air starts decomposition, — it is the prime mover of the destructive
processes. We have already noticed its mode of action, in speaking of
fermentation (488). In the case of vegetables, as potatoes and apples,
for example, if the air is excluded from their interior, they remain
for a considerable time sound. But if we cut them, the oxygen
quickly attacks the exposed surface and turns it brown, indicating the
incipient stage of decay. When the surface of fruits and vegetables
is injured, so that their juices come in direct contact with the air, the
effect is at once seen. If an apple is bruised, the injured spot imme-
diately turns dark, and decomposition gradually spreads from that
point, until the whole apple becomes rotten. The juice of the ripe
grape, while protected from air by an unbroken skin, remains sweet
and scarcely changes ; it may be dried and converted into a raisin,
its sweetness remaining. If it be crushed under mercury, and the
juice be collected in a glass completely filled with mercury, so as to
prevent all contact of air, it will remain unchanged for several days.
But if air be once admitted, as by perforating the grape-skin with a
needlo's point, fermentation commences almost instantaneously, and the
juice is soon entirely changed. The same is true of all animal fluids.
Milk, while in the udder of the healthy cow undergoes no change,
but in contact with air, its properties are soon totally altered — it is
soured and coagulated (547). When life has been destroyed by bodily
wounds, decomposition spreads from them ; or if the animal have not
died by violence, the changes may begin ioternally in those parts,
such as the lungs, which are in contact with the air.

577. Changes begun by Oxygen may proceed without it. — ^It is by no
means necessary, in all cases, that air should be in constant contact
with the changing substance; the decomposition once commenced,

BY EXCLUSION OP AIE. 303

may contintie, thougli the oxygen be entirely excluded. Milk, if once
exposed to the air, coagulates and sours, though sealed up in air-tight
vessels. Grape juice, though oxygen be completely cut off, ferments,
generates gases, and often explodes the bottles in which it is confined.
The impulse of disorganization being given, decomposition goes on
without further external aid. To explain this, we must suppose that
the atoms of the changing substance were at first in a kind of rest or
equilibrium, without mutual activity, and that by the invasion of oxy-
gen, this equilibrium has been disturbed, so that the elements of the
substance begin to act and re-act upon each other, giving rise to new
products. In this way, a state of change commenced by merely jost-
ling a few surface atoms through contact of oxygen, is propagated by
intestinal action throughout the entire mass.

578. How changes begun by Oxygen may be stopped. — "The property
of organic substances to pass into a state of fermentation and decay
in contact with atmospheric air, and in consequence to transmit these
states of change to other organized substances, is annihilated, in all
cases without exception^ l)y heating to the hoiling points — ^Liebio.
The substance most prone to be affected by air-contact, is hquid albu-
men ; and this by boiling is solidified, and so altered in properties, as
to lose its peculiar susceptibihty of transmutation. The boiling cer-
tainly obhterates the effect that oxygen has produced, and as the
atoms of matter have no inherent power to put themselves in motion,
and cannot change place unless influenced by some external cause, it
is obvious that the nutritive substance will remain unaltered if the
air is Jcept excluded. These facts indicate the most certain, manage-
able, and perfect method of preserving alimentary substances. By
simply boating to the boiling point, which produces no other change
than that of partial cooking, and afterward protecting from the air,
alimentary substances, both animal and vegetable, may be preserved
in their natural condition entirely unchanged in both flavor and pro-
perties, for an indefinite period. This plan was first brought into
general notice by M. Appeet of France, in 1809. He preserved all
kinds of fruits, vegetables, meats, soups, &c., in glass bottles. His prac-
tical methods, however, were crude and unsatisfactory, and have been
superseded by others. Captain Ross presented the society of arts with
a box from the house of Gamble and Daekin (London), which con-
tained cooked provisions sixteen years old, and that were in a state of
perfect preservation. The details of the preparation on a large scale,
as practised chiefly for marine consumption, we have no space here
to describe. The vegetables, meats, poultry, &c., are cooked precisely

304 PEESEEVATION OF AXTMEISTTAET SUBSTANCES.

in the same maBner as for immediate consumption, and then sealed
up in boxes and canisters which do rot contain a particle of air.

579. Domestic preservation in air-tiglit Tessels. — ^The preservation of
delicate fruit and vegetables in air-tight cans, has now become quite
generally a household operation, and there can be no doubt that as
people acquire experience in the process, they will employ it much
more extensively. Of this process Prof. Liebig remarks, "The pre-
pared aliments are enclosed in canisters of tinned iron plate (609),
the covers are soldered air-tight, and the canisters exposed to the
temperature of boiling water. When this degree of heat has pene-
trated to the centre of the contents, which it requires about three or
four hours to acomplish, the aliments have acquired a stability which
one may almost say is eternal. When the canister is opened, after
the lapse of several years, the contents appear just as if they were only
recently enclosed. The color, taste, and smell of the meat, are com-
pletely unaltered. This valuable method of preparing food, has been
adopted by many persons in my neighborhood, and has enabled our
housewives to adorn their tables with green vegetables in the midst
of winter, and with dishes at all times which otherwise could be ob-
tained only at particular seasons."

580. Canisters closed by soldering. — Perfectly tight tin canisters of
almost any convenient shape are provided, and the article to be pre-
served, sometimes raw, but generally cooked, is placed within it, and
the lid soldered down. The lid, is however, perforated with a small
aperture or pin-hole. The canister is then placed in boiling water, and
the moisture within is converted into steam which drives out the air.
The boiling is continued as long as may be required totally or partially
to cook the contents of the can, which is then withdrawn, and the
pin-hole closed with solder. This is an operation of considerable
nicety. The heat drives out not only air contained in the canister,
but also a jet of steam. The solderer, therefore, lets fall a few drops
of cold water on the tin around the aperture, producing a momentary
condensation of the steam, during which the pin-hole is dexterously
closed. The delicacy and success of the operation, consists in carry-
ing the condensation only so far as just to arrest the jet of steam, and
in closing the opening at the instant. After the canister is closed,
it is again exposed with its contents for a short period to a boiling
heat.

581. Spratt's self-sealing Cans. — In many cases a tinsmith may not
be near, and the soldering operation for closing the canisters will be
quite certain to fail in the hands of the inexperienced. To obviate

BY EXCLUSION OF AIR.

305

Fig. 106.

this difficulty, other arrangements have been contrived. Speatt's
cans* are oblong tin cylinders (Fig. 106), holding from a quart to a
gallon, which are closed with a screw acting upon a ring or ' com-
press ' of india-rubber, and then hermetically sealed with beeswax.
The closure is simple and effectual, and can be managed with a little
care by any body. The articles being introduced into the can, the cap
is screwed down tightly with the fingers^ and the can submerged in a
boiler of cold water, which is then raised
to boiling. After boiling a sufficient time
they are withdrawn, the caps unscrewed^
and the cans left open for one minute. If \
the previous boiling has been thorough,
steam wiU escape freely. If it does not
so escape, the boiling must be repeated.
The cap is then screwed down, this time
very tightly, with a wrench provided^ and
the can introduced into the water and
boiled a second time. On withdrawing it
again melted beeswax is poured into a
little channel or groove, which makes the
sealing perfect, if the cap fits and is tightly
screwed down. In all cases there are at
least two boilings. The second might be
thought unnecessary, but it is not. The vessel must be opened, that
the steam may drive out the air, and there is always the possibility
that a trace may be left. If so, during the second boiling the oxygen
will be entirely converted into carbonic acid, which is innoxious. As
the results of large experience the times required for the boiling are
as follows :

First boiling. Second boiling.

Berries of all kinds 15 minutes. 5 minutes.

Cherries or currants 15 « 5 «

Khubarb 15 « 6 «

Peaches 20 " 5 "

Plums 20 " 10 "

Quinces, pears or apples 45 " 15 «

Tomatoes 80 " 15 "

Asparagus 60 " 80 "

Green peas, corn or beans 8 hours. 3 hours.

582. Suggestions concerning the use of the Cans.— None but perfectly
fresh sound fruit shoiild be put up in the above manner. It is recom-

Spratt's Self-sealing Can.

* Manufactured by Wells & Pbovost, New York,

306 PEESEEVATION OF AUMENTAEY SUBSTAJSTCES.

mended that peaches, quinces, pears and apples be peeled, and the
seeds removed before preserving, as seeds and peel embitter and other-
wise injure the flavor. Peach stones contain traces of Prussic acid, a
powerful poison, which, if the fruit be preserved whole, is liable to be
diffused through it. Fruits are preserved either with or without
sugar ; if without, a quarter of a pint of water should be poured over
every quart of fruit while in the can. If the fruit is to be sweetened,
make a sirup, and pour on it in the can, until it is nearly full. A
sirup for summer fruits is made by adding a pound of crushed sugar
to a pint of water, and boiling two minutes. Very acid fruits, such
as quinces and plums, require a stronger sirup, say li lb. sugar to a
pint of water. If the cans are not perfectly tight when the steam
condenses vnthin, forming a vacuum, the external pressure of the air
may drive the soft beeswax in through the crevice. Aliments well
put up wiU keep in a room at any temperature ; if the cans bulge, it
is a sign of development of gas by internal decomposition, and their
contents wiU not keep.

3. Peeseevation at low Tempeeatuees.

583. Influence of Temperature. — Degrees of temperature exert an
absolute control over the duration of alimentary compounds. At 32°
their juices are congealed, and they remain totally unchanged. At a
few degrees above the freezing point changes are very slow. As we
ascend the scale, the conditions of mutation become more favorable,
except in the case of albumen, which is rendered more enduring by
the heat of coagulation. In all other cases decomposition proceeds
more rapidly as warmth increases, until the point of quick disorgani-
zation, charring, and active combustion is reached.

584. Freezing as a means of Preserving. — Congelation, therefore, may
be resorted to as a means of preservation, chemical action being im-
possible where the substance is reduced to a solid state. Eemarkable
cases are on record in which the bodies of animals have been disen-
tombed from masses of ice, in such a state of preservation that the
flesh was flt to support nutrition, although they had been wrapped in
ice for such a vast period that the race to which they belonged had
become extinct. It is customary in many regions to preserve fresh
meat by freezing it, and packing in snow. Some object that the
flavor of meat is injured by freezing ; but the Enssians, on the con-
trary, insist that it is improved. Great care is necessary in thawing
all frozen aliments, whether meat, fish, or vegetables. It should be
done slowly, and the best way is by immersion in very cold water.

AT LOW TEMPEEATUEES.

307

A shell of ice will be formed around them, as we have often seen in
' taking the frost out of apples ; ' — the water in contact with the sur-
face being frozen into a scale, by parting with its heat to thaw the
frozen apple within. If thawed too rapidly, as by placing them in a
warm room or in hot water, the taste is impaired, and the composition
of the substance so affected that putrefaction is rapidly brought on.
One of the effects of freezing and thawing potatoes and some fruits,
is to increase the amount of sugar, as shown by their sweeter taste.

585. Low Temperatures above Freezing — Refrigerators. — We command
^ow temperatures by cellars, and the use of ice. Excavations made
below the surface of the ground have a temperature common to the
surrounding strata of earth, which is cooler the deeper we go for
nearly a hundred feet. The temperature is also very constant, the
extremes of winter and summer being both excluded. The temper-
ature of good cellars (40° to 60°), is below the range most favorable
to putrefaction (60° to 100°). By the use of ice in the ice-house
or refrigerator, the temperature

may be kept down to within 5° ^^®- ^^^

or 10° of freezing. At these
points changes proceed slowly, so
that meat admits of being kept at
this degree of coolness for a con-
siderable time. It is said that
meat should never be suffered to
touch ice, as it is toughened and
otherwise injured. The refriger-
ator is commonly a rude, shelved
box. If opening at top, it is
troublesome of access and difficult
to make its space available. If it
have doors at the sides, the cold
air flows out every time it is
opened ; and if the ice is placed
at the bottom, there is no circu-
lation of air or means of cooling
the upper space. A. S. Lyman, of K Y., has obviated these defects by
a newly devised arrangement (Fig. 107). The ice is placed in an upper
chamber over a grate opening to the flue a, through which, ice-cold
air constantly falls. The body of the refrigerator is occupied by three
drawers, I e d, c being represented as partially withdrawn. The cold
air fills these di-awers, and as it becomes slightly warmer is pressed

Lyman's Bureau EeMgorator.

308 PEESEKVATION OF ALIMENTAET SUBSTANCES.

upward in the direction of the arrows, and re-cooled by contact with
the ice. It descends again through the flue, the temperature of the
whole refrigerator being thus kept down nearly to freezing. The
waste water is caught at g. The arrangement of drawers makes the
whole space available, and is as convenient as a common bureau.
When one is partially withdrawn, as at e, the air in, it being heavier
than that of the room, does not escape, while the circulation of air con-
tinues within. There is also a twofold means of purifying the air.
At f there is a filter consisting of a wire-gauze box, through which
the air passes and is disinfected. "When it comes in contact with the
ice, it is condensed and its moisture deposited, so that it has a real dry-
ing effect upon the articles to be preserved. The water constantly form-
ing by the melting ice is highly absorbent of the gases set free by de-
composing food, so that these impurities are constantly washed out of
the air in its progress. The charcoal filter, in effect, divides the space
into two refrigerators ; _ thus preventing articles in one from smelling or
tasting of those in the other. Cars are constructed upon this prin-
ciple, in which meat is transported from the Western States to New
York in summer.

586. Keeping Frnits at low Temperatares. — The most important fact
relating to the composition of fruits is the large proportion of water
they all contain, and which constitutes the bulk of their peculiar
juices. From three-fourths to nine-tenths of them being liquid, we
are to regard them as consisting of a small amount of solid matter
diffused through from four to ten times their bulk of water. This con-
dition is eminently favorable to the action of fruits upon the organs
of taste in their njLtural or uncooked state ; being in a kind of pulpy,
half-dissolved condition, they are ready to take prompt effect upon
the pappilsa of the mouth. But the same property of fruits which
adapts them so perfectly to our gustatory enjoyment, shortens the
time when they can be so employed. Their abounding moisture
"favors decomposition, and they are hence perishable and short-lived.
Yet by proper management fruits may be long preserved in a fresh
and perfect state. Vegetables and juicy fruits, as apples and pears,
can be preserved for months in ceEars where the necessary warmth
for inducing decay is not attained. Sometimes fruit, as many varieties
of apples, are not really ripened at the time of gathering, but undergo
a slow change during the winter months, their acid principle being
converted into sugar. To be best preserved fruit should be picked when
perfectly dry, at a time when the stalk separates easily from the spur.
Apples and pears should have their stalks or " stems " separated from

J

BY DRYING. 309

the tree^ and not from themselves. The utmost care should he ob-
served to prevent bruises or contusions ; some have implements for
collecting the most valuable kinds of fruit, so as not to touch it with
the hand. The most delicate kinds do not bear handling or wiping,
as this rubs off the bloom which, when allowed to dry on some fruits,
constitutes a natural varnish, closing up the pores and preventing the
evaporation of the juices. Apples have been presei-ved a year in a
fine fresh condition, by keeping them in an atmosphere within ten
degrees of the freezing point. Constancy of temperature is important,
as alternations of heat and cold, by contracting and expanding the
juices, seem to favor chemical changes. Grapes, cherries, currants,
gooseberries, and other soft fruits have been preserved for use in win-
ter by gathering them when not too ripe, and when very dry putting
them unbruised into dry bottles, which are afterwards well corked,
and then buried in the earth. The efficiency of this method of pre-
serving is increased by immersing the bottles containing the fruit for
a few minutes previously to corking, in hot water, which coagulates
the vegetable albumen. The preservation is here due to the joint in-
fluence of exclusion of air, and a low and uniform temperature. A
preservatory for fruit, or kind of refrigerator on a large scale, has been
devised by Mr. Paekee. The fruit, picked carefuUy and unbruised, is
conveyed at once to the preservatory, where the temperature is
down nearly to freezing. The plan requires that ice be supplied the
previous winter.

4. PEESEEVATIOlSr BT DeYING-.

587. Retention of Water in Fruits and Vegetables. — ^As nature places
water in large quantities in organic bodies, in many cases she
takes due precautions to keep it there. Unripe potatoes and unripe
apples removed from the parent stock shrivel, shrink, and perish.
These eifects result from the porous condition of the immature skin,
which permits the water within to escape by evaporation. " But
when ripe this porous covering has become chemically changed into a
thin impervious coating of corh^ through which water can scarcely
pass, and by which, therefore, it is confined within for months to-
gether. It is this cork layer which enables the potato to keep the
winter through, and the winter pear and winter apple to be brought
to table in spring of their full dimensions." — (Johnston).

588. Loss of Water as a means of Preservation. — Yet as organic sub-
stances may be kept by solidifying the water, that is, freezing them,
they may also be preserved by withdrawing it. Both vegetable and
animal substances are extensively preserved in this way. Drying is a

SI0 PKESEKVATION OF AUMENTAEY SUBSTANCES.

kind of disorganization of the alimentary body, its largest constitnent
being removed ; yet, in this case, the lost ingredient may be added
again, and the substance brought into a condition more or less re-
sembling the natural state. Drying is effected either by simple
exposure to the sun and air, or by artificial heat of a higher intensity,
applied in various ways. Both methods are quite practicable, but
have their disadvantages. Drying in the air is necessarily a slow pro-
cess, so that there is danger of moulding and fermentation ; the sub-
stances require to be made small or thin, and as the air itself is moist,
the drying can never be complete, but only reaches a certain point,
and then fluctuates with the varying atmospheric dampness. On the
other hand, when artificial heat is employed, as in kiln-drying in close
apartments, it is obvious that the foods are liable to be much altered
in their nature. The starch may be dissolved, or altered to gum ; the
sugar browned and changed to caramel, acquiring a bitter, disagree-
able taste, if the heat of the drying chamber be too high ; while if the
temperature be not higher than 140°, the albumen may be dried so as
to dissolve again in water ; if higher, it is coagulated, and remains
insoluble.

589. Preserviiig Succulent Vegetables. — These, if exposed to the air,
evaporate their moisture, wUt, and lose their crispness and freshness.
A damp cool place is best to prevent these changes for a time. Many
are kept soundly during winter by burying in the earth. M. Masson,
head gardener to the Horticultural Society of Paris, has described a
mode of preserving succulent vegetables by drying and compression.
He prepares cabbage, cauliflower, potatoes, spinach, endive, celery,
parsley, &c., in such a manner that they keep for any length of time,
and when soaked in water resume much of their original freshness
and taste. They are chiefly prepared for marine consumption. The
packages of dried vegetables are covered with tinfoil. Dr. Hassall
speaks of a specimen of dried cabbage as follows : " On opening the
package the contents, which formed a solid cake, were seen to consist
of fragments of leaves of a yellowish color, interspersed here and
there with some that were green. In this state it was difficult to de-
termine what the nature of the vegetable was. Soaked in hot water
for about half an hour, it gradually underwent a great expansion, so
that it acquired several times its former bulk. "When examined, it
was evident at a moment's glance that the vegetable consisted of the
sliced leaves of the white-hearted garden cabbage, presenting the ap-
pearance and color, and possessing the taste and smell, to a remarkable
extent, of the vegetable in its recent state."

BY AlSTTISiTPTIC AGENTS. 311

5. Peeseevation by Antiseptics.

590. Remarkable properties of common Salt. — Antiseptics are op-
posers of putrefaction. Certain bodies when added to organized
substances, possess the power of resisting or preventing their putre-
factive decomposition ; they are numerous, and act in various ways.
Those used for preserving aliments are salt-petre, sugar, alcohol,
creosote, vinegar, oil, and common salt. However ' common ' this
last substance may be, we shall nevertheless be interested in giving it a
moment's attention. Though mild and pleasant to the taste, it is
composed of two elements, one a yellowish green, suffocating, poison-
ous gas, cMori?ie, and the other a bright silvery-looking metal, sodium
(hence the chemical name of the substance chloride of sodium).
"When these two elements are brought together, they unite spontane-
ously ; and yet so prodigous is the force with which they combine, so
enormous the condensation of matter, that although the sodium unites
vrith more than five hundred times its bulk of the heavy gas, yet the
compound formed occupies less space fio. los.

than the solid sodium alone did before
the union. No known mechanical forc6
could have accomplished this, yet it re-
sults from the agency of chemical af-
finity (Faeeaday). If a lump of com-
mon salt, (it occurs in large masses in
the shape of rod salt,) be cut into the
form of a thin plate, and held before a
fire, it does not stop the heat-rays, but
has the singular property of permitting - — ^
them to dart through it, as light does
through glass — it is the glass of heat. A
hundred lbs. of water, hot or cold, dis-
solve 37 of salt, forming a saturated so-
lution or the strongest brine. When the
briny solution evaporates, the salt reap-

■r^^^^r, 4^ +i^« r,^T;A -f^,.™ „_ i IT How crystals of common salt are

pears m the solid lorm, or crystauizes. formed.

Its crystals are cube shaped ; if the evaporation takes place slowly
they are large, but if it be rapid, they are small, and formed in a
curious manner. Eesultmg from evaporation, they are naturally
formed at the surface of the liquid, and present the appearance of little
floating cubes, as shown in (Fig. 108), where the solid crystal is up-
borne or floats in a little depression of the fluid surface. New crystals

312 PBESEEVATION OP AUMENTAEY SUBSTANCES.

soon form, which are joined to the first at its four upper edges, con-
stituting a frame above the first little cube (Fig.. 109). As the whole
descends into the fluid, new crystals are grouped around the first
frame constituting a second {Fig. 110). Another set added in the
same way gives the appearance shown in Fig 111. The consequence
of this arrangement is that the crystals are grouped into hollow, four-
sided pyramids, the walls of which have the appearance of steps, be-
cause the rows of small crystals retreat from each other. This mode
of grouping is called Jiopper-sTiaped (Fig. 112).

591. Sources and Purification of Salt. — Salt is obtained from three
sources ; first^ it is dug from the earth in mines, in large masses, like
transparent stones (roc^ salt) ; second, it is procured by evaporating
sea-water (bay salt) ; and, third, by boiling down the liquid of brine
springs. It differs very much, in purity, from diflferent sources, being
in many cases contaminated by salts of calcium and magnesium, which
render it bitter. Pure salt, in damp weather, attracts water from the
atmosphere, and becomes moist, but parts with it again when the
weather becomes dry. But the chlorides of calcium and magnesium
are much more absorbent of water, and hence, if the salt is damp and
moist when the air is dry, we may infer that a large proportion
of these substances is present in it. Salt, for certain culinary pur-
poses, as for salting butter, should be perfectly pure. Its bitter in-
gredients are more readily soluble in water than is the salt itself;
hence, by pouring two or three quarts of boiling water upon ten or
twenty lbs. of salt, stirring the whole well now and then for a couple
of hours, and afterwards straining it through a clean cloth, the ob-
noxious substances may be carried away in solution. Among the
purest, is that called Liverpool salt, which is an English rock-salt dug
from the mines ; dissolved, recrystallized and ground.

592. How salt preserves meat. — Salt is more widely used than any
other agent in conserving provisions, especially meats. It is well
known that when fresh meat is sprinkled with dry salt, it is found
after a few days swimming in brine, although not a drop of water
has been added. If meat be placed in brine it grows lighter, while
the quantity of liquid is increased. The explanation of this is,
that water has a stronger attraction for salt than it has for flesh.
Fresh meat contains three-fourths of its weight of water, which is
held in it as it is in a sponge. Dry salt will extract a large part of
this water, dissolving in it and forming a saline liquid or brine. In
this case, the water of the meat is divided into two parts ; one is taken
up by the salt to form brine, while the other is kept back by the

BY AlSmSEPnC AGENTS. 3l^

meat. The salt robs the meat of one-third or one-half the water of its
juice. Salting is therefore only an indirect mode of drying ; the chief
cause, perhaps, of the preservation of the meat, being, that there is
not sufficient water left in it to allow putrefaction. The surrounding
brine does not answer this purpose, as it does not act upon the meat ; its
relation to flesh being totally dififerent to that of fresh water. If fresh
water be applied to a piece of dry meat, it is seen to have a strong
attraction for it, but if we use even a weak solution of salt, it flows
over it wetting it but very imperfectly.

593. How meat is injured by salting. — The separation of water from
the fibre of meat shrinks, hardens, and consequently renders it less di-
gestible. It is quite probable, also, that the salt, in some way not yet
understood, combines with the fibre itself, ^hus altering injuriously
its nutritive properties. Peeeiea thinks that the separation of water
is not sufficient alone to account for its preservative action, but that
it must produce some further unexplained effect upon the muscular
tissue. The main and well-established injury of salting, however, is
caused by the loss from the meat of valuable constituents, which escape
along with the water which the salt withdraws. It has been shown
that the most influential constituents of meat are dissolved in its juice
(471). The salt, therefore, reaUy abstracts the juice of flesh with its
albumen, kreatine, and valuable salts ; in fact, the brine is found to
contain the chief soup-forming elements of meat. Salting, therefore,
exhausts meat far more than simple boiling, and as the brine is not
consumed, but thrown away, the loss is still greater In salting meat,
however, there happens to be a slight advantage resulting fi*om its
impurities, lime and magnesia. These are decomposed by the phos-
phoric acid of the juice of flesh, and precipitated upon the surface,
forming a white crust, which may often be observed upon salt meat ;
this constituent, therefore, is not separated in the brine. Saltpetre
has a preservative effect, probably in the same way as common salt,
but it is not so powerful, and unlike salt produces a reddening of the
animal fibres. A little of it is often used along with salt for this
purpose.

594. Salting Vegetables.— These may be preserved by salt, as well as
flesh, but it is not so commonly done. In salting vegetables, however,
a fermentation ensues, which gives rise to lactic acid. This is the
case in the preparation of sauerTcraut from cabbages, and in salting cu-
cumbers. The brine with which both vegetables are surrounded is
found strongly impregnated with both lactic and butyric acids.

595. Preservation by Sugar. — This is chiefly employed to preserve
14

314 PEESEEVATIOlSr OF ALIMENTAET SUBSTANCES.

fruits. Many employ both sugar and molasses for the preservation of
meat ; sometimes alone, but more commonly united with salt. The
principle of preserving by means of sugar is probably similar to that
of salting. In the case of fruits, the sugar penetrates withiu, changing
the juices to a sirup, and diminishing their tendency to fermentation
or decomposition. "Weak or dilute solutions of sugar are, hovpever,
very prone to change ; they require to be of a thick or sirupy consist-
ence. Knapp states that the drops of water which condense from
the state of vapor on the sides of the vessels in which the preserves
are placed, are often sufficient to induce incipient decomposition, by
diluting the upper layers of sugar. The effect of the acids of fruits is
gradually to convert the cane sugar into uncrystaUizable and more fer-
mentable grape sugar,

596. PreserTing by Alcohol and other substances. — Strong alcoholic li-
quors are used to prevent decomposition in both vegetable and animal
bodies. They penetrate the substance, combine with its juices, and
as the organic tissues have less attraction for the spirituous mixture,
it escapes ; and the tissues themselves shrink and harden in the same
way as when salted. Alcohol also obstmots change by seizing upon
atmospheric oxygen, in virtue of its superior attraction for that gas,
and thus preventing it from acting upon the substance to be preserved.
Vinegar is much used for preserving, but how it acts has not been ex-
plained. Spices exert the same influence. Creosote, a pungent com-
pound existing in common smoke, and which starts the tears when
the smoke enters the eyes, is a powerful antiseptic, or preventor of
putrefaction. Meat dipped for a short time in a solution of it wOl not
putrefy, even in the heat of summer. Or if exposed in a close box to
the vapor of creosote, the effect is the same, though in both cases the
amount producing the result is extremely small. The preservative
effect of smoke-drying is partly due to creosote, which gives to the
meat its peculiar smoky taste, and partly to desiccation. Oil is but
little employed in saving alimentary substances — two kinds of fish,
anchovies and sardines, are preserved in it. Charcoal has always been
ranked as an antiseptic or arrester of putrefaction ; but it has been
lately shown that it is rather promotive of decomposition. How this
is, will be explained in another place (811).

6. Peeseevation of Milk, Buttee, and Cheese.

597. Modes of preserving Blilk. — The cause of the souring of milk
we have seen to be the action of oxygen upon its casein, which alters
the sugar to acid (547). If, therefore, tlie milk be tightly bottled, and

MILK, BUTTEE, AI^D CHEESE. 31 5

then boiled, the fermentative power of the curdy matter is destroyed,
and it may be kept sweet for several months. When, however, the
milk is again exposed to the air, the cm-d resumes its power of acting
upon sugar, and acid is again formed. "When milk is kept at a
low temperature, the cold retards its changes. If the vessels contain-
ing it are placed in a running stream of cool water, or in a place cooled
by ice, it will remain cool for several days. Milk may also be pre-
vented from souring, even in warm weather, by adding to it a little
soda or magnesia. The alkali destroyes the acid as fast as it is pro-
duced, and the liquid remains sweet. The small quantity of lactate
of soda or magnesia which is formed, is but slightly objectionable. If
milk be evaporated to dryness, at a gentle heat, with constant stirring,
it forms a pasty mass, which may be long kept, and which reproduces
milk when agaia dissolved in water. Alderi's concentrated milh is a
solidified pasty preparation, made by evaporating milk, with sugar,
and affords an excellent substitute for fresh milk, in. many cases, when
dissolved in water.

598. Unpnrifled Butter qnickly spoils. — Butter when taken from the
churn contains more or less of all the ingredients of milk, water, casein,
sugar, lactic acid, which exist in the form of buttermilk, diffused
through the oily mass. Oheveetjl states that fresh butter yields 16
per cent, of these ingredients, chiefly water, and 74 of pure fat. In
this state butter cannot be kept at all. Active decomposition takes
place almost at once, the butter acquires a bad odor, and a strong dis-
agreeable taste. Tlie casein passes into incipent putrescence, generat-
ing offensive compounds, from both the sugar and oily matter.

599. Bntter Pnrifled by Mechanical Worldng. — It is obvious, theyefore,
that in order to preserve butter, it must first be freed from its butter-
milk, which is done by working it, over and over, and pressing or
squeezing it, which causes the liquid slowly to ooze out and flow away.
The working or kneading is done with a wooden ladle, or a simple
machine adapted to the purpose, or else by the naked hand. It is ob-
jected that the employment of the hand is apt to taint the butter by
its perspiration ; but while it is admitted that moist hands should never
do the work, many urge that those which are naturally cool and dry,
and made clean by washing in warm water and oatmeal {not soaj))^
and then rinsed in cold water, will remove the sour milk from the
butter more effectually than any instrument whatever, without in the
least degree injuring it. Overworking softens butter, renders it oily,
and obliterates the grain.

600. Preparation of Batter by Washing. — Some join washing with

Slfife. PRESERVATION OF ALIMENTAEY SUBSTANCES.

mechanical working, to separate the buttermilk. It is objected to this,
first, that water removes or impairs the fine aroma of the butter, and,
second, that it exposes the particles of butter to the injurious action
of air much more than mechanical working. On the other hand, it is
alleged that without water we cannot completely remove the ferment-
ing matter, the smallest portion of which, if left in the butter, ulti-
mately injures it. K water be used, it is of the utmost consequence to
guard against its impurities. It is liable to contain organic substances,
vegetable or animal matter, in solution, invisible, yet commonly pres-
ent, even in spring water. These the butter is sure to extract, and
their only effect can be to injure it. The calcareous waters of lime-
stone districts are declared to be unfit for washing butter. Speengel
states that the butter absorbs the lime, and is unpleasantly affected by
it. A. B. DioKiNsoii is of opinion that the best butter cannot be
made where hard water is used to wash it ; he employs only the soft-
est and purest for this purpose.

601. Cause of Rancidity in Bntter. — Pure oil has little spontaneous
tendency to change. If lard, for example, be obtained in a condition
of purity, it may be kept sweet for a long time without salt, when
protected from the air. That it does alter and spoU in many cases, is
owing to traces of nitrogenous matter, animal membranes, fibres, &c.,
which have not been entirely separated from it. These pass into de-
composition, and carry along the surrounding oily substance. So with
butter ; when pure, and cut off from the air, it may be long kept with-
out adding any preservative substance. But a trifling amount of curd
left in it is sufficient to infect the whole mass. It is decomposed, and
acting in the way of ferment upon the sugar and oUy substance itself,
develops a series of acids, the tutyric, which is highly disagreeable
and offensive, and the capric and caproic acids, which have a stron g
sour odor of perspiration. The butter is then said to be rancid.
In general, the more casein is left in butter, the greater is its tendency
to rancidity.

602. Action of Air npon Butter. — The fat of butter is chiefly composed
of margarin, which is its main solidifying constituent, and abounds
also in human fat. It is associated with a more oily part, olein.
Now, air acts not only upon the curdy principle, causing its putres-
cence; but its oxygen is also rapidly absorbed by the oleic acid. One
of the effects of this absorption may be to harden it, or convert it into
mai'garic acid. This is, however, a first step of decomposition, which,
when once begun, may rapidly extend to the production of various
offensive substances. When, therefore, butter is much exposed to the

MILK, BUTTER, AND CHEESE. 317

air it is certain to acquire a surface rancidity, which, without pene-
trating into the interior, is yet sufficient to injure its flavor. It is in-
dispensable to its eflfectual preservation that the air be entirely ex-
cluded from it. Hence, in packing butter, the cask or firkin should
be perfectly air tight. Care should be taken that no cavities or spaces
are left. If portions of butter are successively added, the surface
should be either removed or raised up in furrows, that the new portion
may be thoroughly mixed with it, or it should be kept covered with
brine, and the vessel ought not to be finally closed until the butter has
ceased shrinking, and the vacancies that have arisen between the but-
ter and vessel's sides are carefully closed.

603. Substances used to preserve Butter. — Salt, added to butter, per-
forms the twofold office of flavoring and preserving it. The salt be-
comes dissolved in the water contained in it, and forms a brine, a
portion of which flows away, while the butter shrinks and becomes
more solid. Salt preserves butter by preventing its casein from chang-
ing ; hence the more of this substance is left in it the more need of
salt. The quantity used is variable, from one to six drachms to the
pound of butter. It is objected to salt that it masks the true flavor
of butter, especially if it be not of the purest quality (591). Salt-
petre will preserve butter ; but it is less active than common salt,
and some think its flavor agreeable. Sugar is sometimes added to aid
in preservation, and to compensate for the loss of the sugar of milk.
Honey has been also used for the same purpose, at the rate of an
ounce to the pound of butter. Some employ salt, saltpetre, and sugar
all together. From an examination of upwards of forty samples of
English butter, Hassall found the proportion of water in them to
vary from 10 to 20, and even 30 per cent., and the proportion of salt
from one to six or seven per cent. A simple method of ascertaining
the quantity of water in butter is, to melt it and put it in a small bottle
near the fire for an hour. The water and salt wUl separate and sink
to the bottom.

604. Changes of Cheese by Time. — Cheese requires time to develop
its peculiar flavor, or ripen. A slow fermentation takes place within,
which differs much according to the variety of circumstances con-
nected with its preparation, and the degree and steadiness of the tempe-
rature at which it is kept. The fermentation, which is gentle and pro-
longed at a low temperature, becomes too rapid in a warm, moist place.
The influence of temperature is shown by the fact that in certain locaU-
ties of France, especially at Eoquefort, there are subterranean caverns
which rent and are sold at enormous sums for the purpose of keeping

318 MATERIALS OF CULINARY AND TABLE UTENSIIS.

and maturing cheese. These natural rock-cellars are maintained, by
gentle circulation of air, at 41° to 42°. The nature of the changes
that cheese undergoes has not been clearly traced. It is known that
the casein becomes so altered as to dissolve in water. The salt intro-
duced to preserve it is said to be decomposed ; the oily matter gets
rancid, as may be shown by extracting it with ether ; and peculiar
volatile acids and aromatic compounds are produced. Cheese of poor
or inferior flavor, it is said, may be inoculated with the peculiar fer-
mentation of a better cheese, by inserting a plug or cylinder of the
latter into a hole made to the heart of the former. To prevent the
attacks of insects the cheese should be brushed, rubbed with brine or
salt, and smeared over with sweet oil, the shelves on which they rest
being often washed with boiling water.

605. Preservation of Eggs. — When t ewly laid, eggs are almost per-
fectly full. But the shell is porous, and the watery portion of its
contents begins to evaporate through its pores the moment it is ex-
posed to the air, so that the eggs become lighter every day. As the
water escapes outward through the pores of the shell air passes inward
and takes its place, and the amount of air that accumulates within de-
pends, of course, upon the extent of the loss by perspiration. Eggs
which we have preserved for upward of a year, packed in salt, small
ends downwards, lost from 25 to 50 per cent, of their weight, and did
not putrefy. As the moisture evaporated the white became thick
and adhesive, and the upper part was filled with air. To preserve
the interior of the egg in its natural state, it is necessary to seal up
the pores of the shell air-tight. This may be done by dipping them in
melted suet, olive oil, milk of lime, solution of gum arabic, or cover-
ing them with any air-proof varnish. They are then packed in bran,
meal, salt, ashes, or charcoal powder. Eeatjmtje is said to have coated
eggs with spirit varnish, and produced chickens from them after two
years, when the varnish was carefully removed.

VI.— MATEKIALS OF CULINARY AND TABLE UTENSILS.

606. It seems important in this place to ofier some observations
pertaining to our ordinary kitchen and table utensils. We speak of
the chemical properties of their materials rather than of their mechan-
ical structure.

607. Utensils of Iron. — Iron is much employed for vessels in kitchen
operations. The chief objection to it springs from its powerful attrac-
tion for oxygen, which it obtains from the atmosphere. It wiU even

VESSELS OF IBON AND TTN. 319

decompose water to get it. In consequence of this strong tendency to
oxidation, its surface becomes corroded and roughened by a coating of
rust, which is simply oxide of iron. The rust combines with various
substances contained in food, and forms compounds which discolor the
articles cooked in iron vessels, and often impart an irony or stj-ptic
taste. Fortunately, however, most of these compounds, although ob-
jectionable, ai'e not actively poisonous ; yet, sulphate of iron (copperas)
and some other mineral salts of iron, are so. Cast iron is much less
liable to rust than malleable, or wrought iron. There is one mode of
managing cast iron vessels, by which the disagreeable effects of rust
may be much diminished, if not quite prevented. If the inside of
stew-pans, boilers, and kettles be simply washed and rinsed out with
warm water, and wiped with a soft cloth instead of being scoured with
sand or polishing materials, the vessel will not expose a clean metalho
surface, but become evenly coated with a hard, thin jsrust of a dark
brown color, forming a sort of enamel. If this coating be allowed, to
remain, it will gradually consolidate and at last become so hard as to
take a tolerable polish. The thin film of rust thus prevents deeper
rusting and at the same time remains undissolved by culinary liquids.

609. Protection of Iron by Tin. — As such protection, however, in-
volves care and consideration, it is uncertain and unsatisfactory, and
besides it is inapphcable to vessels of thin or sheet iron, A better
method is that of coating over the iron with metallic tin, which has
come into universal use in the form of tin-ware. The sheet tin which
is so widely employed for household utensils is made by dipping pol-
ished sheet iron in vats of melted tin. Tin itself is a metal some-
what harder than lead, but is never used for culinary vessels. What
is called dlocTs tin is generally supposed to consist of the pure metal.
This is an error. It is only tinned iron plate, better planished, stouter,
and heavier than ordinary. All tin ware, therefore, is only iron plate
coated or protected by tin : yet, practically, it is the metallic tin only
that we are concerned with, as that alone comes in contact with our
food.

610. Adaptation of Tin to Culinary Purposes. — Tin, in its metallic
state, seems to have no injurious effect upon the animal system, for it
is often given medicinally in considerable doses, in the form of powder
and filings. It is frequently melted off from the sides of sauce-pans or
other vessels in globules, and is thus liable to be swallowed, a circum-
stance which need occasion no alarm. The attraction of tin for oxy-
gen is feeble, and it therefore oxidizes or rusts very slowly. Strong
acids, as vinegar or lemon juice, boiled in tin-coated vessels, may dis-

320 MATERIAXS OF CULINARY AND TABLE UTENSILS.

solve a minute portion of the metal, forming salts of oxide of tin,
but the quantity will be so extremely small that it need excite little
apprehension. It is a question among toxicologists whether its oxide
be poisonous. Pkotjst showed that a tin platter, which had been in
use two years, lost only four grains of its original weight, and probably
the greater part of this loss was caused by abrasion with whiting, sand,
or other sharp substances during cleansing. If half of it had been
taken into the system dissolved, it would have amounted only to -^-^ of
a grain per day, a quantity too trifling to do much harm, even if it were
a strong poison. Common tin, however, is contaminated with traces
of arsenic, copper, and lead, which are more liable to be acted upon
by organic acids and vegetables containing sulphur, as onions, greens,
&c. Peeeiea remarks that acid, fatty, saline, and even albuminous
substances may occasion colic and vomiting by having remained for
some time in tin vessels. Still, tin is unquestionably the safest and
most wholesome metal that it is found practicable to employ 11 domes-
tic economy.

611. Zinc Vessels Objectionable. — Zinc is rarely employed as a mate-
rial for culinary vessels. In many cases it would be unsafe, as a poi-
sonous oxide slowly forms upon its surface. It has been recommended
for milk pans on the ground that milk would remain longer sweet in
them, and hence, more cream arise. But whatever power of keeping
milk sweet zinc possesses, it can only be caused by neutralizing the
acid of milk with oxide of zinc, thus forming in the liquid a poisonous
lactate of zinc.

612. Behavior of Copper ia contact with Food. — This metal suffers
very little change in dry air, but in a moist atmosphere oxygen unites
with it, forming oxide of copper ; and carbonic acid of the air, combin-
ing with that substance, forms carbonate of copper, of a green color.
Copper is easily acted on by the acid of vinegar, forming verdigris,
or the acetate of copper, which is an energetic poison. Other vegeta-
ble acids form poisonous salts with it in the same way. Common salt
is decomposed by contact with metallic copper during oxidation, the
poisonous chloride of copper being formed. AU kinds of fatty and
oUy matter have the property of acting upon copper and generating
poisonous combinations. Sugar also forms a compound with oxide of
copper, — the sacharate of copper.

613. Test. — As the salts of copper are of a green color, vessels of
this metal have a tendency to stain their contents green. They are
sometimes employed purposely to deepen the green of pickles, &c.,
and cooks often throw a penny-piece into a pot of boiling greens to

COPPEE AND ENAMELLED VESSELS. 321

intensify their color. A simple test for copper in solution is, to plunge
into the suspected liquid a plate of polished iron, (a knife blade, for
example,) when in a short time, (from five minutes to as many hours,)
it will become coated with metallic copper. The solution ought to be
only very slightly acid. Now, as acid, oU, or salt, is found in almost
every article of diet, it is clear that this metal, unprotected, is quite
unfit for vessels designed to hold food.

614. Protectiou of Copper Utensils. — Yet copper has several advan-
tages as a material for culinary utensils. It is but slowly oxidized, and
hence does not corrode deep, scale, become thin, and finally fall into
holes as iron vessels are liable to do. Besides, copper is a better con-
ductor of heat than iron or tin plate, and consequently heats more
promptly and with less fuel, and as it wears long, and the metal when
old bears a comparatively high price, its employment, in the long run,
is unquestionably economical. Copper vessels ought never to be used,
however, without being thoroughly protected by a coating of tin and
when this begins to wear off they should be at once recoated, which the
copper or tin-smith can do at any time. It has been stated that a small
patch of tin upon the surface of a copper vessel would entirely prevent
the oxidation of the latter by galvanic influence ; but Mr. Mitchel has
shown by experiment that such is not the fact, and that the only
safeguard is in covering completely the entire copper surface. Brass
is an alloy of zinc and copper, and although less liable to oxidize, is
nevertheless unsafe. Kettles of brass are often employed in preparing
sauces, sweetmeats, &c., but this ought never to be done unless they
are scrupulously clean and polished, and hot mixtures should not be
allowed to cool or remain in them.

