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UNIVERSITY OF CALIFORNIA.
FROM THE LIBRARY OF
DR. JOSEPH LECONTE.
GIFT OF MRS. LECONTE.
No.
COSMOS:
SKETCH
OF A
PHYSICAL DESCRIPTION OP THE UNIVERSE.
BY
ALEXANDER VON HUMBOLDT.
VOL. I.
Katora vero rerwm vis atque majestas in omnibus momentisfide caret, si quis modoparta gut
ac non totam complectatur animo. — PLIN. H. N. lib. vii. c. 1.
TRANSLATED UNDER THE SUPERINTENDENCE OF
LIEUT.-COL. EDWARD SABINE, R.A., FOR. SEC. R.S.
IStrttion.
LONDON:
PRINTED FOB
LONGMAN, BROWN, GREEN, AND LONGMANS,
PATERNOSTEE ROW : AND
JOHN MURRAY, ALBEMARLE STREET.
1849.
PREFACE
TO THE SIXTH EDITION.
THE Editor's attention has been called to a passage in the
Preface of another translation of " Cosmos," published by
Mr. Bohn, wherein it is stated, that, in Mrs. SABINE'S
translation, passages are omitted, "sometimes amounting
to pages, simply because they might be deemed slightly
obnoxious to our national prejudices." In justice to the
respected Author of "Cosmos," the Editor is induced to
state, that no passage whatever of M. DE HUHBOLDT'S
writing has been omitted for the reason assigned. The
only intentional omission of even a single sentence of
M. DE HUMBOLDT'S writing is of a remark in Note 143
of Yolume I. (English translation), on the intermission of
observations of extraordinary magnetic disturbance at the
British Colonial Observatories, when such phsenomena occur
on a Sunday. Shortly after the publication of the original
•829
EDITOR'S PREFACE.
The two introductory discourses, which occupy 48 pages
in the German edition, have been rewritten by M. de
Humboldt himself in the French language, for the French
edition, in which they fill 78 pages. These were commu-
nicated to the Editor in their passage through the press,
and by the Author's desire have been followed in preference
to the corresponding portion of the German text, where
modifications or additions had been introduced.
Short as the interval has been, since Cosmos was written,
it has not been unmarked by the progress which has been
made in several branches of scientific knowledge. In
astronomy it has been distinguished by the discovery of a
new planet, Astrea, making the number of those bodies
belonging to our solar system twelve instead of eleven:
also of the two heads of Biela's comet, a phenomenon pre-
viously unknown. These discoveries, however, in no
respect affect the reasonings in Cosmos. The optical
means at the command of astronomers have also been
improved, by the construction of a telescope of unparalleled
dimensions by the Earl of Rosse : and the few trials which
have yet been made of its powers, lead to the belief, that the
greater part, if not the whole, of the nebulse will be resolved
by it into stars : happily the Author of Cosmos will himself
have an opportunity, in the succeeding volumes, of stating
the influence which a discovery of this nature may exercise
EDITOB'S PBEFACE*
upon the view which has been taken of the Celestial Phe-
nomena in the volume now published.
It has been M. de Humboldt' s wish, and kindly pressed
by him, that the Editor should add such notes as he might
think desirable, particularly in the branches of science in
which he has himself engaged : he has felt the propriety of
exercising this privilege very sparingly, and has only availed
himself of it in additions to Notes 132, 136, 139, 143,
158, 179, 373, and 382*.
Measures of itinerary distance are expressed in the origi-
nal work in geographical miles of 15 to the degree; these
have been converted in the translation into geographical
miles of 60 to the degree, as more consonant to English
usage. Measures of length are expressed by M. de Hum-
boldt usually in French feet and toises, v hic'i have been
retained in the translation; but the equivalent values in
English feet have been added whenever it has appeared de-
sirable to do so. In like manner the measures of tempera-
ture in Fahrenheit's scale have been given MI addition to
those in the Centesimal scale
"WOOLWICH, AUG. 22, 1846.
* A short addition has also heen made to Note 381 in the second edition}
and an index of names and subjects has been appended. — May 7, 1547.
CONTENTS.
P«ge
THE AUTHOR'S PREFACE . x?ii
INTRODUCTION.
On the different degrees of enjoyment offered by the aspect of Nature
and the study of her laws 3
Limits and method of exposition of the Physical description of the
universe . * . 42
GENERAL VIEW OF NATURE.
Introduction . . .67
CELESTIAL PHENOMENA.
Nebulae . 73
Sidereal systems 77
Our sidereal system 79
The solar system 81
Planets 82
Satellites 86
Comets 91
Aerolites 105
Zodiacal light .... 127
CONTENTS.
Page
The sun 134
Proper motions of stars • 135
Double and multiple stars 136
Distances, masses, and apparent diameters of stars . . .137
Variable aspect of the heavens 138
Nebulous milky-way ^ ' -f* r't f\i ?f 4\'^\ • * * -^
Successive propagation of light /•'»*• . • . 143
TERRESTRIAL PHENOMENA.
General view • 4 . . 145
Figure of the earth 154
Density of the earth . . j i! , . . . 167
Polar light, or aurora . . . . , . . ] 79
Reaction of the interior of the earth on its exterior . . .189
Earthquakes . . > ,;fj ;,, r,;«; .,,,,., -;j *<,,.', . . 191
Eruptions of gas . ...'., + I..A 205
Hot and cold springs 207
Mud volcanoes . , . . . , . . 211
Volcanoes . < » 213
Geological description of the earth's crust .. . . . .235
Fundamental classification of rocks ..... 236
Endogenous or erupted rocks .'• . • .. • . 238
Exogenous or sedimentary rocks 241
Metamorphic rocks .« .- .' . . . , 244
Artificial production of simple minerals . . . .256
Conglomerates ..•.*.•.. . . 257
General chemical constituents of rocks . . . .258
Palaeontology — Fossil organic remains 260
Palseozoology — Fossil animals 261
Palseophytology — Fossil plants * 268
Palseogeography— State of the surface of the globe at
different geological epochs 274
CONTENTS.
Page
Physical Geography — General view ...... 278
The land ........ . 280
The ocean ......... 294
The atmosphere — Meteorology ...... 304
Atmospheric pressure ....... 308
Climatology ......... 312
Limit of perpetual snow ....... 327
Hygrometry ......... 330
Atmospherical electricity ....... 333
Mutual dependence of meteorological phenomena . , 326
ORGANIC LIFE.
General view ....... • . . 338
Geography of plants and animals ...... 345
Man ........ ... 350
NOTES ...... . \
cxv
AUTHOR'S PREFACE.
IN the late evening of a varied and active life, I offer to tho
German public a work of which the undefined type has been
present to my mind for almost half a century. Often the
scheme has been relinquished as one which I could not hope
to realise, but ever after being thus abandoned, it has been
again, perhaps imprudently, resumed. In now presenting
its fulfilment to my contemporaries, with that hesitation which
a just diffidence of my own powers could not fail to inspire,
I would willingly forget that writings long expected are
usually least favourably received.
While the outward circumstances of my life, and an irre-
sistible impulse to the acquisition of different kinds of know-
ledge, led me to occupy myself for many years, apparently
exclusively, with sep arate branches of science, — descriptive
botany, geology, chemistry, geographical determinations,
and terrestrial ma gnetism, tending to render useful the ex-
AUTHOR'S PREFACE.
tensive journeys in which I engaged,-r-I had still throughout
a higher aim in view; I ever desired to discern physical
phsenomena in their widest mutual connection, and to com-
prehend Nature as a whole, animated and moved by inward
forces. Intercourse with highly-gifted men had early led me
to the- conviction, that without earnest devotion to particular
studies such attempts could be but vain and illusory. The
separate branches of natural knowledge have a real and
intimate connection, which renders these special studies
capable of mutual assistance and fructification : descriptive
botany, no longer restricted to the narrow circle of the de-
termination of genera and of species, leads the observer, who
traverses distant countries and lofty mountains, to the study
of the geographical distribution of plants according to dis-
tance from the equator and elevation above the level of the
sea. Again, in order to elucidate the complicated causes
which determine this distribution, we must investigate the
laws which regulate the diversities of climate and the meteo-
rological processes of the atmosphere ; and thus the observer,
earnest in the pursuit of knowledge, is led onwards from one
class of phenomena to another, by their mutual connection.
I have enjoyed one advantage which few scientific tra-
vellers have shared to an equal degree, in having seen not
merely coasts, and districts little removed from the margin of
the ocean, as in voyages of circumnavigation, — but in having,
moreover, traversed,, both in the new and the old world,
extensive continental districts presenting the most striking
contrasts ; on the one hand the tropical and alpine landscapes
of Mexico and South America, and on the other the dreary
uniformity of the steppes of Northern Asia. Such oppor-
tunities could not fail to encourage the tendencies of a mind
predisposed to generalisation, and were well fitted to animate
me to the attempt of treating in a special work our present
knowledge of the sidereal and terrestrial phenomena of the
universe in their empirical connection. " Physical Geogra-
phy/' the limits of which have been hitherto somewhat vaguely
defined, has been thus expanded, by perhaps too bold a plan,
into a scheme comprehending the whole material creation,
or into that of a " Physical Cosmography."
Such a work, if it would aspire to combine with scientific
accuracy any measure of success as a literary composition,
has to surmount great difficulties, arising from the very abun-
dance of the materials which the presiding mind must reduce
to order and clearness, while yet the descriptions of the varied
forms and phenomena of nature must not be deprived of
the characteristic traits which give them life and animation.
A series of general results would be no less wearisome than
a mere accumulation of detached facts. I cannot venture to
natter myself that I have adequately satisfied these various
conditions, or avoided the dangers which I have not failed
to perceive ; the faint hope which I cherish of success rests
on the particular favour which my countrymen have long
bestowed on a small work which I published, soon after my
return from Mexico, under the title of Ansichten der Natur,
and which treated some portions of physical geography, such
as the physiognomy of plants, savannahs, deserts, and cata-
racts, under general points of view. Doubtless the effect
which this small volume produced was far more attributable
to its indirect action, in awakening the faculties of young
and susceptible minds endowed with imaginative power, than
to any thing which it could itself impart. In my present
work, as in the one to which I have just alluded, I have
endeavoured to shew practically, that a certain degree of
scientific accuracy in the treatment of natural facts is not
incompatible with animated and picturesque representation.
Public discourses or lectures have always appeared to me
well adapted to test the success or failure of an endeavour
to unite detached branches of a general subject in a sys-
tematic whole ; with this view a series of lectures on the
Physical Description of the Universe, as I had conceived it,
was delivered both in Berlin and in Paris, in German and
in French. These discourses were not committed to writ-
ing ; and even the notes preserved by the diligence of some
attentive auditors have remained unknown to me ; nor have
I chosen to have recourse to them in the execution of the
AUTHOll S PREFACE.
present work, the whole of which, with the exception of a
portion of the Introduction, was written for the first time
in the years ]843 and 1844; the discourses in Berlin
having been delivered from November 1827 to April 1828,
previous to my departure for Northern Asia. A represen-
tation of the actual state of our knowledge, in which year
by year the acquisitions of new observations imperatively
demands the modification of previous opinions, must, as it
appears to me, gain in unity, freshness, and spirit, by being
definitely connected with some one determinate epoch.
The first volume contains a general view of nature, from
the remotest nebulae and revolving double stars to the
terrestrial phenomena of the geographical distribution of
plants, of animals, and of races of men ; preceded by some
preliminary considerations on i^ie different degrees of enjoy-
ment offered by the study of nature and the knowledge of
her laws ; and on the limits and method of a scientific ex-
position of the physical description of the Universe. I
regard this as the most important and essential portion of
my undertaking, as manifesting the intimate connection of
the general with the special, and as exemplifying in form
and style of composition, and in the selection of the results
taken from the mass of our experimental knowledge, the
spirit of the method in which 1 have proposed to myself to
conduct the whole work. In the two succeeding
VOL. i. c
I design to consider some of the particular incitements to
the study of Nature, — to treat of the history of the contem-
plation of the physical universe, or the gradual development
of the idea of the concurrent action of natural forces
co-operating in all that presents itself to our observation,-—
and lastly, to notice the specialities of the several branches
of science, of which the mutual connection is indicated in
the general view of nature in the present volume. References
to authorities, together with details of observation, have been
placed at the close of each volume, in the form of Notes.
In the few instances in which I have introduced extracts
from the works of my friends, they are indicated by marks
of quotation ; and I have preferred the practice of giving the
identical words, to any paraphrase or abridgment. The deli-
cate and often contested questions of discovery and priority,
so dangerous to introduce in an uncontroversial work, are
rarely touched upon : the occasional references to classical
antiquity, and to that liighly favoured transition period
marked by the great geographical discoveries of the fifteenth
and sixteenth centuries, have had for their principal motive,
the wish, which is occasionally felt when dwelling on general
views of nature, to escape from the more severe and dogma-
.
tical restraint of modern opinions, into the free and imagi-
native domain of earlier presentiments.
It has sometimes been regarded as a discouraging consi-
AUTHOR'S PREFACE.
deration, that whilst works of literature, being fast rooted
fa the depths of human feeling, imagination, and reason,
suffer little from the lapse of time, it is otherwise with
works which treat of subjects dependent on the progress of
experimental knowledge. The improvement of instruments,
and the continued enlargement of the field of observation,
render investigations into natural phenomena and physical
laws liable to become antiquated, to lose their interest, and
to cease to be read. Such reflections are not entirely desti-
tute of foundation; yet none who are deeply penetrated
with a true and genuine love of nature, and with a lively
appreciation of the true charm and dignity of the study of
her laws, can ever view with discouragement or regret that
which is connected with the enlargement of the boundaries
of our knowledge. Many and important portions of this
knowledge, both as regards the phenomena of the celestial
spaces and those belonging to our own planet, are already
based on foundations too firm to be lightly shaken ; although
in other portions, general laws will doubtless take the place
of those which are more limited in their application, new
forces will be discovered, and substances considered as
simple will be decomposed, whilst others will become
known. I venture, then, to indulge the hope, that the
present attempt to trace in animated characters such a
general view of the grandeur of nature, and of the perma-
nent relations and laws discernible through apparent fluc-
tuation, as the knowledge of our own age permits us to
form, will not be wholly disregarded ev*a at a future
period.
POTSDAM, Nov. 1844.
A PHYSICAL DESCRIPTION OF THE UNIVERSE.
ON THE DIFFERENT DEGREES OF ENJOYMENT OFFERED BY
THE ASPECT OF NATURE AND THE STUDY
OF HER LA.WS.
IN attempting, after a long absence from my country, to
unfold a general view of the physical phsenomena of the
globe which we inhabit, and of the combined action of the
forces which pervade the regions of space, I feel a double
anxiety. The matter of which I would treat is so vast, and
so varied, that I fear, on the one hand, to approach it in an
encyclopaedic and superficial manner, and on the other, to
weary the mind by aphorisms presenting only dry and dog«
matic generalities. Conciseness may produce aridity, whilst
too great a multiplicity of objects kept in view at the same
time leads to a want of clearness and precision in the
sequence of ideas.
But nature is the domain of liberty; and to give a lively
4 ASPECT OF NATURE. AND
picture of those ideas and those delights which a true and
profound feeling in her contemplation inspires, it is needful
that thought should clothe itself freely and without con-
straint in such forms and with such elevation of language,
as may be least unworthy of the grandeur and majesty of
creation.
If the study of physical phenomena be regarded in its
bearings, not on the material wants of man, but on his
general intellectual progress, its highest result is found in
the knowledge of those mutual relations which link together
the various powers of nature. It is the intuitive and intimate
persuasion of the existence of these relations which at once
enlarges and elevates our views, and enhances our enjoyment.
Such extended views are the growth of observation, of medi-
tation, and of the spirit of the age, which is ever reflected in
the operations of the human mind whatever may be their
direction. Those who by the light of history should trace
back through past ages the progress of physical knowledge to
its early and remote sources, would learn how for thousands
of years the human mind has laboured to lay hold of the
sure thread of the invariability of natural laws, amid the per-
plexities of ceaseless change ; and in so doing has gradually
conquered, so to speak, great part of the physical universe*
In following back this mysterious track, still the same image
of the Cosmos reappears, which, in its earlier revelation,
shewed itself as a presentiment of the true harmony and
order of the universe, and which, in our days, presents itself
as the fruit of long-continued and laborious observation.
Each of these two epochs of the contemplation of the ex-
ternal world has its own proper enjoyment : that belonging
to the first awakening of such reflections is well suited to
STUDY OP HER LAWS, 5
the simplicity of the earlier ages of the world ; to them the
undisturbed succession of the planetary movements, and the
progressive development of animal and vegetable life, were
pledges of an order yet undiscovered in other relations, but
of which they instinctively divined the existence. To us in
an advanced civilisation belongs the enjoyment of the precise
knowledge of phsenomena. From the time when man in
interrogating nature began to experiment, or to produce
phsenomena under definite conditions, and to collect and
record the fruits of experience, so that investigation might
no longer be restricted by the short limits of a single life,
the philosophy of nature laid aside the vague and poetic
forms with which she had at first been clothed, and has
adopted a more severe cliaracter : — she now weighs the value
of observations, and no longer divines, but combines and
reasons. Exploded errors may survive partially among the
uneducated, aided in some instances by an obscure and
mystic phraseology : they have also left behind them many
expressions by which our nomenclature is more or less dis-
figured ; while a few of happier, though figurative origin, have
gradually received more accurate definition, and have been
found worthy of preservation in our scientific language.
The aspect of external nature, as it presents itself in its
generality to thoughtful contemplation, is that of unity in
diversity, and of connection, resemblance and order, among
created things most dissimilar in their form; — one fair
harmonious whole. To seize this unity and this harmony,
amid such an immense assemblage of objects and forces,—
to embrace alike the discoveries of the earliest ages and those
of our own time, — and to analyse the details of phsenomena
without sinking under their mass, are efforts of human
6 DIFFERENT GRADATIONS OP
reason in the path wherein it is given to man to press towards
the full comprehension of nature, to unveil a portion of her
secrets, and, by the force of thought, to subject, so to speak,
to his intellectual dominion, the rough materials which he
collects by observation.
If we attempt to analyse the different gradations of enjoy-
ment derived from the contemplation of nature, we find, first,
an impression which is altogether independent of any know-
ledge of the mode of action of physical powers, and which
does not even depend on the particular character of the
objects contemplated. When we behold a plain bounded
by the horizon, and clothed by a uniform covering of any of
the social plants (heaths, grasses, or cistusses), — when we
gaze on the sea, where its waves, gently washing the shore,
leave behind them long undulating lines of weeds, — then,
while the heart expands at the free aspect of nature, there is
at the same time revealed to the mind an impression of the
y existence of comprehensive and permanent laws governing
the phenomena of the universe. The mere contact with
nature, the issuing forth into the open air, — that which by
an expression of deep meaning my native language terms in
das Freie, — exercises a soothing and a calming influence
on the sorrows and on the passions of men, whatever may be
the region they inhabit, or the degree of intellectual culture
which they enjoy. That which is grave and solemn in these
impressions is derived from the presentiment of order and
of law/ unconsciously awakened by the simple contact with
external nature ; it is derived from the contrast of the narrow
limits of our being with that image of infinity, which every
where reveals itself in the starry heavens, in the boundless
plain, or in the indistinct horizon of the ocean.
THE ENJOYMENT OF NATUEE. 7
Other impressions, better defined, affording more vivid
enjoyment and more congenial to some states of the mind,
depend more on the peculiar character and physiognomy of
the scene contemplated, and of the particular region of the
earth to which it belongs. They may be excited by views
the most varied ; either by the strife of nature, or by the
barren monotony of the steppes of Northern Asia, or by
the happier aspect of the wild fertility of nature reclaimed
to the use of man, fields waving with golden harvests, and
peaceful dwellings rising by the side of the foaming torrent .
for I regard here less the force of the emotion excited, than
the relation of the sensations and ideas awakened to that
peculiar character of the scene which gives them form and
permanence. If I might yield here to the charm of memory,
I would dwell on scenes deeply imprinted on my own recol-
lection— on the calm of the tropic nights, when the stars,
not sparkling, as in our climates, but shining with a steady
beam, shed on the gently heaving ocean a mild and planetary
radiance; — or I would recal those deep wooded valleys of the
Cordilleras, where the palms shoot through the leafy roof
formed by the thick foliage of other trees, above which their
lofty and slender stems appear in lengthened colonnades, " a
forest above a forest (l) •" — or the Peak of Teneriffe, when a
horizontal layer of clouds has separated the cone of cinders
from the world beneath, and suddenly the ascending current
of the heated air pierces the veil, so that the traveller, standing
on the very edge of the crater, sees through the opening the
vine-covered slopes of Orotava, and the orange gardens and
bananas of the coast. In such scenes it is no longer alone
the peaceful charm, of which the face of nature is never
wholly destitute, which speaks to our minds, but the peculiar
8 DIFFERENT GRADATIONS OP
character of the landscape, the new and beautiful forms of
vegetable life, the grouping of the clouds, and the vague
uncertainty with which they mingle with the neighbouring
islands, and the distant horizon half visible through the
morning mist. All that the senses but partially comprehend,
and whatever is most grand and awful in such romantic
scenes, open fresh sources of delight. That which sense
grasps but imperfectly offers a free field to creative fancy ;
the outward impressions change with the changing phases of
the mind ; and this without destroying the illusion, by which
we imagine ourselves to receive from external nature that
with which we have ourselves unconsciously invested her.
When far from our native country, after a long sea voyage,
we tread for the first time the lauds of the tropics, we ex-
perience an impression of agreeable surprise in recognising,
in the cliffs and rocks around, the same forms and sub-
stances, similar inclined strata of schistose rocks, the same
columnar basalts, which we had left in Europe : this identity,
in latitudes so different, reminds us that the solidification of
the crust of the earth has been independent of differences of
climate. But these schists and these basalts are covered
with vegetable forms of new and strange aspect. Amid the
luxuriance of this exotic flora, surrounded by colossal forms
of unfamiliar grandeur and beauty, we experience (thanks to
the marvellous flexibility of our nature) how easily the mind
opens to the combination of impressions connected with
each other by unperceived links of secret analogy. The
imagination recognises in these strange forms nobler deve-
opments of those which surrounded our childhood; the
colonist loves to give to the plants of his new home names
borrowed from his native land, and these strong untaught
THE ENJOYMENT OF NATURE. 9
impressions lead, however vaguely, to the same end as that
laborious and extended comparison of facts, by which the
philosopher arrives at an intimate persuasion of one indisso-
luble chain of affinity binding together all nature.
It may seem a rash attempt to endeavour to analyse into
its separate elements the enchantment which the great scenes
of nature exert over our minds, for this effect depends espe-
cially on the combination and unity of the various emotions
and ideas excited ; and yet if we would trace back this power
to the objective diversity of the phenomena, we must take a
nearer and more discriminating view of individual forms and
variously acting forces. The richest and most diversified
materials for such an analysis present themselves to the
traveller in the landscapes of Southern Asia, in the great
Indian Archipelago, and, above all, in those parts of the new
continent where the highest summits of the Cordilleras
approach the upper surface of the aerial ocean by which our
globe is enveloped, and where the subterranean forces which
elevated those lofty chains still shake their foundations.
Graphic descriptions of nature, arranged under the guid-
ance of leading ideas, are calculated not merely to please
the imagination, but also to indicate to us the gradation of
those impressions to which I have already alluded, from the
uniformity of the sea beach or of the steppes of Siberia, to
the rich luxuriance of the torrid zone. If we represent to
ourselves Mount Pilatus placed on the Shreckhorn (2), or the
Schneekoppe of Silesia on the summit of Mont Blanc, we
shall not yet have attained to the height of one of the
colossi of the Andes, the Chimborazo, whose height is twice
that of Etna ; and we must pile the Eigi or Mount Athos on
the Chimborazo, to have an image of the highest summit of
10 DIFFERENT GRADATIONS OF
the Himalaya, the Dhavalagiri. But although the moun-
tains of India far surpass in their astonishing elevation (long
disputed, but now confirmed by authentic measurements)
the Cordilleras of South America, they cannot, from their
geographical position, offer that inexhaustible variety of
phenomena by which the latter are characterised. The im-
pression produced by the grandest scenes of nature does not
depend exclusively on height. The chain of the Himalaya
is situated far without the torrid zone. Scarcely is a single
palm tree (3) found so far north as the beautiful valleys
of Kumaoon and Nepaul. In 28° and 34° of latitude,
on the southern slope of the ancient Paropamisus, nature
no longer displays that abundance of tree ferns, or arbo-
rescent grasses, of Heliconias, and of Orchideous plants,
which, within the tropics, ascend towards the higher plateaux
of the mountains. On the slopes of the Himalaya, under
the shade of the Deodar and the large-leaved oak peculiar
to these Indian Alps, the rocks of granite and of mica schist
are clothed with forms closely resembling those which cha-
racterise Europe and Northern Asia ; the species indeed arB
not identical, but they are similar in their aspect and phy-
siognomy, comprising junipers, alpine birches, gentians, par*
nassias, and prickly species of Eibes (4). The chain of the
Himalaya is also wanting in those imposing volcanic pheno-
mena, which, in the Andes and in the Indian Archipelago,
often reveal to the inhabitants, in characters of terror, the
existence of forces residing in the interior of our planet.
Moreover, on the southern declivity of the Himalaya, where
the vapour-loaded atmosphere of Hindostan deposits its
moisture, the region of perpetual snow descends to a zone
of not more than 11000 or 12000 (11700 or 12800 Eng.)
THE ENJOYMENT OF NATURE. 11
feet of elevation : thus the region of organic life ceases at a
limit nearly three thousand feet (5) below that which it
reaches in the equinoctial portion of the Cordilleras.
But the mountainous regions which are situated near the
equator possess another advantage, to which attention has
not been hitherto sufficiently directed. They are that part of
our planet in which the contemplation of nature offers in
the least space the greatest possible variety of impressions.
In the Andes of Cundinamarca, of Quito, and of Peru, fur-
rowed by deep barrancas, it is permitted to man to contem-
plate all the families of plants and all the stars of the
firmament. There, at a single glance, the beholder sees lofty
feathered palms, humid forests of bamboos, and all the beau
tiful family of Musacese ; and, above these tropic forms, oaks,
medlars, wild roses, and umbelliferous plants, as in our Euro-
pean homes ; there, too, both the celestial hemispheres are
open to his view, and, when night arrives, he sees displayed
together the constellation of the Southern Cross, the Mi
gollanic clouds, and the guiding stars of the Bear which circle
round the Arctic pole. There, the different climates of the
earth, and the vegetable forms of which they determine the
succession, are placed one over another, stage above stage ;
and the laws of the decrement of heat are indelibly written
on the rocky walls and the rapid slopes of the Cordilleras, in
characters easily legible to the intelligent observer. Not to
weary the reader with details of phsenomena which I long since
attempted (6) to represent graphically, I will here retrace only a
few of the more comprehensive features which, in their com-
bination, form those pictures of the torrid zone. That which,
in impressions received solely by our senses, partakes of an
uncertainty, similar to the effect of the misty atmosphere,
DIFFERENT GRADATIONS OP
waich, in mountain scenery, renders at times every outline
dim and indistinct, — when scrutinised by reasoning on the
cause of the phenomena, may be clearly viewed and correctly
resolved into separate elements, to each of which its own
individual character is assigned ; and thus, in the study of
nature, as well as in its more poetic description, the picture
gains in vividness and in objective truth by the well and
sharply-marked lines which define individual features.
Not only is the torrid zone, through the abundance and
luxuriance of its organic forms, most rich in powerful im-
pressions,— it has also another advantage, even greater
in reference to the chain of ideas here pursued-, in the
uniform regularity which characterises the succession both
of meteorological and of organic changes. The well-marked
lines of elevation which separate the different forms of
vegetable life, seem there to offer to our view the inva-
riability of the laws which govern the celestial move-
ments, reflected as it were in terrestrial phenomena. Let
us dwell for a few moments on the evidences of this regu-
larity, which is such, that it can even be measured by
scale and number.
In the burning plains which rise but little above the level
of the sea, reign the families of Bananas, of Cycadeae, and of
Palms, of which the number of species included in our floras
of the tropical regions has been so wonderfully augmented
in our own days by the labours of botanic travellers. To
these succeed, on the slopes of the Cordilleras, in mountain
valleys, and in humid and shaded clefts of the rocks, tree
ferns raising their thick cylindrical stems, and expanding
their delicate foliage, whose lace-like indentations are seen
against the deep azure of the sky. There, too, flourishes
THE ENJOYMENT OP NATURE. 13
the Cinchona, whose fever-healing bark is deemed the more
salutary the more often the trees are bathed and refreshed by
the light mists which form the upper surface of the lowest
stratum of clouds. Immediately above the region of
forests the ground is covered with white bands of flower-
ing social plants, small Aralias, Thibaudias, and myrtle-
leaved Andromedas. The Alp rose of the Andes, the mag-
nificent Befaria, forms a purple girdle round the spiry
peaks. On reaching the cold and stormy regions of the
Paramos, shrubs and herbaceous plants, bearing large and
richly-coloured blossoms, gradually disappear, and are suc-
ceeded by a uniform mantle of monocotyledonous plants.
This is the grassy zone, where vast savannahs (on which
graze lamas, and cattle descended from those brought
from the old world) clothe the high table lands and the
wide slopes of the Cordilleras, whence they reflect afar a
yellow hue. Trachytic rocks, which pierce the turf, and rise
high into those strata of the atmosphere which are supposed
to contain a smaller quantity of carbonic acid, support only
plants of inferior organization — Lichens, Lecideas, and the
many-coloured dust of the Lepraria, forming small round
patches on the surface of the stone. Scattered islets of
fresh-fallen snow arrest the last feeble traces of vegetation,
and are succeeded by the region of perpetual snow, of
which the lower limit is distinctly marked, and undergoes ex-
tremely little change. The elastic subterranean forces strive,
for the most part in vain, to break through the snow-clad
domes which crown the ridges of the Cordilleras ; — but even
where these forces have actually opened a permanent channel
of communication with the outer air, either through crevices
or circular craters, they rarely send forth currents of lava, more
14 DIFFERENT GRADATIONS OF
often erupting ignited scoriae, jets of carbonic acid gas and
sulphuretted hydrogen, and hot steam. The contemplation of
this grand and imposing spectacle appears to have produced
on the minds of the earlier inhabitants of those countries
only vague feelings of astonishment and awe. It might
have been imagined, that, as we have before said, the well-
marked periodic return of the same phenomena, and the
uniform manner in which they group themselves in ascending
zones, would have rendered easier a knowledge of the laws of
nature; but so far as history and tradition enable us to
trace, we do not find that the advantages possessed by those
favoured regions have been so improved. Recent researches
have rendered it very doubtful whether the primitive seat of
Hindoo civilisation, one of the most wonderful phases of the
rapid progress of mankind, were really within the tropics.
Airy ana Vaedjo, the ancient cradle of the Zend, was to the
north-west of the Upper Indus ; and after the separation of
the Iraunians from the Brahminical institution, it was in a
country bounded by the Himalaya and the small Yindhya
chain, that the language which had previously been common
to the Iraunians and Hindoos, assumed among the latter
(together with manners, customs, and the social state), an
individual form in the Magadha, or Madliya Desa (7). The
extension of the Sanscrit language and civilisation to its
south-easternmost limit, far within the torrid zone, has
been described by my brother, Wilhelin von Humboldt, in
his great work on the Kawi, and other languages of kindred
structure (8).
Notwithstanding the greater difficulties with which in
more northern climates, the discovery of general laws was
surrounded, by the excessive complication of phenomena, aad
THE ENJOYMENT OF NATURE. 15
the perpetual local variations, both in the movements of the
atmosphere and in the distribution of organic forms, it was
to the inhabitants of the temperate zone that a rational
knowledge of physical forces first revealed itself. It is from
this northern zone, which has shown itself favourable to the
progress of reason, to the softening of manners, and to
public liberty, that the germs of civilisation have been
imported into the torrid zone, either by the great movements
of the migration of races, or by the establishment of colonies,
very different in their institution in modern times from those
of the Greeks and Phoenicians.
In considering the influences which the order and succes-
sion of phsenomena may have exercised on the greater or less
facility of recognizing their producing causes, I have indicated
that important point in the contact of the human mind with
the external world, at which there is added to the charm
attendant on the simple contemplation of nature, the enjoy-
ment springing from a knowledge of the laws which govern
the order and mutual relations of phsenomena. Thenceforth
the persuasion of the existence of an harmonious system of
fixed laws, which was long the object of a vague intuition,
gradually acquires the certainty of a rational truth, and man,
as our immortal Schiller Jias said — " Amid ceaseless change,
seeks the unchanging pole (9)"
In order to reascend to the first germ of this more
thoughtful enjoyment, we need only cast a rapid glance on
the earliest glimpses of the Philosophy of Nature, or of the
ancient doctrine of the Cosmos, We find amongst the most
savage nations (and my own travels have confirmed the
truth of this assertion), a secret and terror-mingled presenti-
ment of the unity of natural forces, blending with the dim
voi,. i. D
16 DIFFERENT GRADATIONS OP
perception of an invisible and spiritual essence manifesting
itself through these forces, whether in unfolding the flower
and perfecting the fruit of the food-bearing tree, or in the
subterranean movements which shake the ground, and the
tempests which agitate the atmosphere. A bond connecting
the outward world of sense with the inward world of thought
may be here perceived ; the two become unconsciously con-
founded, and the first germ of a philosophy of nature is
developed in the mind of man without the firm support of
observation. Amongst nations least advanced in civilisa-
tion, the imagination delights itself in strange and fantastic
creations. A predilection for the figurative influences
both ideas and language. Instead of examining, men con
tent themselves with conjecturing, dogmatising, and inter-
preting supposed facts which have never been observed.
The world of ideas and of sentiments does not reflect back
the image of the external world in its primitive purity.
That which in some regions of the earth, and among a small
number of individuals gifted with superior intelligence, mani-
fests itself as the rudiment of natural philosophy, appears
in other regions and among other races of mankind as
the result of mystic tendencies and instinctive intuitions,
It is in the intimate communion with external nature, and
the deep emotions which it inspires, that we may also trace,
in part, the first impulses to the deification and worship ol
the destroying and preserving powers of nature. At a
later period of human civilisation, when man, having passed
through different stages of intellectual development, has
arrived at the free enjoyment of the regulating power of
reflection, and has learned, as it were by a progressive enfran-
chisement, to separate the world of ideas from that of the
THE ENJOYMENT OF NATURE. 17
perceptions of sense, a vague presentiment of the unity of
natural forces no longer suffices him. The exercise of
thought then begins to accomplish its noble task, and,
by observation and reasoning combined, the students of
nature strive with ardour to ascend to the causes of phse-
nomena.
The history of science teaches us how difficult it has been
for this active curiosity always to produce sound fruits.
Inexact and incomplete observations have led, through false
inductions, to that great number of erroneous physical views
which have been perpetuated as popular prejudices among
all classes of society. Thus, by the side of a solid and scien-
tific knowledge of phsenomena, there has been preserved a
system of pretended 'results of observation, the more diffi-
cult to shake because it takes no account of any of the
facts by which it is overturned. This empiricism — melan-
choly inheritance of earlier times — invariably maintains
whatever axioms it has laid down; it is arrogant, as is
every thing that is narrow-minded ; wliilst true physical
philosophy, founded on science, doubts because it seeks to
investigate thoroughly, — distinguishes between that which is
certain and that which is simply probable, — and labours
incessantly to bring its theories nearer to perfection by
extending the circle of observation. This assemblage of
incomplete dogmas bequeathed from one century to another, —
this system of physics made up of popular prejudices, — is not
only injurious because it perpetuates error with all the
obstinacy of the supposed evidence of ill-observed facts,
but also because it hinders the understanding from rising to
the level of the great views of nature. Instead of seeking to
discover the mean state, around which, in the midst of
IS ERRORS ARISING FROM
apparent independence and irregularity, the phenomena really
and invariably oscillate, this false science delights in multi-
plying apparent exceptions to the dominion of fixed laws ;
and seeks, in organic forms and in the phsenomena of nature,
other marvels than those presented by internal progressive
development, and by regular order and succession. Ever
disinclined to recognise in the present the analogy of the
past, it is always disposed to believe the order of nature
suspended by perturbations, of which it places the seat, as if
by chance, sometimes in the interior of the earth, sometimes
in the remote regions of space.
It is the special object of this work to combatHhese
errors, which, originating in vicious empiricism and de-
fective induction, have survived even amongst the higher
classes of society (often by the side of much literary
cultivation), and thus to augment and ennoble the enjoy-
ments which nature affords, by imparting a deeper view into
her inner being. Such enjoyment (as our Carl Bitter has
well shewn) is highest, when the whole mass of facts col-
lected from different regions of the earth is comprehended
in one glance, and placed under the dominion of intel-
lectual combination. Increased mental cultivation, in all
classes of society, has been accompanied by an increased
desire for the embellishment of life through the augmenta-
tion of the mass of ideas, and of the means of generalising
those already received. Nor is such a desire unworthy of
notice in reference to vague accusations, which represent the
ininds of men, in this our age, as occupied almost exclusively
by the material interests of life.
I touch, almost with regret, on a fear which seems to me
to arise either from a too limited view, or from a certain
VICIOUS EMPIRICISM. 19
feeble sentimentality of character; I mean the fear that
nature may lose part of her charms, and part of the magic of
her power over our minds, when we begin to penetrate her
secrets, — to comprehend the mechanism of the movements
of the heavenly bodies, — and to estimate numerically the in-
tensity of forces. It is true that, properly speaking, the
forces of nature can only exert over us a magical power, by
their action being to our minds enveloped in obscurity, and
beyond the conditions of our experience. Even supposing
that they would thus be the better fitted to excite our ima-
gination, that assuredly is not the faculty which we should
prefer to evoke, whilst engaged in those laborious subsidiary
observations, which have for their ultimate object the know-
ledge of the grandest and most admirable laws of the uni-
verse. The astronomer occupied in determining, by the aid
of the heliometer, or of the doubly refracting prism (10), the
diameter of planetary bodies ; or patiently engaged for years
in measuring the meridian altitudes of certain stars and
their distances apart, — or, searching for a telescopic comet
among a crowded group of nebulse, does not feel his ima-
gination more excited, (and this is the very warrant of the
accuracy of his work,) than the botanist who is intent on
counting the divisions of the calix, the number of sta-
mens, or the sometimes connected, and sometimes indepen-
dent, teeth of the capsule of a moss. And yet it is these
precise angular measurements, and minute organic relations,
which prepare and open the way to the higher knowledge of
nature and of the laws of the universe. The physical phi-
losopher (as Thomas Young, Arago, and Eresnel,) measures
with admirable sagacity the waves of light of unequal length,
which by their interferences reinforce or destroy each other,
even in respect to their chemical action : the astronomer
20 ERRORS ARISING FROM
armed with powerful telescopes, penetrates space, and con-
templates the satellites of Uranus at the extreme confines
of our solar system *, or (like Herschel, South, and Struve)
decomposes faintly sparkling points into double stars, differ-
ing in colour and revolving round a common centre of
gravity ; the botanist discovers the constancy of the gyratory
motion of the chara in the greater number of vegetable cells,
and recognises the intimate relations of organic forms in
genera, and in natural families. Surely the vault of heaven
studded with stars and nebulae, and the rich vegetable
covering which mantles the earth in the climate of palms,
can scarcely fail to produce on these laborious observers im-
pressions more imposing, and more worthy of the majesty
of creation, than on minds unaccustomed to lay hold of the
great mutual relations of phsenomena. I cannot therefore
agree with Burke when he says, that our ignorance of natural
things is the principal source of our admiration, and of the
feeling of the sublime. The illusion of the senses, for exam-
ple, would have nailed the stars to the crystalline dome of
the sky ; but astronomy has assigned to space an indefinite
extent ; and if she has set limits to the great nebula to which
our solar system belongs, it has been to shew us further and
further beyond its bounds, (as our optic powers are in-
creased,) island after island of scattered nebulae. The feel-
ing of the sublime, so far as it arises from the contemplation
of physical extent, reflects itself in the feeling of the infinite
which belongs to another sphere of ideas. That which it
offers of solemn and imposing it owes to the connexion just
indicated ; and hence the analogy of the emotions and of
the pleasure excited in us in the midst of the wide sea ;
[* Written, the reader will remember, before the discovery of the planet
Le Verrier.— ED.]
VICIOUS EMPIRICISM. 21
or on some lonely mountain summit, surrounded by semi-
transparent vaporous clouds ; or, when placed before one of
those powerful telescopes which resolve the remoter nebula
into stars, the imagination soars into the boundless regions
of universal space.
The mere accumulation of unconnected observations of
details, without generalisation of ideas, may no doubt have
conduced to the deeply-rooted prejudice, that the study of
the exact sciences must necessarily tend to chill the feelings,
and to diminish the nobler enjoyment attendant on the
contemplation of nature. Those who in the present day
cherish such an error in the midst of rapid progress and
new vistas of knowledge, fail in appreciating the value of
every enlargement of the sphere of intellect, and of the
tendency to rise from separate facts to results of a higher
and more general character. To this fear of sacrificing,
under the influence of scientific reasoning, something of the
free enjoyment of nature, is often added another fear, namely,
that the extent of the field of natural knowledge forbids to
jthe greater part of mankind access to its enjoyments. It is
true that in the midst of the universal fluctuation of forces,
and of the seemingly inextricable network of organic life,
alternately developed and destroyed, every step in the more
intimate knowledge of nature leads to the entrance of new
labyrinths ; but to those engaged in the pursuit the very
multiplicity of paths presenting themselves, the exciting
effort of divining the true one, the presentiment of fresh
mysteries to be unveiled, are all full of enjoyment. The
discovery of each separate law indicates, even if it does not
reveal, to the intelligent observer the existence of some
other higher and more general law. Nature, according
22 ERRORS ARISING FROM
to the definition of a celebrated physiologist (H), and as
the word itself indicated with the Greeks and Romans, is
" that which is in perpetual growth and progress, and which
subsists in continual change of form and internal deve-
lopment." The series of organic types presented to our
view gradually gains enlargement and completenesses pre-
viously unknown regions are penetrated and surveyed, — as
living organic forms are compared with those which have
disappeared in the great revolutions which our planet has
undergone, — as microscopes have been rendered more per-
fect, and have been more extensively employed. Amid this
immense variety of animal and vegetable forms and their
transformations, we see, as it were, incessantly renewed the
primordial mystery of all organic and vital development,
the problem of metamorphosis, so happily treated by
Goethe, — a solution corresponding to our intuitive desire
to arrange all the varied forms of life under a small
number of fundamental types. As observation, continually
increasing, reveals yet more and more of the treasures of
nature, man becomes imbued with the intimate con-
viction that, whether we regard the surface or the in-
terior of the earth, the depths of the ocean, or the
celestial spaces, the scientific conqueror will never complain
with the Macedonian, that there are no fresh worlds to sub-
ject to his dominion (12). General considerations, whether
relating to matter agglomerated in the celestial bodies, or to
the distribution of organic life on the surface of the earth, are
not only in themselves more attractive than special studies,
but they also offer peculiar advantages to the greater number
of men who can devote but little time to such occupations.
The different branches of the study of natural history are
VICIOUS EMPIRICISM. 23
only accessible in certain positions of social life; nor do
they present the same charm in all seasons and in all climates.
If our interest is fixed exclusively upon one class of objects,
the most animated accounts of travellers from distant regions
will have no attraction for us, unless they happen to touch
on the chosen subjects of our studies.
As the history of nations, if it were possible that it could
always successfully trace back events to their true causes,
would no doubt solve to us the ever-recurring enigma of the
alternately impeded and accelerated progress of human
society ; so, likewise, the physical description of the uni-
verse, the science of the Cosmos, if grasped by a powerful
intellect, and based on the knowledge of all that has been
discovered up to a given epoch, would remove many of those
apparent contradictions, which the complication of pheno-
mena, caused by a multitude of simultaneous perturbations,
presents at the first glance.
The knowledge of laws, whether revealing themselves in
the ebb and flow of the ocean, in the paths of comets, or in
the mutual attractions of multiple stars, renders us more
conscious of the " calm of nature :" and we might say that
" the discord of the elements," — that long-cherished phan-
tasm of the human mind in its earlier and more intuitive
contemplations — is gradually dispelled as science extends its
empire. General views lead us habitually to regard each
organic form as a definite part of the entire creation, and to
recocj nise, in the particular plant or animal, not an isolated
species, but a form linked in the chain of being to other
forms living or extinct. They assist us in comprehending
the relations which exist between the most recent discoveries,
and those which have prepared the way for them. They en-
24 NECESSITY OP GENERAL
large the bounds of our intellectual existence, and while we
ourselves may be living in retirement they place us in commu-
nication with the whole globe. Under their guidance we
follow with eager interest the investigations of travellers and
observers in every variety of climate. We accompany, in
thought, the bold navigators of the polar seas ; and, amidst
the realm of perpetual ice, view with them that volcano of
the antarctic pole, whose jfires are seen from afar, even at the
season when no night favours their brightness. The intellec-
tual objects, both of these adventurous voyages, and of those
stations of observations recently established in almost every
latitude, are not strange to us ; for we can comprehend some
of the wonders of terrestrial magnetism, and general views
lend an irresistible attraction to the consideration of those
magnetic storms, which embrace the whole circumference of
ttuLeacth at the same instant of time.
Let me be permitted to elucidate the preceding considera-
tions, by touching on a few of those discoveries whose
importance cannot be justly appreciated without some
general knowledge of physical science. For this purpose I
will select instances which have recently attracted much
attention. Who, without some general knowledge of the
ordinary paths of comets, could perceive how fruitful in
consequences was Encke's discovery, by which a comet, that
in its elliptic orbit never passes out of our planetary sys-
tem, reveals the existence of an ethereal fluid obstructing its
tangential force ? A rapidly-spreading half-knowledge brings
scientific results ill understood into the conversation of the
day, and the supposed danger of collision between two
heavenly bodies, or of a deterioration of climate from cos-
mica! causes, are again brought forward in a new and more
PHYSICAL KNOWLEDGE. 25
deceptive form. Clear views of nature, even if merely his-
torical, are sufficient preservatives against these dogmatizing
fancies. The history of the atmosphere, and of the annual
variations of its temperature, extends already sufficiently far
back to shew that these consist in repeated small oscillations
around the mean temperature of a station, thereby dispelling
the exaggerated fear of a general and progressive deteriora-
tion of the climates of Europe. Encke's comet, which is
one of the three interior comets, completing its course
in 1200 days, must, from its position and the form of its
path, be as harmless to the inhabitants of our globe as
Halley's great comet of 1759 and 1835, which has a perioi.
of seventy-six years. The path of another comet of short
period, Biela's, which completes its course in six years,
does, indeed, intersect the earth's path, but it can only
approach us when its perihelion coincides with our winter
solstice.
The quantity of heat received by a planetary body (the
unequal distribution of which determines the great meteoro-
logical processes of our atmosphere) depends conjointly on
the light-evolving power of the sun (i. e. the nature of its
surface, or the state of its gaseous covering), and on the re-
lative positions of the sun and planet. There are, indeed,
periodical variations, which the form of the earth's orbit and
the obliquity of the ecliptic undergo in obedience to flie
universal law of gravitation ; but these changes are so slow,
and restricted within such small limits, that their thermic
effects would hardly be appreciable by our present ther-
mometric instruments in many thousands of years . Supposed
cosmical causes of diminished temperature or moisture, or
of epidemic diseases, — of which the idea has been enter-
26 NECESSITY OF GENERAL
tained in modern times, as well as in the middle ages, — are,
therefore, wholly beyond the range of our actual experimental
knowledge.
I may also borrow from physical astronomy other examples,
of which the grandeur and the interest cannot be felt without
some general knowledge of the forces which animate the
universe, and may adduce the elliptic revolutions of many
thousands of double stars, or suns, around each other, or
rather around their common centre of gravity, revealing
the existence of the Newtonian attraction in those distant
worlds; — the periodical abundance or paucity of spots on the
eun (openings in the opaque but luminous envelope of the
solid nucleus) ; — and the periodic appearance, observed for
some years past about the 12th or 13th of November and the
10th or llth of August, of countless multitudes of shooting
stars, moving with planetary swiftness, which probably form
a belt of asteroids intersecting the orbit of the earth.
Descending from the skies to the earth, we may notice
how the oscillations of a pendulum in air (the theory of
which has been perfected by BesseFs acuteness) have thrown
light on the internal density, I might say on the degree of
solidification, of our planet ; they have also served, in a cer-
tain sense, to sound terrestrial depths, conveying informa-
tion respecting the geological nature of strata otherwise
inaccessible. In this manner, as well as in others, we are
enabled to trace a striking analogy between the production
of granular rocks in lava currents which have flowed down
the slopes of active volcanoes, and those granites, porphyries,
and serpentines, which, issuing from the interior of the earth,
have broken, as eruptive rocks, through the secondary
strata, modifying them by contact, hardening them by the
PHYSICAL KNOWLEDGE. 27
introduction of silex, or changing them into dolomite, or
causing in them the formation of crystals of various kinds.
The elevation of sporadic islets, of domes of trachyte, and
of cones of basalt, by the elastic forces which emanate from
the fluid interior of our planet, conducted the first geologist
of our age, Leopold von Buch, to the theory of the elevation
of continents and of mountain chains generally. This ac-
tion of subterranean forces, in breaking through and elevat-
ing sedimentary rocks, of which the coast of Chili has
offered a recent example, shows us how the oceanic shells
which M. Bonpland and myself found on the ridge of the
Andes, at an elevation of more than 4600 metres (about
15100 English feet), may have been conveyed there, not
by a rise of the ocean, but by volcanic agencies elevating
into ridges the heat-softened crust of the globe.
I use the term volcanic agency in its most general sense,
applying it, whether on the earth or on her satellite the
moon, to that reaction of the interior of a planet on its
crust, which on our globe at least has been very different
at different epochs. Those who are unacquainted with the
experiments which show the increase of internal heat at
increasing depths in the earth to be so rapid, that granite (13)
is supposed to be in a state of fusion about twenty geogra-
phical miles below the surface, cannot have a clear compre-
hension of the causes of the simultaneity of volcanic eruptions
occurring at great distances apart, — of the extent and in-
tersection of circles of commotion in earthquakes, — of
the constancy of temperature and of chemical composition
in thermal springs during many years of observation, — or
of the difference of temperature of Artesian wells of unequal
depth, And yet the knowledge of the internal terrestrial
28 NECESSITY OP GENERAL
heat throws a faint light on the early history of our planet,
by showing the possibility of a generally prevalent tropical
climate, arising from the heat issuing from crevices in the
recently oxydized crust of the globe ; a state of tilings in
which the temperature of the atmosphere would depend far
more on the reaction of the interior of the planet upon its
crust, than on its relative position in respect to the central
body or sun.
The cold zones of the earth present to the researches of
the geologist many buried products of a tropical climate :—
in the coal formations, upright stems of palms, coniferse,
and tree ferns, goniatites, and fishes with rhornboidal ena-
melled scales (41) ; — in the Jura limestone, colossal skeletons of
crocodiles and long-necked Plesiosauri, Planulites, and stems
of Cycadese; — in the chalk, small Poly thalainia and Bryozoa,
in part identical with some of our living marine animals; — in
tripoli or polishing slate, in semi-opal, and in the substance
called mountain meal, agglomerated masses of fossil infu-
soria, such as Ehrenberg's all-animating microscope has
disclosed to us ;— and lastly, in transported soils and in caves,
bones of hyenas, lions, and elephantine Pachydermata. An
enlarged knowledge of other natural phsenomena renders
these objects no longer an occasion for mere barren curiosity
and wonder, but for intelligent study and profound medita-
tion.
The multiplicity of diverse objects^ which I have here
•purposely crowded together, leads directly to the question,
whether general views of nature can possess a sufficient
degree of clearness, without a deep and earnest application
to separate studies, whether of descriptive natural history, of
geology, of physics, or of mathematical astroromy ?' In
PHYSICAL KNOWLEDGE. 29
attempting a reply, we must discriminate carefully between
the teacher who undertakes the selection, combination, arid
presentation of the results, and the person who receives
them, when thus presented, as something not sought out by
himself, but communicated to him by another To the first,
some exact knowledge of the special is indispensably neces-
sary ; before proceeding to the generalisation of ideas, he
should have wandered long in the domains of the separate
sciences, and have himself observed, experimented, and mea-
sured. I cannot deny that where positive knowledge is
wanting in the reader, general results, which in their mutual
connection lend so great a charm to the contemplation of
nature, are not susceptible of being always developed with
equal clearness ; but, nevertheless, I permit myself the plea-
sure of thinking, that in the work which I am preparing,
the greater number of the truths presented will admit of
being exhibited without the necessity of always reascending
to fundamental principles and ideas. The picture of nature
thus drawn, even though some part of its outline may be
less sharply defined, will still possess truth and beauty, and
will still be suited to enrich the intellect, to enlarge the
sphere of ideas, and to nourish and vivify the imagina-
tion.
Our scientific literature has been reproached, and perhaps
iiot without justice, with not sufficiently separating the gene-
ral from the special — the view of that already gained, from the
long recital of the means which have led to it. This reproach
even led the greatest poet of our age (15) to exclaim with
impatience, that " the Germans have the gift of rendering
the sciences inaccessible." Whilst the scaffolding stands,
it obscures the effect of the finished building. Who can
30 NECESSITY OF GENERAL
doubt that the -uniformity of figure observed in the distribu-
tion of our continental masses, by which they taper towards
the south, and spread out in breadth towards the north
(a fact or law on which the distribution of climates, the
prevailing direction of atmospheric and oceanic currents, and
the great extension of tropical forms into the southern tem-
perate zone so materially depend), may be fully apprehended,
together with its consequences, without any acquaintance
with those geodesical and astronomical determinations, by
means of which the precise forms and dimensions of the
continents have been delineated in our maps ? Thus, too,
the physical description of the earth teaches us that the
length of the equatorial axis of our planet exceeds that of
its polar axis by a certain number of miles, and informs us
of the mean equality of the compression of the northern
and southern hemispheres, without the necessity of relating
in detail the measurements of degrees and the pendulum
experiments, by means of which we have arrived at the
knowledge that the true figure of the earth is that of an irre-
gular ellipsoid of revolution, and is reflected in the irregu-
larity of the movements of the earth's satellite, the moon.
Enlarged views of physical geography have been essen-
tially advanced by the appearance of the admirable work
(" Erdkunde im Yerhaltiiiss zur Natur und zur Geschichte
des Menschen, oder allgemeine vergleichende Geographic")
in which Carl Bitter has characterized so powerfully the phy*
giognomy of our globe, and has shewn the influence of its
external configuration, both on the physical phaenomena which
take place on its surface, and on the migration of nations,
their laws, their manners, and their history.
France possesses an immortal work, Laplace's " Exposir
PHYSICAL KNOWLEDGE. 31
tion du Systeme du Monde," in which the results of the
highest mathematical and astronomical labours of all pre-
ceding ages are presented, detached from all details of de-
monstration. In this work the structure of the heavens is
reduced to the simple solution of a great problem in me-
chanics ; and yet, assuredly, it has never been accused of in-
completeness, or want of profoundness. The separation of
the general from the special not only renders it possible to
embrace at one view, with greater clearness, a wider field of
knowledge, but it also lends to the treatment of natural
science a character of greater elevation and grandeur. By
the suppression of details the masses are better seen, and
the reasoning faculty is enabled to grasp that which might
otherwise escape our limited powers of comprehension.
The high degree of improvement which the last half cen-
tury has witnessed in the study of all the separate branches
of natural science, but especially in those of chemistry, gene-
ral physics, geology, and descriptive natural history, is emi-
nently favourable to the presentation of general results. When
first looked at singly and superficially all phsenomena appear
unconnected ; as observations multiply and are combined by
reflection, and as a deeper insight into natural powers is
obtained, more and more points of contact and links of
mutual relation are discovered, and it becomes more and
more possible to develope general truths with conciseness,
without superficiality. In an age of such rapid and bril-
liant progress as the present, it is a sure criterion of the
number and value of the discoveries to be hoped for in any
particular science, if, though studied with great assiduity
and sagacity, its facts still appear for the most part uncon-
nected, with little mutual relation, or even in some instances
VOL. I. «i
32 ENLARGED YIEWS OF PHYSICAL
in seeming contradiction with each other. Such is the kind
of expectation at present excited by meteorology, by many
parts of optics, and, since the admirable labours of Melloni
and Faraday, by the study of radiant heat and of electro-
magnetism. The circle of brilliant discoveries has here still
to be run through ; although the Yoltaic pile already reveals
the wondrous connection of electrical, magnetical, and che-
mical phenomena. Who will venture to affirm, that we yet
know with precision that part of the atmosphere which is
not oxygen, or that thousands of gaseous substances affect-
ing our organs may not be mixed with the nitrogen ? or
who will say that we already know even the whole number
of the forces which prevade the universe ?