615. Enamelled Ironware Vessels. — It would seem that no one mate-
rial possesses all the qualities desirable to form cooking vessels.
Some of the metals are strong and resist heat ; but, as we have seen,
various kinds of food corrode them. Earthenware, on the contrary,
if well made, resists chemical action, but is fractured by slight blows
and the careless application of heat. An attempt has been made to
combine the advantages of both by enamelling the interior of ii'on ves-
sels with a kind of vitreous or earthenware glaze. Various cooking
vessels, as saucepans, boilers, and the like, have been prepared in this
manner, and answer an admirable purpose. Dr. Fee remarks, I con-
sider such a manufacture to be one of the greatest improvements
recently introduced into domestic economy, such vessels being remark-
ably clean, salubrious, and adapted to the delicate culinary opera-
tions of boiling, stewing, making of jellies, preserves, &c.

14*

822 MATERIALS OF CDUNAUT AND TABLE UTENSILS.

616. Earthenware Vessels — Glazing. — Vessels of earthenware are in
universal household use. They are made, as is well known, of clay
and sand, of various degrees of purity, witk other ingredients, forming
a plastic mass, which is moulded into all required shapes, and hardened
by baking in a hot furnace. The ware, as it thus comes from the
baking process, is porous, and absorbs water. To give it a smooth,
glossy, water-resisting surface, it is subjected to the operation of glaz-
ing. This is effected in two ways; first, when the stoneware has at-
tained a very high temperature, a few handfuls of damp sea-salt are
thrown into the furnace. The salt volatilizes, the vapor is decomposed,
the hydrochloric acid escaping ; while the soda, diffused over the sur-
face of the ware, combines with its silica, and glosses over the pieces
with a smooth, hard varnish. Another mode by which the desired
artificial surface is given to earthenware, is by taking it from the fire
when it has become sufiiciently firm and stiff, immersing it in a pre-
pared liquid, and restoring it again to the furnace, where by the action
of heat a vitreous or glassy coating is formed.

617. Earthenware Glaze eontaining Lead. — The preparations employed
for glazing common earthenware, are chiefly combinations of lead
with the alkalies, producing vitreous or glassy compounds. It is
known that lead enters largely into many kinds of glass ; it imparts to
them great brilliancy -and beauty, but makes them soft, so that they
are easily scratched, and liable to be attacked by strong chemical sub-
stances. Lead glaze upon earthenware is also subject to the same
objection. It is tender and can be scraped off with a knife, so that
the plates soon become marred and roughened. They also soon black-
en, or darken, when in contact with sulphurized substances. Cooking
eggs or fish in these vessels gives them a brownish tinge. If less lead
be used, the glaze becomes less fusible, the process of applying it more
difiicult, and hence the ware more expensive. Lead glazing can be de-
tected by its remarkably smooth, lustrous surface, resembling varnish ;
while the salt glaze, on the contrary, has less lustre, and the vessel has
not so fine an appearance, all the asperities of the clay beneath being
perfectly visible. Fatty matters, and the acids of fruits, exert a solvent
action on oxide of lead combined in lead glaze, especially where the
chemical energy is increased by a boiling temperature.

618. Other defects of Earthenware Glaze. — If a piece of earthenware
be broken, we may observe upon the freshly fractured edge, the thin
coating of glaze which has been fused on to the body of the ware. If
the tongue be touched to tlie broken surface, it will adhere, showing
the porous and absorbent nature of the material. Eow it often hap-

EAUTHEN AND POECELAIN "WAEB. 823

pens that the shell of glaze and the body which it encloses, are not
aflfected in the same way by changes of temperature. They expand
and contract unequally when heated and cooled, the consequence be-
ing, that the glaze breaks or starts, and the surface of the plate, sau-
cer, or vessel, becomes covered with a network of cracks. Ware in
such a condition is said to be crazed. Through these cracks liquid or-
ganic matters are liable to be absorbed, which make the articles un-
cleanly and impure. Glaze that does not crack is often too soft. To
determine this, drop a small quantity of ink upon it, and dry before
the fire, and then wash it thoroughly ; if the glaze be too soft, an in-
delible brown stain wiU remain.

619. How Porcelain-ware is made. — This is the purest and most per-
fect product of the plastic art. "We are indebted for several suggestions
concerning its processes to Messrs. Haviland, of this city, whose ex-
tensive establishment in France has aflfbrded them a large experience
in the porcelain manufacture. This ware was first made in China, and is
stiQ known as China-ware. But, after long and difllcult experience, the
manufacture has at length become so perfected in Europe as greatly
to surpass the Chinese in elegance, and hence but little is now import-
ed from that country. True porcelain consists of two essentially dif-
ferent constituents, one of which is an infusible, plastic, white clay,
called Molin, or China-clay, and the other an infusible but not plastic
substance, called the Jlux, which is composed of the mineral felspar.
Kaolin alone would afibrd a porous, opaque body ; the flux, however,
softens in the heat of the baking furnace, and penetrates as a vitreous
or glassy matter the whole body of the clay, completely filling up the
pores, and covering aU the surface ; it binds the whole together into
a dense impenetrable mass. Porcelain-ware is translucent, or permits
the partial passage of light, which is due to the clay body being satu-
rated as it were with glass, as transparent paper is permeated with
on. The material is moulded with great care and nicety into the de-
sired forms, and then, placed in cases of clay made expressly to hold
and protect them, are put into the kiln or furnace, and subjected to
an intense heat for 15 or 20 hours. The articles are then withdrawn
and dipped into a glaze composed of felspar, of the same nature as
the flux, and which never contains either lead or tin. The ware is
then returned to the furnace and subjected to the most intense white
heat that art can produce, for 10 or 20 hours longer. The glaze is
thus melted into the flux, so that the porcelain has a uniform body, as
we see when it is broken. There is no accurate mode of measuring
the very high temperatures produced in these kilns, but by the method

824 PHYSIOLOGICAL EFFECTS OF FOOD.

adopted, tlie heat is estimated to run up to 21,000 degrees of the
Fahrenheit scale. The color of porcelain is milk-white, without any
tinge of blue. The quaUties which give it pre-eminence among the
clay wares, are the entire absence of porosity, the intimate union of
the glaze with the mass, and the indestructibleness of the glazed sur-
face under the knife, or when exposed to changes of temperature, and
various chemical agencies. The production of the naked porcelain-
ware in its present perfection, is one of the most signal triumphs of
inventive ingenuity and perseverance, which the history of domestic
improvement affords. But when we observe the beautiful and deli-
cate colors with which porcelain is now ornamented, we are aston-
ished at the resources of art. The paints or pigments with which ex-
quisite pictures are made upon it, consist of colored glass, stained of
various hues by metallic oxides. The coloring materials require to be
fire-proof, as they are pamted upon the ware, and then melted into the
flux or glaze by the heat of the furnace.

620. Repairing brokeu Porcelain. — Various cements are in use for
producing adhesion between fragments of broken porcelain and glass.
A very strong cement for common earthenAvare is made by boiling
slices of skim-milk cheese with water into a paste, and then grinding
it with newly slaked lime in a mortar. "White of egg will cause a
quite strong adhesion, where the objects are not exposed to moisture.
It is however improved by mixture with slaked lime. Shellac dis-
solved iu alcohol or in a solution of borax, forms a pretty good ce-
ment. Various excellent cements are to be procured, ready prepared,
of the dealers. In their anxiety to unite the fragments strongly, per-
sons are apt to defeat their purpose by applying the cement too thick-
ly, whereas the least possible quantity should be used, so as to bring
the edges most closely together. This may be aided by heating the
fragments to be joined.

VII.— PHYSIOLOGICAL EFFECTS OF FOOD.
1. Basis of the Demand eoe Aliment.

621. Creation a Continuous Work. — We are accustomed to conceive
of the creation of man as a dim miraculous event of the most ancient
time, half-forgetting that God's scheme of managing the living world
is one oi perj^etual creation. Had our earth been formed of an eternal
adamant, subject to no vicissitudes of change through all the cycles of
duration, we might perhaps well refer to the act of bringing it into
existence, as especially illustrative of creative power. But where all

BASIS OF THE DEMAND FOR ALIMENT. 325

is changing, transitory, and incessantly dissolving away, so that noth-
ing remains immutable, but God's conception of being, which the
whole universe is for ever hastening to realize, we cannot escape the
conviction of his immediate, living, omnipresent, constructive agency.
Tlie truth is, we are hourly and momentarily created, and it is impos-
sible to imagine in what respect the first act of formative power was
more wonderful or glorious, or afforded any more conspicuous display
of omnipotent wisdom, than that august procession of phenortiena by
which man, and the entire living world, are now and continually
called into being. Those material atoms which are to-day interposed
between us and destruction, are recent from chaos, — they were but
yesterday formless dust of the earth, corroded and pulverized rocks,
or fleeting and viewless gases of the air. These, through the vast
enginery of astronomic systems, whose impulses of movement spring
directly from the Almighty Will, have entered a world of organic or-
der, are wrought into new states, and made capable of nourishing the
animal body. The mingled gases and mineral dust, have become
vital aliment. The test-miracle which the Tempter of old demanded
as evidence of Godlike Power, is disclosed to the eye of science, as a
result of natural laws, for in the most literal sense, " stones are made
bread."

622. Our Systems capable of beiug understood. — That it was designed
for us to understand what goes on within the body, we are not at
liberty to doubt. Instead of being the theatre of a mysterious power
which defies investigation, we find the living system acting under
allegiance to invariable laws, and entirely amenable to investigation.
The whole course of physiological discovery has consisted in showing
that the human constitution is an embodiment and illustration of
reason. The victory of research is to understand a thing ; that is, to
bring it into agreement with reason. The mechanism of the eye was
a mystery, until its optical adaptations and purposes were discovered ;
that is, the reason of its construction. The heart was an object of
mere curious wonder and superstitious speculation, until the circula-
tion was discovered, when the reasonable uses of its parts were at
once understood. The whole scope and drift of past inquiry, and all
the considerations which cluster around the subject, lead us to expect
and demand a rational explanation of living processes. " Not many
years ago, the most acute and distinguished physicans regarded the
stomach as the abode of a conjurer; who, if respectfully treated, and
in good humor, can change thistles, hay, roots, fruits, and seeds,
into blood and flesh; but when angry, despises, or spoils the best

826 PHYSIOLOGICAL EFFECTS OF FOOD.

food." Chemistry has dispelled these crude fancies, and enabled us
to understand how such marvellous transformations occur. We are
getting daily clews to the profounder secrets of the organism ; know-
ledge is here as rapidly progressive as in any other department of
science. In this connection Dr. Draper remarks, " Since it is given
us to know our own existence, and be conscious of our own individu-
ality, we may rest assured that we h&ve what is in reality a far more
wonderful power, the capacity of comprehending all the conditions
of our life. God has formed our understanding to grasp all these
things. For my own part, I have no sympathy with those who say of
this or that physiological problem, it is above our reason. My faith
in the power of the intellect of man, is profound. Far from suppos-
ing that there are many things in the structure and functions of the
body which we can never comprehend, I believe there is nothing in it
that we shall not at last explain. Then, and not till then, will man
be a perfect monument of the wisdom and power of his Maker, a
created being knowing his own existence, and capable of explain-
ing it."

623. The living System a theatre of change. — The body of the grown
man presents to us the same unaltered aspect of form and size, for
long periods of time. "With the exception of furrows deepening in
the countenance, an adult man may seem hardly to alter for half a
hundred years. But this appearance is altogether illusory ; for with
apparent bodily identity, there has really been an active and rapid
change, daily and nightly, hourly and momently, an incessant waste
and renewal of all the corporeal parts. A waterfall is permanent, and
may present the same aspect of identity, and unchangeableness from
generation to generation ; but who does not know that it is certainly
made up of particles in a state of swift transition ; the cataract is
only a form resulting from the definite course which the changing
particles pursue. The flame of a lamp presents to us for a long time
the same appearance ; but its constancy of aspect is caused by a cease-
less change in the place and condition of the chemical atoms which
carry on combustion. Just so with man ; he appears an unchanged
being endowed with permanent attributes of power and activity, but
he is really only an unvarying form, whose constituent particles are
for ever changing. As the roar, spray, and mechanical power of the
falling water are due to changes among the aqueous particles ;
and the heat and light of the flame are due to changes among com-
bustible atoms ; so man's endowments of bodily activity, susceptibilitj',
and force, originate in atomic transformations taking place in his

BASIS OF THE DEMAND FOE ALIMENT. 327

system. As each part is brought into action, its particles perish and
are replaced by others ; and thns destruction and renovation in the
vital economy are indissolubly connected, and proceed together. It is
said, with reference to the casualties to which man is every where
exposed, that "in the midst of life we are in death," but physiologi-
cally, this is a still profounder truth ; we begin to die as soon as we
begin to live.

624. Rate at wMch the vital changes proeeedt — But very few persons
have any correct conception of the rate at which change goes on in
their bodies. The average amount of matter taken into the system
daily, under given circumstances, has been determined with a con-
siderable degree of precision. From the army and navy diet-scales of
France and England, which of course are based upon the recognized
necessities of large numbers of men in active life, it is found that
about 2^ lbs. avoirdupois of dry food per day are required for each
Individual ; of this about three-quarters are vegetable and the rest
animal. Assuming a standard of 140 lbs. as the weight of the body,
the amount of oxygen consumed daily is nearly 2j lbs., which results
from breathing about 25 or 80 hogsheads of air ; the quantity of
water is nearly 4j-'o- lbs. for the same time. The weight of the entire
blood of a full-grown man varies from 20 to 30 pounds; of this, the
lungs, in a state of health, contain about half a pound. The heart
beats, on an average, 60 or 70 times in a minute. Every beat sends
forward two ounces of the fluid. It rushes on, at the rate of 150 ft.
in a minute, the whole blood passing through the lungs every two
minutes and a half, or twenty times in an hour. In periods of great
exertion the rapidity with which the blood flows is much increased,
so that the whole of it sometimes circulates in less than a single
minute. — (Joh^tston.) According to these data, all the blood in the
body, travels through the circulatory route 600 or 700 times in a day,
or a total movement through the heart of 10,000 or 12,000 lbs. of
blood in 24 hours. To assist in carrying forward the several bodily
changes, various juices are poured out each day, according to the latest
estimates, as follows : gastric juice, 14 to 16 lbs. ; bile, 3 to 4 lbs. ; pan-
creatic juice, |- lb. ; intestinal juice, ^ lb. — (Dr. Ohambees.) At the
same time there escapes from the lungs nearly 2 lbs. of cai'lonic acid
and li oi watery vapor. The shin loses by perspiration 2^ lbs. of water,
and there escape in other directions about 2i lbs. of matter. In the
course of a year, the amount of solid food consumed is upwards of 800
lbs. ; the quantity of oxygen is about the same, and that of water taken
in various forms, is estimated at 1,500 lbs., or all together a ton and a

328 PHYSIOLOGICAL EFFECTS OF FOOD.

half of matter, solid, liquid, and gaseous, is ingested annually. We
thus see that the adult, of a half a century, has shifted the substance
of his corporeal being more than a thousand times.

625. A striking illustration of these clianges. — ^Let us take a signal
example, which, although not falling within the limits of ordinary ex-
perience, yet actually occurred in the course of nature. Thomas Pare,
of England, lived to the age of 152 years. If we take the twelve
years of his childhood, and double them over upon the succeeding
twelve years of his youth, we shaU have 140 years of adult life, or
twice the common allotment of man. Applying to his case then the
established physiological constants, we get the following startling
results of the amount of possible change in matter produced in the
lifetime of a single man. He drank upwards of a hundred tons of
water, ate nearly sixty tons of solid food, and absorbed from the air
one hundred and twelve thousand lbs. of oxygen gas to act upon that
food. There are fifteen lbs. weight of air resting upon every square
inch of the earth's surface ; of this one-fifth is oxygen, there being
therefore 3 lbs. of oxygen over every square inch of the earth, extending
to the top of the atmosphere. The daily consumption by respiration
is 2 lbs. Pake, therefore, consumed all the oxygen over a surface of
236 square feet of ground to the very summit of the earth's atmos-
phere, and generated noxious gases enough to contaminate and render
unfit for breathing ten times that space, or poison a column of air 45
miles high, having a base of nearly 2,400 square feet. If we may
indulge in a somewhat violent supposition that the whole blood which
was actually driven through his heart during that long period could
have been accumulated and measured as one mass, by forming a pro-
cession of vehicles, each taking a ton and occupying two rods of space,
such a procession would have attained the enormous length of 2,000
miles.

626. Relation between Waste and Supply. — Such is the ground of our
daily requirement for food. The annual supply of 3,000 lbs. of mattei
to the body is demanded, because in the yearly exercise of its powers
and functions 3,000 lbs. of matter have been used up or spent. It
cannot be maintained for a moment that the bodily system possesses
any power of producing or creating a single particle of the matter
which it uses ; it must receive every thing from without, and maintain
its uniform condition of weight by striking an exact balance between
waste and supply, receipt and expenditure. There are two periods in
the natural life of man when the balance between these antagonizing
forces is overturned ; in infancy, childhood and youth, the reception

BASIS OP THE DEMAND FOE ALIMENT. 329

of matter prevails over its loss, and the body steadily augments in
weight ; in old age reparation does not keep pace with decay, and the
bodily weight gradually declines. In the intervening period of adult
life these antagonizing forces are maintained with but little variation
in a state of constant equilibrium. In all the deepest recesses of the
body, in every springing muscle, and conducting nerve and connecting
tissue, and even the thinking brain, myriads of atoms are continually
passing into the condition of death, while by the profoundest law of
physiological life an exactly equal number are constantly introduced
to replace them, each of its proper kind and in its appropriate place.

626. Practical inference from these facts. — As thus the living being is
the result and representative of change on a prodigious scale, the
question of the course, rate, and regulation of those changes must be
controlling and fundamental. Matter is introduced into the system in
one condition and escapes from it in another ; the change [metamor-
plioda) that it has undergone is oxidation, or a ti'ue burning. The
solid aliment is all combustible, oxygen is the agent which burns or
destroys the food by uniting with it, and water the medium which
brings them into proper relation to act on one another. Hence the
life, activity, and multiform endowments of the organism, originate
in the chemical action and reaction of prepared matter, borrowed
temporarily from the outward world to be quickly restored to it again.
And as the supply of nutritive matter is effected through our own
voluntary agency ; as we select, mingle and prepare the nutritive mate-
rials, and control the times, frequency, quantity and condition in which
they shall be taken, and influence their physiological results in num-
berless ways, it is clear that our practice, whatever it may be, must
exert a direct and powerful influence upon the whole being ; its states
of feeling, conditions of action, health, and disease. It is desirable
therefore to gain the fuUest possible understanding of the subject.

627. Beneficent use of Hanger and Thirst. — It will be seen from the
nature of the case, that the necessities of the system for matter from
without, are pressing and momentous. If the inflowing tide of gases
be arrested but for a few moments, suffocation and death foUow. If
the liquid and solid aliments be withheld, indescribable agonies shortly
ensue, and in a few days the extinction of life. There is, therefore,
an irresistible life-demand for the supply of nutriment which cannot
be put off upon peril of existence, while the cost of nutritive matter
is laborious struggle and exertion, both of body and mind. Now it is
plain, that if in the plan of our being the bodily requirement for food
were left to the determination of reason, the purposes of nature would

330 PHYSIOLOGICAL EFFECTS OP FOOD.

be liable to continual defeat from indolence, carelessness or urgency
of occupations. The Divine Architect has therefore wisely intrenched
in the system two monitors, hunger and thirsty which are independent
of reason or will, cannot be dislodged while life lasts, and whose duty
it is to proclaim that further nourishment is required for bodUy sup-
port. And beside the sensations of hunger and thirst, imperative as
they are, there is attached to their proper indulgence a degree of
pleasure which never fails to insure attention to their demands. In
what hunger and thirst consist, what state of the stomach or vessels
produces them, or how the general nutritive wants of the sys-
tem get expressed in feeling or sensation, we do not know ; several
explanations have been offered upon this point, but they are all un-
satisfactory,

628. Impelled by the demands of the constitution food is procured,
and in several ways, which have been described, prepared for use.
"When taken into the system it is subject to various changes iu a cer-
tain natural and successive order, which will next be noticed.

2. FiEST Staoe of Digestion — Changes of Food in the Mouth.

629. The great ol«ect of Digestion, — The prepared food upon our tables
is in the form of crude, unmixed, and chiefly solid masses. Various
vegetables, breads, meats, butter, each with its peculiar constituents
and properties, are ready for use. Their physiological purpose is to
make blood, the source upon which the whole system draws for what-
ever it requires. The blood contains every thing necessary to form aU
the parts, and produce aU the peculiar hquids or secretions of the
body. It circulates rapidly through every portion of the system,
bearing all the constituents that can be required, while each part is
endowed with the special power of withdrawing from the current as
it passes along, just those particular constituents that it may require ;
compounds of lime for bones and teeth, sulphurized compounds for the
muscles, and phosphorized for the nerves, whUe various parts separate
the liquids of secretion — the glands of the mouth attracting out the
substances necessary to form saliva, those of the eyes the elements of
tears, the coats of the stomach, gastric juice, and the liver, bile. The
blood is a magazine of materials comprehensive enough for every want
of the body, and all brought to a perfectly fluid condition, so as to
flow with facility through the minutest vessels. Now, it is obvious
that the food before us must be profoundly changed before it can be-
come blood. No one element of diet contains all the necessary ma-

DIGESTION — CHANGES IN THE MOUTH.

331

terials for this purpose ; the various articles must, therefore, he mixed.
Some of the elements of food are incapahle of forming blood ; these
require to be separated, and the entire nutritive portion brought into
a state of perfect liquidity. To effect these important changes in food
is the great purpose of digestion, which presents itself to our conside-
ration in three distinct stages, commencing with transformations pro-
duced in the mouth.

680. Redacing Slecbanism of the Mouth. — The food, liquefied or soft-
ened, or with its texture relaxed, loosened, or made spongy by culi-
nary methods, is reduced to small pieces by table instruments, and
thus transferred to the mouth. An ingenious cutting and grinding
mechanism here awaits it, to complete the mechanical operation of
crushing and reducing. It consists of a double system of teeth,
planted firmly in the jaws, and made to work against each other by a
set of powerful muscles. The
teeth are so shaped and placed
as to combine cutting, crushing
and grinding, through vertical
and side movements of the low-
er jaw. The teeth are 32 in
number, and their differences
are illustrated by Fig. 113, which
represents half the lower jaw.
A shows two of the front or
cutting teeth, called incisors;
B the cuspid., canine, or dog tooth, so called from being large in the
dog and carnivorous animals, and used by them to seize and tear their
food ; G the ticuspids or double-speared, from their resemblance to a
double-headed canine tooth ; and D the molars, double-rooted, with
broad, irregular, grinding surfaces.*

631. Conditions of the flow of Saliva. — But no amount of mechani-
cal action alone wUl convert solid aliment into the fluid state. If the
food is to be dissolved, there must be a solvent or liquid to bring about
the solution. It is the office of the saliva or spittle to commence this
work. The saliva is separated from the blood and poured into the
mouth by three pairs of glands (Fig. 114). The rate at which it is
secreted varies at different times and under different circumstances.
The sight, or even the thought of dinner may fill the mouth with it,
while continued mental attention to other subjects, or a state of anxi-

*" In Latin, cuspis signifies the point of a spear ; cants, dog ; mola, a mill ; incisor
anything which cuts."

Illustration of the different kinds of Teeth.

332

PHYSIOLOGICAL EFFECTS OP FOOD.

Fig. 114.

ety, will dry it up. The movements of the mouth, as in speaking,
reading, or singing, excite its flow, but it is most copiously furnished
at times of eating, by the contact and pressure of food during masti-
cation. Hence, the glands on that side of the mouth which is most

used in mastication, secrete more than
the others. The nature of the food
causes the quantity furnished at meals
to vary exceedingly ; hard, dry ali-
ments provoking a much greater dis-
charge than those which are moist
and soft. It streams out abundantly
under the stimulation of spices, and
continues to flow after the meal is
concluded ; the secretion also goes on

^^JT^V/I |i wr 632. Properties.— The saliva is a

^k *'^ f f I f\i' clear, slightly bluish, glairy juice,

It ^1 \ ^ I readily frothing. It contains less

\ H ^ ^^^'^ ^^® P®^" cent, of saline matter,

' *l and in health is always alkaline. It

Salivary glands; a parotid, 6 submaxil- contains also an organic principle
lary, c sublingual. named ptj/alin, an albuminous sub-

stance which acts as a strong ferment. The tartar which collects
on the teeth is the residue left by evaporation of the water of the sa-
liva, and consists of earthy salts, cemented together by animal matter.
The salivary juice of the mouth is, however, a mixture of three difl:er-
ent salivas poured out by three pairs of glands. Parotid saliva is thin
and watery, so as to be readily incorporated with the food by the
teeth ; it also contains much lime. Submaxillary saliva is so thick
and glutinous that it may be readily drawn out into threads. It is
supposed to facilitate swallowing by affording a sort of anti-friction
coating to the masticated food. The sublingual saliva is more limpid,
resembling the parotid.

633. Uses of Saliva. — Saliva serves not only to moisten and lubri-
cate the mouth, and wet the aliment, so that it may assume a pasty or
pulpy condition, but it is an indispensable medium for the sense of
taste, as every thing is tasteless which the saliva cannot dissolve. By
its frothy quality it embroils globules of air, and thus serves to convey
oxygen into the stomach, where it probably plays a part in promoting
the transformations. But beyond these important effects, the saliva
actually begins the operation of digestion in the mouth. If a little

DIGESTION — CHAKGES IN THE MOUTH. 333

pnre starch be chewed for a short time, it will become sweet ; a por-
tion of it has undergone a chemical transformation, and been con-
verted into sugar. By its joint alkaline and fermentative powers,
saliva produces an almost instantaneous effect upon starch, changing
it first into sugar, and in a little longer time converting the sugar into
lactic acid. This important change seems to be effected, not by any
one of the salivary secretions, but is due to their combined action.
Saliva exerts no solvent influence upon the nitrogenous aliments. It
will thus be noticed that the first chemical attack, at the very thresh-
old of the digestive passage, is made upon that alimentary principle
which abounds most of all in our food (382). We furthermore draw a
practical inference opposed to the current opinion which assumes that
animal food, from its tough, fibroas nature, needs more mastication
than vegetable. Meat and albuminous substances require to be thor-
oughly disunited and subdivided in order that each particle may be
brought into contact with the secreting membrane of the stomach,
while bread, and substances which abound in starch, have not only to
be reduced fine, but to be well imbued with the salivary liquid. In
animal food, it is possible to supply the place of mastication by the use
of implements in the kitchen and at the table ; but culinary science
cannot compound an artificial saliva to be mixed with starchy food, so
as to save the trouble of chewing it. The changing of this substance
from a solid to a liquid form, as in gruel and sago slops, so that they
are swallowed without being delayed in the mouth and mingled with
its secretions, is unfavorable to digestion, especially if the stomach be
not vigorous. The best condition in which starch can be taken is
where the outer membrane has been ruptured by heat, and the mass
made light, as in well-baked bread and mealy potatoes (532).

684. Importance of thorough Mastication. — ^The mechanism of insali-
vation has been inserted in the mouth for a definite and important
purpose, and as the act of mastication is under the control of the will,
it is very easy to defeat that purpose. If the food be imperfectly
chewed, and hastily swallowed, or as the phrase goes, ' bolted,' the
aliment passes into the stomach crude and iU-prepared, and the whole
digestive function is just so far imperfect and enfeebled. It is of much
consequence that meals should not be precipitated, but that proper
time should be allowed to perform that portion of the digestive opera-
tion, which falls so directly under voluntary control. Besides thought-
lessness, and business pressure which pleads want of time, there is an-
other cause of inattention to this matter which deserves notice. Many
persons have placed themselves in such a false relation to nature, as

3B4 PHTSIOLOGICAL EFFECTS OF FOOD.

to imagine that they exalt the spiritual attributes of their being by
casting contempt upon the physical. Such are inclined to regard the
act of eating as a very animal and materializing operation, and any
considerations of the way it should be conducted, are apt to weigh
but lightly upon their minds. This view is false, and leads to conse-
quences practically mischievous. Dr. Combe remarks, — " Due mastica-
tion being thus essential to healthy digestion, the Creator, as if to insure
its being adequately performed, has kindly so arranged that the very
act of mastication should lead to the gratification of taste — the mouth
being the seat of that sensation. That this gratification of taste was
intended, becomes obvious when we reflect that even in eating, nature
makes it our interest to give attention to the process in whica we are
for the time engaged. It is well known, for example, that when food
is presented to a hungry man, whose mind is concentrated on the in-
dulgence of liis appetite, the saliva begins to flow unbidden, and what
he eats is consumed with a peculiar relish. "Whereas, if food be pre-
sented to an individual who has fasted equally long, but whose soul is
absorbed in some great undertaking or deep emotion, it will be swallow-
ed almost without mastication, and without sufficient admixture with
the saliva — now deficient in quantity — and consequently lie on the
stomach for hours unchanged. A certain degree of attention to taste
and the pleasures of appetite is, therefore, both reasonable and bene-
ficial ; and it is only when these are abused that we oppose the inten-
tion of nature."

635. Effect of profuse Spitting, — The salivary juices are parts of a
great water circulation of secretion and absorption. They are poured
into the mouth, not to le cast out, but to do a specific work, and then
pass into the stomach and be again absorbed. If they are habitually
ejected by spitting, the object of nature is contravened, and the sys-
tem drained of that which it was not intended to lose. In such case
the order of bodily functions is reversed, and the mouth is converted
into an organ of excretion. It is the oflBce of the kidneys and urinary
ducts to convey away a large part of the superfluous water, and all
the waste salts that require to be expelled from the body ; but if a
drain be established at the mouth, the effect is to relieve those parts
of a portion of their labor. " When the impure habit of profuse spit-
ting is indulged in, it is interesting to remark the reflected effect which
takes place in the reduced quantity of the urinal excretion, and an in-
stinctive desire for water, a kind of perpetual thirst. It is probable
that, under these disgusting circumstances, the percentage amount of
saline substances in the saliva is increased, and that, so far as that

DIGESTION — CHANGES IN THE STOMACH.

335

class of bodies is concerned, the salivary glands act vicariously for the
kidneys, and the mouth is thus partially converted into a urinary
aqueduct."— (Dr. Dkapee.)

3. Second SiAaE of Digestiok— Change of Food m the Stomach.

636. Figure and Dimensions of the Organ. — Having undergone more
or less perfectly the changes which appertain to the mouth, the food
is swallowed, and pass- Fig. 115.

ing down the esopha-
gus, or gullet, enters
the stomach. This or-
gan is a pouch-shaped
enlargement of the di-
gestive tube, having
the form shown in Fig.
115. The larger ex-
tremity is situated at /ji
the right side of the
body, and its lesser end
at the left.

tion where the esoph-
agus enters it, is termed the cardiac region (because it is in the vicin-
ity of the Jcear or heart) ; the other extremity, where the contents of
the stomach escape into the intestine, is known as the pyloric region
(from pylorus^ a gate-keeper). The capacity of the human stomach
of course varies considerably, but on an average, it wiU hold when
moderately distended about three pints. As a general rule, it is larger
among those who live upon coarse, bulky diet. In different animals
the size of the stomach varies exceedingly, according to the concen-
tration of the food upon which they live. Thus in the flesh-eating
animals it is very small, only a slight enlargement of the esophagal
tube ; while in those which feed upon herbage, it is distended into
an enormous cavity, or rather into several, as in the ruminants, cows,
sheep, &c.

637. Layersof the Stomach. — The walls of the stomach consist of
three membranous coats. The outer layer is a smooth, glistening,
whitish membrane (serous membrane), lining the abdomen, and cover-
ing all the internal organs, which it strengthens, and by its smoothness
and constant moisture, permits them to move upon each other with-
out irritation. The middle coat consists of two layers of muscular
fibres or bands, one of which runs lengthways, and the other crossways,

„, Section of the human stomacli : a esophagus ; & c cardiac

i Jiat por- orifice ; d e greater curvature ; / g lesser curvature ; h
pyloric orifice ; ij duodenum ; h bile duct..

S36 PHYSIOLOGICAL EFFECTS OF FOOD.

or around the organ. By means of these muscles the stomach may
contract its dimensions in all directions, so as to adapt its capacity to
the amount of its contents. They also give to the organ its constant
motion during digestion. The third layer of the stomach {mucous mem-
hrane) lines its internal surface. It is a soft, velvet-like memhrane,
of a pale pink color, in health, and of much greater extent than the
outer coats, by which it is thrown into folds or wrinkles. It is con-
stantly covered with a thin, transparent, viscid mucus.

638. Motious of the Stomach. — The food upon which operations have
been commenced in the mouth, is passed into the stomach, but it is
not permitted to rest. By the successive contraction and relaxation of
its muscular bands, the stomach imparts to its contents a constant
churning, or revolving motion. In the celebrated case of St.
Maktest, a Canadian soldier, whose stomach was opened by a gunshot
wound in the side, and healed up leaving a permanent orifice (gastrie
fistula), Dr. Beaumont made numerous observations of digestive
phenomena. He thus describes the movements of food within the or-
gan. " After passing the esophagal ring it moves from right to left along
the small arch ; then through the large curvature from left to right. The
bolus (swallowed mouthfiU), as it enters the cardiac, turns to the left,
descends into the splenic extremity (large extremity near the spleen),
and follows the great curvature towards the pyloric end. It then re-
turns in the course of the smaller curvature, performing similar revolu-
tions. These revolutions are completed in from one to three minutes.
They are slower at first, than after digestion is considerably ad-
vanced." The motion is not absolutely constant, but continues for a
few minutes at a time. If the food remains in the stomach three
hours it travels round and round through this circuit two or three
hundred times : — to what purpose?

639. Minute arrangements for Stomsich Digestion. — Before considering
what takes place in tlie stomach, we must have a closer view of its

mechanism. The lining layer of this organ is curi-

J-^ ' ously and admirably constructed, though it requires

^^^gote^ the microscope to see it. Magnified about 70

•WBroWSIJ^S: ^i^^sters the mucous membrane exhibits the honey-

-a^^^^.^M^/ combed appearance seen in Fig. 116. Into these

reticulated spaces, there open little cup-shaped

cavities called stomach follicles, which are about

1*200 of an inch in diameter. They are closely

packed together in the mucous membrane, so that

when it is cut through, and viewed with the microscope, it looks

DIGESTION — CHA2TGES m THE STOMACH.

337

Fig, 117.

like palisading, or like little flasks or test-tubes close packed and up-
right ; many thousands of these upright cylindrical cavities being
set in a square inch of surface. They are of different depths in
different parts of the stomach, and they terminate at the bottom in
minute closed tubes. The arrangement has been
likened to a little glove, the hand of which opens
into the stomach, while the fingers are buried in
the tissue beneath. Fig. 11 '7, represents the se-
creting foUicles in the stomacJi of a dog after
twelve hours' abstinence ; a, from the middle re-
gion of the stomach ; &, from near the pylorus ; c d,
the mouths opening upon the surface, e /, the closed
tubes imbedded in the membrane below. The walls
of these cavities are webbed over with a tissue of
most delicate bloodvessels, carrying streams of blood
— a network of veins surrounds their outlets upon
the surface of the membrane, while nerves innu-
merable pervade the whole arrangement.

640. Use of these little pocket-shaped vessels. — ^What, now, is the
purpose served by these interesting little contrivances ? It is to
separate from the blood the digestive fluid of the stomach. But they
do not eflect this directly ; another agency, — that of cells (49 6), — is
called into play. The gastric juice does not simply ooze or distil
from the blood into the stomach. It is manufactured by a determi-
nate process. "For each minutest microscopic drop of it, a cell of
complex structure must be developed, grow, burst and be dissolved."
At the bottom of the cavities, in the little tubulai' roots, the seeds or
germs of cells arise in immense numbers. Eecurring to the simile of
the glove, within each finger, at the tip and upon its sides, the cells
take origin, and, nourished by the blood, multiply and sweU untU
they are driven up in crowds into the hand or larger cavity, and hav-
ing reached their fuU maturity, are pushed out at the surface, burst,
and deliver their contents into the stomach.

641. The periodic supply of Food. — The digestive principles are thus
a product of cell-action, and into their preparation there enters the
element of time. Though short-lived, a certain period must elapse
for their production. During digestion the cells are perfected in in-
credible munbers, and yield large amounts of fluid. During fasting,
no fall-grown cells escape ; the tubes collapse, and an opportunity is
allowed for the production of a new stock of germs or ceU-grains. If
this be 60, it must follow that we cannot with impunity interfere with

15

838 PHYSIOLOGICAL BTPECTS OF FOOD.

that whicli seems a natural rule, of allowing certain intervals between
the several times of eating. Every act of digestion involves the con-
sumption of some of these cells ; on every contact of food some must
quipkly perfect themselves, and yield up their contents ; and without
doubt, the design of that periodical taking of food, which is natural to
our race, is, that in the intervals, there may be time for the production
of the cells that are to be consumed in the next succeeding acts of di-
gestion. We can, indeed, state no constant rule as to the time re-
quired for such constructions ; it probably varies according to age, the
kind of food, the general activity or indolence of life, and above all, ac-
cording to habit ; but it may be certainly held, that when the times
are set, they cannot with impunity be often interfered with ; and aa
certainly, that continual or irregular eating is wholly contrary to the
economy of the human stomach. — (Paget.)

648. Properties of Qistric Juice. — The digestive juice of the stomach
is a colorless, inodorous, slightly viscid fluid, which when removed
from the organ, retains its active properties for a long time, if kept
excluded from the air. A boiling heat destroys its activity, but freez-
ing does not. In a healthy state, it is always distinctly sour, which is
caused by an uncombined acid, usually the hydrochloric, but some-
times lactic acid. With its acid principle, the gastric juice also con-
tains a peculiar albuminous body called ' pepsin ' or ' ferment sub-
stance.' If the juice be evaporated to dryness, this pepsin constitutes
three-fourths of the solid residue. As the food is roUed round in the
stomach, it is incorporated with this juice, and changes gradually to
a pulpy semi-fluid mass. Digestion is fully under way in an hour
after the meal is taken, and is usually finished in about four.

644. Limit of Stomacli Digestion. — Recent physiological investigations
have exploded the opinion long entertained, that the stomach is the
exclusive or principal seat of digestive changes. In tracing the
properties of foods, we had occasion to divide them into two great
classes based upon fundamental differences in chemical composition —
the nitrogenous and the non-nitrogenous aliments. We find this dis-
tinction recognized by nature in arranging her plan of digestion. So
different are these two kinds of aliments that they require totally
different agents to dissolve them, — nay, solvent fluids of entirely
opposite characters. We have seen that digestion began in the mouth
with an alkaline liquid, and took eflfect only upon the non-nitrogenou3
principles. Upon proceeding to the stomach we find new conditions —
an acid liquid replaces the alkaline — the changes that commenced in
the mouth are partially or totally suspended, the non-nitrogenous com-

DIGESTION — CHAlfGES m THE STOMACH. 339

pounds remain unaltered, the gastric fluid taking effect only upon
nitrogenous substances.

645, Action of the Acid and Ferment. — If coagulated white of egg
be placed in water acidulated with hydrochloric acid, no solvent
action takes place at common temperatures for a long time. If the
temperature be raised to 150°, a slow dissolving effect begins, which
is much increased at the boiling heat. But if a Httle ' pepsin-' be
added to the liquid the solution goes on actively, so that the pepsin,
as it were, replaces the effect of a high temperature. An ounce of
water mixed with twelve drops of hydrochloric acid and one grain
of pepsin, will completely dissolve the white of an egg in two hours
at the temperature of the stomach (100°). It acts in the same manner
on cheese, flesh, vegetable gluten, and the whole nitrogenous group,
changing them to the Uquid form. These are the results of an arti-
ficial gastric juice, but they are esa^itly the same in Tcind as those
which take place in the stomach. Drs. Bidder and Schmidt, whose
researches upon digestion are the most recent and extensive, have
shown that gastric juice withdrawn from the stomach and placed in
vials, produces upon food precisely the same alterations as occur in
the stomach, only much more slowly. In consequence of the motions
of the stomach turning the aliment round and round, and the flow of
the secretions which constantly washes away the dissolved parts and
exposes fresh surfaces, the action proceeds about five times faster
within the body than without, but the nature of the results is iden-
tical.

646. What is the Digestive Ferment Substance 1 — There has been much
controversy about pepsin ; what is it ? A substance in the gastrio
fluid discovered by Sohwan a few years ago, and supposed to be a
peculiar principle specially prepared for digestive purposes. It may
be obtained from gastric juice, or by soaking the membrane of a calf's
stomach {rennet). "When proper means are taken to separate and dry
it, it appears as a yellow gummy mass. Its potency for digestive pur-
poses was proved by "Wasmann, Avho showed that a solution containing
only l-60,000th part, if slightly acidulated, dissolves coagulated albumen
in six or eight hours. Liebig- is, however, disinchned to regard pepsin
as a peculiar digestive agent. He maintains that the fermentative
change of digestion is due to minute parts of the mucous membrane of
the stomach, separated and in a state of decomposition. The surface 6f
that membrane is Uned with what is called epithelium^ composed of
exceedingly thin filmy cells ; and physiologists have discovered, that
during digestion it separates completely from the other layers of the

340 PHYSIOLOGICAL EPFBCrrS OP POOI>.

membrane. This epithelium, acted on by the oxygen swallowed in
the frothy saliva, excites the digestive fermentation attributed to
pepsin. It may be remarked that this stomach fermentation cannot
change the starch of food into alcohol and carbonic acid, nor give rise
to gases, although in morbid conditions of the organ other fermenta-
tions may arise in the alimentary mass.

647. Gastric Digestion sometliing more than Solution. — ^It was formerly
thought that digestion was simply solution, or change of alimentary
matter to the liquid state ; but late investigations inform us that nu-
tritive substances are more than dissolved, they are really altered in
properties. The nitrogenous matters are not only dissolved, but are
so modified as to remain dissolved. In ordinary solution a solid body
is changed to a liquid by the action of another liquid or solvent ; but
when the solvent is removed the dissolved substance again resumes its
sohd condition. Not so, however, in gastric digestion ; the digestive
fluid dissolves albumen, fibrin, casein ; but as it cannot accompany them
to maintain them in this state, it impresses upon them a stiU further
change, by which they continue soluble. Casein in milk, and liquid
albumen are already dissolved when swallowed ; but they are not
digested, and the first act of the stomach is to coagulate or solidify
both. They are then dissolved again, and so altered as to retain the new
condition under circumstances which would have been before impos-
sible ; while their capabihty of being absorbed, so as to pass into the
blood, is greatly increased. The term '■peptone ' has been given to
nitrogenous matters changed in this way ; thus albumen produces
an albumen-peptone ; fibrin, a fibrin-peptone ; and casein, a casein-
peptone, — substances which have lost the power of coagulating or
setting into a jelly as they did when dissolved before. It has been
found that oil plays a part in the changes by which the peptones are
produced ; so that, although oily matters are certainly not themselves
digested in the stomach, they are made to serve a useful purpose in
passing through it. The nitrogenous matters are not chemically
altered, except perhaps by combining with water.

648. Action of Saliva in the Stomach. — The alkaline saliva attacks
the sugar and starch in the mouth, and has the power of rapidly
changing the starch into sugar, and that into lactic acid. But the
food tarries only a few moments in the mouth ; charged with its alka-
line solvent, it descends into the acid region of the stomach. But
acids and alkalies cannot get on together. They either kill each
other, or if one is the sti'ongest or most abundant, it destroys the
other, though not without injury to itself. Hence, whenever the saliva

DIGESTION — CHANGES IN THE STOMACH. 341

and gastric juice come into contact, the former will be neutralized by
the excess of the latter, and a stop put to its action. Yet this does
not occur instantaneously, as the food is swallowed. The effect of the
gastric juice is superficial, acting at nrst upon the food where it comes
in contact with the bedewed coats of the stomach, whUe the saliva, in-
corporated within, is allowed a little time foi- action. In this limited
sense there may be two digestions going on in the stomach, although
gastric digestion speedily overpowers and suspends the salivary. It
is interesting to remark that lactic acid may replace hydrochloric in
stomach digestion, and that if from any cause the latter is not suppUed
in due quantity, the saliva, acting upon the contents of the stomach,
will generate the required substitute.

649. Qaantity of Gastric Juice secreted. — There has been, and indeed
there stUl is, much doubt upon this point ; but it is now generally con-
ceded that former estimates ranged much too low. The hourly de-
struction of fibrin throughout the system, in average muscular action,
has been assumed at 62 grains, and it has been found that 20
parts of gastric juice are needed to dissolve one part of dry nitro-
genous matter. To digest this quantity only, some 60 or 70 ounces
of the fluid would be required. It is obvious that the natural quanti-
ty must much exceed this, as a considerable portion vsdU be neutralized
by the saliva, and much inevitably escapes into the intestines. But
observation indicates quantities greatly higher than any calculated re-
sults. In the case of dogs, Biddee and Schimxdt found from experi-
ment the proportion to be one-tenth of their weight. This proportion
applied to man would give a daily secretion of 14 lbs. Dr. GEUira-
WALDT has however quite recently had an opportunity of determining
the quantity yielded by the human body, in the case of a stout, healthy
peasant girl, weighing 120 lbs., who had a fistulous opening in her
stomach, from childhood, that did not in the least degree interfere
with her general health. His experiments gave the astonishing result
of 31 lbs. of the gastric secretion in 24 hours, or one-fourth the weight
of the body. Making every possible allowance for error in these in-
vestigations, we must conclude that the quantity of digestive fluid
poured out each day must, at any rate, be very large.

650. Digestibility of Foods. — By this we understand their capability of
yielding to the action of the digestive forces, the joint result of seve-
ral distinct chemical agents fitted to act upon special constituents of
the food, and brought into play throughout the whole alimentary
tract. Digestion is therefore an affair of many conditions, and its re-
sults are by no means capable of being so simply stated as has been

842 PHYSIOLOGICAL EITECT8 OF FOOD.

formerly believed. What goes forward in the stomachy although of
great importance, affords but a partial view of the whole operation.
Dr. Beaumont made an admirable series of observations upon this
organ, and did much to advance the inquiry. Yet the value of his
observations was diminished by the imperfect knowledge of his time,
for we see him constantly misled by the conviction that there is but
one digestive agent, the gastric juice, and but one digestion, that in
the stomach. "We speak of his time, as if he might have lived long ago.
Measuring the time by the course of investigation, he did live long
ago. The history of science has a chronology of deeds, and marks off
time by what has been accomplished. Dtjfat, announcing the first laws
of electricity, in 1737, stood much nearer Thales, of ancient Greece,
rubbing his piece of amber, than to Prof. Moese, patenting the electro-
magnetic telegraph, in 1837. Within a quarter of a century, organic
and animal chemistry have risen to the position of separate and in-
dependent branches of science ; and it is hardly an exaggeration to say
that more has been done to elucidate the subject of digestion in the 30
years that have elapsed since Dr. Beaumont began his experiments,
than was accomplished by all the physiologists who preceded him,
though we are far enough yet from any thing like a clearing up of the
subject. Eegarding digestion comprehensively, as the blood-forming
function, we are to take into account not only the solubility of ali-
ments, but their conformability to the blood. If two substances are
dissolved with equal ease, that wiU be the more digestible which haa
the greatest similarity to some constituent of the blood. Gum, for
example, is much more easily dissolved than fat, yet the latter is a
constant constituent of blood, while the former is never found there.
Gum, to be made available, must pass through a series of transforma-
tions,— sugar, lactic acid, butyric acid, while fat passes into the circu-
lation without decomposition. " If the conformity of two alimentary
principles with the constituents of the blood is equal, the more soluble
is the more digestible. Soluble albumen and fibrin stand equally near
to the blood, both being contained in it ; as the soluble albumen is
however more readily dissolved in the digestive juices than fibrin, the
digestion of the latter is more difficult." We thus see that the diges-
tibility of foods is not the mere matter of the time of solution in the
stomach that has been generally supposed, but involves much more.
Meanwhile, Dr, Beaumont's statements of the periods which various
alimentary substances require to break down into chyme in the
stomach, may be serviceable, if received with due restrictions. We
subjoin an abstract.

DIGESTION — CHANGiS IN THE STOMACH.

343

MEAN TIMES OF CHTMIFICATION OF FOOD.

Eice

Pig's feet, sotised

Tripe, soused

Trout, salmon, fresh.

Apples, sweet, mellow
Venison, steak

Apples, sour, mellow.
Cabbage with vinegar
Codfisii, cured, dry

Eggs, fresh

Liver, beefs, fresh.

Milk

Tapioca

Milk

Turkey, wild

" domesticated

Potatoes, Irish

Parsnips

Pig, sucking

Meat hashed with )

vegetables j

Lamb, fresh

Goose

Cake, sponge

Cabbage-head

Beans, pod

Custard

Chicken, full-grown . .
Apples, sour, hard. . . .

Oysters, fresh

Bass, striped, fresh . . .
Beef; fresh, lean, rare

Corn cake

Dumpling, apple.

Eggs, fresh

Mutton, fresh....

Prepftration.

Time.

h. m.

Boiled

1

Boiled

1

Boiled

1

Boiled

1 SO

Fried

1 80

Eaw

1 80

Broiled . . .

1 35

Boiled

1 45

Eaw

2 —

Eaw

2 —

Boiled. ....

2 —

Eaw

2 —

Broiled

2 —

Boiled....

2 —

Boiled ....

2 —

Eaw

2 15

Eoasted...

2 18

Boiled

2 25

Eoasted . . .

2 30

Baked

2 30

Boiled ....

2 80

Eoasted...

2 80

"Warmed. . .

2 80

Broiled. . . .

2 30

Eoasted . . .

2 30

Baked

2 30

Eaw

2 30

Boiled ....

2 30

Baked. ....

2 45

Fricasseed.

2 46

Eaw J

2 50

Eaw

2 55

Broiled

3 —

Eoasted. ..

3 —

Broiled

3 —

Baked

8 —

Boiled

3 —

Boiled soft.

3 —

Broiled

3 —

Boiled ....

3 _

Pork, recently salted. .

Soup, chicken

Oysters, fresh

Pork, recently salted .

Pork steak

Corn bread

Mutton, fresh

Carrot, orange

Sausage, fresh

Beef, fresh, lean, dry. .
Bread, wheat, fresh. . .

Butter

Cheese, old, strong

!^gs, fresh

Flounder, fresh

Oysters, fresh

Potatoes, Irish

Soup, mutton

" oyster

Turnip, flat

Beets

Corn, green, & beans. .

Beef, fresh, lean

Fowls, domestic

Veal, fresh

Soup, beef, vegeta- (
bles, and bread (

Salmon, salted

Heart, animal

Beef, old, hard, salted
Pork, recently salted .
Cabbage, with vinegar

Ducks, wild

Pork, recently salted .

Suet, mutton

Veal, fresh

Pork, fat and lean ....

Suet, beef fresh

Tendon

Preparation.

Time.

Eaw

h. m,
3 —

Boiled ....

3 —

Eoasted...

3 15

Broiled. . . .

3 15

Broiled....

3 15

Baked

8 15

Eoasted...

3 15

Boiled ....

3 15

Broiled

3 20

Eoasted . . .

8 M)

Baked

3 80

Melted

8 80

Eaw

8 80

Hard boird

3 80

Fried

8 80

Fried

8 80

Stewed . . .

3 30

Boiled....

8 30

Boiled

3 30

Boiled

3 30

Boiled....

8 30

Boiled ....

8 45

Boiled ....

8 45

Fried

4 —

Boiled

4 —

Eoasted.. .

4 —

Broiled . . .

4 —

Boiled ....

4 —

Boiled ....

4 —

Fried

4 —

Boiled ....

4 15

Fried

4 15

Boiled

4 30

Eoasted.. .

4 80

Boiled ....

4 80

Boiled ....

4 80

Fried

4 80

Eoasted.. .

5 15

Boiled ....

5 30

Boiled ....

5 80

651. Absorption from the Stomacb. — The power possessed by liquids
and gases of penetrating and passing througti membranes, is of the
highest physiological importance ; indeed it is one of the primary
conditions of life. The little cell, the starting-point of organization,
is a closed bag — without an aperture. All its nourishment must
therefore pass through its membranous wall. So also with the perfect
animal body. Currents and tides of juices are constantly setting this
way and that, through the membranous sides of vessels. The liquefied
food is destined to pass into the blood, but there is no open door
or passage by which it can get there, and so it enters the circu-
lating vessels by striking at once through their sides. In this way,
water drank is absorbed by the minute veins distributed over the sur-
face of the stomach, and enters the circulatory current directly. This

344

PHYSIOLOGICAL EFFECTS OF FOOD.

is proved by the fact that when the outlet to the stomach is closed by
tying the pyloric extremity, water which has been swallowed rapidly
disappears from the organ, and medicines taken produce their effects
upon the system almost as promptly as under natural circumstances.
In the same way portions of sugar, lactic acid and digested nitro-
genous substances, which are dissolved in water, pass into the blood
by absorption through the stomach veins. The contents of the stomach
thus leave it in two directions, — a portion is absorbed through the
coats of the organ, while the unabsorbed matters gradually ooze
through the valvular opening that leads into the intestine.

4. Thied stage op Digestion — Changes of Food in the Intestines.

652. Digestiye Jniees of the IntvCiinal Tube. — The partially digested
food dismissed from the stomach enters the duodenum, the first por-

FiG. 118.

Gan bladder

Iiarge intestinea

Append ra of
cacum

Stomach

Small ictestinM

Small intostineg

Digestive tract in man.

DIGESTION — CHANGES IN THE INTESTINES. 345

tion of the intestinal tract (small intestine). This is a tube about 20
feet in length, with a surface of some 3,500 square inches, and is the
organ designed for finishing the digestive process. The general
scheme of the digestive tract in man is exhibited in Fig. 118. Into
the duodenum, and but a few inches from the valve of entrance, two
small tubes {ducts) open, one leading from the liver and pouring in
&i?e, and the other from the pancreas, jieldiag pancreatic juice, the
quantity of the former being much greater than of the latter. Both
of these liquids are strongly alkaline from the presence of soda. The
pancreatic juice much resembles saliva in properties; indeed the
pancreas itself is so like the salivary glands as to be grouped with
them. From the walls of the intestine there is also poured out a
fluid called the intestinal juice. It is secreted in small but variable
quantities, and is alkaline like the other secretions.

653. Changes in the Intestinal Passage. — "We find that the alkaline
digestion of the mouth is now resumed. The starch is attacked ener-
getically and rapidly changed into sugar, and that to lactic acid. The
oily substances hitherto untouched by the digestive agents are now
acted upon, not perfectly dissolved like the other alimentary matter,
but reduced to the condition of an emulsion, its particles being very
finely divided and rendered capable of absorption. It is believed that
the Pancreatic juice is the efficient or principal agent in producing
these changes ; although the bile undoubtedly contributes to the efiect
in some way not yet understood. As undigested albuminous matter
is constantly liable to escape through the pyloric gateway into the in-
testines, it seems required that they should be capable, upon emer-
gency, of completing the unfinished work, and such really appears to be
the case. Although the secretions poured into the intestine are aU
distinctly alkaline, yet they convert sugar so actively into lactic acid,
that the intestinal mass quickly becomes acidulous, — strongly so, as it
advances to the lower portion. The conditions are thus afforded for
the digestion of nitrogenous matters in the intestines, which is known
often to take place, although their ordinary function is admitted to be
digestion of non-nitrogenous substances, starch, sugar, and fat.

654. Absorption from the Intestine. — The nutriment being finely dis-
solved, is absorbed through the coats of the intestine, but not aU in
the same manner. Those substances which are completely dissolved
in water, are taken up by the veins, which are profusely distributed
over the intestinal surface, while the oily and fatty matters, which are
not so perfectly dissolved, are taken up by a special arrangement of
vessels, called the lacteals, which are extremely fine tubes arising in the

15*

346 PHTSIOLOaiCAL EFFECTS OF FOOD.

intestinal coats. They -were fonnerly supposed to be open at tlaeir ex-
tremities, but they are now seen to present fine, blunt ends to the in-
testinal cavity. How oily substances get entrance into these tubes is
an old physiological puzzle. The membrane is moist, and water repels
oil ; how then can it be imbibed ? Yet it constantly flows through.
The thing is accomplished by the agency of cells, which are produced
in vast numbers during lacteal absorption. These contain the oil, and
bursting, deliver it to the absorbent vessels. The liquid which enters
the lacteals is white, milk-like, and rich in oil. These veseels are
gathered into knots (glands), so as to be greatly prolonged without
consuming space. They finally gather into a tube (thoracic duct), and
pour their contents into a large vein near the left shoulder. In its
route, there is a disappearance of the large proportion of oil ; and
albumen, which either entered from the intestine, or has afterwards
transuded from the bloodvessels into the lacteals, is gradually
changed to fibrin, the liquid acquiring the power of clotting or coag-
ulating.

655. Constipating and Laxative Foods. — The walls of the alimentary
canal having absorbed from its contents such parts as are adapted for
nourishment, there remains an undigested residue which passes at in-
tervals from the bowels. The conditions of the intestines in reference
to the retention or ready passage of excrementitious matters, is liable
to variation from many causes. Amongst these, the nature of the
food itself is influential. Some aliments have a relaxing effect, and
others are of a binding nature, or tend to constipation, and they differ
much in the degree in which these effects are produced. These re-
sults are not, however, always due to specific active effects produced
upon the bowels ; for some foods, as meats, eggs, mUk, are considered
to be binding, because they are completely absorbed, and leave no
residue to excite the intestines to action. Those aliments are best
adapted to relieve a costive habit of body which leave much undigested
refuse to stimulate the intestines to free action. In this relation wo
may group the most important aliments, according to their reputed
characters, as follows :

THOSE OF A CONSTIPATING TENDENCY. THOSE OF A LAXATIVE TENDENCY.

Bread and cakes, from fine wheaten Wheaten bread and cakes from un-

flonr; rice, beans, peas, meats, eggs, tea, bolted flour, rye bread, corn bread, raw
alcoholic drinks. sugar, (from the molasses it contains,) fruits,

raw and cooked, and generally substances
abounding in ligneous matter,as skins, cores,
husks, bran, &c.

ITS FESTAL DESTINATION. 84Y

5. Final Destination of Foods.

656. Digested alimentary matter enters tlie circulation and becomes
Blood. This fluid is contained in a system of vessels, which extends
to all parts of the body. It has been aptly called the floating capital
of the system, lying between absorption and nutrition. Its quantity
m an average-sized man is estimated at from 20 to 24 lbs. It is whirled
as a rapid stream incessantly through the body, circulating round and
round, so as to be brought into relation with all parts (624).

657. Composition of Blood. — The composition of blood varies slightly
with age, sex, constitution, and state of health ; it is also liable to acci-
dental variations, as the supplies to it are periodic and fluctuating,
while the draught upon it, though constant, is unsteady. It consists
of about 78 per cent, water and 22 per cent, solid food dissolved in it.
When evaporated to dryness, the solid matter is found to consist of:

■ Fibrin Albumen Gelatin 93 per cent.

Fat, a little sugar, and a trace of starch 2 "

Saline matter, crash 57 "

Blood 100 "

658. Blood Discs, Globnles, or Cells. — To the naked eye blood appears
of a red color, but under the microscope it is seen as a transparent,
watery fluid, containing vast numbers of little floating cells or discs,
which are the grand instruments of change in the sanguinary fluid.
Their minuteness is amazing; fifty thousand would be required to
cover the head of a small pin, while in a single drop of blood which
would remain suspended upon the point of a fine needle, there must
be as many as three millions. And yet each of these little bodies,
which dwells down so low in the regions of tenuity that the unas-
sisted eye cannot discover it, seems to be an li' iia
independent individual, which runs a definite
career, is born, grows, performs its offices, and j^f% ^(<%
dies like the most perfect being, though the phy- ^ ^^ O^/S^ A
Biologist tells us that twenty millions of them A ' '
perish at every beat of the pulse. Figs. 119 and m^ mm
120, from a work of Dr. Hassall, represent ^®(0!i
different aspects of the blood discs, as seen under © ^
the microscope. The physiology of the blood \J
in its details is curious and most interesting, but /fs\

we have no space to consider it here, and it is _ , , ,

' Human red blood globules,

not necessary to the general view we propose showing their natural form
to give of the final influence of food upon the brought^fuHy iut'o^focM^^^
system-.

348 PHYSIOLOGICAL EFFECTS OF FOOD.

659. Grand pnrpose of the Homan Body. — The living man is pre-
sented to our consideration as an engine of power — a being capable of
producing effects. The bony framework within is broken into numer-
ous pieces to admit of free motion. A complicated and extensive ap-
paratus of contractile muscles is provided for me-
chanical movement. The nervous system binds
the whole into a co-operating unity, presided over
by the brain, which not only regulates and gov-
erns the animal nature, but is the material seat of
intellectual power. Altogether, the body dis-
closes its supreme purpose to be the reception of
impressions by the senses, and the development
and expenditure of physical and mental force.
But force cannot be produced out of nothing.
The body cannot and does not create it. As there

Blood discs, seen united ig xxo evidence that in the course of events upon

into rolls, like adherent '■

pieces of money. the earth, there is either the creation or destruc-

tion of a single atom of matter, so it is beheved
that in no absolute sense is force either created or destroyed. It
changes states, disappears, and remains latent or reappears in different
forms, but its total amount is thought to correspond with the total
quantity and fixed properties of matter. Power is thus not literally
generated in the body, but is developed or made active there by cer-
taia definite causes. It is desirable to understand, as far as we may
be able, the conditions of its production.

660. Food produced by the action of Forces.— The stream of aliment
which fiows into the system from without, consists mainly of carbon,
oxygen, hydrogen, and nitrogen. These, when left to the undisturbed
play of their attractions, take the compound form of water, carbonic
acid, and ammonia, natural and permanent conditions of equilibrium
from which they are not inclined to depart. These three substances
constitute the chief nourishment of the vegetable kingdom. Through
the roots, or by direct absorption from the air, they get admission into
the vegetable leaf, the crucible of nature, where organized compounds
originate. They are there decomposed and thrown into new arrange-
ments, forming new compounds. Simple substances, those having few
atoms, are destroyed, and the atoms built together into more complex
substances, with greater numbers of atoms. The changes are from
the lower to the higher, ascending, constructive. Now carbonic acid,
"water, and ammonia cannot separate and re-arrange themselves^ nor can
they be separated and re-aiTanged without an enormous expenditure of

ITS FINAL DESTINATION. 349

power. Man with his utmost skill cannot imitate the first step in the
chemistry of the plant. Every green leaf upon the surface of the re-
volving globe decomposes carbonic acid every day at the ordinary
temperatures, setting free the oxygen, a thing which the chemist cannot
accomplish with all the forces at his command. ISTor are we to sup-
pose that the leaf itself does it ; that cannot originate force any more
than the water-wheel or the steam-engine ; it must be acted upon.
Carbonic acid is only decomposed in the leaf during the daytime by
the power of light ; the effect is produced by solar radiations. All
true aliments originate under these circumstances in vegetation.
Though we consume flesh, we only go by the route of another animal
back to the plant ; our food is all fabricated there. Animal life begins
and is sustained by compounds which are the last and highest product
of the creative energy of plants. The animal is nourished from its
blood, but it does not in any sense produce it, it only gives it form ;
the constituents of blood are generated in plants, stored up in their
seeds, which are the crowning results of vegetable life, and with the
maturity of which, most plants employed by man, as food, perish.
Aliments are thus composed of atoms that have been forced from a
lower into a higher combination in plants, and in their new state they
represent the amoxmt of force necessary to place them there. The
particles of sugar, starch, oil, gluten, «&c., are little reservoirs of
power, resembling bent or coiled springs, which have been wound up
into organic combination by nothing less than solar enginery. It is
these materials, dissolved in water, that constitute blood, and with
which the animal system is kept perpetually charged. The circulating
medium of the liviog body is of celestial coinage ; it is a dynamic pro-
duct of astronomic agencies. The energies of the stellar universe it-
self are brought into requisition to estabUsh the possible conditions of
terrestrial life (3).

661. How Food produces Animal Force. — ^Food represents force, but
it is force in a state of equiUbrium or rest, just like a pond of water
enclosed on all sides. But if we make an outlet to the pond, its force
at once becomes active and available. So the quiescent force of food
is to become active animal power ; but how ? There enters the vital
current incessantly from the outward world another stream of matter,
not solid but gaseous, oxygen from the air, which came by the route of
the lungs. It is the office of this agent to unlock the organic springs
throughout the vital domain. We have stated before that oxygen is
an agent of destruction (284) ; it is the foe of the organized state.
The first step of growth, and the production of food in the leaf, con-

350 PHYSIOLOGICAL KPPECT3 OF FOOD.

sisted in forcing carbon and hydrogen out of its grasp ; but in the ani-
mal fabric it is destined to take possession of them again. The food,
as we have seen, is not destroyed in digestion, it is only dissolved ; but
in the blood and tissues it is destined to undergo a series of deeompo-
sitions, which are marked by the production of compounds richer and
richer in oxygen, until finally they are thrown from the body loaded
to their utmost capacity with this substance. The course of changes
that characterizes the animal is descending, from higher to lower, from
the complex to the simple, from compounds containing comparatively
little oxygen to those containing much. In this decomposition of ali-
ment, under the influence of inspired oxygen, bodily force originates.
We see every day that steam power results from the destruction of
fael under the boiler by atmospheric oxygen, and that electric power
comes from the oxidation or destruction of metal by the liquid in the
galvanic battery ; but it is equally true that the conditions of human
power are the oxidation of food and its products in the system. It is
not from the mere introduction of aliment into the system that we
obtain strength and nourishment, but from its destruction. A portion
of food, of course, serves to buUd up the bodily fabric, but it only
continues in that state transiently; it is aU finally decomposed and
dissevered into the simplest inorganic forms.

662. Destructive agency of Oxygen. — The body is built of aliment,
which gives rise by its destruction to force, but the immediate active
agent which destroys the body, and thus develops force, is oxygen
withdrawn from the air. From the moment of birth to the moment
of death, every living animal is incessantly occupied in introducing
this element into the body to maintain the conditions of force by its
constant destructive action. If the current of oxygen flowing toward
a hmb, a muscle, or the brain, be arrested, those parts instantaneously
lose their power of action. The body of every animal is kept charged
with this gas every instant of its active existence. If a man is aban-
doned to the action of air, that is, if no other matter is taken into
his system, we quickly discover the peculiar agency of oxygen. He
loses weight at every breath. Inspired oxygen, borne by the arte:-ial
current, cuts its destructive way through every minutest part, decom-
posing the constituents of both blood and tissues. The fat is consumed
first, then the muscular portions, the body becoming reduced and
emaciated, yet the waste must proceed if life is to last. The brain is
attacked, its offices disturbed, delirium supervenes, and there is an end
of life. "We call this starvation ; it is a conditim in which " atmos-
pheric oxygeoi acts hke a sword, which gradually but irresistibly pen-

ITS nQSTAL DESTINATION. 351

etrates to the central point of life, and puts an end to its activity."
— (LiEBiG.) Had food been regularly introduced, it would have
opposed a constant resistance to that agent, that is, it would have
offered itself for destruction and for repair, and thus have protected
the system from the fatal inroading effects of oxygen.

663. Combustion vrithin the Body. — The term combmtion is com-
monly applied to that rapid combination of oxygen with other ele-
ments, by which a high heat is produced, accompanied with light.
But the essence of the process is, not its rate, but the nature and di-
rection of the changes. It may go forwarc at aU degrees of speed,
the effects being less intense the slower it proceeds. The changes that
go on in the body are the same as tliose in the stove. There is loss of
oxygen, destruction of combustible matter, oxidized products (car-
bonic acid and water), and the development of heat, in one case
rapidly, in the other slowly ; in both cases, in proportion to the amount
of matter changed. The destruction of aliment iu the body is, there-
fore, a real burning ; a slow, silent, regulated combustion.

664. All Foods not equally Combustible. — Foods are destined to be
burned in the body, but they do not all consume alike. We found it
necessary, at the outset, to divide the aliments into two great groups,
based upon their composition — thoso which contain nitrogen, and
those which do not. "We next found a twofold digestion, in which
this distinction is recognized ; an acid digestion for nitrogenous mat-
ters, and an alkaline digestion for the others. And we are now to
find that this fundamental difference is observed in their final uses, —
in their relations to oxygen, and modes of destruction. All foods are
capable of being burned, and are burned ; but there is a wide difference
in their facility of undergoing this change, and upon that difference
depends the very existence of the bodily structure. It is clear that if
certain substances are to be burned in the blood, and others are to es-
cape from it unburned, the latter must be less combustible than the
former, or they would aU be consumed together. Accordingly the
non-nitrogenous bodies, sugar, starch, oil, are easy of combustion ;
while the albuminous compounds are burned with much greater
difiiculty ; these latter are drawn out of the blood, and used in the
construction of all the tissues of the system. The bodily structures,
which require to have a certain degree of permanence, are built of ni-
trogenous substances, having a low combustibility. The case is roughly
represented by what occurs in a common stove. Both the fuel and
the stove itself are combustible. The iron is capable of being burned
up, under proper circumstances, as truly as the wood or coal ; and in

3S2 PHYSIOLOGICAL EFFECTS OF FOOD.

a long time stoves are partially so consumed, or as the phrase is,
' burned out.' Yet the fuel is so much more easily burned, that the
iron serves as a structure to retain, enclose, and regulate the combus-
tion. The difference in capability of burning between the non-nitro-
genous and the nitrogenous aliments, may not be so great as between
iron and wood ; yet it is fully sufficient for the purposes of the animal
economy.

665. Nitrogeii Lowers the Comljustibility of Food. — Of all the elements
of the animal body, nitrogen has the feeblest attraction for oxygen ;
and what is still more remarkable, it deprives all combustible ele-
ments with which it combines, to a greater or less extent, of the
power of combining with oxygen, or of undergoing combustion. Every
one knows the extreme combustibility of phosphorus, and of hydrogen ;
but by combining with nitrogen, they produce compounds entirely
destitute of combustibility and inflammability under the usual circum-
stances. Phosphorus takes fire at the heat of the body ; while the
phosphuret of nitrogen only ignites at a red heat, and in oxygen gas,
but does not continue to burn. Ammonia, a compound of nitrogen
with hydrogen, contains 75 per cent., by bulk, of the highly combusti-
ble hydrogen ; but in spite of this large proportion of an element so
inflammable, ammonia cannot be set on fire at a red heat. Almost all
compounds of nitrogen are, compared with other bodies, difficultly
combustible, and are never regarded as fuel, because when they do
burn, they develop a low degree of heat, not sufficient to raise the
adjacent parts to the kindling point. So with albuminous principles
in the blood and tissues ; they are placed so low in the scale of com-
bustibility, that the other group of aliments is attacked and destroyed
first. " Without the powerful resistance which the nitrogenous con-
stituents of the body, in consequence of their peculiar nature as com-
pounds of nitrogen, oppose, beyond all other parts, to the action of the
air, animal life could not subsist. Were the albuminous compounds
as destructible or liable to alteration by the inhaled oxygen, as the
non-nitrogenous substances, the relatively small quantity of it daily
supplied to the blood by the digestive organs, would quickly disappear,
and the slightest disturbance of the digestive functions would, of ne-
cessity, put an end to life." — (Liebig.)

666. Heat-prodncing and Tissne-making Foods. — In considering the
final uses of foods, we are to preserve the distinction with which we
began. The non-nitrogenous aliments, by their ready attraction for
oxygen, seem devoted to simple combustion in the system, with only
the evolution of heat ; while the albuminous compounds are devoted

PRODUCTION OF BODILY WAEMTH. 353

to the production of tissue. The first class is hence called the heat-
producing, calorifi&nt, or respiratory aliments, while the second is
designated as the tissue-forming, plastic, or nutritive aliments (430).
This distinction is to he received with due limitation, for on the one
hand, fat, which stands at the head of the heat-producers, is deposited
and retained in the cells of the tissues, without being immediately con-
sumed, and probably serves other important purposes beside produc-
ing heat (722) ; on the other hand, some nitrogenous substances (as
gelatin, for example,) do not reproduce tissue, while those which are
worked up into the structure of the system, in their final dissolution,
minister also to its warmth. These facts, however, do not disturb the
general proposition. That it is the chief purpose of sugar, starch, veg-
etable acids, and fat, to be destroyed in the body for the generation
of warmth ; while albumen, fibrin, and casein, furnish the material for
tissue, and in their destruction give rise to mechanical force, or animal
power, — is a fact of great physiological interest and importance, now
regarded as established, and which was first distinctly enunciated, il-
lustrated, and confirmed, by LrEsia.

6. Peodtjotion of Bodilt Waemts.

667. Constant Temperatnre of the Body. — The influence of tempera-
ture over chemical transformations is all-controlling ; they are modified,
hastened, checked, or stopped, by variations in the degrees of heat.
The living body is characterized by the multiplicity and rapidity of its
chemical transmutations. Indeed, the whole circle of life-functions
is dependent upon the absolute precision of rate with which these vi-
tal changes take place. A standard and unalterable temperature is
therefore required for the healthy animal organism, as a fundamental,
controlling condition of vital movements — a certain fixed degree of
heat to which aU the vital operations are adjusted. This standard
temperature of health in man, or blood heat, varies but slightly from
98°, the world over. Yet the external temperature is constantly
changing, daily with the appearance and disappearance of the sun, and
annually with the course of the seasons. We are accustomed to fre-
quent and rapid transitions of temperature, from 30 to 60 degrees, by
the alternations of day and night, sudden changes of weather, and by
passing from warmed apartments into the cold air of winter. The circle
of the seasons may expose us to a variation of more than a hundred
degrees, while the extreme limits of temperature to which man is nat-
urally sometimes subjected in equatorial midsummer, and arctic mid-

354 PHYSIOLOQIOAL EFFECTS OF FOOD.

■winter, embrace a stretch of more than 200° of the thermometric scale.
Yet through all these thermal vicissitudes, the body of man in health
varies but little from the constant normal of 98°.

668. How the Body loses Heat. — In view of these facts, it has been
maintained that the living body possesses some vital, mysterious, in-
ternal defence against the influence of external agents ; indeed, that it
is actually emancipated from their effects. But this is wholly errone-
ous ; the body possesses no such exemption from oatward forces ; it is
a heated mass, which has the same relation to surrounding objects as
any other heated mass ; when they are hotter than itself it receives
heat, when they are colder it loses heat ; and the rate of heating or
cooHng depends upon the difference between the temperature of the
body, and that of the surrounding medium. But in nearly all circum-
stances, the temperature of the body is higher than the objects around.
It is, therefore, almost constantly parting with its heat. This is done
in several ways. The food and water which enters the stomach cold,
are warmed, and in escaping carry away a portion of the heat. The
air introduced into the lungs by respiration is warmed to the tempera-
ture of the body, and hence every expired breath conveys away some
of the bodily warmth. This loss is variable ; as the temperature of
the outer air is lower, of course more heat is required to warm it.
The body also parts with its heat by radiation, just like any other ob-
ject, and much is likewise lost by the contact of cold air with the skin,
which conducts it away, a loss which is considerable when the air is
in motion! This rapid carrying away of heat by air-currents, explains
why it is that our sensations often indicate a more intense cold than
the thermometer. But, lastly, the body loses heat faster by evapora-
tion than in any other way. This takes place from the surface of the
skin, and from the lungs. About 8^ lbs, of water are usually estimated
to be exhaled in the form of vapor daily, of which one-third escapes
from the lungs, and two-thirds from the skin, which is stated to have
28 miles of perspiratory tubing, for water-escape (797). We shall appre-
ciate the extent of this cooling agency, by recalling what was said of
the amount of heat swallowed up by vaporization (68). The water of
the body at 98° receives 114° of sensible heat, and then 1000° of latent
heat, before it is vaporized ; hence it carries away 1114° of heat from
the body.

669. How the Body prodaccs Heat. — To keep the system up to the
standard point, notwithstanding this rapid and constant loss, there
must be an active and unremitting source within. Heat-force cannot
be created out of nothing ; it must have a definite and adequate cause.

PEODUCTION OP BODILY WAHMTH. 355

It is by the destruction of food through respiration, that animal heat
is generated. The main physiological difference between the warm
and the cold-blooded animals is, that the former breathe actively,
while the latter do not. It is natural, therefore, to connect together
the distinctive character of breathing, with the equally distinctive
character of greater warmth ; to suppose that the incessant breathing
so necessary to life, is the source of the equally incessant supply of
heat from within, so necessary also to the continuance of life ; and
this connection is placed, beyond all doubt, when we attend to the
physical circumstances by which the change of starch and fat into
carbonic acid and water is accompanied in the external air. If we
burn either of these substances in the air or in pure osygen gas, they
disappear and are entirely transformed into carbonic acid and water.
This is what takes place also within the body. But in the air, this
change is accompanied by a disengagement of heat and Hght, or, if it
take place very slowly, of heat alone without visible light. Within
the body it must be the same. Heat is given off continuously as the
starch, sugar and fat of the food,, are changed within the body into
carbonic acid and water. In this, we find the natural source of animal
heat. Without this supply of heat, the body would soon become
cold and stiff. The formation of carbonic acid and water, therefore,
continually goes on ; and when the food ceases to supply the materials,
the body of the animal itself is burned away, so to speak, that the
heat may stUl be kept up. — (JoHS'STOjr.) There are certain periods
in the history of the plant, as germination and flowering, when oxy-
gen is absorbed, combines with sugar and starch, and produces car-
bonic acid and water. In these cases, the temperature of the seed
and the flower at once rises, and becomes independent of the sur-
rounding medium.

670. Effect of breathing rarified Air. — The doctrine, that animal heat
ia due to oxidation in the system, is strikingly illustrated by what might
be termed starving the respiration. As cold is felt from want of
food, so also it is felt from want of air. In ascending high mountains, the
effect upon the system has been graphically expressed as ' a cold to the
marrow of the bones,' a difficulty of making muscular exertion is ex-
perienced ; the strongest man can scarcely take a few steps without
resting ; the operations of the brain are interfered with ; there is a pro-
pensity to sleep. The explanation of aU this is very clear. In the
accustomed volume of air received at each inspiration, there is a less
quantity of oxygen in proportion as the altitude gained is higher.
Fires can scarce be made to bum on such mountain tops ; the air is

356 PHTSIOLOGICAl EFFEOTS OF FOOD.

too thia and rare to support them ; and so these combustions which
go on at a measured rate in the interior of the body, are greatly re-
duced in intensity, and leave a sense of penetrating cold. Such jour-
neys, moreover, illustrate how completely the action of the muscular
system, and also of the brain, is dependent on the introduction of air ;
and under the opposite condition of things, where men descend in
diving-bells, though surrounded by the chilly influences of the water,
they experience no corresponding sensation of cold, because they are
breathing a compressed and condensed atmosphere. — (Dr. Deapee.)

671. How the unequal demands for Heat are met. — The steady main-
tenance of bodUy heat being a matter of prime physiological necessity,
we find it distinctly and largely provided for by a class of foods pre-
pared in plants and devoted to this purpose. Much the largest por-
tion of food consumed by herbivorous animals, and generally by man,
is burned at once in the blood for the production of heat. But there
are varying demands upon the system at different places and seasons,
and the provision for these is wise and admirable. First, as the cold
increases, the atmosphere becomes more dense, the watery vapor is
reduced to its smallest proportion, and pure air occiapies its place,
so that breathing furnishes to the body a considerably higher per-
centage of oxygen in winter than in summer, in the colder regions of
the north, than in the warmer vicinity of the equator. On the other
hand, there is an important difference among the heat-producing
principles of food. They vary widely in calorific power. The fats
and oUs head the list ; they consist almost entirely of the two
highly combustible elements, carbon and hydrogen, containing from
Y7 to 80 per cent, of the former, to 11 or 12 of the latter. Starch
occurs next in the series, then the sugars, and lastly the vegetable
acids and lean meat. Liebig states their relative values, or power
of keeping the body at the same temperature during equal times, as
follows : To produce the same effect as 100 parts of fat, 240 of starch
will be required, 249 of cane sugar, 263 of dry grape sugar and milk
sugar, and 770 of fresh lean flesh. We shall illustrate this point more
clearly, when we come to speak of the nutritive value of foods (743).
A pound of fat thus goes as far in heating as 2| lbs. of starch, or 7^ lbs.
of muscular flesh. In regions of severe cold, men instinctively resort
to food rich in fatty matters, as the blubber and train oil, which are
the staples of polar diet. Bread, which consists of starch and gluten,
and which, therefore, as shown by the above illustration, falls far be-
low oleaginous matter in calorifying power, is found to be very insuflS-
cient in the arctic regions for the maintenance of animal heat.

PRODUCTION OF BODILY WARMTH. 357

All breads are, however, not alike in this respect, for the Hudson's
Bay Traders have found, according to Sir John Riohaedson, that
Indian corn bread, which contains about nine per cent, of oH, is de-
cidedly more supporting than wheaten bread. Dr. Kane, in the nar-
rative of his last arctic expedition, remarks : " Our journeys have
taught us the wisdom of the Esquimaux appetite, and there are few
among us who do not relish a slice of raw blubber, or a chunk of
frozen walrus beef. The liver of a walrus, eaten with little slices
of his fat, of a verity it is a delicious morsel. The natives of South
Greenland prepare themselves for a long journey in the cold by a
course of fi-ozen seal. At Upernavick they do the same with the
norwhal, which is thought more heat-making than the seal. In.
Smith's Sound, where the use of raw meats seemed almost inevitable,
from the modes of living of the people, walrus holds the first rank.
Certainly, its finely condensed tissue, and delicately permeating fat —
oh ! caU it not blubber — is the very best kind a man can swallow ; it
became our constant companion whenever we could get it." On the
contrary, the inhabitants of warmer regions live largely upon fruits,
which grow there in abundance, and in which the carbonaceous matter,
according to Liebig, falls as low as 12 per cent. The demands of ap-
petite seem to correspond closely with the necessities of the system ;
for while oranges and bread-fruit would be but poor dietetical stuff
for an Icelander, the West Indian would hardly accept a dozen tallow
candles as a breakfast luxury ; but reverse these conditions and both
are satisfied. A knowledge of the calorifying powers of the various
elements of food, and of the proportions in which they are found,
enables us to modify our diet according to the varying temperature of
the seasons.

672. Begnlation of Bodily Temperature. — The question naturally arises,
why is it that when the external temperature is 100° and even higher
for a considerable time, and the system is constantly generating ad-
ditional heat, that it does not accumulate, and elevate unduly the
bodily temperature ? How is it constantly kept down in health to
the limit of 98° ? This is efifected by the powerful influence of evapo-
ration from the lungs and skin, already referred to in speaking of the
way the body loses heat (668). The large amount of water daily
drank and taken in combination with the food, is used for this pur-
pose as occasion requires. The lungs exhale vapor quite uniformly,
but the quantity thrown off from the skin varies with the condition
af the atmosphere. When the air is hot and dry, evaporation is ac-
tive, and the cooling effect consequently greater. During the heat of

858 PHYSIOLOGICAL EFFECTS OF FOOD.

summer, mucli water evaporates from the skin, and a correspondingly
small proportion by the kidneys ; but in the cold of winter there is
less cutaneous exhalation, the water of the body is not vaporized, but
chiefly escapes in the liquid form by kidney excretion. As human
invention has made the steam-engine beautifully automatic and self-
regulating, and as stoves have been devised which adjust their ov?n
rate of combustion, and thus equalize the heat, so we find the living
body endowed with a matchless power of self-adjustment in regard to
its temperature, by the simplest means.

673. Houses and Clothing replace Food. — We have seen that the neces-
sity for the active generation of heat within the body is in proportion
to the rapidity of its loss. If the conditions favor its escape, more
must be produced ; if on the other hand the surrounding temperature
be high, the loss is diminished, and there is less demand for its evo-
lution in the body. We have also described the various expedients
by which heat is produced in our dwellings in winter, thus forming
an artificial summer climate. Clothing also acts to protect the body
from loss, and enable it to preserve and economize the heat it gen-
erates. Hence in winter we infold ourselves in thick non-conducting
apparel. Clothing and household shelter thus replace aliment ; they
are the equivalents for a certain amount of food. The shelterless a,nd
thinly clad require large quantities of food during the cold of winter
to compensate for the rapid loss of heat. They perish with the same
supply that would be quite sufficient for such as are adequately clothed
and well-housed. " It is comparatively easy to be temperate in warm
climates, or to bear hunger for a long time under the equator ; but
cold and hunger united very soon produce exhaustion. A starving
man is soon frozen to death."

674. Times of Life when Cold is most fatal. — The potent influence of
temperature upon life must, of course, be most strikingly manifested
where there is least capability of resistance — in infancy and old age.
During the first months of infant life the external temperature has a
very marked influence. It was found in Brussels that the average
infant mortality of the three summer months being 80, that of January
is nearly 140, and the average of February and March 125. As the
constitution attains vigor of development, the influence of seasons
upon mortaUty becomes less api^arent, so that at the age of from 25
to 30 years, the difference between the summer and winter mortality
is very slight. Yet this diffference reappeai's at a later period in a
marked degree. As age advances, the power of producing heat de-
clines, old people draw near the fire and complain that ' their blood is

PE0DX7CTI0N OP BODILT WAIIMTH. 859

chill.' The Brussels statistics show that the mortality between 50
and 65 is nearly as great as in early infancy ; and it gradually becomes
more striking until at the age of 90 and upwards the deaths in Jan-
nary are 158 for every 74 in July. It has been observed in hospitals
for the aged, that when the temperature of the rooms they occupy in
winter sinks two or three degrees below the usual point, by this small
amount of cooling the death of the oldest and weakest, males as well
as females, is brought about. They are found lying tranquilly in bed
without the slightest symptoms of disease, or the usual recognizable
causes of death.

675. Diet and the daily changes of Temperature. — The heat of inani-
mate objects, as stones, trees, &c., rises and falls with the daily varia-
tions of temperature. The hving body would do the same thing if it
did not produce its own heat independently. If we disturb the calp-
rifying process, the body becomes immediately subjected to the muta-
tions of external heat. In starving animals, this temperature rises
and falls with the daily rise and nightly fall of the thermometer, and
this response of the living system to external fluctuations of heat is
more and more prompt and decided as the heat-producing function is
more and more depressed. As the system is unequally acted upon by
the daily assaults of cold, it becomes necessary to make provision
against the periods of severest pressure. In the ever admirable
arrangements of Providence, the diurnal time of lowest temperature
is made to coincide with the time of darkness, when animals resort to
their various shelters to rest and recruit, and are there most perfectly
protected from cold. Dr. Deapee has suggested also that the diet of
civilized man is instinctively regulated with reference to the daUy
variations of temperature. He says : " In human communities there is
some reason beyond mere custom which has led to the mode of dis-
tributing the daily meals. A savage may dispatch his glutinous repast
and then starve for want of food ; but the more delicate constitution
of the civilized man demands a perfect adjustment of the supply to
the wants of the system, and that not only as respects the Mnd, but
also the time. It seems to be against our instinct to commence the
morning with a heavy meal. We l)reaTc fast, as it is significantly
termed, but we do no more ; postponing the taking of the chief supply
untU. dinner, at the middle or after part of the day. I think there
are many reasons for supposing, when we recall the time that must
elapse between the taking of food and the completion of respiratory
digestion, that this distribution of meals is not so much a matter of
custom, as an instinctive preparation for flie systematic rise and f^U

360 PHTSIOLOGICAIi EFFECTS OF FOOD.

of tomperature attending on the maxima and minima of daily heat.
The hght breakfast has a preparatory reference to noonday, the solid
dinner to midnight."