It is not the purpose of this work to attempt to reduce
all sensible phsenomena to a small number of abstract prin-
ciples, having their foundation in pure reason only. The
physical cosmography of which I attempt the exposition
does not aspire to the perilous elevation of a pure rational
science of nature. Leaving to' others, who may perhaps
adventure on them with more success, these depths of a
purely speculative philosophy, my essay on the Cosmos con-
sists of physical geography, joined with the description
of the heavenly bodies in space : its aim is to present
a view of the material universe, which may rest on the
experimental foundation of the facts registered by science,
compared and combined by the operations of the intel-
lect. It is within these limits alone that the under-
taking can harmonise with the wholly objective tendency of
my mental disposition, and with the labours which have
occupied my long scientific career. The unity which I seek
to attain in the development of the great phenomena of
GEOGRAPHY AND ASTRONOMY. 33
nature, is similar in kind to that which historical composi-
tions may offer. All that belongs to the specialities of the
actual, — to its individualities, variabilities, and accidents,
whether in the form and connection of natural objects and
phenomena, or in the struggle of man with the elements, or
of nations with each other, — does not admit of being ration-
ally constructed, that is to say, of being deduced from
ideas alone. I venture to think that a like degree of
empiricism attaches to the description of the material uni-
verse, and to civil history ; but in reflecting on physical
phenomena and historical events, and in reasoning back-
ward to their causes, we recognise more and more the
grounds of that ancient belief, that the forces inherent in
matter, and those which regulate the moral world, exert their
action under the government of a primordial necessity, and
in recurring courses of greater or less period. It is this
necessity, this occult but permanent connection, this perio-
dical recurrence in the progressive development of forms, of
phenomena and of events, which constitute nature obedient
to the first-imparted impulse of the Creator. Physical sci-
ence, as the name imports, limits itself to the explanation
of the phsenomena of the material world by the properties
of matter. All beyond this belongs not to the domain of
the physics of the universe, but to a higher class of ideas.
The discovery of laws, and their progressive generalisa-
tion, are the objects of the experimental sciences. Kant,
who has never been deemed an irreligious philosopher, has
traced with rare sagacity the limits of physical explanations,
in his celebrated " Essay on the Theory and Structure of
the Heavens," published at Konigsberg, in 1755*.
The study of a science which promises to lead us over the
34 ENLARGED VIEWS OF PHYSICAL
wide range of creation, may be likened to a journey in a
distant country. Before undertaking it, we are inclined to
measure, perhaps not without mistrust, both our own
strength and that of the guide who offers to conduct us.
But our fears may be lessened by remembering how in our
days, an increasing knowledge of the mutual relation of
phsenomena, leading to the attainment of general results, has
more than kept pace with the vast increase of separate
observations. The chasms which divide facts from each
other are rapidly filling up ; and it has often happened that
. facts observed at a distance have thrown a new and unex-
pected light on others nearer home, which had long seemed
to resist all efforts at explanation. Plants and animals which
had long appeared insulated, become connected with others
by the discovery of intermediate forms before unknown ; and
the geography of beings endowed with organic life receives
completeness, as we behold species, genera, and whole
families, peculiar to one continent, reflected, so to speak,
in analogous forms, or, as it were, in equivalents, in
the opposite continent. These transitions may be traced,
in the sometimes fuller, sometimes more rudimentary,
development of particular parts, or in their different relative
importance in the balance of forces, or in the junction of
distinct organs, or sometimes in resemblances to intermediate
forms, not permanent, but only characteristic of particular
phases of a normal development. Passing to the considera-
tion of inorganic bodies, and to examples which characterise
strongly the advances of modern geology, we see how,
according to the grand views of Elie de Beaumont, chains
of mountains, dividing different climates, floras, and nations,
reveal to us their relative age, by the nature of the sedimen-
GEOGRAPHY AND ASTRONOMY. 35
tary rocks uplifted by them, and by the directions which
they follow over the long crevices produced by the action.
of the forces which have elevated in ridges portions of
the crust of the globe. Relations of superposition of
trachyte and of syenitic porphyry, of diorite and of ser-
pentine, which remain doubtful if studied in the aurife-
rous soils of Hungary, in the platinum district of the
Oural, or on the South "Western slope of the Siberian
Altai, are clearly made out by the aid of observations on
the high table-lands of Mexico and Antioquia, and in
the unhealthy ravines of the Choco. The most important
of the materials which in modern times have afforded a solid
basis for physical geography have not been accumulated by
chance. In conformity with its characteristic tendencies,
our age has recognised, that facts obtained by observations
in different regions of the earth, can only be expected to
prove fruitful in results, when the traveller is previously
acquainted with the state and wants of the science which he
seeks to advance, and when his researches are conducted
under the guidance of sound ideas, and some insight into
the character and connection of natural phenomena.
By means of the happy, though often too easily satisfied ten-
dency towards general conceptions, a tendency dangerous only
in its abuse, a considerable portion of the results of natural
knowledge may become the common property of all educated
persons, producing a sound information very different both
in substance and in form from those superficial compilations,
which contained the sum of what, up to the close of the
last century, was complacently designated by the unsuitable
term of popular scientific knowledge. I take pleasure in
persuading myself that it is possible for scientific subjects to
36 POPULAR SCIENTIFIC KNOWLEDGE.
be presented in language, grave, dignified, and yet animated ;
and that those who are able to escape occasionally from the
restricted circle of the ordinary duties of civil life, and regret
to find that they have so long remained strangers to nature,
may thus have opened to them access to one of the noblest
enjoyments which the activity of the rational faculties can
afford to man. The study of general natural knowledge
awakens in us as it were new perceptions wliich had long
lain dormant ; we enter into a more intimate communion
with the external world, and no longer remain without in-
terest or sympathy for that which at once promotes the
industrial progress and intellectual ennoblement of man.
The clearer our insight into the connection of phsenomena,
the more easily shall we emancipate ourselves from the error
of those, who do not perceive that for the intellectual culti-
vation and for the prosperity of nations, all branches of
natural knowledge are alike important ; whether the mea-
suring and describing portion, or the examination of
chemical constituents, or the investigation of the phy-
sical forces by which all matter is pervaded. It has not
been uncommon presumptuously to depreciate investigations
arbitrarily characterised as "purely theoretic;" forgetting
that in the observation of a phenomenon which shall at first
sight appear isolated, may lie concealed the germ of a great
discovery. "When Galvani first stimulated the nervous fibre
by the contact of two dissimilar metals, his immediate contem-
poraries could not have foreseen that the voltaic pile would
discover to us in the alkalis, metals of a silvery lustre, easily
inflammable, and so light as to float in water ; that it would
become the most important instrument of chemical analysis,
and at the same time a therrnoscope and a magnet. When
POPULAR SCIENTIFIC KNOWLEDGE. 37
Hujgens first applied himself, in 1678, to the enigma of
the phenomena of polarisation of light exhibited in doubly-
refracting spar, and observed the difference between the two
portions into which a beam of light divides itself in passing
through such a crystal, it was not foreseen that through the
admirable sagacity of a physical philosopher of the present
day(16), the phsenomena of chromatic polarisation would
lead us to discern, by means of a minute fragment of Iceland
spar, whether the light of the sun proceeds from a solid
nucleus, or from a gaseous covering ; whether comets are
self-luminous, or reflect borrowed light.
An equal appreciation of all parts of natural knowledge
is an especial requirement of the present epoch, in which
the material wealth and increasing prosperity of nations
are in great measure based on a more enlightened employ-
ment of natural products and forces. The most super-
ficial glance at the present condition of European states
shews, that those which linger in the race cannot hope to
escape the partial diminution, and perhaps the final
annihilation, of their resources. It is with nations as with
nature, which, according to a happy expression of Goethe (l7),
knows no pause in unceasing movement, development, and
production, and has attached a curse to standing still.
The danger to which I have alluded must be averted by the
earnest cultivation of natural knowledge. Man can only
act upon nature, and appropriate her forces to his use, by
comprehending her laws, and knowing those forces in relative
value and measure. Bacon has said that, in human societies,
knowledge is power, — both must rise or sink together.
Knowledge and thought are at once the delight and the
prerogative of man; and they are also a part of the wealth of
38 POPULAR SCIENTIFIC KNOWLEDGE.
nations, and often afford to them an abundant indemnifica-
tion for the more sparing bestowal of natural riches. Those
states which remain behind in general industrial activity, iu
the selection and preparation of natural substances, in the ap-
plication of mechanics and chemistry, — and where a due appre-
ciation of such activity fails to pervade all classes, — must see
their prosperity diminish ; and that the more rapidly as neigh-
bouring states are meanwhile advancing, both in science and
in the industrial arts, with, as it were, renewed and youthful
vigour.
The improvement of agriculture in the hands of freemen,
and on properties of moderate extent, — the nourishing state
of the mechanical arts freed from the trammels of the spirit
of corporation, — commerce augmented and animated by the
multiplied contact of nations with each other, — are brilliant
results of the general progress of intelligence, and of the
amelioration of political and civil institutions in which that
progress is reflected. The picture presented by modern his-
tory ought to convince those who seem tardy in apprehending
the instruction which it is fitted to convey. Nor let it be
feared that the predilection for industrial progress and for
those branches of natural science most immediately connected
with it, which characterizes the age in which we live, has any
necessary tendency to check intellectual exertion in the fair
fields of classical antiquity, liistory, and philosophy ; or to
deprive of the life-giving breath of imagination, the arts and
the literature which embellish life. Where all the blossoms
of civilisation unfold themselves with vigour under the
shelter of wise laws and free institutions, there is no danger
of the development of the human mind in any one direction
proving prejudicial to it in others. Each offers to the nation
POPULAR SCIENTIFIC KNOWLEDGE. 39
precious fruits, — those which furnish necessary subsistence
and comfort, and are the foundation of material wealth,- —
and those fruits of creative fancy which, far more enduring
than that wealth, transmit the 9[lorr of the nation to the
remotest posterity. The Spartans, in spite of the Doric
severity of their mode of thought, "prayed the Gods to
grant them the beautiful with the good (18)."
As in that higher sphere of thought and feeling to which
I have just alluded, in philosophy, poetry, and the fine arts,
the primary aim of every study ought to be an inward one,
that of enlarging and fertilising the intellect; so the direct
aim of science should ever be the discovery of laws, and of
the principles of unity, order, and connection, which every
where reveal themselves in the universal life of nature. But
by that happy connection, whereby the useful is ever linked
with the true, the exalted, and the beautiful, science thus
followed for her own sake will pour forth abundant, over-
flowing streams, to enrich and fertilise that industrial pros-
perity, which is a conquest of the intelligence of man over
matter.
The influence of mathematical and physical knowledge on
national prosperity, and on the present condition of Europe,
requires here only a passing allusion : the well-nigh boundless
course which we have to travel over, warns me that it would
ill become me to digress more widely from the leading object
of our undertaking, — the contemplation of nature as a whole.
Accustomed to distant excursions, I have perhaps fallen into
the error of describing the path before us as more smooth
and pleasant than it will be really found, as those are wont to
do who love to guide others to the summit of lofty moun-
tains : they praise the view, even when great part of the dis-
40 INFLUENCE OF MATHEMATICAL
taut prospect is hidden by the clouds ; knowing, indeed, that
this half transparent misty veil is itself not altogether without
a secret charm for the imagination. I too ought to fear, that
from the height to which fchis physical description of the
universe aspires, many parts of the wide horizon may appear
dimly lighted and imperfectly defined,— that much of the
prospect may remain vague and obscure, and this not only
by reason of the want of connection arising from the im-
perfect state of some branches of science, but also still more,
(and how, in so comprehensive a work, should I not will-
ingly own it ?) because of the deficiencies of the guide
who has imprudently ventured to attempt to scale these
lofty summits.
The object of this introductory discourse has been less to
represent the importance of natural knowledge, which is
admitted by all, and may well dispense with any eulogium,
than to shew how, without prejudice to the thorough and
fundamental study of separate branches, a higher point of
view may be indicated, from whence all the forms and the
forces of nature may be contemplated in intimate and living
connection.
The idea of physical geography, extended so as to embrace
ail that we know of the material creation in space as well
as on our own globe, passes into that of physical cosmogra-
phy ; the one term is moulded upon the other. But the
science of the Cosmos, as I understand it, is not the mere
encyclopaedic aggregation of the most general and impor-
tant results, extracted from separate works on natural history,
physics, and astronomy. Such results are only to be used
as materials, and in so far as they illustrate the concurrent
action of the various forces in the universe, and the manner
AND PHYSICAL KNOWLEDGE. 41
in which they reciprocally call forth or limit each other.
The distribution of organic types in different regions and
climates (i. e. the geography of plants and animals,) differs
tus widely from descriptive botany and zoology, as does a
geological knowledge of the globe from mineralogy properly
so called. The physical description of the universe is not
therefore to be confounded with encyclopedias of the natu-
ral sciences. In the work before us it is proposed to
consider partial facts only in their relation to the whole.
The higher the point of view here indicated, the more the
study requires a peculiar mode of treatment, and to be pre-
sented in animated and picturesque language.
But thought and language are of old intimately allied : if
the language employed lends to the presentation grace and
clearness, if by its organic structure, its richness, and happy
flexibility, it favours the attempt to delineate the phenomena
of nature, it at the same time reacts almost insensibly on
thought itself, and breathes over it an animating influence.
Words, therefore, are more than signs and forms ; and their
mysterious and beneficent influence is there most powerfully
manifested, where the language has sprung spontaneously from
the minds of the people, and is on its own native soil. Proud
of my country, whose intellectual unity is the firm foundation
of every manifestation of her power, I look with joy to these
privileges of my native land. Highly favoured indeed is he,
who, in attempting an animated representation of the phseno-
mena of the universe, is permitted to draw from the depths of
a language, 'which through the elevation and free exercise of
powerful thought, in the domain of creative fancy no less
than in that of searching reason, has for centuries exerted so
powerful an influence over the minds and the destinies of men.
LIMITS AND METHOD OF EXPOSITION OF THE PHYSICAL
DESCRIPTION OF THE UNIVEBSE.
IN the preceding discourse, I have sought to make manifest,
and to illustrate by examples, how greatly the enjoyment of
nature, varying as it does in the inward sources from which
it springs, may be heightened by a clear insight into the
connection of phsenomena, and of the laws by which they are
regulated. I have now to examine more particularly the
spirit of the method of exposition, and to indicate the limits
of the science of physical cosmography, such as I have con-
ceived it, and have now endeavoured to display it, after
many years of preparatory studies in many regions of the
earth. Would, that in so doing, I might natter myself with
the hope of thereby justifying the bold title of my work,
and freeing it from the reproach of presumption !
Before entering on the view of nature, which forms the
larger portion of the present volume, T would touch on
some general considerations intimately connected with each
other, with the nature of our knowledge of the external
world, and with the relations which this knowledge presents,
at different epochs of history, to the different phases of the
intellectual cultivation of nations. These considerations
will have for their objects : —
1. The idea and the limits of physical cosmography as a
distinct and separate science.
PHYSICAL DESCRIPTION OP THE UNIVERSE. 43
2. A rapid review of the known phsenomena of the uni-
verse, under the form of a general view of nature.
3. The influence of the external world on the imagina-
tion and feelings. This, in modern times, has acted as a
powerful incitement to the study of the natural sciences,
through the instrumentality of animated descriptions of dis-
tant regions, descriptive poetry (a branch of modern litera-
ture), of landscape painting when it seizes the characteristic
physiognomy of vegetable or of geological forms, and by
the cultivation and arrangement of exotic plants, in well-
contrasted groups.
4. The history of the contemplation of nature, or the
progressive development of the idea of the Cosmos, with the
exposition of the historical and geographical facts which
have led to the systematic connection of the phsenomena as
they are thus presented.
The higher the point of view from which all the
phsenomena are to be regarded in this study, the more
necessary it is to circumscribe it within its just limits,
and to distinguish it from all analogous and auxiliary
ones. The physical description of the universe is founded
on the contemplation of all the material creation (whether
substances or forces) co-existing in space. For man, as an
inhabitant of the earth, it may be ranged under two leading
divisions ; the telluric and the celestial. I will pause a few
moments on the first of these, (or on that portion of the
science of the Cosmos which concerns the Earth,) in order
to illustrate the independence of the study, and the nature
of its relation to general physics, descriptive natural history,
geology, and comparative geography. An encyclopaedic
aggregation of these would no more constitute the telluric
44 PHYSICAL DESCRIPTION OF THE UNIVERSE.
portion of the Cosmos, than a mere dry enumeration of the
philosophical opinions prevailing in different ages, would
deserve to be called the history of philosophy.
The confusion between the boundaries of closely allied
branches of study has been the greater, because for centu-
ries different portions of our empirical knowledge have been
designated by terms which are either too comprehensive, or
too restricted, for the notions they were intended to convey :
and which have besides the disadvantage of having borne a
very different sense in the languages of classical antiquity
from which they have been borrowed. The terms of physics,
physiology, natural history, geology, and geography, arose
and grew into general use long before clear ideas were enter-
tained of the diversity of the objects which those sciences
ought to embrace, and consequently of their respective
limits. Such is the influence of long habit upon language,
that in one of the nations of Europe most advanced in
civilisation, the word " physic" is applied to medicine ; and
in a Society of justly deserved and universal renown, writ-
ings on technical chemistry, geology, and astronomy experi-
pirically treated, (all branches of purely experimental science),
are classed under the general title of " Philosophical Transac-
tions." The attempt lias often been made, and almost always
in vain, to substitute new and more appropriate names for
those ancient terms, — vague, it is true, but which, however,
are now generally understood. These changes have been
proposed, for the most part, by those who have occupied
themselves with the general classification of all branches of
human knowledge ; from the great Encyclopsedia (Margarita
Philosophica) of Gregory Eeisch(19), Prior of the Chartreuse
of Ereiburg towards the end of the fifteenth century, to
LIMITS AND METHOD OF EXPOSITION. 45
Lord Bacon ; from Bacon to D'Alembert ; and still more
recently to a sagacious physicist of our own time, Andre-Marie
Ampere (20) . The selection of an inappropriate G reek nomen-
clature has, perhaps, been even more prejudicial to the last of
these attempts, than the abuse of the binary division and the
excessive multiplication of groups.
The physical description of the universe as an object of
external sense, does indeed require the aid of general physics
and of descriptive natural history ; but the consideration of
the material creation, all the parts of which are linked toge-
ther by mutual connection, under the figure of a natural
whole animated and moved by inward forces, gives to the
science which now occupies us a peculiar character. Physical
science dwells on the general properties of matter ; it is an
abstract representation of the manifestations of physical
forces, and in the work in which its earliest foundations were
laid, in the eight books of Physics of Aristotle (21), all the
phenomena of nature are depicted as the moving vital activity
of a universal force or power.
The telluric portion of the physical description of the
universe, to which I preserve the old and expressive title of
physical geography, treats of the distribution of magnetism
on our planet in its relations of intensity and direction, but
does not teach the laws of magnetic attraction and repulsion,
or the means of eliciting powerful electro -magnetic effects,
whether transitorily or permanently. Physical geographj
describes in bold and general outlines the compact or in-
dented configuration of continents, and the distribution of
their masses in both hemispheres, — a distribution which
powerfully influences the differences of climates and the most
important meteorological processes of the atmosphere; it
46 PHYSICAL DESCRIPTION OP THE UNIVERSE.
seizes the predominant character of mountain chains,
whether parallel, or transverse and intersecting, and whether
belonging to the same or to different epochs and systems of
elevation ; it examines the mean height of continents above
the present surface of the sea, or the position of the centre
of gravity of their volume; the relation of the highest
summits of the great chains to the general line of their
crests, to the vicinity of the sea, and to the mineral charac-
ter of the rocks of which they consist. It depicts to us the
eruptive rocks as active principles of movement, traversing,
uplifting, and inclining at various angles, the passive sedi-
mentary rocks . it considers volcanoes either as isolated, or
ranged in single or in double series, and extending their
sphere of action to various distances, either by means of
long narrow bands of erupted rocks, or by earthquakes
operating in circles which widen or contract in the course of
centuries. It describes the strife of the liquid element with
the firm land ; it shews the features which are common to
all great rivers in the upper and in the lower portion of
their course, and how they become subject to bifurcation.
It characterises rivers either as breaking their way through
great mountain chains, or following, for a time, a course
parallel to them, either close to their foot or at a considerable
distance, according to the influence which the elevation of
the mountain system may have exercised on the neighbouring
plains. It is only the general results of comparative oro-
graphy and hydrography which belong to the science whose
proper limits I am endeavouring to trace, and not the enu-
meration of our loftiest mountains, active volcanoes, or
rivers with the extent of their watershed and the number of
their tributaries. All these details belong to geography
LIMITS AND METHOD OF EXPOSITION. 47
properly so called, in its most restricted sense. We here
consider phsenomena only in their mutual connection, and
in their relations to the different zones of our planet,
and to its general physical constitution. The specialities
either of inanimate substances or of organic beings, classed
according to analogy of form and composition, do indeed
form a highly interesting subject of study, but quite foreign
to the present work.
Particular descriptions of countries are, it is true, the most
available materials for a general physical geography ; but the
most careful successive accumulation of such descriptions
would be as far from affording a true picture of the general
conformation of the irregular surface of our planet, as a
series of all the floras of different regions would be from
forming what I should designate by the term of a " Geo-
graphy of Plants." It is the work of the intellect, by
comparing and combining isolated observations, to extract
^om the specialities of organic formation (morphology and
the descriptive natural history of plants and animals,) that
which is common to them in regard to their climatic distri-
bution ; — to investigate the numerical laws, or the proportion
of certain forms or particular families to the whole number
of species ; — to assign the latitude or geographical position of
the zone where (in the plains) each of these forms reaches
its maximum number of species, and its highest orgpnift
development. These considerations will lead us to perceive
the manner in which the picturesque character of the land-
scape in different latitudes, and the impression which it pro-
duces on the mind, depend principally on the laws of the
geography of plants, or the relative number and more vigorous
growth of those wLich predominate in the general mass. Tha
YOL, J, *
48 PHYSICAL DESCRIPTION O¥ THE UNIVERSE.
systematically-arranged catalogues, to which the too pompous
name of " Systems of Nature" was formerly given, present to
us an admirable connection and arrangement by analogies of
structure, whether completely developed, or (according to
views of an evolution in spirals) in the different phases passed
through in vegetables, by the leaves, bracteas, calix, blossom,
and fruit, and in animals by their cellular and fibrous tissues,
and their articulations or less perfectly developed parts. But
these ingeniously classified so called " systems of nature/'
do not shew us organic beings as they are grouped over the
surface of our planet, in districts, zones of latitude, or of
elevation, and according to other climatic influences arising
from general and often very distant causes. But, as we
have already said, the final aim of physical geography is to
recognise unity in the vast variety of phenomena, and by
the exercise of thought and the combination of observations,
to discern that which is constant through apparent change.
In the exposition of the terrestrial portion of the Cosmos,
we may sometimes find occasion to descend to very special
facts, but it will only be for the purpose of recalling the
connection existing between the laws of the actual distribu-
tion of organic beings over the surface of the globe, and the
laws of the ideal classification by natural families, analogy
of internal organisation, and progressive evolution.
It follows from these discussions on the limits of different
sciences, and particularly from the distinction which it ia
necessary to draw between descriptive botany (morphology)
and the geography of plants, that, in the physical description
of the globe, the innumerable multitude of organised bodies,
which form so large a portion of the beauties of creation,
ought to be considered rather with reference to zones of
PHYSICAL DESCRIPTION OF THE UNIVERSE. 49
habitation, and to the differently inflected isothermal
curves, than according to principles of gradation in the
development of their internal organisation. But botany
and zoology, which are the two branches of the descriptive
natural history of organised bodies, are the fruitful sources
from whence we draw the materials, without which the
study of the relations and connection of phenomena would
want a solid foundation.
We will here add an important observation. The first
general glance over the vegetation of an extensive portion
of a continent, shews us an assemblage of dissimilar forms, —
graminese, orchideae, coniferae, and oaks : we perceive these
families and genera, instead of being locally associated, scat-
tered apparently as it were by chance : but this irregular
dispersion is only apparent ; and it is the province of phy-
sical geography to shew that vegetation every where presents
constant numerical relations in the development of its forms
and types; that, in the same climates, species which are
wanting in one country, are replaced in a neighbouring one
by other species of the same families, according to a law of
substitution, which seems to belong to the yet unknown
relations of organised beings ; and by which the numerical
proportion of particular great families to the whole mass of
the phsenogamous floras in adjoining countries is main-
tained. There is thus revealed in the multitude of organic
forms by which these regions are peopled a principle of
unity, a primitive plan of distribution. There is also dis-
covered in each zone, diversified according to the families of
plants, a slow but continuous action on the aerial ocean, an
action which depends on the influence of light — that primary
and essential condition of all organic vitality ou the solid or
50 LIMITS AND METHOD OF THE
liquid surface of our planet. It might be said, according to
a fine expression of Lavoisier, that the marvel of the an-
cient mythus of Prometheus is incessantly renewed before
our eyes.
When we apply the course which it is proposed to follow
in the exposition of the physical description of the earth, to
the sidereal part of the science of the Cosmos, or to the
description of what is known to us of the regions of space,
and of the heavenly bodies which they contain, we shall
find our task remarkably simplified. If, according to an-
cient but inexact forms of nomenclature, we distinguish
between physics, or the general consideration of matter, its
forces, and its movements, — and chemistry, or the conside-
ration of the different nature of substances, their elementary
composition, and their attractions not depending on rela-
tions of mass or the laws of gravitation, — we must of course
recognise that the telluric portion of our study embraces
both physical a-nd chemical processes. By the side of the
fundamental force of gravitation, we discover around us on
the earth the action of other forces, taking effect either
when the particles of matter are in contact, or at exceedingly
small distances apart (22) ; to which forces we give the name of
chemical affinity. Under various modifications, by electri-
city, by heat, by condensation in porous bodies, or by the
contact of an intermediate substance, these forces are inces-
santly in action in inorganic matter, and in the tissues of
animals and plants. But, in the regions of space, we are
only cognizant by direct observation of physical phenomena,
and among these (excepting in the case of the small aste-
roids, which appear to us under the form of aerolites or
shooting stars,) we know with certaiiity only those effects
PHYSICAL DESCRIPTION OP THE UNIVERSE. 51
which depend on the quantitative relations of matter or the
distribution of masses ; and which may therefore be contem-
plated as governed by simple dynamic laws. Effects due to
specific differences, or to heterogeneous qualities of matter,
do not as yet enter into our calculations of the celestial
mechanics.
It is only through the phenomena of light (the propaga-
tion of luminous waves) and the effects of gravitation, that
the inhabitants of our earth enter into relation with matter
in space, whether existing in spheroids, or in a dispersed
form. The existence of a periodical influence of the sun or
moon on the variations of terrestrial magnetism is still highly
problematical. The only direct experimental knowledge which
we possess of any of the specific properties or qualities of
matter not belonging to our planet, is derived from the fall
of the aerolites or meteoric stones, already alluded to.
Their direction and enormous velocity of projection (a velo-
city wholly planetary) render it more than probable, that
these masses, enveloped in vapours and reaching the earth
in a state of high temperature, are small heavenly bodies,
which the attraction of our planet has caused to deviate
from their previous path. The aspect so familiar to us of these
asteroids, and the analogy which their composition presents
to the minerals of which the crust of our globe is formed,
are indeed very striking. The inference to which they point
appears to me to be, that the planetary and other masses
were agglomerated in rings of vapour, and afterwards in
spheroids, under the influence of a central body ; and that
being originally integral parts of the same system, they con-
sist of substances chemically identical. Pendulum experi-
ments, and especially those made by Bessel with so high a
52 LIMITS ATsD METHOD OF THE
degree of precision, confirm the Newtonian axiom, that the
acceleration occasioned by the attraction of the earth is
identical in bodies the most heterogeneous in composition,—
viz., water, gold, quartz, granular limestone, and portions
of different aerolites. Purely astronomical observations add
their testimony to the proofs afforded by the pendulum.
The almost identical results found for the mass of Jupiter,
from its influence on his own satellites, on Encke's comet of
short period, and on the small planets, Vesta, Juno, Ceres,
and Pallas, equally teach that, as far as our observations
reach, the attraction of gravitation is determined solely by
the quantity of matter (23) .
Tin's absence of all perception (derived either from obser-
vation or from theoretical considerations) of any heteroge-
neous qualities of matter, gives to celestial mechanics a high
degree of simplicity. The study of the immense regions of
space being directed by the laws of motion only, the sidereal
portion of the Cosmos draws from the pure and abundant
sources of mathematical astronomy, as the terrestrial portion
does from those of physics, chemistry, and organic morpho-
logy. But the domain of the three last-named sciences
embraces phenomena so complex, and, to the present time,
so little susceptible of the application of rigorously exact
methods, that the physical knowledge of the globe cannot
boast of the certainty and simplicity in the exposition of
facts and of their mutual connection, which characterise the
celestial portion of the Cosmos. This difference may be the
true reason why, in the early times of the intellectual culti-
vation of the Greeks, the natural philosophy of the Pytha-
goreans was directed to the heavenly bodies in space, rather
than to the earth and her productions ; and became through
PHYSICAL DESCRIPTION OP THE UNIVEESE. 53
Philolaus, and subsequently through the analogous views of
Aristarchus of Samos, and Seleucus of Erythrea, of far
greater avail towards the knowledge of the true system of
the universe, than the natural philosophy of the Ionic school
could ever become to the physical knowledge of the earth.
Giving less heed to the properties and specific differences of the
various kinds of matter, the great statical school, in its Doric
gravity, preferred to turn its regards towards all that relates
to measure, form, and number (24); while the Ionic school dwelt
on the qualities of matter, its real or supposed transforma-
tions, and its relations of origin. It was reserved to the
powerful genius, and to the at once profoundly philosophi-
cal and practical mind of Aristotle, to enter equally deeply
and successfully into the world of abstract ideas, and into
that of the rich diversity of material substances, of organised
beings, and animated existence.
Several highly esteemed treatises on physical geography
have prefixed to them an introductory astronomical section,
in which the earth is first considered in its planetary depen-
dence, and in its relation to the solar system. This order of
proceeding is opposite to that which I propose to follow.
The dignity of the physical description of the universe re-
quires that the sidereal portion, which Kant has called the
natural history of the heavens, should not be made sub-
ordinate to the terrestrial portion. In the science of the
Cosmos, according to the expression of Aristarchus of Samos
— that ancient herald of the Copernican doctrine — the sun
(together with all his satellites) is viewed but as one of the
countless host of stars. It is then with these celestial
bodies with which space is peopled, that the physical descrip-
tion of the universe ought to begin. It should commence
54 SCIKtfCE OF THE COSMOS.
with such a graphic sketch of the universe (such a
true map of the world) as was traced by the bold hand of
the elder Herschel. If, notwithstanding the smallness of
our planet, the telluric portion of the present work occupies
the largest space, and is treated with the greatest fulness,
this arises only from the unequal amount of our knowledge
of that which is within and that which is beyond our reach.
The subordination of the celestial to the terrestrial portion is
met with, however, in the great geographical work of Bernard
Varenius (25), written in the middle of the seventeenth century,
who distinguishes, with great acuteness, between general and
special geography ; subdividing the first into an absolute, or
properly terrestrial portion (when treating of the surface of
the earth in its different zones), and a relative or planetary one,
when considering the solar and lunar relations of our planet.
It is a permanent glory to Varenius, that his " General and
Comparative Geography" was found capable of fixing, in a
high degree, the attention of Newton. In the imperfect
state, in the time of Varenius, of the auxiliary branches of
knowledge from which his resources had to be drawn, it was
not possible that the execution of the work should corre-
spond to the greatness of the undertaking. It was reserved
to our own time to see comparative geography, in its most
extended sense, and even embracing its influence on the
history of man, treated in a masterly manner by my own
countryman, Carl Bitter (26).
The enumeration of the more important results of the astro-
nomical and physical sciences, which in the Cosmos radiate
towards a common centre, may justify, in some degree, the
title which I have ventured to affix to this work, written in
the late evening of my life. I might add, that the title is
SCIENCE OF THE COSMOS. 55
perhaps more adventurous than the enterprise itself, circum-
scribed within the limits which I have proposed. In all
my previous investigations, I have hitherto avoided, as much
as possible, the introduction of new names to express general
ideas. When I have attempted to enlarge our nomenclature,
it has been solely in the specialities of descriptive botany and
zoology, when objects observed for the first time rendered new
names necessary. The expression of physical cosmography,
or a physical description of the universe, is formed on that oi
physical geography, or a physical description of the earth,
which has long been used. The powerful genius of Des-
cartes has left us some fragments of a great work, which he
intended should appear under the title of " Monde," and
for which he had begun to study special subjects, and even
human anatomy. The little used, but precise expression of
the science of the Cosmos, recals to the inhabitant of our
globe that we are treating of a wider horizon, of the assem-
blage of all the material things with which space is filled,
from the remotest nebulae, to the climatic distribution of
the thin vegetable tissues of variously coloured lichens,
which clothe the surface of rocks.
In every language, views entertained in the infancy of
nations have led to a confusion of the ideas of earth and
world : the common expressions of " voyages round the
world/' " map of the world/' " new world," are instances
of this confusion. The more accurate and more noble ex-
pressions* of "system of the world/' "creation of the
* Our language does not possess all the expressions referred to by M. de
Humboldt. We have no direct English equivalents for the expressive Ger-
man terms " Weltgebaude," "Weltraum," aiid "Weltkorper."
* NSLATOR.
56 SCIENCE OP THE COSMOS.
world/' and others of a similar nature, relate either to the
whole of the bodies with which celestial space is filled, or to
the origin of the entire universe.
it was natural that, amidst the extreme variability of the
phenomena presented by the surface of the earth and the
surrounding aerial ocean, men should have been impressed
by the aspect of the vault of heaven and the regular and
uniform movements of the sun and planets. The word
Cosmos, which, in its primitive signification in the Homeric
times, expressed the ideas of ornament and order, was
subsequently applied to the order and harmony observed in
the movements of the heavenly bodies ; then to those bodies
generally ; and finally, to the universe itself. It is asserted
by Philolaus, — the genuine fragments of whose writings have
been commented on with so much sagacity by M. Boekh, —
that, according to the general testimony of antiquity (27),
" Pythagoras was the first who used the word Cosmos to
express the order which reigns in the universe, or the
world or universe itself." From the Italic school of
philosophy, the term used in this sense passed into the
language of the poets of nature, Parmeuides and Empe-
docles, and thence into that of prose writers. We need not
enter here into the distinction, which, following the Pytha-
gorean views, Philolaus draws between Olympus, Uranus,
and Cosmos, or how the latter word, used in the plural, has
been applied individually to celestial bodies (the planets)
circling round the central " hearth," or focus of the world,
or to " world-islands," or groups of stars. In my work,
the word Cosmos is employed as signifying the heavens and
the earth, or the whole world of sense, or the material uni-
verse; agreeably to general Hellenic usage subsequently to the
SCIENCE OF THE COSMOS. 57
time of Pythagoras, and in conformity with its definition by
the unknown author of the treatise, entitled " De Mundo/'
which was long erroneously attributed to Aristotle. If
scientific names had not long varied from their true linguistic
meaning, the present work might properly have been entitled
'* Cosmography!' divided into Uranography and Geo-
graphy. The desire of imitating the Greeks led the later
Eomans, in their feebler philosopliical essays, to give the
signification of universe to the word mundus, the primary
meaning of which was merely that of ornament, without
including order or regularity in the arrangement. of parts.
The introduction of this technical term, in the same double
signification as the Greek word Cosmos, was probably due
to Ennius(28), who was a follower of the Italic school, and
translated the writings of Epicharmus, or one of his imita-
tors, on the Pythagorean Philosophy. A physical history
of the universe, in the extended sense of the word, ought,
if materials for writing it existed, to trace the variations
to which the Cosmos has been subjected in the course of
ages, from those new stars which have suddenly become
visible or have disappeared in the firmament, from nebulae
dissolving or condensing towards their centres, — to the
first cryptogamic vegetation on the surface of the recently
cooled crust of the globe, or that which now clothes the
coral reef newly risen above the ocean. On the other
hand, the object of a physical description of the universe
is to present a view of all that co-exists in space, and of
the simultaneous action of natural forces, with the result-
ing phenomena. But if we wish to comprehend existing
nature well, we cannot separate entirely and absolutely the
consideration of the present state of things, from that of
58 SCIENCE OF THE COSMOS.
the successive phases through which they have previously
passed. The mode of formation, or of production, is often
an important element of their character. Nor is it in the
organic world only that matter is constantly undergoing
change, and dissolving to be formed into new combinations :
the globe on which we live also reveals the knowledge of
an earlier state: the strata of sedimentary rocks, which
compose a large portion of its crust, present to us earlier
forms of organic life, which have now almost entirely disap-
peared ; and these forms are associated in groups, successively
replacing each other. The different superimposed strata thus
present to us the buried faunas and floras of different
epochs. In this sense the description of nature cannot be
separated from its history ; for, in studying the present, the
geologist, in tracing the mutual relations of thefactswhich come
before him, is conducted back to ages long past : this inter-
mixture of past and present is in some respects analogous to
that which may be observed in the study of languages, where
the etymologist fmdstraces of successive grammatical develop-
ments, leading him back to the primitive state of the
idiom reflected as it were in forms of speech now in use.
In the material world, this reflex of the past is the clearer,
from our now seeing similar eruptive and sedimentary rocks
in process of formation. The particular forms of domes of
trachyte, basaltic cones, bauds of amygdaloid with long
parallel pores, and white deposits of pumice with black
scoriae intermixed, give in the eye of the geologist a pecu-
liar kind of animation to the landscape, acting on his ima-
gination as traditional monuments of an earlier world. Their
form is their history.
The sense in which the Greeks and Romans employed the
SCIENCE OF THE COSMOS. 59
word history shows that they too had the intimate persua-
sion, that, to form a complete idea of the actual condition of
things, it was necessary to consider them in their succes-
sion. It is not, however, in the definition given by "Verrius
Flaccus(29), but in the zoological writings of Aristotle, that
the word history presents itself as signifying an exposition
of the results of experience and observation. The elder
Pliny's physical description of the world bears the title of
" Natural History ;" and in his nephew's letters, the nobler
appellation of "History of Nature/' The earlier Greek
historic writers scarcely separated the description of countries
from the relation of events of which they had been the
theatre. In their writings, physical geography and history
were long gracefully and pleasingly interwoven, until the
increasing complexity of political interests, and the agita-
tions of civil life, expelled the geographical element from
the history of nations, and obliged it to become the subject
of a separate study.
It remains to examine, whether we can hope, by the ope-
ration of thought, to reduce the immense diversity of phseno-
mena comprehended by the Cosmos, to a unity of principle,
similar to that presented by the evidence of what are
specially called "rational truths." In the present state of
our empirical knowledge at least, we dare not entertain such
a hope. Experimental sciences, founded on observation
of the external world, cannot aspire to completeness ; the
nature of things and the imperfections of our organs are alike
opposed to it. We shall never succeed in exhausting the
inexhaustible riches of nature, and no generation of men
will ever be able to boast of having comprehended all phfle-
It is only by distributing them into groups, that
60 SCIENCE OF THE COSMOS.
we have been able to discover in some the empire of laws, grand
and simple as Nature herself. Doubtless, the bounds of
this empire will be enlarged as the physical sciences gradually
enlarge their domain, and become more perfect. Brilliant
examples of such progress have appeared in our own times, in
the phsenomena of electro-magnetism, and in those of the
propagation of luminous waves and of radiant heat. The
doctrine of evolution shows us how, in organic development,
all that is formed is sketched out as it were beforehand, and
how the tissues of both vegetable and animal matter are
uniformly produced by the multiplication and transformation
of cells.
The generalisation of laws which were first applied to
smaller groups of phsenomena advances by successive grada-
tions, and their empire is extended, and their evidence
strengthened, so long as the reasoning process is directed to
really analogous phsenomena. But as soon as dynamic views
no longer suffice, and the specific properties of heteroge-
neous matter come into play, fear may be entertained
lest, in the too obstinate pursuit of laws, we may arrive at
impassable chasms : the principle of unity fails, and the
guiding clue breaks, when, in tracing the effects of natural
forces, we come to specific kinds of action. The law ol
equivalents, and of definite numerical proportions in com-
pound substances, so happily recognised by modern chemists
and proclaimed under the antique form of atomic symbols,
remains hitherto isolated, and unsubjected to the mathema-
tical laws of motion and gravitation.
Natural productions, which are objects of direct obser-
vation, may be logically distributed in classes, order?,
and families, Such distribution does no doubt give greater
GENERALISATION OF LAWS. 61
clearness to descriptive natural history; but the study of
organised bodies, arranged in linear connection, though it
gives greater unity and simplicity to the distribution of
groups, cannot rise to the height of a classification founded
on a sole principle of composition and internal organisa-
tion, As different gradations aie presented by natural laws,
according as they embrace narrower or wider circles of phse-
nomena, so there are successive steps in empirical investi-
gation. It begins by single perceptions, which are after-
wards classed according to their analogy or dissimilarity.
Observation is succeeded, at a much later epoch, by experi-
ment, in which phenomena are made to arise under condi-
tions previously determined on by the experimentalist, guided
by preliminary hypotheses, or a more or less just intuition
of the true connection of natural objects and forces. The
results obtained by observation and experiment lead by the
path of induction and analogy to the discovery of empirical
laws ; and these successive phases in the application of the
human intellect have marked different epochs in the life of
nations. It has been by adhering closely to this inductive
path, that the great mass of facts has been accumulated
which now forms the solid foundation of the natural sciences.
Two forms of abstraction govern the whole of this class
of knowledge; viz. relations of quantity, comprehending
the ideas of number and magnitude; and relations of
quality, embracing the specific properties of heterogeneous
matter. The first of these forms, more accessible to the
exercise of thought, belongs to the domain of mathematics ;
the other, more difficult to seize, and apparently more mys-
terious, to that of chemistry. In order to submit pheno-
mena to calculation, recourse is had to a hypothetical con-
62 STATE OF EMPIRICAL KNOWLEDGE, AND
stmetion of matter by a combination of molecules and atoms
whose number, form, position, and polarity, determine,
modify, and vary the pheenomena. The suppositions of im-
ponderable matter, and vital forces peculiar to each mode of
organization, have complicated and perplexed the view.
Meanwhile, the prodigious mass of empirical knowledge is
enlarging with increasing rapidity ; and investigating reason
tries at times, with varying success, to break through ancient
forms and symbols invented to effect the subjection of
rebellious matter to mechanical constructions.
We are yet very far from the time, even supposing it
possible that it should ever arrive, when a reasonable hope
could be entertained of reducing all that is perceived by
the senses to the unity of a single principle. The complica-
tion of the problem, and the immeasurable extent of the
Cosmos, seem to forbid the expectation of such success in the
field of natural philosophy being ever achieved by man ; but
the partial solution of the problem — the tendency towards a
general comprehension of the phenomena of the universe —
does not the less continue to be the high and enduring ai}ii
of all natural investigation. For my own part, faithful to the
character of my earlier writings, and to that of the labours
which have occupied my scientific career, in measurements,
experiments, and in investigation of facts, I limit myself in the
present work to the sphere of empirical conceptions. It is
the only ground on which I feel myself able to move without
a sense of insecurity. This mode of treating an aggrega-
tion of observed facts does not exclude their combination by
reasoning, their arrangement under the guidance of leading
ideas, their generalisation wherever it can be justly effected,
and the constant tendency to the discovery of laws. A
GENERALISATION OP LAWS. 63
purely rational conception of the universe, founded on princi-
ples of speculative philosophy, would no doubt assign to the
science of the Cosmos a still more elevated aim. I am far
from blaming efforts which I have not myself attempted,
solely because their success hitherto has been extremely
doubtful. Contrary to the wishes and counsels of those
profound and powerful thinkers who have given new life to
speculations belonging to antiquity, systems of a philosophy
of nature have in our country (Germany) turned men's
minds for a time from the graver studies of the mathemati-
cal and physical sciences. The intoxication of supposed '
conquests already achieved, — a novel and extravagantly sym-
bolical language, — a predilection for formulse of scholastic
reasoning more contracted than were ever known to the
middle ages, — have, through the youthful abuse of noble
powers, characterised the short saturnalia of a purely ideal
science of nature. I say abuse of powers, for superior
minds, which have embraced both speculative studies and
the experimental sciences, took no part in these saturnalia.
The results obtained by serious investigations in the path of
induction, cannot be at variance with a true philosophy of
nature. If there is contradiction, the fault must be either
in the unsoundness of the speculation, or in the exaggerated
pretensions of empiricism, which thinks that it has proved by
its experiments more than is really deducible from them.
The natural world may be opposed to the intellec-
tual, or nature to art, taking the latter term in its higher
sense as embracing the manifestations of the intellectual
power of man ; but these distinctions (which are indicated
in the most polished languages) must not be suffered to
lead to such a separation of the domain of physics from that
VOL. i. <*
6i STATE OP EMPIRICAL KNOWLEDGE, AND
of the intellect, as would reduce the physics of the universe
to a mere assemblage of empirical specialities. Science only
begins for man from the moment his mind lays hold of
matter, — when he strives to subject the mass accumulated by
experience to rational combinations : science is mind applied
to nature. The external world only exists for us so far as we
receive it within ourselves, and as it shapes itself within us
into the form of a contemplation of nature. As intelligence
ind language, thought and the signs of thought, are united
by secret and indissoluble links, so in like manner, and
almost without our being conscious of it, the external world
and our ideas and feelings melt into each other. " External
phsenomena are translated," as Hegel expresses it, in his Plii-
losophy of History, "in our internal representation of them."
The objective world, received into our thoughts and reflected, is
subjected to the unchanging, necessary, and all-conditioning
forms of our intellectual being. The activity of the mind exerts
itself on the elements furnished to it by the perceptions of the
senses. Thus, in the youth of nations, there manifests itself
in the simplest intuition of natural facts, in the first efforts
made to comprehend them, the germ of the philosophy of
nature. These tendencies vary, and are more or less power-
ful, according to national individualities of character, turn
of mind, and stage of mental culture, and whether attained
amidst scenery fitted to excite and charm, or to repress and
c*Jnll the imagination.
History has preserved the record of the varied and hazard-
ous attempts which have been made to comprehend all
phenomena in a theoretical conception, and to discovei
in them a single natural force pervading, setting in motion,
and transforming all matter. In classical antiquity the
GENERALISATION OF LAWS. 65
earliest of these attempts are found in the treatises of the
Ionic school on the principles of things ; treatises in which
the whole of nature was subjected to rash speculation, with
only an extremely scanty basis of observation. This ardour
for deductively determining the essence of things and their
mutual connection from an ideal construction and purely
rational principles, has gradually subsided, with the increas-
ingly brilliant development of the natural sciences resting
on the firm support of observation. Nearer to our own
time, the mathematical portion of natural philosophy has
received the grandest and most admirable enlargement. The
method, and the instrument (analysis), have both been per-
fected together. We are of opinion, that what has been
conquered by means so diverse, — by the ingenious application
of atomic suppositions, — by the more general and more inti-
mate study of phenomena, — and by new and improved
apparatus, — is the common property of mankind ; and cannot
now, any more than in the times of the ancients, be with-
drawn from the free exercise of speculative thought. It
cannot be denied that the results of experience may have
been sometimes undervalued in the course of such processes;
nor ought we to be too much surprised if in the perpetual
fluctuations of speculative views, as the author of Giordano
Bruno (30) has ingeniously remarked, " most men see in
philosophy only a succession of passing meteors ; and even
the grander forms under which she has revealed herself
partake in the popular estimation of the fate of comets,
which they regard as belonging not to the class of perma-
nent celestial bodies, but to that of mere passing igneous
vapours." But the abuse of speculative thought, and the
false paths into which it has sometimes strayed, ought not to
66 STATE OF EMPIRICAL KNOWLEDGE.
lead to a view, dishonouring to intellect, which would regard
the world of ideas as essentially a region of phantom-like
illusions, and philosophy as a hostile power, by which the
accumulated treasures of experimental knowledge are threat-
ened. It is unsuitable to the spirit of the age to reject
with distrust any attempted generalisation of views, or
investigation in the path of reasoning and induction. Nor
is it consonant with a due estimation of the dignity of the
human intellect, and the relative importance of the facul-
ties with which we are endowed, to condemn, at one time,
severe reason applied to the investigation of causes and their
connection, and at another, that exercise of the imagination
which is often precursive to discoveries, — for the achievement
of which the imaginative power is indeed an essential
auxiliary.
67
GENEEAL VIEW OE NATUEE.
WHEN the mind of man attempts to subject to itself the
world of physical phenomena ; — when in meditative contem-
plation of existing things he strives to penetrate the rich
fulness of the life of nature, and the free or restricted opera-
tions of naturalpowers; — he feels himself raised to a height
from whence, as he glances round the far horizon, details
disappear, and groups or masses are alone beheld, in which
the outlines of individual objects are rendered indistinct as
by an effect of aerial perspective. This illustration is
purposely selected in order to indicate the point of view from
whence we design to consider the material universe, and to
present it as the object of contemplation in both its divisions,
celestial and terrestrial. I do not blind myself to the boldness
of such an undertaking. Under all the forms of exposition
to which these pages are devoted, the presentation of a
general view of nature is the more difficult, because we must
not permit ourselves to be overwhelmed by the development
of the manifold and the multiform ; but must dwell only on
the consideration of masses, great either by actual magnitude,
or by the place which they occupy in the subjective range of
ideas. We strive by classification and due subordination of
63 GENERAL VIEW OP NATURE.
phenomena, by penetration into the play of obscure forces,
and by, an animated representation in which the visible
spectacle may be reflected back as in a faithful mirror, —to
conceive and to describe the whole creation (TO nav) in a
manner befitting the dignity of the word Cosmos in its sense
of universe, order of the material world, and beauty or
ornament of that universal order. May the immeasurable
diversity of the elements which crowd together into the
picture of Nature not be found to impair the harmonious
impression of repose and unity, which is the ultimate aim
of every literary or purely artistic composition !
I propose to begin with the depths of space and the
remotest nebulae, and thence gradually to descend through
the starry region to which our solar system belongs, to the
consideration of the terrestrial spheroid with its aerial and
liquid coverings, its form, its temperature and magnetic
tension, and the fulness of organic life expanding and
moving over its surface under the vivifying influence of
light. Such a universal sketch, though drawn with only a
few strokes of the pencil, must comprehend from the un-
measured celestial spaces, to those microscopic animal and
vegetable organisations which inhabit our pools of standing
water and the weathered surfaces of our rocks. All that
can be known by the senses, and all that a persevering
study of nature, in every direction, has revealed up to the
present time, constitute the material from which the repre-
sentation is to be drawn. This representation must contain
within itself the evidence of its fidelity and truth. It does
not require for its completeness the enumeration of all
animated forms, or of all natural objects or processes ; on
the contrary, order and harmony must be maintained by
GENERAL VIEW OF NATURE. 69
carefully resisting the tendency to endless division ; thus
avoiding the danger to which we are subjected by the very
abundance of our empirical riches. • Doubtless, a considerable
portion of the properties of matter are still unknown to us ;
entire series of phaenomena dependant on forces and qualities
of which we are ignorant, remain to be discovered ; and were
it for this reason only, we must fail in attaining a perfect
unity in the view of the whole of the facts of nature.
By the side of the pleasure derived from knowledge
already attained, there subsists, not unmixed with melan-
choly, the longing of the aspiring spirit, still unsatis-
fied with the present, after regions yet undiscovered and
unopened. • Such longing draws still closer the link which,
by ancient and deep-seated laws of the world of thought,
connects the material with the immaterial, and quickens the
interchange between that which the mind receives from
without, and that which it gives back from its own depths.
If, then, Nature (comprising in the word all natural
objects and phenomena) may be regarded as embracing a
range infinite in extent and contents, it also presents to the
human intellect a problem which it cannot wholly grasp,
and of which it can never hope to reach the solution, because
it requires a knowledge of all the forces which act in the
universe. Such an acknowledgment is due, when present and
prospective phsenomena are the objects of that direct investi-
gation, which does not venture to quit the empirical path
and strictly inductive method. But though the constant
effort to embrace the whole remain unsatisfied, the " His-
tory of the contemplation of the Universe" (which is
reserved for a subsequent portion of this work) shows
us how, in the course of centuries, mankind have gradually
70 GENERAL VIEW OF NATURE.
arrived at a partial insight into the relative dependence ot
phsenomena. My duty is to depict that which is known,
according to its present measure and limits. In all that is
subject to motion and change in space, mean numerical
values are the ultimate object ; they are, indeed, the expres-
sion of physical laws ; they shew to us the constant amid
change, the stable amid the flow of phenomena. The advance
of our modern physical science, which proceeds by weight and
measure, is specially characterised by the attainment and pro-
gressive rectification of the mean values of certain quantities.
Thus, the only remaining and widely diffused hieroglyphic
characters of our present writing, — numbers, — reappear, as
once in the Italic school, but now in a more extended sense,
as powers of the Cosmos.
The earnest investigator delights in the simplicity of
numerical relations, indicating the dimensions of celestial
spaces, the magnitudes of heavenly bodies, their periodic
disturbances, the threefold elements of terrestrial magnetism,
the mean pressure of the atmosphere, and the quantity of
heat which the sun dispenses in each year and in each portion
of the year to the several points of the solid and the liquid
surface of our planet. Less satisfied is the poet of nature,
and still less the mind of the curious multitude. To both
of these, Science appears a blank, now that she answers
doubtfully, or rejects as unanswerable, questions to which
replies were, in earlier times, unhesitatingly adventured. In
her severer form and less ample robes she appears deprived
of that seductive grace, with which a dogmatising and sym-
bolising physical philosophy could deceive the reason and
occupy the imagination. Long before the discovery of the
new world, men dreamed of lands in the West, visible from
GENERAL VIEW OF NATURE. 71
the Canaries or the Azores ; and these illusive images were
formed, not by any extraordinary refraction of the rays of
light, but by the longing gaze striving to penetrate the dis-
tant and the unapproached. The fascination which belongs
to such unsubstantial images and illusions was offered abun-
dantly by the natural philosophy of the Greeks, the physics
of the middle ages, and even by those of the centuries which
succeeded them. At the limits of exact knowledge, as from
a lofty island shore, the eye loves to glance towards distant
regions. The belief of the unusual and the marvellous
lends a definite outline to every creation of fancy ; and the
realm of imagination, a fairy land of cosmological, geognos-
tical, and magnetical dreams, becomes uncontrollably blended
with the domain of reality.
Nature, so manifold in signification — sometimes taken
as including all the material creation existing and coming
into existence, sometimes as a power of internal develop-
ment, sometimes is the mysterious prototype of all pheno-
mena— reveals herself to the simple senses and feelings of
man by preference in that which is terrestrial, and closely
allied to himself. I\ is in the animated circle of organic
forms that we first fed ourselves peculiarly at home. It is
where the bosom of the earth unfolds its flowers, and ripens
its fruits, and feeds countless tribes of animals, that the
image of nature comes i&ost vividly before our souls. The
starry vault, the wide expanse of the heavens, belong to the
picture of the universe, ia which the magnitude of the
masses, and the number o\ congregated suns, or faintly
bhining nebulae, excite indeed, our admiration and astonish-
ment, but seem estranged from us by the entire absence of
any immediate impression of 1;heir being the theatres of
72 GENERAL IEW OF MATURE.
'
organic life. The earliest physical views separate between,
and oppose to each other, the heavens and the earth — the
above and the below in space. If, then, our view were
intended to correspond solely to the requirements of
sensuous contemplation, it ought to begin with the
description of our native earth. It should depict first
the terrestrial spheroid ; — its magnitude and form ; its in-
creasing density and temperature at increasiug depths in its
solid or liquid strata; the relative configuration of sea and-
land, and in both the development of organic He in the
cellular tissues of plants and animals; the atmospheric
ocean, with its waves and currents, and forest-cUd mountain
chains which rise like reefs and shoals froir its bottom.
After thus depicting purely telluric relations, the eye would
be raised to the celestial spaces ; the earth, :he well-known
seat of organic development, would now be considered as a
planet taking its place in the series of cosmical bodies
revolving around one of the countless host of self-luminous
stars. This succession of ideas indicates the path pursued
in the earliest mode of contemplation, or that which derives
purely from the senses ; it almost remiids us of the ancient
" sea-girt disk of Earth supporting the Heavens." It begins
in perception, and its course is from the known and near to
the unknown and distant. It corresponds to the method
pursued in our elementary works on astronomy (and which
has much to recommend it ir a mathematical point of
view), of proceeding from the apparent to the real or true
movements of the celestial bodies.
In a work which proposes not so much to shew the
grounds of our knowledge, as to display that which is known,
whether regarded in the present state of science as certain,
GENERAL VIEW OF NATURE. 73
or as merely probable in a greater or less degree., a different
order of succession is to be preferred. Here, therefore, we
do not proceed from the subjective point of view of human
interest : the terrestrial is treated only as a part of the
whole, and in its due subordination. The view of nature
should be general, grand, and free; not narrowed by
proximity, sympathy, or relative utility. A physical cos-
mography, or picture of the universe, should begin, there-
fore, not with the earth, but with the regions of space.
But as the sphere of contemplation contracts in dimen-
sion, our perceptions and knowledge of the richness of
details, of the fulness of physical phenomena, and of the
qualitative heterogeneity of substances, augment. From
the regions in which we recognise only the dominion of
the laws of gravitation, we descend to our own planet, and
to the intricate play of terrestrial forces. The method
thus pursued is the opposite of that which is followed when
conclusions are to be established. The one recounts what
the other demonstrates.