7. Peodtjotion of Bodily STEEisraTH.

676. Amount of mecbaiiical force exerted by the Body. — "We have seen
how the double stream of alimentary and gaseous matter which enters
the body incessantly gives rise to heat, an agent which we every day
convert into mechanical power through the medium of the steam engine.
Sufficient heat is produced in this way annually by an adult man, if it
were liberated under a boUer, to raise from 25,000 to 30,000 lbs. of
water from the freezing to the boiling point. But the body also
generates mechanical force directly, producing effects which present
themselves to us in a twofold aspect ; those which are involuntary,
constant, and connected with the maintenance of life, and the volun-
tary movements which we execute under the direction of the will,
for multiplied purposes and in numberless forms. That which produces
movement is force, and there can be no movement without an adequate
force to impel it. If a load of produce or merchandise is to be trans-
ported from one place to another, we all understand that force must
be applied to do it. And so with the human body ; not a particle of
any of its flowing streams can change place, nor a muscle contract to
lift the hand or utter a sound, except by the application of force.
We may form an idea of the amount generated to maintain the invol-
untary motions essential to life, by recalling for a moment their num-
ber and extent. "We make about nine millions of separate motions of
breathing, introducing and expelling seven hundi'ed thousand gallons
of air in the course of a year. At the same time the heart contracts
and dilates forty millions of times — each time with an estimated force
of 13 lbs., whUe the great sanguinary stream that rushes through the
system is measured by thousands of tons of fluid driven through the
heart, spread through the lungs, and diffused through the minute ves-
sels, beside the subordinate currents and side-eddies which traverse
various portions of the body, and contribute essentially to its action.
The system not only generates the force indispensable for these effects,
but also an additional amount which we expend in a thousand forms
of voluntary physical exercise, labor, amusement, (fee. A good laborer
is assumed to be able to exert sufficient force (expended as in walking)
to raise the weight of his body through 10,000 feet in a day. Smeaton
states, that working with his arms he can produce an effect equal to

PEODUGnON OF BODILY STRENGTH. 361

raising SVO lbs. ten feet high, or 3,700 lbs. one foot high in a minute
for eight hours in the day.

677. Tissues destroyed la producing Force. — The expenditure of force
in labor, if not accompanied by a sufficiency of food, rapidly wears
down the system, — there is a loss of matter proportioned to the
amount of exertion, and which can only be renewed by a correspond-
ing quantity of nourishment. The parts brought into action during
exercise are of course those possessing tenacity, firmness, and strength ;
that is, the tissues and organized structures. The unorganized parts,
such as water and fat, which are without texture, have no vital pro-
perties, and cannot change their place or relative position by any in-
herent capability. It is the bodily tissues that are called into action,
and these undergo decomposition or metamorphosis in the exact ratio
of their active exercise. We have stated that the motions within the
system are numerous and constant. If we look on a man externally,
he is never wholly at rest ; even in sleep there is scarcely an organ
which is not in movement or the seat of incess5,nt motion ; yet the
destruction of parts is correspondingly active. It may vary perhaps
in different constitutions, in different parts of the system, and under
various circumstances, but it goes on at a rate of which we are hardly
conscious. Ohossat ascertained the waste in various animals to be an
average of l-24th part of their total weight daily ; and Schmidt deter-
mined it to be, in the case of the human being, l-23d of the weight.
Professor Johnston says : " An animal when fasting wiU lose from a
fourteenth to a twelfth of its whole weight in twenty-four hours.
The waste proceeds so rapidly that the whole body is now believed
to be renewed in an average period of not more than thirty days.

678. Destinatioii of the Nitrogenous Principles. — The basis of animal
tissue is nitrogen. The muscular masses are identical in composition
with the nitrogenous principles of food, albumen, casein, gluten.
Those substances have, by digestion, become soluble; that is, they
have all assumed the form of albumen, and thus enter the blood. In
this liquid, whose prime function is to nourish the system, albumen is
always present in considerable quantity. When the fibrin and red-
coloring matter {dot) is removed from blood, the watery serum or
plasma remains, containing albumen, which coagulates like white of
egg by heat. Albumen is the universal starting point of animal nutri-
tion ; it is the liquid basis of tissue and bodily development through-
out the entire animal kingdom. We see this sti-ikingly illustrated by
what takes place in the bird's egg during incubation. Under the in-
fluence of warmth, and by the action of oxygen, which enters through

16

862 PHTSIOLOGIOAL KPJ^ECTS OF J-OOD.

the porous shell, under the inflaence therefore of the same conditions
which accompany respiration, all the tissues, memhranes and bones,
(by the aid of lime from the shell,) are developed. The foundation
material from which they are all derived is albumen, and it is the
same with the growth and constant reproduction of our own bodies
during life. The course of transformation by which albumen is con-
verted into the various bodily tissues, has not yet been certainly
traced. But it is now universally agreed that it is the nitrogenous
principles of food, — those of low combustibility, which are employed
for the nutrition of animal structures — the reparation of tissue-waste.
Those substances furnish the instruments of movement, and minister
directly to the production of mechanical force. Their design is two-
fold, to form and maintain the bodUy parts in strength and integrity,
and to be finally destroyed for the development of power.

679. Action of Oxygen npon the Tissnes. — Oxygen plays the same im-
portant part in tissue destruction as in the simple development of heat
by combustion of respiratory food. It is the agent by which the
moving parts are decomposed and disintegrated. The muscles are
paralyzed if the supply of arterial blood containing the oxygen which
is to change them, and the nutritive matter which is to renew them,
be cut off. On the other hand, if there is rapid muscular exercise
and consequent waste, the circulation is increased and the breathing
quickened, by which the supply of oxygen is augmented. The
changes of the tissues in action are, moreovei*, retrogressive, and
downwards to simpler and simpler conditions. The products of
metamorphosis are oxidized, and then made soluble in the blood by
which they are promptly conveyed away, and thrown out of the body
by the liquid excretion. It is thus that oxygen, by slow corrosion and
burning of the constituents of the muscles, gives rise to mechanical
force. But oxidation is invariably a cause of heat ; decomposition of
the tissues, therefore, must develop heat at the same time with me-
chanical effect. Indeed, violent muscular exercise is often resorted to
in winter as a source of bodily warmth, by increasing the respirations
and muscular waste. In this subordinate way, the nitrogenous ah-
ments become h^at-producers. It is not to be supposed that oxygen
seizes upon all the atoms of tissue indiscriminately, or upon those
which it finds next before it. There is a wonderful selective power,
some particles are taken and others left. Those only are seized upon
which in some unknown way, perhaps under the regulating influence
of the nervous system, are made ready for change.

680. Relation between Waste and Supply. — If an organ or part be the

PEODUCmON OP BODILY STEENGTH. 363

seat of destructive and reparative changes, and its weight remains in-
variable, we know that an exact balance is struck between these two
kinds of transformation. But the processes of destruction and reno-
vation in the body are not necessarily equal, so that every atom that
perishes out of the structure is promptly replaced by another. In
those cases where the system neither gains nor loses weight, the an-
tagonist forces must of course pi'ecisely compensate each other. Yet,
even here, the general equilibrium is the result of constant oscillations.
The involuntary muscles, which play continually, as those of the heart,
and the muscles engaged in respiration, have an intermitting action.
The short or momentary period of activity is followed by a corre-
sponding interval of rest. If the first condition involves destruction,
the second allows of nutrition. That portion of the mechanism which
is independent of voluntary control, is thus self-sustaining. StUl, in
the case of these parts, the equipoise between waste and supply may be
lost, as in bodily growth when nutrition exceeds decomposition, or in
deficiency of nutriment, when destruction proceeds at the expense of
the tissue, which loses weight faster than the food renews it. As re-
gards the waste and renovation attending voluntary movement, there
is the same periodicity. Destruction gains upon nutrition during the
exercise of the day, and what was lost is regained by nutrition during
rest at night. In sleep, nutrition is at its height while waste falls to its
minimum. As bodily exertion costs tissue destruction, which can only
be made good again by albuminous substances, it follows that these will
be demanded for food, in proportion to the amount of efibrt expended.
If such food be not adequately supplied, or if from any cause the body
be incapable of digesting or assimilating it, the apparatus of force begins
at once to give way, the acting tissues shrink and fail, for human efibrt is
carnivorous, flesh-consuming. If, on the other hand, the system is main-
tained at rest, that is, if force is not exerted, the nutriment is not used
or expended, but is laid up in the body, and serves to increase the mass.
681. Hastening and retarding tissne changes.— Ingested substances have
a twofold relation to waste or metamorphosis of the tissues. Some,
as we have seen, become portions of the animal solids, and then un-
dergo transformation. Others have the power of modifying or con-
trolling these changes, without in the same way participating in them.
Some of these increase metamorphosis, and others chech it. Common
salt, for example, and an excess of water, act as Jiasteiwrs of tissue
change, while alcohol and tea act as arresters of metamorphosis. If
we consume those substances which augment the waste, it is said we
require a fuller diet to compensate for the extra loss, or the body de-

364 PHTSIOLOGICAIi EETECTS OF FOOD.

clines in weight with more rapidity than otherwise. If we employ the
arresters of metamorphosis, we are supposed to have tissue, and can
maintain our usual strength and weight on a more slender diet. That
certain substances produce these eflfects, may he regarded as establish-
ed, but it cannot be admitted that they are proper aliments. "We re-
cognize transformation of the living parts, as the highest and final
physiological fact, the necessary condition of human activity. Dr.
Ohambees remarks — " Metamorphosis is life^ or an inseparable part
of life." Undoubtedly the rates of bodily change are liable to certain
variations, within limits of health ; but the whole import of the vital
economy, leads us to connect accelerated and retarded changes with
variations in the exercise of force, by a fixed organic ordinance. "With
high activity, a rapid change, and with rest, a minimum of loss is evi-
dently nature's purpose, and her law. Substances introduced into the
system, which act upon the tissues, as it were from without, and in-
terfere with this fundamental relation between rate of exertion and
rate of change, can be regarded in no other light than as disturbers of
physiological harmony, StUl, we are to be cautious about theoretically
prejudging any substance ; whether it be beneficial or injm-ious is as-
certainable only by careful observation and experience of its effects.

8. Mind, Body, and Aliment.

682. Mind brongM into relation with Matter. — In his ultimate destiny,
we contemplate man as an immortal spirit, but in the Divine arrange-
ment, that .spirit is to be educated and prepared in nature and time for
its onward career. Spirit or mind partakes in nothing of the attri-
butes of matter, but it coiresponds closely to our conception of force.
The passions are regarded as the mind's motors^ or motive powers.
The directive or governing element we call will^ or wUl-power. We
speak constantly of intellectual force, and mental energy, and regard
the mind as an assemblage of faculties or powers capable of producing
effects. Indeed, as we consider the Mind or WUl of God to be the all-
controlling activity of the universe, so the mind of man, created in his
Maker's image, is perpetually demonstrating an over-mastering con-
trol of the elements and agencies of nature. As mind is thus designed
to be developed by action, with the material world for its theatre, it
must of course be brought into relation with matter. The brain is the
consecrated part where this inscrutable union is eftected, and the ner-
vous system is the immediate mechanism which establishes a dynamic
connection between the spiritual intelligence and the physical creation.

683. Mental Exercise destroys Nervons Matter. — Of the natui-e of this

MIND, BODY, AND ALIMENT. 365

union, how it is accomplished, we know nothing, bnt some of its con-
ditions are understood. We are certain that the brain and nerves
wear and waste by exercise, and require renewal, just like all the
other tissues. Nervous matter in this respect is no exception to the
general law of the organism. The external universe pours in its im-
pulses through aU the avenues of sense, along the nerve routes to the cen-
tral seat of consciousness, the brain ; whUe the mind, exerting itself
through that organ, and another system of nerves, calls the muscles into
action, and produces its thousand-fold effects upon external objects. In
both cases there is decomposition and loss of nerve-substance, and
there must, therefore, be a nutrition of brain and nerves, as truly as
of any other part ; nay, more truly, for destruction and renovation
are perhaps more active in these parts than in any others. Arterial
blood, with its agent of disorganization (oxygen), and its materials of
repair, are sent to the brain in a far more copious flood than to any
other equal portion of the body. Blood-vessels are also distributed
most abundantly around the nerves, so as to effect their nutrition in a
perfect manner ; while if the vital stream be checked or ai'rested, the
nerve loses its power of conducting impressions, and the brain its
capacity of being acted upon by the mind ; the interruption of the
blood-stream through this organ producing instantaneous unconscious-
ness. Besides, the nerve-tissue consists of the most changeable mate-
rials, "TO to 80 per cent, water, 10 of albumen, and 5 to 8 of a peculiar
oily or fatty substance, with various salts. It is interesting to re-
mark, that in starvation the parts are disorganized and consumed in
the inverse order of their physiological values. First, that which is
of lowest service, and can be best spared ; the fatty deposits are
wasted away, then the muscular and cellular tissues, and lastly the
nervous system, which remains undisturbed and intact until the dis-
organization of other parts is far advanced. The mind's throne is the
last part invaded, and the last to be overturned. We are struck with
the wisdom of this arrangement, but we cannot explain it.

684. Can we measure Brain and Nerve waste ? — The appropriation of
certain specific parts to certain purposes, is the basal fact of physiolo-
gy. A part may indeed perform several oflSces, but they are determi-
nate and limited, and the different portions cannot change duties ; the
stomach cannot respire, nor the lungs digest, the mind cannot act di-
rectly upon the muscular system (only through the intermedium of
the nerves), nor can the nerves exert mechanical force. Each part,
therefore, does its appropriate work ; and as it has a special composi-
tion, its metamorphosis gives rise to peculiar products. Muscular de-

366 PHYSIOLOGICAL EFFECTS OF FOOD.

composition must hence yield one set of substances, and nerve-waste
another. It has been attempted to identify these products, and thus
get indications of the amount of change in each part, as a measure of
the degree of its exercise. But the results yet obtained are probably
only approaches to the truth. Thus, urea is undoubtedly a result of
muscular change, and some have regarded its amount in the renal ex-
cretion as an index to the degree of muscular exercise. But others
aflBrm that it may also come from unassimUated food, as well as active
muscle, which casts a doubt over conclusions thus formed. In the
same way, salts of phosphoric acid have been regarded as the peculiar
products of brain and nerve waste, and their amount in the kidney
evacuations, as a measure of the exercise of brain and nerves. From
the researches of Dr. Bense Jones, it appeared that where there is a
periodical demand upon the mental powers (as among clergymen, for
example, in preparation for their Sunday exercises), there is a corre-
sponding rise in the quantity of alkaline phosphates voided by the renal
organs. Yet here, too, there is uncertainty, for we are not sure that
these phosphatic salts may not have other sources also.

685. The Mind's action wears and cxhansts the Body. — That all forms of
mental exertion have a wearing, exhausting eflEect upon the body,
producing hunger, and a requirement for food, is well known. Pure
intellectual labor, vigorous exercise of the will, active imagination,
sustained attention, protracted thought, close reasoning, ' the nobler
enthusiasms, the afflatus of the poet, the ambition of the patriot, the
abstraction of the scholar,' — the passions and impulses, hope, joy,
anger, love, suspended expectance, sorrow, anxiety, and ' corroding
cares,' all tend to produce physical exhaustion, either by increasing
the destruction of the tissues, or preventing the assimilation of nutri-
ment. It is true that the stunning effect of an emotion, a surge of
joy, or a blast of anger, or profound grief, may temporarily overpower
the sensation of hunger, that is, prevent its being felt, but after a time
the appetite returns with augmented force. In sleep, the mechanism
of sense, consciousness, volition, and passion, is at rest, and unhindered
nutrition makes up for the losses of the waking hours. If the brain
be overworked, either by long and harassing anxiety, or by severe
and continued study, it may give way ; that is, its nutrition takes place
so imperfectly as to produce morbid and unsound tissue, which can
only be restored to the healthy state by long mental tranquillity and
cessation of effort.

686. The Phosphatic constituents of Brain. — We have spoken of the
phosphates as special products of brain and nerve waste. That phos-

MESTD, BQDT, AND ALIMENT. 367

pliorus, in some state, or combination, is a leading ingredient of nervous
and cerebral matter, is unquestionable ; and that it stands related in
some way to tbe fundamental exercise of those parts, will hardly be
doubted. "We remember that it is a very remarkable element,
shining in the dark (from which it takes its name), and having a most
powerful attraction for oxygen, combining with a large amount of it,
and generating phosphoric acid with intense heat und Hght. It is
also capable of existing la two states ; its ordinary active condition
and a passive or inert state, in which it seems paralyzed or asleep, and
exhibits no aflBnity for oxygen. The solar rays have the power of
throwing it from the active to the passive form. It has been main-
tained that in the leaf and by the sun, elementary phosphorus is sepa-
rated from its compoimds, put in the passive state, rocked to sleep (297),
is stored up in foods, and thus finds its way into the body, its blood and
nervous matter, — and that finally, in the exercise of mental and ner-
vous power, it resumes the active condition, and undergoes oxidation,
producing phosphoric acid. In L'Heeitiee's analysis of nervous mat-
ter (quoted by standard physiological authorities); it is stated that the
proportion of phosphorus in infants is 0'80 parts per 1,000, in youths'
1"65 (more than double), in adults 1'80, in aged persons 1"00, and in
idiots 0'85, thus apparently connecting the quantity of this substance
in the brain with maturity and vigor of mental exercise. From this
point of view Dr. Moleshott leaps at once to the conclusion, ' no
phosphorus, no thought ;' Liebig, however, denies point-blauc that
elementary phosphorus has ever been found in nervotis matter. He
says, " no evidence is known to science tending to prove that the food
of man contains phosphorus, as such, in a form analogous to that in
which sulphur occurs in it. No one has ever yet detected phosphorus
in any part of the body, of the brain, or of the food, in any other
form than that of phosphoric acid." As phosphorus and phosphoric
acid, in their properties, are as wide asunder as the poles of the earth,
it is highly incorrect to use the terms interchangeably, or (according to
the statement of Liebig) to apply the term phosphorus in this con-
nection. It may be remarked that the phosphoric compound is a con-
stituent of the oily matters of nerve tissue, which are hence called
' phosphorized fats.'

687. Are there special Brain NatrimeatSt — On the strength of this
phosphoric hypothesis, crude suggestions have been volunteered for
students and thinkers, to take food abounding in phosphorus, as fish,
eggs, mUk, oysters, &c. Such advice has no justification in weU de-
termined fact^ "We are not authorized by science to prescribe a diet

368 PHYSIOLOGICAL EFFECrrS OF FOOI>.

specially or peculiarly constructed to promote brain nutrition and pro-
tract mental exercise. But while it would seem as if care had been
taken to secure these high results in the universal constitution of food,
stUl it is certainly in accordance with analogy, that specific aliments
should be adapted, or at all events iest adapted, to produce certain
kinds of effect in the system. Special means for special ends make up
the unitary scheme of the living economy. The waste produced by
mental exertion is repaired only by food, but to say by all food alike
transcends the warrant of science. Professor Liebig remarks, " It is
certain that three men, one of whom has had a full meal of beef and
bread, the second cheese or salt fish, and the third potatoes, regard a
difficulty which presents itself from entirely different points of view.
The effect of the different articles of food on the brain and nervous
system is different, according to certain constituents peculiar to each
of these forms of food. A bear kept in the anatomical department of
this university, exhibited a very gentle character as long as he was fed
exclusively on bread. A few days' feeding with flesh rendered him
savage, prone to bite, and even dangerous to his keeper. The carni-
vora are, in general, stronger, bolder, and more pugnacious than the
herbivorous animals on which they prey ; in like manner those nations
which live on vegetable food differ in disposition from those which
live chiefly on flesh. The unequal effects of different kinds of food,
with regard to the bodily and mental functions of man, and the de-
pendence of these on physiological causes, are indisputable ; but as yet
the attempt has hardly been made to explain these differences accord-
ing to the rules of scientific research."

688. Diet of Braia-workers. — Yet the diet of the literary, of artists,
and those who devote themselves to intellectual labor, is by no means
unimportant, and should be carefully conformed to their peculiar cir-
cumstances. They should avoid the mistake of supposing that, as they
do not work physically, it is no matter how slight their diet, and the
perhaps stUl more frequent error, on the other hand, of excessive eat-
ing, the fruitful cause of dyspepsia, and numerous ailments of the sed-
entary. The best condition of mind corresponds with the most
healthy and vigorous state of body. The blood prepared by the di-
gestive and pulmonary organs, and taking as it were its quality and
temper from the general state of the system, nourishes the brain and
influences the mind. That diet and regimen are therefore best for
thinkers, which maintain the body in the most perfect order. They
should select nutritious and easily digestible food, avoiding the more
refractory aliments, leguminous seeds, heavy bread, rich pastry, &c.

INFLUENCE OF SPECIAL SUBSTANCES. 369

689. Men seek for Brain Excitants. — Althongli specific brain nutri-
ents and though t-sustainers are not determined among foods, yet sub-
stances exerting a powerful influence through the brain upon the mind,
are but too well known. By a kind of ubiquitous instinct, men have
ransacked nature in quest of agents which are capable of influencing
their mental and emotive states, and they have found them every
where. It is estimated that the peculiar narcotic resin of Indian
hemp (haschish), is chewed and smoked among from two to three hun-
dred millions of men. The ietel nut is employed in the same way
among a hundred millions of people ; the use of opium prevails among
four hundred millions, and of tobacco among eight hundred million
of the world's inhabitants. These substances act poAverftJly, although
somewhat diflferently, upon the nervous system, and thus directly affect
the state of the mind and feelings. "We here touch upon the myste-
rious world problem of narcotism; but its discussion, though of absorb-
ing interest, would* be too extensive for our limits, besides being for-
eign to the present inquiry, which is restricted to the general subject
of foods. The effects of tea and coffee will be noticed when speaking
of drinks (704).

9. iNTLtJEKOE OF SPECIAL StJBSTANOES.
A.— Saline Matters.

690. Tlie Asli elements of Food essential to Life. — When vegetable sub-
stances are burned, there remains a small portion of incombustible
mineral matter. It was formerly thought that this consisted merely
of contaminations from the soil, which happened to be dissolved by
water that entered the roots, and was therefore present in the vegeta-
ble by accident. We now understand that such is far from being the
fact. The ash-principles of food are indispensable to animal life. In-
deed, without them neither group of the alimentary substances which
we have been considering could do its work. It has been found, in
numerous experiments, made upon the lower animals, that neither
gluten, casein, albumen, sugar, oil, nor even a mixture of these, when
deprived as far as possible of their mineral ingredients, are capable of
sustaining life ; the animal thus fed actually perishes of starvation.

691. Acids, Alkalies, Salts. — We remember that acids are bodies hav-
ing the power of turning blue test paper red, and that alJcalies change
the red to blue. They also combine together, each losing its peculiar
properties, and produce salts. If the properties of the acid and alkali
both disappear, the salt produced is neutral^ that is, neither acid nor

16*

370 PHYSIOLOGICAL EFFECTS OF FOOD.

alkaline. If the acid be stronger, or there be a donble or treble dose
of it combining with the alkali, the compound is still acid, an acid
salt; or if the alkali be strongest or in excess, it overpowers the acid
and an alhaline salt results. If a neutral salt be dissolved in water,
the liquid will be neither acid nor alkaline. If an acid salt be dis-
solved, the water will be acidulous, and produce all the effects of
acidity ; if an alkaline salt, the liquid will be alkaline, producing alka-
line effects. The ash of foods consists of potash, soda, lime, magnesia,
oxide of iron, sulphuric, carbonic and phosphoric acids, silica and com-
mon salt. Fruits abound in acid salts, that is, powerful organic acids,
as oxalic, tartaric, and malic acids, with potash and lime ; the acids be-
ing in excess. When fruits are burned, the organic acids are consumed
or converted into carbonic acid, and the salts become carbonates — neu-
tral carbonates of lime or alkaline carbonates of potash. The quanti-
ties of salts, alkalies, and alkaline earths contained ia many kitchen
vegetables are surprising. Celery (dried), contains from 16 to 20 per
cent., common salad 23 to 24 per cent., and cabbage heads 10 per cent.

692. Tlie Ashes of the Food are Assimiiated, — When the organic mat-
ter of food is burned away in the system, a residue of ashes is left,
just as in open combustion in the air. But they are not cast at once
from the body as useless, foreign, or waste matters. They have im-
portant duties to perform as mineral substances, after being set free
from organized compounds ; and they hence remain dissolved in the
blood and various juices of the system. Portions of these mineral
matters are constantly withdrawn from the circulation, some at one
point and some at others, to contribute to special local nutrition.
Thus phosphate of lime is selected to promote the growth of bones,
while the muscles withdraw the phosphates of magnesia and potash ;
the cartilages appropriate soda in preference to potash ; silica is se-
lected by the hair, skin, and nails ; while iron is attracted to the red
coloring matter of tha blood, and the black coloring matter within
the eye.

693. The Blood Alkaline, and why ? — But there remains constantly
dissolved in the blood and animal juices, a proportion of acids, al-
kalies, and salts, which impart to these liquids either acid or alkaline
properties. The result, however, is not left to accident. Whether
a liquid be acid or alkaline is of essential importance in refer-
ence to the offices it has to perform. We have seen that it is
the determining fact of the digestive juices ; one is always acid, and
the other alkaline, and their peculiar powers depend upon these
properties. So with the blood. It contains potash, soda, lime, mag-

INFLUENCE OF SPECIAL SUBSTANCIS. 371

nesia, oxide of iron, phosphoric acid, and common salt ; yet these are
so proportioned that soda is in excess, and hence the blood of all animals
is invariably alkaline. An alkaline condition is indispensable to the
action of this fluid. Liebig remarks, " The free alkali gives to the
blood a number of very remarkable properties. By its means the
chief constituents of the blood are kept in their fluid state, the ex-
treme facUity with which the blood moves through the minutest ves-
sels, is due to the small degree of permeability of the walls of these
vessels for the alkaline fluid. The free alkali acts as a resistance to many
causes, which, in the absence of the alkali, would coagulate the albu-
men. The more alkali the blood contains, the higher is the tempera-
ture at which its albumen coagulates ; and with a certain amount of
alkali, the blood is no longer coagulated by heat at aU. On the al-
kali depends a remarkable property of the blood, that of dissolving
the oxides of iron, which are ingredients of its coloring matter, as
weU as other metallic oxides so as to form perfectly transparent solu-
tions." Alkali in the blood also promotes the oxidation of its consti-
tuents. A number of organic compounds acquire by contact with, or
in presence of, a free alkali, the power of combining with oxygen
(burning), which alone they do not at aU possess at the ordinary
temperature of the air, or at that of the body. — (Cheveettl.) The
alkalies of the blood exert a precisely similar action, increasing the
combustibility of the respiratory foods,

694, Flesh and its Jaices, Acid.— But while alkali is necessary to
maintain the perfect fluidity and combustive relations of the blood,
the alkaline state seems unfavorable to nutrition. In the ash of
muscles, there is an excess of phosphoric acid, and the juice of flesh
which surrounds the muscles is also acidulous. The blood nourishes
the flesh-juice, and that the muscles, but an acid medium is indis-
pensable to the latter change. Taking the whole body together, acids
predominate, so that if the blood were mingled with the other juice,
the whole would have an acid character. The chief flesh acids are
phosphoric and lactic, but how they influence nutrition is not under-
stood. The remarkable fact of the existence in all parts of the body
of an alkahne liquid, the blood, and an acid liquid, the juice of flesh,
separated by very thin membranes, and in contact with muscles and
nerves, seems to have some relation to the fact now established, of the
existence of electric currents in the body.

695. Uses of Salt in the System. — The properties of commercial or
common salt, have been noticed when speaking of its preservative
powers (590). We may now con^der its action in the system. It is

372 PHYSIOLOGICAL EFFECTS OF POOD.

a large and constant ingredient of the blood, forming neariy sixty pei
cent, of its ash. It exists also in other fluids of the body, hut is not,
perhaps, a constituent of the solid tissues, except the cartilages. Its
offices in the system are of the first importance. It increases the so-
lubility of albuminous matters. Dissolved in the liquids of the ali-
mentary canal, it carries with it their important principles, preserves
them fluid through the chyle and blood, then parting from them aa
they become fixed in the tissues, returns to perform the same round
again. By decomposition in presence of water, common salt yields
an acid and an alkali, hydrochloric acid and soda. This separation is
is effected in the system, indeed there is no other source for the hy-
drochloric acid of stomach digestion. The considerable quantity of
soda in the bile and pancreatic juice, which serve for intestinal diges-
tion, as weU. as the soda of the alkaline blood, are chiefiy derived from
common salt. A portion comes directly from the food, but by no
means sufficient for the wants of the body. Yet it is highly probable,
that in the econony of the system, the same materials are used over
and over, the acid of the stomach, as it fiows into the intestine, com-
bining with the soda it finds there, and reproducing common salt,
which is absorbed into the blood, decomposed, and yielded again to
the digestive organs. We recollect that common salt consists of
chlorine and sodium ; it is a chloride of sodium. Chloride oi potassium
is another salt of apparently quite similar properties. Tet in their
physiological effects, they are so different, that while chloride of
sodium exists largely in the blood, it is not present in muscles or juice
of flesh, chloride of potassium being found there. They seem to have
distinct and different offices, and are not replaceable. But the chlo-
rine of the chloride of potassium comes from common salt. It may
be remarked, that as phosphate of soda exists in the blood, phosphate
of potash belongs to flesh-juice and muscles.

696. Commott Salt contained in Food. — Salt escapes from the system
by the kidneys, intestines, mucus, perspiration, and tears. To re-
place this constant loss, and maintain the required quantity in the
body, there must be a proper supply. It is universally diffused in
nature, so that we obtain it both in the solid food we consume and in
the water we drink, though not always in quantity sufficient for the
demands of the system. Yet the proportion we obtain in food is
variable, animal diet containing more than vegetable ; though the
parts which most abound in this ingredient, — the blood and cai-ti-
lages — are not commonly used for food. Of vegetable foods, seeds
contain the least amount of common salt, roots vary in their quantity,

mrLUBNCE OF SPECIAI. BTTBSTANCES. 373

turnips having hardly a trace. Yet mucli depends upon its abundance
in the soil, and even in the atmosphere ; the air near the sea being
saline from salt vapor. Plants near the sea are richer in soda than
those grown inland, the latter abounding in potash. When we reflect
upon the importance of the duties of salt in the organism, and that its
necessary proportion in the blood is so much larger than in the food, —
often tenfold greater — and besides, that its quantity is extremely vari-
able in our aliments, its almost universal use as a condiment, will not
surprise us. The craving for it is very general — probably instinctive
— but where it does not exist, we conclude, either that sufficient is
furnished naturally in the food and drink, or that animals suffer for
the want of it. The quantity annually consumed by each individual
in France, has been estimated at 19| lbs ; in England at 22 lbs.

697. Effects of too little and too much Salt. — From what has been
said, we see that a due supply of salt is of the first necessity ; its de-
ficiency in diet can only prove injurious. The most distressing symp-
toms, ending in death, are stated as the consequence of the protracted
use of saltless food. The ancient laws of Holland " ordained men to
be kept on bread alone, unmixed with salt, as the severest punish-
ment that could be inflicted upon them in their moist climate ; the
effect was horrible ; — these wretched criminals are said to have been
devoured by worms engendered in their own stomachs." Taken into
the system in large quantity (a table spoonful), it excites vomiting ;
when thrown into the large intestines, it purges. A too free use of
salt engenders thirst ; in moderate quantities, it increases the appetite
and aids digestion. A long course of diet on provisions exclusively
salt-preserved, produces the disease called scurvy. This condition of
body is believed by some to be due to a deficiency of potash com
pounds in the system, as in the act of salting, various valuable all
ments are abstracted (593). Potatoes, and vegetables rich in potash
are excellent antiscorbutics — correctives of scurvy. Fresh flesh yieldr
potash to the system unequally ; for in that of the ox, there is three
times, in that of the fowl, four times, and in that of the pike, five times
as much potash as soda. Experiments relating to the influence of com-
mon salt upon animals, have given somewhat discordant results. In
some cases, it improved their appearance and condition decidedly ;
whUe in others, no such result followed. Yet the amount supphed
naturally in the food, in the several instances, was not determined.
Salt is supposed to be in some way closely allied to the nutritive
changes, and some think it increases the metamorphosis of the
body ; so that a free use of it would only be consistent with a liberal
diet.

874 PHYSIOLOGICAL BFFECTS OF FOOD.

698. Carbonates of Soda and Potash. — The exclusive employment of
these substances in extemporising light bread (509), makes a reference
to their physiological action necessary. Carbonate of potash in its
crude shape, appears a'spearlasTi; in its more purified form it is saleratus.
Crude soda is known as sal-soda or soda-saleratus ; refined and cleared
of its chief impurities, it forms carbonate and bicarbonate of soda.
All these compounds have the common alkahne or burning property,
which belongs to free potash and soda ; tut it is lowered or weakened
by the carbonic acid united with them. The potash compounds are
the strongest, those of soda being of the same nature but weaker. Yet
the system, as we have just seen, recognizes essential differences be-
tween them ; one pertains to the blood and the other to the flesh.
According to the theory of their general use for raising bread, they
ought to be neutralized by an acid, muriatic, tartaric, acetic, or lactic,
thus losing their peculiar properties and becoming salts. These
changes do take place to a certain extent, and the saline compounds
formed, are much less powerful and noxious than the unneutralized
alkalies ; their effects are moderately laxative. Yet, in the common
use of these substances, as we have stated, the alkali is not aU ex-
tinguished ; much of it enters the system in its active form. Pure,
strong potash, is a powerful corrosive poison ; disorganizing the
stomach, and dissolving its way through its coats, quicker, perhaps,
than any other poisonous agent. When the alkalies are taken in small
quantities, as where there is an excess in bread, they disturb healthy
digestion in the stomach, by neutralizing its necessary acids (643).
They are sometimes found agreeable as palliatives, where there is
undue acidity of the stomach ; and, on the other hand, they may be
of service in the digestion and absorption of fatty substances. It is
alleged that their continued use tends to reduce the proportion of the
fibrin in the blood. Cases are stated, where families have been poisoned
by the excessive employment of saleratus.

B.— Liiqnid Aliments*

699. Physiological importance of Water. — "Water is the most abundant
compound in the body, constituting 80 per cent, of the blood, and 75
per cent, of the whole system, — in importance to life it ranks next
to oxygen of respiration. An adult umn takes into his system three-
quarters of a ton of it in a year. It supplies some of the first condi-
tions of nutrition, and is, therefore, entitled to head the list of aliments
(366). It is the simple and universal bevei-age furnished by nature, for
all living beings, and exists in greater or less proportion, as we have

ESTPLTJENCB OF SPBCIAl SUBSTANCBS. 375

seen, in all solid food. Vegetables and meats are, at least, three-
fourths water ; while bread is about 45 per cent, or nearly one half.
Athough there is a little water even in the dryest food, yet the demand
for it is so great, and its consumption so rapid, that our mixed ali-
ments do not furnish sufficient, whUe the most nutritious, are the most
provocative of thirst. Hence, we daily drink large quantities of it in
the free or liquid condition.

700. Its twofold state in the body. — Water exists in the body, in the
fluctuating, circulating, liquid condition ; and also fixed as a solid in th«
tissues. In the liquid state, it subserves the same great purpose :^
in the world of commerce, it is an agent of transportation. Its par-
ticles glide so freely among each other, as easily to be put in motion,
which makes it a perfect medium of circulation, and transportation of
atoms. It is the largest constituent of the fleshy parts, serving to
give them fulness, softness, and pliancy. Water is a vital and essen-
tial portion of the animal structure, but hardly an organized constitu-
ent. It is intimately absorbed and held in a peculiar mechanical
combination, which permits of separation by pressure. " The milk-
white color of cartilage, the transparency of the cornea, the flexibility
and elasticity of muscular fibre, and the silky lustre of tendons, aU
depend on a fixed proportion of water in each case."

701. Water generated in the Animal System. — Water in large quantities
is as necessary to plants as to animals ; but it serves an important pur-
pose in the vegetable world, which it does not, or but to a small de-
gree, in the animal kingdom. Plants decompose it, and use its ele-
ments to form their peculiar compounds. The animal possesses this
power in but a limited way, if at aU ; on the contrary, it is one of its
leading offices to combine the elements which the plant separated,
and thus produce water. Hydrogen and oxygen combine continually
in the combustion of food, so that in reality, a considerably larger
quantity of water is excreted from the system, than was introduced
into it in that form.

702. Influence of Water upon Digestion, — We have referred to the
remarkable solvent powers of water (367). If we could look into the
living organism, we should see that its whole scheme is but an illus-
tration of it. Blood, juice of flesh, bUe, gastric and pancreatic fluid,
saliva, mucus, tears, perspiration, and aU other peculiar liquids of the
body, are simply water, containing various substances in solution. In-
deed, the flnal result of the whole digestive process is to liquefy the
aliments, or dissolve them in water. The effect of taking Liquids is of
course to dilute the bodily fluids, just in proportion to the amount

376 PHYSIOLOGICAI. EFFECTS OF FOOD.

taken. The first effect "will be a dilation of the gastric juice of the
stomach, but the water is rapidly absorbed into the blood, which is
thus made thinner. It has been taught that the effect of swallowing
much liquid during meals is to lower the digestive power by diluting
and weakening the gastric juice. This is, however, denied by high
authority. We know that excessive eating is usually accompanied by
a copious nse of liquids, so that it is easy to commit the mistake of
charging the evils of over-eating to the account of over-drinking. In
such cases abstinence from drinks may be commended as a means
of enfoscing moderate eating. Dr. Chambees, of ix>ndon, asserts
that, " A moderate meal is certainly easier digested when diluents
are taken with it." Again he remarks, " Aqueous fluids in large quan-
tities during meals, burden the stomach with an extra bulk of matter,
and, therefore, often cause pain and discomfort, but that they retard
digestion I do not believe. Indeed, among the sufferers from gastric
derangements of all kinds, cases frequently occur of those who cannot
digest at aU without a much more fluid diet than is usual among heal-
thy persons."

703. Water iMoenees change of Tissue. — Beyond digestion is meta-
morphosis of structure, and this is influenced by the amount of water
drank. Eecent careful experiments by Dr. Bockee, performed upon
himself, show that the use of any quantity of water above the actual
demand of thirst, and the essential wants of the system. Increase the
transformations of the solid parts of the body. He first ascertained
what quantity of food and drink was just suflicient to satisfy his appe-
tite and cover the losses of the system. He then found that by con-
tinuing the same quantity of food, and increasing the proportion ot
water, the weight of the body constantly dimiuished. The excess
of water increased the waste, so that the same food would no longei
restore it — the balance inclined on the destructive side. Neither tht
pulse nor respiration were affected, but there was more languor aftei
exercise, while the sensation of hunger kept pace with the increased
metamorphosis of matter.

Y04. Tea and Coffee. — These are taken in the form of infusions, the
composition and preparation of which have been described (551).
They are allied to foods by whatever nutritive constituents they hap-
pen to have, which are inconsiderable, and they are distinctly separa-
ted from them by possessing certain additional qualities which do not
pertain to nutriment. The ingredients to which tea and coffee owe
their peculiar action are thein and cafein, tannic acid and volatile or
empyreumatic oU.

rsnBXtTBNCE OF SPECIAL SUBSTANCES. 311

705. Effects of Tea, — Thotigh tea is so universally employed in diet,

yet its effects upon the constitution are by no means precisely ascer-
tained. Its tannic acid gives an astringent taste, and a constipating in-
fluence in the intestines. It also acts as a diuretic. Thein and vola-
tile oil of tea are its most active ingredients, producing, perhaps
jointly, its characteristic effects upon the nervous system. It is
acknowledged that tea is a brain excitant, that it influences the mind,
and produces exhilaration and wakefulness. How it effects the men-
tal faculties, observers have been unable to decide, judging by their
discrepant statements. If the quantity of thein contained in an oimce
of good tea (8 or 10 grains), be taken, unpleasant effects come on, the
pulse becomes more frequent, the heart beats stronger, and there is
trembling of the body. At the same time the imagination is excited,
the thoughts wander, visions begin to be seen, and a peculiar state of
intoxication supervenes; all these symptoms are followed by, and pass
off in, a deep sleep. Dr. Booker has made several careful sets of ex-
periments upon his own person to determine the physiological effects
of tea. He took exact account of the quantity of aliment ingested, of
the substances excreted, of his own weight, and the general bodily
sensations. His investigations lead to the conclusion, Jirst, that tea in.
ordiuary doses has no effect on the amount of carbonic acid expired,
the frequency of the respirations, or of the pulse ; second, when the
diet is insufficient, tea limits the loss of weight thereby entailed ;
third, when the diet is sufficient, the body is more likely to gain weight
when tea is taken than when not ; fourth, tea diminishes the loss of
substance in the shape of urea, lessens the solid excretions, and limits
the loss by perspiration. It is thus claimed that this beverage is an
enlivener of the mind, a soother of the body, and a lessener of the
waste of the system.

706. Influence of Coffee in Digestion. — The active ingredients of cof-
fee are cafein, which is identical in properties with thein of tea, and
the peculiar empyreumatic or burnt oil produced in roasting. "By
the presence of empyreumatic substances, roasted coffee acquires the
property of checking those processes of solution and decomposition
which are begun and kept up by ferments. "We know that all em-
pyreumatic bodies oppose fermentation and putrefaction, and that, for
example, smoked flesh is less digestible than that which is merely
salted. Persons of weak or sensitive organs will perceive, if they at-
tend to it, that a cup of strong coffee after dinner, instantly checks
digestion ; it is only when the absorption and removal of it has been
effected, that relief is felt. For strong digestions, which are not suf-

378 PHYSIOLOGICAL EFFECTS OP POOD.

ficiently delicate reagents to detect such effects, coffee after eating
serves from the same cause to moderate the activity of the stomach,
exalted beyond a certain limit by wine and spices. Tea has not the
same power of checking digestion ; on the contrary, it increases the
peristaltic motions of the intestines, and this is sometimes shown in
producing nausea, especially when strong tea is taken by a fasting
person" — (Liebig.)

Y07. Lehman oa the inflnenee of Coffee. — "We are indebted also to Pro-
fessor Lehman for valuable experiments to ascertain the effects of cof-
fee. He states that coffee produces two leading effects upon the gen-
eral system, which it seems difficult to associate together, viz : height-
ening vascular and nervous activity, and at the same time protracting
the decomposition of the tissues. The cafein and oil both contribute
to the same peculiar stimulant effects, by which it rouses the exhaust-
ed system and promotes feelings of comfort and cheerfulness. He
finds that in retarding the decompositions of the body, it is the em-
pyreumatic oil of the beverage that chiefly acts, the cafein only pro-
ducing this result when taken in larger than usual proportion. Excess
of this oO. causes " perspiration, diuresis, quickened motion of the
bowels, and augmented activity of understanding, which may indeed,
by an increase of doses end in irregular trains of thought, congestions,
restlessness, and incapacity for sleep ; and that excess of cafein pro-
duces increased action of the heart, rigors, derangement of the renal
organs, headache, a peculiar inebriation, and delirium."

708. Chocolate is allied to tea and coffee by its nitrogenous princi-
ple (theobromin), but the effect of this substance seems to be less
marked than in the other cases, and has not been clearly traced. It
is more nutritive than those drinks from its larger proportion of albu-
men and fat, but the excess of the latter substance makes it indigesti-
ble and offensive to delicate stomachs.

709. Alcoholic Liquors. — The common and active principle of spirit-
ous liquors is alcohol, obtained from sugar by fermentation. It varies
in proportion in the different sorts from 1 to 50 or 60 per cent.
Liquors contain various accompanying substances, traces of albumen,
sugar, acids, volatile oils, ethers, bitter principles produced in the pro-
cess of fermentation or distillation, or purposely added to suit the de-
mands of taste. The scale of commercial valuation of alcoholic liquors
is made to depend, not on the peculiar spirituous principle, which is
cheap, but on the attending flavoring ingredients, and various sub-

' stances which are said to modify the effect of alcohol upon the sys-
tem. Yet it is the alcoholic principle found in all these mixtures that

INFLITENCE OF SPECIAL SUBSTANCES, 379

gives them life, and a common character, and groups them all together
under the common title of intoxicating liquors. It has been insisted
by some that alcoholic beverages are entitled to rank as food or nutri-
ment, but the claim is inadmissible, and moreover, is not urged by the
most discriminating physiologists, even those who look with favor
upon its general use.

710. They cannot replace Water in the System. — Water is the ap-
pointed solvent within the living body. Aided by acids, alkahes, salts,
it brings the various solids into the required condition of solution.
But alcohol cannot replace water in this duty. Its solvent powers are
not the same as those of water. "What alcohol dissolves, water may
not, and the reverse. Alcohol mised with water may deprive it of
its solvent powers in particular cases. This is precisely what is done
when alcoholic liquids are taken into the stomach. They coagulate,
and precipitate the pepsin dissolved in the watery gastric juice, and tf
not quickly absorbed by the stomach into the blood, they would in this
way effectually stop digestion. Their action while within the stomach
is to disturb and arrest the digestive process.

711. They cannot nourish Tissue. — Alcohol contains no nitrogen; it
cannot, therefore, be transformed into tissue, nor take part in meta-
morphic changes. Its composition forbids the possibility of any such
effect, and nobody acquainted with the rudiments of physiology
claims it.

712. Their relation to Animal Heat. — The assumption that alcohol
is a respiratory aliment is plausible at the first blush, but conceding the
utmost demand — that it undergoes combustion in the body — it is en-
tirely impossible to sustain the doctrine. True, alcohol gives rise to
heat in the system, but so do other agents, whose claim to the charac-
ter of foods woidd be on their face preposterous. The question is, do
these liquors produce heat in the manner of foods, or in some unnatu-
ral and injurious way. By reference to Liebig's scale of respirants
(743), it wUl be seen that the strongest spirits drank are inferior,
pound for pound, to starch and sugar, and not nearly half so valuable
as oUy substances for a heat generator. Yet they act in such a rapid,
flashy way, as to produce preternatural excitement and irritation in the
system. In sustained calorific effect, they are not to be compared with
the aliments provided by nature, as is emphatically attested by the
concurrent experience of Arctic voyagers exposed to the utmost se-
verities of cold.

713. Dr. Bocker's Observations. — ^This gentleman tested the effects of
alcohol in small quantities upon his own person, in a course of skUfully

380 PHYSIOLOGICAL EFFECTS OF FOOD.

conducted experiments. He found that this substance diminishes both
the sohd and liquid constituents of excretion by the kidneys, that it does
not increase perspiration, that it diminishes the quantity of carbonic
acid exhaled by the lungs, while the quantity of water thrown off by
these organs remained unchanged, or, if any thing, was slightly re-
duced. The general action, therefore, was that of an arrester of the
boddy changes. As carbonic acid is hindered from being freely ex-
creted, it accumulates in the blood in poisonous quantities, and thus
. contributes to the effects of intoxication.

714. Is its use Pliysiologically Economical. — The apologists for the
general and moderate use of alcoholic beverages, cannot agree among
themselves upon any philosophy to suit the case. Dr. Moleshott
Bays, "Alcohol may be considered a savings-box of the tissues. He
who eats little and drinks a moderate quantity of spirits, retains as
much in the blood and tissues as a person who eats proportionally
more, without drinking any beer, wine, or spirits. Clearly, then, it is
hard to rob the laborer, who in the sweat of his brow eats but a slen-
der meal, of a means by which his deficient food is made to last him a
longer time." Upon which Dr. Chambees justly remarks, " This is
going rather too far. When alcohol limits the consumption of tissue,
and so the requirements of the system, whUe at the same time a man
goes on working, it is right to inquire, whence comes his new strength ?
It is supplied by something which is not decomposition of tissue ; by
what, then? " Dr. Liebig points out the consequences of that pecu-
liar economy by which the laboring man saves his tissue and the food
necessary to repair it by the use of liquors. " Spirits, by their action
on the nerves, enable the laborer to make up for deficient power (from
insufiicient food), at the expense of Ms 'body^ to consume to-day that
quantity which ought naturally to have been employed a day later.
He draws, so to speak, a bill on his health which must be always re-
newed, because, for want of means, he cannot take it up ; he con-
sumes his capital instead of his interest, and the result is the inevita-
lle 'bankruptcy of his body.''''

715. Stimulating effect of the Beverages. — They produce general stim-
ulation ; the heart's action is increased, the circulation quickened, the
secretions augmented, the system glows with unusual warmth, and
there is a general heightening of the functions. Organs, usually below
par from debility, are brought up to the normal tone, while those
which are strong and healthy are raised above it. Thus the stomach,
if feeble, for example, from deficient gastric secretion, may be aided
to pour out a more copious solvent, wliich promotes digestion, or if it

mrLUKNCE OE SPECIAL SUBSTAlirCES. 381

be in full health, it may thus be made to digest more than the body
requires. The life of the system is exalted above its standard, which
takes place, not by conferring additional vitality, but by plying the
nervous system with a fiery irritant, which provokes the vital func-
tions to a higher rate of action. This is the secret of the fatal fascina-
tion of alcohol, and the source of its evil. The excitement it produces
is transcient, and is followed by a corresponding depression and drag-
ging of all the bodily movements. It enables us to live at an acceler-
ated speed to-day, but it is only by plundering to-morrow. By its
means we crowd into a short period of intense exhilaration, the feel-
ings, emotions, thoughts, and experiences, which the Author of ocj*
nature designed should be distributed more equally through the pass-
ing time. We cannot doubt that God has graduated the flow of these
life-currents, in accordance with the profoundest harmonies of being,
and the highest results of beneficence. By habitually resorting to
this potent stimulant, man violates the Providential Order of his con-
stitution, loses the voluntary regulation and control of his conduct, in-
augurates the reign of appetite and passion, and reaps the penal con-
sequences in multiform sufiering and sorrow, — for nature always
vindicates herself at last.*

716. Efifects of Milk. — This is the food prepared by nature for the
complete nourishment of the infant. It is easily digestible, but con-
stipating. There is a difference, however, in different kinds of milk.
Cow's milk is richer in butter, or oil, than human milk, or asses' milk,
and for this reason often disagrees with delicate stomachs. By sTcim-
ming, however, cow's milk is made to approach human milk in quality.
It still, however, contains nearly all the cheese, the sugar of milk, the
salts, and some butter. It is therefore scarcely less nutritious than
new milk, but from its loss of butter is less fattening, and has a lower
power of sustaining, through respiration, the temperature of the body.
Physicians order milk when they are desirous of affording stimulus
or excitement. It is also recommended as a good diet for children,
especially in scrofulous complaints.

717. Properties and effects of Soups. — The soluble extract of various
animal and vegetable substances, obtained by boiling or steeping, forms

* " Wlien, by habit, the stimulant has become a necessity, an enervating relaxation in-
fallibly follows, as sometimes mournfully illustrated by less prudent literary men. The
stimulant ceases to excite — the debilitated oi-gans have already been indebted to it for
all the activity it can give. In this case the victim continues to seek his refuge, until
dangerous diseases of the stomach cripple the digestive powers; with the decay of the
digestive organs, the formation of blood and nutrition are disturbed ; and with the di-
gestion vanish clearness of thought, acuteness of the senses, and the elasticity of the
muscles."— (MoLESHOTT.)

382 PHYSIOLOGICAL EFFECTS OP FOOD.

soups. They are made from a great nnmber of materials, and their
effects, of course, depend upon the substances they contain. The infu-
sion of meat, which has been described (471), is easily digestible,
nourishing, and well adapted to restore the exhausted strength of in-
valids. The substance which has played the most important part in
soups, is gelatin^ the glue-principle obtained from bones, tendons, car-
tilages, and membranes. It is this element in soup, procured by long
boiling of animal substances, which causes it to coagulate and thicken
{ffelatinize} in cooling, and thus conveys to the uninstructed, the im-
pression of strength and richness. Gelatin is the principle of animal
jellies — calves' feet, blanc-mange, &c. It is an exclusive animal pro-
duct, and never found in plants, — ^pectin being the vegetable jelly
principle. Gelatin is a nitrogenous compound, but not of the protein
type. It is regarded as a product of the partial decomposition of al-
buminous bodies in the system, but is not capable of replacing them
when taken as aliment. It is questioned, indeed, if gelatin, taken as
such in food, is even capable of nourishing the gelatinous tissues. It
is digestible in the stomach along with other nitrogenous matters, and
finally contributes slightly, by its destruction to bodily warmth, thus
ranking as a respirant of low power. But even this small duty is not
performed without detriment, for while the true respirants burn com-
pletely away, gelatin loads the blood with its incombustible and nox-
ious residues. The French attempted to feed the inmates of their hos-
pitals on gelatinous extract of bones ; murmurs arose, and a commis-
sion was appointed, with Mageudie at its head, to investigate the
matter ; the conclusion of which was, that giving the poor gelatin, was
just equivalent to giving them nothing at all. The use of gelatin as a
nutritive or invigorating substance may be regarded as given up. The
utmost claim now put forth for it is, that, mixed with other food, it
makes it go further ; " but at the same time we must be careful that
it is not used in excess, as it is apt not only to weaken the individual
by its insuflBciency as an article of diet, but causes also diarrhoea,
whether by acting as a foreign body, or by some spontaneous decom-
position. Hence the unwholesomeness, to healthy stomachs, of dishes
containing a great quantity of gelatin, such as mock-turtle soup, calves'
foot jelly, &c. At the same time, to invalids they often fulfil very
inportant indications. In the first place-they dilute nuti-itious matter,
so as to render it capable of being absorbed ; then again perhaps they
line the irritable membranes with a slimy coat, and it is not impossi-
ble that in some cases they are beneficial because not nutritious, con-
stituting, in fact, an agreeable mode of abstaining from food."

ESTFLtTENCE OP SPECIAL SUBSTANCES. 383

C— Solid Aliments.

T18. Starch, as we have seen, consists of hard, highly organized
grains, enclosed in a firm envelope, so that in the raw state they defy
the action of the digestive organs. Thorough cooking of starch, to
break its grains, is therefore indispensable. We remember that the
digestion of starch, altered by culinary heat, begins in the mouth by
intermixture with saliva. Its changes in the stomach depend upon
such previous intermixture. This explains why it is that those in
whom the action of the salivary glands has been impaired (as tobacco
smokers, often), complain that starchy food lays like a weight on the
stomach. Starch prepared in the form of slops for invalids, as arrow-
root, sago, &c., is apt to be swallowed without provoking the salivary
flow, which prevents its prompt change ; hence starchy matter in the
solid form, as bread or potatoes, which require mastication, is likely
to be best digested. Starch is mainly changed in the system to sugar,
perhaps some of it becomes dextrine and lactic acid.

719. Sugar. — Of the behavior of this substance in the system, we
know very little positively. A portion of it is absorbed through the
veins into the circulation, and then burned away for the production
of heat. But it contributes to other objects also. Another part is
turned into lactic acid, which may assist stomach digestion, and serve
other important uses. Physiologists are now agreed that sugar is ca-
pable of conversion into fat in the body. To effect this change, it is
only necessary to remove its oxygen, the remaining hydrogen and car-
bon f^irnishing the constituents of oil. A deficiency of oxygen in the
system is a necessary condition of the accumulation of fat, as an ex-
cess of this agent would consume the elements, and thus prevent their
deposition. Sugar is of an acid nature, and combines with lime and
the alkalies. There is an old opinion, that sugar, when eaten freely,
attacks the teeth, corrupting them, and spoiling their color ; and re-
cent French experiments are quoted confirming this view. Dr.
Pereiea declares the opinion totally unfounded, saying that no peo-
ple on earth have finer teeth than the negroes of Jamaica, who per-
haps use sugar most liberally. " It is probable that this erroneous no-
tion has been propagated by frugal housewives, in order to deter chil-
dren from indulging in an expensive luxury. Their fondness for sac-
charine substances may be regarded as a natural instinct ; since nature,
by placing it in milk, evidently intended it to form part of their nour-
ishment during the first period of their existence. Instead, therefore,
of repressing this appetite for sugar, it ought rather to be gratified in
moderation.

384 PHYSIOLOGICAL EFFECTS OP FOOD.

720. Gam, in composition, resembles sugar and starcli, and, there-
fore, would seem to be devoted in the system to the same final pur-
pose— the production of heat ; but there is no evidence that it is
absorbed into the blood, nor indeed satisfactory proof that it accom-
plishes any alimentary purpose in the system.

721. Supply of Oily Substances. — These are furnished to the system
mingled by nature with nearly all the food we take. Milk contains
three or four per cent, of it, wheat about one per cent., rye 1"75, corn
8 or 9, ordinary meats abound in it, whUe in butter, gravies, and fat
meat, we have it concentrated and almost pure. The roots, as potatoes,
beets, &c., contain the smallest proportion of it. The system is thus
largely furnished with fat, ready prepared ; and moreover, when its
supply is deficient, it has the power of producing it out of other ali-
mentary principles, sugar, starch, and perhaps even nitrogenous sub-
stances. The physiological services rendered by the fats are manifold
and most important. In digestion and absorption, they undergo little
or no change. "We may consider their uses under a twofold aspect ;
first^ when laid up in the body, in a passive state ; and, second^ as par-
ticipating in the active changes of the system.

722. The accumulated Fat of the Body. — The necessity of some sub-
stance adapted to fill and occupy the interspaces that must occur be-
tween bones, muscles, and vessels, is obvious. There is hence extended
across these vacancies a fine tissue of cells filled with fat. But as un-
impeded motion is required in all regions of the system, the matter
built into these openings and fissures to connect the working parts
must be of a nature to facilitate movement. The lubricating, anti-
friction properties of the oils answer this requu'ement perfectly ; and
this effect becomes the more apparent when we consider that the oily
matter of the living body is kept by its heat, either entirely fluid, or
nearly so. Masses of fat tissue are interposed among the muscular
bundles of the heart to promote the ease, freedom and regularity oi
their movements. The eye, with its retinue of muscles and nerves, is
bedded in it ; it fills up the interstices of the intestinal cavity, to aid
the peristaltic motion of the bowels ; layers of it are placed on the
soles of the feet and between the bones of the joints, where it serves
similar purposes — that of pads and cushions to break the effect of
shocks, and the mechanical violence to which the body is constantly
liable. Besides, deposited in the layer of cellular tissue, under the
skin, it relieves abrupt inequalities of the surface, and rounds the out-
line into curves of grace and beauty, as we notice most conspicuously
in women and children. " The fat which smooths the bony corners

ESTPLUENCE OP SPECIAL SUBSTANCES. 385

and angles, and the narrow muscles of the face, is the cosmetic em-
ployed by nature to stamp the human countenance with the incom-
parable impress which exalts it far above all the lower animals." Fat
in a fluid state is also a very lad conductor of heat, so that the layer
of it which nature provides under the skin answers an important pur-
pose in protecting the body from the eflfects of extreme heat and cold,
and sudden changes of temperature. Finally, in the course of our
experience upon this water-drenched planet, it is often desirable that
we should be able to swim, and this is only made possible by the
extreme lightness of the fatty parts of the body. Were the fat con-
tained in our systems as heavy as water, swimming would be imprac-
ticable ; besides entaUing upon the muscles the increased labor of
moving the more weighty limbs and body under ordinary circum-
stances.

723. Behavior of Fats in the Stomach. — "We have seen that fats are
not digested in the stomach, but are reduced to a fine state of emulsion
in the intestiaes, so as to be capable of absorption. But it has been
found that their presence is essential to stomach digestion. Lehman
ascertained " that a certain, though small quantity of fat, was indis-
pensable to the solution of nitrogenous articles of food during the
process of gastric digestion." Elsassee observed in experiments on
artiflcal digestion, that the solution of articles used as food is consider-
ably accelerated by means of fat. It has been found ia the case of
dogs with artificial openings in their stomachs, that flesh which had
been designedly deprived of fat laid longer in the stomach, and there-
fore required a longer period for its change than the same substances
when mixed or impregnated with a little fat. Yet on the other hand
excess of fat exerts an injurious action, especially in persons of weak
digestion. Fat ia small amount is thus necessary to digestion ; in the
considerable proportion which the system requires, it ought not to
derange the gastric apparatus ; but that it is actually a powerful dis-
turber of digestion, in very numerous cases, is well understood. It is
probable that those principles which are designed to be dissolved in
the stomach, may be so enclosed and pervaded with fat as to cut off
the access of the solvent juice, and thus greatly hinder solution. The
way in which fat is distributed among the muscular fibres of meat, for
example, is one thing that makes it more or less easUy soluble by
Btomachs deficient in gastric juice. " Mutton owes its good character
for digestibility to the little fat there is among its close-grained fibres,
while the flesh of the ox is infiltrated with oleaginous matter through-
out. The oU envelops the fibres when in the stomach, prevents their
17

886 PHYSIOLOGICAL EFFECTS OP FOOD.

being permeated by the gastric secretion, and so renders beef indiges-
tible to all but robust persons. The absence of fat in fish, and iu
poultry, is one great cause of their easy digestibility in the stomach,
though their ultimate fibre is less easily soluble than that of red meat.
Meat or fish fried or otherwise dressed with grease is thereby ren-
dered less digestible to weak stomachs, though to those whose gastrio
juice is sufficiently plentiful to wash away the oily envelope and pene-
trate the muscular fibre, it is wholesome. — (Chambees.) Even the
healthy stomach often recoils at certain combinations of fat, starch
and gluten, as in the instance of the oily meats of nuts, filberts,
almonds, walnuts, &c.

Y24. Cooking inflaences the Digestibility of Fats. — The effect of cook-
ing upon fatty substances is generally to render them less agreeable to
the stomach, especially if the organ be weak. "When speaking of
butter, we noticed the complex composition of fats and their
liability to be decomposed into various offensive substances. Heat
effects these changes rapidly, and to an extent proportional to its in-
tensity. In some, as butter, the bare act of melting produces an un-
favorable alteration, which the morbidly delicate stomach detects. In
frying, the temperature runs high, tending to decomposition and the
production of various acrid and irritant fatty acids. Fatty matters
thus changed, or even predisposed to change, are Uable to become
rancid by the fermenting action of the stomach, producing heartburn
and nausea. This explains why cakes are less healthy and digestible
than bread. The large proportion of butter, cream, and eggs, (the
yolks being rich in oil,) which are usually contained in cakes, and the
changes they undergo at the high heat of baking, impairs their diges-
tibility. Dr. Peeeiea remarks : " Fixed oil or fat is more difficult of
digestion, and more obnoxious to the stomach, than any other ali-
mentary principle. Indeed, in some more or less obvious or concealed
form, I believe it will be foimd the offending ingredient in nine-tenths
of the dishes which disturb weak stomachs. Many dyspeptics, who
have most religiously avoided the use of oU or fat in its obvious or
ordinary state, (as fat meat, marrow, butter, and oU,) unwittingly em-
ploy it in some more concealed form, as yolk of eggs, hvers of animals,
rich cheese, fried dishes, buttered toasts, suet puddings, &c." Dr.
Chambees says : " Fatty food can be taken without pain by gastric
invalids, very closely in proportion as it is fresh, and without rancidity.
New made butter often agrees, when the empyreumatic fat in baked
meat makes it utterly indigestible. If there .is much emaciation, it is
right to try several forms of oleaginous food in each case, to see if one

HTPLUENCB OP SPECIAL SUBSTANCES. 387

cannot be found capable of supplying nutriment to the failing adipose
tissue."

725. Relation of the Fats to IVatrition. — The fats are ranked as respi-
ratory aliments, but it would be a great mistake to suppose that after
absorption from the intestinal passage into the blood they are simply
burned away for heat ; before their destruction they serve other and
capital uses in the body. Fat is an essential constituent of the braia
and nervous system ; it is thus one of the prime material substances
destined to establish communication between miad and matter. It
has also been lately maintained that fatty substances have an essential
share in the tissue-making process. They do not furnish the material,
and we do not know how they act ; but it is agreed that their pres-
ence is necessary to the formation of ceUs and the growth of the
bodily structure. Thus, in point of fact, oleaginous substances, though
at the head of respiratory aliments, are indispensable to nutrition.

726. Oleaginous Diet and Consamption. — ^Masses of crude unorganized
matter containing coagulated albumen and half-formed cells, and
called tubercles, are sometimes found in the lungs, producing tubercular
consumption. The immediate cause of the disease is an abortive or
perverted nutrition, tubercle being produced instead of true tissue.
The seeds of consumption are most generally sown in the system in
youth, when there is a double demand upon nutrition, for current
waste and steady growth. There is, however, suiEcient nitrogenous
matter present to nourish the structures ; some other condition must
therefore be wanting. It has been lately maintained that the faulty
nutrition which results in tubercle, is caused by a deficiency of oily
substances, and therefore such of these bodies as are easiest digested
and absorbed have been indicated as remedies. Cod Liver Oil has
come into use for this purpose. Dr. Hughes Bennett, who first in-
troduced this oil to the notice of the English and American public,
states that butchers, cooks, oilmen, tanners, and others who are con-
stantly coming in contact with fatty matter, are less liable than others
to tubercular disease ; and Dr. Simpson has observed that chUdren and
young persons employed in wool factories, where large quanties of oil
are daily used, are generally exempt from scrofula and pulmonary con-
sumption. These facts would indicate that even absorption of fatty
matter through the skin may powerfully influence nutrition. Dr.
Bennett says that, to prevent consumption during youth, indulgence
in indigestible articles of food should be avoided, especially pastry,
unripe fruit, salted provisions, and acid di-inks, whUe the habit of
eating a certain quantity of fat should be encouraged, and, if neces-

388 PHYSIOLOGICAL EFFECTS OP FOOD.

sary, rendered imperative. Dr. Carpenteb observes : There is a strong
tendency, and increasing reason to believe that a deficiency of ole-
aginous matter, in a state fit for appropriation by the nutritive
processes, is a fertile source of diseased action, especially that of a
tuberculous character ; and that the habitual use of it in larger pro-
portion would operate favorably ia the prevention of such maladies,
as cod liver oil unquestionably does in their cure. A most remark-
able example of this is presented in the population of Ireland, which,
notwithstanding the concurrence of every one of the circumstances
usually considered favorable to the scrofulous condition, enjoys a
most remarkable immunity from it, without any other assignable
cause than the peculiarly oleaginous character of the diet usually em-
ployed. Dr. Hooker, in a report on the diet of the sick, says : 1st.
Of all persons between the ages of 15 and 22 years, more than one-
fifth eat no fat meat ; 2d. That of persons at the age of 45, all except-
ing less than one in fifty, habitually use fat meat ; 3d. Of those who
have abstained, a few acquire an appetite for it and live to a good old
age, while the great proportion die of consumption before 45 ; 4th.
Of persons dying of consumption between the ages of 15 and 45,
nine-tenths at least have never used fat meat.

727. Effects of Fndae Proportions of Alimeatary Principles. — The di-
gestion and final use of the nitrogenous principles have been explained.
When taken in too great quantity, they charge the system with im-
perfectly assimilated compounds and wrongly-changed products of de-
composition, which are not promptly expelled, and which produce a
gouty state of the constitution, besides influencing the course of other
diseases. The excess of oily substances in the food tends to increase
the proportion of fat in the body. If more is taken than can be stored
up, or consumed by oxidation, and thrown from the skin and lungs,
the burden of disposing of it falls upon the liver, the blood becomes
charged with the elements of bile, and a MUoiis condition of the sys-
tem results. The rheumatic state of the body, like the gouty, is sup-
posed to be connected with mal-assimilation ; but rather with a de-
ficiency of albumen and an excess of lactic acid, derived from a rich,
starchy, and saccharine diet. A deficiency of oleaginous substances
tends, as we have just seen, to produce the scrofulous state, and alack
of fruits and fresh vegetables engenders the soorhutic condition of body,
or scurvy.

728. Flesh Meats. — Having considered the action of the constitu-
ents of flesh, little needs to be added here concerning their combined
eflfect. The less the fibre of meat has been dried or altered by cook-

INFLUENCE OF SPECIAL SUBSTANCES. 389

ing, the more juicy and abounding in soluble albumen, and the less its
fat has been changed from the condition of perfect freshness, either
by heat or other causes, the more digestible it is. The flesh of young
animals contains less fibrin than that of old ones, but more soluble al-
bumen and gelatin, and is hence more tender. This preponderance of
gelatin explains why the broth of veal and lamb coagulates sooner in
cooling than that of beef and mutton. Albumen is usually considered
the most digestible form of nitrogenous matter. But as the acids of
the stomach coagulate it before digestion, it does not appear that liquid
albumen is more digestible than that partially coagulated. Eggs
boiled, not too hard, are therefore quite as digestible as if taken raw.

729. Preparatiofls of Flour. — Of the products of grain and flour
which we get in multifarious shapes, baked and boiled, it may be
said, their digestibility depends first and mainly upon their condition
as respects lightness or heaviness. The porous and spongy state, as in
good bread, is most favorable to the penetration and action of the di-
gestive juices, while glutinous masses in a dense compact condition,
especially if charged with fat, are the torment of weak stomachs, re-
quiring the strongest digestive powers for their reduction. It is very
difficult to preserve the loose and open texture of flour-paste, or
dough in boiling, and hence pastry, dumplings, &c., are very rarely
light or digestible. Dr. Paeis remarks, " All pastry is an abomina-
tion. I verily believe that one-half at least of the cases of indiges-
tion which occur after dinner-parties, may be traced to this cause.
The most digestible pudding is that made with bread or biscuit and
boiled flour ; latter puddings are not so easUy digested, and suet pud-
ding is to be considered the most mischievous to invalids in the whole
catalogue." Dr. Lee observes, " It is doubtful whether there is any
way of boiling wheat dough so as to render it fit for food ; it wiU al-
ways be crude, and heavy, and impermeable to the gastric juice. Our
best puddings are those made of rice, bread, sago, or Indian meal
baked. Boiled Indian puddings are not very indigestible, and are far
preferable to those of wheat."

T30. Coarse and Fine Bread. — As respects the final or nutritive
effects of groimd grains, it makes every difference whether they be
bolted or unbolted. We have stated the composition of flour from the
interior of the seed, and the whole flour, which includes the bran
(Ml). The fine or bolted flour has less of the fibre-building gluten,
and is therefore less nourishing and strengthening. The unbolted
sorts, and even the dark-colored sorts, through which finely-pulver-
ized bran is diffused, are more digestible ; the fibrous or ligneous par-

390 PHYSIOLOGICAL EFFECTS OF FOOD.

tides act as a kind of mechanical divisor, separating and diluting the
highly-concentrated food, rendering the mass looser and more pene-
trable to the solvent liquids, and submitting it more gradually to the
membranous absorbing surface. The ground grain, or woody fibre,
mingled with the flour, together with the adhering oil, are further ser-
viceable by promoting the action of the intestines. Bread from fine
flour is constipating, while that from whole flour has an aperient ten-
dency, although it is not purgative. Unquestionably, coarse bread is
much superior to fine for maintaining the free and regulated action of
the boweis, and Mr. Geaham insists strongly, as the result of large ob-
servation, that coarse bread is corrective, not only of undue consti-
pating tendencies, but also of morbid and chronic laxity ; though at
first it may seem to aggravate the symptoms, yet the final result is de-
clared to be most decidedly beneficial. Besides, in the fine flour we
miss the full proportion of the elements of bone and tooth nutrition,
the essential mineral phosphates. The nourishment of the bony parts
must be deficient, having less volume, solidity, and strength, with a
diet of fine bread than with the coarser varieties. We have sacrificed
several most important qualities, and gained only tohiteness. We trifle
with the first conditions of health to gratify a fancy of the eye.

731. Beans and Peas. — The digestibility of these is much dependent
upon their preparation. When old and hard, and cooked with their
husks and shells, and more especially if boiled in hard water, which
prevents the softening and solution of their nitrogenous matter, they
are apt to be very indigestible and heating, occasioning flatulence and
sometimes colic. When boiled in soft water, the nutritive pi'inciple
softens, partially dissolves, and becomes more digestible if the husks
are separated by passing through a hair sieve. Soup is, therefore, the
best form in which dried beans and peas can be taken.

732. Vegetables. — The healthful and indispensable influence of fresh
vegetables in diet is undoubted. They are rich in valuable saline sub-
stances, essential to the system, and probably act by these as antiscor-
butics,— preventives, and remedies of scurvy. They of course vary in
digestibility, according to the proportion of their constituents, and the
thorough softening and decomposing effect of culinary heat. Most
esculent vegetables abound in indigestible ligneous tissues, which pro-
voke intestinal movement, and thus incline to produce aperient effects.
Leaves and young shoots contain organic acids ; thus, asparagus and
the whole cabbage tribe contain acid of apples, or malic acid ; rheu-
barb, malic and oxalic acid ; white cabbage converted into sour krout
ferments and yields large quantities of lactic acid. These acids may

raiXUENCE OF SPECIAL STIBSTAIiTCES. 891

contribute to stomacli-cligestion, promoting the solution of the more
nutritive aliments. In the case of fruits, which are still richer in
acids, this effect is more marked.

Y33, Edible Roots, of which the potato ranks first, are superior in
dietetic importance to the vegetables just refei'red to. Besides their
chief constituents, water, starch, and albumen, potatoes contain malic
acid and asparagin^ a nitrogenous substance existing also in asparagus.
Potatoes are rich in aU the mineral ingredients required by our bodies,
and are of permanent value against scurvy ; they especially abound in
potash. Turnips contain no soda, but httle iron, and considerable
potash. Onions have a peculiar volatile oU which is not assimilated
or destroyed by the body, but escapes through the lungs, contaminating
the breath.

734. Frnitt — The delicious and refreshing taste of fruits is caused
by a combination of sweets and sours, sugars and acids. The sour taste
predominates in the green fruit, for although the quantity of acid in-
creases as the fruit ripens, yet the sugar increases so much faster, that
there is a gradual sweetening as the fruit matures. In ripe fruits the
acids are enveloped in sugar, just as in stewed fruit they are in the
vegetable jelly, produced by stewing. In stewed and prepared fruit,
the sugar and jelly cover, or, as it were, mask the acids and salts, and
thus check their irritating action upon the interior coating of the di-
gestive passage. The following suggestions of Liebig concerning, the
value of apples, afford us hints of the utility of fruits generally.
" The importance of apples as food has not hitherto been sufficiently
estimated or understood. Besides contributing a large propertion of
sugar, mucilage, and other nutritive compounds in the fonn of food,
they contain such a fine combination of vegetable acids, extractive
substances, and aromatic principles, with the nutritive matter, as to
act powerfoUy in the capacity of refrigerants, tonics, and antiseptics,
and when freely used, at the season of ripeness, by rural laborers and
others, they prevent debility, strengthen digestion, correct the putre-
factive tendencies of nitrogenous food, avert scurvy, and probably
maintain and strengthen the power of productive labor."

Y35. Seasoning Agents, or Condiments. — Substances taken in small
quantities for the purpose of flavoring, and rendering foods palatable,
are called condiments. Few or none, however, are merely limited to
this effect ; they serve other purposes besides ministering to the taste.
Sugar, oil, acids, and common salt, have been described as aUments,
but they are also employed as condiments.

736. Chceset — We may regard cheese as an aliment when consider-

^92 PHYSIOLOGICAL EFFECTS OF FOOD.

ing it as composed simply of casein and fat, to be digested and ab-
sorbed. Thus regarded, it is a highly concentrated food, diflBcult of
digestion. But it is also used in small quantities in a condimentary
way, and may thus possess active properties in relation to digestion.
Old, changed, and mouldy cheese has long had the reputation of being
a digester, that is, of assisting in some manner the action of the stom-
ach, and for this purpose it is often taken in trifling quantities after a
meal. Being in a state of decomposition, it is capable, when mingled
with the contents of the stomach, of excitiag fermentation, and thus
of assisting the process. Of course, if the cheese be fresh, or not ia
the mouldy, putrefactive condition, it can be expected to produce no
such result.

Y37. Vinegar, in small quantities, by augmenting the acidity of the
stomach, may help digestion, assisting the solution of albumen, gluten,
and fibrin. It does not, however, dissolve the legumin of peas and
beans, but rather precipitates it from solution. An idea has prevailed
that the free use of vinegar promotes leanness. However the fact may
be, the experiment of reducing corpulence in this way is fraught with
the danger of establishing deeply-rooted disease (775).

738. Spices, &c. — A class of substances rich in pungejit oils, — horse-
radish, mustard, pepper, cloves, and various spices, are in extensive
request as condiments. These oils produce a heatiag, irritating effect
upon the organs of taste, and the stomach ; upon entering the blood,
they increase the circulation, and give rise to stimulation. " Con-
diments, particularly those of the spicy kind, are not essential to the
process of digestion, in a healthy state of the system. They afford no
nutrition. Though they may assist the action of a debilitated stom-
ach for a time, their continual use never fails to produce a weakness
of that organ. They affect it as alcohol or other stimulants do — the
present relief afforded is at the expense of future suffering. Salt and
vinegar are exceptions, and are not obnoxious to this charge, when
used in moderation." — (Dr. Beatjmon^t.)

10. NuTEiTivE Value of Foods,

739. Limitation of the Nutritive Powers. — It is to be expected that
Bubstances differing so widely as those which constitute food — sub-
stances of such various composition — some contatniDg nitrogen, while
others are free from it, some containing sulphui", others none, some an
excess of carbon, others the reverse — must serve very different pur-
poses in the economy. Each has its special work to do, while their
duties are not interchangeable. A certain degree of variety is thus

ITS NUTRITIVE VALUE. 393

the fundamental requirement of the system ; and accordingly we find
that where nature herself has prepared the food, as in the case of
the mother's milk for her young, it is always of a mixed nature,
emhracing alimentary principles of very diflferent composition. We
have no shadow of evidence that the living hody possesses the power
of converting one element into another ; it cannot transmute hydrogen
into nitrogen, or carhon into phosphorus ; if it lack an element, it
must suffer the inconvenience of deficiency. As regards the conver-
sion of one compound into aiiother, the system has a limited faculty
of this kind in a certain direction ; it can efiect some changes, as we
have seen ; it cannot efiect others. It can destroy compounds by a
progressive series of changes, each descending step being a new sub-
stance, but it cannot work upward in a formative direction, — that is
the ofiice of plants. The materials necessary to form a compound may
be present in the body without any power whatever to produce it.
The dissevered constituents of used-up tissue, exist in the blood, but
it is entirely incapable of reconverting them into tissue. Nor has the
body the power of transmuting the respiratory group of aliments into
the albuminous, or of enabling the former to replace the latter, in the
exigencies of the animal economy. It cannot make starch do the
work of gluten. " That none of the non-nitrogenous substances can be
made capable, by metamorphosis or combination within the animal
body of taking the place of the nitrogenous or plastic compounds, may
now be regarded as one of the most certain facts in physiology ; the
concurrent evidence of experiment and observation tending to the
conclusion, that in plants alone can any production of nitrogenous
compounds take place. If animals be fed exclusively on saccharine or
oleaginous substances of any kind, or in any combination whatever,
they speedily perish with symptoms of starvation." — (Dr. Oaepentee.)
As the system has no mysterious energy to change what it wUl and as
it will, its action being absolutely limited, it follows that its nutritive
supplies must be adapted to its wants.

740. Mixed Diet Indispensable. — Our diet thus requires to be of a
mixed nature, comprehending such a variety of materials as to supply
the whole range of bodily wants, and moreover, should be varied with
the varying circumstances of growth, bodUy and mental exercise, tem-
perature, and numerous changing requirements of the system. Hence
the impossibility of prescribing any thing like precise and invariable
rules in reference to the quantity and proportions of alimentary sub-
stances. "We now call attention to the comparative values of nutritive
substances, in certain important respects, as based upon composition,

17*

304

PHYSIOLOGICAL EFFECTS OF FOOD.

and experience of their eflfects. "We shall have occasion to note both
agreement and discordance, in many particulars, between general
habits and the indications of science.

Y41. Proportions of Solid Matter and Water. — The following scheme,
Kg. 121, illustrates the proportion of solid matter and water contained
in the principal articles of diet. They were dried at 212 ; the results
are averages of statements by the best authorities. The length of the bars
represent the proportion of dry solid matter in 100 parts, the remain-
der of the hundred indicated by the scale being water. The preva-

FiG. 121.
PEOPOETION OF SOLID MATTES AND WATER EST FOODS.

1.0 , 20 , 3,0 , 40 , 5.0 , 60 , 7,0 80 , 90 100

Wheat, Peas.

Eice, Eye, Beans, Corn.

Wheat Bread.

Mutton.

Chicken.

Lean Beef

Eggs.

Veal.

Potatoes.

Pork.

Cod.

Blood.

Trout.

Apples.

Carrots.

Beets.

Milk.

Oysters.

Muskmelon.

Cabbage.

Turnips.

Watermelon.

Cucumbers.

The length of the bars represents upon the scale, the percentage proportion of solid mat-
ter in the various articles of diet, opposite to which they are placed.

lence of the aqueous element in diet, is thus strikingly apparent. Most
of the articles contain Y5 per cent, water ; some much more. The
grains are driest, but in being reduced to bread they become more
than half water, and even then we take additional liquids freely whUe
eating it. "Water is essential to food, but to make the best statement
of its nutritive value, we must throw this constituent out of the ac-

ITS NUTEITIVE VALUE.

,395

count, and regard only the dry matter. But the quantity of solid sab-
stance left, is no guide to its nutritive effect ; potatoes and lean beef
have the same proportion of water, but they are certainly widely apart
in nutritive power,

742. How far we caa measure Nutritive Values. — A fall view of the
nutritive value of foods, requires us to take into account all their
effects ; but we are as yet far from being prepared to do this on any
systematic or comparative scale. The nearest approach to a state-
ment that can be ventured, is by classifying foods in reference to the
two great leading purposes which they serve in the system — forma-
tion of tissue, and production of heat — the proportion of the nutritive
to the calorifient principles. This division, although fundamentally
true, and capable of being embodied in a valuable shape, we take with
its qualifications ; for as has been stated, the respiratory principles
contribute also to nutrition, while the albuminous may produce
heat (666).

743. Different valaes of the Respiratory Principles. — The albuminous
substances are identical in composition, and have equal nutritive
powers; whether in the form of gluten, fibrin, casein or albumen,

EELATIYE POWEEB OF THE

Fat

HEAT-PEODTJOma PEINCIPLES OF FOOD.
Fig. 123.

Btarch.

Cane Sugar.

Grape Sugar,

Spirits, BO per ct. Alcohol.

Lean Flesh.

The relative lengths of the bars illnstrate the comparative amount of heat produced in
the system by equal weights of the substances mentioned.

they are replacable in nutritive effect, Not so, however, with the
calorifient principles; their heat-giving powers are very unequal.
The preceding diagram (Fig. 122), exhibits the relative proportions
of heat produced by equal weights of the substances mentioned. It
will be thus seen that 10 parts of fat go as far as 24 of starch in
generating heat. This is Liebig's estimate. He calculates the oil as
starch, by multiplying it by 2*4. Thus the 9 per cent, of oil in Indian

396 PHYSIOLOGICAL EFFECTS OF FOOD,

corn, -would be equal to adding 22 per cent, to its real amount of
etarch. In this way, the nutritive and calorifient powers of foods are
readily brought into comparison. It appears from this estimate of
L1EBI&, that the strongest spirits are not only incomparably inferior
to the oils, in heat-producing power, but also rank decidedly below
starch and sugar (712). When we remember that alcohol is derived
from sugar by a destructive process, in which half the saccharine sub-
stance is lost, and that the product obtained is stdl below sugar on
the heat-making scale ; it is clear, that the use of alcohol as a respira-
tory substance, is any thing but good economy.

744. Bad Economy of an exclusive Meat Diet. — It is seen by the fore-
going scale, that lean meat is the feeblest of all respirants. If it is to
be employed, not only for nutrition, but to produce heat, an enormous
quantity of it must be consumed. As the largest alimentary demand
of the system is for carbon and hydrogen to support respiration, the
nitrogenous principles being low in these elements, afford the least
economical diet that can be adopted. Thus it has been calculated,
that since fifteen lbs. of flesh contain no more carbon than four lbs. of
starch, a savage with one carcass and an equal weight of starch,
could support life for the same length of time, during which another,
restricted to animal food, would require five such carcasses in order to
produce the carbon necessary for respiration. The misture of the nitro-
genous and non-nitrogenous compounds, (gluten and starch,) that exist
in wheat flour, seems to be just that which is most generally useful to
man ; and hence we see the explanation of the fact, that from very
early ages, bread has been regarded as the ' staff of life.'

745. Equilibrium of Values Disturbed. — When the due proportion
demanded by our physiological welfare, is struck, between the nutri-
tive and respiratory principles, they may be regarded as of equal
values ; that is, they are both, in their just relative amounts, equally
necessary, and a diminution of either produces injury. But under
ordinary circumstances, the nitrogenous matters are most diflicult to
obtain. They exhaust the soil most, and the tendency of cropping is
to reduce their proportion in equal weights of alimentary products.
They represent animal power, are more complex and highly organized,
are less easily produced, and more destructible than the other group.
The value of foods, therefore, under ordinary circumstances, rises and
falls mainly in correspondence with the "proportion of these constit-
uents. But in case of famine, or arrest of production, these conditions
are reversed. Crops of green roots and vegetables, the immediate
and principal sources of respiratory food, in the shape of starch, sugar,

ITS NXTTEITIVE VALUE.

397

<

and oil, are cut off. "We fall back upon the animal world, but this is
chiefly a grand store of nitrogenous matter, without its due proportion
of other constituents. The balance being thus lost, respiratory food
rises in demand and value.

746. Proportiott of Nutritive to Calorifient Principles. — The following
scheme represents approximately the values, nutritive and calorifient
— building materials and fuel — of various articles of food. It must be
received as only a general or outline expression of the facts. Dififerent
samples of the same food vary in composition ; an average is the best
result that can be obtained.

Fig. 123.

OOMPAEATIVE SCALE OF THE NUTRITIVE AND EE3PIEAT0ET VALUES OF

VAEIOUS AETIOLES OF FOOD.

Nutritive or tissue-
forming principles.

*Veal.

Hare.

Dried Beef.

Eggs.
Beef.

Calorifient or heat-pro-
ducing principles.

Peas.

Eat Mutton.
Pork.
Cow's Milk.
Human Milk.
"Wheat riour.
Bye Flour.
Wiiite Potatoes.
Indian Corn.
Turnips-
Blue Potatoes.
Eice.
Buckwheat Flour.