Our knowledge of the external world is obtained through
the medium of the senses. It is by the phsenomena of light
that the presence of matter in the remote regions of space is
revealed to us. The eye is the organ by which we are
enabled to contemplate the universe ; and, for the last two
centuries and a half, telescopic vision has given to later gene-
rations a power of which the limit is yet unattained. The first
and most general consideration in the Cosmos is that of the
contents of space, — the distribution of the material universe,
We see matter " existing in space, partly in the form
of rotating and revolving spheroids differing greatly in
74 CELESTIAL PHENOMENA.
density and magnitude, and partly in that of self-luminous
vapour, dispersed in shining nebulous spots or patches.
If we consider first the nebulous spots, or cosmical vapour
in definite forms, its state of aggregation appears constantly
varying. The nebulae present themselves to the eye in the
form of round or elliptic disks of small apparent magni-
tude, either single, or in pairs which are sometimes con-
nected by a thread of light : when their diameter is greater
their forms vary, — some are elongated, others have several
branches, some are fan-shaped, some annular, the ring being
well defined and the interior dark. They are supposed to
be undergoing various and progressive changes of form, as
condensation proceeds around one or more nuclei in confor-
mity with the laws of gravitation. Between two and three
thousand of such unresolvable nebulae (or, at least, in
which no stars have hitherto been discovered by the most
powerful telescopes), have already been classed, and their
positions determined.
The genetic evolution, or perpetual process of formation,
which appears to be going on in this part of space, has lid
philosophical observers to the analogy of organic phaenomena.
As we see in our forests, at one time, the same kind of tree
in all stages of growth, and receive from this co-existence
the impression of progressive development ; so, in the great
garden of the universe, we seem to see stars in various stages
of progressive formation. The process of condensation,
which was* part of the doctrine of Anaximenes and of the
whole Ionic school, appears to be here going on before our
eyes. This subject of conjoint investigation and conjecture
has a peculiar charm for the imagination. Throughout the
range of animated existence, and of moving forces in the
NEBULA. 75
physical universe, there is an especial fascination in the
recognition of that which is becoming, or about to be, even
greater than in that which is, though the former be indeed
no more than a new condition of matter already existing :
or of the act of creation itself, the original calling forth of
existence out of non-existence, we have no experience, nor
can we form a conception of it.
Besides the comparison of different stages of development
in nebulse which appear more or less condensed towards their
centres, observers have believed that they could recognize
by direct observation at different epochs, actual changes of
form in particular nebulse : in the nebula in Andromeda,
for example ; in the nebula in the constellation of the Ship ;
and in the filamentous portion of the nebula in Orion.
Inequality in the instruments employed, differences in the
state of the atmosphere, and other optical circumstances,
may indeed invalidate part of these results as true historical
elements.
Neither the irregularly-shaped nebulse (to wliich the name
more especially belongs), the separate parts of which are of
unequal brightness, and which may, possibly, as their circum-.
ference contracts, become finally concentrated into stars, —
nor the planetary nebulae, whose circular or slightly oval disks
show throughout a perfectly equable intensity of faint light,
must be confounded with nebulous stars. These are not
stars accidentally projected upon a distant nebulous ground,
but the luminous nebulous matter itself forms one mass
with the body which it surrounds. The often considerable
magnitude of their apparent diameter, and the remote dis-
tance from which their faint light reaches us, show that both
the planetary nebulse and thi nebulous stars must be of
76 CELESTIAL PHENOMENA.
enormous dimensions. New and highly ingenious considera-
tions (31) on the very different effect which distance produces
on the intensity of light of a disk of appreciable diameter,
and of a self-luminous point, render it not improbable that
the planetary nebulae are very remote nebulous stars, in which
the difference between the central star and the nebulous
envelope is no longer sensible even to our telescopic vision.
The magnificent zones of the southern celestial hemisphere,
between 50° and 80°, are especially rich in nebulous stars,
and in unresolvable nebulas. Of the two Magellanic clouds
which revolve around the starless and desert southern pole,
the larger especially appears, by the most recent researches (32),
as a " collection of clusters of stars, composed of globular
clusters and nebulae of different magnitudes, and of large
nebulous spaces not resolvable, which, producing a general
brightness of the field of view, form as it were the
background of the picture." The appearance of these
clouds, that of the brilliant constellation of the Shi]),
the milky way between the Scorpion, the Centaur, and
the Southern Cross, — I may say, the graceful, and pictu-
resque aspect of the whole southern celestial hemisphere,
have left on my mind an ineffaceable impression.
The zodiacal light which rises in a pyramidal form, and con-
stantly adorns the tropical nights with its mild radiance, is
either a vast rotating nebulous ringbetweentheEarthand Mars,
or, less probably, the outermost stratum of the solar atmos-
phere. Besides the luminous clouds and nebulae of definite
form, exact and always accordant observations indicate the ex-
istence and general distribution of an infinitely divided and ap-
parently non-luminous matter, which constitutes a resisting
medium, and manifests itself by diminishing the eccentricity,
SEDEKEAL SYSTEMS. 77
and shortening the time of revolution of Encke's and,
perhaps, also of Biela's comet. "We may conceive of this
impeding ethereal and cosmical matter that it is subject to
motion; that it gravitates, notwithstanding its extreme
tenuity, and is consequently condensed in the vicinity of the
great mass of the sun ; and even that it may be augmented in r
the course of myriads of years by emanations from the tails {
of comets.
If we now leave the consideration of the attenuated va-
porous matter of the immeasurable regions of space (ovpavov
Xoproc)33, whether existing in a dispersed state, as a cosmical
ether without form or limits, or in the shape of nebulae, and
pass to those portions of the universe which are condensed
into solid spheres or spheroids, we approach a class of
phenomena exclusively designated as stars, or as the
sidereal universe. Here, too, we find different degrees
of solidity, or density, in the agglomerated matter. Our
own solar system presents all gradations of mean density
(or relation of volume to mass) . If we compare the planets,
from Mercury to Mars inclusive, with the Sun and with
Jupiter, and the two latter bodies with the still inferior
density of Saturn, we pass through a descending scale, in
which (taking terrestrial substances for illustration) the grada-
tions correspond respectively to the densities of antimony, of
honey, of water, and of deal wood. In comets (which, in point
of number of individual forms, constitute the largest portion
of our solar system), that which we call the head, or nucleus,
allows the light of stars to shine unimpaired through its
substance: perhaps in no case does the mass of a comet \
equal the five-thousandth part of that of the earth,— so
various do the processes of formation appear in the original,
T8 CELESTIAL PHENOMENA.
and, perhaps, still progressive, agglomeration of matter.
Before we pass from the most general considerations to those
which are less so, it is especially desirable to notice this
diversity, not merely as a possibility, but as actually existing.
The purely speculative conceptions of Wright, Kant,
and Lambert, concerning the general arrangement of the
fabric of the universe, and the distribution of matter in
space, have been confirmed by Sir William Herschel in
the surer path of observation and measurement. This
great man, in whom the inspiration of genius was combined
with a spirit of cautious investigation, was the first to
sound the depths of the celestial spaces, in order to deter-
mine the limits and form of the starry stratum of which we
form a part ; the first to enter on the inquiry of the rela-
tions of position and distance between our own region of
the heavens and remote nebulae. William Herschel (as the
inscription on his monument at Upton finely says), broke
through the inclosures of the heavens (ccelorum perrupit
claustra) ; like Columbus, he penetrated into an unknown
ocean, and first beheld coasts and groups of islands, whose
true position remains to be determined by succeeding ages.
Considerations respecting the different intensity of light
in stars, and their relative numbers in equal telescopic fields,
have led to the assumption of unequal distances and distribu-
tion in space of the strata in which they may be conceived to
exist. Such assumptions, in so far as we may attempt to trace
by them the limits of separate portions of the fabric of the
universe, cannot, indeed, offer the same degree of mathema-
tical certainty as is attained in all that regards our solar
system, or the revolution of the double stars with unequal
velocity around a common centre of gravity, or the apparent
OUJl SIUE11EAL SYSTEM. 79
or true movements of the heavenly bodies. If we commence
physical cosmography with the most remote nebulae, we may
feel inclined to compare this portion of our subject with the
heroic, or mythical, periods of history. Both begin in twi-
light obscurity — the one of antiquity, the other of inacces-
sible distance ; and where reality threatens to elude the grasp,
imagination becomes doubly incited to draw from its own
fulness, and to give outline and permanence to undefined
evanescent objects.
If we compare the regions of space to one of the island-
studded seas of our planet, we may imagine we see matter
distributed in groups, whether of unresolvable nebulae of
different ages condensed around one or more nuclei, or in
clusters of stars, or in stars scattered singly. Our cluster
of stars, or the island in space to which we belong, forms a
lens-shaped, flattened, and every where detached stratum,
whose major axis is estimated at seven or eight hundred, and
its minor axis at a hundred and fifty times the distance of
Sirius from the Earth. If we assume that the parallax of Sirius
does not exceed that determined for the brightest of the
stars in the Centaur (0"'9]28), it will follow that light
traverses one distance of Sirius in three years, while nine
years and a quarter are required for the transmission of
the light of 61 Cygni, whose considerable proper motion
might lead to the inference of great proximity. I take
the parallax of this remarkable star (0"'34S3) from
Vessel's excellent first memoir (34). Our cluster of stars
is a disk of comparatively small thickness, divided, at
about a third of its length, into two branches : we are
supposed to be near tin's division, and nearer to the region
of Sirius than to that of the constellation of the Eagle,
VOL.I, it
80 CELESTIAL PHENOMENA.
and nearly in the middle of the starry stratum in the direction
of its thickness.
The place of our solar system, and the form of the whole
lens, are inferred from a kind of stellar scale, i. e., from the
different number of stars seen (as already alluded to) in equal
telescopic fields of view. The greater or less number of
stars measures the relative depth of the stratum in different
directions ; giving, in each case, like the marks on a sound-
ing line, the comparative length of visual ray required to
reach the bottom ; or, more properly, as above and below do
not here apply, the outer limit of the sidereal stratum. In
the direction of the major axis, where the greater number of
stars are placed behind each other, the remoter ones appear
closely crowded together, and, as it were, united by a milky
radiance, and present a zone, or belt, projected on the
visible celestial vault, or sky. This narrow belt is divided
into branches ; and its beautiful, but not uniform, brightness
is interrupted by some dark places. As seen by us on the
apparent concave celestial sphere, it deviates only a few
degrees from a great circle, as we are near the middle
of the cluster, and almost in the plane of the milky
way. If our planetary system was far outside the cluster, the
milky way would appear to telescopic vision as a ring, and,
at a still greater distance, as a resolvable disk-shaped nebula.
Among the many self-luminous moving suns (erroneously
called fixed stars), of which our starry island, or nebula,
consists, our own sun is the only one known to us by direct
observation as a central body, in its relations to spherically-
agglomerated matter, revolving around it under the manifold
forms of planets, comets, and aerolite-asteroids. In the
multiple stars (double stars, or double suns), so far as we
THE SOLAR SYSTEM. 81
have yet investigated them, there does not prevail the same
planetary dependence in respect to relative motion and illu-
mination as that which characterizes our solar system : two
or more self-luminous heavenly bodies (whose planets and
their satellites, if they exist, escape the power of our tele-
scopes), do, indeed, revolve around a common centre of
gravity ; but this centre of gravity falls in a space occupied,
possibly, only by unagglomerated matter, *. e., cosmical
vapour ; whilst, in our system, the centre of gravity is in-
cluded within the surface of a visible central body. If
we choose to consider the sun and the earth, or the earth
ar?d the moon, as double stars, and our whole planetary
system as a multiple star, or group of stars, yet the
analogy suggested by such denominations fails altogether
when we regard illumination, and can only apply to motion
in conformity with the laws of gravitation.
In such a generalisation of cosmical views as accords with
the plan of the present work, namely, with the sketch of a
picture of nature or of the universe, the solar system to
which our earth belongs may most properly be considered
under a two-fold aspect, — first, in reference to the different
classes of the individual bodies which it contains, their mag-
nitudes, forms, densities, and disi-ances apart ; and, second,
in its relation to the other parts of the starry cluster of which
it forms a portion, and to its motion, or change of place,
within the same.
The solar system (i. e., those various material bodies
which revolve round the sun) consists, according to our
present knowledge, of eleven principal planets, eighteen
moons or satellites, and myriads of comets, three of which
(called planetary comets) do not pass beyond the orbits of the
82 CELESTIAL PHENOMENA.
principal planets. We may, with considerable probability,
include within the dominion of our sun, and the immediate
sphere of its central force, a rotating ring of finely,
divided or nebulous matter, situated, perhaps, between the
orbits of Venus and Mars, but certainly extending beyond
that of the earth (35), which is called by us the Zodiacal
Light ; and a host of extremely small asteroids, the paths
of which intersect, or very nearly approach, that of the
Earth, and which present to us the phenomena of aerolites,
or shooting stars. When we take into our consideration
all the varied forms of bodies which revolve round the sun
in more or less eccentric paths, — unless we are inclined, with
the illustrious author of the " Mecanique Celeste," to view
the greater number of comets as nebulous stars, wandering
from one central system to another (36), — we must acknow-
ledge that the planetary system distinctively so called (i. e.
the group of bodies which in only slightly eccentric orbits
revolve around the sun, with their attendant moons,) forms,
not indeed, in mass, but in number, a comparatively small
portion of the entire solar system.
It has been proposed to consider the telescopic planets,
Vesta, Juno, Ceres, and Pallas, with their more eccentric,
intersecting, and greatly inclined orbits, as forming a
middle zone, or group, in our planetary system ; and if we
follow out this view, we shall find that the comparison of
the inner group of planets, comprising Mercury, Venus,
the Earth, and Mars, with the outer group, consisting of
Jupiter, Saturn, and Uranus, presents several striking con*
trasts (37). The planets of the inner group, which are nearer
the -sun, are of more moderate size, are denser, rotate around
their respective axes more slowly in nearly equal periods
83
of about twenty-four hours, are less compressed at the
poles, and, with one exception, that of the Earth, are without
satellites. The external planets, more distant from the sun,
are of much greater magnitude, five times less dense, more
than twice as rapid in their rotation round their axes, more
compressed at their poles, and richer in moons in the pro-
portion of 17 to 1 ; if Uranus has really six satellites as
supposed.
In viewing these general characteristics of the two groups,
we must admit, however, that they cannot be strictly applied
to each of the planets in particular ; nor are there any con-
stant relations between the distances of the planets from the
central body round which they revolve, and their absolute mag-
nitudes, their densities, times of rotation, eccentricities, and
inclinations of orbit and of axis. We know as yet of no inhe-
rent necessity, no natural mechanical law, (such as the great
law of the proportionality of the squares of the periodic
times to the cubes of the mean distances from the sun), con-
necting the above-named six elements of the planets, and
the forms of their orbits, either inter se, or with their mean
solar distances. We find Mars, though more distant from
the Sun than either the Earth or Yenus, inferior to them
in magnitude; being, indeed, that one of the long known
greater planets which most nearly resembles in size Mercury,
the nearest planet to the solar orb. Saturn is less than
Jupiter, and yet much larger than Uranus. The zone of the
telescopic planets, which are so inconsiderable in point of
volume, viewed in the series of distances commencing from
the Sun, comes next before Jupiter, the greatest in size of
all the planetary bodies ; and yet the disks of these small
planets (whose apparent diameters scarcely admit of measure-
84 CELESTIAL PHENOMENA.
ment) are less than twice the size of Prance, Madagascar,
or Borneo. Remarkable as is the small density of all the
colossal planets which are farthest from the sun, yet neither
in this respect can we recognise any regular succession (38).
Uranus, even if we assume as correct the small mass of
a4ao5J assigned by Lamont (39), appears to be denser than
Saturn ; and (although the inner group of planets differ but
little from each other in this particular) we find both Venus
and Mars less dense than the Earth, which is situated between
them. The time of rotation decreases, on the whole, with
increasing solar distance, but yet it is greater in Mars than
in the Earth, and in Saturn than in Jupiter. Among all
the planets, the elliptic paths of Juno, Pallas, and Mercury,
have the greatest eccentricity; Venus and the Earth,
which immediately follow each other, have the least : while
Mercury and Venus (which are likewise neighbours) present,
in this respect, the same contrast as do the four smaller
planets, whose paths are so closely interwoven. The eccen-
tricities of Juno and Pallas are nearly equa], but are each
three times as great as those of Ceres and Vesta. Nor is
there more regularity in the inclination of the orbits of the
planets towards the plane of projection of the ecliptic, or in
the position of their axes of rotation, relatively to their
orbits; on which latter position the relations of climate,
seasons of the year, and length of the days depend, more
than on the eccentricity. It is in the planets which
have the most elongated ellipses — Juno, Pallas, and Mer-
cury— that we find, though not in equal proportion, the
greatest inclination of the orbits to the ecliptic. The path
of Pallas is almost comet-like, its inclination twenty-six
times greater than that of Jupiter; whilst, in the little
PLANETS. 85
Vesta, which is so near Pallas, the corresponding angle of
inclination is one-fourth less, or scarcely six times greater
than in Jupiter. Neither do we find a regular order of
succession in the position of the axes of the few planets
(four or five), of the planes of rotation of which we have at
present any certain knowledge. Judging by the position of
the satellites of Uranus (of two of which, *'. e., the second
and the fourth, a fresh and certain view has been recently
obtained), the axis of this the outermost of all the planets,
is inclined barely 11° to the plane of its orbit; and Saturn
is placed intermediately between this planet, in which the
axis of rotation almost coincides with the plane of its orbit,
and Jupiter, whose axis is almost perpendicular to it.
In this enumeration of forms in space, they have been
depicted simply as they exist, rather than as objects of
intellectual contemplation, or in inherent causal connec-
tion. The planetary system, in its relations of absolute
magnitude, relative position of the axes, density, time of
rotation, and different degrees of eccentricity of the orbits,
has, to our apprehension, nothing more of natural necessity,
than the relative distribution of land and water on the sur-
face of our globe, the configuration of continents, or the
elevation of mountain chains. No general law in these
respects is discoverable, either in the regions of space, or in
the irregularities of the crust of the earth. They are facts
in nature, which have arisen out of the conflict of various
forces acting under unknown conditions. We apply the
term accidental to what in the planetary formation we
are unable to elucidate genetically. If the planets have been
formed by the progressive condensation of rings of nebulous
matter concentric with the sun, the different thickness,
86 CELESTIAL PHJENOMEXA.
.
unequal density, temperature, and electro-magnetic tension of
these rings, may have occasioned differences of form in the
sphcroidally condensed matter, as the amount of tangential
velocity and small variations in its directions may have caused
the diversity of form and inulmotion in the elliptic orbits.
Attractions of ma?s, and the laws of gravitation, have, no
doubt, been influential here, as well ns during the changes
which have produced the irregularities in the terrestrial
surface ; but we cannot infer, from present forms, the whole
series of conditions which may have been passed through.
Even the so-called law of the distances of the planets from
the sun, (which led Kepler to conjecture the existence of
some planet filling up the void between Mars and Jupiter),
has been found numerically inexact for the distances between
Mercury, Venus, and the Earth, and requires an arbitrary
supposition in the first member of the series.
The eleven hitherto discovered primary planets -re-
volving round our Sun are attended certainly by fourteen,
and probably by eighteen secondary planets — moons, or
satellites ; the primary planets being themselves the central
bodies of subordinate systems. We seem to recognise here
in the fabric of the universe, an arrangement somewhat
similar to that so often shown to us in the development of
organic life, where, in the manifold combinations of groups
of plants or of animals, the typical form is repeated in subor-
dinate circles. The secondary planets, or satellites, are more
frequent in the outer region of our planetary system,
situated beyond the intersecting orbits of the telescopic
planets; none of the planets of the inner division have
satellites, except the Earth, whose moon is of great relative
magnitude its diameter being to that of the earth as one to
SATELLITES. 87
four, whereas the diameter of the largest of all known satel-
lites— the sixth of Saturn — is supposed to be one-seven-
teenth, and that of the largest of Jupiter's satellites — the
third — only one-twenty-sixth part of the respective diameters
of the planets round which they revolve. The planets most
rich in satellites are found among those most remote, of
greatest magnitude, least density, and greatest compression
According to the most recent measurements of Madler,
Uranus is the planet which has the greatest compression,
viz. 9^3. The Earth and her moon are 207200 miles
apart, and the differences of mass (40) and diameter in these
two bodies are much less than we are accustomed to meet
with elsewhere in the solar system, between bodies of dif-
ferent orders, or primary planets and their satellites. The
density of the Moon is -f- less than that of the Earth, while
the second satellite of Jupiter appears, if we may place suffi-
cient dependence on the determinations of magnitude and
of mass, to be even actually denser than the great planet
round which it revolves.
Among the fourteen satellites concerning which investi-
gation has arrived at some degree of certainty, the system of
the seven satellites of Saturn offers the greatest contrasts,
both of absolute magnitude and of distance from the central
planet. The sixth satellite is probably but little smaller
than Mars (whose diameter is twice that of our moon),
while, on the other hand, the two innermost satellites (dis-
covered by the forty-foot telescope of "William Herschel in
1789, and seen again by John Herschel at the Cape of
Good Hope, by Yico at Rome, and by Lamont at Munich)
belong, perhaps, together with the remote moons of Uranus,
to the smallest cosmical bodies of our solar system, being
88 CELESTIAL PHENOMENA.
visible only under peculiarly favourable circumstances, and
with the most powerful telescopes. After the sixth and
seventh of the satellites of Saturn, comes, in order of volume,
the third and brightest of Jupiter's. The diameters of satel-
lites deduced from measurements of the apparent magnitude
of their small disks are subject to many optical difficulties ;
fortunately, the calculations of astronomy, which shew the
movements of the heavenly bodies as they will appear to
us when viewed from the earth, depend much more on
motion and mass than on volume.
The absolute distance of any satellite from the planet
round which it revolves is greatest in the case of the outer-
most (or seventh) of the satellites of Saturn, being above
two millions of geographical miles, or ten times the distance
of our moon from the earth. The distance of the outermost,
or fourth, satellite of Jupiter from that planet is only
1040000 miles; the distance between Uranus and his
sixth satellite (supposing the latter really to exist) amounts
to 1360000 miles. If we compare in each subordinate
system the volume of the central planet with the dimensions
of the orbit of its outermost satellite, we obtain a new series
of numerical relations. The distances of the outermost
satellites of Uranus, Saturn, and Jupiter, expressed in semi-
diameters of the respective central planets, are as 91, 64,
and 27 ; and in this mode of estimation, the outermost
of the satellites of Saturn appears to be only a little (-^ )
farther from the centre of that planet, than our Moon
is from the Earth. The satellite, which is nearest to
its central planet, is undoubtedly the first or innermost
of Saturn, and it offers, moreover, the only example of a
period of revolution of less than twenty -four hours : its
SATELLITES. 89
distance from the center of he tplanet is, according to
Madler and Wilhelrn Beer, 2*47 semi-diameters of Saturn,
or 80088 miles; from the surface of the planet, therefore,
only 47480, and from the outermost edge of the ring, only
4916 miles. The traveller may find pleasure in realising
to his imagination the smallness of this amount, by remem-
bering the statement of a distinguished navigator, Captain
Beechey, that, in three years, he had sailed over 72800 geo-
graphical miles. If we estimate distances, not in absolute
measure, but in semi-diameters of the primary planets, we
find that the first or nearest of Jupiter's satellites (which, in
absolute distance, is 26000 miles farther from the centre of
that planet than our moon is from the earth) is only six
semi-diameters of Jupiter from its centre, while our moon is
dista,nt from us fully 60^ semi-diameters of the Earth.
In the subordinate systems of satellites or secondary
planets, we see reflected in their relations to their primary
planets and to each other, all the laws of gravitation which
regulate those primary planets in their revolutions round the
sun. The twelve moons attendant on Saturn, Jupiter, and
the Earth, all move, as do their primary planets, from west to
east, and in elliptical orbits differing little from circles. It
is only the earth's moon, and probably the first or inner-
most of the satellites of Saturn, which have orbits
more elliptic than that of Jupiter. The eccentricity of
the sixth satellite of Saturn, which has been so accurately
observed by Bessel, is 0'029, and is greater than that of the
Earth. Near the extreme limits of the planetary system,
where, at a solar distance nineteen times greater than that of
the Earth, the centripetal force of the solar orb is considera-
bly diminished, the satellites of Uranus (which have, it ia
90 CELESTIAL PHENOMENA.
true, been as yet but imperfectly investigated) exhibit some
remarkable differences from the movements of other satel-
lites and planets. In all other cases, the orbits are but
little inclined to the ecliptic, and the movements are from
west to east, including Saturn's rings, which may be regarded
as belts formed of an aggregation of satellites; but the
satellites of Uranus are almost perpendicular to the ecliptic,
and the direction of their movement, as confirmed by Sir
John Herschel from many years of observation, is retrograde,
or from east to west. If the primary and secondary planets
have been formed by condensation from annular rotating
portions of the primitive atmospheres of the sun and of the
principal planets, there must have been in the rings of va-
pour winch revolved round Uranus, singular and unknown
relations of retardation or counteraction, to have occasioned
the second and the fourth satellite to revolve in a direction
opposite to that of the rotation of the central planet.
It appears highly probable, that the times of rotation of
all secondary planets, or satellites, are the same as their
times of revolution round their primary planets ; so that they
always present to the latter the same face. In the case
of the moon, inequalities, consequent on small variations
in the revolution, cause, however, fluctuations of from
six to eight degrees, or an apparent libration in longitude
as well as in latitude, which renders more than one-half
of her surface visible to us at different times, showing us
sometimes more of her western and southern limbs, and
sometimes more of her eastern and northern. It is this
libration (41) which enables us to see the annular mountain
of Malapert, sometimes concealed from us by the moon's
southern pole, the arctic landscape round the crater of
COMETS. 91
Gioja, and the great grey plain near Endymion, which
exceeds, in superficial extent, the Mare Vaporum. Three-
sevenths of the moon's surface are at all times concealed
from the earth, and must always remain so, unless new
and unexpected disturbing forces are brought into action.
These cosmical relations remind us involuntarily of
nearly similar ones in the intellectual world, where, in
the domain of deep research and of meditation on the mys-
terious elaborations of nature, and on primeval creation,
there are regions similarly turned from our view and appa-
rently unattainable, of which a narrow margin has for
thousands of years presented itself, from time to time tc
the human race, glimmering now in true, now in uncertain
light.
Having thus considered, as products of a single tan-
gential impulse, and closely connected with each other
by mutual attraction, the primary planets, their satellites,
and the concentric rings which belong to one of the
outermost planets, we have still to notice, — among
the cosmical bodies which revolve around the sun in
paths of their own, and receive light from him,— the
unnumbered host of comets. If we estimate according to
the rules of the calculus of probabilities, the equable dis-
tribution of the paths of these bodies, the limits of their
perihelia, and the possibility of their remaining invisible to
the inhabitants of the earth, their possible numbers
will be an amount of myriads astonishing to the irna^
gination. Kepler, with his characteristic liveliness of expres-
sion, said, even in his day, " there are more comets in space
than fishes in the ocean/' As yet, however, we hardly
92 CELESTIAL PHENOMENA.
possess as many as one hundred and fifty calculated paths of
comets ; but we have notices more or less precise of the
appearance of six or seven hundred of such bodies, and of
their passage through known constellations. Whilst the
classic nations of the West, the Greeks and the Bomans, do,
indeed, sometimes mention the place in the heavens where a
comet was first seen, but never afford us information respect-
ing its apparent path, the literature of the Chinese (who
observed nature diligently, and carefully recorded everything),
supplies us with circumstantial notices of the comets seen
by them, and of the constellations which each passed
through. These notices extend back to more than five
centuries before the Christian era, and many of them are
still found useful in astronomy (42). Of all planetary bodies,
comets, — though their mean mass is probably much less than
the five-thousandth part of that of the earth, — are those which
occupy the greatest space, their wide-spreading tails often
extending over many millions of miles. The cone of
light-reflecting gaseous matter which radiates from them has
been found in some instances, as in 1680 and 1811, to equal in
length the distance of the earth from the sun, or that of a line
including the orbits of the two planets, Yenus and Mercury.
It is even probable that the emanations from the comets of
1811 and 1823 mixed with our atmosphere.
Comets show such diversities of form, diversities belong-
ing rather to the individual than to the class, that the
description given of one of these " wandering light-clouds"
(as they were called by Xenophanes, and Theon of Alex-
andria, contemporaries of Pappus), can only be applied with
much caution to another. The fainter telescopic comets are
f, 0'0 0 of that of the earth, has assigned
with a certain degree of probability, for the average mass
of comets, a quantity far below even To-oVo-o °f the
earth's mass, or only about l a!0 -0 of that of the moon (54).
The passage of Biela's comet across the earth's orbit must
not of course be confounded with its proximity to, or
encounter with, our globe itself. "When this passage took
place on the 29th of October, 1832, the earth was a full
month in time from the point of intersection of the two
paths. The orbits of Encke's and Biela's comets also inter-
sect each other ; and it has been justly remarked, that in the
course of the many perturbations which such small bodies
suffer from the greater planetary masses, there is a possibility
of their meeting (55) ; and that should this take place about
the middle of the month of October, the inhabitants of the
Earth might behold the extraordinary spectacle of an encoun-
ter between two cosmical bodies, and possibly of their mutual
penetration and amalgamation, or of their destruction by
exhausting emanations. Such events, the consequences either
of deflection produced by disturbing masses, or of originally
intersecting orbits, may have taken place frequently in
the course of millions of years, and in the vast extent of
immeasurable space ; they would, however, be isolated occur-
rences, having as little general influence on other cosmical
COMETS. 101
forms, as the breaking forth or extinction of a single volcano
has in our less extensive sphere.
A third planetary comet of short period was discovered
on the 22d of November, 1843, at the Paris Observatory,
by M. Faye. Its elliptic path approaches much more nearly
to a circle than that of any of the comets previously known
to us, and is included between the orbits of Mars and
Saturn; passing, according to Goldschmidt, beyond the
orbit of Jupiter. This comet is therefore one of the very
few whose perihelia are beyond the orbit of Mars ; its period
of revolution is 7*29 years, and the present form of its
path may perhaps be due to the near approach which it
made to the great mass of Jupiter at the end of the yeai
1839.
If we consider all comets moving in elliptic orbits as mem-
bers of our solar system, and class them by the lengths of
their major axes, the amount of their excentricities, and the
duration of their periods of revolution, it seems probable
that in the last-named respect, the three comets of Encke,
Biela, and Paye, are most nearly approached by the comet
which Messier discovered in 1766 (regarded by Clausen as
identical with the third comet of 1819), and by the fourth
comet seen in the same year (1819), discovered by Blan-
pain, and thought by Clausen to be identical with the
comet of 1743. The orbits of the last-mentioned comet,
as well as that of LexelPs, seem to have undergone great
alteration by the proximity and attraction of Jupiter ; their
periods of revolution appear to be only from five to six years,
and their aphelia take place near the orbit of Jupiter.
Among comets whose periods range from seventy to seven ty-
six years, we should name, first, Halley's which has been
102
CELESTIAL PHENOMENA.
of so much importance in theoretical and physical astro-
nomy, and whose last appearance in 1835 was less
brilliant than might have been expected from preceding
ones) ; the comet of Gibers (of the 6th of March, 1815);
and the one discovered by Pons in 1812, the elliptic
orbit of which was determined by Encke. The two latter
comets were invisible to the naked eye. We now know,
with certainty, of nine returns of Bailey's comet, for Lau-
gier's (56) calculations have recently demonstrated the identity
of its orbit with that of the comet of 1378, mentioned in
the Chinese tables of comets, for the knowledge of which we
are indebted to Edouard Biot. During the interval between
its first and last recorded appearances, in 1378 and 1835,
its periods of revolution have fluctuated between 74'91
years and 77'58 years, the mean being 76-1.
Contrasted with the cosmical bodies of which we have
been speaking are a group of comets requiring many thou-
sand years to perform their revolutions, of which the
periods can only be determined with great difficulty and
uncertainty. Argelander assigns a period of 3065 to the
fine comet of 1811, and Encke a period of upwards of
8800 years to the awfully grand one of 1680. Accord-
ing to such views, these bodies recede respectively to dis-
tances from the Sun twenty-one and forty-four times greater
than that of Uranus, or to 83600 and 70400 millions
of miles. At these enormous distances, the attractive force
of the Sun still subsists ; but whilst the motion of the comet
of 1680 at its perihelion is 212 miles in a second, being
thirteen times greater than that of the Earth, its velocity at
its aphelion is scarcely ten feet in a second, being only
three times greater than that of our most sluggish European
COMETS. 103
rivers, and but half that which I found in the Cassiquiare,
an arm of the Orinoco. Amongst the countless host of un-
calculated or still undiscovered comets, it is highly proba-
ble that there are many, the major axes of whose orbits may
far exceed even that of the comet of 1680. In order to
afford through the medium of figures some idea, — I do not
say of the extent of the sphere of attraction, but, — of the
distance in space of a fixed star or other sun from the aphe-
lion of the comet of 1680, (the one of the bodies of our
solar system which, according to our present knowledge,
attains the greatest remoteness,) I would here remind the
reader, that, according to the most recent determinations of
parallax, even the nearest fixed star is at least 250 times
more distant from our Sun than this comet at its aphelion.
The comet's distance is only 44 times that of Uranus, whilst
that of a Centauri is 11000, and of 61 Cygni, according to
Bessel's determination, 31000 times that of Uranus.
Having thus considered the greatest known distances of
comets from the central body, we may proceed to notice
instances of the greatest proximity hitherto measured. The
smallest distance between a comet and the Earth occurred
in the case of Lexell and Burkhardt's comet of 1770, which
has acquired so much celebrity from the perturbations it
underwent from the mass of Jupiter. On the 28th of June,
1770, this comet's distance from the Earth was only six
times that of the Moon from the Earth. The same comet
passed twice, in 1767 and in 1769, through the system of
the four satellites of Jupiter, without causing the slightest
sensible derangement in these small bodies, whose move-
ments are so well known. The great comet of 1680, when
at its perihelion on the 17th of December, was only
104 CELESTIAL PHENOMENA.
one-sixth of the sun's diameter from the surface of that
body; an approach eight or nine times nearer than Lsxell's
comet made to the Earth, and equal to only seven-tenths of
the Moon's distance from the Earth. Owing to the feeble-
ness of the light of distant comets, perihelia which take
place beyond the orbit of Mars can very seldom be observed
by the inhabitants of the earth ; and of all the comets wliich
have been computed hitherto, that of 1729 is the only one
which has its perihelion between the orbits of Pallas and
Jupiter ; it was even observed beyond the latter planet.
Since a degree of scientific knowledge, sometimes
sound, but oftener vague and partial, has extended into
wider circles of social life, the fears of possible evils
threatened by comets have perhaps rather increased in
weight as their direction has become more definite. The
certainty that within the known planetary orbits there are
comets which visit our regions at short intervals, — the con-
siderable perturbations which their paths undergo by the
attractions of Jupiter and Saturn, whereby apparently harm-
less bodies might be converted into dangerous ones, — the
intersection of the Earth's orbit by that of Biela's comet, —
the recognition of the existence of a cosmical ether, wliich
as a retarding medium tends to contract all orbits, — the
differences between individual comets, which allow of the sup-
position of considerable diversity in the mass of the nucleus,
— are motives of alarm which by their number and variety
are fully equivalent to the vague fears which prevailed in
former centuries of "fiery swords," and "long haired
blazing stars," threatening universal conflagration. The
tranquillising considerations which, on the other hand,
have been derived from the calculus of probabilities, being
AEROLITES, OR METEORIC STONES. 105
addressed to the understanding rather than to the imagina-
tion, modern science has been accused, with some degree of
justice, of only endeavouring to allay fears which she has
herself contributed to excite. That the unexpected and extra-
ordinary should oftener excite fearthan joy or hope(57), springs
from a source more deeply seated in our common nature.
The strange aspect of a large comet, its faint nebulous gleam,
its sudden appearance in the vault of heaven, have almost
always, and in all regions of the earth, been viewed as the
portentous heralds of impending change in the established
order of things. The phenomenon itself being of short dura-
tion, its reflection is the more naturally looked for in cotem-
poraneous or immediately succeeding events, and it is seldom
difficult to fix on some incident which may be interpreted as
the calamity foreshewn. Inourowntime, however, the popular
mind has taken another and more cheerful, though singular,
direction in respect to comets. Among the German vine-
yards, in the beautiful valleys of the Rhine and the Moselle,
a favourable influence on the ripening of the grape and on
the quality of the wine has been ascribed to these bodies
long regarded as so ill-omened : nor has experience of a
contrary kind, which has not been wanting in these days
when comets have been so often seen, been able to shake
the belief in this meteorological fable of wandering heat-
imparting stars.
I now proceed from the consideration of comets to that
of another and still more enigmatical class of bodies ; namely,
to those minute asteroids, which, when they arrive in a frag-
mentary state within our atmosphere, we designate by the
names of "aerolites," or "meteoric stones." If I dwell at
1 06 CELESTIAL PHENOMENA.
greater length on these phenomena as well as on comets,
and notice particular cases more than might appear suitable
in a general view of nature, it is not without a purpose.
The great diversity of character in different comets has been
already mentioned. The little knowledge which we yet pos-
sess of the physical qualities of these bodies, renders it
difficult to separate the essential from the accidental in phse-
nomena recurring at intervals, and which have been observed
with very unequal degrees of accuracy. It is only the mea-
suring and computing parts of the astronomy of comets,
which, in modern times, have made such admirable progress:
in the present imperfect state of our knowledge, therefore, a
scientific consideration must restrict itself to physiognomical
diversity in the nucleus and tail, — to instances of remarkable
approximation to other cosmical bodies, — and to extreme
cases either of dimensions of orbit, or of periods of revolution.
In these phenomena, as well as in' those which will next be
treated of, fidelity to nature can only be sought in the
careful description of individual instances, and by such an
animated and graphic mode of expression, as may serve to
bring the reality vividly before the mind.
Shooting stars, fire balls, and meteoric stones, are with
great probability regarded as small masses moving with
planetary velocities in space, and revolving in conic sections
round the Sun, in accordance with the laws of universal
gravitation. These masses approach the Earth in their
path, are attracted by her mass, and enter our atmosphere,
becoming luminous at its limits ; when they frequently let
fall stony fragments, heated in a greater or less degree, and
covered with a shining black crust. A careful investigation
of what has been observed at the epochs when periodic
AEROLITES. 107
showers of shooting stars fell in Ciimana in 1799, and in
North America in 1833 and 1834, shews, that balls of fire
and shooting stars are not only often contemporaneous and
intermingled, but that they pass gradually one into the
other, whether we compare the magnitude of their disks, or
the trains which accompany them, or the velocities of their
movement. While there are exploding and smoke-emitting
balls of fire, which are luminous even in the bright sunshine
of a tropic day(58), and sometimes exceed in size the apparent
diameter of the Moon, — there are, on the other hand, shooting
stars which fall in immense numbers, and are of such small
dimensions, that they exhibit themselves only as moving
points, or as phosphorescent lines (59) . Whether among the
many luminous bodies which shoot across the sky, there may
not be some of a different nature from others, still remains un-
certain. In the equinoctial zone, I received the impression
that, both on the low burm'ng plains, and at elevations of
twelve or fifteen thousand feet, falling stars were there more
frequent, — of brighter colours, — and more often accompanied
by long brilliant trains of light, than in the colder latitudes ;
but doubtless this impression was occasioned solely by the
exceeding transparency of the tropical atmosphere, which
enables the eye to penetrate farther into its depths (6o). Sir
Alexander Burnes extols, as a consequence of the serenity
and clearness of the air and sky in Bokhara, the brilliant
and frequently recurring spectacle of variously coloured
meteors.
The connection of meteoric stones with the more splendid
phsenomenon of fire-balls, and the fact that meteoric stones
sometimes fall from fire-balls with a force which causes them
to sink to a depth of from ten to fifteen feet into the earth,
108 CELESTIAL PHENOMENA.
have been shewn, among many other instances, by the fulls
of aerolites observed at Barbotan, in the Departement des
Landes in France (24th July, 1790), at Sienna, (16th
June, 1794), at Weston in Connecticut (14th December,
1807), and at Juvenas in the Departement derArdeche, (15th
June, 1821). In other instances, a small and very dark
cloud forms suddenly in a perfectly clear sky, and the
stones are hurled from it with a noise resembling repeated
discharges of cannon. Such a cloud, moving over a whole
district of country, has sometimes covered it with thousands
of fragments, very various in size, but similar in quality.
A phenomenon of still more rare occurrence took place on
the 16th September, 1843, when a large aerolite fell at
Kleinwenden, not far from Mulhausen, accompanied by a
thundering noise, but with a clear sky in which no cloud
was formed. As further evidence of the affinity between
fire-balls and shooting stars, it should be noticed that fire-
balls, from which meteoric stones have descended, have some-
times been seen, as at Angers, on the 9th of June, 1822, of
a diameter hardly equal to that of the small Roman candles
in our fire-works.
"We have as yet scarcely any knowledge in regard to the
physical and chemical processes which contribute to the
formation of these phenomena. Whether the particles, of
which the compact meteoric masses are composed, exist
originally in a fluid form (as in comets) and only begin to
condense within the fire-ball at the moment when it becomes
luminous to our sight, — or what takes place within the
bosom of the dark cloud from which sounds resembling
thunder are sometimes heard for minutes before the stones
are precipitated from it, — or whether, in the case of smaller
AEROLITES. 109
shooting stars, there falls any compact substance, or only a
meteoric dust (61), containing iron and nickel., — are questions
still wrapped in great obscurity. "We know, by measure-
ment,, the astonishing and wholly planetary velocity of shoot-
ing stars, fire-balls, and meteoric stones; in this respect,
therefore, we are able to recognise what is " general" and
" uniform" in the phsenomena ; but the genetic and cosmical
premises, the successive transformations undergone, are
not known to us. If meteoric stones circulate in space
in already consolidated and dense masses (62) (less dense, how-
ever, than the mean density of the earth), we must suppose
that they form very small nuclei, which, surrounded by in-
flammable vapours or gases, constitute fire-balls of from 500
to 2600 feet in actual diameter, as inferred in some of the
largest amongst them from observations of their height
and apparent diameter. The largest meteoric masses yei
known to us are those of Bahia in Brazil, and of Otumpa,
described by Rubin de Celis : these are seven and
seven and a half feet in length. The meteoric stone of
JEgos Potamos, celebrated in antiquity, and mentioned in
the Chronicle of the Parian Marbles, and which fell about
the year of the birth of Socrates, has been described as being
of the size of two millstones, and equal in weight to a full
waggon load. Notwithstanding the failure of the efforts of
the African traveller, Browne, I have not given up the hope
that this Thracian meteoric mass, which must have been so
difficult to destroy, may be found, after the lapse of more than
2300 years, by some of the European visitors to countries
which have now become so easy of access. We learn by a
document lately discovered by Pertz, that the enormous
aerolite wlu'ch, in the beginning of the tenth century, fell into
110 CELESTIAL PHENOMENA.
the river near Narni, projected nearly four feet above the sur-
face of the water. It must be remarked that these meteoric
stones, whether ancient or modern, cannot be regarded as
more than principal fragments of the mass which exploded
in the fire-ball, or descended from the dark cloud.
When we consider the mathematically-proved enormous
velocity with which meteoric stones arrive at the earth from
the extreme limits of the atmosphere, and with which balls
of fire move in a more lengthened course through its denser
strata, it appears to me highly improbable that these metal-
liferous masses of stone, with their imbedded and perfectly-
formed crystals of olivine, labradorite, and pyroxene, should
have condensed from a gaseous state into a solid nucleus in
so short an interval of time. Even when the falling pieces
differ from each other in chemical composition, they almost
always show the peculiar characters of a fragment, having
often a prismatic, or truncated pyramidal form, with slightly
curved faces and rounded angles. But whence this frag-
mentary character (first recognised by Schreibers) in a
rotating planetary body ? Here, as in the sphere of organic
life, there is obscurity in all that belongs to the history of
development. Meteoric masses kindle and become luminous
at elevations which must be supposed to be almost
entirely deprived of air. Biot's recent investigations
on the important phenomena of twilight (63) even reduce
considerably the height of the line which has been
usually, but somewhat hazardously, termed the " limit" of
the atmosphere; but luminous processes may take place
without the presence of oxygen, and Poisson has imagined
| that the ignition of aerolites occurs far beyond the range of
\ our atmosphere. In treating of meteoric stones, as well as
AEUOLITES. Ill
of the larger cosmical bodies of our solar system, it is only
in what is subject to calculation and to geometric measure-
ment that we feel ourselves on safe or solid ground. As
early as 1686, Halley pronounced the great ball of fire seen
in that year, the movement of which was opposite to that of
the Earth in her orbit(64), a cosmical phenomenon; but it was
not until 1794, that Chladni, with remarkable acuteness,
recognised the general connection between fire-balls and those
stones which had been known to fall through the air, and
the motion of the former bodies in space (65). A brilliant con-
firmation of this view of the cosmical origin of these phseno-
mena has since been furnished by Denison Olmsted, of New-
haven in Massachusetts, who, from the concurrent testimony
of all the observers of the celebrated fall of meteors, or shoot-
ing stars, which took place on the 12th or loth of November,
1833, has shewn, — that all these bodies, whether fire-balls or
shooting stars, proceeded from the same quarter of the
heavens, i. e. from a point near the star y Leonis, — and that
this continued to be the point, although in the time during
which the phsenomenon was observed, the star materially
altered both its apparent altitude and azimuth. This inde-
pendence of the earth's rotation showed that the luminous
bodies came from without, i. e. that they entered our atmo-
sphere from the external regions of space. From Encke's
computation (66) of the whole of the observations which were
made in the United States of North America, between the
latitudes of 35° and 42°, it follows that these meteors
all proceeded from the point in space towards which the
motion of the Earth was then directed. In the subsequent
great falls of shooting stars in the month of November,
observed in 1831- and 1837 in North Am erica, and in 1S3S
VOL. i. K
112 CELESTIAL PHENOMENA.
in Bremen, the same general parallelism of the paths of the
meteors, and the same direction from the constellation of the
Lion, were recognised. The periodical falls of shooting stars
which take place at other parts of the year, are also supposed
to show greater parallelism of direction than is the case with
those which appear sporadically at other seasons. A periodical
recurrence, similar to that of November, has been noticed in
the month of August; in which month, in 1839, it was
observed that the meteors came from a point in the heavens
situated between Perseus and Taurus, towards the latter of
which constellations the Earth was then moving. This pecu-
liarity of the phenomenon (viz., the retrograde direction,
both in November and in August), is especially deserving of
being confirmed or refuted by very exact and careful obser-
vation on future occasions.
The heights of shooting stars, i. e. the heights at which
they first become visible, as well as those at which their visibility
ceases, are exceedingly various, fluctuating from 16 to 140
miles. This important result, and the enormous velocity of these
problematical asteroids, were first shown by Benzenberg and
Brandes, from simultaneous observations and determinations
of parallax, at the two extremities of a base line of 46000
(49020 English) feet in length (6?) . The relative velocity of
their motion was from eighteen to thirty-six miles in a
second; and similar, therefore, to that of the planets (6S).
This planetary velocity, and the retrograde or opposite direc-
tion of the paths of the meteors to that of the Earth, are the
principal grounds which are considered subversive of that
hypothesis wliich attributes the origin of aerolites to the
supposed active volcanoes of the Moon. All numerical
hypotheses of a greater or less volcanic force on a small
AETIOUTES. 118
cosmicai body not surrounded by an atmosphere, must
be in their nature exceedingly arbitrary. The reaction of
the interior of such a body against its crust may, indeed, be
imagined to be ten times, or even a hundred times, more
powerful than that of our present terrestrial volcanoes. The
direction of masses discharged from a satellite revolving from
west to east, might also appear retrograde, in consequence of
the Earth arriving later at the point in her orbit where those
masses falL If, however, we duly weigh all the circumstances,
which I have thought it necessary to recount lest I should
seem to make assertions without having sufficient ground for
their support, we shall find the lunar origin (69) of meteoric
stones to be dependent on a number of different conditions
whose concurrence would be requisite in order to change the
simply possible into the actual. It appears more in analogy
with our other views of the formation of the solar system, to
admit the separate existence of small planetary masses circu-
lating independently in space.
It is very probable that a large portion of these minute
cosmicai bodies may continue their course round the sun
undestroyed by the vicinity of our atmosphere, and suffering
only an alteration in the eccentricity of their orbits by the
attraction of the earth. It is possible, therefore, that they
first become visible to us after many revolutions. The sup-
posed ascent of shooting stars and balls of fire which Chladni
attempted, not very happily, to explain by the reaction
of the air strongly compressed in their descent, seems,
at first sight, a consequence of some unexplained tangential
force tending to throw off the meteors from the earth : but
Bessel has asserted, on theoretical grounds, the im-
probability of the supposed facts ; and this has been sinc«
114 CELESTIAL PHENOMENA.
confirmed by Peldt's careful calculations, shewing that, for
want of perfect simultaneity in the observed disappearances,
an upward movement cannot be regarded as a result of
observation (70). Future researches must decide whether,
as Olbers supposes, the explosion of shooting stars, and the
ignition of fire-balls, may not occasionally impel the
meteors upwards, or otherwise influence the direction of
their paths.
Shooting stars fall either singly or sporadically, or in
groups of many thousands which are compared by Arabian
writers to flights of locusts. The latter cases are periodical,
and the meteors are then seen in streams, moving, for the
most part, in parallel directions. Of the periodic groups,
those hitherto best known are the phsenomena of the 12th
to the 14th of November, and of the 10th of August or the
day of St. Lawrence, whose "fiery tears'' (71) were long since
recognised in England as a recurring meteorological phse-
nomenon, and are mentioned in an old Church Calendar, as
well as in legendary traditions. Although a mixed shower
of shooting stars and fire-balls had been seen on the night
of the 12th and 13th of November, in 1823, by Kloden, at
Potsdam, — and in 1832 throughout Europe, from Ports-
mouth in England, to Orenburg on the Oural river, and even
in the southern hemisphere in the Isle of Prance, — still the
idea of the periodicity of the phsenomenon, and of great
showers of falling stars being connected with particular days,
was first inferred on the occasion of the fall observed by
Olmsted and Palmer in North America on the 12th and
13th of November, 1833, when the shooting stars seemed,
in one part of the sky, to fall as thickly as snow-flakes ;
in the course of nine hours there fell at least 240000.
ATTOOTJTES. 115
Palmer recalled to recollection the fall of meteors in 1799,
at Newhaven, which was first described by Ellicott and
myself (72), and which was shown, by the obervations which
I brought together, to have extended simultaneously over the
new continent, from the Equator to New Herrnhut in Green-
land in lat. 64° 14', and from 46° to 82° of west longitude
from Paris. The identity of the two epochs was perceived with
astonishment. The stream which was seen over the whole
sky, on the 12th and 13th of November, 1833, from Jamaica
to Boston, recurred on the nights of the 13th and 14th of
November, 1834, in the United States, but the display
was less brilliant.
A second equally regular periodic shower, that of the
Feast of St. Lawrence, takes place between the 9th and 14th
of August. Muschenbrock (73) had called attention, in the
middle of the last century, to the frequency of meteors in
the month of August ; but their regular return about the
epoch of St. Lawrence's Day was first made out by Quetelet,
Gibers, and Benzenberg. No doubt other periodically re-
curring showers (74) will in time be discovered, possibly
about the 22nd and 25th of April, the 6th and 12th of
December, and — judging from the falls of aerolites recounted
by Capocchi— perhaps also from the 27th to the 29th of
November, or on the 17th of July.
Independent as all the occurrences of this kind have
hitherto seemed of local circumstances, such as latitude,
temperature, and climatic relations, there is an accompanying
phsenomenon of which it would be wrong to omit the notice,
although the coincidence may, perhaps, have been purely
accidental. The Aurora Borealis showed itself with great
intensity during the occurrence of the most magnificent dis-
116 CELESTIAL PH^ENOMEN A .
play of meteors yet observed, viz., that described by Olmsted,
on the 12th and 13th of November, 1833. The Aurora
was also seen during the periodical phenomenon in 1838, at
Bremen, where, however, the fall of meteors was much less
striking than at Richmond, near London. I have noticed
elsewhere the remarkable observation of Admiral Wrangel(75),
which he has repeatedly confirmed to me verbally, viz., that
during the appearance of the Aurora on the Siberian coast
of the Polar Sea, he frequently saw portions of the sky
not previously luminous which seemed to kindle when a
falling star shot across them, and continued bright for some
time afterwards.
It is probable that the different streams or meteors, each
consisting of myriads of small cosmical bodies, intersect the
orbit of the Earth in the same way that Biela's comet does.
According to this view, we may imagine that they form a con-
tinuous ring, each pursuing its course in a common direction.
The small planets between Mars and Jupiter present, with
the exception of Pallas, an analogous arrangement in their
closely connected orbits. We cannot yet determine whether the
variations in the epochs at which the stream becomes visible
to us, and the retardations of the phsenomena, to which I long
ago called attention, indicate a regular progression or an
oscillation of the nodes (i. e.y the points of intersection of
the ring with the Earth's orbit) ; or whether they are to be
explained by the irregular grouping and very unequal
distances apart of these very small bodies ; and by
the supposition that the zone formed by them has a width
which the Earth requires several days to traverse.
The system of the satellites of Saturn shows us a group
of intimately connected cosmical bodies, occupying a zone
AEROLITES. 117
of prodigious breadth. In this group the orbit of the
outermost, that is the seventh, satellite, has a diameter so
considerable, that the earth, in her course round the sun,
requires three days to pass through an equal space. If in
one of the continuous rings, which we have imagined as formed
by the paths of the periodical streams, we suppose the dis-
tribution of the asteroids to be such that there are only a few
groups so closely congregated as to occasion the appearance
of showers, we may conceive how such brilliant phenomena
as those of November 1799 and 1833 may be of exceedingly
rare occurrence. The highly ingenious Olbers was inclined
to think, that the next return of the great phsenomenon of
fire-balls and shooting stars falling like flakes of snow,
would be witnessed from the 12th to the 14th of November,
1867.
Sometimes the stream of the November asteroids has
been visible over a small portion only of the earth's surface :
for example, in the year 1837, it was seen with great mag-
nificence as a meteoric shower in England, whilst, on the
same night, which was uninterruptedly clear, a very atten-
tive and practised observer at Braunsberg, in Prussia, saw
only a few sporadic shooting stars between 7 P.M. and sun-
rise the following morning. Hence, Bessel inferred (76) that
a small group of the great ring occupied by these bodies
approached the earth in England only, while the countries
to the eastward passed through a part of the meteoric ring
which was comparatively void. Should increased proba-
bility be given to the supposition of a regular progression
of the line of nodes, or of its oscillation in consequence of
perturbations, the discovery of older observations of these
phenomena will acquire a special interest. The Chinese
118 CELESTIAL PHENOMENA.
annals, which contain notices both of the appearance of
comets, and of great showers of falling stars, go back be-
yond the time of Tyrtaeus, or of the second Messenian war :
they describe two streams occurring in the month of March,
one of which was observed 687 years before the Christian
era. Edouard Biot has remarked, that in fifty-two
appearances of numerous shooting stars recorded in the
Chinese annals, the periods which recur most frequently
are from the 20th to the 22d July, old style. This stream
may therefore be the same as that which we now observe
about St. Lawrence's day (10th of August), supposing it to
have somewhat advanced(77). If the shower of falling stars
of the 21st October, 1366, old style, of which Boguslawsld,
(the younger), has found a notice in Benessius de Horowic's
Chronicon Ecclesise Pragensis,— be our present November
phsenomenon, seen on that occasion in bright daylight, — we
should learn from the progression which has taken place in
the interval of 477 years, that the centre of gravity of this
system of shooting stars describes a retrograde path round
the sun. It also follows from the views which have been
here developed, that if years pass by in which neither of
the streams which have been hitherto indicated (that is,
those of November and August) are observed at any part of
the earth, the cause may be sought, either in interruptions
in the ring by vacant spaces or gaps between the groups of
asteroids, or, as Poisson thinks, in the influence which the
larger planets (78) may exercise on the form and position of
the ring.
The solid masses which reach the earth, — whether they
have been seen to fall at night from balls of fire, or in the day-
time from a small dark cloud usually in a clear sky, and with
AEROLITES. 119
a loud noise — though considerably heated, are not incan-
descent. They exhibit, on the whole, a general unmislakeable
resemblance to one another in their external form, in the
nature of their crust, and in the chemical composition of their
principal constituents ; and this resemblance is traceable when
and wherever they have been collected, at all periods of time,
and in all parts of the earth. But this remarkable and early
recognised similarity of general character in solid meteoric
masses, suffers many exceptions in detail. How different are
the very malleable masses of iron from Hradschina in the dis-
trict of A gram, or those from the banks of the Sisim in the
Jeniseisk government, mentioned by Pallas, or those
which I brought from Mexico (79), all of which con-
tain 96 per cent, of iron, from the aerolite of Sienna, which
hardly contains two per cent, of iron, from the earthy me-
teoric stone of Alais in the Departement du Card, which
falls to pieces when immersed in water, and from those of
Jonzac and Juvenas, which are without any metallic iron,
and are composed of various crystalline ingredients.