Arrow-root, sa
go, tapi
corn-starch

, sa- (
ioca,-<
rch. (

This scheme represents, by the relative length of the bars, the proportion of nitrogenous to tho
non-nitrogenous principles in each article given, the latter being all reduced to the value of
starch. The upper part of the scale represents those foods which are highest in proper nutri-
tive power, and lowest in heat-producing eifect, while tho lower portion exhibits those
which are lo^vest in nutritive, but highest in calorifying effect.

* The authorities for the above scale are as follows, in numerical order, counting from the
top downward: 1, 2, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 17, 18, 19 (Likbig); 3, 4, 16 (Prof. John-
ston) ; 20 (Prof. E. D. Thompson) ; 15 (Author),

398 PHYSIOLOGICAL EFFECTS OF FOOD.

The point to wMch we called attention in the previons paragraph
must not be forgotten, or the scheme will certainly mislead ns.
The calorifient principles are reduced to the expression for starch, so
that wherever fats are involved, the respiratory equivalent appears
higher than the quantities furnished by analysis would otherwise war-
rant. Thus, if we take the weight of the casein of milk to represent
its nutritive power, and the combined weights of the sugar and butter
to represent the respiratory effect, we shall get a result different from
that in the table, 10 of nutritive, to 18 or 20 of respiratory food.
LiEBiG says in substance, in connection with this statement, that the
relative proportions of the nutritive constituents 'jQ milk, to its butter
and milk-sugar, that of the plastic matter of flesh to its fat, and of
the albuminous substance of grain, potatoes, peas and beans to their
starch, are not constant. They vary in milk with the food ; fattened
flesh contains more fat than that which is lean ; and the difference be-
tween the two kinds of potato shows how great may be the variation
in different varieties of the same plant. But the above may be re-
garded as average numbers lying between the opposite extremes in
each case. We may consider as constant the following results,
namely, that peas, beans, and lentils contain for one part by weight of
plastic matter, between two and three of non-nitrogenous matter
ranked as starch ; that grains, such as wheat, rye, and oats, contain be-
tween five and six parts, potatoes from eight to eleven parts, and rice
and buckwheat from twelve to thirteen parts of the latter, to one of
the former.

747. NatritiTe Powers of Blilk. — The above scheme is rich in sug-
gestions. The starting point of all inquiries into the nutritive quali-
ties of foods is milk. It is the only complete or typical aliment fitted
to nourish the entire body ; the only dietetic prescription that nature
has furnished to fill the full circle of bodily wants. The water is there
in large proportion to supply the necessary Hquids, the mineral salts,
to build the bony framework, the casein to form the tissues, and but-
ter and sugar to sustain the bodily warmth. Not only does it contain
every thing the system requires, but in proportions exquisitely adapted
to the demands of peculiar and varying conditions. It is the appointed
diet of the infant, the chief business of which is to grow. Its diet
must, therefore, not only be adjusted to meet its current waste, but it
requires to be especially rich in the structure-making constituents, and
such is the fact. The weight of the nitrogenous curd to the butter
and sugar, is as high as 1, to 2 or 3. But see how admirably nature
modifies these proportions to suit special occasions. Of all the young

rNPLUENCE OP SPECIAL SUBSTANCES.

399

of the animal world, none lead so quiescent a life, or advance so slow-
ly to maturity, as does the human infant. The young of other ani-
mals more quickly develop, and are called upon to put forth exertion
much earlier. Hence the milk of these animals, as for example the
cow, is richer in the curdy, or huUding and strength-giving principle
than human milk.

748. Wheat resembles Milk and Blood. — Wheat, by universal consent,
ranks first in nutritive value among grains. It abounds in the valua-
ble elements which the body requires — mineral matter for bones, glu-
ten for tissue, starch for respiration. Its deficiencies are water and
oil ; the former we supply in converting it into bread, and the latter
by the universal custom of using butter with it when eaten. Another
great advantage of wheat is, that its gluten is pre-eminently of that
quality which yields the lightest and most digestible bread. The near-
ness of wheat flour in chemical composition to milk and blood, ia
shown in the following analytical statement :

Flour.

Blood.

Mm.

Fibrin,

- Fibrin, '

Albumen,

Albumen,

Albumen,

Casein,

Casein,

Casein,

Gluten,

■ Coloring matter,

Oil and starch,

Fats and oils,

Butter,

Sugar,

Sugar, ■

Milk-sugar.

Chloride of potassium.

■

Chloride of sodium.

Phosphate of soda,
" " lime,

Ditto.

Ditto.

" " magnesia,

" « iron.

749. How Wheaten preparations meet the losses of the System. — The

attempt has been made to determine the daily consumption in the sys-
tem of nutritive and respiratory matter. The problem is most difii-
cult, and the results thus far only average and approximative. It is as-
sumed that the waste of tissue is about a grain a minute, or 62 grains
per hour, or somewhat more than 3 oz. per day. Poggaile states
that the researches of the last 20 years have shown that an adult la-
loring man consumes each day between 11 and 12 ounces of heat-pro-
ducing principles, and about 4^^ ounces (dry) of nitrogenous matters,
charged with the regeneration of the tissues ; that his nourishment is
not complete unless it is formed of one part nitrogenous matter and
four parts respiratory. Beneke, fi'om an examination of the diet
scales of various educational, invalid, and penal establishments in Lon-
don, obtains the result that the nitrogenous should be to the non-nitro-

4.00 PHYSIOLOGICAL EFTECTS OE FOOD.

genous as one to five. Feeeiohs calculates that tlie daily consump-
tion should be 2-l'I ounces avoirdupois of nitrogenous, and 15'54 ounces
of non-nitrogenous food, that is, about as one to seven. Wheat aver-
ages, perhaps, one to five. But starch is a bulky form of respiratory
aliment, and hence it is only by the use of very considerable quanti-
ties of bread, that enough of this ingredient can be procured to sus-
tain the temperature. Butter, a more concentrated heat-producer,
comes in to assist in relieving this difficulty, and as wheat is almost
entirely destitute of oil, it is highly probable that butter is also in-
stinctively added to promote its digestion.

750. Variations in Nntritive Value of Wheat. — The proportion of nu-
tritive to respiratory principles in wheat, fluctuates much, which of
course, affects its value correspondingly. Flour containing 9 per cent,
of gluten must give rise to very different physiological effects from
that containing 18 per cent. The large proportion will produce the
blood constituents most copiously, and yield most strength. Yet, as
we have repeatedly stated, commercial and nutritive values, so far
from coinciding, actually antagonize. Instead of the increasing pro-
portion of nitrogenous compounds being any indication of the price
which win be paid for wheat, it is quite the reverse. "We prize and
estimate flour directly in proportion to its whiteness, which is gener-
ally in inverse ratio to the proportion of its gluten. We give most for
the wheat that wiD nourish least. As the chief object of the farmer
is to produce an article which will command the highest marTcet price,
he has no inducement to cultivate grains rich in albuminous com-
pounds, but a double motive for the contrary course ; those which are
deficient in these elements exhaust the soil less and bring most money.
751. High JVntritive Power of coarse Bread. — In the seventeenth
century, Vatjban estimated the annual consumption of a man at near-
ly 712 pounds of Avheat, a quantity which now nearly suffices for two
men ; and by the improvements in mills, there are now gained to the
population immense masses of nutritious matter, of the annual value
of many millions, which were formerly used for animals ; the bran
may be far more easily replaced by other food not in the least adapted
for the use of man. The high value of bran for food has been long
ago pointed out. Wheat does not contain above 2 per cent, of indi-
gestible, woody fibre, and a perfect mill should not yield more than
that proportion of bran, but practically, the best mills always sepa-
rate, even now, from 12 to 20 per cent. (10 per cent, coarse bran, 7
fine bran, 3 bran flour) ; and the ordinary mills produce as much as 25
per cent, of bran, containing 60 or 70 per cent, of the most nutritious

ITS NUTEITIVE VAiUE. 401

constituents of the flour. By baking bread with unbolted flour, the
mass of it may be increased from one-sixth to one-fifth, and the
price of it lowered hy the difference 'between the price of the bran as
fodder for cattle, and that of the flour gained by not bolting it.
The separation of the bran from the flour by bolting is a matter of
luxury, and injurious rather than beneficial as regards the nutritive
power of the bread — (Liebig).

752. Aliments may be corrected by Intermixture. — Lean flesh is the
most concentrated form of nutriment, is easily digested, and quickly
converted again into muscle. Yet, though a most perfect mitrimenf,
it is least fitted to meet the complete demands of the system. It is
not a complementary food, like wheat, answering to the double re-
quirements of the body ; its deficiency of respiratory matter makes it
necessary to consume with it fats and gravies, or else join it with
those substances at the opposite extremity of the scale, rice, potatoes,
vegetables, &o., which abound in calorifying matter, but are deficient
in the nutritive. On the other hand, if we attempt to live exclusively
on rice, potatoes, or vegetables, in order to procure suflicient of the
flesh-producing ingredients, we must consume an enormous bulk of
respiratory matter, so much more than is needed, as to produce de-
formity and disorder of the system. It is easy to see, however, by
reference to the preceding scale, that we can make such combinations
of dietetical articles, as shall compensate for natural deficiencies. In-
deed, the due admixture of these different principles of food, is a vital
and immanent necessity, which, if disregarded, makes itself quickly
felt in physiological derangement, so that man's instincts have sufficed
to guard him in many cases against broad departures from the proper
and healthy course. In aU countries we notice dietetical adjustments
tending to the same physiological end. In the coarsest and crudest
diet of barbarous tribes, or the high- wrought luxuries of the refined,
the same instinctive cravings are ever regarded — the same purpose of
nature is always in view. Potatoes and vegetables, with beef, mutton,
and pork, are almost universal combinations. Beans and peas, which
are the most highly concentrated vegetable nutriments, are associated
with fat pork, in the weU-known dishes — 'pork and beans,' 'pork
and peas pudding,' and the extreme oUiness of ham or bacon is cor-
rected by the highly nutritive egg (ham and eggs). So also milk and
eggs are cooked with rice, and butter is added to bread, which is de-
ficient in oily matter. In Ireland, where potatoes form the staple of
diet, and there is a deficiency of meat, they attempt a compensation
by mingling with the potatoes boiled cabbage, which is rich in nitro-

402 PHTSIOLOGICAl EFFECTS OF FOOD.

genous matter, with perhaps a little meat, makiag a dish known as hol-
cannon. Rice is also a staple article of food through vast regions. It is
very deficient as a nutriment, containing but little nitrogenous, fatty
or saline matter. It forms an unsubstantial diet, cannot be substituted
for meat and dry vegetables in soldiers' rations — and must always be
combined with nitrogenous principles. Hence, whenever they can be
obtained, mUk, fish and meat are added to it ; and even with the ut-
most procurable quantity of these substances, it is questionable wheth-
er the natives of rice-eatiag countries do not owe much of their lack
of spirit and power to defective diet.

753. Diet required by Children. — We are reminded agam, by refer-
ence to the preceding scale of equivalents, of the iU-adaptation of rice,
sago, arrow-root, corn-starch, &c., as diet for children. MUk, rich in
nutrient matters, is their typical food. They require nitrogenous sub-
stances, for the double purpose of present waste and growth. "When
fed on the substances just mentioned, which lack both nitrogenous and
mineral substances, fat may indeed accumulate, but the frame is weak
and rickety, from small muscles and softness of bones. Children should
have a foil supply of blood-producing food — even bread contains too
little for them — ^milk or flesh should be added. Bat whether fed on
bread and mUk, or meat and bread, there is apt to occur a deficiency
of phosphate of lime, from the rapid formation of bone. But as meat,
eggs and milk contain an excess of phosphoric acid, there being not
enough Hme to convert it all into phosphate, lime itself is a good ad-
dition to the food of young children. It may be given in the form of
lime-water, which the peasants of Germany give to their children with
the best results, while the children greedUy take it, guided by instinct.
— (Geegoet.)

11. The Ye&etaeiak Qitestidn.

754. The points in Controversy. — Strenuous objection to the use of
animal diet has been made by many, and pure vegetable products com-
mended as the best food of man. The controversy has been between
the advocates of a mixed diet, of vegetable and animal substances, on
the one hand, and the partisans of an exclusive vegetable diet, on the
other ; the point of contention being the dietetical fitness of animal
food. The vegetarians, however, as a school, do not entirely proscribe
animal diet. They generally admit the use of eggs, milk, butter, and
cheese, but repudiate flesh. Mr. Geaham recognizes the inconsistency
of this course with the true vegetarian theory, and regards the use of
those substances with disfavor, tolerating them, as it might be, under

THE VEGETAKIAJ!^ QUESTION.

403

protest. The quarrel is an old and embittered one, and has been
made to involve all sorts of considerations. We epitomize and con-
trast belovr, some of the arguments and objections which are most
commonly started in the course of this discussion.

ADVOCATES OF VEGETABLE DIET.

Flesh diet involves the barbarous and
unfeeling practice of destroying sentient
life.

ADVOCATES OF MIXED DIET.

So does the necessary clearance of house-
hold pests, and the insects and vermin in-
jurious to the farm and garden. It is in-
volved in the fundamental older of nature.

In a state of primitive nature, man lived
on vegetable products, fruits, and grains of
the earth.

Whatever may be true concerning the
natural dietetic character of man, there is
neither now on earth, nor has there been
for many centuries, any portion of the hu-
man race, which has lived in all respects
so perfectly in a state of nature, as to af-
ford us an opportunity to study man's true
natural history and dietetic habits. Ana-
tomically, and in strict propriety, man
must be regarded as an extinct species,
that is, he has become so artificial in his
dietetic habits, that they afford no evidence
of his natural dietetic character. Man's al-
imentary organs, if placed before us, afford
no clear and determinate indications of his
true dietetic character — his natural habits
in this respect are wholly unknown, ex-
cept as matter of history and tradition. —
(Stlvestbk Geaham.)

Vegetables afford the pure, first princi-
ples of nature ; while animal products are
drossy, corrupted, second-hand residues,
from which the finer and subtler essences
have been, as it were, exhaled and lost.

If so, it was because he knew no better ;
he is a progressive being, designed to be
civilized, and improve his condition in
numberless ways.

The anatomical structure of man proves
his adaptation to a mixed diet. The her-
bivorous animals are enabled by numerous
and variously-formed teeth to gnaw and
grind, and by a longer digestive canal, and
larger salivary glands, to digest substances
which could not be suflBciently reduced by
the differently structured and sharper teeth
of carnivorous animals, nor dissolved by
their smaller salivary glands, and shorter
intestinal canal. In the structure of man's
stomach and intestines, teeth and jaw-
bones, salivary glands, and muscles of mas-
tication, we find a medium between these
extremes, which points to a compromise in
his diet, and indicates that he was designed
to use both forms of food.

There is no proof of any such difference ;
the foundation of our being is laid in ani*-
mal nutrition ; the infant in the early stages
of its life, is exclusively nourished by its
mother's blood and milk. It is ordered, at
all events, that we shaU not begin our ca-
reer as vegetarians, — ^a pretty distinct prov-
idential hint I

The meat of diseased animals being eaten,
is liable to introduce the same diseases, or
others, into the human system.

Diseased meat is of course unwholesome,
dangerous, and to be rejected; but so are
diseased grains, and damaged flour ; both
are liable to engender disease.

Animal diet excites and inflames the ani-
mal passions and propensities, favoring cru-

Bnt does not the carnivorous animal eat
flesh because it is ferocious, that is, because

404 PHYSIOLOGICAL EFFECTS OP FOOD.

elty and ferocity of disposition, as seen in the Creator has implanted in it the instincts
the carnivora; while vegetable food pro- necessary to its acquirement of the food
duces mildness and docility of disposition for which its organization is destined ; and
(687). that the herb and grain eaters are without

• this savage nature, because they have no

occasion for it, being intended to derive their food from the produce of the soil. But
if we admit that the habitual diet reacts upon, and tends to keep up the respective pro-
pensities of these two classes, still there is nothing in vegetable food that necessarily
induces mildness and docility. The ferocity of wild bulls, boars, bufifalos, &c., is well
known. Our domesticated animals are not in their natural state, an active source of ex-
citement and danger being removed, in the general mutilation of the males. " We can-
not see the least ground for the conviction, that a man, in good average health, with no
plethoric excitability, will be in the least changed for the better by relinquishing his slice
of mutton and potatoes for its equivalent in wheat-flour, or an omelet and custard-pud-
ding. And if the effect of universal vegetarianism were to be, to reduce the character
of all mankind to the insipidity of said omelet, and the blandness of custard-pudding,
we, for our part, should not like the world half so well as we do now. A very excellent
lady, who had kept a school for nearly half a century, said — ' I never liked the girls who
were brought to me with " very good characters " from their parents ; they had either
no energy, or were very sly ; give me the naughty children ; there is something in them
to work upon, and a promise of future activity.' The emotions and propensities are the
sources of all action, and if these be tamed down to the vegetarian standard, we appre-
hend that, neither will the better parts of human nature be called into energetic opera-
tion by their own activity ; nor will the worse call forth that energy for their repression,
which is often the foundation of what is noblest in human character." — (Dr. Caepentee.)

Into the general question, as thus opened, we do not propose to en-
ter ; but simply to call attention to a few chemical and physiological
facts, which appear to have been established, and which may enable us,
perhaps, better to comprehend the present conditions, and more strict-
ly scientific aspects of the subject.

755. Restricted Scope of Animal Transformations. — We recall at this
point the statement repeatedly made, that the animal system is not to
be viewed as capable of creating or fabricating the compound sub-
stances which it employs in nutrition. Recent organic chemistry
has profoundly modified the older views of this matter. In the ab-
sence of all accurate information, the animal system was looked upon
as endowed with unlimited and mysterious powers of transforma-
tion; but we now understand that those powers are definite, and
limited within a narrow range. It is not strange that, in the absence
of exact knowledge, but little could be discovered in common between
herbage and dried leaves of grass consumed by an ox, and the blood
and texture of its body. But chemistry teaches us now that the very
identical material of blood and tissue is prepared in the vegetable, and
that the office of the animal is chiefly limited to extracting and col-
lecting it from its multifarious vegetable food ; it can only appropri-
ate pre-existing compounds.

THE VEGETAEIAN QUESTION'. 405

756. Vegetable aud Aaimal Principles tlie same. — We have further seen
that there is a remarkable identity of alimentary principles, whether
derived from plants or animals. Vegetable and animal fats have the
same substantial composition — are alike divisible into liquid and solid
parts, with similar properties. And so the nitrogenous principles,
vegetable and animal, are remarkable for their chemical similarity —
in composition, the proportion of their elements, external properties,
and modes and products of decomposition, vegetable albumen resem-
bles animal albumen, and the same with casein and fibrin. The veg-
etable principles, by simple digestive solution, are converted into blood
and flesh, without decomposition, just as mineral substances may bo
dissolved and separated, again and again, without affecting their chem-
ical integrity or essential properties. Whether we go to the vegetable
or animal world, therefore, we get the same nutritive principles, and
we arrive at this twofold conclusion : that, while we may procure
every thing adequate to complete and healthful sustenance from the
vegetable kingdom, where it is all first fabricated ; on the other hand,
we find substantially the same principles in the animal world, with
only modifications of form, concentration, and solubility. It would
seem from this point of view, that we may confine ourselves without
detriment to the former source of aliment, or resort without injury to
the latter.

757. Peculiar inflnence of Flesli Diet. — Yet there are important dif-
ferences between vegetable and animal food ; in what do they con-
sist? LiEBiG observes, "Bread and flesh, or vegetable and animal
food act in the same way with reference to those functions, which are
common to man and animals ; they form in the living body the same
products. Bread contains in its composition, in the form of vegetable
albumen and vegetable fibrin, two of the chief constituents of flesh,
and in its incombustible constituents, the salts, which are indispensa-
ble for blood-making, of the same quality and in the same proportion
as flesh. But flesh contains, besides these, a number of substances
which are entirely wanting in vegetable food ; and on these peculiar
constituents of flesh depend certain effects by which it is essentially
distinguished." Reference is here made to the peculiar constituents
of flesh-juice which have been mentioned (471). Flesh is thus a com-
plex product, containing peculiar principles, — a result of all the diges-
tive and preparative actions of an animal organism ; and as the
purpose of food is to re-produce flesh, it is evident that no dietetical
preparation can effect this so perfectly, so rapidly, or with so little
physiological labor as meat itself. Flesh is nearest to blood, and flesh

406 PHYSIOLOGICAL EFFECTS OF FOOD.

of all aliments is most easily converted into both. The ingestion
of flesh augments the proportion of fibrin in the blood, and increases
the activity of nutrition. The heart being a tissue of muscular fibres,
is more fully nourished ; the activity of the circulation is consequently
increased. The excitation of this activity, observed after a copious
meal of venison, is due not only to the abundance of albuminous mat-
ters contained in the venison, but also, probably, to its proportion-
ately large quantity of kreatin. Highly animalized diet exalts
the density and solid constituents of the blood, and increases the
number of its corpuscles or globules; but does not augment the
proportion of its albumen. This re'enforcement of the blood by con-
sumption of flesh, in heightening the general power of the system, of
course, strengthens the passions and propensities. Por this reason the
terra stimulating has been applied to flesh-diet. From its greater
concentration, it is easier to over-eat with animal than with vegetable
diet. As excessive alimentation is a universal danger, the vegetarian
is most protected, though by no means safe ; for it is very easy to
slide into excess upon a vegetable regimen, especially if eggs, milk,
butter, and cheese be freely used, as is very apt to be the case.*

T58, Mineral Matters RepIaceaMe in the two Diets. — But while vegetable
and animal food yield precisely the same organic principles to the blood,
they do not furnish to it identical mineral constituents, as was stated
before. The phosphoric acid which appears in the blood in com-
bination with the alkalies forming phosphates^ when animal food is
consumed, is replaced by carbonic acid, and the carloivxtes when, we
change to a diet of vegetables, and fruits. Bread gives rise to phos-
phoric acid like flesh. We called attention to this most extraordinary
fact — that a powerful, flxed, mineral acid, and a feeble, volatile, or-

* " The influence of diet over muscular fibre, is an inoiportant social question ; for thews
and sinews have always ruled the world, in peace and in war, in a proportion quite equal
to brains. Indeed, it is a question which the present writer is disposed to answer in the
affirmative, whether naUonally muscular and mental energy do not always run in couples
and whether the first is not the cause of the second. It does not appear that any diet, so
there be plenty of it, is incapable of fitting a man to get through his daily work in a
fasTiion; but the best specimens of the species in their several sorts, hunters, agricul-
turists, or citizens, are those nations who get most flesh-meat. A collateral advantage
of a meat diet to a nation is the difSculty of obtaining it ; for the truth, probably, is that
the mode of procuring food has as great an influence over mind, manners, and muscles, as
the nature of the food itself He that is satisfied with what he can pick up, ready grown,
degenerates either into a starved New Hollander, where food is deficient, or into an
effeminate creature like the old inhabitants of the "West Indies, where it is abundant ;
while a civilized people with ' a care for their meat and diet,' will have thought about it,
labored for it steadily, advanced science, and ransacked nature, to improve it, and ob-
tained their reward in the search itself "—(Dr. Cuambeks).

THE VEGETARIAN QUESTION. 407

ganic acid, deport themselves alike, and produce exactly the same
effects, in that most delicate and changeable of all chemical prepara-
tions— the blood of the living body. We can hardly suppose that
these widely dissimilar substances would have been made so perfectly
interchangeable under these circumstances, except to provide for the
possibility of a mixed and variable diet.

759. Indications from the Saliva. — Attention has been called to the
saliva, as affording a possible test of the kind of food adapted to different
animals. Human saliva is much more powerful in its action than that
of carnivorous animals, as the dog. This evidently points to a diet
abounding in starch as proper for man, whUe the contrary is clearly
indicated in reference to the dog.

760. Relative Economy of Vegetable and Animal Diet. — If the question
present itself as one of economy on the largest scale, that is, under
which diet the greatest number of human beings can be sustained on
a given area, we must decide at once in favor of the vegetarian policy.
AU animals are organisms for the destruction of nutritive matter.
When an animal is slaughtered, it affords a mass of nutritive material ;
but it is only a residue, — a small remaining part after life-long waste and
destruction of food. The body of the ox represents, perhaps, thou-
sands of bushels of grains and roots which it has consumed. If we ob-
tained from him force, in the shape of work done, the loss was not
total ; otherwise, a few hundred weights of beef is our sole equivalent
for the destruction of many tons of vegetable food. The amount of
nutritive material procurable upon a given surface of the earth, is de-
finite and limited, and the inferior animals are machines for its de-
struction ; in consuming them, we take what happens to remain, and
besides the previous necessary loss, the nutriment we get comes in
the worst possible shape in point of economy (74^. If grains, legu-
minous seeds, fruits, and roots, are cultivated — nutriments adapted to
the sustenance of men ; and the lower animals be dispensed with, the
conditions are provided for the largest human population. The great
superiority of agricultural communities in numbers and power, over
the hunting and flesh-consuming races, is thus obvious. The case
was pithily put by a North American Chief, who, according to the
French traveller Oeeviooue, addressed his tribe as follows : " Do you
not see the whites living upon seeds, while we eat flesh 7 That the
flesh requires more than thirty moons to grow up, and is then often
scarce ? That each of the wonderful seeds they sow in the earth,
returns them a hundred fold ? That the flesh on which we subsist has
four legs to escape from us, while we can use but two to pursue and

408 PHYSIOLOGICAL EFFECTS OF FOOD.

capture it ? That the grains remain where the whites bow them, and
grow ? That winter, which with us is the time for laborious hunting,
to them is a period of rest? For these reasons have they so many
children and live longer than we do. I say, therefore, unto every one
that wUl hear me, that before the cedars of our village shall have died
down with age, and the maple trees of the valley shall have ceased to
give us sugar, the race of the little corn-sowers, will have extermi-
nated the race of flesh-eaters, provided their huntsmen do not them-
selves become sowers."

761, Diversities of Diet among different Nations. — The adaptability of
the human constitution to widely different dietetic conditions, is re-
markable. We find among the races distributed over the globe, the
pure vegetarians, — some subsisting upon soft fruits, others upon hard
grains, others upon succulent herbage, and others again upon tough
fibrous roots. On the other hand, there are the exclusive animal
feeders, some consuming flesh, others fish, others fowl, and others
even insects ; — some devour their food raw, others cook it ; some take
it as soon as it has ceased to live, and others wait till it turns putres-
cent. Thus the diet of one locality would become loathsome and fatal
in another. It has been aflBrmed that this dietetic pliancy of man,
by which he is enabled to live upon the most strangely diverse forms
of aliment, is a wise providential design to secure the diffusion of the
human race, and the most extended occupancy of the earth. But
though this be admitted, it brings us no nearer to a settlement of the
question, " What form of diet is best suited to the full and harmonious
and highest development of man's nature ? " that is one of the large
and serious problems to which science will address itself in the
fature.

12, OONSIDEEATIONS OF DlET.

762, We conclude the subject of the physiological action of foods
with some general and practical suggestions concerning diet, partly in
recapitulation and partly supplemental.

763, The demand for Food variable. — By recalling the purposes to
which food is applied, we perceive how changeable must be the de-
mand for it. It is the source of power, and therefore, with the alter-
nations of exercise and rest, its requirement rises and falls. It is the
source of warmth, and therefore the quantity we need must vary with
our protection from cold. Any cooling of the body increases the
appetite, and compels us to eat more than usual. Again, the necessity
for food is complicated with the conditions of breathing. The waste

CONSIDEEATIONS OF DIEr. 409

of matter in the body stands in close relation to the oxygen it con-
sumes, and this varies with capacity of the lungs, atmospheric purity
and density, and therefore influences the quantity of food necessary to
restore the hodUy loss. A Manchester manufacturer ventilated his
weaving mill, when forthwith the appetites of the operatives were
sharpened, and as their wages would just support them, they made
formal complaint of the change, and demanded an advance of com-
pensation. Thus the multiplex and ever- varying conditions of tem-
perature, air, and exercise, joined with the diverse influences of age,
sex, constitution, temperament, and habit, conspire to determine the
necessity for food in each special case.

Y64. Dhersities in Digestion and Diet. — There are also wide differ-
ences among different persons in point of ability to digest and assim-
ilate food. We meet with one class — types of robust health, with
sound, vigorous systems, accustomed to much exercise in the open air,
and who take aU kinds of food, caring only that there shall be enough.
They never suffer the slightest inconvenience from what they eat, and
seem indeed to be unconscious of having any stomach or visceral
organs. All discriminations among aliments, as digestible and indi-
gestible, with suggestions and precautions concerning diet, fall upon
the ears of such as without signification. On the other hand, we
behold the dismal group of dyspeptics, horribly conscious of their
digestive arrangements, and to whom the whole world of aliment is
turned into a perennial fountain of misery. Between these two ex-
tremes there are aU degrees of digestive power and gastric suscepti-
bility. Again we notice great diversities in plans of diet among those
with healthy digestions. This state of things makes difficulty in
fixing upon terms to describe different sorts of diet. Low diet, for ex-
ample, is applied to a combination of food that yields less blood and
strength than usual, while a Thigh or generous diet tends to produce a
contrary effect. But it is obvious that a diet which would be, to aU
intents and purposes, low and spare^ to a hearty meat-eater, might be
MgTi and generous to a strict vegetarian. To be able, therefore, to
pronounce any particular diet abstemious or full, we must understand
the preceding dietetic habits.

V65. Daily reqniremeut of Food — ^These facts make it apparent, that
an rules of diet are necessarily so general as to be of little service,
until modified to suit the peculiar cu'cumstances of each individual.
Instead of blindly submitting ourselves to any scheme of dietetic
directions, we should exercise an independent judgment, studying
carefully our own constitutional peculiarities, analyzing our conditions,
18

410 PHYSIOLOGICAIi EFFECTS OP FOOD.

and freely revising all rules before reducing them to personal practice.
We cannot fix the precise quantity of food required to be consumed.
Where men are dealt with systematically in large numbers, as the
inmates of hospitals, soldiers, «&;c., it becomes necessary to establish
diet scales, that is, to apportion to each person his due allowance of
food by weight and measure. The following is the diet scale of the
U. S. Favy : Three days in the weeTc ; — ^pork, 16 oz.; beans or peas,
7 oz. ; biscuit, 14 oz. ; pickles or cranberries, 1 oz. ; sugar, 2 oz. ; tea,
\ oz. ;=40| oz. Two days in the weeTc; — ^beef, 16 oz.; flour, 8 oz. ;
dried fruit, 4 oz. ; biscuit, 14 oz. ; tea and sugar, 2i oz, ; pickles or
cranberries, 1 oz. ;=45|- oz. Two days in the weeJo; — beef, 16 oz. ;
rice, 8 oz. ; butter, 2 oz. ; cheese, 2 oz. ; biscuit, 14 oz. ; tea and
sugar, 2| oz. ; pickles or cranberries, 1 oz.=45j oz. These numbers
are valuable as near expressions of the wants of large bodies of men,
under given circumstances ; but they are of small service as dietetical
guides to individuals.

766. Regulating the AppetitCt — We are left, therefore, in this matter
entirely to individual discretion. Nature's guide is the appetite, but
we must be cautious not to misinterpret its indications. In what
hunger exactly consists we cannot tell. But the feeling seems to
depend less upon the immediate state of the stomach (in respect of
fulness or emptiness), than upon conditions of the general system.
Hence the swallowing of food, although an immediate relief of hunger,
does not at once extinguish the appetite. If therefore we eat slowly,
prolonging the meal with deliberate and thorough mastication (634),
time is given for the system to become conscious, as it were, of the
progress of the supply, while the sense of quiescent satisfaction indi-
cates that BuflBcient food has been taken, and that we should cease
eating. If, on the other hand, we neglect these monitions, bolting the
alimentary mass, and driving on to repletion, we incur the double
evQ of over-eating, and of taking our food in a crude, half-prepared
state. To obtain that command of appetite which shall enable us to
abstain before we reach satiety, is every way most desirable, both as
a means of preserving health, and of regaining it when lost.

767. Frequency and times of Eating. — Systematic recurrence is the
order of nature, observed every where, alike in the timing of melo-
dious sounds, the rhythmic beats of the heart, the measured respirations,
the coming and going of light, the ocean's ebb and flow, seasonal revo-
lutions and planetary periodicities. The arrangement of regular times
for meals, harmonizes, therefore, with the universal policy of nature,
and is, moreover, of the highest social convenience. Yet it is impos-

CONSIDERATIONS OF DIET. 411

sible to subject all to the same regulations of time. Dr. Combe re-
marks : " The grand rule in fixing the number and periods of our
meals is, to proportion them to the real wants of the system, as modi-
fied by age, sex, health, and manner of life, and as indicated by the
true returns of appetite." As the blood is usually most impoverished
after the eight or ten hours' fast of the night, breakfast should be
early (768). The stomach is usually vacated of its nutritive contents
in about four hours after eating, but it may be an hour or two later
before the blood begins to call upon it for a renewed supply. Persons
engaged in active labor, in which bodily expenditure is rapid, of course
require to eat more often than the indolent and the sedentary ; and
children need nourishment oftener than adults. But too long absti-
nence, especially if the digestive power be not strong, sharpens the
appetite, so that there arises danger of excessive eating. Some avoid
luncheon for fear of 'spoiling the dinner,' whereas the thing they
most need is to have it spoiled. "Where the intervals between the
meals are so long as to produce pressing hunger, something should be
taken between them to stay the appetite and prevent over-eating.
Late and hearty suppers are to be reprobated. Active digestion and
sleep mutually disturb each other, as at night the exhalation of car-
bonic acid is slowest, and tissue changes most retarded, the overloaded
blood is not reheved, and invades the repose of the brain, producing
heavy, disordered dreams, and nightmare, followed by headache and
ill-humor in the morning. Still there is the opposite extreme, of sit-
ting up late, and going to bed wearied, hungry, and with an ' inde-
finable sense of sinking,' followed by restless, unrefreshing sleep. A
little light nourishment in such cases, may prevent these unpleasant
eflfects. Custom has fixed the daily number of meals at from three to
five ; probably three is the smallest number that consists with weU-
sustaiued vigor of the system ; four or five may be unobjectionable,
the amount of nom-ishment taken each time being less. The essential
thing is, regularity in each case, in order that the digestive glands may
have time to prepare their secretions (641).

768. Rest before Meals. — We should not take our meals when tired
out, or much fatigued. The stomach participates with the other parts
of the system in the exhaustion, and is thus unfitted for the perform-
ance of its proper and active duties. If there has been severe exer-
cise, either of body or mind, a short interval should be allowed for
repose, or half an hour may be appropriated to any light occupation,
such as dressing, before sitting down to dinner. It is questionable if
much exercise before breakfast be generally proper. When we rise in

412 PHYSIOLOGICAL EFFECTS OF FOOD.

the morning, tlie system has passed the longest interval withont food,
and is at the lowest dinrnal point of weakness from want of nourish-
ment. It is well understood that the body is more susceptible to
the morbid influence of colds, miasms, and all noxious agencies, in the
morning before eatiag, than at any other time ; and those exposed to
the open air before getting any thing to eat, in aguish regions, are in-
finitely more liable to be affected than those who have been fortified
by a comfortable breakfast. Cases may be quoted, undoubtedly, in
which early exercise has produced no injurious results — perhaps even
the contrary. Yet ia most instances, especially if tiiQ constitution be
not strong, breakfast should follow shortly after rising and dressing,
before serious tasks are attempted. Dr. Combe justly observes, that
in " boarding schools for the young and growing, who require plenty
of sustenance, and are often obliged to rise early, an early breakfast is
almost an indispensable condition of health."

Y69. State of Mind dnring Meals. — We have before seen how mental
and passional excitement disturb appetite and digestion (685). The
brain and stomach are profoundly sympathetic. Morbid states of the
stomach often so disturb the brain as to throw a pall of gloom over
the mind, or destroy its equanimity, as we often see in dyspeptics,
while any mental tension or discord interrupts the gastric fimctions.
Food has been rejected from the stomach, unaltered, several hours
after it was taken, under the dread of an impending surgical opera-
tion. During meals, therefore, every thing like intense mental exercise
should be avoided, yet the mind ought to be lightly occupied, as in
cheerful, exhilarating conversation upon passing topics. A flow of
sprightly or sportive talk, that may agreeably engage the attention,
and thus protract the meal, is not only most pleasant at table, but is
of solid physiological service. This explains an observation of Dr.
Chambers. "It is very common to hear bachelors complain that when
they dine in company, their dinner gives them no trouble ; they swal-
low all sorts of imprudent food, and feel no more of it, while a soli-
tary meal at their club, on the plainest meat, is digested with difB-
culty and pain."

Y70. Exercise after Meals. — "When any portion of the body is strongly
exercised, the whole system is taxed to sustain it. There is an unu-
sual determination of blood to the excited part, with, of course, a cor-
responding deficiency in other parts. The case of the two dogs is well
known, both of which had taken a hearty meal, one being then left at
rest and the other put upon the chase. After a short time they were
both killed, when digestion was found far advanced in the one at rest,

CONSIDEEATIONS OP DIET. 413

while it was not even begun in the other. The vital force reqnired to
promote digestion was diverted entirely to the muscular and nervous
systems. There is some conflict of opinion as respects the propriety
of exercise after a hearty meal, such as dinner. Dr. Beaixmont says,
" From numerous trials, I am persuaded that moderate exercise con-
duces considerably to healthy and rapid digestion. The discovery was
the result of accident, and contrary to preconceived opinions," Dr.
Combe, on the other hand, observes " that active exercise immediately
after a fall meal, such as is generally taken for dinner, is prejudicial to
its digestion, seems to be proved by daily and unequivocal experi-
ence." "We conclude that physiological indications, the widest expe-
rience, and the analogies of nature, concur to suggest rest for a time,
or very gentle exercise, as most advisable.* There is clearly a de-
pression of the general functions of the body, with a tendency to slug-
gishness and repose. Inclination to rest after eating, seems to be a uni-
versal instinct of the animal kingdom. To those who are drowsy and

* "Reading has been too much overlooked of late as a bodily exercise, and the benefit
has been doubted, because of the awkward manner in which it is done. Look at a
Greek or Eoman representation of a man speaking or reading ; he is standing up, or sit-
ting back with the chest thrown well forward and dilated, the nostrils open, and the
shoulders flatter and more erect than when walking. The artist's model evidently has
the lungs filled with air, and the diaphragm at rest, so that fall play is given to the elas-
tic cartilages of the ribs. The man is rolling out his words really dare, as Celstis has
it, comfortably to himself, and agreeably to his hearers. Observe as a contrast many a
modern reader or orator ; his constrained attitude recalls rather the architectural incon-
gruities of Gothic art, expressing, perhaps, the earnestness and self-denial which that
style may be held to indicate, but certainlynot wholesome ease. The head is bent for-
ward, a stiff neck-cloth compresses the windpipe, the lungs are emptied, and the words
are squeezed out by an effort of the diaphragm and abdominal muscles, which makes the
listener fancy he can almost hear them creak with the strain. They are used at an enor-
mous mechanical disadvantage, and the nervous energy of the whole trunk is foolishly
exhausted. Hence, reading and preaching, instead of being a relief to gastric derange-
ment, are nowadays found actually to produce it. The clergyman's sore throat and
dyspepsia have often been traced to their professional work, and that which might have
been a cure has become an aggravation. There was, some years ago, a quack in the Isle
of Wight, who used to treat clergymen very successfully, under a promise of secrecy.
His method was simply to teach them to keep the chest inflated, by breathing in only
through the nose, and to allow it to empty itself by the elasticity of the cartilages as the
patient spoke. This plan entails the habit of straightening the windpipe, sitting or
standing upright, and throwing the shoulders back ; in fact, of assuming tho attitude
which I have described as a model for the reader, and is for that reason found practically
beneficial. If patients can sing, they possess a part of the Materia Medica very valuable
to their digestion. They will seldom require the hints above given, for most leading
masters have found the necessity for teaching their pupils a rational attitude, and the or-
dinary time for exercising the art is the hour after the meal that most requires attention.
It is striking how rarely powerful singers suffer from gastric derangement."— (Db. Cham-

BEBS.)

414 PHTSIOLOGICAL EFFECTS OP FOOD.

inclined to take their siesta, or after-dinner nap, we may suggest that
it is better to sleep upright in a chair than to repose on a sofa or bed.
In the former position the sleep is generally short, and never very pro-
found ; but when the whole body is recumbent and the stomach full,
the sleep is heavy, prolonged, and unrefreshing.

771. Effects of ExcessiYO Eating. — The consequences of uncontrolled
indulgence of the appetite manifest themselves variously. The imme-
diate result of over-eating is lethargy, heaviness, and tendency to
sleep. The effect of persisting in the habit will depend upon numer-
ous circumstances. In a healthy system, with good digestion and
much active out-of-door exercise, bad results may not foUow from the
freest use of plain food. In other conditions the burden may fall upon
the overworked digestive organs, which are irritated by the presence
of the excess of food which they cannot appropriate. If digestion be
strong, an excess of nutriment may be projected into the blood, over-
loading the circulation. If food is not expended in force, the natural
alternative is its accumulation in the system, increasing the volume of
muscle and tissue, and swelling the deposit of fat. Degeneracy of the
structures, mal-assimilation of nutritive material, increased proneness
to derangement and diseased action, and various unhealthy conditions,
may be induced by the habitual employment of too much food. It is
either transmuted into fat and flesh, or into pain and disease. Yet it
is very common to charge upon quantity the evils that flow from qual-
ity in diet. Injury may spring from hearty indulgence in a rich, con-
centrated, and various diet, which would not flow from the most lib-
eral use of plain and simple food. ' Dine upon one dish, and in that
consult your taste,' is an excellent motto.

772. Effects of Insufficient Nutrition. — The blood is the stock of ma-
terial on hand, from which the supplies of the constantly wastmg sys-
tem are withdrawn, and this stock is but small. It contains dissolved
only about one-eighth of the dry matter of the body, so that the
strength can be sustained only a very short time without external sup-
plies. Yet when food is withheld, life holds its ground against exten-
sive changes. An animal does not die of starvation tiU it has lost two-
fifths of its weight and more than a third of its heat. Yet, so impor-
tant is the prompt and regular ingestion of aliment, to keep the sys-
tem up to the par of its activity, that even transient interruptions pro-
duce serious disturbance. As the demand for nourishment is the prime
necessity of our being, taking precedence of all other needs, if the
supply be suspended, the clamors of the system for food rise at once
above all other wants. Until hunger is appeased, there is disquiet ; the

CONSIDEEATIONS OF DIET. 415

mind traverses witli less than its usual freedom, the temper is more
easily started, and sleep fails to invigorate as usual. There was shrewd,
practical wisdom in the warntag of Cardinal Db Eetz to politicians,
never to risk an important motion before a popular assemblage, how-
ever proper or wise it might be, just before dinner. Of the effects of
insuflficient food Moleshott speaks as follows : " There is another in-
stinct by which the vigor of the mind is vanquished in a more melan-
choly way. Hunger desolates head and heart. Though the craving
fOx nutriment may be lessened to a surprising degree during mental
exertion, there exists nothing more hostile to the cheerfulness of an
active, thoughtful mind, than the deprivation of hquid and solid food.
To the starving man every pressure becomes an intolerable burden ;
for this reason, hunger has effected more revolutions than the ambition
of disaffected subjects. It is not, then, the dictate of cupidity or the
claim of idleness which prompts the belief in a natural human right
to work and food."