These diversities have led to the division of the cosmical
masses under consideration into two classes; nickelife-
rous meteoric iron, and fine or coarse-grained meteoric
stones. The crust of these masses, which is only a few
tenths of a line in thickness, is very characteristic ; it has
often a pitchy lustre (80) and is sometimes veined. The only
instance which I know of the absence of this crust is in the
meteoric stone of Chantonnay in La Vendee, which is
marked by another circumstance equally rare, viz. the presence
of pores and vesicular cavities, like the meteoric stone of Juve-
nas. The separation of the black crust from the light gray
120 CELESTIAL PHENOMENA.
mass beneath is always as sharply defined as is that of the
dark leaden-coloured crust of the white granite blocks (81)
which I brought from the cataracts of the Orinoco, and
which are also found by the side of many cataracts in other
parts of the world, as those of the Nile and the Congo.
The greatest heat of our porcelain furnaces can produce
nothing similar to the crust of the aerolites, so distinctly
and sharply separated from the unaltered mass beneath.
Appearances which might seem to indicate a softening of
the fragments have been occasionally recognised, but, in
general, the condition of the greater part of the mass, —
the absence of any flattening from the effect of the fall, — and
the moderate degree of heat perceived on touching the
newly fallen aerolite, — are far from indicating a state of in-
ternal fusion dining its rapid passage from the limits of the
atmosphere to the earth.
The chemical elements of which meteoric masses consist
have been well analysed by Berzelius, and are the same whick
we find dispersed in the crust of the earth ; they include iron,
nickel, cobalt, manganese, chrome, copper, arsenic, tin,
potash, soda, sulphur, phosphorus, and carbon; being in
all about one-third of the number of elementary substances
with which we are at present acquainted. Notwithstand-
ing the identity of their ultimate constituents with those
into which inorganic bodies are chemically decomposable,
yet the manner in which these constituents are combined
occasions the general aspect of meteoric masses to be
peculiar, and unlike terrestrial productions. The pre-
sence of native iron, found in almost all aerolites, gives
them a specific character, but one not necessarily lunar;
AEEOLITES.
for there may be other cosmical bodies besides the moon
in which water may be entirely wanting, and processes of '
oxidation may be rare.
The cosmical gelatinous vesicles, the organic masses re-
sembling the Tremella nostoc, which, since the middle ages,
have been supposed to belong to shooting stars, and the pyrites
of Sterlitamak, west of the Oural, which are supposed
to have formed the inside of hailstones (82), belong to the
fables of meteorology. The aerolites winch possess a fine-
grained texture, and are composed of olivine, augite, and
labradorite (83), are, as Gustav Kose has shewn, the only
ones which have a telluric appearance; for example, the
aerolite resembling dolorite, found at Juvenas, in the De-
partement de TArdeche. They contain, in fact, crystalline
substances quite similar to those of the crust of the earth ;
and in the Siberian mass of meteoric iron, the olivine is
only distinguished by the absence of nickel, which is there
replaced by oxide of tin (84). As meteoric olivine, like
our basalts, contains from 47 to 49 per cent, of magnesia,
and as, according to Berzelius, olivine forms one -half
of the earthy constituents in meteoric stones, there is no
reason to be surprised at the large proportion of silicate of
magnesia which we find in these cosmical masses. Since
the aerolite of Juvenas contains distinct crystals of augite
and labradorite, the numerical proportions of the constituents
render it at least probable, that the meteoric masses of
Chateau Eenard are examples of diorite composed of horn-
blende and albite, and that those of Blansko and Chatonnay
are combinations of hornblende and labradorite. The proof
which has been supposed to be furnished, by the minera-
logical resemblances just alluded to, of a telluric or atmo-
122 CELESTIAL PHENOMENA.
spheric origin of aerolites, do not appear (o me to have
much force. I would here refer to a remarkuble conversation
which took place between Newton and Conduit at Ken-
sington (s5), and ask, why should not the substances be-
longing to one group of cosinical bodies, or to one planetary
system, be for the most part the same ? Why should it
not be so, if we permit ourselves to surmise that the
planets, and all the spheroidal masses which revolve
around the sun, have been formed by the gradual condensa-
tion of revolving rings of gaseous matter, separated from the
once more extended solar atmosphere ? We are, it seems
to me, no more entitled to call nickel and iron, olivine and
augite, which we find in meteoric stones, exclusively terres-
trial substances, than I should be to call plants which grow
wild in Germany, and which I might also meet with beyond
the Oby, " European species of the flora of Northern Asia."
If, in a group of cosmical bodies, the elementary substances are
tiie same, why should they not form determinate compounds
in accordance with their mutual affinities and attractions, as
in the polar regions of Mars resplendent domes of snow and
ice, and in other smaller cosinical masses, mineral aggrega-
tions, containing crystals of olivine, augite, and labradorite ?
Even in the field of what must necessarily be conjecture, its
course must not be arbitrary, or irrespective of induction.
Extraordinary obscurations of the sun's disk have occa-
sionally taken place, so that stars have been seen even at
midday. A phenomenon of this nature, not to be explained
by a cloud of volcanic ashes, or by a fog of unusual elevation,
occurred in 1547, at the period of the eventful battle near
Miihlberg, and continued during three entire days. They were
attributed by Kepler, at one time to a " materia cometica, '
AEEOLITES. 123
and at another to a black cloud produced by sooty exhalations
from the solar orb. Obscurations of less duration, which took
place in 1090 and 1203, and lasted, one for three, and the
other for six hours, were ascribed by Chladni and Schnurrer
to the intervention of meteoric masses. Since the common
direction of their paths has led us to regard the streams of
shooting stars as forming a continuous ring, the epochs of
yet unexplained celestial phenomena have been brought into
remarkable connection with the regularly recurring epochs
of the meteoric displays. Adolph Erman, with much acute-
ness, and after a careful analysis of all the facts hitherto
collected, has called attention in this respect to the times of
conjunction with the sun of the August asteroids (the 7th
of February), and of the November asteroids (the 12th of
May) ; and has pointed out a remarkable coincidence
between the conjunction of the November asteroids, and :
the celebrated cold, days of the Saints Mamertus, Pan-
cratius, and Servatius (86).
The Greek natural philosophers, generally little disposed
to observation, but most persevering and inexhaustible in
conjectural interpretations of half-perceived facts, have left
on record speculations respecting shooting stars and me-
teoric stones, which greatly resemble some of the views of the
cosmical nature of these phsenomena now commonly received.
" Shooting stars," says Plutarch (8?), in the Life of Lysander,
"according to some naturalists, are not emanations from
the ethereal fire, which become extinguished in the air
immediately after being kindled ; nor are they an ignition
and combustion of air which may have been dissolved in
quantity in the upper region; they are rather celestial
bodies which fall in consequence of an interruption of the
121 CELESTIAL PHENOMENA.
general force of rotation, and are precipitated not only upon
inhabited countries, but also beyond them in the ocean, so
that they are not found/' Diogenes of Apollonia (88) ex-
presses himself still more clearly. According to him,
" together with the visible stars there move other in-
visible ones, which are therefore without names. These
not unfrequently fall to the earth and become extinguished,
like the star of stone which fell in flames at ^Egos Potamos/'
The Apollonian, who regarded all other stars (i. e. the
luminous ones) as pumice-like bodies, probably founded his
opinion respecting shooting stars and meteoric stones on
the doctrine of Anaxagoras of Clazomene, who imagined all
celestial bodies to be mineral masses which the fiery ether
in its impetuous course had torn from the earth, inflamed,
and converted into stars. The Ionic school, therefore,
with Diogenes of Apollonia, placed aerolites, and stars or
heavenly bodies, in one and the same class : both, indeed,
were alike regarded as of telluric origin, but this was in the
view of all having been once formed from the earth, and
having taken their places round her as a central body (89) ;
precisely as, according to modern ideas, the planets of a
system are conceived to have been formed around the cen-
tral body or sun, and from its once extended atmosphere. This
view is not, therefore, to be confounded with that usually
implied in what is called the telluric or atmospheric origin
of meteoric stones; or with the extraordinary notion of
Aristotle, who supposed the enormous mass of JEigos Pota-
mos to have been carried up by a tempestuous wind.
A presumptuous scepticism, which rejects facts without
examination of their truth, is in some respects even more
injurious than an unquestioning credulity; it is the tendency
AEROLITES.
of both to impede accurate investigation. Although for
upwards of two thousand years the annals of different na-
tions had told of falls of stones, and in many instances such
falls had been placed beyond doubt by the testimony of irre-
proachable witnesses ; although the Bsetylia formed an
important part of the meteor worship of the ancients, and
the companions of Cortes saw at Cholula the aerolite which
had fallen on the neighbouring pyramid ; although Caliphs
and Mongolian princes had had swords forged of fresh-fallen
meteoric stones ; and even although human beings had been
killed by stones in their descent (a friar at Crema, in
1511; a monk at Milan, 1650; and two Swedish sailors
on board a ship in 1674) ; yet until the time of Chladni,
who had already earned an imperishable renown in physics
by the discovery of the quiescent lines shown by his figure
representations of sound, this great cosrnical pheenomenon
remained almost unheeded, and its intimate connection with
the rest of the planetary system unknown. Those who are
persuaded of this connection, if susceptible of emotions of
awe from the impressions of nature, will be strongly moved
to thoughtful contemplation, not only by the spectacle of
the brilliant phenomenon of meteoric showers at the August
or November periods, but also whenever they behold
& solitary falling star shoot across the sky. The pro-
found repose of night is suddenly interrupted, and life
and motion momentarily break the tranquil splendour
of the firmament. The spectator sees in the glimmering
light which marks the track of the falling star the
visible delineation of a portion of its orbit ; and the
burning asteroid brings to his mind the existence of matter
pervading universal space. When we compare the volume
126 CELESTIAL PHENOMENA.
of the innermost of Saturn's satellites, or of Ceres, with the
enormous volume of the Sun, the relations of great and
small disappear to our imagination. The sudden blazing
up and subsequent extinction of stars in Cassiopea, Cygnus,
and Ophiucus, have already led to the admission of the
possible existence of non-luminous cosmical bodies. Con-
densed in smaller masses, the asteroids revolve around
the sun, intersect like comets the paths of the great
luminous planets, and become ignited when they enter or
when they approach the outermost strata of our atmosphere.
Our intercourse with all other cosmical bodies — with all
nature beyond the limits of our own atmosphere — is, exclu-
sively, either through the medium of light, and of radiant
heat intimately united with light (90), or through the
mysterious force of attraction exerted by remote bodies, ac-
cording to the measure of their distance and their mass, on
our globe, its ocean, and its atmosphere. But if in shooting
stars and meteoric stones we recognise planetary asteroids,
we are enabled by their fall to enter into a wholly different,
and more properly material, relationship with cosmical objects.
Here we no longer consider bodies acting upon us exclu-
sively from a distance, by exciting undulatory vibrations of
light or heat, or by causing, or themselves undergoing, mo-
tion by the influence of gravitation ; but we have actually
present the material particles themselves, which have
come to us from the regions of space, have descended
through our atmosphere, and remain upon the earth. A
meteoric stone affords us the only possible contact with a
substance foreign to our planet Accustomed to know non-
telluric bodies solely by measurement, by calculation, and
by the inferences of our reason, it is with a kind of asto-
ZODIACAL LIGHT. 127
nishment that we touch,, weigh, and analyse a substance
appertaining to the world without : the imagination is sti-
mulated, and the intellect aroused and animated by a spec-
tacle, in which the uncultivated mind sees only a train of
fading sparks in the clear sky, and apprehends in the black
stone which falls from the thundering cloud only the rude
product of some wild force of nature.
If the asteroids, on the description of which I have lin-
gered with pleasure, may seeni in some degree to resemble
comets by the smallness of their mass and the variety of their
paths, they differ essentially from those bodies in being visible
to us only at the instant of their destruction, or when,
arrested by the earth, they become luminous by ignition.
To complete our view of all that belongs to the
solar system, which since the discovery of the small
planets, of the comets of short period, and of the meteoric
asteroids, appears so complex and so rich in forms, we
have yet to consider the Zodiacal Light, to which
allusion has already been made. Those who have dwelt
long in the zone of Palms, must retain a pleasing re-
membrance of the mild radiance of this phsenomenon,
which rising pyramidally, illumines a portion of the un-
varying length of the tropical nights. I have seen it
occasionally shine with a brightness greater than that of the
Milky Way near the constellation of Sagittarius ; and this
not only in the dry and highly rarefied atmosphere of the
summits of the Andes, at elevations of thirteen to fifteen
thousand feet, but also in the boundless grassy plains or
llanos of Venezuela, and on the sea-coast under the ever
clear sky of Cumana. The phenomenon is one of peculiar
VOL. i. L
128 CELESTIAL PHENOMENA.
beauty when a small fleecy cloud is projected against the
Zodiacal light, and detaches itself picturesquely from the
illuminated back-ground. A passage in my journal during
a voyage from Lima to the West Coast of Mexico, notices
such a picture. "For the last three or four nights (be-
tween 10° and 14° of North latitude), the Zodiacal light
has appeared with a magnificence which I have never before
seen. Judging also from the brightness of the stars
and nebulae, the transparency of the atmosphere in this
part of the Pacific must oe extremely great. Prom
the 14th to the 19th of March, during a very regular in-
terval of three-quarters of an hour after the disk of the sun
had sunk below the horizon, no trace of the Zodiacal light
could be seen, although the night was perfectly dark ; but
an hour after sunset it became suddenly visible, extending
in great brightness and beauty between Aldebaran and the
Pleiades, and, on the 18th of March, attaining an altitude
of 39° 5'. Long narrow clouds, scattered over the lovely
azure of the sky, appeared low down in the horizon, as if in
front of a golden curtain, while bright varied tints played
from time to time on the higher clouds : it seemed a second
sunset. Towards that side of the heavens the diffused light
appeared almost to equal that of the moon in her first
quarter. Towards ten o'clock, in this part of the Pacific,
the Zodiacal light usually becomes very faint, and at mid-
night I could see only a trace of it remaining. On the
16th of March, when its brightness was greatest, a mild
reflected glow was visible in the east." In the obscurer
sky and thicker atmosphere of our so-called temperate zone,
the Zodiacal light is only distinctly visible in the beginning
of spring, when it may be seen after evening twilight above
ZODIACAL LIGHT. 129
the western horizon, and at the end of autumn, before the
commencement of morning twilight, above the eastern
horizon.
It is difficult to understand how so striking a natural
phenomenon could have failed to attract the attention of
astronomers and physical philosophers before the middle of
the seventeenth century, or how it should have escaped the
observant Arabs in ancient Bactria, on the Euphrates, and
in Southern Spain. We are almost equally surprised at the
late period at which the nebulse in Andromeda and Orion,
first described by Simon Marius and Huygens, were ob-
served. The earliest distinct description of the Zodiacal
light is contained in Childrey's Britannia Baconica(91), of the
year 1661 ; its first observation may have been two or three
years earlier. Dominic Cassini has, however, incontestably
the merit of having been the first (in 1683) who investi-
gated its relations in space. The luminous appearance
which was seen by him in 1668 at Bologna, and at the same
time in Persia by the celebrated traveller Chardin (and
which the Court astrologers of Ispahan, who had never seen
it before, named " nyzek" or " small lance"), was not,
as has often been said, the Zodiacal light, but the enormous
tail of a comet (92), the head of which was concealed by its
proximity to the horizon, and which, in its position and
appearance, presented many points of resemblance to the
great comet of 1843. But it may be conjectured with
much probability, that the remarkable light rising pyrami-
dally from the earth, which, in 1509, was seen in the
eastern part of the sky for forty nights in succession from
the high table land of Mexico (and which I found men-
tioned in an ancient Aztec manuscript, in the Codex
130 CELESTIAL PH/ENOMENA.
Telleriano-Remensis (93), in the Royal Library at Paris) , was
the Zodiacal light.
TMs phenomenon, doubtless of primeval antiquity, but
first discovered in Europe by Childrey and Dominic
Cassini, is not the luminous atmosphere of the sun
itself, which, according to the laws of mechanics, cannot be
more oblate than in the ratio of 2 : 3, and could not there-
fore extend to a greater distance than nine-twentieths of the
distance of Mercury from the Sun. The same laws deter-
mine that the height of the extreme limit of the atmosphere
of a rotating cosmical body above its equator, or the point
at which gravity and the centrifugal force are in equili-
brium, can only be that at which a satellite would complete
its revolution in the same time that the central body rotates
around its own axis (94). This restricted limit of the
solar atmosphere, in its present concentrated condition,
is particularly striking when we compare the central
body of our system with the nucleus of other nebulous
stars. Herschel discovered several in which the semi-
diameter of the nebula surrounding the star subtends an
angle of 150". Assuming a parallax of not" quite one
second, we find the outermost nebulous stratum of such
a star to be 150 times farther from its center than the dis-
tance of the Earth from the Sun. If, therefore, such a
nebulous star was in the place of our Sun, its atmosphere
would not only include the orbit of Uranus, but would ex-
tend eight times as far (95).
The solar atmosphere being thus limited in extent, we
may with great probability attribute the Zodiacal light to
the existence of an extremely oblate ring (96) of nebulous mat-
ter, revolving freely in space between the orbits of Venus
ZODIACAL LIGHT. 131
and Mars. We can, indeed, at present, form no certain
judgment concerning the true dimensions of the supposed
ring ; its possible augmentation (97) by emanations from the
tails of many millions of comets when at their perihelia ; the
singular variability of its extension (which seems sometimes
not to exceed that of our own orbit) ; or concerning its not
improbable intimate connection with the more condensed
cosmical vapour in the vicinity of the Sun. The nebulous
particles of which the ring consists, and which revolve
around the Sun according to the same laws as the planets,
may either be self-luminous, or may reflect the light of the
Sun. The first supposition is not inadmissible; even a
terrestrial fog (and it is a very remarkable fact), shewed
itself in 1743, at the time of the new moon and in the
middle of the night, so phosphorescent, that objects could
be distinctly recognised at a distance of above 600 feet(98).
In the tropical regions of South America, I have some-
times observed with astonishment the variations in in-
tensity of the Zodiacal light. Having passed the nights
during several months in the open air and under a
serene sky, on the banks of the great rivers or in the midst
of the wide grassy plains or llanos, I had frequent oppor-
tunities of carefully observing the phenomenon. Some-
times in a few minutes after the Zodiacal light had been at
the strongest, it would become sensibly weakened, then
suddenly reappear in full brilliancy. In a few instances I
thought that I perceived,— not indeed a tinge of red colour,
or a dark arch beneath, or, as Mairan describes, a jet
of sparks, — but an undulatory motion of the light. Are
there, then, processes going on in the nebulous ring
itself? or is it not more probable that, — though near the
CELESTIAL PHJENOMENA
ground, and in the lower part of the atmosphere, I could
detect no changes of temperature or moisture by the me-
teorological instruments, — and even though small stars of
the fifth and sixth magnitude appeared still to shine with
undiminished and equable light, — condensations were tak-
ing place in the higher regions of the atmosphere, which
modified the transparency of the air, or rather its reflecting
power,*in some peculiar and to us unknown manner ? The as-
sumption of such meteorological processes near the limits
of our atmosphere is favoured by observations made by
the acute Olbers ("), "of sudden flashings and pulsations
which, in the course of a few seconds, vibrate throughout
the whole of a comet's tail, which is seen at the same time
to lengthen several degrees, and again to contract. As the
different portions of a comet's tail, which is millions of
miles in length, are at very unequal distances from the
Earth, it is not possible, according to the laws of the velocity
and propagaiton of light, that actual alterations in a cosmical
body filling so immense a space, should be seen by us to
take place in such short intervals of time." These considera-
tions by no means exclude the reality of variable emana-
tions around the denser envelopes of the nucleus of a comet,
or of sudden brightenings of the Zodiacal light from internal
molecular movements, or of changes due to variations in
the light reflected by the nebulous matter of which the ring
is composed ; but they should make us careful to distin-
guish between effects which should be referred to the cos-
mical ether and to the regions of space, and those which are
referrible to the terrestrial atmospheric strata through which
the bodies existing in space are beheld by us. There are
well observed facts, which shew us that we are not able to
ZODIACAL LIGHT. 133
explain completely all that takes place at the uncertain and
much contested limit of our atmosphere. The wonderful
lightness of whole nights in the year 1831, in which, in the
latitudes of Italy and Northern Germany, small print could
be read at midnight, appears in manifest contradiction to all
that we learn (10°) from the most recent and exact researches
on the theory of twilight, and on the height of the atmo-
sphere. The phenomena of light which astonish us in the
variability of the crepuscular limits, and in the changes in
the Zodiacal light, must be dependent on conditions which
have not yet been successfully investigated.
Thus far we have been occupied in considering the
world of forms governed by our Sun, or the solar
system ; comprising planets, satellites, comets of shorter or
longer periods of revolution, meteoric asteroids moving either
sporadically, or in crowded streams in continuous rings,
and, finally, a luminous nebulous ring, revolving round the
sun near the orbit of the earth, and for which, from its
position, the name of Zodiacal light may be retained, In
the movements of all, the law of periodic return everywhere
prevails, however different may be the measure of velocity,
or the quantity of the aggregated particles : the asteroids
alone, as they enter our atmosphere from the regions of
space, have their planetary revolution checked, and are them-
selves united to the larger planet. In that immense system,
of which the limits are determined by the force of attraction
of the central body, comets return in their elliptic orbits
from distances equal to forty-four elongations of Uranus ;—
nay, in those very comets in which the nucleus, from the
smallness of its mass, appears to us but as a cosmic cloud,
it yet retains by its attraction the most remote particles
134 CELESTIAL PHENOMENA.
of the tail, which streams from it to a distance of many
millions of miles. Thus the central forces are the main*
taining as well as the constituent forces of the system .
Our Sun, viewed in relation to all the bodies so various
in magnitude and density which revolve around it, may be
regarded as at rest, although it revolves around the common
center of gravity of the whole system, which center, in conse-
quence of the varying position of the planets, falls sometimes
within and sometimes without the body of the Sun itself. Alto-
gether distinct in its nature is the movement of translation of
the Sun, — the progressive motion of the center of gravity of
the whole solar system in universal space, — which is supposed
to take place with such prodigious velocity, that, according
to Bessel(101), the relative motion of the Sun and the star
61 Cygni amounts, in a single day, to no less than 3336000
. miles. "We should be unconscious of the change of place
of the solar system, were it not that, by the perfection of
our astronomical instruments, and by improved methods
of observation, we are enabled to note our progress by refe-
rence to distant stars, — as in a vessel we estimate its speed
by the apparent motion of objects on shore. The proper
motion of 61 Cygiri is, nevertheless, so considerable, as to
produce a displacement of a whole degree in 700 years.
We can measure the amount of changes in the relative
positions of the stars to one another, — in their proper
motions as these changes are called, — with far greater
certainty than we can explain their cause. After de-
ducting all that depends on the precession of the equi-
, noxes, and the nutation of the Earth's axis consequent
upon the influence of the Sun and Moon on the sphe-
roidal form of the earth, -all that results from the
PliOPEE MOTIONS OF STAES. 135
propagation and aberration of light, or from the parallax
produced by the opposite positions of the Earth in
its orbit round the Sun, — we find a residual annual
motion of the fixed stars, which includes both the trans-
lation of the whole solar system in space, and the actual
proper motions of the stars themselves. The very
difficult numerical separation of these two elements has
been rendered possible, by a careful specification of the
directions in which the movements of the different stars
take place, and by the consideration that, if they were all
absolutely at rest, they would appear perspectively.to recede
from the point towards which the Sun's course is di-
rected. The result of the investigation, confirmed by the
theory of probabilities, is, that both our solar system and
the stars are changing their place in space. It appears
from the admirable investigations of Argelander (102), (who
has been engaged at Abo in extending, and in carrying to
much greater perfection, the work commenced by William
Herschel and Prevost,) that the Sun is moving towards the
constellation of Hercules, and very probably towards a
point which, from a combination of the observations of
537 stars, was situated (equinox of 1792'5) in 257° 49''7
Eight Ascension, and in 28° 49'7 North Declination. In
this delicate investigation there is still great difficulty in
separating the absolute from the relative motion, and in
determining what portion belongs to the solar system only.
If we consider the proper motions of stars, as contra-
distinguished from their apparent or perspective motions,
their directions are various and even opposite in different
groups ; it is not, therefore, a necessary conclusion, either
lat all parts of our astral system, or that all the systems
rhich fill universal space, revolve around one great undis-
136 CELESTIAL PHENOMENA.
covered luminous or non-luminous central body, however
naturally we may be disposed to an inference which would
gratify alike the imaginative faculty, and that intellectual
activity which ever seeks after the last and highest generalisa-
tion. Even the Stagirite has said, " All that moves leads
us back to the cause of the motion which we perceive ; and
it would be but an endless derivation of causes, were there
not a primary mover itself at rest(103)."
Amongst the manifold changes of place of stars in groups,
not occasioned by parallax depending on the place of
the observer, but actual changes taking place progressively
and uninterruptedly in space, we have revealed to us in
the most incontestable manner by one phenomenon, — the
orbital movements of double stars, and their variable
motion in different parts of their elliptical orbits, — the
dominion of the laws of gravitation, extending far beyond
the limits of our solar system, even to the remotest regions
of creation. On this subject man's desire of knowledge need
no longer rest on vague conjecture, or seek satisfaction in
the boundless but uncertain field of analogy, for here also
the progress of astronomical observation* and calculation has
at length placed us on firm ground. It is not so much the
astonishing number already discovered of double or multiple
etars revolving round a common center of gravity
(a number which, in 1837, amounted to 2800), as it
is the extension of our knowledge of the fundamental forces
of the whole material world, — and the evidence thus afforded
of the universal prevalence of the law of gravitation, —
which excites our admiration, and constitutes one of the
most brilliant discoveries of our epoch. The time of
revolution of differently -coloured double stars varies ex-
ceedingly in different instances, from 43 years in 77 Coronse,
DOUBLE AND MULTIPLE STARS. 137
to many thousands of years in 66 Ceti, 38 Geminorum, and
100 Piscium. In the triple system of £ Cancri, the nearest
companion of the principal star has already more than accom-
plished one entire revolution since HerscheFs measurement in
1782. By means of skilful combinations of the changes of
distance and of angles of position (104), the elements of the
orbits have been assigned, and conclusions have even been
drawn respecting the absolute distance of the double stars
from the earth, and their mass as compared with the mass
of the Sun. But whether the attracting forces depend solely
on the quantity of matter in these systems as in ours, or
whether there may not coexist with gravitation other specific
forces which do not act according to mass, is, as Bessel has
been the first to shew, a question of which the solution is
reserved for later ages(105).
If we desire to compare our Sun with others of the
fixed stars or self-luminous suns, within the lenticular side-
real stratum to which we belong, we find that in the case of
some of them at least, there are methods by which we may
arrive approximately, and within certain limits, at a know-
ledge of their distance, their volume, their mass, and the
velocity of their motions in space. If we take the
distance of Uranus from the Sun at 19 times the solar dis-
tance of the Earth, then the central body of our system is
11900 such spaces, or solar distances of Uranus, from
a Centauri, 31300 from 61 Cygni, and 41600 from a Lyra.
The comparison of the volume of the Sun with the volume
of stars of the first magnitude is dependent on an optical
element which is subject to extreme uncertainty, viz. the
apparent diameter of the fixed stars. If, with Herschel, we
assume the apparent diameter of Arcturus even at only the
CELESTIAL PHENOMENA.
tenth part of a second, it will result that the true diamet^
of the star is eleven times greater than that of the Sun(106).
The distance of the double star, 61 Cygni, determined by
Bessel,has led to an approximate knowledge of the quantity of
matter contained in it. Although the portion of the apparent
path passed through by the smaller star since Bradley' s obser-
vations is not yet sufficiently large to enable us to infer the
true path, and its major semi-axis, yet the great Konigsberg
astronomer (107) considers it probable that " the mass of this
double star is neither much more nor much less than half
the mass of our Sun." This result is from actual measure-
ment. Analogies derived from the greater mass of those
planets of our solar system which are attended by satellites,
and from the fact that Struve has observed the proportion
of double stars to be six times greater among the brighter
than among the telescopic stars, have led other astronomers to
conjecture (108), that the average mass of the greater number
of double stars exceeds the mass of the Sun. On this sub-
ject, however, general results are far from being yet attainable.
In respect to proper motion in space, our Sun belongs,
according to Argelander, to the class of rapidly moving stars.
The aspect of the sidereal heavens, the relative position of
stars and nebulae, the distribution of the masses of light
formed by them, the picturesque beauty, if I may use the
expression, of the whole firmament, depend, in the course
of thousands of years, conjointly on the actual proper mo-
tion in space of stars and nebulse, on the movement of
translation of our solar system, on the appearance of new
stars, and the extinction or diminution in intensity of the
light of others ; and lastly and especially, on the changes
which the Earth's axis undergoes from the attraction of the
VARIABLE ASPECT OF THE HEAVENS. 139
Sun and Moon. The beautiful stars of the Centaur and of
the Southern Cross, will at some future day be visible in
our northern latitudes, whilst other stars (Sirius and the
stars forming the belt of Orion) will no longer appear
above the horizon. The place of the North Pole will be
successively marked by /3 and a Cephei, and 5 Cygni, until
after the lapse of 12000 years, when a Lyra will become
the brightest of all possible pole stars. These statements
serve in some degree to realise in the mind the magnitude
of the movements, which proceed uninterruptedly in infi-
nitely small divisions of time in the great Chronometer of
the Universe. If, for a moment, we imagine the acuteness
of our senses preternaturally heightened to the extreme limits
of telescopic vision, and bring together events separated by
wide intervals of time, the apparent repose which reigns in
space will suddenly vanish ; countless stars will be seen
moving in groups in various directions ; nebulae wan-
dering, condensing, and dissolving like cosmical clouds ;
the milky way breaking up in parts, and its veil rent
asunder. In every point of the celestial vault we
should recognise the dominion of progressive movement,
as on the surface of the earth where vegetation is con-
stantly putting forth its leaves and buds, and unfolding
its blossoms. The celebrated Spanish botanist. Cavanilles,
first conceived the possibility of " seeing grass grow," by
placing the horizontal micrometer wire of a telescope with a
high magnifying power at one time on the point of a
bamboo shoot, and at another on the rapidly unfolding
flowering stem of an American aloe ; precisely as the astro-
nomer places the cross of wires on a culminating star.
Throughout the whole life of physical nature — in the organic
140 CELESTIAL PHENOMENA.
as in the sidereal world — existence* preservation, produc-
tion, and development, are alike associated with motion as
their essential condition.
The breaking up of the Milky Way, to which I have
alluded, requires a more particular notice. William
Herschel, our safe and admirable guide in the regions
of space, has found by his star-gaugings, that the tele-
scopic breadth of the Milky Way is six or seven degrees
wider than is laid down in our celestial maps, or than it
appears to the naked eye (109) . The two bright nodes in which
the two branches of the zone unite, near the constellations
of Cepheus and Cassiopea, and those of Scorpio and Sagit-
tarius, appear to exercise a powerful attraction on the
neighbouring stars ; but in the brightest portion, between
ft and 7 Cygni, 330000 stars are found in a breadth of 5°,
of which half appear to be attracted towards one side, and
half towards the other. It is here that Herschel surmises
that a disruption may take place (110).
The number of distinguishable telescopic stars in the
Milky Way, apart from nebula, is estimated at eighteen
millions. In order, I will not say to realise the magnitude
of this number, but to compare it with something analogous,
I would recal to the reader, that the whole number of stars
in the firmament from the first to the sixth magnitude,
visible to the naked eye, is only about 8000. In the unpro-
ductive astonishment which is excited by the relation of
mere numerical values, unconnected with applications
affecting the higher powers of the intellect, the imagination,
or the feelings, the extremes in point of dimension meet; —
namely, the cosmical bodies of the vast regions of space,
and the smallest forms of animal existence. A cubic inch of
NEBULOUS MILKY WAY. 141
the polishing slate of Bilin contains, according to Ehren-
berg, 40000 millions of the siliceous shells of Galionellee.
Nearly at right angles to the Milky Way formed of stars,
in which, as Argelander remarks, brilliant stars are more
numerous than in any other part of the heavens, there is
another milky way consisting of nebulse. The first of these,
or the galaxy of stars, according to Sir John Herschel's
views, forms around our sidereal system, and at some dis-
tance from it, a detached ring or zone, similar to the ring
of Saturn. The situation of our planetary system is
eccentric, nearer to the region of the Cross than to the
opposite region, that of Cassiopea(ul). In a nebula
discovered by Messier, but which has been only imper-
fectly seen, we seem to discover the image of our own
sidereal system, and the divided ring of our Milky Way
reflected, as it were, with wonderful similarity (112). The
galaxy of nebulse does not belong to our sidereal zone, but
surrounds it at a vast distance, and without any physical
connection, passing almost in a great circle through the
nebulse in Virgo (which are particularly numerous in the
northern wing), through the Coma Berenicis, the Ursa
Major, the girdle of Andromeda, and the Northern Fish.
It probably intersects the galaxy of stars in Cassiopea, and
connects the poles, which are situated where the thickness
of the stratum is least, and which are poor in stars, owing
possibly to the action of those forces which have formed the
stars into groups (113).
It follows from these considerations, that our sidereal
cluster — which, in its projecting branches, shews traces of
great progressive changes of form— is surrounded by two
rings, one of which, the Nebulous Milky Way, is very
142 CELESTIAL PHENOMENA.
remote; while the other, composed of stars alone, is
less distant. The latter ring, or that to which we
usually apply the term "Milky Way," consists of stars
averaging from the 10th to the llth degree, but ap-
pearing, when viewed singly, very various in point of
magnitude; whereas detached clusters, or groups of stars,
almost always shew throughout great similarity in mag-
nitude and brilliancy (m).
In whatever quarter the celestial vault has been exa-
mined with powerful space-penetrating telescopes, either
stars, though it may be only telescopic ones from the
twentieth to the twenty-fourth degree of magnitude, or
nebulae, are seen. It is probable that, with still more
powerful optical instruments, many of the nebulse would be
found resolvable into stars. The sensation of light, impressed
on the retina by single isolated points, is less, as Arago has
recently shewn, than when the rays proceed from several
points extremely near to each other (116). It is probable that
the production of heat by the condensation of the cosmical
nebulous matter, whether existing in definite forms, or
simply in its general state of distribution, may modify the
equable intensity of light, which, according to Hallcy and
Olbers, should arise from every point in the heavens being
occupied by an infinite series of stars (116). Observation,
however, contradicts the hypothesis of uniform distribution,
shewing us instead, extensive regions wholly devoid of stars
— '• openings in the heavens," as William Herschel calls
them — one four degrees in width in Scorpio, and another in
Ophiucus. We find near the margin of both these open-
ings resolvable nebulse, of which the one on the western
edge of the opening in Scorpio is amongst the richest and
SUCCESSIVE PROPAGATION OF LIGHT. 143
most crowded groups of small stars with which the heavens
are adorned. Herschel, indeed, ascribes to the attractive
force of these marginal groups (117), the starless open-
ings themselves ; of which he says, in his finely ani-
mated style, " they are parts of our sidereal stratum
which have already suffered great devastation from time."
If we consider the telescopic stars, situated one behind
another, as forming a canopy of stars covering the
whole apparent celestial vault, we may, I think, regard the
starless portions of Scorpio and Ophiucus as tubes through
which we look into the remote regions of space. The strata
which form the canopy are there interrupted ; other still
remoter stars may indeed lie beyond, but our instruments
cannot reach them. The ancients had also been led, by the
apparition of igneous meteors, to the idea of rents or chasms
in the canopy of the skies ; but the chasms were supposed
to be only transitory, and, instead of being dark, to be
bright and fiery, from affording a glimpse of the burning
ether beyond (118) . Derham, and even Huygens, appeared not
indisposed to explain, in a somewhat similar manner, the
tranquil light of the nebulse (119).
When we compare the stars of the first magnitude,
which on an average are certainly the nearest to
us, with the non-nebulous telescopic stars, — and the ne-
bulous stars with unresolvable nebulse (for example, with
the nebula in Andromeda, or even with the so-called
planetary nebulse), — and when we thus enter on the consi-
deration of distances so diverse in the boundless regions
of space,— there presses itself on our notice a fact, which
governs the relation of the phenomena as perceived by us,
to the realities which are their actual basis, viz. the sttcces-
sive propagation of light. The velocity of this propagation,
VOT.. T M
144 CELESTIAL PHENOMENA.
according to Struve's most recent investigations, is 166072
geographical miles in a second — a velocity almost a million
times greater than that of sound. From all that we learn
from the measurements of Maclear, Bessel, and Struve
of the parallaxes and distances of three fixed stars of
very different magnitudes, a Centauri, 61 Cygni, and
a Lyrse, a ray of light from each of these three bodies
requires respectively 3, 9J, and 12 years, to reach the
Earth. In the short but memorable period between 1572
and 1604, from the time of Cornelius Gemma and Tycho
Brahe to that of Kepler, three new stars suddenly appeared
in the constellations of Cassiopea, Cygnus, and in the foot
of Ophiucus. A similar phenomenon shewed itself in
the constellation of Vulpis, in 1670, but in this case
the light of the new star was intermitting. In very
modern times, Sir John Herschel, at the Cape of Good
Hope, saw the star r) Argus increase in brightness from the
second to the first magnitude (12°) . But such events or occur-
rences in the vast regions of cosmical space belong, in their
historic reality, to other epochs than those at which the
i phenomena of light first reveal them to the inhabitants of
the Earth ; they reach us as voices of the past. It has
been justly said, that with our large telescopes we penetrate
at once into space and time. We measure space by
time; the ray of light requires one hour to travel 592
millions of miles. Whilst in the Hesiodic Theogony, the
dimensions of the universe were expressed by the fall of
bodies, and the iron anvil was only nine days and nine nights
in falling from heaven to earth, it was thought by the elder
Herschel (121), that the light of the most distant nebula? disco-
I vered by his forty-foot refrnctor requires two millions of
years to reach our eyes. Thus, much may have
SUCCESSIVE PROPAGATION OF LIGHT. 145
peared even before it became visible to our eyes, and in
much the arrangement and order may have varied. The
spectacle of the starry heavens presents to our view objects
not contemporaneous ; and however much we may diminish
both the supposed distance whence the faint light of the
nebulae, or the barely discernible glimmer of the remotest
cluster of stars, reaches us, — and the thousands of years which
serve as the measure of that distance, — it will still remain
true that, according to the knowledge which we possess of
the velocity of light, it is more than probable that the light
of the most distant cosmical bodies offers us the oldest
sensible evidence of the existence of matter. Thus, resting
on simple premises, the reflecting mind rises to graver and
loftier views of nature's forms, in those boundless fields
which light traverses, and where " myriads of worlds spring j
like grass in the night/' (122)
We will now descend from the region of celestial forms to
the more restricted sphere of terrestrial forces; from the
children of Uranus to those of Gea. A mysterious bond
unites the two classes of phenomena. In the ancient sym-
bolical meaning of the Titanic mythus, (123) the forces
of the universe, and the systematic order of nature, depend
on the union of the heavens and the earth. If our
terrestrial spheroid, as well as each of the other planets,
belongs originally to the Sun, as having been formed from
detached nebulous rings of the solar atmosphere, a con-
nection is still maintained, by means of light and radiant
heat, both with the Sun of our own system, and with all
those remoter suns which glitter in the firmament. The
verv different measure of these effects must not prevent the
] 16 ==^TERRESTRIAL PHENOMENA.
physical philosopher, engaged in tracing a general picture of
nature, from noticing the connection and co-extensive domi-
nion of similar forces. A minute fraction of the Earth's
heat belongs to the part of space through which our pla-
netary system is moving, the temperature of which is
supposed to be nearly equal to the mean temperature of the
poles of the Earth, and is regarded by Fourier as the product
of calorific radiation from all the bodies of the universe.
Par more powerful undoubtedly are the effects of the Sun's
rays on the atmosphere and on the upper strata of our
globe, in the electric and magnetic currents occasioned by
his heat-producing powers ; and in the magical and beneficent
influence which awakens and nourishes the germs of life in
the organic forms on the surface of the Earth, which will
be considered in a subsequent part of the volume.
In now turning our attention exclusively to the telluric
sphere of nature, we will first consider the relative extent of
liquid and solid surface of the Earth ; its figure ; its mean
density, and the partial distribution of this density in the in-
terior of the planet; its temperature, and electro-magnetic
tension. These relations and forces will lead us to consider
the reaction of the interior of our globe on its exterior;
the special agency of subterranean heat, producing the
phenomena of earthquakes in districts of varying extent ;
the breaking forth of hot springs, and the more powerful
action of volcanic forces. Movements in the crust of the Earth,
sometimes sudden and in shocks, sometimes continuous and
almost imperceptible, alter in the course of centuries the
relative elevation of the land and sea, and the configuration
of the land beneath the ocean; while, at the same time,
communications are formed between the interior of the
GENERAL VIEW. 147
earth and the atmosphere, either through temporary clefts
or more permanent openings. Molten masses, issuing from
unknown depths, flow in narrow streams down the de-
clivities of mountains, sometimes with an impetuous, and
sometimes with a slow and gentle motion, until the fiery
subterranean fount is dry, and the lava solidifies under a
crust which it has itself formed. We thus see new rocks
produced under our eyes; whilst those of earlier forma-
tion are altered by the influence of heat, rarely in imme-
diate contact, more often in proximity. Even when no
disruption takes place, the crystalline particles in super-
incumbent rocks are displaced, and re-arranged in a denser
texture. The waters present formations of an entirely
different nature ; concretions of the remains of plants and
animals ; deposits of earthy, calcareous, and aluminous
matter ; aggregations of finely pulverized rocks, covered with
beds of siliceous-shelled infusoria, and with transported soil
containing the bones of animals belonging to an earlier state
of our globe. These processes of formation and stratification
going on before our eyes, in modes so different, — and the
disruption, flexure, and elevation of rocks and strata, by
mutual pressure and by the agency of volcanic forces, — lead
the thoughtful observer, by simple analogies, to compare the
present with the past, to combine actual pha3nomena, to
generalize, and to amplify in thought the extent and in-
tensity of the forces now in operation. Thus we arrive at
the domain of that geological science, long desired and
obscurely anticipated, but which, in the last half century,
has been placed on the firm basis of legitimate induction.
It has been acutely remarked, "that much as we have
gazed on the planers through large telescopes, we know less
148 TERRESTRIAL PHENOMENA.
of their exterior than of their interior." They have been
weighed and measured; thanks to the progress of astrono-
mical observation and calculation, their volumes and their
densities are known with constantly increasing numerical
exactness; but (with perhaps an exception in some degree
in the case of the Moon), a profound obscurity still veils
from us their physical properties. It is only on our own
globe that immediate proximity places us in relation with all
the elements both of the organic and the inorganic crea-
tion. The rich diversity of materials, their admixtures and
transformations, and the ever changing play of the forces
elicited, offer to the spirit of investigation appropriate and
welcome food ; and the immeasurable field of observation in
which the intellectual activity of the human mind can here
expatiate, lends to it a portion of its own elevation and
grandeur. The world of sensible phenomena reflects itself
into the depths of the world of ideas, and the rich variety of
nature gradually becomes subject to our intellectual domain.
I here touch again upon an advantage to which I.
have already repeatedly alluded, possessed by that portion of
our knowledge which is especially connected with our
terrestrial habitation. Uranography, or the description of
the heavens, from the remotely gleaming nebulous stars to
the central body of our own system, is limited to general
conceptions of volume and mass ; no vital activity is there
revealed to our senses ; it is only by means of resemblances,
and often fanciful combinations, that even conjectures have
been hazarded respecting the specific nature of the material
elements, and their presence or absence in this or that
cosmical body. The heterogeneity of matter, its chemical
diversity, the regular forms into winch its particles arrange
GENERAL VIEW. 149
themselves, whether crystalline or granular; its relations to
the deflected, or decomposed waves of light by which it is
penetrated; to radiating, and to transmitted, or polarised
heat; to the brilliant, or the not less energetic because
invisible, phenomena of electro-magnetism, — all this in-
calculable treasure of physical knowledge by which our
contemplation of the universe is enriched and exalted, we
owe to investigations concerning the surface of the planet
which we inhabit, and more to its solid than to its liquid
portion. I have already noticed how greatly this extensive
knowledge of natural objects and forces, and the measure-
less variety of objective perceptions, stimulates the cultiva-
tion and promotes the activity of the human intellect ; it is
as needless, therefore, to dwell farther on this topic, as on
that of its connection with the causes of the superiority in
material power, which particular nations derive from their
command of a portion of the elements. If, on the one
hand, I have been desirous of calling attention to the dif-
ference between the nature of our telluric knowledge, and of
that which we possess concerning the regions of space, I
wish, on the other hand, to indicate the limited extent of
the field from whence our whole knowledge of the hetero-
geneous properties of matter is derived. It is from that
which has been rather inappropriately termed the " crust"
of the earth, or the thickness of so much of the strata
nearest to the surface of our planet, as is opened to our
view either by deep natural valleys, or by the labours of
man in boring or in mining operations. These opera-
tions (124) attain a perpendicular depth below the level of
the sea of little more than two thousand feet, about one-third
of a geographical mile, or -g-gVo of the Earth's radius. The
150 TERRESTRIAL PHENOMENA.
crystalline masses erupted from active volcanoes, and for the
most part resembling the rocks at the surface of the earth,
come from absolute depths which, though they cannot be accu-.
rately determined, are assuredly sixty times greater than
any which have been reached by our artificial works. In
situations where strata of coal dip beneath the surface,
and rise again at distances determined by careful measure-
ment, we are enabled to assign numerically the depth of
the basin formed by them ; and we thus learn that such
coal measures, together with the ancient organic remains
which they contain, often reach (as in Belgium, for ex-
ample) depths exceeding five and six thousand feet (125)
below the present level of the sea ; and that the mountain
limestone, and the strata of the Devonian basin, attain a
depth fully twice as great. If we now combine these depths
beneath the surface with those mountain summits which
have hitherto been regarded as the highest portions of the
crust of the Earth, we obtain nearly 40000 English feet,
or a measure equalling about -5-^- of the Earth's radius.
This, therefore, would be the whole range in a vertical
direction of our geological researches, or of our knowledge
of superimposed rocks, — even if the general elevation of the
surface of the Earth equalled the height of the Dhawalagiri
in the Himalaya, or of the Sorata in Bolivia. All that is
situated at a greater depth beneath the level of the sea than
the deepest wells or mines, or the basins I have referred
to, — or than the bed of the sea where it has been reached
by sounding (James Ross sounded with 4600 fathoms, or
27600 feet of line, without finding bottom), — is as unknown
to us as the interior of the other planets of our solar system.
In the case of the Earth, as in that of the other planets, we
GENERAL VIEW. 151
know the mass and the mean density, and we are able to
compare the latter with the density of the materials con-
stituting the upper terrestrial strata, which alone are
accessible to us. Where the knowledge of the chemical
and mineralogical properties of substances in the interior of
the Earth fails us, we find ourselves again limited to the field
of mere conjecture, as in the case of the remotest planetary
bodies. We can determine nothing with certainty respect-
ing the depth at which the materials of which our rocks
are composed exist either in a softened though still
tenacious state, or in complete fusion, — respecting cavities
filled with elastic vapours, — the condition of fluids heated
under enormous pressure, — or the law of the increase of
density from the surface to the center of the earth.
The notice of the increase of heat with increasing depth
in the interior of our planet, and of the reaction of the in-
terior on the surface, will lead us to the consideration of the
long series of volcanic phsenoinena : these manifest them-
selves to us as earthquakes, emissions of gas, thermal
springs, mud volcanoes, and streams of lava flowing from
craters of eruption. The reaction of the internal elastic
forces shews itself also in alterations of the configuration
and of the level of the surface of the globe. Vast plains
and deeply indented continents are elevated or depressed,
and thus the reciprocal limits of land and sea, of solid and
liquid surface, are frequently and variously modified. Plains
have undergone an oscillatory motion, being alternately ele-
vated and depressed. Subsequently to the elevation of con-
tinents above the sea, mountain chains have risen from long
clefts, and these are mostly parallel, in which case the
elevations were probably cotemporaneous. Salt lakes and
152 TERRESTRIAL PHENOMENA.
great inland seas, long inhabited by the same species of ani-
mals, have been violently separated, their original connection
being still evidenced by the fossil remains of shells and
zoophytes. Thus in following phenomena in their mutual
dependence, we are conducted from the consideration of
forces operating in the interior of our globe, to movements
and disruptions of its surface, and to the pouring forth of
molten streams forced up by the expansive energy of elastic
vapours. The same forces which elevated the lofty chains
of the Andes and the Hiinalaya to the regions of perpetual
snow, have occasioned new compositions and textures in the
mineral masses, and have altered strata which had been
previously deposited from fluids containing many organic
substances. We thus perceive the dependence of the series
of formations, divided and superposed according to their
ages, on changes of configuration of the surface, on dynamic
relations of the upheaving forces, and on the chemical
action of the vapours which issue from the fissures.
The form and distribution of the dry laud, or of tha,t
portion of the earth's crust which is suited to the luxuriant
development of vegetable life, are connected by intimate
relations, and by reciprocal action, with the surrounding sea,
in which organic life seems almost limited to the animal world.
The liquid element is again covered by the atmosphere — an
aerial ocean into which the mountain chains and plateaus of
the dry land rise like shoals, and occasion a variety of cur-
rents and changes of temperature. Collecting moisture from
the region of clouds, these loftier tracts contribute also to
the spread of life and motion, by the beneficial influence of
the streams of water which flow down their declivities.
Whilst the geography of plants and animals depends on
GENERAL VIEW. 153
the intricate conditions of the distribution of land and
water, the general form of the surface, and the direction of
isothermal lines, or zones of equal mean annual tempera-
ture, it is far otherwise when we view the human race, — the
last and noblest subject in a physical description of the globe.
The characteristic differences observed in the races of men,
and their numerical distribution on the face of the earth,
are influenced, not alone by natural relations, but also, and in
a higher degree, by the progress of civilisation, and by moral
and intellectual culture, on which the political superiority
of nations depends. Some races, clinging, as it .were, to
the soil, are supplanted and gradually annihilated by the
dangerous vicinity of others whose social state is more ad-
vanced, and leave behind them but a faint historical trace
of their existence ; whilst other races, not the strongest in
point of number, navigating the liquid element in every
direction, have spread themselves over the whole surface of
the earth, and have thus been the first to attain, though late,
a graphical knowledge of the surface of our planet, or, at
least, of its coasts, from pole to pole.
Here, then, and before we enter on individual features of
that part of the contemplation of nature which embraces tel-
luric phenomena, I have shown generally in what way, from
the consideration of the Earth's form, and the ceaseless action
of the forces of electro-magnetism and subterranean heat,
we may embrace, in one view, the configuration of the
surface of the land both in horizontal extent and elevation,
the types of different geological formations, the liquid
ocean, the atmosphere with its meteorological processes, the
geographical distribution of plants and animals, and, finally,
the physical gradations of the human race which is exclu-
154 TEBRESTEIAL PHENOMENA.
sively and every where susceptible of intellectual culture.
This unity of contemplation presupposes a combination of the
phenomena according to their intimate mutual connection :
a mere juxtaposition of facts would not fulfil the object
which I have proposed to myself; it would not satisfy that
desire for cosmical presentation awakened in me by the
aspect of nature during long voyages by sea and land, by a
careful study of forms and forces, and by a vivid impression
of the unity of nature in regions of the earth differing most
widely from each other. Much which in this attempt is
exceedingly defective, will, perhaps, soon be corrected and
completed by the rapid advance of all branches of phy-
sical science ; for it belongs to the fuller development of
knowledge, that parts which were at first isolated become
gradually connected, and subjected to the dominion of
higher law. I but indicate the path of observation and
experience in which I, and many others of like mind with
myself, advance, full of expectation that, as Plato has told
us Socrates once desired, " Reason shall be the sole inter-
preter of Nature/' (126)
The description of the leading features of telluric pheno-
mena must begin with the form and relative dimensions of
the planet itself. Here, too, we may say, that as the crys-
talline, granular, and fossiliferous rocks respectively indicate
the modes of their formation, so the geometrical form of
the Earth reveals its earlier condition; an ellipsoid of
revolution indicating a once soft or fluid mass. Thus the
Earth's ellipticity constitutes, to the intelligent reader of
the book of nature, the record of one of the earliest telluric
facts. Analogous facts in the history of the Moon are
presented by the elliptical form of the lunar spheroid, and
FIGURE OF THE EARTH. 155
the constant direction of its major axis towards the Earth ;
the accumulation of matter on that half of the Moon which
is turned to us determines the relation of the periods of
rotation and revolution, and doubtless reaches back to the
earliest epoch in the history of the satellite. The mathe-
matical figure of the Earth " is that which it would have
if its surface were covered by water in a state of repose :"
it is to this imaginary surface, which is unaffected by the
accidents and inequalities of the true physical surface, that
all geodesical measurements of degrees are referred. (127)
The general figure of the Earth is determined when we know
the magnitude of the equatorial axis and the compression
at the poles ; but to obtain a complete representation of
its form, measurements in two directions, perpendicular to
each other, are required.
Eleven measurements of degrees (or determinations of the
curvature of the Earth's surface in different parts), of which
nine belong to the present century, have made known to us
the magnitude of our globe, which Pliny (128) long since
termed a " point in the immeasurable Universe.'" If these
measurements are not always accordant in giving equal
curvatures for the different meridians under the same parallel
of latitude, this very circumstance rather testifies in favour
of the accuracy of the instruments and methods employed,
and of the fidelity of the partial results. The conclusion
respecting the figure of a planet, from the increase of the
attracting force in going from the equator to the poles, is
dependent on the distribution of density in its interior. In
his immortal work, " Philosophise Naturalis Principia/'
Newton, incited probably by Gassings discovery of the ellip-
ticity of Jupiter (129) made previous to 1666, determined
156 TERRESTRIAL PHENOMENA.
from theoretical grounds the compression of the Earth, aa
a homogeneous mass, at -^-o. By the aid of new and more
perfect analysis, actual measurements have since shewn the
ellipticity of the terrestrial spheroid, when the density of the
strata is regarded as increasing towards the centre, to be
more nearly ^T.
Three methods have been employed in investigating the
curvature of the Earth's surface : it has been inferred from
measurements of degrees, from the vibrations of a pen-
dulum, and from certain inequalities in the Moon's orbit.
The first method is a direct geometrical and astronomical
one; in the other two, we infer from movements accu-
rately observed, the measure of the forces which occasion
those movements ; and from the inequality of the forces
we infer the difference between the equatorial and polar
diameters. In this part of the sketch of nature, I have
introduced an exception to the general manner of its treat-
ment, by noticing methods, because in this case they
afford a striking exemplification of the intimate connec-
tion existing between forms and forces in natural phse-
nomena; and also, because their employment has happily
given occasion to the attainment of a high degree of accuracy
in optical instruments, and in those employed in the mea-
surements of space and time, as well as to fundamental im-
provements in the astronomical and mechanical sciences,
and even to new and special branches of analysis. Except
the investigations concerning the parallax of the fixed stars,
which led to the discovery of aberration and nutation, the
history of science presents no problem in which the object
obtained, — the knowledge of the mean compression of the
Earth . and the certainty that its figure is not a regular one, —
FIGURE OP THE EAETH. 157
is so far surpassed in importance by the incidental gain
which, in the course of its long and arduous pursuit, has
accrued in the general cultivation and advancement of
mathematical and astronomical knowledge. The compari-
son of eleven measurements of degrees (including three
extra European, the old Peruvian and two East Indian
arcs), discussed by Bessel in a memoir in which due regard
is paid to the most modern refinements, gives an ellipticity
of -2-fg-, (13°) being a difference between the polar and equa-
torial semi -diameters, of 10938 toises (69648 English feet),
or about 11-6 geographical miles. The excess of the
equatorial radius resulting from the curvature of the surface
of the spheroid amounts, therefore, in the direction of gra-
vity, to more than 4-f- times the height of Mont Blanc, or
twice and a half the probable height of the summit of the
Dhawalagiri in the Himalaya Chain. The lunar inequalities
(perturbations of the Moon's motion in longitude and
latitude), give, according to Laplace's most recent investi-
gations, almost the same result for the Earth's ellipticity
as the measurements of degrees, viz. ?%-§. The experiments
with the pendulum give a much greater compression, viz.
-2Tr(131)' It is related that Galileo, when a boy, observed,
during the performance of divine service, that the height of
the vaulted roof of a church might be measured by means of
the time of vibration of chandeliers suspended at different
heights ; but he could scarcely have anticipated that pendu-
lums would one day be carried from pole to pole to determine
the figure of the earth. In this research it has been found
that the length of the seconds pendulum is aflected by the
unequal density of the superficial strata of the earth. This
geological influence on an instrument by wlich time is
158 TERRESTRIAL PHENOMENA.
measured, — this property of the pendulum, whereby, like a
sounding line, it searches unknown depths, and reveals in
volcanic islands, (132) or on the declivity of raised continental
mountain chains, (133) the presence of dense masses of basalt
and melaphyre, instead of subterranean cavities, — renders a
general result in the deduction of the figure of the earth
difficult of attainment, in spite of the admirable simplicity
of the^onethod. In the astronomical part also of the mea-
surement of degrees, mountain chains and rocks, or strata
of great density, exert, though in a less degree, a prejudicial
influence on the determinations of latitude.
As the figure of the Earth influences materially the
movements of other planetary bodies, and especially those
of her own satellite which is nearest to her, the more perfect
knowledge of the lunar movements enables us reciprocally
to infer from them the Earth's figure ; and thus, as Laplace
ingeniously remarked, (134) " an astronomer, without quit-
ting his observatory, may be able, from a comparison of the
lunar theory with actual observation, to determine not only
the form and magnitude of the Earth, but also its distance
from the Sun and Moon, — results only to be otherwise ob-
tained by long and arduous undertakings in the remotest
regions of both hemispheres/' The ellipticity inferred from
the lunar inequalities has an advantage not afforded either
by measurements of degrees or by pendulum experiments,
in being independent of local accidents, and thus shewing
the mean ellipticity of the planet. The comparison of the
Earth's figure with its velocity of rotation serves also tj
establish the increase of density of the strata from the sur-
face to the center ; an increase which the comparison of the
ratios of the polar and equatorial axes of Jupiter anil Saturn
DENSITY OF THE EARTH. 159
with their times of rotation, shews to exist also in those two
large planets. Thus the knowledge of the external form of
planetary bodies affords a basis for conclusions respecting
their internal constitution.
The northern and southern terrestrial hemispheres appear to
present nearly the same curvature under equal latitudes (135) j
but, as has been already remarked, pendulum experiments
and measurements of degrees give such different results for
different parts of the Earth's surface, that it is impossible
to assign any regular figure which shall satisfy all the results
obtained by these methods. The actual figure of the Earth
is probably to a regular figure, " as the uneven surface of
agitated water is to the even surface of water in repose."
Having thus measured the Earth, it had to be weighed ;
and here also the vibrations of the pendulum, and the em-
ployment of the plumb line, have served to determine its
mean density. This has been attempted in three ways : 1st,
by combining astronomical and geodesical operations for
the purpose of ascertaining the deflection of the plumb line
caused by the vicinity of a mountain; 2d, by comparing the
length of the pendulum vibrating seconds in a plain, and
on the summit of a mountain ; 3d, by employing a balance
of torsion, which may be regarded as a horizontal pendulum,
as a measure of the relative density of neighbouring strata.
Of these three methods (136) the last is the most certain,
because it is independent of the very difficult determina-
tion of the density of the mineral masses of which the
mountain consists, near which the observations of the
other two methods must be made. The most recent
experiments with the balance of torsion are those of
VOL. i. N
160 TERRESTRIAL PHENOMENA.
Beich, and give for their result 5-44 to 1 as the ratio of the
mean density of the Earth to that of distilled water. Now, we
know from the general nature of the rocks and strata which
form the dry or continental portion of the Earth's surface,
that their density can hardly amount to 2 '7, or that
of the land and sea surfaces taken together to 1*6; it
follows, therefore, that, either by pressure, or from the
heterogeneity of the substances, the elliptical strata in the
interior must undergo a great increase of density towards the
center of the Earth. Here, again, the horizontal (as before
the vertical) pendulum, shews itself to be justly entitled to
the name of a geological instrument.
The results thus obtained have led physical philosophers
of celebrity to form to themselves, according to the different
hypotheses from which they proceeded, wholly opposite views
respecting the nature of the interior of the globe. It has
been computed at what depths liquid and even gaseous
substances, from the pressure of their own superimposed
strata, would attain a density exceeding that of platinum,
or of iridium ; and in order to bring the actual degree of
ellipticity, which was known within very narrow limits, into
harmony with the hypothesis of the infinite compressibility
of matter, Leslie conceived the interior of the Earth to be
a hollow sphere, filled with " an imponderable fluid of enor-
mous expansive force." Such rash and arbitrary conjectures
have given rise, in wholly unscientific circles, to still more
fantastic notions. The hollow sphere has been peopled with
plants and animals, on which two small subterranean revolv-
ing planets, Pluto and Proserpine, were supposed to shed a
mild light. A constantly uniform temperature is supposed
to prevail in these inner regions, and the air being rendered
DENSITY OF THE EARTH. 161
self-luminous by compression, might well render the planets
of this lower world unnecessary. Near the north pole, in 8£°
of latitude, an enormous opening is imagined, from which
the polar light visible in Aurora streams forth, and by which
a descent into the hollow sphere may be made. Sir Hum-
phry Davy and myself were repeatedly and publicly invited
by Captain Symmes to undertake this subterranean expe-
dition : so powerful is the morbid inclination of men to fill
unseen spaces with shapes of wonder, regardless of the
counter-evidence of well-established facts, or universally
recognised natural laws. Even the celebrated . Halley, at
the end of the 17th century, hollowed out the Earth in
lus magnetic speculations; a freely rotating subterranean
nucleus was supposed to occasion, by its varying positions,
the diurnal and annual changes of the magnetic declination.
It has been attempted in our own day, in tedious earnest, to
invest with a scientific garb that which, in the pages of the
ingenious Holberg, was an amusing fiction.
The figure of the earth, its degree of solidification,
and its density, are intimately connected with forces
which act in its interior, apart from external influ-
ences, or the position of the planet relatively to the
luminous central body. We have considered the com-
pression or ellipticity as a consequence of the centrifugal
force acting on a rotating mass, and as evidencing an
earlier condition of fluidity in our planet: in the course
of the solidification of this fluid, (which some have been
inclined to assume to have been originally gaseous, and
heated to a very high degree of temperature,) an enormous
quantity of latent heat would have been disengaged ; and
TERRESTRIAL PHENOMENA.
supposing, with Fourier, the process of consolidation to
have commenced by radiation into space from the cool-
ing surface, the particles nearer to the center of the Earth
would have continued fluid and incandescent. After long
transmisson of heat from the center towards the surface, a
stable condition of the temperature would have been esta-
blished, when the heat would increase uninterruptedly with
increasing depth. The high temperature of water which
rises in very deep borings in Artesian wells, — direct obser-
vation of the temperature of rocks in mines, — and, above all,
the volcanic activity of the Earth, ejecting molten masses
from opened clefts or fissures, bear unquestionable evidence
to this increase for very considerable depths in the upper
terrestrial strata. Inferences, which are indeed founded
only on analogy, render the extension of this increase farther
towards the center more than probable. That which has
been learnt respecting the propagation of heat in homo-
geneous metallic spheroids, by means of an ingenious
analytical calculus perfected expressly for this class of in-
vestigations, (l37) can only be applied with great caution to
the actual constitution of our planet, considering our igno-
rance of the substances of which the Earth may be com-
posed,— of the different capacity for heat and conducting
power of the superimposed masses, — and of the chemical
changes which solid and fluid matter may undergo from
enormous pressure. That which is most difficult for us to
conceive and to represent to ourselves, is the boundary line
between the fluid interior mas.s and the solidified rocks
which form the outer crust ; or the gradual change from
the solid strata to the condition of semi-fluidity, a
condition to which the known laws of hydraulics can only
INTERNAL HEAT OF THE EAETH. 163
be applicable under considerable modifications. It seems
highly probable that the action of the Sun and Moon, which
produces the ebb and flow of the ocean, is also felt in these
subterranean depths. "We may suppose periodic heavings
and subsidings of the molten mass, and consequent varia-
tions in the pressure against the vaulted covering formed by
the solidification of the upper rocks. The amount and effects
of such oscillations must, however, be small ; and though the
relative position of the heavenly bodies may here also occa-
sion " spring tides," yet it is certainly not to these, but to
more powerful internal forces, that we must attribute the
movements which shake the surface of the Earth. There are
groups of phsenomena to the existence of which it may be
useful to refer, for the purpose of illustrating the universality
of the attraction of the Sun and Moon on the external and
internal condition of our globe, however little we may be
able to assign numerically the amount of such influence.
Tolerably accordant experience has shewn that in Arte-
sian wells, the average increase of temperature in the strata
pierced through is 1° of the Centigrade thermometer for
92 Parisian feet of vertical depth (54'5 English feet for 1°
of Fahrenheit) ; or if we suppose this increase to continue
in an arithmetical ratio, a stratum of granite would, as I have
already remarked (138), be in a state of fusion at a depth of
nearly 21 geographical miles, or between four and five times
the elevation of the highest summit of the Himalaya.
In the globe of the Earth three varieties in the mode of the
propagation of heat are to be distinguished. The first is
periodical, and causes the temperature of the strata to vary,
as, according to the position of the Sun and the season of
the year, the warmth penetrates from above downwards,
164 TERRESTRIAL
or, inversely, escapes by the same path. The second is
also an effect of the Sun; its action is extremely slow,
part of the heat which has penetrated into the Earth in the
equatorial regions travels along the interior of the Earth's
crust to the vicinity of the poles, where it escapes into the
atmosphere, and thence into space. The third is the slowest
of all ; it consists in the secular cooling of the terrestrial
globe ; in the escape of the very small quantity of the primi-
tive heat of the planet which is now given out from its surface.
The loss of central heat is supposed to have been very great at
the time of the early terrestrial revolutions, but within his-
toric periods it has hardly been appreciable by our instru-
ments. The temperature of the surface of the earth is
intermediate between the glowing temperature of the
inferior strata, and that of space which is probably below
the freezing point of mercury.
The periodic variations of the temperature, produced at
the surface by the position of the Sun and by meteorolo-
gical processes, propagate themselves towards the interior
of the Earth, but only to a very inconsiderable depth. The
slow conducting power of the soil diminishes the loss of
heat in winter, and is favourable to trees having deep roots.
At points placed at different depths on the same vertical
line, the maximum and minimum of the imparted tempera-
tures are attained at very different seasons ; and the greater
the distance from the surface, the less is the difference be-
tween the extremes of temperature. In our temperate
latitudes (48° — 52°) the stratum of invariable temperature
is found at a depth of from 55 to 60 French feet (59 to 64
English feet nearly) ; and at half that depth the oscillations
of temperature from the influence of season are already
MEAN TEMPERATURE OE THE EARTH. 165
diminished to less than 1° of Fahrenheit. In tropical cli-
mates the invariable stratum is only one foot below the sur-
face ; and Boussingault has ingeniously availed himself of this
fact to obtain a very convenient, and, as he thinks, certain
mode of determining the mean temperature of the air at a
station (139). This mean temperature of the air, either at a
fixed point, or at a group of points not far removed from each
other on the surface of the Earth, is, to a certain degree, the
fundamental element of the relations which determine the
climate, and the appropriate cultivation of a district; but
the mean temperature of the whole surface of the Earth is
very different from that of the Earth itself. The often
repeated questions, whether the superficial temperature has
undergone any considerable change in the course of cen-
turies,— whether the climate of a country has deteriorated, —
whether the winter may not have become milder, and the
summer at the same time cooler, — are all inquiries which
can only be Decided by means of the thermometer, an instru-
ment only invented about two centuries and a half ago,
and of which the intelligent scientific employment scarcely
dates back to 120 years. The nature and the novelty of the
means, therefore, restrict within very narrow limits cur
inquiries concerning the temperature of the air ; but it is
quite otherwise with the solution of the larger problem
regarding the internal temperature of the whole globe. A s
from the unaltered time of vibration of a pendulum we are
able to conclude that the equality of its temperature has
•been maintained, so the unchanged velocity of the Earth's
rotation furnishes a measure of the stability of its mean
temperature. This insight into the relation between the
length of the day and the heat of the globe, leads to a
166 TERRESTRIAL PHENOMENA,
most brilliant application of the long knowledge we possess
of the movements of the heavens to the thermic condition of
our planet. The velocity of the Earth's rotation depends on
her volume ; and since, therefore, by the gradual cooling of the
mass from the effects of radiation the axis of rotation would
become shorter, such decrease of temperature would be
accompanied by increased velocity of rotation and dimi-
nished length of day. Now the comparison of the secular
inequalities in the Moon's motion with eclipses observed by
the ancients, shews that since the time of Hipparchus, or
during an interval of two thousand years, the length of the
day has certainly not been diminished by one -hundredth
part of a second : we know, therefore, that the mean tem-
perature of the Earth has not altered, during that period, so
much as the — }-0 part of a Centigrade degree, or the -g-^-g- of
a degree of Fahrenheit. (14°)
This invariability of form presupposes also great inva-
fiability in the distribution of density in the interior of the
globe. Such transference of matter as is effected by the
action of our present volcanoes, the eruption of ferruginous
lavas, and the filling up of previously empty fissures and
cavities with dense mineral masses, are therefore to be
regarded merely as inconsiderable superficial phenomena,
wholly insignificant when considered in relation to the
dimensions of the Earth.
I have described the internal heat of our planet, both in
respect to its cause and distribution, almost exclusively from
the results of Fourier's admirable investigations. Poisson
doubted the uninterrupted increase of the Earth's tempera-
ture from the surface to the center ; he believed that its heat
had penetrated from without, and that the temperature of
TERHEST.RIAL MAGNETISM. 3 67
the globe was dependent on the high or low temperature of
the part of space through which the solar system has moved.
This hypothesis., imagined by one of the profoundest ma-
thematicians of our time, has been satisfactory to few, if
indeed to any one except himself, and has certainly not been
received by physicists and geologists.
But whatever may be the cause of the internal heat of our
planet, and its limited or unlimited increase at increasing
depths, it conducts us, in this general contemplation of
nature, through the intimate relation of all the primary phse-
nomena of matter, and through the common bond which
unites the molecular forces, into the obscure domain of Mag-
netism. Changes of temperature elicit magnetic and electric
currents. Terrestrial magnetism, of which, in its threefold
manifestation, incessant periodical variation is the leading
characteristic, is ascribed either to inequalities in the tempe-
rature of the globe, (141) or to those galvanic currents which
we regard as electricity moving in a closed circuit. (142) The
mysterious march of the magnetic needle is dependent both
on time and space, — on the course of the Sun, and on its
own change of place on the surface of the Earth. The hour of
the day may be known between the tropics by the direction
of the needle, as well as by the height of the mercury in the
barometer. It is affected instantly, though only transitorily,
by the distant Aurora — by the streams of richly coloured
light which shoot in bright flashes across the polar sky. When
the ordinary horary movement of the needle is interrupted
by a magnetic storm, the perturbation manifests itself, often
simultaneously in the strictest sense of the word, over land
and sea, over hundreds and thousands of miles; or propa-
168 TEERESTRIAL PHENOMENA.
gates itself gradually, in short intervals of time, in every
direction over the surface of the Earth. (143) In the first
case, the simultaneity of the phsenomena may serve, like
occupations of Jupiter's satellites, or like fire signals and
shooting stars, to determine within certain limits geogra-
phical differences of longitude. We recognise with wonder
and admiration, that the movements of two small magnetic
needles, even if suspended at depths beneath the surface
of the Earth, should measure the distance which divides
them from each other; that they should tell us how far
Kasan is situated east of Gottingen, or of the banks of the
Seine. There are parts of the Earth where the mariner, who
has been enveloped for many days in fog, seeing neither
Sun nor stars, and having no means of determining time,
may know with certainty, by an observation of the magnetic
Inclination, whether he is to the north or south of the port
which he desires to enter. (144)
When the sudden interruption or disturbance of the
horary movement of the needle announces the presence of a
magnetic storm, we are unhappily still unable to determine
the seat of the perturbing cause, whether it be in the
crust of the earth, or in the upper regions of the atmo-r
sphere. If we regard the earth as an actual magnet, we
know from the profound investigator of a general theory of
terrestrial magnetism, Friedrich Gauss, that to each portion
of the globe one-eighth of a cubic metre in volume, we must
assign an average amount of magnetism equal to that con-
tained in a magnetic bar of 1 Ib. weight. (145) If iron and
nickel, and probably cobalt (but not chrome, (146) as was
long believed), are the only substances which become per-
manently magnetic, and by a certain coercive force retain
TERRESTRIAL MAGNETISM. 169
polarity, the phenomena of Arago's magnetism of rotation,
and of Faraday's induced currents, on the other hand, shew
the probability that all terrestrial substances are capable of
assuming transitory magnetic relations. According to the
rotation experiments of the former of these two great
physicists, water, ice, (147) glass, carbon, and mercury, affect
the vibrations of a needle. Almost all substances shew them-
selves in a certain degree magnetic when they are acting as
conductors ; that is to say, when a current of electricity is
passing through them.
Although a knowledge of the attracting power of the
loadstone, or of naturally-magnetic iron, appears to have
existed from time immemorial among the nations of the
West, yet it is a well-established and very remarkable his-
torical fact, that the knowledge of the directive power of a
magnetic needle, resulting from its relation to the magnetism
of the Earth, was possessed exclusively by a people occupying
the eastern extremity of Asia, the Chinese. More than a
thousand years before our era, at the obscurely known
epoch of Codrus and the return of the Heraclides to the
Peloponnesus, the Chinese already employed magnetic cars,
on which the figure of a man, whose moveable out-
stretched arm pointed always to the south, guided them
on their way across the vast grassy plains of Tartary ;
and in the third century of our era, at least 700 years
before the introduction of the compass in the European
seas, Chinese vessels navigated the Indian Ocean (148) with
needles pointing to the south. I have shewn in another
work(149) what great advantages in topographical know-
ledge the magnetic needle gave to the Chinese geogra-
phers over their Greek and Roman contemporaries, to whom*
170 TERRESTRIAL PHENOMENA.
for example, the true direction of the mountain Chains of
the Apennines and Pyrenees always remained unknown.
The magnetic force of our planet is manifested at its
surface by three classes of phenomena ; one of these is the
varying intensity of the force, and the other two its varying
direction, shewn in the inclination of the magnetic needle
in the vertical plane, and in its declination from the geo-
graphical meridian. The aggregate effect may therefore be
represented graphically by three systems of lines, called
isodynamic, isoclinal, and isogonic ; or, of equal force, equal
dip or inclination, and equal variation or declination. The
distances apart, and the relative as well as absolute positions
of these lines, are undergoing continual change. At parti-
cular points on the Earth's surface, (15°) for example in the
western part of the Antilles, and in Spitzbergen, the mean
declination of the magnetic needle has scarcely undergone
any sensible change in the course of the last hundred years.
Elsewhere, when the isogonic curves, in their secular move-
ment, pass from the surface of the sea to that of a continent
or island of considerable extent, they appear to be retained
for a time, and the curves become thereby inflected. The
gradual change in the forms of the lines which accompanies
their translation, and modifies the extent of the spaces which
are occupied by east or west declination, makes it difficult
to recognise the nature of the changes and the analogies of
form in graphic representations belonging to different cen-
turies. Each branch of a curve has its history ; but in no
case does that history reach farther back, among the nations
of the West, than to that memorable epoch (13th Sept.,
1492), when the re-discoverer of the new world found the
line of no variation three degrees to the westward of the
meridian of the Island of Mores, one of the group of the
TE.RRESTRIAL MAGNETISM. 171
Azores. (151) At the present time the whole of Europe,
with the exception of a small part of Bussia, has west de-
clination. This only began to be the case late in the
17th century, the needle having first pointed due north in
London in 1657, and in Paris in 1669, an interval of
twelve years, notwithstanding the small distance which
divides these two capitals. In eastern Russia, east of
the mouth of the Volga, of Saratow, Nishni-Nowgorod,
and Archangel, the easterly declination of Asia is advancing
towards us. In the wide extent of Northern Asia, two
excellent observers, Hansteen and Adolph Erman, have
traced the extraordinary double curvature of the declination
lines, which are concave towards the pole between Obdorsk
on the Obi and Turucjiansk, and convex between Lake
Baikal and the Gulf of Ochotsk. In this last-named por-
tion of the earth, in North-eastern Asia, between the
Werchoiansk Mountains, lakoutsk, and Northern Corea,
the isogonic lines form a remarkable closed system. This
oval form (152) is repeated with still greater regularity, and
on a larger scale, in the Pacific Ocean, nearly in the meridian
of Pitcairn Island and the group of the Marquesas, between
20° N. and 45° S. latitude. We might be inclined to
regard so singular a configuration as the effect of local
peculiarity in those parts of the earth ; but if these
apparently isolated systems are found to change their place
progressively in the course of centuries, we must conclude
that these phenomena, like all great natural facts, appertain
to a general system, and have a general cause.
The horary variations of the decimation are apparently
governed by the sun whilst that body is above the horizon at
any spot; they also decrease in angular value with the decrease
178 TERRESTRIAL PHENOMENA.
of magnetic latitude: near the equator, in the Island of Rawak,
for example, they barely amount to three or four minutes,
while in middle Europe they attain to thirteen or fourteen
minutes. Throughout the northern hemisphere the move-
ment of the north end of the needle from 8£ A.M. to 1-' P.M.
or thereabouts, is from east to west ; and, as at the same hours
n the southern hemisphere, the same end of the needle
moves in the opposite direction, or from east to west, atten-
tion has been justly called (153) to the presumption, that
there must be a region of the earth, probably between the
terrestrial and magnetic equators, in which no horary varia-
tion of the declination is sensible. This fourth curve, which
might be called the curve of no motion, or line of no horary
variation of the declination, has not yet been found.
The name of magnetic poles has been applied to those
points on the Earth's surface where the horizontal force
disappears, and to these points more importance has been at-
tached than properly belongs to them; (154) in like manner
the curve on which the needle has no inclination, but rests
in a horizontal direction, has been called the magnetic
equator. The position of this li]ie, and its secular change
of form, have of late years been objects of careful investiga-
tion. According to the excellent memoir of Duperrey (155),
who crossed the magnetic equator six times between 1822
and 1825, the nodes or intersection of the two equators, or
the two points at wlu'ch the line without inclination crosses
the geographical equator and passes from one hemisphere
into the other, are unequally distributed; in 1825, the node
near the Island of St. Thomas on the "West Coast of Africa,
was 188£° from the node in the Pacific, which is near the
small islands called Gilbert Islands (nearly in the meridian
TERRESTRIAL MAGNETISM. 173
of the Yiti Islands). At the commencement of the present
century,, I determined the point where the magnetic equator
crosses the chain of the Andes, in the interior of the new
continent, between Quito and Lima, at an elevation of
nearly 12000 English feet above the level of the sea, in
7° V S. lat., and 48° 40' W. long, from Paris. To the
west of this point, throughout almost the whole breadth of
the Pacific, the line without dip, or magnetic equator,
though slowly approaching the geographical equator, conti-
nues in the southern hemisphere ; in the vicinity of the
Indian archipelago it passes into the northern hemisphere,
just touches the southern point of Asia, and enters the con-
tinent of Africa near the strait of Bab-el-Mandeb, which is
the point of its greatest distance from the geographic
equator. Thence, traversing the terra incognita of the
interior of Africa in a south-westerly direction, it re-enters
the southern hemisphere in the Gulf of Guinea, and, main-
taining a south-westerly course across the Atlantic, reaches
the Brazilian coast near Os Ilheos, north of Porto Seguro,
in 15° S. lat. From thence to the elevated plateau of the
Cordilleras, where I observed the inclination at a spot be-
ween the silver mines of Micuipampa and the ancient seat
of the Incas at Caxamarca, the line traverses a part of
South America as unknown to us as the interior of Africa.
Recent observations, collected and discussed by Sabine(156),
have taught us that, in the interval between 1825 and 1837,
the node jjear the Island of St. Thomas moved 4° from the
east towards the west. It would be extremely important to
learn whether the opposite node near the Gilbert Islands in
the Pacific, has undergone a corresponding westerly move-
ment, and advanced an equal amount towards the meridian
174 TERRESTRIAL PHENOMENA.
of the Carolinas. la investigating the laws of terrestrial
magnetism, it is no slight advantage that four-fifths of the
magnetic equator are oceanic, and are thus easily accessible,
and that we now possess the means of determining the de-
clination and inclination on board ship with great exactness.
The changes which alter the places of the nodes, and modify
the form of the magnetic equator, are felt in the remotest
regions of the earth, where also they produce changes of the
inclination and of the magnetic latitude. (157)
We have spoken of the distribution of magnetism on the
surface of our planet according to the two forms of declina-
tion and inclination: it still remains to notice the third
form, that of the intensity of the force, which is expressed
graphically by isodynamic curves, or curves of equal inten-
sity. The investigation and measurement of this force by
means of the oscillations of a vertical or horizontal needle,
has excited a general and lively interest, which, in its appli-
cation to the distribution of the magnetic force on the
surface of the globe, commenced with the present century.
By the application of refined optical and chronometrical
means, the measurement of the horizontal force, in par-
ticular, has become susceptible of a degree of accuracy
exceeding that of all other magnetic determinations.
Doubtless the isogonic lines are of the greatest practical
importance, from their use in navigation ; but in respect to
the theory of terrestrial magnetism, the isodynamic lines are
those from which the most fruitful results are expected. (158)
The first fact in reference to these lines which direct observa-
tion made known was the increase of the intensity of the total
force in proceeding from the equator towards the pole.(159)
It is to the unwearied activity of Edward Sabine, from the
TERRESTRIAL MAGNETISM. 175
year 1819 to the present time, that we are principally in-
debted for the knowledge of the variations of the magnetic
intensity over the whole surface of the globe, and for their
laws so far as we are yet able to infer them. After having
himself vibrated the same needles in the vicinity of the
North American pole, in Greenland, in Spitzbergen, on the
coast of Guinea, and in Brazil, he has been constantly
engaged in collecting and co-ordinating all the materials
capable of elucidating the great question of the isodynamic
lines. The first sketch of an isodynamic system divided
into zones was given by myself, for a small portion of South
America. The isodynamic lines are not parallel with the
isoclinal lines; the intensity is not, as was first supposed,
weakest at the magnetic equator, nor is it even equal at all
parts of that line. If we compare Erman's observations
(0*706), in the southern part of the Atlantic ocean, where a
zone of weak intensity extends from Angola past the Island
of St. Helena to the Coast of Brazil, with the most recent
observations of the great navigator James Clark Ross, we
find that on the surface of our planet the force augments
almost in a ratio of 1 : 3. The highest intensity which has
been measured is 2*071, in lat. 60° 19' and long. 131° 20'
E. from Greenwich. (16°) These values are expressed in
terms of the scale of which the unity is the intensity which
I observed on the magnetic equator, in tiie north of Peru.
In Melville Island (74° 27' N.), in the neighbourhood of
the northern magnetic pole, the force was found by Sabine
only 1*624, while at New York in the United States, almost
in the same latitude as Naples, he found it 1*803.
The brilliant discoveries of Oersted, Arag9, and Earaday,
have established intimate relations between the electric
VOL. i. o
176 TERRESTRIAL PHENOMENA.
tension of the atmosphere and the magnetic charge of the
Earth. According to Oersted, a conductor is rendered
magnetic by the electrical current which passes along it.
According to Earaday, magnetism gives rise, by induction,
to electrical currents. Thus magnetism is one of the
manifold forms under, which electricity shews itself; and
the ancient obscure presentiment of the identity of electric
and magnetic attraction has been realised in our own
days. Pliny, (161) in accordance with Thales and the Ionic
school, says, "The electrum (amber), when animated by
friction and warmth, attracts fragments of bark and dry
leaves, just as the magnetic stone does iron/' We find a
remark to the same effect in a speech of the Chinese philo-
sopher Kuopho in praise of the virtues of the magnet. (162)
It was not without surprise that I noticed, on the shores of
the Orinoco, children, belonging to tribes in the lowest
stage of barbarism, amusing themselves by rubbing the dry,
fiat, shining seeds of a leguminous climbing plant (probably
a Negretia), for the purpose of causing them to attract
fibres of cotton or bamboo. It was a sight well fitted to
leave on the mind of a thoughtful spectator a deep and
serious impression. How wide is the interval which sepa-
rates the simple knowledge of the excitement of electricity
by friction, shewn in the sports of these naked copper-
coloured children of the forest, from the invention of a
metallic conductor which draws the lightning from the
storm-cloud, — of the voltaic pile effecting chemical decom-
position,— of a magnetic apparatus evolving light, — and of
the magnetic telegraph ! Such intervals of separation are
equivalent to thousands of years in the progress and intel-
lectual development of the human race.
TEREESTRIAL MAGNETISM. 177
The perpetual fluctuation observed in all the magnetic
phenomena, in the inclination, declination, and intensity of
the force, according to the hours of the day and even of the
night, the season of the year, and the lapse of years, leads to
the belief in the existence of very various and complicated
systems of electric currents in the crust of the Earth. (163)
Are these, as in Seebeck's experiments, simple thermo-
magnetic currents, the immediate effect of unequal dis-
tribution of heat, or currents induced by the calorific
action of the Sun ? Has the rotation of the Earth, and the
velocity of its different zones according to their distance from
the equator, any influence on the distribution of magnetism ?
Is the source of magnetic action to be sought in the atmo-
sphere, or in the interplanetary spaces, or in a polarity of
the Sun and Moon ? Galileo, in his celebrated " Dialogo,"
ascribes the constant parallel direction of the Earth's axis to
a center of magnetic attraction existing in space.
If we conceive the interior of the Earth to be molten,
subject to enormous pressure, and raised to a temperature
for which we possess no measure, we must renounce the
idea of a magnetic nucleus. Though at a white heat all
magnetism disappears, (164) it is still sensible in iron heated
to a dark-red glow; and whatever may be the modifica-
tions which, in these experiments, the molecukxr condition
and consequently the coercitive force undergo, there must
still remain a considerable thickness of terrestrial strata, in
which we might seek the seat of the magnetic currents. In
the old explanation of the horary variations of the declina-
tion, by the progressive warming of the Earth by the Sun
in his apparent course from east to west, the action would
indeed be limited to the extreme exterior surface ; for ther-
178 TERRESTRIAL PHENOMENA.
mometers sunk in the Earth, which are now accurately
observed at many places, show how slowly the heat of the
Sun penetrates even to the small depth of a few feet.
Moreover, the thermic condition of the surface of the sea,
which covers two -thirds of the planet, is but little favourable
to an explanation assuming an immediate influence, and not
an induced action proceeding from the gaseous and aqueous
strata of the atmosphere.
In the present state of our knowlede, no satisfactory
reply can be given to questions respecting the ultimate
physical causes of phseriomena so complex. On the other
hand, that part of the subject which, in the threefold mani-
festations of the Earth's magnetic force, presents relations
admitting of measurememt in regard to space and time, — and
which leads us to discern, amidst constant and apparently
irregular change, the order and dominion of laws, — has
recently made the most brilliant progress in the determina-
tion of mean numerical values. Erom Toronto, in Canada, to
the Cape of Good Hope and Van Diemen's Land, and from
Paris to Pekin since 1S28, the globe has been covered by
magnetic observatories, in which every movement or mani-
festation, regular and irregular, of the Earth's Magnetic
force, is watched by uninterrupted and simultaneous obsei-
vation. A variation of 4 0 /, 0 0 of the magnetic intensity
is measured. At certain epochs observations are taken
at intervals of two minutes and a half, and are continued
during twenty-four consecutive hours. A great English
astronomer and physical philosopher, has computed (165) that
the mass of observations to be discussed amount in three
years to 1958000. Never before has an effort so grand,
and so worthy of admiration, been made to investigate the
TERRESTRIAL MAGNETISM. 179
quantitative m the laws of one of the great phsenomena of
nature. We may therefore justly hope, that these laws, when
compared with those which prevail in the atmosphere and
in still more distant spaces, will gradually conduct us nearer
to the genetical explanation of the magnetic forces. As
yet we can only boast of having opened a greater number of
paths which may possibly lead to such explanation. In the
physical theory of terrestrial magnetism (which must not be
confounded with its purely mathematical theory), as in that
of the meteorological processes of the atmosphere, a prema-
ture satisfaction can only be obtained by those who permit
themselves to set aside as erroneous, all those phenomena
which are inconsistent with their own views. (166)
Telluric magnetism, and the electro-dynamic forces mea-
sured by the ingenious Ampere, (l67) are intimately con-
nected both with the terrestrial or polar light (Aurora), and
with the external and internal temperature of our planet,
whose magnetic poleshave been regarded by some philosophers
as poles of cold. (168) That which, more than 130 years ago,
Halley (169) put forward as a bold conjecture, viz. that the
Aurora is a magnetic phsenomerion, has, by Faraday's
brilliant discovery of the evolution of light by the action of
magnetic forces, been raised from a mere conjecture to an
experimental certainty. There are precursors of the Aurora ;
the luminous nocturnal appearance is usually foretold by
antecedent irregularity in the diurnal inarch of the magnetic
needle, indicating a disturbance in the equilibrium of the
distribution of the Earth's magnetism. When the disturb-
ance has reached a great degree of intensity, the equilibrium
is restored by a discharge accompanied by an evolution of
180 TERRESTRIAL PHENOMENA.
light. The Aurora (W) is not, therefore, to be itself re-
garded as a cause of the perturbation, but as the result of
a state of telluric activity excited to the production of a
luminous phenomenon ; an activity which manifests itself,
on the one hand, by the fluctuations of the needle, and, on
the other, by the appearance of the brilliant auroral light.
The magnificent phenomenon of coloured polar light is the
act of discharge, the termination of a magnetic storm, — as
in the electric storm, an evolution of light (lightning) indi-
cates the restoration of the equilibrium in the distribution
of the electricity. The electrical storm is usually confined
to a small space, beyond which the state of electricity in the
atmosphere remains unchanged. The magnetic storm, on
the contrary, manifests its influence on the march of the
needle, over large portions of continents, and far from the
place where the evolution of light is visible, as was first re-
discovered in our own age by Arago. It is not improbable
that, as clouds of threatening appearance and heavily
charged with electricity, do not always proceed to the point
of discharge by lightning, owing to frequent transitions in
the electrical state of the atmosphere, so magnetic storms
may produce great disturbances in the ordinary diurnal
march of the magnetic needle over a wide range, without
its necessarily following that the equilibrium of distribution
must be restored by explosion, or by luminous effusions from
the pole to the equator, or from pole to pole.
If we desire to collect into one view all the features of the
phenomenon, we may describe the commencement and
successive phases of a complete appearance of the Aurora as
follows : — Low down on the horizon, about the part where
it is intersected by the magnetic meridian, the sky, which
POLAll LIGHT, OB, AUEOBA. 181
was previously clear, is darkened by an appearance resem-
bling a dense bank or haze, which gradually rises and
attains a height of eight or ten degrees. The colour of the
dark segment passes into brown or violet, and stars are
visible through it as in a part of the sky obscured by thick
smoke. A broad luminous arch, first white, then yellow,
bounds the dark segment ; but as the bright arch does not
appear until after the segment, Argelander considers that
the latter cannot be attributed to the mere effect of contrast
with its bright margin. (171) The azimuth of the highest
point of the luminous arch, when carefully measured, (172)
has been usually found not quite in the magnetic meridian,
but from five to eighteen degrees from it, on the side
towards which the magnetic declination of the place is
directed. In high northern latitudes in the near vicinity
of the magnetic pole, the dark segment appears less dark,
and sometimes is not seen at all ; and in the same locali-
ties, where the horizontal magnetic force is weakest, the
middle of the luminous arch deviates most widely from the
magnetic meridian. The luminous arch undergoes frequent
fluctuations of form ; it remains sometimes for hours before
rays and streamers are seen to shoot from it and rise to the
zenith. The more intense the discharges of the Aurora, the
more vivid is the play of colours, from violet and bluish-
white through all gradations to green and crimson. In the
common electricity excited by friction, it is also found that
the spark becomes coloured only when a violent explosion
follows high tension. At one moment the magnetic streamers
rise singly, and are even interspersed with dark rays, re-
sembling dense smoke; at another they shoot upwards
simultaneously from many and opposite points of the hori-
182 TEERESTHIAL PHENOMENA.
zon, and unite in a quivering sea of flame, the splendour of
which no description can reach, for every instant its bright
waves assume new forms. The intensity of this light is
Sometimes so great, that Lowenorn (29th January, 1786)
discerned its corruscations during bright sunshine. Motion
increases the visibility of the phenomenon. The rays
finally cluster round the point in the sky corresponding to
the direction of the dipping needle, and there form what is
called the corona — a canopy of light of milder radiance,
streaming, but no longer undulating. It is only in rare
cases that the phenomenon proceeds so far as the complete
formation of the corona ; but whenever this takes place, the
display is terminated. The streamers now become fewer,
shorter, and less intensely coloured ; the corona and the
luminous arches break up, and soon nothing is seen but
irregularly scattered, broad, pale, shining patches of an
ashy-grey colour ; and even these vanish before the trace
of the original dark segment has disappeared from the
horizon. The last that remains of the whole spectacle
is often merely a white delicate cloud, feathered at the edges,
or broken up into small round masses, like cirro cutnuli.
This connection of the polar light with the most delicate
cirrous clouds deserves particular attention, because it
shews us the electro-magnetic evolution of light as part of a
meteorological process. The magnetism of the Earth is
here exhibited in its influence on the atmosphere, and on the
condensation of aqueous vapour. The observation of
Thienemann, in Iceland, who regarded the light detached
fleecy clouds as the substratum of the Aurora, has been
confirmed in modern times by Franklin and Richardson
in the neighbourhood of the American magnetic pole, aud
POLAR LIGHT, OR AURORA. 183
by Wrangel on the Siberian coast of the Polar Sea.
They all remark, that the Aurora shoots forth the most
vivid rays when masses of cirro-strati are hovering in the
upper region of the atmosphere, and when they are so thin
that their presence can only be discovered by the formation
of a halo round the Moon. These clouds sometimes ar-
range themselves in the day-time like the rays of the
Aurora; and in such cases the movements of the needle
are similarly affected by them. After a great nocturnal
display of Aurora, there have been recognised early in the
morning the same streaks of cloud which had before been
luminous. (173) The apparently converging "polar bands"
(streaks of cloud in the direction of the magnetic meridian),
which continually engaged my attention during my journeys
both on the high table lands of Mexico and in Northern
Asia, belong probably to the same group of diurnal phseno-
mena. (174)
Southern lights have been repeatedly seen in England by
Daltori, and northern lights have been seen in the southern
hemisphere as far as 45° S. latitude (14th January, 1831) ;
it not unfrequently happens, also, that the magnetic
equilibrium is simultaneously disturbed in the direction of
both poles. I have distinctly ascertained that the polar
light has been seen within the tropics, in Mexico and Peru.
It is necessary to distinguish between the sphere of simul-
taneous visibility of the phenomena, and the zones of the
Earth in which it is seen almost nightly. Every observer
certainly sees his own Aurora as well as his own rainbow ;
but the phenomenon of the effusion of light is generated
by a large portion of the Earth at once. Many nights may
be cited when it was observed simultaneously in England
184 TERRESTRIAL PHENOMENA.
and in Pennsylvania, at Rome and at Pekin. When it is
stated that Auroras decrease in frequency and brilliancy
with decreasing latitude, it must be understood of magnetic
latitude. Whilst an Aurora is a very rare occurrence in
Italy, it is extremely common in the same latitude in
Philadelphia (39° 57'), owing to the vicinity of the Ame-
rican magnetic pole; and in Iceland, Greenland, New-
foundland, on the shores of the Slave Lake, and at Tort
Enterprise, the " merry dancers," (175) as the inhabitants
of the Shetland Islands call the quivering and variously-
coloured rays of the Aurora, are seen during certain seasons
of the year almost every night. But even in those parts
of the new continent and of Siberia which are distin-
guished by the frequency of the phenomenon, there may be
said to be different districts or zones of longitude in
which it shews itself with peculiar splendour. (176) Wrangel
saw its brilliancy diminish at Nishni Kolymsk, as he receded
from the coast of the Polar Sea ; in this and in similar
instances local influences are not to be denied. The expe-
rience of the various North Polar expeditions seems to shew
that in the immediate vicinity of the magnetic pole the
evolutions of light are, to say the least, not more intense or
frequent than at somewhat greater distances.
What we know of the height of the Aurora is grounded
on measurements which, from their nature, and from
the incessant fluctuation of the phenomenon and con-
sequent uncertainty of the parallactic angle, cannot inspire
much confidence. Without including older statements, the
results of these measurements give heights varying from a few
thousand feet to several miles. (177) The most modem ob-
servers are inclined to place the seat of the phenomenon, not
POLAU LIGHT, OR AURORA, 185
at the limits of the atmosphere, but in the region of clouds :
they even believe that the rays of the Aurora may be moved to
and fro by winds and currents of air ; and this may be the case,
if the luminous phsenomenon which manifests to us the pre-
sence of an electro-magnetic current, be actually connected
with groups of vesicles of vapour in motion ; or, to speak
more exactly, if it traverses the group, darting from one
vesicle to another. Franklin saw an Aurora near Great
Bear Lake, the light of which appeared to him to illuminate
the under surface of the stratum of cloud ; while, at the dis-
tance of only eighteen miles, Kendal, who was on watch all
night, and never lost sight of the sky, observed no luminous
phseuomenon whatsoever. In respect to the statements re-
cently made from several quarters, of rays of the Aurora being
seen to shoot down in close proximity to the Earth, between
the observer and a neighbouring hill, it must be remembered
that, as in the case of lightning and of fire balls, there is in
several ways danger of optical illusion
Whether the magnetic storms manifested by Auroral
display (of which we have just noticed one instance remark-
ably restricted in respect to locality) share with electric
storms the phenomena of sound as well as of light, has be-
come extremely doubtful since the accounts of Greenland
whalers and Siberian fox-hunters have ceased to obtain im-
plicit confidence. The Auroras have become more silent since
observers have better understood how to observe them, and
how to listen for them. Parry, Franklin, and Richardson
near the north magnetic pole, Thienemann in Iceland,
Giesecke in Greenland, Lottin and Bravais near the North
Cape, Wrangel and Anjou on the Siberian coasts of the
Polar Sea,, have together seen thousands of northern lights
186 TERllESTEIAL PHENOMENA.
without ever hearing a noise. Even if it be considered that
this negative evidence ought not to countervail the positive
testimony of two observers, Hearne at the mouth of the
Coppermine River, and Henderson in Iceland, it must be
remembered that Richardson and Hood heard, indeed, a
sound, which one terms " a hissing noise, like that of a
musket bullet passing through the air/' and of which the
other says, " that it resembled the noise of a wand waved
smartly through the air ;" but though both were inclined to
regard these sounds as connected with the Aurora, each adds
that they were attributed "by Dr. Wentzel to the con-
tracting of the snow from a sudden increase of cold •" and
this opinion was supported "by the same sounds being
heard the following morning/' (Pages 585 and 628 of the
Appendix to " Eranklin's First Journey to the Polar Sea/')
Wrangel and Giesecke arrived at the same persuasion, thai
sounds heard during Auroras do not proceed from them,
but are to be ascribed to contractions of the ice, and of the
crust on the surface of the snow, from sudden increase of
cold. The belief of a crackling noise did not originate
with uncultivated persons having frequent opportunities of
noticing the Aurora, but with learned travellers ; the cause
probably being, that as electric flashes in spaces filled only
with a very rare atmosphere had been observed to resemble
the northern light, the latter phenomenon was regarded as
an effect of atmospheric electricity, and thus people
heard what they expected they ought to hear. Recent
experiments, however, with regard to atmospheric elec-
tricity, made with very sensitive electrometers, have hitherto,
contrary to all expectation, given only negative results, since,
during the finest Auroras, no change has been detected.
POLAR LIGHT, OB AURORA. 187
On the other hand, all the three manifestations of terrestrial
magnetism, the declination, inclination, and force, are affected
during the appearance of the polar light ; so that in the
course of the same night, and during different parts of the
phsenomenon, the same end of the needle is sometimes
attracted and sometimes repelled. The statement that the
facts collected by Parry in Melville Island, in a high mag-
netic latitude, indicated rather a tranquillizing than a
disturbing influence of Auroras upon the magnet, has been
refuted by a more careful examination of Parry's own
journal, (178) by the valuable observations of Richardson,
Hood, and Franklin, and latterly by Bravais and Lottin
in Lapland. As I have before remarked, the luminous
phenomenon is the act of restoration of equilibrium
temporarily disturbed ; the effect on the needle varies with
the intensity of the discharge; at the winter station
of Bosekop it was always sensible, except when the
luminous phsenomenon was very faint, and appeared only
low down near the horizon. The Auroral streamers
have been ingeniously compared to the light which, in
the Voltaic circuit, is produced between two points of
carbon placed at a considerable distance from each other,
(or, according to Eizeau, between a point of carbon and
one of silver) ; a light which is attracted or repelled by the
magnet. This analogy renders superfluous the assump-
tion of metallic vapours in the atmosphere, which some
celebrated physicists have considered to be the substratum
of the Aurora.
In applying to the luminous phsenomenon which we
ascribe to a galvanic current the vague term of polar light,
or Aurora borealis and australis, we merely indicate thereby
188 TERRESTRIAL PHENOMENA.
the direction in which the evolution of light most frequently,
but by no means always, commences. The fact which gives to
the phenomenon its greatest importance is, that the Earth
becomes self-luminous ; that besides the light which, as a
planet, it receives from the central body, it shews a
capability of sustaining a luminous process proper to itself.
The intensity of the "terrestrial light," or rather of the
degree of illumination which it diffuses at the surface of
the Earth, when the rays are brightest, are coloured, and
ascend to the zenith, is a little greater than that given
by the Moon in her first quarter. Sometimes (as on the
7th of January, 1831) it has been possible to read print by
it without effort. This terrestrial luminous process, going
on almost uninterruptedly in the polar regions, leads us by
analogy to the remarkable phenomenon presented by Venus,
when the portion of that planet not illumined by the Sun
is seen to shine with a phosphorescent light of its own. It
is not improbable that the Moon, Jupiter, and the comets,
radiate a light generated by themselves, in addition to the
reflected light which they receive from the Sun and which
is recognised by means of the polariscope. Without speak-
ing of the enigmatical but not uncommon kind of lightning,
which, unaccompanied by thunder, is seen flickering
throughout the whole of a low cloud for minutes together,
we have yet other examples of the production of terrestrial
light. To these belong the celebrated mists, luminous at
night, seen in the years 1783 and 1831 ; the steady luminous
appearance in great clouds observed by Eozier and Beccaria;
and even, as Arago ingeniously remarks, the faint diffused
light which guides our steps in densely clouded moonless
and starless autumn or winter nights, and when no snow is
POLAE, LIGHT, OK ATJEORA. Lo9
on the ground. (179) In high latitudes a flood of brilliant
and often coloured light streams through the atmosphere in
polar light or electro-magnetic storm ; and in the torrid zone
many thousands of square miles of ocean are also seen to
generate at once a light of their own ; in the latter case
the magic brightness belongs to organic nature : each
breaking wave curls in luminous foam; the whole wide
expanse sparkles, and every spark is the vital movement of
a minute and otherwise invisible world of animal existence.
Manifold, no doubt, are the sources of the terrestrial light ;
and we may even imagine it as existing latent and not yet
set free from combination with vapours, as a means of
explaining Moser's pictures produced at a distance, —
a discovery in which reality as yet presents itself to us
like the unsubstantial images of a dream.
If, on the one hand, the internal heat of our planet may be
connected with the excitement of electro-magnetic currents,
and the evolution of terrestrial light accompanying a mag-
netic storm, it is also a principal source of geological pheno-
mena. We shall trace this connection in passing from the
purely dynamic effect manifested in earthquakes, and the
elevation of entire continents and mountain masses, to the
production and issue of gases and liquids, of hot mud, and
of glowing and molten earths which harden into crystalline
rocks. It is no small advance made by modern geology (or
the mineralogical part of terrestrial physics), to have investi-
gated the connection of the phenomena here indicated. The
insight which we thus obtain leads away from the unpro-
fitable hypotheses by which it was formerly sought to explain
each such manifestation of force singly and independently :
190 REACTION OF THE INTERIOR OP THE EARTH
it shews the relations which subsist between the ejection
of various substances on the one hand, and earthquakes
and elevations on the other ; it classes together groups of
phsenomena which appear at the first glance very hetero-
geneous, as thermal springs, exhalations of carbonic acid gas
and sulphureous vapour, harmless eruptions of mud, and
the devastating phsenomena of active volcanoes. In a ge-
neral view of nature, all these phenomena are comprehended
under the one idea of the action of the interior of a planet
upon its crust and surface. Thus in the increase of
temperature in the interior of the Earth as we descend
from the surface, we recognise the germ not only of earth-
quakes, but of the gradual elevation of continents, and of chains
of mountains from extended fissures, of volcanic eruptions,
and of the production of very various minerals and rocks.
But it is not inorganic nature only which is influenced by
the reaction of the interior on the exterior. It is very pro-
bable that in an earlier state of the globe, far greater emis-
sions of carbonic acid gas mingled with the atmosphere, and
heightened the process by which plants assimilate carbon ;
and thus vast forests were formed, which in subsequent
revolutions were destroyed, and inexhaustible stores of fuel
(lignites and coal) were buried in the terrestrial strata then
forming at the surface. Nor should we overlook that the
destinies of men are in part dependent also on the form of
the outer crust of the Earth, on the direction and elevation
of mountain chains, and on the divisions and articulations
of upheaved continents. The investigating spirit is thus
enabled to ascend from link to link in the chain of phseno-
mena, to the supposed epoch of the solidification of the
planet, when, in its first transition from a gaseous to a
ON ITS EXTERIOR. EARTHQUAKES. 191
liquid or a solid form, the internal heat not due to the
calorific action of the solar rays was developed.
In order to give a brief general view of the causal con-
nection of geological phenomena, we will begin with those
whose principal character is dynamic. Earthquakes are
distinguished by rapidly succeeding vertical, horizontal,
or circular oscillations. In the not inconsiderable num.
ber of these phenomena which I have witnessed both on
the old and new continents, at sea and on land, the two
first kinds of movement, the vertical and horizontal, have
often appeared to me to take place together. The mine-
like explosion, the vertical action from below upwards,
shewed itself in the most striking manner at the over-
throw of the town of Eiobamba in 1797, where many
corpses of the inhabitants who perished were hurled to
a height of several hundred feet on the hill of La Cullca,
beyond the small river of Lican. The shock is propagated
chiefly in a linear direction, by undulations having a velo-
city from twenty to twenty- eight geographical miles in a
minute, and occasionally in circles or ellipses of commotion,
in which the shocks are propagated from the center to the
circumference, but with diminishing force. There are dis-
tricts which belong to two intersecting circles. In Northern
Asia, where the father of history, Herodotus, (18°) and at
a later epoch Theophylactus Simocatta, (181) spoke of
Scythia as free from earthquakes, I have found the southern
and richly metalliferous part of the Altai mountains subject
to the double influences of the foci of commotion of Lake
Baikal and of the volcanoes of the Thian-schan (" celestial
mountains"). (182) Where the circles of disturbance inter-
sect,— where, for example, an elevated plateau is situated
between two volcanoes in a state of activity, — several systems
VOL. i. P
192 REACTION OF THE INTERIOR OF THE EARTH
of waves may exist simultaneously, and produce their
effects, as in fluids, without mutual disturbance. We may
even imagine interferences, as in intersecting waves of
sound. The magnitude of the waves propagated in the
crust of the Earth will be increased at the surface, accord-
ing to the general law in mechanics by which vibrations
transmitted in elastic bodies have a tendency to detach the
superficial strata.
The undulations in earthquakes have been examined with
tolerable accuracy, in respect to their direction and intensity,
by means of pendulums and sismometers; but in their
characters of alternation and periodical intumescence they
have by no means attracted sufficient attention. In the
city of Quito, which is situated at the foot of a still
active volcano, the Rucu-Pichincha, and at an elevation
above the sea of 8950 (9539 English) feet, and which
possesses fine cupolas, high roofed churches, and massive
houses of several stories in height, I have been often
surprised in the night by the violence of the earthquake
shocks ; but these, though extremely frequent, very rarely
injure the walls, whereas, in the Peruvian plains, even low
dwellings built of reeds suffer from apparently far slighter
oscillations. Natives of those countries, who have expe-
rienced many hundred earthquakes, believe this difference to
depend less on the greater or less duration of the shocks, or
the slowness or rapidity (183) of the horizontal oscillation,
than on alternation of motion in opposite directions.
The circular (or gyratory) earthquakes are the most rare,
and at the same time the most dangerous. In the great
earthquake of Eiobamba in the province of Quito (4th
February, 1797), and in that of Calabria (5th February, and
2bth March, 1783), walls were changed in direction without
ON ITS EXTERIOR. EARTHQUAKES. 193
being overthrown, straight and parallel rows of trees were
inflected, and in fields having two sorts of cultivation, one
crop even took the place before occupied by the other : the
latter phenomenon shewing either a movement of translation,
or a mutual penetration of different portions of the ground.
When making a plan of the ruined city of Riobamba, I was
shewn a place where the whole furniture of one house had been
found under the remains of another ; the earth had evidently
moved like a fluid in streams or currents, of which we
must assume that the direction was first downward, then
horizontal, and lastly again upward. Disputes concerning
the ownership of objects which had been thus carried to
distances of many hundred yards, were decided by the
Audiencia, or Court of Justice.
In countries where earthquakes are comparatively rare,
for example in the south of Europe, an imperfect induction
has led to the very general belief that they are always pre-
ceded by calms, oppressive heat, and a misty horizon. (184)
This popular error is however refuted, not merely by mr
own experience, but also by the observations of all those
who have lived many years in districts such as Cumana, Quito,
Peru, and Chili, where the earth is frequently and violently
shaken. I have felt shocks in serene weather as well as in
rain, and during a fresh east wind as well as during a
storm. Even the regularity of the horary variations of the
magnetic declination, and of the pressure of the atmo-
sphere, (185) were not disturbed on the days of earthquakes.
My observations were made within the tropics ; and those
made by Adolph Erman in the temperate zone, during
an earthquake at Irkutsk near Lake Baikal on the Stb of
March, 1829, give a similar result. At Cum an a, on the
194 BEACTION OF THE INTERIOR OF THE EARTH
4th of November, 1799, I found no change either in
the magnetic declination or intensity from a strong shock
of earthquake; but, on that occasion, I observed with
astonishment that the inclination was diminished 48'. (186)
I had no reason to suspect any error, although, during
a great number of other shocks and earthquakes ex-
perienced by me in the highlands of Quito and Lima,
the inclination, as well as the other elements of terres-
trial magnetism, always remained unaltered. If, however,
these deep-seated terrestrial movements are not generally
announced by any peculiar state of the atmosphere or
appearance of the sky, it is, on the other hand, as we shall
soon see, not improbable, that in some very violent earth-
quakes the aerial strata have participated, and that the
phenomena are not, therefore, always purely dynamic.
During the long-continued trembling of the ground in the
Piedmontese valleys of Pelis and Clusson, great variations in
the electric tension of the atmosphere were remarked, quite
independently of any storm, and when the sky was perfectly
clear.
The hollow noise which most frequently accompanies
earthquakes by no means increases in proportion to the
violence of the oscillations. I- have distinctly ascertained
that the great shock of the earthquake of Eiobamba (4th
February, 1797), one of the most terrible phenomena in the
physical history of our globe, was unaccompanied by any
noise; the great subterranean detonation (el gran ruido),
which was heard at the cities of Quito and Ibarra, (but not
at Tacunga and Hambato which were nearer the center of
the movement,) occurred eighteen or twenty minutes after
the catastrophe. In the celebrated earthquake of Lima and
Callao, October 23th 1746, a noise, resembling a sub-
ON ITS EXTERIOR. EARTHQUAKES. 195
terranean thunder-clap, was heard a quarter of an hour
later at Truxillo, and was unaccompanied by any trembling
of the ground. In like manner, it was not till some time
after the great earthquake of New Granada, November 16,
1827, described by Boussingault, that subterranean detona-
tions, unaccompanied by any movement, were heard with
great regularity at intervals of thirty seconds, throughout
the whole Cauca Valley. The nature of the noise also dif-
fers greatly ; sometimes it is rolling, and occasionally like the
clanking of chains ; in the city of Quito it has sometimes
been abrupt, like thunder close at hand, and sometimes clear
and ringing, as if obsidian or other vitrified masses clashed,
or were shattered in subterranean cavities. As solid bodies
are excellent conductors of sound, — which is propagated, for
example, in burnt clay with a velocity ten or twelve times
greater than in air, — the subterranean noise may be heard at
great distances from the place where it has originated. In the
Caraccas, in the grassy plains of Calaboso, and on the banks
of the Bio Apure which falls into the Orinoco, there was
heard over a district of 2300 square (German) miles, a
loud noise resembling thunder, unaccompanied by any
shaking of the ground; whilst, at a distance of 632 miles
to the north east, the crater of the volcano of St. Vincent,
one of the small West India Islands, was pouring forth a
prodigious stream of lava. In point of distance, this was as
if an eruption of Vesuvius should be heard in the north
of Erance. In 1744, at the great eruption of Cotopaxi,
subterranean noises, as of cannon, were heard at Honda,
near the Magdalena River. Not only is the crater of
Cotopaxi about 18100 English feet higher than Honda,
but these two points are separated from each other by a
196 REACTION OF THE INTERIOR OF THE EARTH
distance of 436 miles, and by the colossal mountain masses
of Quito, Pasto, and Popayan, as well as by countless val-
leys and ravines. The sound was clearly not propagated
through the air, but through the earth, and at a great depth.
During the violent earthquake in new Granada in February
1835, subterranean thunder was heard at Popayan, Bogota,
Santa Martha and Caraccas (where it lasted seven hours
without any movement of the ground), and also in Hayti,
in Jamaica, and near the Lake of Nicaragua.