Y73. Diet and the Capacity of Exertion. — There are evils also in the
opposite extreme of a too restricted diet. Our strength and power of
accomphshment is derived from the food we consume, and for high
and sustained effort there is required a strong and generous diet. We
cannot have something for nothing. Large exertion, physical or men-
tal, involves active physiological change, and hearty eating, to sustain it.
The distinguished and discriminating President of one of our largest
coUegiate institutions remai'ked to us, that many students required to
be encouraged to freer living. Urged to economy by limited resom-ces
and misled by the partial views of those who recommend low, abste-
mious diet as favorable to clearness of thought, they adopted a scale
of nutriment insufficient to sustain the powers of nature in vigorous
and protracted exercise. Existence can undoubtedly be maintained on
a very small amount of food, but we are not concerned to know what
that minimum of nourishment may be, as bare, inert, passive existence
is no object. Life is of but little value except in its purposes, and man
is only a man in his capability of executing them. Coenaeo, the Ve-
netian, the Prince of ascetic heroes, lived to a great age on 12 oz. of
food, chiefly vegetable, per day, and 14 oz. of light wine. But he
passed "a sort of vegetable life in his palace and gondola," without
stress or buffet, while a mere lawsuit is said to have carried off two
of his brothers who attempted the same style of living. " Dr. Staek,
of London, tried similar experiments, and got on pretty well so long
as he had nothing to do besides weighing himself, but when he came
to imdergo a contested election for St. George's Hospital, it killed him

416 PHYSIOLOGICAL EFFECTS OF FOOD.

outright. If the hody is to he exposed, as it is in all modern civil-
ized life, to sudden extraordinary demands, it must he prepared for
them by heing hahituated to take in rather more than is ordinarily re-
quired."— (Dr. Chambees.) It is charged upon the Americans that they
are enormous feeders ; probably they eat too much ; but where else
upon the globe is there such general activity, bodily and mental ?

774. Order and Variety in Diet. — Our nature was made for variety.
The differences of complexion, cast of countenance, expression and
figure constantly presented to us in the human form, are infinite. The
objects about us are endlessly and namelessly diversified, always har-
monious, yet ever changing into new relations. We gather from this,
that in habits and experience, man is not designed to be the slave of a
mechanical routine, nor to fall into tame and spiritless repetition. Of
all the systematic degradations to which he is subject, the lowest is
that of the soldier, who has taken formal leave of his independent
manhood, who starts at the tap of the drum, belongs somewhere in a
row, and lives only to be drilled and messed at the arbitrary dicta-
tion of his superiors. In nature, we behold inflexible order working
out eternal variation ; and so in life, methodized habits should give
rise to never-ceasing diversities. As respects diet, the materials pre-
pared for us, although marvellously simple in composition and adapta-
tion to our needs, are wonderfully various in form and gustatory
properties. We have the widest and freest choice of means to ac-
complish the same physiological end. Nature thus solicits us to
enjoy the bounty of her resourses, which we should wisely do, not tempt-
ing the appetite with a parade of culinary enticements, but restricting
the dishes at each meal, and agreeably varyiog them at successive
times of eating.— Prof. Moleshott, after insisting that aU food partakes
somewhat of the nature of a stimulant, has the following observations :
— "And as the uniformity of the stimulant, even if repeated at longer
intervals, is prejudical to its effects ; a regular arrangement of dishes,
repeated certain days every week, is a custom not to be commended.
If a stiff regularity only too clearly betrays a commonplace narrowness
of mind, such a regular repetition becomes a source of petty for-
malism, insensibly, but aU the more dangerously, repressing the free
movements of the mind. Whoever has watched himself with atten-
tion, will often enough have experienced how the refreshing and
Btimulating effect of a walk is evidently lost if taken for a long time
daily at the same hour. It is the same with uniformity in meals ;
and while the ancient physicians used actually to assert it to be useful
sometimes to throw the body out of order, in accordance with this

CONSIDERATIONS OF DIET. 417

doctrine, it is perfectly true that an inflexible regularity of life is by
no means compatible with a genial freedom."

775. Diet and Corpulence. — The undue accumulation of fat is pro-
moted by many causes. Privation of active exercise, too much in-
dulgence in sleep, indolent, sedentary habits, and want of thought,
favor obesity; — restless animals and industrious men are seldom
inconveniently fat. The free use of an oily, starchy, or sugary diet,
dispose to fattening, as also alcoholic liquors and the absorption of
watery fluids, either by much drinking, frequent warm baths, or even
breathing damp air. It is also frequently caused by defective diges-
tion. There may be want of gastric power to manage the nitro-
genous matters, the muscular fibre escaping from the stomach half
dissolved. As a moderate diet thus proves Insufiicient, it is instinc-
tively increased, and fatty bodies being more easUy assimilated than
the albuminous, a surplus of it is lodged in the system. The excessive
increase of fat must be regarded as a disease, and often involves the
constitution in much disorder. In the truly healthy organization,
there is a perfect correspondence in capacity and power, between the
circulation through the lungs and that of the general system (283);
but where the fat deposit becomes largely increased, the extension of
the minute blood-vessels to maintain the extra nutrition, destroys the
equilibrium ; the lung circulation is inadequate to its full duty, the
carbonic acid is not perfectly excreted, the blood becomes venous, the
circulation is retarded, producing congestion, with frequent dilatations
and degenerations of the heart. The diet best fitted for corpulency,
is that containing the least oil, starch, or sugar. Very hght meals
should be taken at times most favorable to rapid digestion, and should
consist of substances easy of solution and assimilation. The time of
meals should be fixed at an early hour in the day, before exertion has
rendered the powers of the alimentary canal languid. Breakfast
should consist of dry toast, or stUl better, of sea-biscuit, and if much
active exercise is intended, a piece of lean meat. Dinner at one, on
ineat with the fat cut off, stale bread or biscuit, and some plain boiled
macaroni or biscuit pudding by way of a second course. — (Dr. Cham-
bees.) Lean meat is a good diet for the aspirant after leanness ; —
carnivorous animals are never corpulent. In connection with proper
diet, vigorous and systematic exercise is essential. Sometimes there is
an accumulation of fat, where the amount of aliment taken is less than
natural. Such cases are difficult to remedy by exercise, as the
quantity of food taken is too small to sustain muscular strength.

776. Diet of Infancy. — We have stated that nature prescribes the

18*

418 PHYSIOLOGICAL EFFECTS OF FOOD.

infant's diet in the composition of its mother's mUk ; but nature is
sometimes defeated in her intention, as the mother's diet controls the
milk-secretion both in quantity and quality. If her food be scanty, or
low and light, the infant wiU be imperfectly nourished. The lactic
secretion requires to contain its due proportion of casein, sugar, oil,
and phosphate of lime; and to produce these copiously, a varied
nutritious diet of good bread, meat, mUk, eggs, and potatoes, is re-
quired. The aliment which the mother furnishes to her child is more
richly nutritive than that which she retains for her own nourishment.
She should avoid indigestible substances, and especially take but
little vinegar or acid fruits, as these both diminish the amount of mUk
and render what there is less nutritious. The nursing mother may
with great advantage make free use of milk itself, as it furnishes, ready
formed, the substances she is required to impart. Should there be
tendency to acidity, it may be corrected by mixing the mUk with a
mild alkali, such as one-fourth or one-fifth of its bulk of soda water.
It becomes often necessary that children should be surrendered to toet
nurses. As the composition and consequent physiological effects of
milk gradually change in the successive months after the child's birth,
it is important that the ages of the children, both of the mother and
wet-nurse, should be as nearly as possible the same. That nature,
temper, and character are communicated by her milk, from the
mother to the nursing child, is not an idle prejudice. Not only do
bodily circumstances of health affect the lactic secretion, but con-
ditions of the mind and passions also. A paroxysm of anger may
pervert and even poison the fountain of life ; " and there is no thought
more natural, than that on the breast of its mother the infant may
imbibe together with its milk, her nobleness of mind." "When the
exigency occurs, therefore, the selection of wet-nurses is a matter of
much importance. If they have been accustomed to plain, substantial
diet, it is highly unwise to pamper them with delicacies, as is some-
times done in affluent families, indigestion and bad bodily conditions
being very liable to ensue. As respects the use of spirits under these
circumstances, Dr. Chambers, himself no advocate of abstinence, has
the following remarks. " Nursing women are desired to drink an un-
usual quantity of porter, wine, bitters, and what not, till they get
bloated, thick-complexioned, stupid, and dyspeptic. The reason of
this is, that alcohol and other ingredients, in such a diet, arrest meta-
morphosis, detain in the system the secretions we want to flow out,
and fill those which do flow out with effete matter. If the con-
stitution of the mother is robust enough to stand this bad usage,

CONSIDEEATIONS OP DIET. 419

and still afford the due quantum of milk for her chUd, yet that
must be of inferior quality to what she otherwise would have
made, and the innocent consumer suffers." The milk of the cow
differs so considerably from that of the mother, that it should be
corrected if it is to be given to the infant. This is done by adding
a third or a fourth of water, and about l"25th its weight of refined
sugar; it should be warmed to the temperature of the body, 98°.
To this, solid substances may be gradually added, as wheaten bread
or boiled farina (445), but not arrowroot, tapioca, sago, or rice,
upon which many children are fed to death. These are not complete
nutriments, and are incapable of promoting the growth of either bones
or flesh (746). Even after weaning, soft mixtures of good bread
with milk and sugar, or with the juices of meat ; also the more
readily digestible roots and vegetables, together with soups prepared
from the meat of young animals, may be considered the best food.
After the teeth are cut, meat and bread in their simple form may also
be given. Aliments difficult of digestion, fat meat, heavy bread, rich
pastry, unripe fruit, leguminous seeds, and heating condiments are
carefully to be avoided for children.

777. Diet of Childhood and Youth. — Besides the maintenance of ac-
tivity, the diet of this period must be such as to harden, strengthen,
and expand the system. The muscles increase in fibrin and firmness,
tissues are developed and strengthened, and the gelatinous model of the
bones is solidified and enlarged into a strong skeleton by the gradual
deposit of bone-earth. With these changes there is also a slowly aug-
menting activity of bodily transformation, the excretion of carbonic
acid by the lungs, and of urea by the kidneys, increasing in amount
up to the twenty-fifth or thirtieth year. The demand for food is
therefore more peremptory during the growing time of youth than
at any portion of subsequent life. As regards the indulgence of the
appetite at this period, perhaps there is no better guide than the indi-
cations of nature. So children have plain food, if healthy and active,
they will hardly eat sufficient to injure themselves. It is not right to
subject the young to a regimen adjusted to the adult ; they require
more nutritious food, and to satisfy the appetite oftener. Something
to eat in mid-forenoon and mid-afternoon will often be necessary, but
the thing should be done strictly upon system, as the habit of eating
irregularly, at every capricious call of appetite, is wrong and injurious.
Yet, though the diet of youth should be nutritive and strength-
imparting, it is of the first necessity that it should be plain and unex-
citing. Luxurious stimtiating food, charged with condiments and

420 PHYSIOLOGICAL EFFECTS OF FOOD.

nerve-provocatives, gives rise to a morbid precocity of instincts,
thoughts and actions, and helps to explain the unhealthy prematurity,
the slender figures and pale faces of boys and girls brought up in
towns.

778. Diet of Middle Life. — "When maturity has been reached, there
comes a period, varying in duration, but extending perhaps from the
ages of 25 to 45, in which the bodily exchanges are in equilibrium —
the expenses and receipts of nutrition are balanced, and the individual
neither gains nor loses weight. No portion of the food is now to be
appropriated as heretofore in growth ; it may all be devoted to exer-
tion. It is the time of maximum power, the effective working period
of life. The diet should be varied and strong, but of course ought to
be modified in accordance with the activity, constitution and various
circumstances. For hard, exhausting labor, brown or lean meat, the
leguminous seeds, bread, and an admixture of vegetables may be em-
ployed. It can hardly be necessary to add in the light of the princi-
ples of nutrition which have been established, that fat pork is gen-
erally much over-estimated by laborers ; it is the blood-producing
beans and bread with which it is always associated that chiefly im-
parts the strength. It has been sufiiciently pointed ou± that persons
in light sedentary occupations, brain- workers and idlers, should avoid
those more indigestible substances, and whUe reining in the appetite, or
at aU events, not spurring it, should live upon a diet of the most easily
digestible substances.

779. Diet of Advanced Life. — As age comes on, the nutritive condi-
tions of youthhood are reversed, the body can no longer digest and
appropriate sufficient to meet its destructive losses, and there is a
decrease of strength and weight. The tissues shrink, as we see in the
shrivelled hands and wrinkled brow, the hair is changed in compo-
sition, the bones become more earthy and brittle, the cartilages ossify,
there is a general diminution of fat, and a loss of fluids in all parts
except the brain, which becomes more watery. The stomach partici-
pates in the general decline, its diminished and weakened juices be-
coming less capable of dissolving the necessary food ; the circulation
is retarded, and the general vitality lowered. As the solvent powers
of the stomach begin to be enfeebled, and the appetite becomes languid,
elderly people should be admonished to exercise care in selecting food,
and not waste the power they have on refractory indigestible aliments.
Young and tender meats, strong broths, milk, light, well-baked bread,
and tender succulent vegetables, tax the digestive organs least. Nor
should they commit the error of supposing that the waning powers

CONSIDBEATIONS OF DIET. 421

of advancing life can be sustained by increasing tbe quantity of food
eaten. Dr. Chetne remarked more than a hundred years ago,
" Every man after fifty ought to begin to lessen the quantity of his
aliment ; and if he would avoid great and dangerous distempers, and
preserve his senses and faculties clear to the last, he should go on
every seven years abating gradually." When hints like these are
neglected, and persons persist in a high and hearty diet, keeping up a
plethoric state of the system, serious and fatal consequences often
ensue. The blood-vessels of the brain are not only weaker than those
of any other part of the body, but they derive no support as other
vessels do from the elastic pressure of surrounding muscles. In the
imperfect nutrition and growing debility of advancing age, these ves-
sels participate, so that with over-fulness there arises liability of their
giving way, as in brain congestion or apoplexy.

PART FIPTH.

CLEANSING.

- * —

I.— PEINCIPAL CLEANSING AGENTS.

780. Chemical Principles involved. — Dirt has been laconically defined
as ' matter in the wrong place ' ; its removal constitutes ' cleansing.'
The action of cleansing agents, and the management of cleansing pro-
cesses, depend upon the properties of solvents and the operations of
solution and decomposition, and therefore involve questions of chemis-
try. We have had frequent occasion, in the preceding pages, for the
aid of this science in elucidating the phenomena of the household, and
we shall none the less need a knowledge of it to understand the pres-
ent subject. The considerable space given to aliments makes it neces-
sary to restrict our treatment of this topic within narrow limits.

Y81. Water as a Cleansing Agent. — This is the most important and
universal of the agents of purification employed by art. It is so essen-
tial to life, that where man dwells it is always found, and is supplied
by the hand of nature with a copiousness equal to its necessity and
value. Water cleanses by its mechanical action in carrying away dirt
and impurities, and also by its power of dissolving them. While it
possesses the property of dissolving a gi'eat number of substances, it
is at the same time so mild and neutral as not to injure the objects to
which it may be applied.

782. Cleansing of Water. — ^But before water can be used for cleansing
purposes, it may itself reqmve to be cleansed. We have already stated
that it is liable to many forms of impurity. It is often desirable to
remove these contaminations by artificial means, and thus make the
liquid purer, which may be done in various ways. The foreign sub-
stances of water are of two kinds ; Jirst, finely divided earthy matters,
as sand, clay, lime, &c., and particles of vegetable and animal sub-
stances, as of decayed leaves, decomposing wood, insects, &c., diflTused

FILTEATION OP WATEE.

423

through the liquid and mechanically suspended in it, causing it to
appear more or less turbid or cloudy ; and second^ various dissolved
substances which contaminate the water, whUe it is yet clear to the
eye and apparently pure.

783. Purification by Subsidence. — The first sort, or mechanical impu-
rities, if the water is kept perfectly still, will mostly subside, forming
sediment ; the heavier particles falling first, and the finer afterward.
It is wisely arranged that there are but few substances of exactly
the same specific gravity as water ; if there were, this fluid would
scarcely ever be clear. But thei-e are many particles which find their
way into water that are so near its precise weight, that they remain
long suspended, and hence we must resort to other means for their
removal.

784. Purification by Filtering. — "Water strained or leached through
soils and sand-beds comes out free from mechanical contaminations ;
hence if made to percolate through artificial sand-beds, it may be de-
livered clear. A cistern may be divided into two compartments by a
partition which does not reach quite to the bottom. In one of the
divisions is put layers of sand, of different degrees of coarseness, the
finest being at the bottom. The water is poured into these apart-
ments, trickles through the layers, its impurities are detained, and it
comes out into the other division clear. After a time the sand gets
clogged with sediment, and needs to be renewed.

785. Upward flow of Water throngh Filters. — Through natm-e's filter-
beds water ascends^ rising to the surface in
springs, &c. This is better, as their weight
tends to oppose the ascent of the impuri-
ties which are more likely to be left behind.
The arrangement may be made available
in many ways ; the principle is illustrated
in rig. 124. In the cistern or vessel the
partition a does not reach quite to the bot-
tom. The middle division has a perforated bottom of metal or wood,
above which is placed a layer of sand, and upon that a layer of char-
coal. In the partition 5, and above the filter, is an aperture through
which the filtered water passes, and is drawn off by the faucet. Where
rain water is to be preserved for household use (380), an underground
cement tank should be constructed to store it, and a filter similar to the
one described placed above, through which the water from the roof
should flow to the reservoir. Filters may be cleansed by reversing the
direction of the water through them. The principle of filtration is

124.

424 PEIN-CrPAL CLEANSINQ AGENTS.

SO simple that any vessel can be made to answer for it, tall ones being
preferable to shallow. A box, cask, jar, or flower-pot may, with the
least ingenuity, be made to serve the purpose. Besides sand, porous
stone, pounded glass, woollen cloths doubled thickly, sponge, &c.,
are used for filtering. But by far the most valuable agent for the pur-
pose is charcoal. Its prndfying action goes much further than merely
straining out mechanical impurities ; it acts powerfully to absorb and
destroy offensive gases (811). The foulest ditch water made to pass
through a layer of charcoal, comes out sweet, clear, and bright. Ani-
mal charcoal, derived from burnt bones, is more powerful than wood
charcoal, owing, perhaps, to the fact that its mineral matter acts as a
divisor, separating the particles and exposing a larger sm-face,

786. Impurities in Solntion. — But the dissolved impurities of water
cannot be removed by filtering ; it is more difficult to separate these.
By vaporizing, water leaves its impurities behind. Steam conducted
away and condensed in a separate vessel, produces distilled water,
which is its purest form. A tube of copper, glass, or gutta-percha,
connected with the spout of a tea-kettle, and surrounded by cloths
kept saturated with cold water, affords a rude but convenient means
of preparing the purest water. The removal of dissolved impurities
by other means depends upon the special nature of the dissolved sub-
stance. Thus, carbonate of lime or Hmestone, is dissolved in but a
small degree by pure water, but water containing carbonic acid dis-
solves it freely, in proportion to the amount of the contained gas. It
has been found that one gallon (70,000 grains) of 'pure water wiU not
dissolve more than two grains of carbonate of lime. But by the ad-
dition of carbonic acid, it acquires the power of dissolving 10, 20, or
60 grains, as the case may be. The number of grains contained in
a gallon has been adopted to express the * degree of hardness ; ' thus,
10 grains would correspond to 10 degrees of hardness, 20 grains to 20
degrees, and so on. By boUing, the carbonic acid is driven off, the
carbonate of lime precipitates or falls, and the water is softened. This
is the source of the thick fur which gradually accumulates on the in-
ner surface of tea-kettles in limy districts. But all the carbonate is
not at once precipitated when the water is raised to boiling ; it may,
indeed, take two or three hours of brisk boiling to separate all the
lime that is capable of being thus removed. It has been found that
water of 14 degrees of hardness lost two degrees when merely made
to boU ; boiling for five minutes reduced the hardness to 6 degrees, and
for a quarter of an hour to a little more than four degrees. There is,
therefore, reason in the antiquated habit of letting the tea-kettle boil

ALKALINE SUBSTANCES. 425

for some time before the tea is made ; it softens the water (533). We
may relieve water of one impurity by adding another, and the ex-
change is often desirable, as when we wish to convert hard water into
soft. If water be hard from carbonate of lime, the addition of a little
caustic lime (wet to the consistence of cream) will absorb the excess
of carbonic acid, and the insoluble carbonate will separate ; the dan-
ger is that there will be an excess of caustic hme, so that the softened
water wiU be con-osive. If water be hard from sulphate of lime, it is
softened by the addition of potash, or soda, which decomposes the lime
compomid combining with its sulphuric acid. The new compound
is not decomposed by soap (794).

787. Alkaliae Substances for Cleansing. — But there are many sub-
stances upon which water will not act ; other agents must therefore
be called in to aid it. The alkalies, potash, soda, and ammonia, are
most powerful chemical bodies, decomposing a great many different
compounds, especially every thing of a vegetable and animal nature.
But they are far too strong for ordinary use, as they not only remove
dirt and impurities, but corrode and injure the fabrics or objects which
it is desired to cleanse. The alkalies, when pure, from their hot, cor-
rosive, disorganizing nature, are called caustie. But we do not meet
with pure alkalies ; the ever-present carbonic acid of the air combines
with them, forming carbonates. But as the carbonic is a very weak
acid, it only neutralizes them in a partial degree, their carbonates be-
ing very powerfully alkaline. "When the alkalies are commonly spoken
of, it is their carbonates that are meant. The alkaline carbonates dis-
solve readily in water, forming ley. Soda is of a weaker nature than
potash, less liable to injure, and therefore better fitted for detergent
uses. Ammonia is an alkaline gas, called the volatile alhali ; it is
adapted for use in all cases where a gaseous alkaline agent is required.
Its common form, however, is aqua-ammonia^ or solution m. water,
which absorbs a large amount of it.

788. The Alkalies Modified— Soap. — Alkali is the principal agent of
cleansing in most domestic operations, the chief question being how
to restrain and regulate its power. Soap is an artificial compound of
alkali with the acids of oil or fat (195), by which the alkaline energy
is to any required degree masked or subdued. The theory of soap-
making (sapanification) is, that the alkalies decompose the oils, setting
free their basic part or glycerin, which is lost, and combining with
other acids, forms alkaline salts ; soap is therefore really a salt.

789. How Soap is made.— The alkalies require to be in a caustio
state, which is produced by dissolving them and passing the solution

426 PEmciPAL CLEANsma agents.

(ley) tlirougli newly slaked lime, wMch. takes away their carbonic
acid. Soap may be made by the alkalies in their condition of carbon-
ate, but just so far as the alkali is neutralized by the carbonic acid, it
becomes useless for soap-making. In the caustic ley the fats are
boiled, their glyceria is set free, and the fatty acids combining with
the alkali, form soap, which exists as a solution in the water. To ob-
tain it in a solid form, the solution is boiled down to a certain degree
of concentration, when the soap ceases to be soluble, and rises to the
surface in a soft, half-melted state. This being drawn off into moulds,
cools, and forms hard soap. If soda ley is used, the soap may be sep-
arated from the water, in which it is dissolved, by adding common
salt, which forms a brine and at once coagulates the soap. If potash
ley is used, the addition of salt decomposes the potash soap, and forms
a soap of soda. — {Glms-'boo'k of Chemistry.')

790. Hard and Soft Soap. — Soaps are thus of two kinds, hard and
soft, this condition being influenced both by the fat and alkali em-
ployed. The firmer and harder the fat, the solider wiU be the result-
ing soap. With the same alkali, therefore, tallow wiU make a harder
soap than pahn or olive oil, and stearic acid than oleic acid. But the
consistence of soaps depends far more upon the alkali employed. Pot-
ash is very deliquescent, that is, has a strong attraction for water, so
that when exposed it will absorb it from the air and run down into a
fluid or semi-fluid state. The potash retains this water in the condi-
tion of soap, so that potash soaps are always liquid and soft. The
hard soaps, therefore, all contain soda, those with tallow or stearic acid
being the hardest. Potash soaps will not dry, but retain their soft,
jelly-like condition, while some kinds of soda soap become so hard by
drying that at last they can be pulverized.

T91. Water in Soap. — Soap has a strong attraction for water, and
may retain from 50 to 60 per cent, of it, and still remain in the solid
state. Even when dry and hard, it holds from 25 to 30 per cent, of
water. The customer is therefore interested to purchase old, dry
soap, while the vender of course finds his advantage in selling it with
as large an amount of water as possible ; and hence often keeps it in
damp cellars, in an atmosphere saturated with moisture, to prevent it
from drying. The quantity of water contained in a sample is easily
determined, by cutting the soap into thin slices, weighing, and drying
at a temperature not exceeding 212°. It is impossible, however, in
this way, to separate all its water. Its proportion of water influences
the solubility of soap. Some dissolve so freely in washing as to waste
rapidly when used, while others possess the opposite quality — as, for

COMPOSITION Ami VAKIETIE3 OF SOAP. 427

example, "the small cubic mass of wliite, waxy, stubborn substance,
generally met with on the washing stands of bedrooms in hotels, and
which, for an indefinite period, passes on from traveller to travelTer,
each in turn unsuccessfully attempting, by various manoeuvres, and
diverse cunning immersions in water, to coax it into a lather." Hence,
although, as a general rule, old, partially dried soap is preferable, yet
it may be so dry and insoluble, as to involve too great labor in rub-
bing it into a lather ; and to injure articles by excessive friction, with
large chance of failure in the cleansing operation. Business compe- .
tition, and the demand for low-priced articles compel manufacturers
to furnish soaps with a large excess of water ; but these cheap soaps
may not be the most economical.

792. Varieties of Soap, — Common yellow hard soap, consists of soda
with oil or fat and resin. Eesin is a feeble acid, capable of combining
with alkali, but neutralizing it less completely than oil, so that the
compound or soap formed, is too powerfully alkaline. But when
resin is worked with an equal or larger proportion of oD, it makes an
excellent soap for many purposes. Genuine castile soap consists of
olive oil, saponified with soda, and colored ; that which is commonly
sold under this name, however, is an imitation, made with common
fatty materials. Windsor soap consists of tallow, a small proportion
of olive oil and soda. Ordinary wMte soap or curd soap consists of
tallow and soda. Cocoa-nut oil forms a soap that gives a strong
lather. Toilet soaps are made vrith lard, almond oil, palm oil, olive
oil, or suet, combined either with soda or potash, accordingly as they
are desired to be hard or soft, and with as little excess of alkali aa
possible. They are colored and perfumed to taste. Fancy soaps are
essentially common soaps, mixed with diiferent aromatic oils and
coloring substances, and diversified in form so as to suit the fashion
of the day. Soaps are mottled, streaked or stained, by metallic
oxides, chiefly oxides of iron ; which can only be worked through the
body of the soap, to give it the desired marbled appearance, wTien it is
of a certain consistence; such soaps, therefore, cannot be charged
with an excess of water. Transparent soap, is white soap that has
been dissolved in alcohol ; in addition to the detergent properties of
the soap itself, it joins the alcohol, which is sometimes useful for
cleansing purposes, and always harmless. But it wastes rapidly, and
its advantages hardly compensate for its extra cost. Besides water
and soap, the universal and most important agent, other substances
are also employed for special purposes, which we shall notice in con-
nection with their applications and uses.

428 CLEANSING OP TEXTILB AJBTICLBS.

II.— CLEANSING OF TEXTILE AETICLES.

793. Composition of tlie Dirt.— The general principle of cleansing
away aU dirt, spots, and stains, consists in applying to them a sub-
stance which shall have a stronger attraction for the matter composing
them, than this has for the cloth or surface to which it adheres. The
dirt is to be dissolved, and hence for each special form of impurity we
require, if possible, to find special solvents. It is a matter of chemical
affinities. In cleansing textile articles, for example, we desire to
remove the dirt without injuring the fibre of the cloth ; and if it be
possible, without disturbing the color. Alkalies are able to dissolve
almost every thing that presents itself in the form of dirt, but they
are too powerful, discharging colors and corroding the tissue. In
soap, their activity is so restrained that they become generally avail-
able for cleansing purposes. The leading cementing constituent of
dirt upon our garments, is some form of oily substance communicated
by perspiration or contact of the skin, which is constantly covered
by an oleaginous film. The oily, greasy basis of dirt, may be de-
rived from many sources. But water has no aflinity for oily matters
in any form, and cannot dissolve them or alone remove them from
any surface to which they may adhere. This is readily effected by
soap, which being always alkaline, takes direct effect upon the grease,
partially saponifies it and forms with it a compound which dissolves
in water. The oily nature of the soap also increases the pliancy of
the articles with which it is washed.

Y94. Reactions of Soap and Water, — "Water is the common liquid
vehicle of cleansing, and soap the agent resorted to, to render dirt
soluble in water. The soap is either applied directly to the article it
is desired to cleanse, or it may be first dissolved in water. As soap
and water thus act jointly, it is proper to inquire as to their behavior
toward each other. If the water be pure or soft, soap dissolves in it
entirely ; if it be hard, that is, if it contains sidphate of lime or mag-
nesia, the soap, whes added, instead of dissolving, curdles or is de-
composed, and a new soap is formed, which contains lime instead of
potash or soda. This new lime soap will not dissolve, and may be
seen upon the surface of the water as a kind of greasy scum. It
adheres to whatever is washed in it, and gives that unpleasant sensa-
tion called liarshness when we wash our hands. Hence, with hard
water, an excessive quantity of soap is required, while the operation
is much less agreeable and satisfactory than with soft water. To test
its quality of harshness, dissolve a little soap in alcohol and put a few

STEUCTUKE OF THEIE ULTIMATE ITBEES.

429

Fig. 125.

drops in the water it is wished, to examine. If it remains clear, the
water is perfectly soft ; if it becomes cloudy or opaque, the water is
ranked as hard, and according to the degree or density of the cloudi-
ness, is the hardness of the water.

795. Cotton, Linen, and Woollen articlesi — All textUe articles are,
however, not to be treated alike in cleansing. There is a radical dif-
ference in the structure of the fibre between woollen fabrics on the
one hand, and cotton and linen on the other, which makes it necessary
that they should be differently man-
aged. Fig. 125 represents the straight
smooth form of linen and cotton fila-
ments, while Fig. 126 exhibits the
toothed and jagged structure of
woollen fibres. It is evident that
these, by compression and friction,
will mat and lock together, while
the cotton and linen fibres, having
no such asperities of surface, are in-
capable of any thing like close me-
chanical adherence. Hence, the pe-
culiar capabilities of woollen fabrics,
of felting^ fulling^ and shrinking,
caused by the binding together of the ultimate filaments. "We see,
therefore, the impolicy of excessive rubbing in washing woollen fabrics,
and of changing them from hot to cold water, as the contraction that
it causes is essentially a fuUing pro-
cess. The best experience seems to
indicate, that wooUen cloths should
never be put into cold water, but al-
ways into warm; and if changed
from water to water, they should go
from hot to hotter. In the most
skilful modes of cleansing, and pre-
paring delaines for priatuig, the plan
is, to place them first in water at
100° or 120°, and then treat them 8
or 10 times with water 10° hotter ia
each case. Some soak articles in warm water, to which a little wheat-
bran has been added over night. The dirt is loosened, perhaps by a
kind of fermentation. Soakmg in weak soda-water is useful, but too
free a use of alkalies shrinks the fibres of cloth and impairs the

Cotton fibres.

Linen fibres.

Fig. 126.

■Woollen fibres.

430 CLEANSING OF TEXTILE AETICJLES.

strength of tlie tissue. Resin-soap should not be employed to wash
woollen, as the resin has the effect of hardening the fibres. Delicate
textures, and especially white linen, should never be boiled in hard
water. The carbonate of lime precipitated by boiling (786) is not
only itself deposited upon the fabric, but carries down with it whatever
coloring matter happens to exist in the water, and fixes it upon the
fabric, imparting to it a disagreeable, unremovable dirty hue.

T96. Removal of Stains, Spots, &c. — To do this without injury to the
color or the fabric, is sometimes easy, frequently most difficult, and
often impossible. Much may depend upon skilful and persevering ma-
nipulation ; and although various agents, which we are now to men-
tion, are oftentimes valuable, yet good soap, after all, is the chief re-
liance. Grease-spots may generally be removed by the patient appli-
cation of soap and soft water, but other means are also employed.
Alumina^ or the pure principle of clay, has a strong attraction for
fatty substances, and is much used in the form of fullers' earth, a fine-
grained clay, which is prepared by baking and elutriation. It is used
by diffusing a little through water, so as to form a thin paste, spread-
ing upon the stain, and leaving to dry ; the spot then only remains to
be brushed. French chalky a very resinous mineral, is also highly ab-
sorbent of grease. Ox-gall is an excellent and delicate cleansing agent.
It is a liquid soda soap. It removes grease, and is said to fix and
brighten colors, though it has a greenish tinge, which is bad for the
purity of white articles. The application of a red-hot iron closely
above a grease-spot often volatilizes the oily matter out of it. Brown-
paper pressed upon a stain with a warm iron, will often imbibe the
grease. Stains by wax, resin, turpentine, pitch, and substances of a
resinous nature, may be removed by pure alcohol. The fats, resins,
and unctuous oils, are dissolved by essential oils, as oil of turpentine.
Common spirits of turpentine, however, requires to be purified by re-
distillation, or it will leave a resinous stain upon the spot where it Is
used. When pitch, varnish, or oil-paint stains have become dry, they
should be softened with a little butter or lard, before using turpentine
and soap. Burning-fluid combines the solvent powers of both alco-
hol and turpentine. Fruit-stains, wine-stains, and those made by col-
ored vegetable juices, are often nearly indelible, and require various
treatment. Thorough rubbing with soap and soft water ; repeated
dipping in sour butter-milk, and drying in the sun; rubbing on a
thick mixture of starch and cold water, and exposing long to sun and
ah", are among the expedients resorted to. Sulphurous acid is often
employed to bleach out colors. It may be generated at the moment

REMOVAL OP STAINS.

431

of using, by burning a small piece of sulphur in the air, under the
■wide end of a small paper funnel, whose upper orifice is applied near
the cloth. Coffee and chocolate stains require careful soaping and
washing with water at 120°, followed by sulphuration. If discolora-
tion has been produced by acids, water of ammonia should be applied ;
if spots have been made by alkaline substances, moderately strong
vinegar may be applied ; if upon a delicate article, the vinegar should
be decolorized by filtering through powdered charcoal. For iron
mould, or ink stains, lemon-juice or salt of sorrel (oxalate of potash)
may be used. If the stains are of long standing, it may be necessary to
use oxalic acid, which is much more powerful. It may be applied in
powder upon the spot, previously moistened with water, well rubbed
on, and then washed off with pure water. It should be effectually
washed ou^, for it is highly corrosive to textile fibres. The staining
principle of common indelible inh is nitrate of sUver. It may be re-
moved by first soaking in a solution of common salt, which produces
chloride of sUver, and afterwards washing with ammonia, which dis-
solves the chloride.

Fie. 127.

III.— CLEANSING OF THE PEESON.

797. Stractnre aad Offices of the Skin. — A glance at the curious and
beautiful structure of the skin, and its important offices, wUl assist us
to understand the causes
and nature of its defile-
ments. The outer layer
of the skin (cuticle) is
formed of albuminous
cells, which, losing their
liquid contents by evapo-
ration at the surface, are
flattened into exceeding-
ly minute thin scales, of
a horny, resisting quality,
which serves as a pro-
tection to the sensitive
or true skin underneath.
The surface of the cuticle
is constantly loosening.

41^ k:

Surface of tie cuticle greatly magnified, showing
the pores and hairs.

and wearing off in fine,

powdery scales, which are replaced by new growths from below.

Figs. 127, 128, exhibit the structure of the skin. It is an organ of

432

CLEANSING OF THE PERSON.

Fig. 128.

drainage, with a double function ; co-operating, with the kidneys, on
the one hand, to relieve the system of water, and with the lungs on
the other, to extrude its gases. The perspiratory tubes, which open

through the cuticle upon the
surface, forming pores, are spi-
ral-shaped, as shown in the fig-
ure, and terminate in glands be-
low. Prof. Wilson says, "I
counted the perspiratory pores
on the palm of the hand, and
found 8528 in a square inch.
Each of these pores being the
aperture of a little tube, about a
quarter of an inch long, it fol-
lows, that in a square inch of
skin on the palm of the hand,
there exists a length of tube
equal to 882 inches. I think
that 2800 might be taken as a
fair average of the number of
pores on the square inch, and

Vertical section of the skin, greatly magnified: 700 the number of inches in
a the cuticle, outer, or scarf skin: & (Z the true T ii, ^ j.-u -u i r j>

skin; c oil-tube and gland; e sweatglands and lengtn tOr the Wbole SUrtace Ot

their ducts, the outlets at the surface being ^he body. Now the number of
the pores ; / hairs ; g cellular substances. -^

square inches of surface, in a man
of ordinary height and bulk, is 2500 ; the whole number of pores, there-
fore, is 7,000,000, and the amount of perspiratory tube 48,600 yards, or
nearly 28 mUes." Twenty or thirty ounces of perspiration escape
through these channels daily, and upon evaporating into the air, le^ve
a residue upon the surface, of animal and saline matter, consistiag of
acids, alkahes, calcareous earth, &c.

798. Impurities of the Skin. — "We have noticed the enormous ex-
haling and absorbing surface of the lungs (283), and the consequent
danger to which we are exposed by the inhalation of foreign, poison-
ous substances, from the air. Evidently, if the skin were in the same
condition, if its millions of little mouths were constantly and freely
open to the air, the danger from absorption of infectious matter would
be greatly heightened. But this consequence is wisely guarded against
by a set of glands, whose special ofSce it is to secrete oily matter to
bedew the surface of the body. We notice that where this oUy coat-
ing is in excess, it often gives an unseemly polish to the features ;

MANAGEMENT OF THE SKIN.

433

•while if it be deficient or absent, tbe Bkin is dry, barsb, and rough.
Now this oleaginous pellicle, while offering no hindrance to cxhalob-
tion, or the outward escape of waste matter, protects the system
against too free absorption from without. It is this oily distilment,
perpetually covering the cutaneous surface, that seizes upon aU forms
of dirt and impurity, cementing them into an adherent layer of dirt,
comprising also the dregs of perspiratory evaporation, and the scales
of scarf-skin just noticed. This crust of dirt may at length accumulate
and consolidate, until it obstructs the pores, arrests free drainage, and
thus seriously interferes with the functions of the skin, and the health
of the body. As a consequence of the neglected state of this organ, the
sedentary and irregular habits of refined society, the unctuous sys-
tem of the skin becomes sluggish, and its actions torpid Fig. 129.
and irregular, and instead of the constant fiow through
the oil-tubes, their contents become dry, dense, impacted,
and do not freely escape. They accumulate in the ob-
structed passages and form pimples. "When those are
squeezed between the finger nails, there issues a little
cylindrical mass of white unctuous matter, which, when
examined with the microscope, reveals a little animalcula,
represented by Fig. 129. It is called by Dr. "Wilson,
who has studied its history and habitudes for six months
at a time, steatozoon folliculorum ; that is, the 'animal of
the oily product of the skin.' These little personages are
caterpillar-like, with head, feelers, four pair of legs, and
a long tail. They are about the l-45th of an inch in
length, and always occupy the same position in the oil-
tube, the head being directed inwards. The little mass
shot out from the pimple may contain from two to twenty
of them.

799. Cleansing of the Skin— Ablution.— As oil is the basis of the coat-
ing of dirt which daily concretes upon the skin, it is obvious that
water alone is incapable of removing it. Soap is the proper skin-
detergent. It partially saponifies the oil, rendering it miscible and
soluble in water. The alkaline element of soap also softens and dis-
solves a part of the cuticle which, when rubbed off, carries with it the
dirt. Thus any washing with soap removes the face of the old scarf-
skin and leaves a new one. If the hands are too long exposed to the
action of an alkaline soap, they become tender, that is, the cuticle
dissolves away, and gets so thin as not to protect the inner or sensitive
skin. Wash powders are inferior to soap, and injure the whitenegg
19

434 CLEANsma of the peeson.

and purity of tlie skin. If soap produce irritation, it is because tlie
skin is in some way morbid. It should then be used in small quantity
at first, increasing it gradually.

800. PMlosopliy of wasliing the Face— Dr. Wilson thus pleasantly
discourses on the art and mystery of cleansing the face. " And now,
dear reader, having detertained to wash your face, how will you set
about it ? there are many wrong ways of effecting so simple a pur-
pose ; there is but one right way. I will tell it to you. Fill your
basin about two-thirds full with fresh water ; dip your face in the
water, and then your hands. Soap the hands well, and pass the
soaped hands with gentle friction over the whole face. Having per-
formed this part of the operation thoroughly, dip the face in the water
a second time, and rinse it completely : you may add very much to
the luxury of the latter part of the process by having a second basin
ready with fresh water to perform a final rinsing. And now you will
say, ' What are the wrong ways of washing the face ? ' Why, the
wrong ways are — ^using the towel, the sponge or fiannel as a means
of conveying and applying the soap to the face, and omitting the
riasing at the conclusion. If you reflect, you wiL. see at once that the
hands are the softest and the most perfect means of carrying the soap,
and employing that amount of friction to the surface with the soap
which is necessary to remove the old and dirty scar!" and bring out
the new and clean one from below. Moreover, the hand is a sentient
rubber, or rubber endowed with mind ; it knows when and where to
rub hard, where softly, where to bend here or there into the little
hoUows and crevices where dust is apt to congregate ; or where to
find little ugly clusters of black-nosed grubs, the which are rubbed
out and off, and dissolved by soap and friction. In a word, the hand
enables you to combine efficient friction of the skin with complete
ablution ; whereas in every other way ablution must be imperfect.
Then, as regards drying the face, a moderately soft and thick towel
should be used ; a very rough towel is not desirable, nor one of thin
texture. This is a point that may be safely left to your own taste and
feelings. The question of friction during the drying is of more con-
sequence, and this is a reason why the towel should be moderately
soft, that you may employ friction and regulate the amount. With a
very rough towel it is impossible to use friction, for its tenderest pres-
sure may be enough to excoriate the skin ; and a very soft towel is
equally open to objection from its inadequacy to fulfil the obligation
of friction during the process of drying. In washing the face you

SUBSTANCES ACTING UPON THE TEETH. 435

Lave three objects to fulfil — to remove the dirt, to give freshness,
and to impart tone and vigor to the skin."

801. Cleansing the Teeth. — The effect of talking, singing and breath-
ing through the mouth, is to evaporate the -vvater of the saliva, leaving
its solid constituents, animal matter and salts, as a residue which accu-
mulates upon th,e teeth as tartar. This, together with the fragments
of the food which get lodged in the cavities between the teeth, is a
constant cause of impurity in the mouth, which should, therefore, be
often cleansed. Dentifrices are preparations of liquid, paste and pow-
der for cleansing the teeth. Some act chemically to dissolve the tar-
tarous incrustation, as dilute muriatic acid, which also removes dis-
colorations and whitens the teeth. But it also corrodes their enamel,
and rapidly, destroys them. Its habitual or frequent use is, therefore,
most pernicious. It may be rarely and cautiously employed to efface
dark spots or black specks upon the teeth, but it should be quickly
neutralized with chalk, and washed away with water. Tooth pow-
ders, which act mechanically, are better. They require to have a cer-
tain degree of hardness or grittiness to enable them to remove the
foreign substances adherent to the teeth ; but if too hard, they injure
the enamel. The powder of ground pumice stone is employed, but it
is too sharp for any thing more than exceptional use — say once in two
or three months. Chalk is soft and excellent ; not common chalk
pulverized, for that contains flinty particles, but prepared chalk of the
druggist. Charcoal and powdered cuttle fishbone are good tooth de-
tergents. Yet all insoluble powders are liable to the objection, that
they accumulate in the space formed by the fold of the gum and the
neck of the tooth, presenting a colored circle. The powder is there-
fore often colored red with carmine or tole armeniac. Myrrh, cin-
namon, &c., are added as perfume. Shatany, cinchona, and catechu^
are added to exert an astringent and hardening effect upon the
gums. If substances are required Avhich shall dissolve in using,
sulphate of potash, phosphate of soda,, cream of tartar, and com-
mon salt may be used. Disinfecting and deodorizing tooth-powders
and washes which destroy the unpleasant odor of the breath, and
tend to whiten statued teeth, owe their efficiency to chloride of lime
(807). Such a preparation may be made by mixing one part chloride
of lime with twenty or thirty of chalk. A disinfecting mouth- wash
is made by digesting three drachms of chloride of lime in two ounces
of distilled water, and to the filtered solution adding two ounces of
spirit, and scenting, as with attar of roses. — (Peeeiea.)