These phenomena of sound, even when unaccompanied
by sensible shocks, produce a peculiarly deep impres-
sion, even on those who have long dwelt on ground
subject to frequent trembling. One awaits with anxiety
that which is to follow the subterranean thunder. \ The
most striking instance of uninterrupted subterranean
noise, unaccompanied by any trace of earthquake, is the
phenomenon which is known in the Mexican territory by
the name of "the subterranean roaring and thundering,
(bramidos y truenos subterraneos) of Guanaxuato." (18?)
This rich and celebrated mountain city is situated at a dis-
tance from any active volcano. The noise began on the 9th
of January, 1784, at midnight, and lasted above a month.
I have been enabled to give a circumstantial description of
the phenomenon from the report of many witnesses, and
from the documents of the municipality, which I was per-
mitted to make use of. Prom the 13th to the l-6th of
January, it was as if there were heavy storm clouds under
the feet of the inhabitants, in which slow rolling thunder
alternated with short thunder- claps. The noise ceased gra-
dually, as it had commenced ; it was confined to a small space,
for it was not heard in a basaltic district at the distance
ON ITS EXTERIOR. EARTHQUAKES. 197
of only a few miles. Almost all the inhabitants were terrified
and quitted the city, in which large masses of silver were
stored ; but the most courageous, when they had become
somewhat accustomed to the subterranean thunder, returned
and fought with the bands of robbers who had taken pos-
session of the treasure. Neither at the surface, nor in
mines 1598 English feet in depth, could the slightest
trembling of the ground be perceived. In no part of the
whole mountainous country of Mexico had any thing similar
been ever known before, nor has this awful phsenomenon
been since repeated* Thus, as chasms in the interior of the
Earth close or open, the propagation of the waves of sound
is either arrested in its progress, or continued until it
reaches the ear.
The activity of a burning mountain, however awfully
picturesque the spectacle which it presents to us, is
always limited to a very small space; whereas earth-
quakes, whose movements are scarcely perceptible to the
eye, propagate their waves sometimes to distances of
many thousand miles. The great earthquake which, on
November 1st, 1755, destroyed Lisbon, and the effects of
which have been well traced out by the great philosopher
Kant, was felt in the Alps, on the coasts of Sweden, in
the West India Islands '(Antigua, Barbadoes, and Mar-
tinique), on the great lakes of Canada, in Thuringia,
in the flat country of northern Germany, and in small
inland lakes on the shores of the Baltic. Remote foun-
tains were interrupted in their flow, a phenomenon of
earthquakes which had even been noticed among the an-
cients by Demetrius of Calatia. The thermal springs at
Toplitz dried up, and again returned, inundating every
198 REACTION OF THE INTERIOR OF THE EARTH
tiling with water discoloured by ochre. At Cadiz the sea
rose above sixty feet ; and in the West India Islands above
mentioned, where the tide usually rises only from twenty-six to
twenty-eight French inches, it suddenly rose above twenty
feet, the water being discoloured and of an inky blackness.
It has been computed that, on that day (] st November, 1755),
a portion of the earth's surface, four times greater than the
extent of Europe, was simultaneously shaken. There is no
manifestation of force yet known to us (including the
murderous inventions of our own race), by which a greater
number of human beings have been killed in the short
space of a few seconds or minutes, than in the case of earth-
quakes : sixty thousand were destroyed in Sicily in 1693 ;
thirty to forty thousand at Eiobamba, in 1797 ; and perhaps
five times as many in Asia Minor and Syria under Tiberius
and the elder Justinian, in the years 19 and 526.
Examples have occurred in the Andes of South America, in
which the earth has been shaken uninterruptedly for several
successsive days ; but of tremblings felt almost every hour for
months together, I am at present only aware of instances at
a distance from any volcano ; as on the eastern declivity of the
Mont Cenis portion of the chain of the Alps at Fenestrelles
and Pignerol from April 1808; in the United States of
America, between New Madrid and Little Prairie (north
of Cincinnati) in December 1811, as well as in the whole
winter of 1812 ;(188) and in the Pachalic of Aleppo in
August and September 1822. From the popular dispo-
sition to ascribe great phsenomena to local causes, rather
than to rise to general views, wherever the shaking of the
earth is long continued, fears of the breaking out of a new
volcano are entertained. In particular and rare cases, these
ON ITS EXTERIOR. EARTHQUAKES. 199
fears have been realised by the sudden appearance of volcanic
islands ; and a remarkable instance occurred in the eleva-
tion of the volcano of Jorullo, 1682 English feet above the
ancient level of its site and of the plain in which it now stands,
which took place the 29th of September, 1759, after eighty
days of earthquakes and subterranean thunder.
If we could obtain daily intelligence of the condition of
the whole surface of the earth, we should very probably
arrive at the conviction that this surface is almost always
shaking at some one point ; and that it is incessantly affected
by the reaction of the interior against the exterior. The
frequency and universality of a phenomenon, which probably
owes its origin to the high temperature of the interior and
deep-seated molten strata, explain its independence of the
nature of the rocks in which it manifests itself. Earthquake
siiocks have been felt even in the loose alluvial soil of Hol-
land, Middelberg, and Flushing (23d Feb. 1828). Granite
and mica slate are shaken, as well as limestone and sand-
stone, trachyte and amygdaloid. It is not the chemical
nature of the constituent particles, but the mechanical struc-
ture of the rocks, which modifies the propagation of the
shock or of the wave which occasions it. Where such a
wave proceeds in a regular course along a coast, or at the
foot of and parallel to the direction of a mountain chain,
interruptions at certain points have sometimes been re-
marked, and continue for centuries ; the undulation passes
onward in the depth below, but it is never felt at those
points of the surface. The Peruvians say of these upper
strata which are never shaken, that they form a bridge. (189)
As the mountain chains themselves appear to have been
elevated over fissures., it may be that the walls of these
200 REACTION OF THE INTERIOR OF THE EARTH
cavities favour the propagation of the undulations moving
in their own direction ; sometimes, however, the waves
intersect several chains almost at right angles ; an example
of which occurs in South America, where they cross both the
littoral chain of Venezuela and the Sierra Parime. In Asia
shocks of earthquakes have been propagated from Lahore and
the foot of the Himalaya (22d Jan. 1832), across the chain of
the Hindoo Coosh, as far as Badakschan, or the upper Oxus,
and even to Bokhara. (19°) The range of the undulations is
sometimes permanently extended, and this may be a conse-
quence of a single earthquake of unusual violence. Since
the destruction of Cumana on the 14th Dec. 1797, and only
since that epoch, every shock on the southern coast extends
to the mica slate rocks of the peninsula of Maniquarez,
situated opposite the chalk hills of the main land. In the
great alluvial vallies of the Mississipi, the Arkansas, and the
Ohio, the progressive advance from south to north of the
almost uninterrupted undulations of the ground between 1811
to 1813, was very striking. It would seem as if subterranean
obstacles were gradually overcome ; and that the way being
once opened, the undulatory movement is propagated through
it on each occasion.
If earthquakes appear at first sight to produce solely dy-
namical effects, we learn on the other hand, from well-
established evidence, that not only are whole districts of
country elevated by them above their former level (such as
the UUa-Bund, east of the Delta of the Indus, after the
earthquake of Cutch in June 1819, — rand the coast of Chili
in November 1822) but also that during their occurrence va-
rious substances are ejected from the earth; such as hot-water
at Catania in 1818; hot steam in the Valley of the Mississipi at
ON ITS EXTERIOR. EARTHQUAKES. 201
New Madrid in 1812; noxious gases which injured the herds
of cattle grazing on the chain of the Andes ; mud, black
smoke, and even flames, at Messina in 1783, and at Cumana
on the 14th Nov. 1797. During the great earthquake of
Lisbon (1st Nov. 1755), flames and a column of smoke
were seen to issue from a newly-formed fissure in the rock of
Alvidras, and the smoke was more dense as the subterranean
noise became louder. (191) At the destruction of Riobamba
(1797), where the shocks were not accompanied by any erup-
tion of the closely adjacent volcano, a singular mass (called
by the natives Moya), in which carbon, crystals of augite,
and siliceous shells of infusoria were intermingled, was pushed
up in numerous small conical eminences. During the
earthquake of New Granada (16th Nov. 1827), carbonic
acid gas issuing from fissures in the valley of the Magdalena
Eiver suffocated many snakes, rats, and other animals which
live in holes. Great earthquakes have sometimes been
followed in Quito and Peru by sudden changes in the
weather, and by a premature commencement- of the tropical
rainy season. Do gaseous fluids issue from the interior of
the earth and mingle with the atmosphere? or are these
meteorological processes the effects of a disturbance of the
electricity of the atmosphere by the earthquake ? In inter-
tropical parts of America, where sometimes, for ten months
together, not a drop of rain falls, repeated earthquake shocks,
which do no injury to the low reed-huts of the natives, are
regarded by them as the welcome harbingers of abundant
rain and a fruitful season.
The common origin of the different phenomena which have
been thus described, is still wrapped in obscurity. Elastic
fluids subjected to enormous pressure in the interior of the
202 EEACTION OF THE INTERIOR OP THE EARTH
globe no doubt occasion the slight and perfectly harmless
tremblings of the crust of the earth lasting several days, (such
as those which were experienced in 1816 at Scaccia in Sicily,
before the volcanic elevation of the new island of Julia), as well
as those terrible explosions which are accompanied by loud
noises. Bui the focus of the action, the seat of the moving
force, is placed deep below the crust of the earth, and we
can as little judge of the depth as we can of the chemical
nature of the fluids so powerfully compressed. At the edge
of the crater of Vesuvius, and on the towering cliff which
rises above the great abyss of the crater of the Pichincha
near Quito, I have felt periodical and very regular shocks, oc-
curring from twenty to thirty seconds before the eruption of
the incandescent scoriee or gases. The shocks were greatest
when the explosions were at long intervals, and when, there-
fore, the gases were longer in accumulation. Tin's simple
experience, confirmed by many travellers, contains the
general solution of the phenomenon. Active volcanoes may
be regarded as safety-valves for the country in their im-
mediate vicinity. The danger increases when the openings
of the volcanoes are stopped, and the free communication
with the atmosphere impeded ; but the destruction of Lisbon,
of Caraccas, of Lima, of Cashmeer in 1554,(192) and of so
many towns of Calabria, Syria, and Asia Minor, shews that
on the whole the most violent shocks do not usually take
place in the vicinity of still active volcanoes.
As the impeded activity of volcanoes influences the force of
earthquakes, so do the latter react on volcanic phenomena.
The opening of fissures favours the elevation of cones or
craters of eruption, and the chemical processes which take
place in the cones by free contact with the atmosphere*
ON ITS EXTEIIIOIU EARTHQUAKES.
A column of smoke which was seen for some months to rise
from the volcano of Pasto in South America, suddenly dis-
appeared, when, on the 4th of February, 1797, the province
of Quito, one hundred and ninety-two miles to the south-
ward, was visited by the great earthquake of Riobamba.
Tremblings of the ground, which had long been felt over the
whole of Syria, in the Cyclades, and in the island of
Euboea, suddenly ceased when a stream of lava issued
forth in the plains near Chalcis.(193) The celebrated
geographer of Amasea, from whom we have received this
account, adds, " Since the craters of Etna have been opened
through which fire issues, and since glowing masses and
water have been ejected from them, the lands near the sea-
shore have not been so often shaken as in the time when,
previous to the separation of Sicily from Lower Italy, all
the issues were closed." "We thus see that the force which
manifests itself in earthquakes, acts also in the phsenomena
of volcanoes ; but though as universally diffused as the in-
ternal heat of the planet, and making its presence everywhere
known, it is only rarely, and at insulated points, that its
accumulated energy produces the phsenomenon of eruption.
The formation of veins, *. e. the filling up of fissures with
crystalline masses issuing from the interior (basalt, mela-
phyre, and greenstone), gradually impedes the free escape of
the elastic fluids. They then accumulate, their tension
increases, and their reaction against the crust of the earth
shews itself in three different ways, — in earthquakes, — in
sudden elevations, — or in slow and continuous elevations,
winch alter progressively the relative levels of the land and
eea. The last mode of action produces effects which are
only sensible at intervals of long period, and was observed
for the first time over a considerable portion of Sweden,
204 REACTION OP THE INTERIOR OF THE EARTH
Before we quit this important class of phenomena, which
I have considered not so much in its individual as in its
general, physical, and geological relations, I would advert
to the cause of the deep and peculiar impression pro-
duced on the mind by the first earthquake which we
experience, even if it is unaccompanied by subterranean
noise. I do not think that this impression is produced
by the recollection at the moment of the dreadful images
of destruction, which historic relations of past catastrophes
have presented to our imaginations : it is rather occa-
sioned by the circumstance that our innate confidence in
the immobility of the ground beneath us is at once shaken.
From our earliest childhood we are accustomed to contrast
the mobility of water with the immobility of the earth : all
the evidences of our senses have confirmed this belief; and
when suddenly the ground itself shakes beneath us, a natural
force of which we have had no previous experience presents
itself as a strange and mysterious agency. A single instant
annihilates the illusion of our whole previous life ; we feel the
imagined repose of nature vanish, and that we are ourselves
transported into the realm of unknown destructive forces.
Every sound affects us — our attention is strained to catch
even the faintest movement of the air — we no longer trust
the ground beneath our feet. Even in animals similar inquie-
tude and distress are produced ; dogs and swine are particu-
larly affected, and the crocodiles of the Orinoco, which at all
other times are as dumb as our little lizards, leave the agi-
tated bed of the river and run with loud cries into the forest.
To man, the earthquake conveys a sense of danger of which
he knows not the extent or limit. The eruption of a vol-
cano, the flowing stream of lava threatening his habitation,
can be fled from -, but in the earthquake, turn where he will,
ON ITS EXTERIOR. ERUPTIONS OF GAS. 205
danger and destruction are around him and beneath Ills
feet. Though such emotions are deeply seated, they are not
of long duration. The inhabitants of countries where long
series of weak shocks succeed each other, lose almost every
trace of fear. On the coasts of Peru, where rain scarcely
ever falls, and where hail, lightning, and thunder, are un-
known, these atmospheric explosions are replaced by the
subterranean thunder which accompanies the trembling of
the earth. Erom long habit, and a prevalent opinion that
dangerous shocks are only to be apprehended two or three
times in a century, slight oscillations of the ground scarcely
excite so much attention in Lima as a hail storm does in
the temperate zone.
Having thus taken a general view of the active internal ter-
restrial forces ; — of the earth's heat, its electro-magnetic cur-
rents, its auroral light, and the irregular action of those forces
at the surface of the earth, — we will now proceed to the pro-
duction of material substances, and to the chemical changes of
which the crust of the earth and the constitution of the atmos-
phere is the theatre. We see steam and carbonic acid gas
issue from the ground almost always free from any admixture
of nitrogen (124), — carburetted hydrogen gas (which has been
used for more than a thousand years in the Chinese province
of Sse-tchuan,(195) and recently in the village of Eredonia
in the North American State of New York, both for culinary
purposes and for illumination), — sulphuretted hydrogen and
sulphurous vapours, — and more rarely sulphurous acids and
hydrochloric acid gas.(196) The fissures of the earth from
whence the vapours and gases issue are not peculiar to
districts of active or of long extinct volcanoes, but occur
•206 REACTION OP THE INTERIOR OP THE EARTH
also in countries where neither trachyte nor other volcanio
rocks are present at the surface. In the Cordillera of
Quindiu, at an elevation of 6830 English feet above the
sea, I have seen sulphur deposited in mica slate from hot
sulphureous vapours; (197) and to the south of Quito, in
the Cerro Cuella, near Tiscan, the same rock, which was
formerly regarded as primitive, contains an immense deposit
of sulphur imbedded in pure quartz.
Of gaseous emissions, those of carbonic acid are, as far
as we yet know, the most numerous and the most abun-
dant. In Germany, in the deep ravines of the Eifel, in
the vicinity of the Laacher-See, in the crater-like valley of
Wehr, and in Western Bohemia, exhalations of carbonic
acid gas appear as a last effort of volcanic; activity, in and
near its ancient foci in an earlier state of the globe.
With the high terrestrial temperatures of that period, and
the numerous fissures which were not then filled up, tlie
processes which we have here described, and in which carbonic
acid gas and hot steam mingled in considerable quantities
with the atmosphere, must have acted far more powerfully ;
and then, as Adolphe Brongniart has shewn, the vegetable
world must have attained everywhere, almost independently
of geographical position, the most luxuriant development and
abundance. (198) In this constantly warm and moist atmos-
phere loaded with carbonic acid gas, plants must have found
both the stimulus and the superabundant nourishment, which
piepared them for becoming the materials of those nearly
inexhaustible stores of coal, on which the physical power arid
prosperity of nations are based. Beds of this fuel are
accumulated in basins in particular parts of Europe, in the
British Islands, in Belgium, in France, on the Lower Bhine,
ON ITS EXTERIOR. HOT AND COLD SPRINGS. 207
and in upper Silesia. At the same early period of generally
distributed volcanic activity, there also issued from the
earth the enormous quantity of carbonic acid, which, in
combination with lime, has formed the limestone rocks, and
of which the carbon alone, in a solid form, constitutes
about the eighth part of their absolute bulk. (199) The
portion of carbonic acid which was not absorbed by the
alkaline earths, but still remained in the atmosphere, was
gradually consumed by the luxuriant vegetation ; and the
atmosphere being thus purified by the vital action of plants,
retained only that extremely minute portion which we
now find, and which is not injurious to the present condi-
tion of animal life. More abundant exhalations cf the
vapours of sulphuric acid, in the inland waters of the ancient
world, appear to have occasioned the destruction of the nu-
merous species of fish and mollusca which inhabited them, and
the formation of the contorted beds of gypsum which have
doubtless been subjected to the frequent action of earthquakes.
Gases, liquids, mud, and melted lavas (the last emitted
through volcanic cones, and to be regarded as a kind of
" intermittent springs," (20°) all issue from the earth at the
present day under similar relations. All these substances
owe their temperature and their chemical nature to the place
of their origin. The mean temperature of springs is less
tbtui that of the air at the points where they issue, when
their waters descend from greater elevations , and the tem-
perature increases according to the depth of the stratum
with which they are in contact at their origin. The nu-
merical law of this increase has been already stated ; but
I have found, from my own observations and those of my
VOL. I. Q
208 REACTION OF THE INTERIOR OF THE EARTH
companions in Northern Asia, that the mixture of the waters
from the various sources from which springs originate —
mountains, hills, or deep subterranean strata— makes it very
difficult to determine the position of the " Isogeothermal
lines" (201) (lines of equal internal terrestrial heat), from the
temperature of water as it issues from the earth. The tem-
perature of springs, which, for the last half century, has been
so much an object of physical research, depends, indeed, like
the limit of perpetual snow, on the concurrent influence of
many and very complicated causes. It is a function of the
temperature of the stratum in which they take their rise, of
the specific heat of the soil, and also of the quantity and tem-
perature of the water which falls, in rain, snow, or hail, (203)
and which, from the conditions of its origin, has a different
temperature from that of the air in the lower portion of the
atmosphere. (203) In order that cold springs may shew the
true mean temperature of the place where they issue from the
ground, they must be unmixed with waters coming either from
great depths, or from mountain elevations; and they must have
passed through a long subterranean course, at a depth below
the surface of about forty to sixty feet in our latitudes,
and, according to Boussingault, of one French foot within
the tropics : (204) these depths being those at which the
temperature is supposed to be constant, or unaffected by the
horary, diurnal, or monthly variations of the temperature of
the atmosphere.
Hot springs issue from rocks of every kind; the
hottest permanent springs yet known are those found by
myself, at a distance from any volcano, — the " Aquas ca-
lientes de las Trincheras," in South America, between
Porto Cabello and New Valencia, and the "Aquas de
ON ITS EXTERIOR. HOT AND COLD SPRINGS. 209
Comangiilas," in the Mexican territory near Guanaxuato. The
first of these had a temperature of 90°.3 Cent. (194°.5 Fahr.),
and issued in granite; the latter in basalt, with a tem-
perature of 96°.4 Cent. (205°.5 Fahr.). According to our
present knowledge of the increase of heat at increasing
depths, the strata, by contact with which these temperatures
were acquired, are probably situated at a depth of about
7800 English feet, or above two geographical miles. If the
internal terrestrial heat be the general cause of thermal springs
as well as active volcanoes, the rocks which the waters
traverse can influence the temperature only by their different
capacity for heat and their conducting powers. The hottest
permanent springs (between 95° and 97° Cent., or 203°
and 209° Fahr.) are also the purest, containing the smallest
portion of mineral substances in solution, but their tempera-
ture appears to be less constant than that of springs between
50° and 74° Cent. (122° and 165° Fahr.), which, in Europe at
least, have been found remarkably uniform, both in tem-
perature and mineral contents ; having undergone no change
for the last fifty or sixty years, or since 4 the application
of exact thermometric measurement and accurate chemical
analysis. The thermal springs of las Trincheras, on the
other hand, have increased about 7° Cent, (or 12° Fahr.) in
twenty-three years ; their temperature having been observed
by myself, in 1800, to be 90°.3Cent. (194°5. Fahr.), while
in 1823, according to Boussirigault,(205) it reached 97° Cent.
(or 206°.6 Fahr.) . This gently flowing source is therefore, at
the present time, almost 7° Cent. (12°. 6 Fahr.) hotter than
the intermitting fountains of the Geyser and the Strokr, of
which the temperatures have been recently determined with
great care by Krug of Nidda, The elevation of the new
volcano of Jorullo, unknown before my American jouniev,
210 REACTION OF THE INTERIOR OF THE EARTH
offers a remarkable example of ordinary rain water sinking
to a great depth, where it acquires heat, and afterwards re-
appears at the surface of the earth as a thermal spring.
When, in September 1759, Jorullo was suddenly elevated to
a height of 1682 English feet above the surrounding plain,
the two small streams called Eio de Cutimba and Rio de San
Pedro disappeared, and some time afterwards broke forth
afresh from the ground during severe earthquake shocks,
forming springs, whose temperature, in 1803, I found to be
05°.8 Cent, (or 150°.4 Mir.)
The springs in Greece still flow at the same places as
in the Hellenic times : the spring of Erasinos, on the slope
of the Chaon, two hours' journey to the south of Argos,
was mentioned by Herodotus ; the Cassotis at Delphi, now
the well of St. Nicholas, still rises on the south of the
Lesche, and its waters pass under the temple of Apollo ; the
Castalian fount still flows at the foot of Parnassus, and the
Pirenian near Aero-Corinth ; the thermal waters of ^Edepsos
in Euboea, in which Sylla bathed during the war of Mithri-
dates, still exist. (2o6) I take pleasure in citing these details,
which shew that, in a country subject to frequent and
violent earthquakes, the relative condition of the strata, and
even of those narrow fissures through which these waters find
a passage, has continued unaltered during at least two thou-
sand years. The " Fontaine jaillissante" of Lillers, in the
Departement du Pas de Calais, bored in 1126, still reaches
the same height, and gives the same quantity of water, as at
first. I may add that the excellent geographer of the Cara-
manian coast, Captain Beaufort, saw in the district of the
ancient Phaselis, the same flames fed by emissions of the
same inflammable gas, which Pliny has described as the flame
of the Lycian Chimera. (207)
ON ITS EXTEHIOH. MUD VOLCANOES. 211
The remark made by Arago, in 1821, that the deepest
Artesian wells are the warmest, threw new and important
light on the origin of thermal springs, and on the investiga-
tion of the law of increase of terrestrial heat at increas-
ing depths. (208) It is a striking circumstance, which has
been only recently noticed, that, at the end of the third cen-
tury, Saint Patricks, (209) who was probably bishop of Pertusa,
was led, by a consideration of the hot springs which issue
from the ground near Carthage, to form very correct views
regarding these phsenomena. To inquiries as to what might
be the cause of boiling water thus issuing from the earth,
he replied, " Tire is nourished in the interior of the earth
as well as in the clouds, as you may learn both from Mount
Etna and another mountain near Naples. Waters rise from
beneath the ground as in siphons ; those at a distance from
the subterranean fire are colder, but those which have their
source near the fire are heated by it, and bring with them to
the surface which we inhabit an insupportable degree of heat/'
As earthquakes are often accompanied by emissions of
water and elastic fluids, we may recognise in the Salses, or
small " mud volcanoes/' a transitional phsenomenon between
issues of gaseous fluids and of thermal springs, and the grand
and awful phsenomenon of streams of lava issuing from
burning mountains. On the one hand, we may consider
the mountains as springs or fountains sending forth, in-
stead of water, molten earths forming volcanic rocks ;
and, on the other hand, we should remember that thermal
springs, impregnated with carbonic acid and sulphurous
gases, are continually depositing successive horizontal beds
of travertin, or forming conical hills as in Algeria in Nor
them Africa, and in the Banos of Caxamarca on the
212 REACTION OF THE INTERIOR OP THE EARTH
western declivity of the Peruvian chain of the Andes. The
travertin of Van Diemen Island (near Hobarton), contains,
as we learn from Charles Darwin, the remains of vegeta-
tion belonging to the earlier ages of the world. It may be
noticed, that lava and travertin, which are rocks still formed
beneath our eyes, present to us the two extremes in geologi-
cal relations.
The phenomena of nrad volcanoes are deserving of more
attention than geologists have hitherto given to them ; their
grandeur has been overlooked, because, of the two phases
presented by them, it is only the second, or calmer state,
lasting for centuries, which has usually been described : but
their origin is accompanied 'by earthquakes, subterranean
thunder, the elevation of great districts of country, and lofty
jets of flame of short duration. When the mud volcano of
Jokmali, on the peninsula of Abscheron, east of Baku on
the Caspian Sea, was first formed, on the 27th of No-
vember, 1827, flames blazed up to an extraordinary height
for a space of three hours, and during the following twenty
hours they rose about three feet above the crater from
which mud was ejected. Near the village of Baklichli, west
of Bacu, the column of flame rose so high that it could be
seen at a distance of twenty-four miles. Enormous frag-
ments of rock, torn doubtless from depths, were hurled to a
great distance round. Similar fragments are seen around the
now tranquil mud volcano of Monte Zibio, near Sassuolo ii
Northern Italy. For fifteen centuries, the Silician Salse
near Girgenti (Macalubi), described by the ancients, has
continued in the secondary stage of activity ; it consists of
several conical mounds, from eight or ten to thirty feet
Ingh, subject to variation both in form and height. Streams
of argillaceous mud, accompanied by periodical disengage-
ON ITS EXTERIOR. VOLCANOES. 213
merits of gas, flow from very small basins containing water
at the summits of the cones. In these cases the mud is
usually cold, but sometimes it has a high temperature, as
at Damak in the province of Samarang in Java. The gaseous
eruptions, which are accompanied by noise, vary in their
nature, consisting sometimes of hydrogen gas mixed with
naphtha, sometimes of carbonic acid, and even occasionally
of almost pure nitrogen, as Parrot and myself have shewn
in the peninsula of Taman, and in the South American
volcancitos of Turbaco. (21°)
After the violent explosions and flames which accom-
pany the first appearance of mud volcanoes, and which
may not perhaps be common to all in an equal degree,
they present to the observer an image of the constant
but feeble activity of the interior of the globe. It would
seem' as if, soon after their first formation, the channels
of communication with the very deep strata having a
high temperature became obstructed, and the coldness
of the mud emitted appears to indicate that, during the
more permanent condition of the phenomenon, the seat of
activity is situated not very far below the surface. The
reaction of the interior of the earth upon its crust manifests
itself far more powerfully in volcanoes properly so called,
viz. at points where there exists a communication, either
permanent or reopened from time to time, with deep-seated
volcanic foci. We must, however, carefully distinguish be*
tween volcanic phsenomena of greater or less intensity, —
between earthquakes, thermal springs, and jets of steam ;
mud volcanoes ; the elevation of bell-shaped or dome-shaped
trachytic hills or mountains, without openings ; the forma-
tion of an opening at the summits of such mountains, or of
214 REACTION OF THE INTERIOR OF THE EARTH
craters of elevation in basaltic districts ; and lastly, the
appearance of a permanent volcano within the crater of
elevation itself, or among the debris of its earlier formation.
At different epochs, and in different stages of activity and
force, permanent volcanoes em?*- aqueous or acid vapours
and ignited scoriae, or, when the resistance is overcome,
glowing streams of molten earth.
Sometimes great but local manifestations of force in the
interior of our planet, acting by means of elastic vapours,
upheave portions of the Earth's crust in dome-shaped un-
broken masses of felspathic trachyte and of dolerite (Puy de
Dome and Chimborazo) ; or the upheaved strata are broken
through, so as to present a slope on the exterior side, and
a steep precipice towards the interior which forms the inclo-
sure or bounding wall of a crater of elevation. When it is
a part of the bottom of the sea which has been thus ele-
vated (which is by no means always the case), the form
and character of the upheaved island are determined there-
by. In this manner have originated the circular form of
Palma, so well described by Leopold von Buch, and also
that of Nisyros in the ^Egean Sea.(211) Sometimes a part
of the annular circumference has been destroyed, and in the
bay where the sea has entered, families of coral animals
have built up their cellular habitations. Even on conti-
nents, craters of elevation are often filled with water, and
the lakes thus formed impart to the landscape a picturesque
beauty of a very peculiar kind. The formation of these
€t craters of elevation'" is independent of the nature of the
rock ; they are found in basalt, trachyte, leucite porphyry
(Somma), and in combinations of augite and labradorite :
hence the varieties of their form and aspect. "No phenomena
of eruption, however, proceed from these craters; nor is
OX ITS EXTERIOK. VOLCANOES. 215
there any permanent channel of communication open with
the interior; it is only rarely that any traces of modern
volcanic activity are found either within them or in their
vicinity. The force capable of producing such considerable
effects must have been long accumulating in the interior,
before it acquires sufficient strength to overcome the resist-
ance of the superincumbent mass, and is enabled, for example,
to raise new islands above the surface of the ocean, by
breaking through granular rocks and conglomerates (strata of
tufa containing marine plants). The strongly compressed
vapours escape through the crater of elevation, but the great
upheaved mass again falls back, and recloses the opening
thus momentarily produced by a vast effort. No volcano
could in such case be formed." (212)
A volcano, properly so called, exists only where a per-
manent communication is established between the interior of
the earth and the atmosphere : the reaction of the interior
upon the surface is in such case continued during long
periods of time, and although interrupted for centuries, as
in the case of Vesuvius (213), it may afterwards be re-
newed with fresh energy. In the time of Nero there was
a disposition to class Mount Etna amongst the burning
mountains which 'were gradually becoming extinct; (214)
and at a still later epoch JUlian even affirmed that the
summit of the mountain was subsiding, that mariners could
no longer discern it at so great a distance from the shore as
formerly. (215) Where traces of the first eruption exist, — or
where, if I may so express myself, the primitive scaffolding
is still preserved entire, — the volcano rises from the middle
of the crater of elevation, and the isolated cone is surrounded
by an amphitheatre of lofty precipices, composed of greatly
216 REACTION OF THE INTERIOR OF THE EARTH
inclined strata : but frequently no trace of this circular ram-
part can be perceived ; and the volcano, which is not always
of a conical form, rises immediately from the table land like
the ridge-shaped volcano of Pichincha, at the foot of which
the town of Quito is built.
As the nature of rocks, or the mixture or association
of simple minerals which unite to form granite, gneiss, and
mica slate, trachyte, basalt and dolerite, is wholly indepen*
dent of our present climates, and is the same in all latitudes
and all regions of the earth; so also we see that every,
where in inorganic nature the same laws regulate the super-
position of the strata composing the crust of the globe, their
mutual penetrations, and their elevation by the agency of
elastic forces. In volcanoes especially, the identity of form
and structure is peculiarly striking. The navigator amongst
islands of remote seas, where new stars replace those on
which he has been accustomed to gaze, and where he finds
himself surrounded by palms and other unfamiliar forms of
an exotic flora, yet recognizes in the features of inorganic
nature which characterise the landscape, the forms of
Vesuvius, of the dome-shaped summits of Auvergne, of
the craters of elevation of the Canaries and the Azores, and
of the fissures^pf eruption of Iceland. The analogies thus
noticed receive a still wider generalization when we view the
attendant satellite of our planet. The maps of the moon,
which have been traced by the aid of powerful telescopes,
exhibit to us a surface devoid of air and water, abounding in
vast craters of elevation surrounding or supporting conical
eminences ; thus clearly evidencing the effects of the reaction
of the interior of the moon upon its exterior ; a reaction fa-
voured by the feebler influence of gravitation at the surface.
ON ITS EXTERIOR. VOLCANOES. 217
Although volcanoes are justly termed in many languages
w fire-emitting mountains/' they are not formed by the
gradual accumulation of erupted streams of lava ; they ap-
pear, on the contrary, to originate generally in a sudden eleva-
tion of masses of trachyte or augitic rock in a softened state.
The degree of intensity of the upheaving force is shewn by
the height of the volcano, which varies from that of a mere hill
such as the volcano of Cosima, one of the Japanese Kurile
islands, to that of a cone of above 18000 feet of elevation.
It has appeared to me that the height of volcanoes exercises a
great influence on the frequency of eruptions, which are far more
numerous in the lower than in loftier volcanoes. As instances
I may place in a series, — Stromboli (2175 Trench, or 2318
English feet) : Guacamayo, in the province of Quiros, whence
detonations are heard almost daily; (I have often heard
them myself at Chillo, near Quito, at a distance of 88 miles:)
Vesuvius (3637 French, or 3876 English feet) : Etna
(10200 French, or 10870 English feet) : the Peak of
Teneriffe (31424 French, or 12175 English feet): and
Cotopaxi (17892 French, or 19070 English feet). If we
suppose the seat of action to be at an equal depth below
the general surface of the earth in the case of all these
volcanoes, it must require a greater force to raise the
molten masses in the case of the higher mountains. It is
not therefore surprising that the one whose elevation is
least considerable, Stromboli (Strongyle), should have been
in a state of constant activity from the Homeric times,
and should still serve as a flaming beacon to mariners who
navigate the Tyrrhenian Sea, whilst the loftier volcanoes are
characterised by longer intervals of repose. Thus also we see
the eruptions of most of the colossal summits which crown
£18 REACTION OF THE INTERIOR OF THE EARTH
the chain of the Andes separated by intervals of almost a
century. To this law I long since called attention ;
and where exceptions occur, they may perhaps be explained
by the channels of communication between the volcanic
seat of action and the crater of eruption not being in all
cases alike permanently free; since this channel may be
temporarily obstructed in some volcanoes of moderate eleva-
tion, so that eruptions may become more rare, without
any immediate prospect of their absolute extinction.
These considerations, respecting the relation of the height
of volcanoes to the frequency of their eruptions, naturally
conduct us to an examination of the causes which determine
the place at which the lava issues from the mountain. In
many volcanoes eruptions from the crater are extremely rare;
they more often take place (as was remarked in the case of
Etna in the sixteenth century by the celebrated historian
Bembo (216), when a youth), from lateral openings formed in
those parts of the walls of the upheaved mountain, which,
from their nature and shape, may offer the least resistance.
Sometimes "cones of eruption" rise over these lateral
fissures ; and in this case the larger cones, erroneously
denominated "new volcanoes/' are ranged in rows, in-
dicating the line of fissure, which is speedily reclosed;
while the smaller cones, which are shaped like bells
or bee-hives, form numerous crowded groups, which cover
large spaces of ground. To the latter class belong the
"hornitos de Jorullo" (21?) and the cones of eruption of
Vesuvius in October 1822, those of the volcano of Awatscha
according to Postels, and of the lava field described by
Ennan, near the Baidar mountains, in the peninsula of
Kamtschatka.
ON ITS EXTERIOR. VOLCANOES. 219
Where volcanoes are not isolated in the midst of
plains, but are surrounded, as in the double chain of the
Andes of Quito, by a table land from nine to twelve thou-
sand feet high, this circumstance may very probably
account for the non-production of streams of lava during
the most dreadful eruptions of ignited scorise, which are some-
times accompanied by detonations heard at distances of more
than four hundred miles. (218) Such are the volcanoes of
Popayan, of the table land of los Pastes, and of the Andes
of Quito; the volcano of Antisana may possibly form an
exception.
The height of the cone of cinders, and the magnitude and
form of the crater, which are the principal elements of the
individual character of volcanoes, are independent of the
dimensions of the mountain itself. In Vesuvius, which is
only a third of the height of the Peak of Teneriffe, the cone
of ashes rises to a third of the height of the whole mountain,
while the cone of the Peak amounts to only l-22d part of
its altitude ; in the case of the Kucu-Pichincha, a volcano
much loftier than Teneriffe, the proportions much more
nearly resemble those of Vesuvius. Among all the volcanoes
which I have had an opportunity of seeing in both hemi-
spheres, the conical form of Cotopaxi is at once the most
regular and the most picturesque. A sudden melting of the
snow on its cone of cinders announces the near approach
of an eruption ; even before smoke is seen to ascend
through the rarefied atmosphere which surrounds the sum-
mit and the crater, the walls of the cone of cinders some-
times become glowing, and the mass of the mountain itself
then assumes an aspect of awful and portentous blackness.
The crater which, except iu very rare instances, always
220 REACTION OF THE INTERIOR OP THE EARTH
occupies the summit of the volcano, forms a deep circular
and often accessible caldron-like valley, the bottom of which
is subject to constant change. In many volcanoes the
greater or less depth of the crater is a sign of the greater or
less time elapsed since the last eruption. Long narrow
fissures from which vapours escape, or small circular hollows
filler) with substances in a state of fusion, alternately open
and close within the crater. The ground intumesces and
subsides, and mounds of scorise and cones of eruption rise
sometimes high above the surrounding wall of the crater,
giving the volcano a peculiar character, which may last for
years, until, during a new eruption, the mounds and cones
sink or otherwise disappear. The openings of such cones
of eruption, rising from the bottom of the crater, ought not to
be confounded, as they sometimes have been, with the crater
itself which incloses them. When the latter is inacces-
sible from its great depth and precipitous descent, as is the
case of Rucu-Pichincha, (14946 French feet in height), the
traveller may look down from the edge on the summits
which rise from the depth below, through the sulphureous
vapours by which the valley of the crater is partially filled.
This spectacle is a magnificent one. I have never seen
nature under an aspect more grand and wonderful than in
the view from the edge of the crater of Pichincha.. In the
interval between two eruptions, a crater may either offer to
the eye no phsenomenon whatever of incandescence, but
merely open fissures from which steam issues ; or the geo-
logist who is able to approach the cones of scorise without
danger over a soil only slightly heated, may enjoy the view
of the eruption of burning fragments which fall back on the
flanks of the mounds from whence they have issued. Each
ON ITS EXTERIOR. VOLCANOES. 221
such explosion is regularly announced by small and purely
local earthquake shocks. Sometimes lava is poured out
from the open fissures or hollows, but without making its
way beyond the sides of the crater; and when it does
break through them, the new stream of molten rock
usually finds a course which does not prevent the great
crater-valley itself from being accessible even during such
minor eruptions. The margins of craters appear to undergo
far less variation than might have been expected; for ex-
ample, in the case of Vesuvius, Saussure's measurements
compared with mine, shew that no change beyond the limits
of observation error took place in the height of the north-
western edge of the volcano, the E-occa del Palo, in the
interval of forty-nine years, from 1773 to 1822. (9W) I
have been solicitous to give an accurate idea of the form and
normal structure of volcanoes, without which it is impos-
sible to attain a right understanding of phsenomena, which
have been long much disfigured by fanciful descriptions,
and by the equivocal and ill-defined use of the terms,
crater, cone of eruption, and volcano.
Volcanoes which, like those of the Andes, rise high above
the region of perpetual snow, present peculiar phsenomena;
the masses of snow, by their sudden melting during
eruptions, produce terrible inundations and torrents of
water, by which smoking scoriae are hurried along with
blocks of k-e ; they also exert a continued action during
the periods when the volcano is in a state of entire repose,
by infiltration into the fissures of the trachytic rocks. Ca-
vities in the declivity or at the foot of the volcano are thus
gradually converted into subterranean reservoirs of water,
with which the alpine torrents and rivulets of the highlands
222 REACTION OP THE INTERIOR OP THE EARTH
of Quito communicate by numerous narrow channels. The
fish of these rivulets multiply by preference in the obscurity
of the caverns ; and when the whole mass of the volcano is
powerfully shaken by the earthquake shocks, which, in
the Andes, always precede eruptions, these subterranean
caves are suddenly opened, and water, fishes, and tufaceous
mud, are all ejected together. It was by this singular phse-
nomenon that the inhabitants of the plains of Qui'o were
made acquainted with the little fish which they call Prena-
dilla, Pimelodes cyclopum. (22°) When, in the night of
the 19th of June, 1698, the summit of the Carguairazo
(18000 French feet in height) fell in, leaving two immense
peaks of rock as the sole remains of the wall of the crater,
masses of liquid tufa, and of argillaceous mud ( lodazales ) ,
containing dead fish, spread themselves over and rendered
sterile a space of nearly two square German miles. The
putrid fevers which seven years before prevailed in
the mountain town of Ibarra, north of Quito, were attri-
buted to the quantity of dead fish ejected in like manner
from the volcano of Imbaburu.
Water and mud, which, in the Andes, do not issue from
the crater, but from caverns in the trachitic mass of the
mountain, cannot be strictly classed among volcanic pheno-
mena, in the restricted sense of the expression. Their con-
nection with the volcanic activity of the mountain is only
indirect, as is that of the singular meteorological pheno-
menon to which, in my earlier writings, I have given the
name of " volcanic storm." The hot steam which, during
the eruption, issues from the crater and mingles with the
atmosphere, condenses as it cools, and forms a cloud sur-
rounding the column of fire and ashes, which rises to a
ON ITS EXTEKIOR. VOLCANOES. 223
height of many thousand feet. The electric tension is in-
creased by the suddenness of the condensation, and also, as
Gay-Lussac has shewn, by the formation of such an enor-
mous surface of cloud. Forked lightnings dart from the
column of ashes, and (as at the close of the eruption of
Vesuvius, near the end of the month of October 1822) the
rolling thunder of the volcanic storm is heard, and clearly
distinguished from the sounds which issue from the interior
of the volcano. We learn from Olafsen's relation, that in
Iceland (at the volcano of Katlagia, 17th October, 1755),
eleven horses and two men were killed by lightning from the
cloud of volcanic steam.
Having thus pourtrayed, as part of the general view of
nature, the structure and dynamic activity of volcanoes, we
have next to glance briefly at the diversity of their material
products. The subterranean forces dissolve old combinations,
and form new ones ; but they operate also by displacing
the otherwise unchanged substances whilst in a state of
liquefaction by heat. The greater or less pressure under
which the solidification either of liquid or of merely softened
substances takes place, appears to be the principal cause of
the difference between " plutonic" and " volcanic" rocks.
The molten rock which has issued in a distinct current
from a volcanic opening is called lava; and where such
currents meet, and are impeded in their course by opposing
obstacles, they spread out in breadth, and cover large areas,
in which they solidify in superposed strata. These few
sentences contain all that can be affirmed generally respect-
ing the products of volcanic activity.
Fragments of the rocks which have been broken
through by volcanic disturbance are sometimes inclosed in
VOL. i. R
REACTION OF THE INTERIOR OF THE EARTH
the igneous products. Thus I have found angular frag-
ments of feldspathic syenite imbedded in the black augitic
lava of the volcano of Jorullo, in Mexico. But the masses
of dolomite and granular limestone found in the neigh-
bourhood of Vesuvius, containing magnificent groups
of crystallized minerals (vesuvian and garnets, covered
with mionite, nepheline, and sodalite), are not substances
which have been erupted from that volcano ; et they belong
rather to a very generally distributed formation — to beds
of tufa, which are older than the elevation of the Somma
and of "Vesuvius, and were probably produced by a sub-
marine and deeply-seated volcanic action/' (221) We find
among the products of existing volcanoes five metals, iron,
copper, lead, arsenic, and selenium, the latter of which was
discovered by Stronger in the crater of Volcano. The
vapours from the small cones contain chlorides of iron,
copper, lead, and ammonia ; specular iron, (222) and common
salt, (the latter often in large quantities) are found in
cavities of recent lava currents, and in fissures in the
margin of the crater.
The mineral composition of lava differs according to the
nature of the crystalline rock of which the volcano consists,
— according to the height of the point at which the eruption
takes place (whether at the foot of the mountain or near the
crater), — and according to the degree of heat of the interior.
Vitreous volcanic rocks, obsidian, pearl stone, and pumice,
are entirely wanting in some volcanoes; in others they
proceed from the crater itself, or at least from consi-
derable depths beneath it. These important and complicated
relations can only be investigated by very exact crystallo-
graphical and chemical examination. My Siberian tra-
ON ITS EXTEUIOR. VOLCANOES. 225
veiling companion, Gustav Bose, and subsequently Her-
mann Abich, have commenced, with much ingenuity
and success, the investigation of the structure of volcanic
rocks.
The greater part of the vapour which rises from volca-
noes is pure aqueous vapour, which condenses and forms
springs, as the spring in the Island of Pantellaria, to which
the goat-herds resort for a supply of water. The current
which, on the morning of the 26th of October, 1822,
was seen to pour from the crater of Vesuvius through
a lateral opening, and was long supposed to have been boil-
ing water, appears from the careful examination of Monti-
celli, to have consisted of dry ashes, or of lava pulverised by
friction. The phenomenon of volcanic ashes, which darken
the air for hours and even for days, and in their fall cause
great damage to vineyards and olive trees by adhering
to the leaves, mark by their columnar ascent, upborne
by vapours, the termination of every great eruption. This
was the magnificent phaenomenon which, in the case of Ve-
suvius, the younger Pliny, in his celebrated letter to Corne-
lius Tacitus, compared to a lofty pine spreading out at its
summit into wide shadowing branches. The appearance of
flame, which has been described as accompanying the erup-
tions of scoriae, and the red glow of the clouds which hover
over the crater, are not certainly true flames, or to be attri-
buted to the combustion of hydrogen ; they are rather due
to reflections from the incandescent substances projected
high in air, and also to the ascending vapours illumi-
nated by the fiery sea within the crater itself. In regard to
the flames seen occasionally, as in the time of Strabo, to
issue from the deep sea during the activity of coast volca-
226 REACTION OF THE INTERIOR OP THE RAHTJI
noes, or a short time before the elevation of a volcanic
island, we can give no explanation.
When it is asked, what it is that burns in volcanoes, —
what excites the heat, fuses the earths and metals, and im-
parts to lava currents of great thickness (223) a heat which
lasts for many years, — the question assumes by implication,
that the presence of materials capable of supporting combus-
tion is indispensable in volcanoes, like the beds of coal in
subterranean fires. According to the different phases which
chemical science has passed through, bitumen, pyrites, or a
humid mixture of pulverised sulphur and iron, pyrophoric
substances, and the metals of the earths and alkalies, have
been successively assigned as the cause of active volcanic
phsenomena. Sir Humphry Davy, the great chemist to
whom we owe the knowledge of these latter most inflam-
mable metals, has himself renounced his bold chemical
hypothesis in his last work, " Consolation in travel, and last
days of a Philosopher/'' which cannot be read without a sen-
timent of melancholy. The higji mean density of the earth'
(5.44), compared with the much inferior specific gravity of
potassium (0.865), and of sodium (0.972), or of the metals
of the earths (1.2), the absence of hydrogen in gaseous
emanations from the fissures of craters, and from lava cur-
rents which have not yet cooled ; and lastly, many chemical
considerations, oppose- themselves to the earlier conjectures
of Davy and of Ampere. (224) If hydrogen were disengaged
by the eruption of lava, what prodigious quantities of that gas
must have been set free in the memorable eruption at the
foot of the Skaptar- Jokul, in Iceland, described by Macken-
zie and Soemund Magnussen, which lasted from the l|th
of June to the 3d of August, and covered very many
ON ITS EXTERIOR. VOLCANOES, 227
square miles of country with lava, which, where it met with
obstacles to its course, accumulated to a thickness of several
hundred feet. The small quantity of nitrogen emitted op-
poses similar difficulties to the hypothesis of the entrance of
atmospheric air into the crater, OL-, as it has been metapho-
rically expressed, to the breathing or inhaling of air by the
earth. An activity so general as that of volcanoes, so
deeply seated, and extending itself so widely in the interior,
oannot well have its source in chemical affinities, and in the
contact of certain substances found only in particular loca-
lities. Modern geology prefers to seek its cause in the
internal terrestrial heat, manifested in every latitude by the
increase of temperature with increasing depth, and which has
been ascribed to the supposed condition of the earth as a
body only partially cooled. If we consider volcanoes as
irregular intermitting springs, supplying in tranquil flow a
fluid mixture of oxidized metals, alkalies, and earths, which,
upheaved by the powerful expansive force of vapours, have
found a permanent outlet, — we are involuntarily reminded
how nearly the rich imagination of Plato approached to the
same view, when he attributed thermal springs and all vol-
canic phenomena to a single cause every where present in
the interior of the earth, the Pyriphleyethon, or subterra-
nean fire. (225)
The geographical distribution of volcanoes is wholly inde-
pendent of climatic relations ; they have been arranged
characteristically in two classes : " central volcanoes," and
" volcanic chains ;" the former term being applied to volca-
noes forming the centers of numerous orifices of eruption
distributed with some regularity in every direction; and
tjie latter to those which, placed at moderate distances
apart, form lines running in one direction, like chim-
228 REACTION OF THE INTERIOR OF THE EARTH
neys or vents from a long extended subterranean fis-
sure. The latter class of volcanoes, or those which form
lines, is again subdivided into those which rise as single
conical islands from the bottom of the sea, (in which case
they are usually parallel to, and at the foot of a chain of
primitive mountains), or they are elevated upon the highest
ridge of the primitive chain, of which they then form the
summits. (226) The Peak of Teneriffe, for example, is a
" central volcano ;" it is the center of the group to which
we refer the volcanic islands of Palma and Lancerote. The
grandest example of a continental volcanic "chain" is offered
by the great rampart of the Andes, extendingfrom the southern
part of Chili to the north-west coast of America, sometimes
forming a single range, sometimes divided into two or three
parallel branches, which are occasionally connected by nar-
row cross or transversal ridges. In this chain the proximity
of active volcanoes is always announced by the appearance of
certain kinds of rocks (dolerite, melaphyre, trachyte, an-
desite, and dioritic porphyry), breaking through and dividing
the primitive rocks, the transition slates and sandstones, and
the more recently formed strata. The constant recurrence
of this phenomenon led me long since to the belief that
these sporadic rocks were the seat of volcanic phenomena,
and determining conditions of volcanic eruptions. It was
at the foot of the majestic Tunguragua, near Penipe (on the
banks of the Rio Puela), that I first distinctly observed
mica schist (resting on granite) traversed by a volcanic rock.
In parts of the volcanic range of the new continent, where
the single volcanoes are nearest to each other, they shew a
certain mutual dependence and connection ; it even appears
that the volcanic activity has progressively advanced frr
centuries in certain directions, as in the province of
ON ITS EXTERIOR. VOLCANOES. 229
Quito from north to south. The seat of volcanic action ex-
tends under the whole of that elevated province ; (227) its
several channels of communication with the atmosphere being
the volcanic mountains of Pichincha, Cotopaxi, and Tungu-
ragua, which, by their grouping, as well as by their lofty
elevation and grand outlines, present the most sublime and
picturesque aspect which is anywhere concentrated within
BO small a space in a volcanic landscape. The extremities
of volcanic chains are connected with each other by sub-
terranean communications ; and this fact, which experience
has made known to us in numerous instances, reminds us of
the old and just statement of Seneca, that (t the crater is
only the issue of the deeper seated volcanic forces." (228)
The Mexican volcanoes of Orizaba, Popocatepetl, Jorullo,
and Colima, also appear to be connected with each other,
and are situated over a transverse fissure running from sea
to sea. As was first shewn by myself, (229) these moun-
tains are all situated between 18° 59' and 19° 12' of North
latitude; and in the exact line of the direction of these
volcanoes, and over the same transverse fissure, Jorullo
was suddenly elevated on the 29th of September, 1759 ;
this last mountain has only once sent forth streams of
lava, resembling in this respect Mount Epomeo in the
island of Ischia, of which likewise only a single eruption (in
1302) is recorded.
But although Jorullo, situated eighty miles from any
active volcano, is in the strictest sense a " new moun-
tain," yet its appearance must not be confounded with
that of the Monte Nuovo near Pozzuolo (19th Sep-
tember, 1538), which is rather to be classed with the
" craters of elevation." It appears, indeed, to me, to agree
better with the results of observation, if we compare the sudden
230 REACTION OP THE INTERIOR OF THE EARTH
appearance of the Mexican volcano with the volcanic elevation
of the Hill of Methone, now Methana, in the peninsula of
Trcezena, a phaenornenon of which the description by Strabo
and Pausanias led one of the Roman poets endowed with the
richest fancy to develop views strikingly accordant with those
of modern geology. " Near Troezena is a tumulus, steep and
treeless, once a plain, now a mount. The vapours, pent up in
dark caverns, in vain sought an outlet ; thus constrained,
their powerful force caused the inflated ground to swell up-
wards, like a bladder or goat-skin filled with air. The
ground thus raised still remains, but has been changed
by time into a hard rock/' (23°) Thus picturesquely, and,
as analogous phenomena justify us in believing, thus truly,
does Ovid describe the great natural phsenoinenon which
took place between Troezena and Epidaurus, 282 years
before our era ; 45 years therefore before the volcanic sepa-
ration of Thera (the island of Santorin) from Therasia.
In the same spot Eusseg'ger found intersecting veins of
trachyte.
Of all " islands of eruption," belonging to volcanic chains,
Santorin is the most important as an object of study : "it
is a complete type of islands of elevation : for more than
2000 years, or as far back as history and tradition enable
us to trace, efforts of nature to form a volcano in the middle
of the crater of elevation seem to have been perpetually going
on/' (231) Near the island of St. Michael, in the Azores,
similar insular elevations manifest themselves at almost
regularly recurring intervals of eighty or ninety years ; (232)
but in this case the bottom of the sea is not always raised
at precisely the same points. The island to which Captain
Tillard gave the name of Sabrina, appeared at a time
(30th January, 1811) when unfortunately political events
ON ITS EXTERIOR. VOLCANOES. 231
did not permit scientific institutions to give to this great
phenomenon the attention which, at a latter epoch (2d July,
1831) was devoted to the ephemeral apparition of the
igneous island of Eerdinandea, between the limestone coast
of Sciacca and the purely volcanic island of Pantellaria. (233)
The geographical distribution of the volcanoes which
have been in a state of activity within historic times, — the
great number situated on islands or on coasts, — and the re-
curring phenomena of eruptions from the bed of the sea, —
early led to a belief that volcanic activity is connected with
the vicinity of the sea, and dependent on it for its continu-
ance. " Etna and the J^olian islands have been burning for
centuries/'' says Justin, (234) (or rather Trogus Pompeius,
whom Justin follows ;) " and how could they have lasted so
long if the neighbourhood of the sea did not feed the fire ?"
Even in recent times it has been attempted to explain the
supposed necessity of the vicinity of the sea, by the hypo-
thesis of sea water penetrating to the foci of volcanic acti-
vity, or to very deep-seated strata. After comprehending
in one view all that my own observation has furnished, and
all that I can gather from facts diligently collected else-
where, it appears to me that the conclusion in this intricate
investigation must depend upon the solution of certain
questions ; we must, -for instance, first determine whether
the great mass of aqueous vapour unquestionably exhaled
by volcanoes, even when in a state of repose, be derived
from sea water impregnated with salt, or from fresh water
obtained from meteoric sources. In the next place we
must decide whether the expansive force of aqueous
vapour (which, at a depth of 88000 French feet, is equiva-
lent to 2800 atmospheres,) would be sufficient, at the dif-
ferent depths of the foci of volcanic action, to counterba-
232 REACTION OP THE INTERIOR OP THE EARTH
lance the hydrostatic pressure of the waters of the sea, and
to allow them, under certain conditions, free access to the
foci. (235) We must learn whether the presence of the metallic
chlorides, or even of marine salt in the fissures and crevices in
the sides of craters, and the frequent admixture of hydro-
chloric acid in the aqueous vapours, necessarily imply such
access of the sea water. Finally, we must inquire if the in-
activity of volcanoes (whether temporary, or final and com-
plete,) is dependent on the interruption of the channels by
which either the sea or fresh water previously penetrated ;
or if the absence of flames and of hydrogen gas (not of sul-
phuretted hydrogen which belongs rather to solfataras than
to active volcanoes,) is directly opposed to the hypothesis
which attributes their activity to the decomposition of great
masses of water. The discussion of these important physi-
cal questions does not belong to a work like the present :
but whilst on the subject of the geographical distribution of
volcanoes, it is proper to notice that all active volcanoes
are not in close proximity to the sea ; since on the new
continent, Jorullo, Popocatepetl, and the Volcano de la
Fragua, are respectively 80, 132, and 156 geographical miles
from the ocean ; and even in central Asia, a fact to which
Abel Remusat (236) first called the attention of geologists,
we find a great volcanic chain, the Thian-schan (celestial
mountains,) — to which belong the Pe-schan from whence
lava issues, the solfatara of Urum-tsi, and the still ac-
tive " fire mountain" (Ho-tscheu,) of Turfan, — almost equi-
distant from the shores of the Polar Sea and of the Indian
Ocean (1400 and 1528 miles.) Pe-schan is also fully
1360 miles from the Caspian Sea, and 172 and 208 miles
respectively from the great lakes of Issikoul andBalkasch. (237)
It is deserving of notice that, of the four great parallel
ON ITS EXTERIOR. VOLCANOES. 233
chains of mountains which traverse the Asiatic continent
from east to west, the Altai, the Thian-schan, the Kuen-
lun, and the* Himalaya, it is not the Himalaya which is
nearest to the sea, — but the two interior chains (the Thian-
schan and Kuen-lun), at distances of 1600 and 720 miles
from the sea, which have eruptive volcanoes like Etna and
Vesuvius, and issues of ammoniacal gas like the volcanoes
of Guatimala. It is impossible not to recognise currents
of lava in the descriptions given by Chinese writers of
smoke and flame bursting from the Pe-schan, accom-
panied by burning masses of stone flowing as freely as
"melted fat," and devastating the surrounding district, in
the first and seventh centuries of our era. The facts thus
brought together, and which have not perhaps been hitherto
sufficiently considered, render it at least highly probable
that the vicinity of the sea, and access of sea water to the
focus of volcanic activity, are not essential conditions of
the breaking forth of the subterranean fire ; and that, if
littoral situations favour such eruptions, it is only because
they are on the margin of the deep sea basin, of which the
bed, covered only by superincumbent water, and situated
many thousand feet lower than the elevated terra firma of
the interior of continents, offers less resistance to the sub-
terranean forces.
The present active volcanoes, of which the craters es-
lublish a communication between the interior of the
earth* and the atmosphere, have been opened at so late
an epoch, that the upper chalk strata, and all the ter-
tiary formations, were previously existing : this is evidenced
by the trachyte and the basalt which often form the sides of
the craters of elevation. Melaphyres extend to the middle
tertiary strata, having apparently been poured out also be-
REACTION OF THE INTERIOR OP THE EARTH
neath the oolite, since they traverse the bunter or variegated
sandstone. (238) We must not confound the pre sent active
craters with earlier outpourings of granite, of quartzose por-
phyry, and of euphotide, from open temporary fissures in the
old transition rocks.
The cessation of volcanic activity may be only partial,
the subterranean fire finding for itself another outlet in the
same chain of mountains ; or it may be total, as in Au-
vergne. More recent examples of the latter class are known
to have occurred within historic periods; the volcano of
Mosychlos, (™) on the island consecrated to Vulcan, of
which the " high whirling flames" were still known to So-
phocles ; and the volcano of Medina, which, according to
Burckhardt, sent forth a stream of lava as late as the 2d of
November, 1276. * Each stage of volcanic activity, from its
first excitement to its extinction, is characterised by a parti-
cular class of products : first, by ignited scoriae, by currents
of lava consisting of trachyte, pyroxene, and obsidian, and
by rapilli and tufaceous ashes, accompanied by an abun-
dant disengagement of steam, usually quite pure : at a later
period the volcano becomes a solfatara, where aqueous
vapours are emitted mixed with sulphuretted hydrogen and
carbonic acid gases : and lastly, the crater becomes entirely
cooled, and carbonic acid exhalations only proceed from it.-
There is an extraordinary class of volcanoes (such as the
Galungung, in the island of Java), which do not emit lavas,
but only devastating streams of boiling water, accompanied
by sulphur in combustion, and rocks reduced to the state of
dust ; (24°) but whether these present a normal condition, or
are only a certain transitory modification of volcanic processes,
must remain undecided until they are visited by geologists
skilled in the doctrines of modern chemistry.
ON ITS EXTERIOR. VOLCANOES. 235
This general description of volcanoes, — one of the most
important manifestations of the internal activity of our
planet,, — has been based in part on my own observations, but
still more,, and in its more comprehensive outlines, on the
labours of my friend, Leopold von Buch, the greatest geolo-
gist of our age, who was the first to recognise the intimate
connection of the several volcanic phsenomena, and their mu-
tual dependence. Yolcanic action, or the reaction of the in-
terior of a planet on its external crust and surface, was long
regarded as an isolated and purely local phsenomenon, and
wa§ considered solely in respect to its destructive agency ;
it is only in modern times that, greatly to the advantage of
geological science founded on physical analogies, volcanic
forces have been contemplated as formative of new
rocks, and transformative of those which were pre-
existing. We here arrive at the point I previously indi-
cated, at which a well-grounded study of volcanic ac-
tivity in its various manifestations, branches into, and con-
nects itself with the mineralogical portion of geology
(the science of the structure and succession of terrestrial
strata), and with the configuration of continents and islands
which have been elevated above the level of the sea. The
enlarged view presented by this connection of phenomena is
a result of the philosophical direction, which the more
earnest and serious study of geology has now so generally
assumed. The prosecution and improvement of the sciences
has the same tendency as political and social improvements,
to bring together and unite that which had long been
divided.
If instead of arranging rocks, according to their differences
236 GEOLOGICAL DESCRIPTION OP THE EARTH*S CRUST.
of form and superposition, into stratified and unstratified,
schistose and compact, normal and abnormal, we trace out
and study the phenomena of formation and transformation
which are still going on before our eyes, they may be distri-
buted into the four following classes, according to their
mode of origin : —
1. Erupted rocks, which have issued from the interior
of the earth, either by volcanic action in a state of fusion,
or by plutonic action in a more or less softened state.
2. Sedimentary rocks, precipitated or deposited from
liquids in which their particles were held in solution
or suspended ; these form the greater part of the secondary
and tertiary groups.
3. Transformed or metamorphic rocks, in whicn the
texture and mode of stratification have been altered, either
by the contact or proximity of an erupted plutonic or vol-
canic rock (endogenous rocks),2*1 or, as is more frequently the
case, by the action of vapours and sublimations, (242) which
accompany the issue of certain masses in a state of igneous
liquefaction.
4s. Conglomerates, coarse or fine-grained sandstones or
breccias, consisting of mechanically divided fragments of
the three preceding classes.
The production of these four kinds of rocks, as still
going on before our eyes — by the pouring forth of vol-
canic masses in streams of lava, — by the influence of these
masses on 'rocks previously hardened, — by mechanical se-
paration or chemical precipitation from liquids charged
with carbonic acid, — and by the cementation of the detritus
of rocks of every kind ; — may be regarded as presenting
FUNDAMENTAL CLASSES OF EOCKS. 237
only a faintly reflected image of that which took place in
the early chaotic period of more energetic activity, under
very different conditions of pressure, and a far higher tem-
perature of the more extended and vapour-loaded atmo-
sphere, as well as of the crust of the earth. The vast fissures
which were then open in the solid portions of the crust have
been since closed by the elevation of mountain chains pro-
truded through them, or filled up by veins of granite, porphyry,
basalt, and melaphyre. At the present period of the globe
there remain only, on an extent of the size of Europe, four
volcanoes, or openings through which ignited masses may
issue ; whereas formerly, channels of communication between
the molten interior and the atmosphere existed at almost
every part of the thinner and much fissured crust of the globe.
Gaseous exhalations, rising from very unequal depths, and
bringing with them different chemical substances, gave
great activity to the processes of plutonic formation and of
metamorphic action. In like manner, in the case of sedi-
mentary formations, the beds of travertin which are now in
daily course of deposition from cold and warm springs and
river water, near Rome, and near Hobarton in Yan Diemen
Island, afford but a feeble representation of the formation
of the earlier mineral strata. On the coasts of Sicily and of
the Island of Ascension, and in King George's Sound in
Australia, small banks of limestone, of \vhich some parts are
scarcely inferior in hardness to Carrara marble, (243) are in
course of gradual formation by our present seas, under the
influence of processes which have not' yet been sufficiently
investigated, by means of precipitation, accumulation by
drift, and cementation. On the coasts of the West India
Islands, these formations of the present ocean contain pot-
tery, instruments of human art and industry ; and, at Gua-
daloupe, even human skeletons of the Carib race. The
negroes of the French colonies call these banks " Maconne-
bon-Dieu." (244) In Lancerote, one of the Canary Islands,
a small bank of oolite, which, notwithstanding its recent
formation, resembles the Jura limestone, has been recog-
nised as a product of the sea and of tempests. (245)
The composite rocks are determinate associations of certain
simple minerals, such as feldspar, mica, silex, augite, and
nepheline. Rocks very similar to those of the earlier periods,
and composed of the same elements, but differently grouped,
are now produced under our eyes by volcanic processes.
"We have already remarked, (246) that the mineralogical cha-
racters of rocks are wholly independent of their geographical
distribution ; and the geologist recognises with surprise, in
opposite hemispheres, and in very dissimilar climates, the
familiar aspect, and the repetition, even in the most minute
details, of the successive members of the silurian series, and
the precisely similar effects of contact with erupted augitic
masses.
We will now take a nearer view of the four fundamental
classes of rocks, which correspond to the four phases or
modes of formation presented by the stratified and unstrati-
fied portions of the earth's crust : and, first, in the endoge-
nous or erupted rocks, designated by some modem geolo-
gists by the terms massive and abnormal rocks, we distin-
guish as immediate products of the active subterranean
forces, the following principal groups : —
1. Granite and syenite, of very different ages. The
granite is often the more recent rock, traversing the
ENDOGENOUS OR ERUPTED ROCKS. 239
syenite. (247) Where granite is found in large insulated
masses,, having a slightly vaulted ellipsoidal form, whether
it be in the Hartz district, in Mysore, or in Lower
Peru, it is surmounted by a kind of crust divided
into blocks. These " seas of rocks," as they are
sometimes called, are probably occasioned by a con-
traction of the distended surface of the granite when
first upheaved. (248) In Northern Asia, on the ro-
mantic shores of Lake Kolivan on the north-western
slope of the Altai, (249) as well as at las Trin-
cheras (25°) on the declivity of the maritime chain of
Caraccas, I have seen divisions in the granite, which were
probably caused by similar contractions, but which ap-
peared to penetrate deep below the surface. Farther to
the south of Lake Kolivan, towards the boundary of the
Chinese province of Ili (between Bucktarminsk and the
river Narym), the appearance of the erupted rocks, in
which there is no trace of gneiss, is more remarkable
than I had ever before seen in any part of the globe.
The granite, which always scales at the surface, and is
characterised by tabular divisions, rises, on the steppe, in
small hemispherical hillocks of six or eight feet in height^
and sometimes, like basalt, in small mounds with narrow
streams on opposite sides of their base. (251) At the cata-
racts of the Orinoco, as in the Fichtelgebirge in Bavaria,
—and in Gallicia, as on the Pappagallo between the high
lands of Mexico and the Pacific, — I have seen large flat-
tened globes of granite, which could be separated into
concentric layers like certain basalts. In the valley of
the Irtysch, between Buchtarminsk and Ustkamenogorsk,
VOL. I. S
240 GEOLOGICAL DESCRIPTION* OF THE EARTH*S CRUST.
granite covers transition slate for a space of four
and penetrates it from above downwards in narrow
branching veins, having wedge-shaped terminations. (252)
These details have been introduced for the purpose of
indicating by examples the character of erupted rocks, as
shewn in a rock most generally distributed throughout
all parts of the earth. As granite covers argillaceous
schists in Siberia, and in the Departement de Pinisterre
(He de Mihau), so does it cover oolitic limestone in
the mountains of Oisons (Fermonts), and syenite and
chalk in Saxony near Weinbohla. (253) At Mursinsk,
in the Oural, the granite is porous, and as in the later
volcanic rocks, the cavities are filled with magnificent
crystals, particularly beryls and topazes.
2. Quartzose porphyry, frequently imbedded as veing
in other rocks. The matrix is usually a fine-grained mix-
ture of the same elements as those which form the larger
disseminated crystals. In granitic porphyry, which is
very poor in quartz, the feldspathic base is almost
granular, and laminated. (254)
3. Greenstone, Diorite, granular mixtures of white
albite and dark-green hornblende, forming dioritic por-
phyry when the crystals of albite are disseminated in a
compact paste. The greenstones, either pure, or, as in the
Fichtelgebirge, containing laminae of diallage, and passing
into serpentine, have sometimes penetrated, in the form of
beds, between ancient strata of green argillaceous schist;
but they more often traverse the rock in the form of
veins, or appear as domes of greenstone, analogous to
domes of basalt and of porphyry. (255)
ENDOGENOUS OR ERUPTED ROCKS. 241
Hi/per sthene rock is a granular mixture of labrador
feldspar, and hypersthene.
Euphotide and serpentine/ containing sometimes in-
stead of diallage crystals of augite and uralite, and thus
becoming nearly allied to a more abundant, and, I might
almost say, a more active eruptive rock, viz. augitic
porphyry. (256)
Malaphyre, and the porphyries containing crystals of
augite, uralite, and oligoklas ; to which latter species the
celebrated verd-autique belongs.
Basalt, with oliviue and other constituents which
gelatinise with acids, phonolite, porphyry-slate, trachyte,
and dolerite : the first of these rocks is partially, and the
second always, divided into tabular laminee, which gives
to them an appearance of stratification, even when cover-
ing a large extent. Mesotype and nepheline form, accord-
ing to Girard, an important part in the composition and
internal texture of basalts. Nepheline forming a con-
stituent of basalt remind j the geologist of the miascite
of the Ilmen mountains in the Ural (257), a mineral
which has been confounded with granite, and which
sometimes contains zircon; it also reminds him of the
pyroxenic nepheline discovered by Gumprecht near Lobau
and Chemnitz.
To the second or sedimentary class of rocks belongs the
greater part of the formations comprehended under the old
systematic but incorrect denomination of floetz rocks, or of
transition, secondary, and tertiary formations. If earth-
quakes and erupted rocks had not exerted an unheaving and
disturbing influence on the sedimentary formations, the
242 GEOLOGICAL DESCRIPTION OF THE EARTH*S CRUST.
surface of our planet would have consisted of horizontal
strata, regularly superimposed one over the other. Deprived
of our mountain chains, — the declivities of which may be
said to reflect, in the picturesque gradation of the different
vegetable forms with which they are clothed, the scale of
diminishing atmospheric temperature from their base to their
summits, — the only features of variety in the disposition of
the ground would have been the occasional presence of
ravines hollowed out by the feeble erosive force of currents
of fresh water, and slight eminences of transported detritus
due to the same cause. Prom pole to pole, under every
region, continents would have presented to the eye the
dreary uniformity of the llanos of South America, or the
steppes of Northern Asia ; the vault of heaven would have
everywhere appeared to rest on the unbroken plain, and the
stars to rise and set as on the horizon of the ocean. Such
a state of things, however, cannot have had a long duration
even in the primitive world, for at all periods subterranean
forces have exerted their modifying influence.
Sedimentary strata have been either precipitated or depo-
sited from liquids, according as the materials which con-
stitute them were chemically dissolved or mechanically
suspended. But when earths that have been dissolved in
fluids containing carbonic acid are separated, their descent
during precipitation and accumulation in strata require to be
regarded as a true mechanical process; a consideration of some
importance in respect to the envelopment of organic bodies in
fossiliferpus limestone. The oldest sedimentary strata of the
transition and secondary series were probably formed from
water of high temperature, at a time when the heat of the
upper surface of the globe was still very considerable. In
EXOGENOUS OR- SEDIMENTARY ROCKS. 243
this point of view a plutonic influence may be said to have
acted in a certain sense even on the sedimentary strata,
especially on the older ones ; but these strata appear to have
hardened and to have acquired their schistose structure
under great pressure, whereas the rocks which issued from
the interior (granite, porphyry, and basalt) solidified by
cooling. As the heat of the waters gradually diminished,
they could absorb a larger portion of the carbonic acid gas
existing in the atmosphere, and were thus fitted for holding
a larger quantity of lime in solution.
The sedimentary rocks, excluding all other exogenous
purely mechanical deposits of sand or detritus, are as
follow : —
Argillaceous schist of the lower and upper transition
series, comprehending the silurian and devonian forma-
tions, from the lower silurian strata, once termed cambrian,
to the upper strata of the old red sandstone or devonian
period, immediately below the mountain limestone.
Carboniferous deposits.
Limestones included in the transition and car-
boniferous formations, the zechstein, the muschelkalk,
the Jura oolitic limestone, the chalk, and various beds
of the tertiary period which cannot be classed amongst
the sandstones or conglomerates.
Travertin, including fresh- water lime-stone, and sili-
ceous concretions from hot springs, formations which
have not been produced under the pressure of a great
body of sea water, but almost at the surface, in shallow
marshes and streams.
Infusorial masses, a geological phenomenon of great
importance, as it has revealed to us the influence which
organic life has exercised on the formation of a part of
24i4f GEOLOGICAL DESCRIPTION OF THE EARTHS CRUST.
the solid crust of the earth ; the existence of such masses
is a very recent discovery, for which science is indebted
to my distinguished friend and travelling companion
Ehrenberg.
| If in this short but general review of the mineralogical
constituents of the crust of the earth, I do not place imme-
diately after the simple sedimentary rocks, those conglome-
rates and sandstones, which are also partially sedimentary
deposits, and which alternate with argillaceous schists and
chalk in the secondary and older formations, — it is only
because these conglomerates and sandstones are not composed
solely of the debris of eruptive and sedimentary rocks, but
contain also the detritus of gneiss, mica slate, and other
metamorphic masses. The obscure process of metamorphism,
and the influence it exerts, should therefore form the third
class of fundamental rocks.
I have already had occasion to remark that the endogenous
; or erupted rocks (granite, porphyry, and melaphyre), not
only act dynamically, shaking, elevating, inclining, and late-
rally displacing the superincumbent strata, but that they also
modify the chemical combinations of their elements, and the
nature of their internal structure : thus forming new kinds
of rocks, of which the gneiss, mica slate, and granular or
saccharoidal limestone (Carrara and Parian marble), may be
cited as examples. The schists of the silurian or devonian
periods, the belemnitic limestone of the Tarantaise, the dull
grey calcareous sandstone, containing fucoids of the northern
Apennines (inacigno\ often assume in their altered state a
new and brilliant appearance, which renders their recognition
difficult. The metamorphic theory has been established by
following step by step the successive phases of transforma-
METAMOEPHIC RCCKS. 245
tion, and by bringing to the aid of inductive conclusions,
direct chemical experiments on the effects of different
degrees of fusion and pressure, and different rates of
cooling. When the study of chemical combinations is pur-
sued under the guidance of leading ideas, (258) a bright light
may be thrown on the wide field of geology, and on the
operations of the great laboratory of nature, in which sub-
terranean forces have formed and modified the terrestrial
strata. But to avoid being misled by apparent analogies to
entertain too narrow a view of the processes of nature, the
philosophical inquirer must ever keep in view the compli-
cated conditions, and the unknown intensity, of the forces
which, in the primitive world, modified the reciprocal action
of the several substances. It cannot, however, be doubted
that the elementary substances always obeyed the same laws
of affinity ; and I am fully persuaded, that where apparent
contradictions are met with, the chemist will generally suc-
ceed in explaining them, by ascending in thought to the
primary conditions of nature, which cannot be identically
reproduced in his experimental researches.
Observations made with great care, and over considerable
tracts of country, shew that erupted rocks have acted in a
regular and systematic manner. In parts of the globe most
distant from each other, (259) granite, basalt, and diorite, are
seen to have exerted, even in the minutest details, a perfectly
similar metamorphic action on the argillaceous schists, the
compact limestone, and the grains of quartz in sandstone.
But whilst the same kind of erupted rock exercises almost
every where the same kind of action, the different rocka
belonging to this class, present, in this respect, very
different characters. The effects of intense heat are indeed
246
apparent in all the phenomena; but the degree of fluidity
has varied greatly in all of them from the granite to the
basalt: and at different geological epochs, eruptions of
granite, basalt, greenstone, porphyry, and serpentine, have
been accompanied by the issue of different substances in a
state of vapour. According to the views of modern geology,
the metamorphism of rocks is not confined to the effects of
simple contact, or of the juxta-position of two kinds of rock;
but it comprehends all the phsenomena that have accom-
panied the issuing forth of a particular erupted mass ; and
even where there has been no immediate contact, the mere
proximity of such a mass has frequently sufficed to produce
modifications in the cohesion of the particles and texture of
the rock, in the proportions of the silicious ingredients, and
in the forms of crystallization of the pre-existing rocks.
All eruptive rocks penetrate as veins into sedimentary
strata, or into other previously existing endogenous masses ;
but there is an essential difference in this respect between
plutonic rocks, — granites, porphyries, and serpentines, —
and those called volcanic in the most restricted sense, — tra-
chytes, basalts, and lavas. The rocks produced by the
still existing volcanic activity present themselves in narrow
streams, and do not form beds of any considerable breadth,
except where several meet together and unite in the same
basin. Where it has been possible to trace basaltic erup*
tions to great depths, they have always been found to termi-
nate in slender threads, of which examples may be seen in
three places in Germany, — near Marksuhl, eight miles
from Eisenach, — near Eschwege, on the banks of the Werra,
— and at the Druidical stone on the Hollert road (Siegen),
In these cases, the basalt, injected through narrow orifices,
METAMORPHIC ROCKS. 247
has traversed the banter sandstone and greywacke slate, and
has spread itself out, in the form of a cup ; sometimes form-
ing groups of columns, and sometimes divided into thin
laminse. This, however, is not the case with granite, syenite,
porphyritic quartz, serpentine, and the whole series of
unstratified rocks, to which, by a predilection for mytho-
logical nomenclature, the term plutonic has been applied.
With the exception of occasional veins, all these rocks have
been forced up in a semi-fluid or pasty condition through
large fissures and wide gorges, instead of gushing in a
liquid stream from small orifices ; and they are never found
in narrow streams like lava, but in extensive masses. (26°)
Some groups of dolorites and trachytes shew traces of a
degree of fluidity resembling that of basalt; others, form-
ing vast craterless domes, appear to have been elevated
in a simply softened state , others again, like the trachytes
of the Andes, in which I have often remarked a striking
analogy to the greenstone and syenitic porphyries (argentife-
rous and then without quartz), are found in beds like
granite and quartzose porphyry.
Direct experiments (261j on the alterations which the
texture and chemical constitution of rocks undergo from
the action o£ heat have shewn, that volcanic masses (diorite,
augitic porphyry, basalt, and the lava of Etna) give different
products according to the pressures under which they are
melted and the rate at which they are cooled; if
the cooling has been rapid, they form a black glass, homo-
geneous in the fracture ; if slow, a stony mass, of granular
or crystalline structure; and in this latter case crystals
are formed in cavities, and even in the body of the
mass in which they are imbedded. The same materials also
248 GEOLOGICAL DESCRIPTION OF THE EARTIl's CRUST.
yield products very dissimilar in appearance, a fact of (lie
highest importance in the study of eruptive rocks, and the
transformations which they occasion ; as, for example, car-
bonate of lime, melted nnder high pressure, does not part
with its carbonic acid, but becomes when cooled granular
limestone or saccharoidal marble when the operation is
performed by the dry method, while in the humid pro-
cess calcareous spar is produced with a less, and arrago-
nite with a greater, degree of heat. (262) The mode of
aggregation of the particles which unite in the act of crys-
tallization, and consequently the form of the crystal itself, are
also modified by differences of temperature ; (263) and even
where the body has not been in a state of fluidity, the parti-
cles, under particular circumstances, may undergo a new ar-
rangement, manifested by different optical properties. (264)
The phsenomena presented by devitrification, — by the produc-
tion of steel by casting or cementation, — by the passage from
the fibrous to the granular texture of iron, occasioned by in-
creased temperature, (265) and possibly by the influence of
the long-continued repetition of slight concussions, — may
elucidate the geological study of metamorphism. Heat some-
times elicits opposite effects in crystalline bodies ; for Mit-
scherlicfr's beautiful experiments have established the fact,
that without altering its condition of aggregation, calcareous
spar, under certain conditions of temperature, expands in
one of its axial directions while it contracts in the other. (266)
Passing from these general considerations to particular
examples, we may mention the case of schist converted by
the vicinity of plutonic rocks into roofing slate of a deep
blue colour and glistening appearance; the planes of
stratification are intersected by other divisional planes, often
METAMORPHIC EOCKS. 249
almost at right angles with those of stratification, indicating
an action posterior to the alteration of the schist. (267) The
silicic acid which has penetrated into the mass causes it
to be traversed by veins of quartz, and transforms it in part
into whetstone and siliceous schist; the latter sometimes
containing carbon, and then perhaps capable of pro-
ducing galvanic phenomena. The most highly silicified
rocks of this kind are known as ribbon jasper, (26s) a
material valuable in the arts, produced in the Oaral moun-
tains by the eruption and contact of augitic porphyry (as at
Orsk), of dioritic porphyry (as at Aufschkul), or of a
rounded mass of hypersthene rock (as at Bogoslowsk).
In the island of Elba (at Monte Serrato), according to Fried-
rich Hoffman, and in Tuscany, according to Alexandre
Brongniart, the ribbon jasper is formed by contact with
euphotide and serpentine.
Sometimes (as observed by Gustav Rose and myself in
the Altai, within the fortress of Buchtarminsk), (269) the
contact and plutonic action of granite have rendered argil-
laceous schists granular, and transformed the rock into a mass
resembling granite itself, consisting of a mixture of feldspar
and mica, in which larger laminae of mica are found im-
bedded. (27o) We are told by Leopold von Buch, ( ' that all
the gneiss between the Icy Sea and the Gulf of Finland has
been produced by the metamorphic action of granite upon
the silurian strata. In the Alps near the St. Gothard,
calcareous marl has been similarly changed by the influence
of granite, first into mica slate, and subsequently into
gneiss/' (271) Similar phsenomena of gneiss and mica slate
formed under the influence of granite present themselves
in the oolitic group of the Tarantaise, (272) in which
250 GEOLOGICAL DESCRIPTION OP THE EARTHS CRUST.
belemnites are found in rocks which have already in great
measure assumed the character of mica slate, — in the
schistose group of the western part of the island of Elba,
not far from Cape Calamita, — and in the Fichtelgebirge
near Bai'reuth, between Lomitz and Markleiten. (273)
I have already alluded to the jasper employed in the arts,
which the ancients could not obtain in large masses, (274)
and have described it as produced by the volcanic action
of augijic porphyry; there is also another material of
which ancient art made the noblest and most extensive
use, i. e. granular or saccharoidal marble, which is to be
regarded as a sedimentary rock altered by terrestrial heat
and the vicinity of erupted rocks. This assertion is
justified by a careful observation of the phenomena which
result from the contact of igneous rocks, and by the
remarkable experiments made by Sir James Hall on the
fusion of mineral substances. These experiments, made
more than half a century ago, together with the atten-
tive study of the phenomena 01 granitic veins, have
contributed in a very high degree to the recent pro-
gress of geological science. Sometimes the metamorphic
action of the erupted rock extends only to a very small
distance from the surface of contact, and produces a partial
transformation, or a sort of penumbra, as in the chalk of
Belfast in Ireland traversed by veins of basalt, and as in the
compact calcareous beds, partially inflected by the contact
of syenitic granite, near the bridge of Boseampo, and at the
cascade of Canzocoli in the Tyrol, brought into notice by
Count Marsari Pencati. (275) Another mode of transfor-
mation is, when the whole of the beds of compact limestone
become granular by the action of granite, syenite, or dioritic
porphyry. (276)
METAMORPHIC ROCKS. 251
Let me here make a special mention of the Parian
and Carrara marbles, to which the noblest works of
sculpture have given such celebrity, and which were so long
regarded in our geological collections as the types of primi- •
tive limestone. The action of granite has been exerted
sometimes by immediate contact, as in the Pyrenees ; (277)
sometimes through intermediate beds of gneiss or of mica
slate, as in Greece, and the islands of the ^Egean
Sea. In both cases the transformation of the calcareous
rock has been cotemporaneous with the granite, but the
process has been different. It has been remarked that in
Attica, in the island of Euboea, and in the Peloponnesus,
" the limestone superposed on mica slate is more beautiful and
more crystalline, as the mica slate is most pure, or least argil-
laceous," and it is known that mica slate and becta of gneiss
shew themselves at many pcSts beneath the surface m Paros
and Antiparos.(278) Xenophanes of Colophon (who supposed
the whole surface of the earth to have been originally covered
by the sea), remarked, in a notice preserved by Origen, (279)
that marine fossils had been found in the quarries of Syra-
cuse, and the impression of a small fish (a sardine) at the
bottom of that of Paros : supposing the latter statement to
have been correct, we might infer the presence of a fossiliferous
bed but partially metamorphosed. The Carrara (Luna) marble,
which, from the Augustan era, and even from an earlier period,
has afforded the principal supply of statuary marble, and will
probably continue to do so unless the quarries of Paros are
reopened, is a bed, altered by plutonic action^ of the same
calcareous sandstone (macigno), which in the insulated Alp
of Apuana, shews itself between micaceous and talcose
schists. (28°) A very different origin has, indeed, been
assigned for marble in some other localities; and whether in
252 GEOLOGICAL DESCRIPTION OF THE EAIITH'S CRUST.
some cases granular limestone may not have been formed
in the interior, and raised to the surface by gneiss and
syenite, (281) where it occupies fissures, as at Auerbach or
in the Bergstrasse, is a question on which I do not
venture to express an opinion, because I have not personally
visited the localities.
The most remarkable instance of metamorphism produced
by erupted rocks on compact calcareous strata, is that which
Leopold von Buch has pointed out in masses of dolomite,
especially on the southern Tyrol, and on the Italian declivity
of the Alps. ' The alteration of the limestone appears to
have been effected by means of fissures traversing it in every
direction ; the cavities are everywhere covered with rhorn-
boidal crystals of magnesia, and the whole formation con-
sists of a granular agglomeration of crystals of dolomite,
without any trace of the original stratification, or of the
fossils which were previously contained in it. Laminae of talc
are partially disseminated in the new rock, and it is interspersed
with masses of serpentine. In the valley of the Passa
the dolomite rises perpendicularly in smooth walls of daz-
zling whiteness to a height of several thousand feet. It
forms groups of numerous sharply-pointed conical moun-
tains, clustered but separate. „ These features recal the
lovely mountain landscape with which the imagination of
Leonardo da Vinci has adorned the background of the por-
trait of Mona Lisa.
The geological phsenomena which we are here describing,
and which interest both the imagination and the intellect,
Result from the action of augitic porphyry, which has ele-
vated, shattered, and transformed the beds which are above
it. (282) The illustrious geologist who first brought into
METAMORPHIC EOCKS. 253
notice the conversion of limestone into dolomite, does not
attribute it to the introduction of a certain portion of talc
derived from the black porphyry, but considers it a modifi-
cation of the limestone, contemporaneous with the projection
of the erupted rock through wide fissures filled with va-
pours. But in certain localities, beds of dolomite are found
interposed between limestone strata, and it is yet to be ex-
plained how the transformation can have taken place without
the presence of an erupted rock, and where we are to look
for the concealed channels of the plutonic action. We
ought not to resort, however, even in this case, to the old
Eoman adage, "that much that is alike in nature has
been formed in different ways :" since over widely ex-
tended parts of the earth, we have seen two phenomena
associated, — the protrusion of a certain igneous rock, —
and the transformation of compact limestone into a
crystalline mass possessing new chemical properties, — we
may well suppose that, in the few cases in which the latter
phenomenon alone is visible, future observation will remove
the difficulty, and will shew that the apparent anomalies
are due to the conditions under which the general causes of
metamorphism have acted in the particular cases. We can-
not doubt the volcanic nature and igneous fluidity of basalt,
because some rare instances occur ot basaltic dykes tra-
versing a bed of coal, without reducing it to charcoal, —
of sandstone without producing the usual effect of heat, —
or of chalk without converting it into granular marble. If
we have, as yet obtained only an imperfect light to guide
us in the obscure domain of mineral formations, it would
surely be unwise to abandon it, because there are some
points in the liistory of the transformation of rocks, and
254 GEOLOGICAL DESCRIPTION OF THE EARTHS CRUST.
some difficulties connected with the interposition of beds
of altered rock between unaltered strata, which we cannot
wholly explain.
Having described the transformation of compact car-
bonate of lime into granular limestone and dolomite, we
have to notice a third mode of alteration in the same rock,
occasioned by the emission at some ancient epoch of the
vapours of sulphuric acid. The gypsum thus produced
offers analogies with beds of rock salt and sulphur (the
latter deposited from aqueous vapour charged with that
mineral) . In the lofty Cordilleras of Quindiu, far from any
volcano, I have observed deposits of sulphur in fissures in
gneiss, while in Sicily (at Cattolica near Girgenti), sulphur,
gypsum, and rock salt, are found in the most recent secon-
dary formations. (283) At the edge of the crater of Vesuvius
also I have seen fissures filled with rock salt, sometimes
in masses sufficiently considerable to occasion a contra-
band trade ; while on the northern and southern declivi-
ties of the Pyrenees, one cannot doubt the connection of
dioritic (pyroxenic?) rocks with the occurrence of dolo-
mite, gypsum, and rock salt. (284) In these phenomena
every thing indicates the action of subterranean forces on the
sedimentary strata deposited by the ancient sea.
There is much difficulty in assigning the origin of those
vast masses of pure quartz which are characteristic of the
Andes of South America. (285) In descending towards the
Pacific, from Caxamarca to Guangamarca, I have found beds
of quartz from seven to eight thousand feet in thickness,
resting sometimes on porphyry devoid of quartz, and some-
times on diorite. Can these be a metamorphosed sandstone,
such as Elie de Beaumont conjectures to be the origin of the
METAMORPHIC ROCKS. 255
beds of quartz of the Col de la Poissoniere, to the east of
Briancon ? (286) In the diamond districts of Minas Geraes
and St. Paul in Brazil, which have been recently studied
with great care by Clausen, the plutonic aetion of dioritic
veins has produced ordinary mica and specular iron in
quartzose itacolumite. The diamonds of Grammagoa are
contained in silicious beds, and are sometimes enveloped
in laminae of mica, like the garnets found in mica slate.
The most northern diamonds yet known, which have been
discovered since 1829, in 58° lat., on the European decli-
vity of the Oural, are geologically related to the black car-
boniferous dolomite of Adolphskoi, (287) and to augitie
porphyry ; but these relations have not yet been sufficiently
elucidated by exact observation.
Among the most remarkable phsenomena of contact, I
may also allude to the formation of garnets in argillaceous
schist in contact with basalt and dolerite in Northumber-
land and the Island of Anglesea, and the production of a
large quantity and variety of beautiful crystals of garnet, vesu-
vian, augite and ceylanite, at the surface of contact of erupted
and sedimentary rocks ; namely, at the junction of the
syenite of Monzon with dolomite and compact limestone. (288)
In the Island of Elba, masses of serpentine, which perhaps
nowhere present such clear evidences of their eruptive cha-
racter, have produced sublimations of specular iron, and of
red oxide of iron, in fissures of calcareous sandstone. (289)
We still see specular iron formed daily from sublimation on
the sides of open fissures in the craters, and in recent cur-
rents of lava, of the volcanoes of Stromboli, Vesuvius, and
Etna. (29°) The veins thus formed under our eyes by volcanic
forces, in rocks which have attained a certain degree of solidity,
VOL. I. T
256 GEOLOGICAL DESCRIPTION OF THE EARTHS CRUST.
teach us how, in earlier terrestrial or geological epochs,
metalliferous or mineral veins may have been produced,
wherever the crust of our planet, then thinner, and fre-
quently rent by earthquakes, was fractured and fissured in
every direction by change of volume in cooling, presenting
communications with the interior, and a means of escape for
ascending vapours and sublimations of the metals and the
earths. The arrangement of the particles in layers parallel
with the bounding surfaces of veins, — the regular repetition
of layers of the same materials on opposite parts, for example
on the walls, of veins, — and the elongated drusy cavities
occupying the middle space, often furnish direct evidence of
the plutonic act of sublimation in metalliferous veins. As
theiveins or dykes which traverse rocks are more recent
than the rocks which are traversed by them, the relative
positions of the porphyry and of the argentiferous ores
in the mines of Saxony, which are the richest and most
important in Germany, teach us that they are at least more
recent than the remains of vegetation in the coal measures
and in the lower portions of the new red sandstone (Roth-
liegendes. 291)
Our geological hypotheses of the formation of the crust
of the earth, and of the metamorphism of rocks, have
derived unexpected elucidation, from the comparison of
minerals elaborated by nature with the products of our
smelting furnaces, and from the endeavours to reproduce
the former artificially from their elements. (292) In all these ;'
operations, the same affinities which determine chemical
combinations are in action both in our laboratories and
in the bosom of the earth. Amongst the minerals
ARTIFICIAL PRODUCTION OP SIMPLE MINERALS. 257
formed artificially are the most important simple minerals
which characterise very widely distributed eruptive plu-
tonic and volcanic rocks, as well as nietamorphic rocks
altered by them ; and these have been produced in a crys-
talline state,, and with complete identity. We must dis-
tinguish, however, between minerals formed accidentally in
the scoriae, and those produced by chemical operations
purposely devised : to the first class belong feldspar, mica,
augite, olivine, blende, crystallized oxide of iron (specular
iron), octahedral magnetic oxide of iron, and metallic tita-
nium ; (293) to the second, garnet, idocrase, ruby (as hard
as the oriental ruby), olivine, and augite. (294) These mi-
nerals form the principal constituents of granite, gneiss, and
mica slate, of basalt, dolerite, and many porphyries. The
artificial production of feldspar and mica is of singular
geological importance, in reference to the theory of the
nietamorphic conversion of argillaceous schist into quartz.
We have in the schist all the elements of granite, without
even excepting potash. (295) It would not be very sur-
prising, therefore, as our ingenious geologist von Deche;*
has justly remarked, if on some occasion we were to find a
fragment of gneiss formed on the inside wall of a furnace
built of argillaceous schist and greywacke.
Having passed in review the three great classes of erupted,
sedimentary, and metamorphic rocks, we have still to notice
the fourth class, comprising conglomerates, or rocks formed
of detritus. The terms which we employ to designate this
class recal the revolutions which the crust of the earth has
undergone, as well as the cementing action which has con-
solidated, by means of the oxide of iron, or argillaceous or
calcareous pastes, the sometimes rounded, and soiretimea
253 Q30L03ICAL DESCRIPTION1 OP THE EA.RTH*S CRUST.
sharply angu.hr masses of fragments. Conglomerates and
breccias, in their widest acceptation, present the characters
of a double origin. Their mechanical constituents have
not been accumulated solely by the action of the sea,
or by streams of fresh water, and there are some of these
rocks to the formation of which the action of water has
not contributed. "When basaltic islands or trachytic
mountains have been elevated through large fissures, the
friction of the ascending masses against the sides of the
fissures has occasioned the basalt or the trachyte to be sur*
rounded by conglomerates, formed from fragments of their
own substance. ' In the sandstones of many formations, the
grains of which they are composed have been separated,
rather by the friction of erupted plutonic or volcanic rocks,
than by the erosive action of a neighbouring sea. The ex-
istence of this species of conglomerate (which is found in
immense masses in both continents), testifies the intensity of
the force with which the eruptive masses were impelled from
the interior towards the surface. The pulverized materials
must have been subsequently conveyed away by the waters,
and disseminated in the beds where they are now found." (296)
Formations of sandstone are found every where interposed
between other strata, from the lower silurian series to the
tertiary formations above the chalk. On the margins of
the vast plains of the new continent, both within and beyond
the tropics, we find these beds of sandstone extending in
long ramparts or walls, as if indicating the ancient shore
against which the billows1 of the sea once broke.
When we glance at the geographical distribution of rocks,
and at the extent which each occupies of the portion of the
crust of the earth accessible to our researches, we recognise
that the most generally prevailing chemical substance is
GENERAL CHEMICAL CONSTITUENTS OF ROCKS. 259
silica, usually opaque, and variously coloured : the sub-
stance next in abundance is carbonate of lime ; then com-
binations of silicic acid with alumina, potash, and soda,
with lime, magnesia, and oxide of iron. The substances to
which we give the generic name of rocks are definite associa-
tions of a small number of minerals, to which some other mine-
rals attach themselves as it were parasitically, but always under
definite laws. These elements are not confined to particular
rocks : thus quartz (silicic acid), feldspar, and mica, are the
substances which, in their association, essentially constitute
granite ; but they are also found in many other rock forma-
tions, either singly or two of them combined. A single ex-
ample will suffice to shew how the proportions of these
elements may vary in different rocks, and how quan-
titative relations distinguish a feldspathic from a micaceous
rock. Mitscherlich has shewn, that if we add to feldspar
three times the quantity of alumina, and one-third of the
proportion of silex which previously belonged to it, we obtain
the composition of mica. Both these minerals contain
potassium; a substance of which the existence in many
kinds of rock was no doubt anterior to vegetation.
The succession and the relative age of different forma-
tions are traced, partly by the order of superposition of sedi-
mentary strata, of metamorphic beds, and of conglomerates,
and partly by the nature of the formations which the erupted
rocks have reached or traversed, but most securely by the pre-
sence of organic remains and their diversities of structure.
The application of botanical and zoological evidence in deter-
mining the age of rocks, and in fixing points in the chro-
logy of the crust of the globe, which the genius and
260 PALAEONTOLOGY : FOSSIL ORGANIC REMAINS.
sagacity of Hooke led him to anticipate, marks one of the most
brilliant eras in the progress of modern geology, into which
paleeontological studies have, as it were, breathed new life,
investing it with fresh charms and richly varied interests.
In the fossiliferous strata are inhumed the remains of the
floras and faunas of past ages. As we descend from stratum
to stratum to study the relations of superposition, we ascend
in the order of time, and new worlds of animal and vege-
table existence present themselves to the view. Widely
extended changes of the surface of the globe, elevations of
the great mountain chains of which we are able to deter-
mine the relative age, have been accompanied by the de-
struction of existing species, and by the appearance of new
forms of organic life ; a few only of the older remaining
for a time amongst the more recent species. In our igno-
rance of the laws under which new organic forms appear from
time to time upon the surface of the globe, we employ the
expression of " new creations," when we desire to refer to
the historical phsenomena of the variations which have taken
place at intervals, in the animals and plants which have
inhabited the basins of the primitive seas and the uplifted
continents. It has sometimes happened that extinct species
have been preserved entire, even to the minutest detail of
their tissues and articulations. In the lower beds of the secon-
dary period, the lias of Lyme Hegis, a sepia has been found so
wonderfully preserved, that a part of the black fluid with wliich
the animal was provided myriads of years ago to conceal itself
from its enemies, has actually served, at the present time, to draw
its picture. (297) In other cases such traces alone remain, as
the impression which the feet of animals have left on wet sand
or mud over which they may have passed when alive, or the
PAL^OZOOLOGY : FOSSIL ANIMALS. 261
remains of their undigested food (coprolites). Some strata
furnish only the impression of a shell ; but if it be one of
a characteristic kind, (298) we are able, on its production,
to recognise the formation in which it was found, and
to state other organic remains which were buried with it.
Thus the shell brought home by the distant traveller ac-
quaints us with the geological character of the countries
which he has visited.
The analytical study of the animal and vegetable king-
doms of the primitive world has given rise to two distinct
branches of science ; one purely morphological, which oc-
cupies itself in natural and physiological descriptions., and
in the endeavour to fill up from extinct forms the chasms
which present themselves in the series of existing species ;
the other branch, more especially geological, considers the
relations of the fossil remains to the superposition and rela-
tive age of the sedimentary beds in which they are found.
The first long predominated; and the superficial manner
which then prevailed of comparing fossil and existing spe-
cies, led to errors of which traces still remain in the strange
» denominations which were given to certain natural objects.
Writers attempted to identify all extinct forms with living
species ; as, in the sixteenth century, the animals of the New
World were confounded by false analogies with those of the
Old Continent. Camper, Sommering, and Blumenbach,
were the first to enter on a more rational course, and have
the merit of having first applied the resources of compara-
tive anatomy, in a strictly scientific manner, to that part of
palaeontology (the archseology of organic life), which treats
of the bones of the larger vertebrated animals. But it is
pre-eminently to the admirable works of George Cuvier and
262 PALEONTOLOGY : FOSSIL ORGANIC REMAINS.
Alexander Brongniart, that we owe the establishment of ("he
science of fossil geology, by the successful combination of
zoological types with the order of superposition and the
relative age of strata. The oldest sedimentary strata pre-
sent to us, in the organic remains which they contain, a
variety of forms occupying very different gradations in the
scale of progressive development. Of plants, we find a
few Fuci, Lycopodiacese which were perhaps arborescent,
Equisetacese, and tropical ferns : but of animals we discover
a strange association of Crustacea (including Trilobites with
reticulated eyes), Brachiopoda (Spirifers, Orthis), elegant
Sphseronites allied to Crinoidea, (2") Orthoceratites of the
family of Cephalopoda, and numerous corals ; and, mingled
with these animals of inferior order, we already find in the
upper beds of the silurian system fish of singular form.
The family of Cephalaspidse, animals of which the head was
defended with large bony enamelled plates, and fragments
of one genus of which (the Pterichtys) were long mistaken
for trilobites, belong exclusively to the devonian forma-
tion (old red sandstone) ; this family constitutes, according
to Agassiz, as distinctly marked a type in the series of fishes,
as that which includes the Ichthyosaurus and Plesiosaurus
among reptiles. (30°) Goniatites, belonging to the tribe
of ammonites, (301) also begin to shew themselves in the
limestone, and in the greywacke of the devonian formation;
and even appear in the lower silurian strata.
In respect to invertebrate animals, no very clear relation
has yet been recognised between the age of rocks, and the phy-
siological gradation of the species which they contain : (302)
but this relation manifests itself in a very systematic manner in
vertebrate animals. In these, the most, ancient forms, as
?AL;EZOOLOGY : FOSSIL ANIMALS. 263
we have just seen, are those of certain fishes ; ascending
in the scale of superposition, we find first reptiles, and
then mammalia. The first reptile (a Saurian of the genus
Monitor, according to Cuvier), and which had already at-
tracted the notice of Leibnitz, (303) is found in the copper
slate (Kupferschiefer) of the zechstein in Thuriugia; the
Paleosaurus and the Thecodontosaurus of Bristol, belong,
according to Murchison, to the same period. The number
of Saurians continues to augment in the muschelkalk,(304)
tlie keuper sandstone, and the oolite in which they reach
their maximum. At the oolitic period (including under
this name the lias) lived several species of Plesiosaurus, an
animal having a long swan-like neck, formed in some cases
df upwards of thirty vertebrae ; the Megalosaurus, a gigantic
reptile of forty- five feet in length, with bones of the extre-
mities resembling those of the heavy terrestrial quadrupeds;
eight species of Ichthyosauri with enormous eyes; the
Geosaurus (Sommering's Lacerta gigantea) ; and seven species
ctf hideous Pterodactyles, or reptiles with membranous
wings. (305) There existed also towards the latter part of
the period the colossal Iguanodon, an herbivorous animal ,
and in the chalk where the number of crocodilian Saurians
begins to diminish, we find the Mososaurus of Conybeare,
a crocodile of Maestricht. We learn from Cuvier, that
animals belonging to the present race of crocodiles are found
in the tertiary formations ; and Scheuchzer's supposed hu-
man skeleton (homo diluvii testis), a great salamander
allied to the axolotl which I brought from the lakes around
the city of Mexico, belongs to the most recent fresh water
formations of (Eningen.
In studying the relative age of fossils by the order of
superposition of the strata in which they are found, impor-
PALAEONTOLOGY I FOSSIL ORGANIC REMAINS.
tant relations have been discovered between families and
species (the latter always few in number) which have dis-
appeared, and those which are still living. All observations
concur in shewing, that the fossil faunas and floras differ
from the present animal and vegetable forms the more widely,
in proportion as the sedimentary beds to which they belong
are lower or more ancient. Thus great variations have suc-
cessively taken place in the general types of organic life ;
and these grand phsenomena, which were first pointed out by
Cuvier, (306) offer numerical relations, which Deshayes and
Lyell have made the object of important researches, by which
they have been conducted to decisive results, especially as re-
gards the numerous and well observed fossils of the different
groups of the tertiary formation. Agassiz, who has exa-
mined 1700 species of fossil fishes, and who estimates at
8000 the number of living species which have been de-
scribed or which are preserved in our collections, affirms in
his great work, that, with the exception of one small fossil
fish peculiar to the argillaceous geods of Greenland, lie
Las never met in the transition, secondary, or tertiary strata,
with any animal of this class specifically identical with any
living fish ; and he adds the important remark, that even
in the lower tertiary formations, a third of the fossil fishes
of the calcaire grossier, and of the London clay, belong to
extinct families. Below the chalk we no longer find a single
genus of the present period ; and the singular family of the
i3auroid fishes (fishes with enamelled scales, almost approach-
ing reptiles in some of their characters, and extending up
wards from the carboniferous rocks, where the larger species
among them are found, to the chalk, where only a few indi-
viduals are met with), presents relations with two species
which now inhabit the Nile and some of the American rivers
PALJSOZOOLOGY : DOSSIL ANIMALS. 265
(the Lepidosteus and the Polypterus), similar to those exhi-
bited by the Mastodon and Anoplotherium of the ancient
world when compared with our elephants and tapirs. (307)
We learn from Ehrenberg's remarkable discoveries, that
the beds of chalk, which still contain two species of these
sauroid fishes, and in which are found gigantic reptiles, and
a considerable number of corals and shells which no longer
exist, are nevertheless composed in great part of microscopic
polythalainia, many of which are still living even in the seas
of our own latitudes, in the North Sea, and in the Baltic.
Thus we see that the tertiary, group of deposits resting imme-
diately upon the chalk, and to which the name of Eocene group
is usually given, is not strictly entitled to that desig-
nation, for the dawn of the world in which we live extends
much farther back in the history of our planet than has
been hitherto supposed. (308)
We have seen that fishes, which are the oldest verte-
brated animals, first appear in the silurian strata, and
are found in all the succeeding formations up to the
beds of the tertiary period. Reptiles begin in like manner in
the zechstein (magnesian limestone) ; and if we now add, that
the first mammalia (the Thylacotherium prevostii and Thyla-
cotherium bucklandi, allied, according to Valenciennes, (309)
to marsupial animals,) are met with in the Stonesfield
slate, a member of the oolite, — and that the first remains of
birds have been found in the deposits of the cretaceous
period, (31°) we shall have indicated the inferior limits,
according to our present knowledge, of the four j?reat divi-
sions of the vertebrata.
In regard to invertebrate animals, we find corals and
some shells associated, in the oldest formations, with very
266 PALEONTOLOGY: FOSSIL ORGANIC REMAINS.
highly organised cephalopodes and crustaceans, so that
widely different orders of this part of the animal kingdom
appear intermingled ; there are, nevertheless, many isolated
groups belonging to the same order, in which determinate
laws are discoverable. Whole mountains are sometimes found
to consist of a single species of fossil, goniatites, . trilobites,
or nummulites. Where different genera are intermingled,
there often exists a systematic relation between the series of
organic forms and the superposition of the formations ; and
it has been remarked, that the association of certain families
and species follows a regular law in the superposed strata
of which the whole constitute one formation. Thus Leo-
pold von Buch, after classifying the immense variety of
ammonites in well defined families by observing the dispo-
sition of the lobes, has shewn that the ceratites belong to
the muschelkalk, the arietes to the lias, and the goniatites
to the transition limestone and older rocks. (311) Belem-
mtes have their lower limit (312) in the keuper sandstone,
below the Jura or oolitic limestone, and their upper limit in
the chalk. It has been found that the waters in the most
distant parts of the globe were inhabited at the same epochs
by testaceous animals corresponding at least in generic
character with European fossils: for example, Von Buch
has described species of exogyra and trigonia from the
southern hemisphere (from the volcano of Maypo in Chili),
and D'Orbigny has indicated species of ammonites and
gryphsea from the Himalaya and the Indian plains of Cutch,
which have been supposed even specifically identical with
those of the ancient oolitic beds of Prance and Germany.
Strata defined by their fossil contents, 01 by the frag-
ments of other rocks which they include, form a geological
PAL^OZOOLOGY : FOSSIL ANIMALS. 267
horizon by which the geologist may recognise his position,
and obtain safe conclusions in regard to the identity or
relative antiquity of formations, — the periodical repetition of
certain strata, — their parallelism, — or their entire suppres-
sion. If we would thus comprehend in its greatest simpli-
city the general type of the sedimentary formations, we find
in proceeding successively from below upwards : —
1. The transition group, divided into lower and upper
greywacke : this group includes the silurian and devonian
systems ; the latter formerly called the old red sandstone.
2. The lower trias (313), comprising the mountain lime-
stone, the coal measures, the lower new red sandstone
(todtliegendes), and the magnesian limestone (zechstein).
3. The upper trias, comprising the hunter or variegated
sandstone, (314) the muschelkalk, and the keuper sandstone,
4. The oolitic at Jurassic series ; including the lias.
5. The cretaceous series, the quadersandstein, the lower
and the upper chalk. This group includes the Floetz forma-
tions of Werner.
6. The tertiary group, as represented in its three stages
by the calcaire grossier and other beds of the Paris basin,
the lignites or brown coal of Germany, and the sub-apennine
group in Italy.
To these succeed transported soils (alluvium), containing
the gigantic bones of ancient mammalia, such as the
Mastodons, the Dinotherium, and the Megatheroid ani-
mals, among which is the Mylodon of Owen, an animal
upwards of eleven feet in length, allied to the sloth. As-
sociated with these extinct species are found the fossil
remains of animals still living: elephants, rhinoceroses,
oxen, torses, and deer. Near Bogota, at an elevation of
8200 French feet above the level of the sea, there is
268 PALEONTOLOGY : FOSSIL ORGANIC REMAINS.
a field filled with the bones of Mastodon (Carapo da
Gigantes), in which I have had careful excavations
made. (315) The bones found on the table lands of
Mexico belong to true elephants of extinct species. The
minor ranges of the Himalaya, the Sewalik hills, which
Major Cautley and Dr. Falconer have examined with so
much zeal, contain, besides numerous Mastodons, the Siv*-
therium, and the gigantic land tortoise (Colossochelys),
more than twelve feet in length and six in height, as well
as remains belonging to still existing species of elephants,
rhinoceroses, and giraffes. It is worthy of notice, that these
fossils are found in a zone which still enjoys the same tro-
pical climate which is supposed to have prevailed at the
period of the Mastodons. (316)
Having thus viewed the series of inorganic formations
which compose the crust of the earth in combination with
the animal remains interred in them, we have still to consi-
der the vegetable kingdom of the earlier times, and to trace
the epochs of the successive floras which have accompanied
the increasing extent of dry land, and the progressive modi-
fications of the atmosphere. As we have already remarked,
the oldest strata contain only marine plants exhibiting cel-
lular tissue, the devonian strata being the first in which some
cryptogamic forms of vascular plants are found (calamites
and lycopodiacese (31?). It had been inferred from certain
theoretical views concerning the simplicity of the primitive
forms of organic life, that in the ancient world, vegetable
had preceded animal life, and that the former was in fact
always the indispensable condition of the latter. But there
do not appear to be any facts to justify this hypothesis ; and
the circumstance that the Esquimaux, and other tribes who
PALvEOPHYTOLOGY : FOSSIL PLANTS. 269
live on the shores of the Polar Sea, subsist at the present
day exclusively on fish and cetaceae, is alone sufficient to
shew that vegetable substances are not absolutely indispen-
sable to the support of animal life. After the devonian
strata and the mountain limestone, we come to a formation
in which botanical analysis has recently made the most
brilliant progress. (318) The coal measures contain not only
cryptogamic plants analogous to ferns,, and phsenogamoua
monocotyledones (grasses, yucca-like liliacese, and palms),
but also gymnospermic dicotyledones (coniferae and cycadere) .
We have already distinguished nearly four hundred species in
the coal formation, but of these I will here merely enumerate
arborescent calamites and lycopodiacece ; the scaly lepido-
dendron ; the sigillaria, sixty feet long, distinguished by a
double system of vascular fascicles, and sometimes found
upright and apparently having its roots attached ; the stig-
maria, approaching in some respects the cactacese ; an im-
mense number of fronds and sometimes stems of ferns, which,
by their abundance, indicate the insular character of the dry
land of that period ;(319) cycaclese, (32°) and especially
pilms, (321) though fewer in number than the ferns ; astero-
phyllites, with verticillate leaves, allied to naiades; and
coniferse, resembling araucarias, (322) having some faint
traces of annual rings. All this vegetation was luxuriantly
developed on those parts of the older rocks which had risen
above the surface of the water, and the characters which dis*
tinguish it from our present vegetation were maintained
through all subsequent epochs up to the last of the cretaceous
strata. The flora of the coal formation, comprising these
remarkable forms, presents a very striking uniformity of
distribution in genera, if not in species, ove? all the
270 PALAEONTOLOGY: FOSSIL OKGANIC TIEMAINS.
parts of the surface of the earth which were then exist-
ing, as in New Holland, Canada, Greenland, and Melville
Island. (32^)
The vegetation of the ancient world presents forms
which, by their affinities with several families of living
plants, shew that in their extinction we have lost many
intermediate links in the organic series. Thus, for example,
the lepidodendra find their pace, according to Lindley, be-
tween the coniferse and the lycopodiacese ; (324) whilst the
araucarise and the pines present differences in the junction of
their vascular fascicles. Even limiting our consideration to
the present vegetable world, we perceive the great impor-
tance of the discovery of cycadese and coniferse, in the
flora of the coal measures, by the side of sagenarise and
lepidodendra. Coniferse are allied not only to cupuliferae
and betulinse, with which they are associated in the lig-
nites, but also to the lycopodiacese. The family of the
eycadese in their external aspect approach palms, while
in the structure of their flowers and seeds they present
material points of accordance with coniferse. (325) Where
many beds of coal are placed one above another, the genera
and species are not always intermingled, but are more often
eo disposed that only lycopodiacese and certain ferns are
found in one bed, and stigmatise and sigillarise in another.