436 CLEANSING THE AIR.

lY— CLEANSING THE AIR.

802. It "was noticed (303) that the atmosphere constantly tends to
Belf-purification ; its oxygen is a universal cleanser ; it gradually but
certainly consumes the noxious gases that are poured into it, from
whatever source. Yet its action is slow, and it often happens that in-
jurious exhalations are set free in such quantities, or in such confined
spaces, as to require other and active means for their removal. Besides
ventilation, other methods are also to some extent available for getting
rid of atmospheric impurities, some of which will now be noticed.
The subject of malaria, air-poisons, atmospheric infection — what they
are, how they act, and in what manner and to what extent they are
capable of counteraction — is yet involved in much obscurity. The
substances which relieve us of disagreeable odors and noxious emana-
tions are numerous, and take effect in various ways.

808. Palliatives and Disguiscrs. — "When atmospheric impurities report
themselves to the olfactory sense, they are pretty sure to receive at-
tention, though we too often seek only relief from the disagreeable
smell. This is done, not by removing it, but by smothering or over-
powering it with sweet scents. "With musk, attar of roses, lavender,
odoriferous gums, fragrant spices, aromatic vinegars, &c., a cloud of
perfume is raised which masks the unwholesome odor. This may be
often an excusable resort, but it is too frequently a slovenly expedient
to conceal the effects of uncleanliness. " They are the only resources
in rude and dirty times against the offensive emanations from decay-
ing animal and vegetable substances, from undrained and untidy dwell-
ings, from unclean clothes, from ill- washed skins and ill-used stom-
achs. The scented handkerchief in these cases takes the place of the
sponge and the shower-bath, the pastUe hides the want of ventHlation,
the attar of roses seems to render the scavenger unnecessary, and a
sprinkling of musk sets all other stenches and smells at defiance. The
fiercest demand for the luxury of civilized perfumes may exist where
the disregard of healthy cleanliness is the greatest." In this connexion
we may mention those agencies which exert a palliative effect, re^nov-
ing rather than concealing or destroying the offensive bodies. Thus,
sulphuretted hydrogen, the gas of rotten eggs, and which is copiously
set free from putrefying animal bodies, may be absorbed by water, but
the water does not decompose or neutralize it ; if heated, it all escapes
back again into the air. The moist soil also acts as an absorbent of
bad gases, fixing and retaining them during cold and wet weather, and
setting them free during drought or heat.

ACTION OF LIMB AND CHLOEINE. 437

804. Action of Disinfeetants. — A large number of substances have
been discovered which destroy evil odors and injurious gases. These
are termed disinfectants, and act chemically either to decompose the
noxious substances or to combine with them, producing new and harm-
less compounds.

805. Freshly Burned Lime — Qaicklimc. — Lime newly burned, caustic
and hydrated (slaked), is used to purify the air. It has a powerful at-
traction for carbonic acid, half a cubic foot of it absorbing nearly 40
cubic feet of the gas. A few lbs. of it placed upon a board or tray in
the bed-room, or oftentimes in the sick-room, rapidly absorbs this de-
leterious substance, while the condensed gas is immediately replaced
by an equal volume of fresh air from without. The oLly inconve-
nience is, that as the lime combines with the acid, the water used in
slaking is set free, which charges the air with aqueous vapor. The in-
habitants of newly built houses, and even after a considerable time,
often experience a similar annoyance. It is not from the ordinary
wetness of new walls that the moisture proceeds, hut from the dry
hydrate of lime in the mortar. The carbonic acid of the room, from
the lungs of its inmates, gradually penetrates the plaster and displaces
this water. "When quicklime is strewed over fresh animal and vegeta-
ble substances, it retards their decay, and so influences the changes
that ammonia and other volatile and strong-smelling compounds are
less freely produced. If spread upon putrefying refuse, it acts differ-
ently, seizing upon the acids and setting free the pungent gaseous alka-
lies. It at first liberates a large amount of offensive gaseous matter,
and then checks the decomposition.

806. Chlorine as a Disinfectant. — But the most powerful disinfecting
agent is chlorine gas^ one of the elements of common salt (590). It is
an energetic chemical agent, used for the destruction of coloring mat-
ters, as in bleaching cotton, linen, fatty substances, &c. The remark-
able lightness and tenuity of hydrogen have been referred to (76). It
combines with many heavier elements, forming compounds of extreme
volatility, lighter than the air, and which constantly ascend into it.
It is this highly rarefied gas which seems to stand closest upon the bor-
ders of nothing, — but becomes potent through its very nothingness,
that gives wing to the deadly exhalations, lifting them away from the
ground into the breathing region. The gaseous poisons of the air, so
far as known, are compounds of hydrogen. For this substance chlo-
rine has a strong attraction, decomposing and destroying its com-
pounds, and being a gas, it may also diffuse through the air, and thu3
cleanse and disinfect it.

438 GLEANSING THE AIB.

807. Forms of its use— CUoride of Lime. — Chlorine gas may be set

fire in two ways : first, by pouring hydrochloric acid upon finely
powdered black oxide of manganese; and second, by pouring sul-
phuric acid upon a mixture of common salt with the same oxide.
Chlorine stands first as a disinfectant. It is cheap, easily prepared,
acts efficiently though diluted with much air, and in this state of dilu-
tion is breathable without injury even by the sick. It corrodes me-
tallic substances, which should therefore be removed as far as possi-
ble from apartments in which it is to be used. (Other disinfecting
gases are liable to the same objection.) If it be desired to generate
large quantities of chlorine, the methods just mentioned may be re-
sorted to, but apartments cannot then be occupied, as chlorine in any
considerable amount is to a high degree irritating and inflammatory to
the throat and air passages. In aU common cases chloride of lime
may be employed. This is lime charged with chlorine gas, which
combines with it so easily that it is slowly set free when exposed to
the air. It has a double action : the lime combines with all acid
bodies aa carbonic acid, sulphuretted hydrogen, while chlorine
diffuses through the air, decomposing all the noxious compounds of
hydrogen. It may be spread upon any putrefying substance, when it
destroys noxious bodies as they are formed. It may be placed in a
room, when carbonic acid slowly combines with the lime, and the
chlorine is gradually set free. It may be dissolved in water and
sprinkled through bad smelling apartments, or cloths dipped in a
diluted solution of it can be hung up in the room. After infectious
diseases, a weak solution of chloride of lime should be sprinkled over
sheets and family linen before washing, and the walls of the room
washed down with it. Chloride of soda is used in the same manner
as chloride of lime.

808. Disinfection by Snlphnrons icid. — When sulphur is burned in
the open air, oxygen combines with it, produciug sulpTiurous acid gas.
It has a noxious odor, and if largely mingled with the air, is
injurious to health. It is an active chemical agent, much used for
bleaching, as may be illustrated by holding over a burning sulphur
match, a red rose, which is immediately whitened. "WooUen, silk, and
other garments are bleached by it. It is of a strongly acid nature and
combines with alkaline vapors of the air, while it decomposes and de-
stroys other substances, as sulphuretted and phosphuretted hydrogen.
When an apartment is fumigated by burning sulphur, it is necessary
to leave it ; it corrodes metals.

809. Other Substances nsed for Disinfection. — Ohhride of iron is a

CHAECOAL HASTENS CHANGE OF MATTEE. 439

cheap and eflScient disinfectant, thougli it imparts a brown or bluish
stain wherever its solution falls. Chloride of zinc is equally efficient,
but more expensive. Sulphate of iron (copperas or green vitriol) haa
strong disinfecting power. Either of these substances dissolved ia
water, (one, two, or three lbs. to the pailful,) thrown into vaults, cess-
pools, or gutters, or over any foul masses of fermenting matter, exert
not only a disinfecting and deodorizing action, but partially arrest
putrefactive change. Acetate and nitrate of lead are strong disin-
fectants. These substances are all solids. They do not assume the
gaseous form, but act, dissolved in water, by fixation of noxious sub-
stances as they are set free.

810. EflTects of Charcoal. — It is well known that charcoal is a power-
ful deodorizer. Strewn over heaps of decomposing filth, or the bodies
of dead animals, it prevents the escape of effluvia. Tainted meat sur-
rounded with it, becomes sweetened. Foul water strained through it
is pni'ified. Placed in shallow trays in apartments where the air is
offensive, it quickly restores it to sweetness, and even purges the putrid
air of dissecting rooms. Charcoal has also a powerful attraction for
coloring substances, and is used for bleaching sirups, liquors, &c., by
filtration through it.

811. Mode of Action of Charcoal. — Charcoal produces these effects in
a particular manner, unlike any substance that has been noticed.
Most, if not aU. porous solids, have the power of absorbing and con-
densing gases within their minute interior spaces. Charcoal is ex-
ceedingly porous, and has this property pre-eminently. A cubic inch
of freshly burned, light, wood charcoal, wUl absorb nearly 100 inches
of gaseous ammonia ; 50 or 60 of sulphuretted hydrogen, and nearly
10 of oxygen. The charcoals are not aU alike in efficacy. Animal
charcoal — from charred animal substances — and peat charcoal, are
both superior in absorbing and condensing power to wood charcoal.
But how d oes this substance produce its effects ? It was formerly
supposed, simply by sponging up the deleterious gases and retaining
them in its pores. But later inquiries have thrown light upon this
matter, and we now understand that by means of this mechanical
condensation, charcoal becomes a powerful agent of destructive change.
Chemical action is hastened in proportion to the nearness with which
the atoms can be brought together. In the pores of the coal they are
forced into such close proximity, as rapidly to augment the chemical
changes. The condensed oxygen seizes upon the other gases present,
producing new compounds, oxidized products. In this way ammonia
ia changed to nitric acid, and sulphuretted hydrogen to sulphuric acid.

440 CLEANSINa THE AIR.

In this way, charcoal promotes oxidation, so that instead of being ac
antiseptic or preventer of change, it is really an accelerator of decom-
position,* This active property of hastening decomposition has been
made medically available in the form of poultice, to corrode away
sloughing and gangrenous flesh in malignant wounds and sores. Dr.
BiED, in his work on the medical uses of charcoal, quotes several cases :
we give one. " A man was admitted to St. Mary's hospital with a slough-
ing sore upon his leg. A poultice of this kind was put on, and in sis
hours the dead portion was reduced in size fully one-quarter. At the
same time, the poultice thus made, effectually prevents any odor or
putrefying exhalations proceeding from the slough and pervading the
apartment." Dr. Stenhouse, who, in 1855, first drew distinct atten-
tion to the fact, that charcoal is rather a hastener of decomposition
than an antiseptic, has contrived ventilating arrangements in which the
air of dwellings is filtered through charcoal. He has also a breath-filter
or respirator, consisting of a hollow case of fine flexible wire-gauze,
_, . which is mounted upon the face, as

shown in Tig. 130. It is filled with
coarsely powdered charcoal, so that all
the air that enters the lungs is strained of
its impurities. Charcoal is thus strongly
commended as a disinfectant. It has
many advantages over the preparations
of chlorine, as it neither injures the
texture of substances, nor corrodes
metals, nor discharges the color of
fabrics by contact, nor gives off dis-
agreeable fumes. It is never in anj
application or use, poisonous or danger-
ous, but is entirely innocent, and in only one solitary instance can it
become pernicious, and that is when it ceases to become charcoal, and
is burnt in a perfectly closed room.

* " I took the body of an English terrier, -weight about ten lbs., placed it on a stone
floor in a small apartment, and lightly covered it with charcoal; although the weather
■was very warm, not the slightest odor could be detected. By some accident the charcoal
was disturbed, and a large portion of the mass was left uncovered ; in spite of this the
circumjacent charcoal was sufficient to prevent any offensive stench. Upon seeing this,
I left the body completely uncovered, merely surrounding it with the deodorizing agent;
this again prevented any disagreeable smell. Having determined this fact, I again cov-
ered the carcass. In less than a fortnight not a particle of flesh remained upon the
bones, which were picked perfectly clean, and were of a snowy whiteness."— (Bibd on
Chabcoal.)

POISONS, AND THEIE ANTTDOTES. 441

v.— POISONS.

812. Poisons and Poisoning. — ^Poisons are divided into three classes
according to the way they act npon the system. Acrid or irritant
poisons directly corrode or destroy the tissues with which they come
in contact, and cause intense pain, but do not suspend consciousness.
Strong acids, and alkalies, and indeed all poisonous metallic substances,
belong to this class. JSTarcotic poisons are such as produce stupor, as
opium, carbonic acid. N'arcoto-acrids, as tobacco, alcohol, &c., act
both as acrids and narcotics. Some of these poisons may be arrested
or neutralized in the system before producing fatal results, if measures
are promptly taken, but no time is to be lost. "Whatever is done,
must be done at once ; the delay necessary to ransack books for anti-
dotes, or to get a physician, may cost the victim's life. If sevei-e pain
in the stomach, vomiting, purging, &c., come on after a meal, poisoning
is to be suspected. Something may be gathered from the demeanor
of the poisoned individual, and a knowledge of circumstances. A
person who has swallowed poison, by way of suicide, will be apt to
be more silent about it than one who has taken it accidentally or to
whom it has been administered purposely.

813. Eesonrces in case of Poisoning, — If the vial or vessel from
which the poison was taken be accessible, or if there be discolored
spots upon the dress, and if on applying the tongue to either there is
sourness, we infer that the poison is acid. In this case, or if it be
known that an acid has been swallowed, chalk or whiting, mixed with
milk, should be given copiously. If these are not at hand, plaster torn
from the wall, or soap, may be substituted. Alkalies are given as an-
tidotes to acids, and the reverse. Thus, poisoning by osalic or sul-
phuric acids may be remedied by soda or saleratus, while poisoning by
pearlash would be arrested by vinegar. So if lime get into the eyes,
it may be dissolved and washed out by moderately strong vinegar.
The antidote for corrosive sublimate is eggs; for sugar of lead, epsom
salts. If other or unknown poisons have been taken, the stomach
should be freed of its contents as speedily as possible by an emetic, the
readiest and best being a teaspoonful of mustard stirred up with
warm water, its action being promoted by copious draughts of the
latter. The poison called arsenic or ratsbane is not the metal arsenic,
but the oxide of arsenic — a white, slightly sweetish insoluble powder.
Being destitute of any decided taste, it is eminently fitted for the pur-
pose of the poisoner, as it may be mingled with food without easy
detection. But while this circumstance is fitted to tempt the mm--

19*

442 AESENIC POISONTN-G.

derer, there follows another which is fraught with sure retribution,
No poison is so ready and certain of detection as arsenic. And not
only this, but " it is as indestructible as adamant. The corpse may
decay ; the coffin fall to dust ; hundreds or thousands of years may
pass, but underneath the mound of earth, in the spot where the
corpse was laid, there is the arsenic." The best antidote to this poison
is the hydrated sesquioxide of iron, which combines with it, forming an
inert compound ; in the absence of this, milk, sugar, eggs, &c., may
be given, and an emetic should be administered as quickly as possible
to relieve the stomach of its contents : it must be prompt to be
available.

APPENDIX.

ADDITIONAL LIBT OF TEMPEEATUEES.

Lowest artificial cold 187° below zero, or 219° below freezing water,
Carbonic acid freezes 148° below zero, or 180° below freezing water,
Lowest natural temperature at Yakutsk, In Siberia, 84° below zero.
Estimated mean temperature of the North Pole, 13° below zero.
Salt water of specific gravity 1-104, and oil of turpentine freezes,
Wine freezes, .......

Blood freezes, .......

Milk freezes, ......

"Water freezes, . . . .

Alcohol boils in a vacuum, ....

Mean winter temperature of England,

Temperature of hybernating animals, .

Mean winter temperature at Eome,

Mean annual temperature at Toronto, .

Putrefaction begins, ......

Cultivation of the vine begins at a mean annual temperature o^

Mean annual temperature of New York, .

Mean annual temperature at Eome, ....

Cultivation of the vine ends, ....

"Water boils in a vacuum, .....

Temperature of glow-worm and cricket,
Silk-worm hatches — temperature of germination,
Tepid bath begins, ......

Acetous fermentation, ......

Putrefaction rapid, ......

Tepid bath ends, — warm bath begins, ....

Temperature in man — blood heat, ....

Warm bath ends, — vapor bath begins, ....

Cold-blooded animals die, .....

Vapor bath ends, .......

Temperature in a boat In Upper Egypt, .

Steamboat's engine-room (West Indies),

Starch converted to sugar, .....

Finland vapor bath, ......

Alcohol (specific gravity -794) boils,

Water boils at the summit of Mont Blanc (15,360 ft, elevation).

Water boils at an elevation of a mile.

Water boils at the sea-level, .....

14°
20°
25°
80°
82°
86°
87.8°
88°
41°
43°
50°
50°
54°
59°
65°
72°
74°
77°

95°

106°
130°
188°
155°
160°
170°
174°
182°
202°
212°

444

APPENDIX.

Syrup, 53 per cent, sugar, boils,
Water of the Dead Sea boils,
Syrup, 80 per cent, sugar, boils.
Gypsum converted to plaster.

216°

223°
264°
291°

B.

We append an illustration of the astonishing scale of minuteness upon which
even art has found it practicable to conduct her operations. "Within a circle of
but one-thirtieth of an inch in diameter — a mere visible dot, as
we see in the figure, M. Feoment, by an exquisite mechanical
contrivance, executed an elaborate piece of writing and engraving.
Of course no result was visible to the naked eye ; but when the
work was placed under a compound microscope, its details came
out, as we see in fig. 131, which is a transcript of the magnified view. With
what marvellous accuracy were those infinitesimal movements performed.

Fio. 131.

INDEX.

Ablntion of the face, 434

Acids, vegetable, 225 ; composition of, 225 ;
of apples, 225; of lemons, 225; of grapes,
225 ; nature of, 369.

Acetic acid, 226.

Air, non-conduction of, 35 ; pressure of, 43,
151 ; composition of, 49, 153 ; contami-
nation of by gas burning, 123 ; general
ofiices of, 150 ; weight of, 151 ; etfect of
varying pressure of,l52 ; intermixture of,
153 ; constituents of, 154 ; oxygen of, 154 ;
moisture in, 157 ; conditions of drying
power of, 153 ; system affected by moist,
160 ; by dry, 161, 170 ; effects of its ingre-
dients, 163; impurities of external, 165;
conditions of salubrity, 166 ; self-purify-
ing, 167 ; causes of impurity of in dwell-
ings, 168 ; bad influence of heating appa-
ratus upon, 168 ; aflected by hot-iron sur-
faces, 169 ; composition of, altered by
heating, 169 ; impurities of, from the body,
170 ; Dr. Farraday on, 171 ; of bedrooms,
171 ; purity of the design of nature, 172 ;
danger of foul, 174 ; contamination of, in-
doors, 181 ; vitiated by illumination, 183 ;
vitiated by the person, 184 ; influence of
plants upon, 185; in motion, 185; cur-
rents in close rooms, 1S6, 187 ; stratifica-
tion of, in rooms, 187; currents through
doors and windows, 189, 190 ; currents
atfecting the system, 191 ; supply of, by
crevices, &c., 195 ; modes of introducing,
196 ; efl'ect of breathing rarified, 355.

Albumen, vegetable, 227 ; composition of,
227 ; properties of, 22S.

Alcohol, as an illuminator, 116 ; as a pre-
server, 314 ; the principle of spirituous
liquors, 378.

Aliments, source of, 205; classification of,
206, 207 ; undue proportions of, 388 ; cor-
rection of, 401.

Alkalies, 369.

Amaurosis, 145 ; subjects of, 146.

Apartments, size of for breathing, 184.

Appetite, regulation of, 410.

Apples, composition of, 244.

Argand burners, 112.

Arnott's valve, 19S ; importance of, 199.

Arrow-root, 215,

Arsenic, 441.

Artificial light, 105; from ignition, 105;
measurement of, 124 ; color of, 137 ; inju-
rious action of, 137 ; how it affects the
eyes, 139 ; effects upon the retina, 140,
144; heat accompanying, 141; unsteadi-
ness of, 142 ; extraneous rays, 143 ; may
produce inflammation, 144 ; management
of, 146 ; whitening by absorption, 148.

B

Barley, 240.

Barometer, 43.

Beans, composition, 242 ; mineral matter
in, 243 ; digestibility of, 390.

Beaumont, Dr's. table, 343.

Bedrooms, air of, 171 ; ventilation of, 201.

Beets, 247.

Beverages, 289.

Blood, constituents of, 250, 347; globules,
347; alkaline, 370.

Boiling, culinary changes by, 277.

Boiling point, elevation of, 44.

Bran, composition of, 235.

Brain, measure of its change, 365; phos-
phatic constituents of, 366 ; has its specSl
nutriments, 367 ; excitants, 369.

Braziers, 61, 62.

Bread, from plain flour and water, 258 ; fer-
mented, 259 ; objections to fermented,
267 ; unfermented, 263 ; raised by chemi-
cals, 269, 270 ; heat of baking, 271 ; loss of
weight in baking, 272 ; changes in the
crust, 272 ; in the crumb, 272 ; moisture
in, 273; good, 273; influence of salt on,
274; alum, 274; effects of lime water,
275; different kinds of, 276; white and
brown, 277 ; coarse and fine, effects of, 389.

Broth for the sick, 284.

Buckwheat, composition of, 241.

Burning fluids, composition of, 116; how
explosive, 116 ; conditions of accident
from, 117 ; how used with safety, 117.

Butter, separation, of, 285 ; composition and
properties of, 286 ; cause of its change-
ableness, 315 ; cause of rancidity, 316 ; ac-
tion of air upon, 316 ; substances used to
preserve, 317.

446

rtTDEX.

c

Cabbage, nutritive properties of, 244.

Camphene, 115 ; combustion of, 115 ; why it
spoils, 115.

Candles. 108; stearic acid, 109 ; tallow, 109;
spermaceti and wax, 109 ; structure of,
110; olEce of wick, 110; how it burns,
110 ; snuffing of, 111 ; shade for, 148.

Carbon, office in fuel, 49; heating effects
of, 51.

Carbonic acid, 161 ; physiological effects of,
162; in small quantities, 162; case of sui-
cide by, 162; necessity for, in air, 163;
exhaled by respiration, 182.

Carrots, 248.

Casein, composition of, 228.

Cataract, 136.

Cellars, foul air in, 1T3.

Changes in the living system, 826 ; rate of,
32T ; equalization of bodily, 362 ; hasten-
ing and retarding, 363.

Charcoal, as fuel, 53 ; as a disinfectant, 489 ;
mode of its action, 439 ; respirator, 440.

Cheese, preparation of, 288; changes by
time, 317 ; influence in digestion, 391.

Chevreul, 91.

Chimneys, draught of, 55 ; causes of smoky,
56, 57, 58, 59 ; currents in summer, 200.

\!hocolate, 293 ; adulterations, 800; effects,

378.
Cholera and foul air, 175.

Churning, 285.

Citric acid, 225.

Cleansing, principles involved in, 422 ; by
alkaline substances, 425 ; of textile arti-
cles, 428; cottons, linens, and woollens,
429 ; of spots and stains, 430 ; agents for,
430 ; of the person, 4;B1 ; of the skin, 433 ;
of the face, 434; of the teeth, 485; of the
air, 486.

Climate, artificial, 22.

Coal, mineral, 53, 54.

Cocoa, composition, 298 ; preparation, 299 ;
how used, 299.

Coffee, varieties, 294; composition, 294;
effects of roasting, 295 ; effects of time
upon, 296 ; mode of preparation, 297 ; adul-
teration, 297 ; how detected, 298 ; Lehman
on the effects of, 378.

Cold, when most fatal, 358.

Color, influence upon radiation, 30; upon
absorption, 31 ; Newton's theory of, 89 ;
Brewster's theory, 89 ; complementary,
90 ; tints and tones of, 91 ; chromatic cir-
cles, 92 ; contrast of, 97 ; mutually inju-
rious, 98 ; contrast of tone, 99 ; harmonies
of, 100 ; circumstances influencing, 101 ;
associated with white, black, gray, 101 ;
combining, 102 ; influence of, upon com-
plexion, 102 ; arrangement of flowers, 103 ;
paper-hangings, 103 ; furniture, 105 ; popu-
lar recognition of the effects of, 140 ; asso-
ciated heat of, 141.
Combustion, products of, 50; air hinders,

55 ; within the body, 851.
Common salt transparent to heat, 28 ; effect
upon bread, 274; uses of, in the system,
871; contained in food, 872; mode of crys-
tallization, 311 ; puriflcation of, 312 ; how
it preserves meat, 312; how it injures
meat, 313 ; too littls and too much, 377.

Complexion, 102.

Condiments, 391.

Contagion and foul air, 175.

Corn starch, 215.

Cream, production of, 253.

Culinary art, objects of, 256.

Culinary utensils, 318 ; of iron, 813 ; of tin,
819; zinc, 320; copper, 320, 321; enam-
elled ironware, 321 ; earthenware, 322 ;
Porcelain ware, 323.

Dentifrices, 485.

Dew, cause of, 82 ; dew-point, 158.

Diet, for brain-workers, 868; mixed indis-
pensable, 398; exclusive meat, bad econ-
omy, 896 ; required by children, 402 ; of
flesh, influence of, 405 ; mineral matters
replacable in, 406 ; economy of vegetable
and animal, 407 ; diversities of, 408, 409 ;
scale of U. S. Navy, 410, and the capacity
of exertion, 415 ; order and variety in,
416, and corpulence, 417; of infancy, 417,
418; of childhood and youth, 419; of
middle life, 420 ; of advanced life, 420.

Diffusion of gases, 153.

Digestion, object of, 830; in stomach, 333;
extent of gastric, 340 ; influence of coffee
on, 377.

Dirt, composition of, 428.

Disguising bad smells, 436.

Disinfectants, 487 ; quicklime, 437; chlorine,
437 ; chloride of lime, 438 ; sulphurous
acid, 438 : charcoal, 439.

Double windows, 159.

Dough, water absorbed by, 257; effects of
kneading, 258 ; what makes it rise, 261 ;
raising by leaven, 262; raised by yeast,
206 ; acidity in, 266 ; sugar in, 267 ; alco-
hol in, 267 ; raised with eggs, 270.

Dress, 21, 35 ; colors of, 102.

E

Ebullition, 42 ; effects of pressure upon, 44

Eggs, composition of, 250 ; preservation of,
318.

Electricity, atmospheric, 164.

Emerson's injector, 197; ejector, 198.

Ether, luminous, vibrations of, 87.

Evaporation, 42 ; cooling eflects of, 46 ; rate
of, 159.

Eye, sensibility to colors, 97 ; parts of, 127,
128 ; minuteness of images in, 129 ; adap-
tation to light, 130 ; attected by conditions
of the system, 130 ; influence of reading
and writing upon, 131 ; cause of far-sight-
ed, 132; remedy of far-sightedness, 183;
cause of near-sighted, 134; remedy of
near-sighted, 135 ; cataract in, 136 ; influ-
ence of carbonic acid upon, 142 ; bad light
inflames, 144.

F
Faraday, Dr., 171.
Fats, see Oils.
Farina, 237.
Farina kettle, 45.
Fermentation, 260 ; conditions of, 260 ; dlf

fcrent kinds of, 260 ; spontaneous, 260.
Fibriu, 228.

INDEX.

447

Fire, kindling of; 50; risk oi^ IS; origin
of; 74.

Fireplace, form of, 62 ; action of, 62 ; econ-
omy of, 63 ; ventilation by, 192.

Flame, cause of, 50 ; illumination from, 106;
hollowness of, 110 ; length of, in gas burn-
ing, 123.

Flesh, composition of, 248 ; juice of, 249 ;
action of heat upon, 2S1 ; changes by
cooking, 282; loss of weight in, 282; best
plan of cooking, 283 ; common method
objectionable, 283; its juices acid, 371;
digestion of, 3S8.

Flour, white and dark, 236; evaporation
from, 236 ; changes in, 236 ; effects of its
preparations, 389.

Foods, why perishable, 300 ; conditions of
perishableness, 301 ; effects of, maybe un-
derstood, 325 ; periodic supply of, 337 ;
digestibility of, 341, 342, 343 ; changes in
mouth, 380 ; in stomach, 335 ; in intes-
tines, 344; constipating and laxative, 346;
final destination of, 347 ; produced by
forces, 348; produces animal force, 349;
unequal combustibility of, 351 ; heat-pro-
ducing and tissue-making, 352 ; replaced
by houses and clothing, 358 ; ash elements
of, 369 ; demand for variable, 408 ; daily
requirement of, 409.

Force, production of, destroys tissue, 361.

Freezing, artificial, 41 ; heat produced by,
42.

I'rost, cause of; 33.

Fruits, composition of, 243 ; dietetic effects
of, 391.

Fuel, influence of, 22 ; composition of, 49 ;
heating effects of, 54.

Furniture, colors of, 104.

G

Gas fixtures, 124.

Gas, illumination by, 119 ; sources of, 119 ;
composition of, 120 ; purification of, 119 ;
various sources of, 120 ; measurement of,
121 ; how burned, 122; contaminations of
air, by burning of, 123 ; disadvantages of
lighting by, 124; fixtures of, 124; is light-
ing by, injurious, 149.

Gas meter, 121.

Gastric juice, 338 ; its acid and ferment,
339; quantity of, 841.

Gelatin, 230.

Gingerbread, 271.

Glass, opaque to heat, 28.

Gluten, 229 ; quality of, 232.

Glycerine, 109.

Grain, grinding of, 234; structure of, 234;
sifting of, 235.

Grates, 64; combustion in, 64; Circular,
66 ; Arnotfs, 66 ; height of, 67.

Gum, artificial, 223; composition of, 223;
physiological effects of, 384.

H

Heat, from the sun, 18; from the stars, 18;
distribution of, 19; influence on vegeta-
tion, 19; distribution of animal, 20; in-
fluences man's development, 20; relation
to character, 21 ; diffusion of, 23 ; equi-
librium of, 23; expansion of, 23 ; weight
of, 24 ; radiation of, 27, 29, 30 ; transmis-

sion of, 28; absorption of, 29; exchanges
of, 31; conduction of, 34; convection o^
86 ; circulation of, 37 ; capacity for, 38 ;
latent, 39, 40, 41, 46; influence on the
body, 48 ; loss of, in rooms, 60 ; source of
in rooms, 61 ; amount of bodily, produced,
860.

Heating arrangements compared, 74.

Honey, 217.

Hot-air furnace, 70 ; ventilation by, 193.

Hot-water apparatus, 72.

Human body, purpose of, 348 ; constant
temperature of, 358 ; how it loses heat,
354 ; how it produces heat, 354 ; resources
against cold, 856 ; force exerted by, 860 ;
limited action over food, 892 ; its restricted
transforming power, 404.

Hunger, use of, 329.

Hydrogen, its office in fuel, 50; heating
powers of, 51.

Hydrometer, 255.

Illumination, artificial, 105 ; by ignition,
106 ; from burning gas, 106 ; simplicity of
the laws of, 107 ; by means of solids, 108 ;
by liquids, 112 ; by gases, 119.

Impure air, and contagion, 175 ; cholera and,
175 ; fevers and, 176 ; scrofula and, 177 ;
consumption and, 178; infant mortality
and, 178; undermines the health, 179;
morbid mental effects of, 180.

Indian corn, 239.

Intestines, juices of, 844; changes in, 345;
absorption from, 345.

Jelly, vegetable, 226.

Kneading, effects of, 258.

Lactometer, 255.

Lamps, 112 ; structure of, 113 ; astral, 113 ;
Carcel, 114 ; sinumbra, 113 ; not oil, 114 :
Newell's 117 ; study, 148.

Language, 22.

Lead, vessels for water, 212.

Leaves, nutritive properties of, 244.

Lenses, 84.

Lettuce, 245.

Light, exhilarating effects of, 76 ; theory of;
77 ; diffusion of, 78 ; reflection of, 79, 80 ;
scattered by air, 82 ; transmission of, 82 ;
refraction of, 82 ; wave theory of, 87 ; arti-
ficial, 105 ; from ignition, 105 ; measure-
ment of, 124 ; results of Ure and Kent, 126 ;
color of artificial, 137; injurious action
of artificial, 137.

Liquefaction, 37.

Liquors, alcoholic, 878 ; cannot replace wa-
ter in the system, 379, and animal heat,
379 ; Becker's observations, 879 ; not eco-
nomical, 88 ; stimulating effect, 380.

Looking-glass, 79.

Lyman's cold-air flue, 198 ; refrigerator 807

Macaroni, 233.
Malaria, 166.

M

448

INDEX.

Malic acid, 225.

Margaric acid, 109.

Margarine, 109.

Mastication, importance of, 333.

Meals, frequency in times of, 410 ; rest be-
fore, 411 ; state of mind during, 412 ; ex-
ercise after, 412 ; effects of excess at, 414.

Melting points, 38, 111.

Milk, composition of, 250; qualities of, 251,
252; cream of, 253; value of, 255; mineral
matter in, 256 ; spontaneous curdling of,
287 ; curdling with acids, 28T ; with ren-
net, 2SS; preserving, 314; etfects of, 381.

Mind, relation of, to matter, 361 ; its action
destroys the nerves, 365 ; wears the body,
366.

Moisture, in air, 157; in the air of rooms,
158 ; amount required in air, 183 ; the
supply of, 194.

Molasses, 221.

M. Mouries, 277.

Musical sounds, 85 ; scale, SO.

N

Night-air, 167.

Nitrogen, 154 ; lowers the combustibility of
food, 352.

Nitrogenous principles, properties of, 230 ;
names of, 231 ; destination of, 361.

Non-nitrogenous principles, different values
of, 395.

Nutrition, effects of, insufficient, 414.

Nutritive values, 395 ; scale of, 397 ; equi-
librium of, 396; milk, 398; wheat, 399;
adaptations of wheat, 399 ; coarse bread,
400.

O

Oats, 239.

Oils, proximate composition of, 109, 114;
fluidity of, 114; kerosene, 118; sylvic,
lis ; volatile and fixed, 223 ; sources of,
223 ; proportion of in articles of diet, 224 ;
ultimate composition of, 224; supply of,
in diet, 384; accumulation of, 384; in
stomach, 385; digestibility of, 336; rela-
tion of to nutrition, 387 ; to consumption,
387.

Oleaic acid, 109.

Oleaine, 109.

Onions, 247.

Oxygen, 49, 154 ; how it enters the system,
1.55 ; what it does in the body, 156 ; effect
of varying the quantity of, respired, 157 ;
consumed by respiration, 181 ; consumed
by combustion, 182; an exciter of decay,
802 ; destructive agency of, 350 ; action
of, upon tissues, 362.

Oxalic acid, 226.

Ozone, 164.

P

Paper-hangings, colors of, 103; poisonous
colors on, 173.

Parr, Thomas, 328.

Parsnips, 248.

Pectic acid, 226.

Peas, composition, 241 ; digestibility of, 390

Photometer, 125.

Pictures, hanging of, SI ; frames of, 104.

Poisons, used to color candy, 222 ; how di-
vided, 44\ ' how managed, 441.

Potatoes, composition of, 245 ; water in, 245;
starch in, 246 ; nutritive part of, 246 ; dry
matter of, 246 ; ash of, 247 ; changed by
cooking, 280.

Potash, 374.

Preservation, by exclusion of air, 302 ; Ap-
perfs method, 303; in canisters, 304; in
Spratt's cans, 305 ; at low temperatures,
8U6; by freezing, 306; in refrigerators,
307; fruits, 308; "by drying, 309; by anti-
septics, 311 ; by sugar, 313 ; by alcohol, 314.

Putrefaction, 259.

B

EeflectOTs, 146; blue, 147.
Eetina, image formed upon, 129; loss of sen-
sibility of, 144 ; paralysis of, 145.
Eice, composition of, 241.
Eoot^ edible, dietetic effects of, 391.
Eye, anatomy of, 235 ; compositioD of, 288.

Sago, 215.

SaUva, flow of, 831 ; properties of, 832 ; uses
of, 332 ; action in stomach, 340.

Salts, 369.

Shades, ground glass, 146; blue, 147; struc-
ture and mounting of, 147.

Simultaneous contrast of colors, 97.

Skin, structure of, 431 ; impurities of, 432 ;
cleansing of, 433.

Smoke, 59, 60.

Soap, how made, 425 ; hard and soft, 426 ;
water in, 426 ; varieties of, 427 ; its I'e-
ac.tion with water, 428.

Soda, 374.

Solution, 208.

Sound, transmission of, 85.

Soup, preparation and proj^erties of, 284;
effects of, 381.

Spectacles, 131; for the far-sighted, 133;
for the near-sighted, 135 ; suggestions in
selecting, 136 ; management, 137 ; pebble-
glass, 137 ; colored glasses for, 148.

Spectrum, 68.

Specific heat, 3S.

Spermaceti, 109.

Spitting, effects of, 834.

Starch, separation of, 213; proportion of,
214; grains, 214; sago, 215 ; tapioca, 215;
arrow-root, 215; corn-starch, 215; com-
position, 216 ; culinary changes of, 279 ;
physiological effects of, 383.

Steam, warming by, 73.

Steariue, 109.

Stearic acid, 109.

Stomach, figure of, 335; layers of, 335; mo-
tions of, 336 ; follicles of, 336 ; absorption
from, 846.

Stovepipe, 69.

Stove, Franklin, 64; self-regulating, 68; air-
tight, 68; best, 69; ventilation by, 193.

Sugar, proportion from various sources, 216 ;
artificially produced, 216; honey, 217;
cane, 218 ; grape, 218 ; sweetening power,
218 ; production of brown, 219 ; compo-
sition of brown, 219 ; fermentation of
brown, 220 ; contaminations of brown,
220 ; refined, 221 ; candy, 221 ; culinary
changes of, 278 ; as a preserver, 313 ; phy
Biological effects of, 383; refining of, 44.

INDEX.

449

Tapioca, 215.

Tartaric acid, 225.

Tea, 2S9 ; the shrub, 289 ; varieties, 2S9 ;
green and black, 290 ; conaposition of, 291 ;
how best made, 292 ; grounds, 292 ; adul-
teration, 293 ; physiological effects of, 377.

Teeth, 321 ; cleansing of, 435.

Temperature, facts of. 27 ; of body constant,
853 ; regulation of bodily, 357 ; diet and
daily changes of, 359.

Thermometer, 23, 24, 25, 26.

Turpentine, spirits of, 115.

Turnips, 248.

V

Vegetables, Influence of, iu diet, 390.

Vegetarian question, 402; statements of,
contrasted, 403, 404.

Ventiducts, 198.

Vermicelli, 283.

Vinegar, effects of, 892.

Vision, conditions of, 76; value of the sense
of, 126 ; how produced, 129 ; mechanism
of, 128 ; optical defects of. 131 ; limits of
perfect, 131 ; paralysis of the nerve oi^ 145.

Ventilation, of the person, 186 ; arrange-
ments for, 192 ; by the fireplace, 192 ; by
stoves, 193 ; by hot-air arrangements, 193 ;
points to bo secured in, 196 ; downward
current in, 197 ; ascending current in, 198 ;
by an additional flue, 200 ; of gas-burners,
201 ; of cellars, 202 ; should be provided
for in building, 202 ; involves loss of heat,
203.

W

Warming by steam, 73 ; by hot water, 72 ;
and ventilation best method of, 195.

Warming of rooms by air, 71.

Waste and supply, 228.

Water, its relations to heat, 39 ; evaporation
of, 42 ; boiling of, 42, 48 ; spheroidal state
of, 44 ; solvent powers of, 207 ; to hasten
solution, 208 ; its dissolved gases, 208, 209 ;
varieties of, 208 ; rain and snow, 209 ; or-
ganic contaminations of, 209 ; living in-
habitants of, 210 ; their use, 210 ; its min-
eral matter, 211 ; hard and soft, 212 ; in
contact with lead, 212; supply of rain,
213 : for culinary uses, 280 ; physiological
eff'ects of, 874, 875; influences digestion,
375 ; change of tissue, 376 ; proportions of
in foods, 394; as a cleansing agent, 422;
filtration of, 423 ; its dissolved impurities,
424.

Wave movements, 84.

Wax, 109.

Wheat, composition of, 232 ; gluten in, 232
water in, 233; mineral matter in, 237
nutritive value of, 899.

Wood, water in, 51 ; heating value of, 52
soft and hard, 52.

Woody fibre, 278.

Teast, brewer's. 262 ; a plant, 263 ; domestic
preparation of, 204 ; hops in, 265 ; drying
of, 265; bitterness of, 266; acidity ot,
266.

TESTIMONIALS.

OP THE OLASS-BOOE OF CHEMISTRY.

From the, N. Y. Commercial Advertiser.
Either for schools or for general reading we know of no elenaentary work
on Chemistry which in every respect pleases ns so much as this.

From the Albion.
A remarkably interesting and thoroughly popular work on Chemistry, re-
commended to the general reader by the clearness of its style, and its freedom
from technicalities.

From, the Boston Common School Journal.
We consider this Chart a great simplification of a somewhat confused «ib-
ject ; and we welcome it as another successful attempt, not only to simplify
truth, but to fix it in the mind by the assistance of the eye. If we were
called to teach the elements of chemistry in a school-room, we should be very
unwilling to lose the valuable assistance of this ingenious chart.

From the National Intelligencer.
Besides the fulness with which this work treats of the chemistry of agi-i-
eulture and the arts, we regard it as chiefly valuable for the clear account it

fives of the action of chemical agents upon the greatly varied functions of life,
t is veiy elementary and practical ; and whether for the use of schools or of
private libraries, it is an appropriate because an instructive and entertaining
book.

From the Scientific American.
Such a book in the present state of chemical science was demanded, but to
present the subject in such a clear, comprehensive manner, in a work of the
size before us, is more than we expected. The author has happily succeeded
in clothing his ideas in plain language — true eloquence^so as to render the
subject both interesting and easily comprehended. The number of men who
can write on science, and write clearly, is' small ; but our author is among that
number.

From, the Farmer and Mechanic.
A Class-Book of Chemistry for the use of beginners and young students,
which should be divested as much as possible of its tedious technicalities and
dry repulsiveness, so often attending their first eflbrts in this important study,
has long been a desideratum. To supply this need, the present volume is
fully adequate. It is designed as a popular introduction to the study of this
beautiful science, and presents it in such a manner as to win the attention and
engage the interest.

OF THE OHEMIOAL CHART.

From HoKACE Mann, President o/Antioch College.
I have been highly delighted by inspecting a Chart, shown to me by Mr. E.
L. Toumans, of New York, the object of which is to represent the ratios in
■which chemical atoms are combined to form compound bodies. The dift'erent
atoms are represented by square diagrams of different colors; and then the
compounds exhibit the exact number or numbers of the respective atoms
that unite to form them, each atom retaining its original color. Thus the eye
of the learner aids his memory ; and as the eye, in regard to all objects hav

YOUMANS' OHEMIOAL CHART.

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