To give an idea of the luxuriance of vegetation in the pri-
mitive world, and of the immense vegetable masses accumu-
lated in particular places by streams or currents, and
transformed (326) into coal, I will notice the coal measures
of Saarbruck, where a hundred and twenty beds are found
one above another, exclusive of a great number which
are not more than a foot thick* and there are beds
PAL.EOPHYTOLOGY : FOSSIL PLANTS. 271
exceeding thirty, and even exceeding fifty feet in thick-
ness, as at Johnstone in Scotland, and in the Creuzot
in Burgundy. In the forests of the temperate zone at the
present period, the carbon contained in the trees which
grow upon a given surface would hardly suffice to cover it
with an average thickness of seven French lines in a cen-
tury. (327) it should also be remarked, that the masses of
drift-wood transported by rivers or by marine currents, such
as those which are found at the mouth of the Mississippi, and
those which have formed the " hills of wood," described by
Wrangel, on the shores of the Polar Sea, may give us some
idea of the accumulations which must have taken place near
projecting points of land in inland waters, and along the
island shores of the ancient world, and which have produced
our present coal-beds : there can be no doubt, also, that
these beds owe a considerable portion of their substance,
not to large trunks of trees, but to grasses, to low branch,
ing shrubs, and to small cryptogamia.
The association of palms and coniferse, which we have
noticed in the coal measures, continues through all the suc-
ceeding formations until far into the tertiary period. In
the present day it may almost be said that these families
avoid each other's presence. We have become so accus-
tomed (although without sufficient ground), to regard
coniferse as a northern form, that I well remember expe-
riencing a feeling of surprise, when, in ascending from the
coast of the Pacific towards ChilpansingQ and the elevated
valleys of Mexico, between the Venta de la Moxonera and
the Alto de los Caxones, at a height of above 4000 English
feet above the level of the sea, I rode for an entire day
through a thick forest of Pinus occidentalis, and saw
amongst these trees, resembling the Wey mouth pine, fan
YOL. T u
272 PALAEONTOLOGY : FOSSIL ORGANIC REMAINS.
palms (Corypha dulcis 328), covered with parrots of many-
coloured plumage. South America has oaks, but not a
single species of pine ; and the first of these familiar forms
of my native land which presented itself to my sight, was
thus in strange association with a fan palm. Columbus, in
his first voyage of discovery, saw Coniferse and palms grow-
ing together on the north-eastern point of the Island of
Cuba, (329) and consequently within the tropics and nearly at
the level of the sea. That wonderful man, whom nothing
escaped, notices this fact in his journal as remarkable ; and
his friend Anghiera, the secretary of Ferdinand the Catholic,
recounts with astonishment, that " in the newly discovered
lands palmeta and pineta are found together/' The com-
parison of the present distribution of plants over the surface
of the earth, with that disclosed by fossil floras, is of great
geological interest. The southern temperate zone, accord-
ing to Darwin's beautiful and animated description (33°) of
its ocean-covered surface, its numerous islands, and its
wonderful intermixture of tropical forms of vegetation with
those of colder regions, offers us the most instructive ex-
amples for the study of the past and present geography of
plants. The past is undoubtedly an important portion of
the history of the vegetable kingdom.
Cycadese, which, from the number of their fossil species,
must have occupied a far more important place in the
ancient than in the present vegetable world, accompany
their allies the coniferse from the coal formation upwards,
but are almost entirely wanting in the variegated sandstone,
which contains the remains of a luxuriant growth of certain
coniferse of peculiar form, Yoltzia, Haidingera, and Albertia.
The cycadese attain a maximum in the keupe* jnd the lias,
which contain twelve different species. In the cretaceous
PAL.EOPHYTOLOGY : FOSSIL PLANTS. 273
rocks, marine plants and naiades predominate. Thus, the
forests of cycadese of the oolitic period had long disappeared,
and in the oldest groups of the tertiary formation this
family is very subordinate to the coniferse and the
palms. (33i)
The lignites, or beds of brown coal, which are found in
each division of the tertiary period, contain, amongst the
earliest land cryptogamia, some palms, a great number of
coniferae with well-marked annual rings, and arborescent
forms (not coniferous) of a more or less tropical character.
The middle tertiary period is marked by the re-establish-
ment, in full numbers, of the families of palms and cycadese,
and, finally, the most recent shews great similarity to our
present vegetation, exhibiting suddenly and abundantly
various pines and firs, cupuliferse, maples, and poplars.
The dicotyledonous stems in lignite are occasionally charac-
terised by colossal size and great age. In a trunk found
near Bonn, Noggerath counted 792 annual rings. (332) In
the turf bogs of the Somme, at Yseux near Abbeville, a
trunk of an oak tree has been found above fourteen feet in
diameter, which is an extraordinary thickness for the extra-
tropical parts of the old continent. It appears from G op-
pert' s excellent investigations that " all the amber of
the Baltic comes from a coniferous tree, which, judging
from the remains of its wood and bark at different ages or
stages of growth, seems to have been a peculiar •species,
approaching nearest to our white and red pines. The
amber tree of the ancient world (Pinites succinifer) was far
more resinous than any conifer of the present period, the
resin being deposited not only as in our present trees within
and upon the bark, but also in the wood itself, following
the course of the medullary rays, which, as well as the ceils,
274 PALAEONTOLOGY ! FOSSIL ORGANIC REMAINS.
are still distinctly recognisable under the microscope, and
large masses of white and yellow resin are sometimes found
between the concentric ligneous rings. Among the vege-
table substances inclosed in amber there are male and fe-
male blossoms of native needle-leaved trees and cupuliferae ;
but distinctly recognisable fragments of Thuia, Cupressus,
Ephedera, and Castania vesca, intermingled with those of
Junipers and Firs, indicate a vegetation different from that
now subsisting on the coasts and plains of the Baltic."
We have now passed through the whole series of forma-
tions in the geological portion of the general view of nature,
from the eruptive rocks and most ancient sedimentary
strata, to the alluvial soils on which are scattered the frag^
ments of rock known by the name of " erratic blocks/' The
dissemination of these blocks has been the subject of much
discussion; it has been attributed to glaciers, and to floating
masses of ice ; but I am inclined to ascribe it rather to the
impetuous flow of waters from reservoirs in which they had
long been detained, and from which they were set free by
the elevation of mountain chains. (333) It is a point which
will probably long continue undecided, and to which I only
incidentally allude. The most ancient members of the
transition series with which we are acquainted are the
schists and greywacke, containing remains of marine plants
of the sjlurian, or, as it was before called, the cambrian sea.
On what do these oldest formations rest, or, — supposing the
gneiss and mica schist beneath them to be merely meta-
morphosed sedimentary rocks, — on what were the oldest sedi-
mentary strata deposited ? May we venture a conjecture on
that which cannot be the subject of actual geological obser-
vation ? According to an Indian mythus, the earth is sup*
PAI^EOGEOGRAPHY. 275
ported by an elephant, who, that he may not fall, is in his
turn supported by a gigantic tortoise; but the credulous
Brahmins are not permitted to ask on what the tortoise
rests. "We here venture on a somewhat similar problem,
though aware that we cannot hope to escape criticism. In
the astronomical portion of this work, reasons were given
which seemed to make it probable that our planet has
been formed from nebulous rings, separated from the solar
atmosphere, agglomerated into spheroids, and consolidated
by progressive condensation, beginning at the exterior and
proceeding towards the center. We will suppose a first
solid crust of the earth to have been thus formed, of which
the oldest silurian strata were the upper part. The eruptive
rocks, which broke through and upheaved these strata, rose
from depths inaccessible to our research ; they must have
existed, therefore, below the silurian strata, and were com-
posed of the same association of minerals which, when they
are brought to the surface, become known to us as granite,
augitic rock, and quartzose porphyry. Guided by analogy
we may assume that the substances which traverse the sedi-
mentary strata, and fill up their wide fissures, are only
ramifications of a great inferior mass. The foci of our pre-
sent volcanoes are situated at enormous depths; and,
judging from the fragments which, in various parts of the
globe, I have found imbedded in volcanic currents of lava,
I consider it as more than probable that a primitive
granitic rock is the substratum and support of the whole
edifice of superimposed fossiliferous strata. (334) Basalt,
containing olivine, does not shew itself before the cre-
taceous period, and trachyte still later ; but we find that
eruptions of granite certainly belong to the epoch of the
£76 STATE. OF THE SURFACE OF THE GLOBE
oldest sedimentary strata of the transition formation, as is
indeed shewn by the effects of their metamorphic action.
Where knowledge cannot be obtained from direct evidence,
it may well be permitted, after a careful comparison of the
facts which are accessible, to take analogy as our guide, and
to advance a conjecture which would restore to the old gra-
nite a part of its disputed claim to the title of primordial
rock.
The recent progress of geology, and the extended know-
ledge of geological epochs, characterised and determined by
the mineralogical composition of rocks, by the peculiarities
and succession of the organic remains which they contain,
and by the circumstances of their stratification, whether
uplifted, inclined, or with its horizontality undisturbed,
conduct us, pursuing the intimate causal connection of
phenomena, to the distribution of the solid and liquid por-
tions of the surface of our planet, its continents and seas.
We here indicate a connecting point between the history of
the revolutions which the globe has undergone, and the de-
scription of its present surface ; between geology and phy-
sical geography, which are thus combined in the general
consideration of the form and extent of continents. The
boundaries which separate the dry land from the liquid
element, and the relative areas of each, have varied greatly
during the long series of geological epochs ; they have been
very different, for example, when the strata of the coal for-
mation were deposited horizontally upon the inclined strata
of the mountain limestone and the old red sandstone; — when
the lias and the oolite were deposited on the keuper and the
muschelkalk ; — and when the chalk was precipitated on the
elopes of the greensand and oolitic limestone. If, with
AT DIFFERENT GEOLOGICAL EPOCHS. 277
Elie de Beaumont, we give the names of Jurassic or oolitic
sea, and of cretaceous sea, to the waters from which the
oolite and the chalk were respectively deposited in soft beds,
the outlines of those formations will indicate, for the two
corresponding geological epochs, the boundary between the
dry land, and the ocean in which these rocks were then
forming. Maps have been drawn representing the state of
the globe in respect to the distribution of land and water at
these periods. They rest on a more sure basis than the
maps of the wanderings of lo, or even than those of Ulysses,
which at best but represent legendary tales, whilst the geo-
logical maps are the graphical representations of positive
facts.
The following are the results of the investigations which
have had for their object the determination of the extent of
the dry land at different epochs. In the most ancient times, —
during the silurian, devonian, and carboniferous epochs,
and even as recently as the triassic period, — the portion
of the surface supporting land vegetation was exclusively
insular. At a subsequent epoch these islands became con-
nected with each other, forming numerous lakes and deeply
indented bays. Finally, when the mountain chains of the
Pyrenees, the Apennines, and the Carpathians, were ele-
vated,— about the epoch, therefore, of the older tertiary
formations, — the great continents possessed nearly their
present form and extent. During the silurian epoch, when
the cycadese were in the greatest abundance, and the gigan-
tic saurians were living, the whole surface of dry land from
pole to pole must have been less than it now is in the
Pacific and Indian oceans. We shall see presently how this
great preponderance of oceanic surface must have contri-
273 PHYSICAL GEOGRAPHY.
buted, together with other causes, to equalise climates, p,nd
to maintain a high temperature. It is only necessary to
add here, in reference to the progressive extension of
dry land, that a short time before the cataclysms which,
at longer or shorter intervals, caused the destruction
of so many gigantic vertebrated animals, part of the conti-
nental masses presented the same divisions as at present.
There prevails, both in South America and in Australia, a
great analogy between the living animals and the extinct
species of those countries Fossil species of Kangaroo have
been discovered in New Holland ; and in New Zealand, the
semi-fossilized bones of a gigantic struthious bird, the
Dinonris of Owen, closely allied to the present Apteryx of
the same islands, and remotely so to the recently extinct
Dodo of the island of Rodriguez.
A considerable part of the height of the present continents
above the surrounding waters may perhaps be due to the erup-
tion of the quartzose porphyry, which overthrew with violence
the first great terrestrial flora, the material of our coal-beds.
The level portion of our continents, to which we give the
name of plains, are the broad summits of mountains, of
which the feet are at the bottom of the ocean : considered in
respect to submarine depths, these plains are elevated pla-
teaus, of which the original inequalities have been partially
filled up by horizontal layers of later sedimentary deposits,
and covered over with alluvium.
Amongst the leading considerations in this part of the
general contemplation of nature, we must regard, first, the
quantity of land raised above the water ; next the configu-
ration of each great continental mass in horizontal extension
GENERAL VIEW. 279
and vertical elevation. We then come to the two coverings
or envelopes of our planet, of which one, composed of
elastic fluids, the atmosphere, is general ; and the other, the
sea, is local, or restricted to portions of the earth's sur-
face. These two envelopes, air and sea, constitute a natural
whole, materially affecting the distribution of the various
climates of the surface of the globe, according to the relative
extent of land and sea, the form and aspect of the land, and
the height and direction of the mountain chains. It results
from this reciprocal influence of the atmosphere the sea
and the land, that great meteorological phsenomena cannot
be well studied apart from geological considerations. Me-
teorology, as well as the geography of plants and of animals,
have only begun to make real progress, since the mutual
connection and dependence of the phaenomena to be investi-
gated have been recognised. It is true that the word cli-
mate has especial reference to the condition of the atmo-
sphere ; but this condition is itself subjected to the double
influence of the ocean, whose agitated waters are traversed
by currents differing greatly in temperature, and of the dry
land, which radiates heat with very different degrees of in-
tensity, according to its varying characters of form, eleva-
tion, and colour, and whether bare or clothed with forests,
or with grasses or other low growing plants.
In the present state of our knowledge, the superficial ex-
tent of dry land compared to that of the liquid element, is
as 1 : 2-8; or, according to Kigaud, as 100 : 270. (335) The
islands form scarcely one-twenty-third part of the continental
masses, which are so unequally distributed, that the northern
hemisphere contains three times as much land as the southern,
twhich is pre-eminently oceanic. Prom 40° South latitude
280 PHYSICAL GEOGRAPHY.
to the Antarctic Pole, its surface is principally covered with
water. The liquid element predominates equally in the
space comprised between the eastern shores of the old, and
the western shores of the new continent, where it is only-
interrupted by a few widely-scattered groups of islands. The
learned hydrographer Meurieu has very justly given to this
great basin, which, under the tropics, extends over 145
degrees of longitude, the name of " the Great Ocean," to
distinguish it from all other seas. The southern hemisphere,
and the western (from the meridian of Teneriffe), are
therefore the most oceanic portions of the globe.
Such are the leading points in the comparison of the re-
lative areas of land and sea, — a relation which exercises a
powerful influence on the distribution of temperature, the
variations of atmospheric pressure, the direction of the winds,
and the hygrometric state of the air which materially in-
fluences the development of vegetation. When we consider
that nearly three-fourths of the entire surface of the globe
are covered by water, (336) we shall be less surprised at the
imperfect state of meteorology before the commen^ment of
the present century ; but since that epoch a considerable
mass of exact observations on the temperature of the sea
in different latitudes and at different seasons has been
obtained, and numerically compared.
The philosophers of ancient Greece indulged in general
speculations with regard to the horizontal configuration of
the dry land ; they discussed its greatest extent from east
to west, which, according to the testimony of Agathemerus,
was placed by Dicearchus in the latitude of Rhodes, and in the
direction of a linepasing from the Pillars of Hercules to Thine.
THE LAND. 281
This line has been termed the " parallel of the diaphragm of
Dicearchus ;" and the exactness of its geographical position,
which I have made the subject of discussion in another work,
may well excite our astonishment. (337) Strabo, guided no
doubt by the views of Eratosthenes, appears to have been so
fully persuaded that the 36th parallel of latitude, as the line
of greatest extent of the then known world, had some inti-
mate connection with the form of the earth, that he places
under it, between Iberia and the coast of Thine, the land of
which he divined the existence. (338)
We have noticed the great inequality in the extent of
dry land in the two hemispheres, whether we divide the
sphere at the Equator or at the Meridian of Teneriffe;
the two great insular masses, or continents, eastern and
western, old and new, present also some striking contrasts,
and at the same time some analogies, deserving of notice.
Their major axes are in opposite directions; the eastern,
or old, continent, extending, in its greatest dimension,
from east to west, or more precisely from north-east to
south-west; whilst the western continent extends from
north to south, or more exactly from N.N.W. to S.S.E.
On the other hand, both continents are terminated towards
the north by a line coinciding nearly with the 70th
parallel ; and to the south they both run into pyramidal
points, having submarine prolongations which are indi-
cated by islands and shoals : such are, the Archipelago of
iTierra del Fuego, the Lagullas bank south of the Cape of
Good Hope, and Van Diemen Island, separated from New
Holland by Bass's Straits. The northern part of Asia
passes beyond the above-mentioned (70th) parallel towards
Cape Taimura (78° 16' according to Krusenstern), and
falls short of it from the mouth of the larger Tschukotschia
282 PHYSICAL GEOGRAPHY.
river to Behring's Straits, where the eastern extremity of
Asia (Cook's East Cape) is, according to Beechey, in
66° 3' N. lat. (339) The northern shore of the new continent
follows the 70th parallel with tolerable exactness, for the
lands to the north and south of Barrow's Straits are detached
islands.
The pyramidal form of all the southern terminations of
continents belong to those " similitudines physicse in con-
figuratione mundi," to which Bacon called attention in the
Novum Organum, and with which Beinhold Eorster, one of
the companions of Cook on his second voyage of circum-
navigation, connected some ingenious considerations. Direct-
ing our attention eastward from the meridian of Teneriffe,
we perceive that the terminations of the three continent^
t. e. the southern extremities of Africa, Australia, and
America, successively approach nearer to the South Pole.
New Zealand, which is fully twelve degrees of latitude in
length, seems to form a regular intermediate member between
Australia and South America; its southern termination is
likewise marked by an island, New Leinster. We may
notice, further, as a remarkable circumstance, that tlie
projecting points of the old continent, both to the north and
to the south, are nearly under the same meridian ; thus the
Cape of Good Hope and the Lagullas bank are situated nearly
in the same meridian as the north cape of Europe ; and the
peninsula of Malacca nearly in that of Cape Taimura. (34°)
We know not whether the two poles of the Earth are sur-*
rounded by land, or by an ice -covered sea; towards the
North Pole, the parallel of 82° 55' has been reached, and
towards the South Pole, that of 78° 10'.
The pyramidal terminations of the great continents are
frequently repeated on a smaller scale, not only in the Indian
THE LAND. 283
ocean, in the peninsulas of Arabia, Hindostan, and Malacca,
but also in the Mediterranean, where Eratosthenes and
Polybius had compared in this respect the Iberian,
Italic, and Hellenic Peninsulas. (341) Europe itself, having
an extent of surface equalling only one-fifth part of that of
Asia, may be considered as the western peninsula of the
compact mass of the Asiatic continent, to which it bears, in
point of climate, a relation somewhat similar to that of
the peninsula of Brittany to the rest of Prance. (342) The
favourable influence of the articulated and varied form of a
continent on the civilization and intellectual cultivation of
its inhabitants was recognised by Strabo, (343) who extolled
as a special advantage the richly varied form of our little
Europe. Africa (344) and South America, which also offer
many other features of analogy in their configuration, are the
two continents which have the simplest and least indented
outlines, while the eastern side of Asia, as if it were rent by
the force of the currents of the ocean, (345) (fractas ex
sequore terras), presents a richly varied coast line ; peninsulas
and islands alternate along its shores, from the equator to
60° N. latitude.
Our Atlantic Ocean presents the characteristics of a valley.
It is as if the flow of the waters had been directed first
towards the north-east, then towards the north-west, and
then again towards the north-east. The parallelism of
the coasts north of 10° of South latitude, the projecting and
re-entering angles, the convexity of Brazil opposite to the
Gulf of Guinea, and the convexity of Africa to the Gulf of
Mexico, all favour tin's view, which at first may seem too
hazardous. (346) In the Atlantic Valley, as is indeed usually
the case in the form of large masses of land, coasts deeply
284 PHYSICAL GEOGRAPHY.
indented and fringed with many islands are placed opposite
to those of a contrary character. It is long since I called
attention to the geognostical interest of the comparison of the
west coasts of Africa and of South America. Within the
tropics, the deeply re-entering curve of the African coast
near Fernando Po (4°j-N. lat.), is repeated on the shores of
the Pacific (in 18°i S. lat.), where, between the Valle de
Arica and the Morro of Juan Diaz, the Peruvian coast sud-
denly alters the direction from south to north which it had
previously followed, and turns to the north-west. This
change of direction in the coast of Peru is participated in
by the chain of the Andes ; (347) and not only by the maritime
branch of the two parallel ranges into which the mountains
are there divided, but also by the eastern Cordillera, in which
civilisation had its earliest seat in the South American
highlands, and where the small alpine lake of Titfaca lies at
the foot of the giant mountains of Sorata and Illimani.
Farther to the south, from Yaldivia and Chiloe in 40° and
42° S. lat,, through the Archipelago of los Chonos, to Tierra
del Fuego, we find the same peculiar " fiord" character,
which distinguishes the west coasts of Norway and
Scotland.
Such are the most general considerations respecting the
form of continents in the horizontal direction, which an
examination of the present surface of our planet suggests.
"We have brought facts together, so as to call attention to
certain analogies of form in regions remote from each other,
without, however, venturing to give to these analogies the
title of laws. When an observer at the foot of an active
volcano, Vesuvius for example, notices the not unfrequerit
phenomenon of partial elevations, in which, previously to, or
THE LAND. 285
during the occurrence of an eruption, small portions of
ground have their level permanently altered several feet, and
are converted into shelving or flattened eminences, he per-
ceives how greatly small accidental variations in the intensity
of the subterranean force, and in the resistance which it has
to overcome, must modify the form and direction taken by
the upheaved particles. In like manner slight disturbances
in the equilibrium of the elastic forces in the interior of our
planet may have determined their action more towards the
northern than the southern hemisphere, and have occasioned
the elevation of the dry land in the eastern hemisphere in the
form of a wide connected mass, having its major axis almost
parallel to the equator, — and in the western and more oceanic
hemisphere, in a comparatively narrow band, following the
direction of the meridian.
But little can be ascertained by investigation respecting
the causal connection of the great phenomena appertaining
to the formation of our continents, and to the analogies and
contrasts presented by their configuration. We know that
a subterranean force was the agent; that the continents
were not suddenly formed in their present shape, but that
they gradually acquired it by progressive enlargement, or by
the junction of smaller masses, effected by a series of
successive elevations and depressions, commencing with the
siluiian epoch, and continuing to the tertiary. The present
form has been produced by two causes which have acted in
succession the one after the other : the first is a subterranean
reaction, of which the measure and direction are unknown to
us ; the second comprises all the causes acting at the surface,
as volcanic eruptions, earthquakes, elevations of mountain
chains, and oceanic currents. How different would have
been the present state of temperature, of vegetation, of agri-
286 PHYSICAL GEOGRAPHY.
culture, and even of human society, if the major axes of the
old and new continents had been given the same direction ;
if the chain of the Andes, instead of following a meridian,
had been directed from east to west ; if no heat-radiating
mass of tropical land extended to the South of Europe ; or if
the Mediterranean, which was once in connection both with
the Caspian and Red Sea, and which has so powerfully
favoured the social establishment of nations, were not in
existence : that is to say, if its bed had been raised to
the level of the plains of Lombardy and of the ancient
Cyrene.
The changes in the relative heights of the solid and liquid
portions of the surface, which have determined the emersion
or submersion of the lower lands and the present outlines of
continents, must be referred to various causes acting at
different times. The most powerful among these have
no doubt been, elastic forces acting in the interior of the
earth; sudden changes of temperature affecting great
masses of rock ; (348) the unequal secular loss of heat in the
terrestrial crust and in the nucleus, causing ridges and con-
tortions in the solid crust ; and local modifications of gravi-
tation, (349) with consequent changes of curvature in the
surface of equilibrium of certain portions of the liquid ele-
ment. According to the opinion generally received among
the geologists of the present day, the elevation of conti-
nents above the sea is a real, and not merely an apparent or
relative elevation, such as would be occasioned by a de-
pression of the general level of the sea. The merit of
this view, which has been derived from long observation
of connected facts, and from the analogy of important
volcanic phenomena, belongs to Leopold von Buch, who
advanced it for the first time in the narrative of his memo-
THE LAND. 287
rable journey through Norway and Sweden, in 1806 and
1807. (35°) While the whole coast of Sweden and Pin-
land, from Srelvitsborg at the limit of Northern Scania,
to Torneo, and from Torneo to Abo, is undergoing a
gradual rise amounting to four Prench feet in a century,
the southern part of Sweden, according to Nilsson, is being
depressed. (351) The elevating force appears to attain its
maximum in the north of Lapland, and to diminish gradu-
ally southwards towards Calmar and Sselvitsborg. Lines
marking the ancient level of the sea, in pre-historic times,
may be traced throughout Norway, (352) from Cape Lindes-
naes to the North Cape, by banks of shells identical
with those of the present sea ; these lines have been
recently examined and measured with great exactness by
Bravais, during his long winter sojourn at Bosekop. The
banks rise as high as 600 (640 English) feet above the
present level of the sea, and reappear, according to Keilhau,
and Eugene Eobert, on the coast of Spitzbergen, opposite to
the North Cape, in a N.N.W. direction. Leopold von
Buch, who was the first to call attention to the high
bank of shells at Tromsoe (lat. 69° 40'), has shewn,
that the more ancient elevations of the shores washed
by the North Sea belong to a series of phenomena wholly
different from the gentle and gradual elevation of the
Swedish coast in the Gulf of Bothnia. Nor must this latter
phenomenon, which has been established by sure historical
evidence, be confounded with changes of level caused by
earthquakes, as on the coasts of Chili and of Cutch : it has
recently led to similar observations in other countries, and
instances have been found, in which a sensible subsidence in
one part takes place, corresponding to an elevation else-
VOL. I. X
288 PHYSICAL GEOGRAPHY.
where; this has been observed in West Greenland (by
Pingel and Graah), in Scania, and in Dalmatia.
As it appears more than probable that, in the earlier
periods of our planet, the elevations and depressions of its
surface were much more considerable than at present, we
ought not to be surprised at finding, even in the interior of
continents, portions of the surface depressed below the
general level of the present sea ; as the small natron lakes
described by General Andreossy, the small bitter lakes of
the isthmus of Suez, the Caspian Sea, the lake or sea of Tibe-
rias, and above all, the Dead Sea. (353) The levels of the
two last-named seas are respectively 625 (666 English) and
1230 (1311 English) feet below the level of the Mediter-
ranean. If we could remove the alluvial soil which so fre-
quently covers the rocky strata in the level portions of the sur-
face of the earth, we should discover how many parts of the
denuded crust are below the present level of the sea. The
periodical, but irregularly recurring, rise and fall of the
Caspian, of which I observed distinctly marked traces in the
northern portion of the basin of that sea, (354) and the obser-
vations of Darwin in the Coral Sea, (35S) appear to indicate
that, without earthquakes properly so called, the surface of the
earth still undergoes in some places slow and continued
oscillations, similar to those which, in earlier times, must
have been of very general oocurrence in the then thinner
solid crust.
The phenomena to which we are now directing our atten-
tion remind us of the instability of the present order of
things, of the changes to which the outline and form of
continents are probably still subject in long intervals of
time. These variations, though hardly sensible from one
THE LAND. 289
generation to the next, accumulate and become so in pe-
riods similar in duration to those of the remoter heavenly
bodies. The eastern coast of the Scandinavian peninsula
may have risen about 320 French feet in 8000 years; in
12000 years, if the present rate of movement were uniformly
continued, the parts of the bed of the sea nearest to the
shore, now covered with 45 fathoms of water, would begin to
emerge. Such intervals of time, however, are short, when com-
pared with the length of the geological periods disclosed to
us by the series of superposed formations, and by the suc-
cessive groups of extinct organic forms. "We have hitherto
considered only the phenomena of elevation ; but the analogy
of observed facts will justify us in assuming the equal possi-
bility of the depression of large tracts of country : the mean
height of the parts of France which are not mountainous is
less than 480 (512 English) feet: geological changes, of
moderate amount compared with those which took place in
the earlier periods of the globe, would therefore be suffi-
cient to effect the permanent submersion of large portions
of north-western Europe, and would alter materially its
general configuration.
All variations in the form of continents are produced either
by the elevation or the depression of the land or sea, and
these are complementary phsenomena, since the real elevation
of the one element produces the appearance of a depression
in the other. In a general contemplation of nature such a*
is here presented, we should not overlook the possibility at
least of a real depression of the general level of the ocean,
or a diminution of the quantity of its waters. No one in
the present day can doubt that, at the periods when the
surface of the earth possessed a higher temperature, — when
290 PHYSICAL GEOGRAPHY.
wide fissures, capable of receiving large masses of water, were
frequent, — and when the constitution of the atmosphere dif-
fered materially from what it now is, — great changes of the
oceanic level may have taken place from variations in the
actual quantity of water : but in the present state of our
planet, there is no direct evidence whatsoever of a progres-
sive augmentation or diminution of the waters of the sea ; nor
is there any evidence of a progressive change in the mean
height of the barometer at the level of the sea. According
to Daussy and Antonio Nobile's experimental investigations,
an increase in the mean height of the barometer would
itself occasion a depression of the level of the sea. As, how-
ever, the mean pressure of the atmosphere is not the same in
all latitudes, owing to meteorological causes, such as the gene-
ral direction of the wind and the hygrometric state of the air,
the barometer alone would not afford certain evidence of varia-
tions in the general level of the ocean. The remarkable fact,
that several of the ports of the Mediterranean were repeatedly
left dry for several hours about the commencement of the pre-
sent century, appears to shew that, without any actual diminu-
tion of the general mass of water, or any general depression of
the oceanic surface, changes in the direction and strength of
currents may occasion a local retreat of the sea, and possibly
a permanent emersion of a small portion of coast ; but we
cannot be too cautious in the interpretation of our very
recently acquired knowledge of these complicated phenomena,
lest we should be led to attribute to one of the old " four
elements," water, that which really belongs to two others,
viz. the air and the earth.
As the external form of continents, in the varied and deeply-
indented outline of their coasts, exercises a beneficial intiu-
THE LAND. 291
ent-e on climate, trade, and the progress of civilisation, so also,
in the interior, the variations of form in the vertical direction,
by mountains, hills, valleys, and elevated plains, have conse-
quences no less important. Whatever causes diversity of
form or feature on the surface of our planet, — mountains,
great lakes, grassy steppes, and even deserts surrounded by
a coast-like margin of forest, — impresses some peculiar mark
or character on the social state of its inhabitants. Continuous
ridges of lofty mountains covered with snow impede inter-
course and traffic ; but where lowlands are interspersed with
discontinuous chains, and with groups of more moderate eleva-
tion, (356) such as are happily presented by the south-west of
Europe, meteorological processes and vegetable products are
multiplied and varied ; and different kinds of cultivation, even
under the same latitude, give rise to different wants, which
stimulate both the industry and the intercourse of the inhabi-
tants. Thus those formidable terrestrial revolutions, in which,
by the reaction of subterranean forces, portions of the oxidized
crust of the globe were upheaved, and lofty mountain chains
were suddenly formed, have served, when repose was re-esta-
blished and organic life re-awakened, to furnish a more beau-
tiful and richer variety of individual forms, and to rescue the
greater part of the dry land in both hemispheres from a
dreary uniformity, which tends to impoverish both the phy-
sical and the intellectual powers of man.
The great views of Elie de Beaumont assign a relative age
to each system of mountains, on the principle that their eleva-
tion must necessarily have intervened between two periods; —
between the deposition of the strata which have been upheaved
and inclined., and of those which extend in undisturbed hori-
292 PHYSICAL GEOGRAPHY.
zontality to the base of the mountains, and which must there-
fore have been deposited subsequently to the strata which
are inclined. (357) The ridges of the crust of the earth,
which are of the same geological age, appear to follow a com-
mon direction. The line of strike of the uplifted strata is not
always parallel to the axis of the chain, but sometimes inter-
sects it; whence I am led to infer, (358) that the pheno-
menon of the inclining of the strata, or of the disturbance of
their horizontality (which sometimes extends to the adjacent
plain), must, in such cases, be older than the elevation of the
mountains. The general direction of the land of the European
continent is from south-west to north-east, and is at right
angles to the direction of the great fissures, which is from
north-west to south-east, extending from the mouths of the
Ehine and the Elbe through the Adriatic and Bed Seas,
and the mountain system of Puschti-koh in Louristan, and
terminating in the Persian Gulf and Indian Ocean. This
rectangular intersection of the continent, in the direction of
its principal extent, has powerfully influenced the commer-
cial relations of Europe with Asia and the north of Africa,
as well as the progress of civilization on the formerly more
flourishing shores of the Mediterranean. (359)
The more the imagination and the intellect are impressed
by lofty and massive mountain chains, from the evidences
they afford of great terrestrial revolutions, — as the boundaries
of different climates, — as the lines of separation from whence
the waters flow to opposite regions, — and as the sites of a
peculiar vegetation, — the more necessary is a correct numeri-
cal estimation of their volume, in order to show the smallness
of their mass when compared either to that of the continents, or
THE LAND, 293
to that of the adjacent countries. Let us take, for example,
the chain of the Pyrenees, in which both the mean ele-
vation and the area covered have been measured with
great exactness, and if we suppose the whole mass of these
mountains to be spread equably over France, we find thai- its
surface would be only raised thereby 108 (115 English)
feet. In like manner, if the material which forms the chain
of the Alps were spread equably over the whole surface of
Europe, it would not raise it more than 20 (21.3 English)
feet. I have found by a laborious investigation, which from
its nature can only give a maximum limit, that the center
of gravity of the land at present above the surface of the
ocean is, in Europe 630, in North America 702, in Asia
1062, and in South America 1080 French feet (or 671, 748,
1132, and 1151 English feet) above the level of the sea. peo)
These results shew that the more northern regions are
comparatively of lower altitude. In Asia, the low ele-
vation of the extensive plains, or steppes, of Siberia, is
compensated by the mountain masses between the parallels
of 28i° and 40°, from the Himalaya to the Kuen-lun of
Northern Thibet, and to the Tian-schian or celestial moun-
tains. We may in some degree form an idea, from these
calculations, in what portions of the surface of the globe the
action of the subterranean plutonic forces, as exhibited in the
upheaval of continental masses, has been most intense.
There is no sufficient reason why we should assume that
the subterranean forces may not, in ages to come, add new
systems of mountains to those which already exist, and of which
Elie de Beaumont has studied the directions and relative
epochs. Why should we suppose the crust of the earth to
294 PHYSICAL GEOGRAPHY.
be no longer subject to the agency which has formed the
ridges now perceived on its surface ? Since Mont Blanc,
and Monte Rosa, Sorata, Illimani, and Chimborazo, the
colossal summits of the Alps and the Andes, are considered
to be amongst the most recent elevations, we are by no means
at liberty to assume that the upheaving forces have
been subject to progressive diminution. On the contrary,
all geological phenomena indicate alternate periods of
activity and repose ; (361) the quiet which we now enjoy is
only apparent ; the tremblings which still shake the surface
in every latitude, and in every species of rock, — the pro-
gressive elevation of Sweden, and the appearance of new
islands of eruption, — are far from giving us reason to sup-
pose that our planet has reached a period of entire and final
repose.
The two ambient coverings of the solid surface of our
planet, the liquid ocean and the aerial atmosphere, present,
by reason of the mobility of their particles, many analogies
with each other with respect to currents and thermometric
relations ; whilst, at the same time, they also offer contrasts
arising from the great difference in their conditions of
aggregation and elasticity. The height and depth of both
are unknown : soundings of 27600 English feet (or above
four geographical miles) have been taken without finding
any sea bottom ; and if we assume with Wollaston that the
atmosphere has a limit from which waves reverberate, the
phsenomena of twilight will indicate a height at least nine
times as great. The aerial ocean rests partly on the
solid earth, whose mountain chains and high table lands
THE OCEAN.
may be considered to represent shoals ; and partly on the
sea, whose surface forms a liquid base or floor in immediate
contact with the lower and denser strata of humid air.
Proceeding both upwards and downwards from the
common limit or plane of contact of the atmosphere and the
ocean, we find the strata of air and of water subject to
definite laws of decreasing temperature. The decrease is
much more rapid in the ocean than in the atmosphere ; the
sea has, in all zones, a tendency to keep up the temperature
of its superficial strata by the sinking of the cooled particles
which are the heaviest. It has been found, by an extensive
series of careful observations, that the surface temperature
of the ocean, throughout a band extending forty-eight degrees
on either side the equator, is, in its usual and mean condition,
somewhat warmer than the adjacent strata of the air. (362) By
reason of the diminishing temperature at increasing depths,
fish and other inhabitants of the sea, whose organs are fitted
for deep water, may find even under the tropics the low
temperature of cooler latitudes. This circumstance, which
, is analogous to that of the temperate and even cold Alpine
climate of the elevated plains of the torrid zone, has an im-
portant influence on the migration and on the geographical
distribution of many marine animals. The depths also at
which fishes live, exercise, by reason of the increased pressure,
a modifying influence on their cutaneous respiration, and on
the quantity of oxygen and nitrogen contained in their
swimming bladders.
The saline particles of sea water causing it to attain its
maximum of density at a lower temperature than is the case
with fresh water, we comprehend why water brought up from
oceanic depths, in the voyages of Kotzebue and Dupctit
296 PHYSICAL GEOGRAPHY.
Thouars, was found at the temperature of 2°.8 and 2°.5 Cent,
(37° and 36°.5 Mi.), and even lower. The almost icy tern-,
perature found at great sea depths within the tropics first led
to the knowledge of a submarine polar current flowing from
either pole towards the equator ; as without this current the
depths of the tropical seas could only have a degree of cold
equal to the lowest temperature of their surface water. The
apparent anomaly offered in the Mediterranean, whose waters
are found of a higher temperature than is usual at great
depths, has been explained by Arago, and results from the
fact that, at the Straits of Gibraltar, where the surface water
of the Atlantic flows in as a westerly current, a counter current
prevails beneath, and prevents the influx from the ocean of
the cold current from the pole.
The Ocean is the great moderator and equalizer of ter-
restrial climates ; at a distance from coasts, and where its
surface is not disturbed by currents of cooled or heated
water, it maintains throughout the tropics (and especially in
the equatorial region from 10° N. to 10° S.) a wonderful
uniformity and constancy of temperature (363) over spaces of
many thousand square miles. It has, therefore, been well
said, p64) that an exact and long-continued investigation of
the thermic relations of the tropical seas might afford, in the
simplest manner, a solution of the great and long-contested
problem of the invariability of climates and of the tempera-
ture of the globe. Great changes of solar heat, of considerable
duration, would be reflected in the altered mean temperature
of the sea, with even greater certainty than in the mean
temperature of the land.
Those zones in which the waters of the ocean attain in the
one case their maximum of temperature, and in the other their
THE OCEAN. 297
maximum of density resulting from their saline contents, do not
coincide with each other, or with the geographical equator.
The waters of highest temperature appear to form two bands
not quite parallel, one on either side of the equator. Lenz,
in his voyage of circumnavigation, found in the Pacific the
maxima of saltness in 22° N. and in 17° S. lat., and be-
tween them a minimum zone was interposed a few degrees
south of the equator. Within the region of calms the
solar heat has little effect in augmenting the relative propor-
tion of the saline particles by the process of evaporation,
because the stratum of air saturated with aqueous vapour
which rests on the surface of the water is rarely disturbed
by the action of the wind.
The surfaces of all connected seas must be regarded as
possessing a general equality of mean level, although local
causes (such as prevailing winds or currents) may produce
small permanent differences in particular seas which form
deep gulfs or inlets. An instance of this occurs in the Bed
Sea, whose level, near its northern extremity at the Isthmus of
Suez, is, at different hours of the day, from twenty-four to thirty
Trench feet above that of the neighbouring part of the Medi-
terranean : the form of the Straits of Bab-el-Mandeb, which
is more favourable to the ingress of the waters of the Indian
ocean than to their egress, being probably the cause of this
remarkable fact, which was not unknown to the ancients. (365)
The excellent geodesic operations of Corabceuf and Delcros
have shewn that at the two extremities of the Pyrenean
Chain, as well as at Marseilles and the northern coast of
Holland, there is no sensible difference between the level of
the Atlantic and of the Mediterranean Seas. (366)
PHYSICAL GEOGRAPHY.
Disturbances of equilibrium, and consequent movements
af the waters, are of three kinds : 1st, irregular and transitory,
occasioned by winds, and producing waves which sometimes
during storms, and at a distance from coasts, attain a height
of more than 37 English feet ; 2d, regular and periodic,
dependent on the position and attraction of the Sun and
Moon ; and, 3d, the less considerable but permanent phce-
nomena of oceanic currents. The tides extend over all
seas (except those small inland seas where the ebb and
flow is scarcely if at all perceptible) ; they have received a
complete explanation by the Newtonian doctrine, and have
been thus brought " within the domain of necessary facts."
The duration of each of these periodical oscillations ot
the sea is rather more than half a day; their height
in the open ocean is not more than a few feet ; but when
the configurption of a coast opposes the progress of the
wave, they may reach upwards of 50 feet, as at St. Malo,
or even of 70 feet, as in the Bay of Pundy. The great
geometer, Laplace, has shewn that, regarding the depth of the
sea as inconsiderable in relation to the semi-diameter of the
earth, the stability of equilibrium of the ocean requires
that the density of its fluid mass should be less than the
mean density of the earth. We have already seen that the
mean density of the earth is actually five times that of water.
Tides, therefore, caused by the action of the Sun and Moon
can never overflow the elevated portions of the dry land; nor
can they have transported the remains of marine animals to
the summits of the mountains where they are now found. (367)
It is no small testimony of the value of analysis, sometimes
so contemptuously regarded in the unscientific circles of
THE OCEA^. 299
civil life, that by his complete theory of tides, Laplace has
enabled us to predict in our astronomical ephemerides the
height of spring tides at the periods of new and full moon.
Oceanic currents, which exercise an important influence
on the climate of neighbouring coasts, and on the intercourse
of nations, depend concurrently on a variety of causes of
unequal magnitude and operation. Amongst these we may
reckon the propagation of the tide-wave in its progress round
the globe, the duration and strength of prevailing winds,
the variations of density which sea-water undergoes in
different latitudes and depths by changes of temperature and
of the relative quantity of its saline contents, (368) and, finally,
the horary variations of the atmospheric pressure, so regular
in the tropics, and propagated successively from east to west.
The currents of the ocean present a remarkable spectacle ;
maintaining a nearly constant breadth, they cross the sea in
different directions, like rivers of which the adjacent undis-
turbed masses of water form the banks. The line of de-
marcation between the parts in motion, and those in repose,
is most strikingly shewn in places where long bands of sea-
weed, borne onward by the current, enable us to estimate its
velocity. Analogous phenomena are sometimes presented
to our notice in the lower strata of the atmosphere, when,
after a violent storm, the path of a limited aerial current
may be traced through the forest by long lanes of over-
thrown trees, whilst those on either side remain unscathed.
The general movement of the sea from east to west be-
tween the tropics, known by the name of the equatorial
or rotation current, is regarded as the joint effect of the
trade winds, and of the progressive propagation of the tide-
wave. Its direction is modified by the resistance which it
300 PHYSICAL GEOGRAPHY.
experiences from the eastern coasts of continents. The ve
locity of this current, computed by Daussy from data sup-
plied by bottles purposely thrown overboard and subse-
quently picked up in different localities, agrees within
one eighteenth part with the velocity of ten Trench nautical
miles in twenty-four hours, which I had previously deduced
from comparing the experience of different navigators. (369)
Columbus was aware of the existence of this current at
the period of his third voyage, (the first in which he sought to
enter the tropics in the meridian of the Canary Islands), since
we find in his journal the following passage : — " I regard
it as proved that the waters of the sea move from east to
west as do the heavens" (or the apparent motion of the
sun, moon, and stars), " las aguas van con los cielos." (37°)
Of the narrow currents, or true oceanic rivers, of which
we have spoken, some carry warm water into higher, and
others cold water into lower latitudes. To the first class
belongs the celebrated gulf stream, (371) the existence of
which was recognised by Anghiera, (372) and more particu-
larly by Sir Humphry Gilbert, as early as the sixteenth
century, and of which the first origin and impulse is to be
sought to the south of the Cape of Good Hope. After a
wide circuit, it pours itself from the Caribbean Sea and the
Mexican Gulf through the channel of the Bahamas, and
following a direction from S.S.W. to N.N.E., deviates more
and more from the coast of the United States, until, de-
flected still further to the east by the banks of Newfoundland,
it crosses the Atlantic, and casts an abundance of tropical
seeds (Mimosa scandens, Guilandina bonduc, Dolichos
urens) on the coasts of Ireland, of the Hebrides, and of
Norway. Its north-easternmost prolongation mitigates the
THE OCEAN. 301
cold of the ocean, and exercises a beneficent influence on
the climate of the northernmost point of Scandinavia. At
the point where the stream is deflected to the east by the
banks .of Newfoundland, it sends off an arm toward the
south, not far from the Azores. (375) This is the situation
of the Sargasso Sea, or that great sea of weed, or bank of
fucus, which made so lively an impression on the imagina-
tion of Columbus, and which Oviedo calls sea- weed mea-
dows,— "praderias de yerva." These evergreen masses of
Fucus natans (one of the most widely distributed of the
social sea plants), driven gently to and fro by mild and
warm breeses, are the habitation of a countless number of
small marine animals.
This great current, which, in the Atlantic valley, between
Africa, America, and Europe, belongs almost entirely to the
northern hemisphere, has its counterpart in the Southern
Pacific Ocean, in a current the effect of whose low tempera-
ture on the climate of the adjacent coasts was first brought
into notice by myself in the autumn of 1802. This current
brings the cold water of the high south latitudes to the coast
of Chili, and follows its shores and those of Peru north-
ward to the bay of Arica, and thence north-westerly to
the neighbourhood of Payta, where the most westerly pro-
jection of the American coast deflects the stream, and
causes :v, suddenly to quit the shore, taking a due west
direction. Here the boundary is so sharply marked, that a
fillip sailing northwards finds itself passing suddenly from
cold to warm water. At certain seasons of the year this
cold current brings into the tropics water of 15°.6 Cent.
(60° Pah.), the temperature of the undisturbed masses of
water in the vicinity being from 27°.5 to 28°.7 Cent.
(81°.5 to 83°.7 Pah.)
302 PHYSICAL GEOGRAPHY.
"We do not know the depth to which oceanic currents
(warm or cold) extend: the deflection of the South
African current by the Lagullas bank, which is from
sixty to seventy fathoms deep, would indicate it to be
considerable. The presence of sand banks and shoals, not
situated in any line of current, may be recognised by the
low temperature of the water over them; and the knowledge
of this fact may often conduce to the safety of navigation.
It was first discovered by the justly celebrated Benjamin
Franklin, who may be said to have thereby transformed the
thermometer into a sounding line; and its explanation ap-
pears to be, that when in the general movement of the
water forming the current, the deeper situated and colder
particles strike upon a bank, their motion is inclined up-
wards, and they mingle with and chill the upper stratum of
water. My late illustrious friend, Sir Humphry Davy,
attributed the phsenomenon rather to the descent of the
surface particles, cooled by nocturnal radiation, and to their
being prevented from sinking deeper by the shoal, which
thus retained them in closer proximity to the surface. Mists
are frequently met with over shoals, from the influence of
the cooled water in condensing the vapour in the atmo-
sphere. I have seen such mists to the south of Jamaica,
aud in the Pacific, which have shewn the outline of the
shoals beneath so well defined, as to be distinctly recog-
nised from a distance; thus forming to the eye aerial
images reflecting the form of the bottom of the ocean. A
still more remarkable effect of the cooling influence of shoals
is shewn sometimes in the higher regions of the atmosphere.
At sea and in very clear weather, clouds are often seen sus-
pended above the site of sand banks or shoals, as well as
over low coral or sandy islands. Their bearings may be
THE OCEAN. 303
taken from a distant ship by the compass, precisely as that
of a high mountain or a solitary peak.
Although the surface of the ocean is less rich in animal
and vegetable forms than that of continents, yet when its
depths ate searched, perhaps no other portion of our planet
presents such fulness of organic life. Charles Darwin, in
the agreeable journal of his extensive voyages, justly remarks,
that our land forests do not harbour so many animals as the
low wooded regions of the ocean, where the sea- weed rooted
to the shonls, or long branches of fuci detached by the force of
waves and currents, and swimming free upborne by air-cells,
unfold their delicate foliage. The application of the micros-
cope still farther increases our impression of the profusion
of organic life which pervades the recesses of the ocean, since
throughout its mass we find animal existence, and at depths
exceeding the height of our loftiest mountain chains, the
strata of water are alive with polygastric worms, cyclidise,
and ophrydinse. Here swarm countless hosts of minute
luminiferous animals, mammaria, Crustacea, peridinea, and
ciliated nereides, which, when attracted to the surface by
particular conditions of weather, convert every wave into
a crest of light. The abundance of these minute crea-
tures, and of the animal matter supplied by their rapid
decomposition, is such, that the sea water itself becomes
a nutritious fluid to many of the larger inhabitants of the
ocean.
If all this richness and variety of animal life, containing
some highly organised and beautiful forms, is well fitted to
afford not only an interesting study, but also a pleasing ex-
citement to the fancy, the imagination is yet more deeply,
I might say more solemnly, moved by the impressions of th«
boundless and immeasurable which every sea-voyage affords.
VOL. I. Y
SO 4 PHYSICAL GEOGRAPHY.
He who, awakened to the inward exercise of thought, delights
to build up an inner world in his own spirit, fills the wide
horizon of the open sea with the sublime image of the infinite ;
his eye dwells especially on the distant sea line where air and
water join, and where stars arise and set in ever renewed
alternation : in such contemplations there mingles as with
all human joy, a breath of sadness and of longing.
A peculiar predilection for the sea, and a grateful recol-
lection of the impressions which, when viewed within the
tropics, either in the calm of peaceful nights or in moments
of tumultuous agitation, it has left upon my mind, have alone
induced me to allude to the individual enjoyment afforded
by its contemplation, before I proceed to other and more
general considerations. Contact with the ocean has un-
questionably exercised a beneficial influence on the culti-
vation of the intellect and formation of the character of many
nations, on the multiplication of those bonds which should
unite the whole human race, on the first knowledge of the
true form of the earth, and on the pursuit of astronomy
and of all the mathematical and physical sciences. This
beneficial influence, enjoyed by the dwellers on the Medi-
terranean and on the shores of South- We stern Asia, was
long limited to them ; but since the sixteenth century it
has spread far and wide, extending to nations living even
in the interior of continents. Since Columbus was " sent to
unbar the gates of ocean" (as the unknown voice said to
him in a dream on his sick-bed near the River Belem), (374)
man has boldly adventured into intellectual as well as geo-
graphical regions before unknown to him.
"We proceed to the second covering of our planet, its
exterior and universally diffused envelope, the aerial ocean,
THE ATMOSPHEllE. METEOROLOGY. 305
at the bottom or on the shoals of which we live. The
atmosphere presents six classes of phsenomena which manifest
the most intimate connection with each other. These arise
from its chemical composition ; the variations in its transpa-
rency, polarisation, and colour ; its density or pressure ; its
temperature ; its humidity ; and its electric tension. The
atmosphere contains, in the form of oxygen, the first element
of the physical life of animals ; and we may here notice another
benefit scarcely less important, of which it is the instrument;
the air is the " conveyer of sound ;" the channel of the com-
munication of ideas, the indispensable condition of all social
life. The earth, deprived of its atmosphere, as we believe
our moon to be, presents to our imagination the idea of a
soundless desert.
Since the beginning of the present century, the relative
proportion of the constituents of the accessible strata of the
atmosphere has been the object of researches, in which 8 a,y-
Lussac and myself took an active part : but the chemical
analysis of the atmosphere has only very recently attained a
high degree of perfection, through the meritorious labours of
Dumas and Boussingault by new and more accurate methods.
According to this analysis a volume of dry air contains 20.8
parts of oxygen and 79.2 of nitrogen, besides from two to
five ten-thousandth parts of carbonic acid gas, a still smaller
quantity of carburetted hydrogen, (375) and, according to the
important experiments of Saussure and of Liebig, traces of
ammoniacal vapours, (376) which furnish to plants the azote
they contain. Some observations of Lewy have rendered it
probable that the quantity of oxygen varies slightly, but per-
ceptibly, in different seasons of the year, and over the sea or
in the interior of continents. It is quite a conceivable case
306 PHYSICAL GEOGRAPHY.
that variations which microscopic animals may occasion in
the quantity of oxygen held in solution in the water may entail
corresponding variations in the strata of air immediately in
contact with it. (3?7) The air which Martins collected on the
Faulhorn at a height of 8226 Trench feet had not less
oxygen than the air at Paris. (378)
The admixture of carbonate of ammonia in the atmosphere
may have been older than the presence of organic life on the
globe. The sources from whence the atmosphere may derive
carbonic acid are manifold. (379) We may name first the
respiration of animals, who obtain the carbon which they
exhale from vegetable food, the vegetables receiving it from
the atmosphere. Other sources are, the interior of the earth
in districts of extinct volcanoes and thermal springs ; and the
deopmposition of the small portion of carburetted hydrogen
existing in the air by the electric discharges of clouds, which
are much more frequent within the tropics than in our
climates. With the above-mentioned substances, which we
find to be proper to the atmosphere at all elevations within
our reach, are accidentally associated others, especially in
dose vicinity to the ground, which, as miasma and pesti-
lential emanations, sometimes exercise a dangerous influence
on animal organization. Although the chemical nature of
these has not yet been ascertained by direct analysis, yet the
existence of such deleterious local admixtures may be
inferred, both from a consideration of the processes of decay
which the vegetable and animal substances with which our
globe is covered are perpetually undergoing, and from combi-
nations and analogies belonging to the domain of pathology.
Ammoniacal and other vapours containing azote, sulphuretted
hydrogen, and even combinations analogous to the ternary
THE ATMOSPHE11E. METEOROLOGY. 307
and quaternary bases of the vegetable kingdom, (38°) may
produce miasma which, under many forms and conditions
(and by no means exclusively on wet marshy grounds, or
on coasts covered with decaying mollusca and low bushes o(
mangrove and avicennia) may generate agues and typhus
fever. At certain seasons of the year, fogs having a peculiar
smell remind us of such adventitious and unwelcome
mixtures in the lower portions of the atmosphere. Winds
and ascending currents, caused by the heating of the
ground, may sometimes carry up even solid substances when
reduced to fine powder. The sand which creates an ob-.
scurity in the air over a wide area, and falls on the Cape
Yerd Islands, to which attention was directed by Darwin,
was found by Ehrenberg to contain innumerable siliceous-
shelled infusoria.
As principal features of a general descriptive picture of
the atmosphere, we may distinguish —
1. Variations of atmospheric pressure ; those horary
fluctuations which within the tropics occur with such
regularity, and are so distinctly marked : they form a kind of
atmospheric tide, which, however, cannot be attributed to
the attraction of the Moon, (381) and which differs greatly
at different seasons, latitudes, and elevations.
2. Climatic distribution of heat, dependent on the
relative position of transparent and opaque masses (the fluid
and solid portions of the surface of the globe), and on the
hypsometric configuration of continents. These determine
the geographical position and the curvature of the isothermal
lines (or lines of equal mean annual temperature), both in a
horizontal and a vertical direction, or on uniform or
different levels.
<508 PHYSICAL GEOGRAPHY.
3. The humidity of the atmosphere. The quantitative
relations of the humidity depend on the proportion between
the terrestrial and oceanic surfaces ; on the distance from the
Equator, and the height above the sea ; on the form in which
the aqueous vapour in the atmosphere is precipitated;
and on the connection of these precipitations with changes
of temperature and with the direction and succession of
winds.
4. The electric tension of the atmosphere ; of which
the primary source, when the sky is serene, is still much
contested. Under this head we have to consider the relation
of ascending vapour to the electric charge and form of
clouds at different periods of the day and year ; the influence
of cold and warm zones of the earth, and of low or elevated
plains; the frequency or infrequency of thunder-storms,
their periodicity, and their formation in summer and winter ;
and the causal connection of electricity with the exceedingly
rare occurrence of night hail, and with the phsenomena of
water-spouts and of columns of sand, investigated with much
ingenuity by Peltier.
The horary variations of the barometer, which under the
tropics present two maxima (at 9 or 9J A.M., and at
10J or lOf P.M.) and two minima (at 4 or 4J A.M.
and 4 A.M., which are nearly the hottest and the coldest
hours of the day), were long the object of my most careful
daily and nightly observation. (382) Their regularity is such,
that, in the day time especially, we may infer the hour from
the height of the column of mercury, without being in error
on an average more than fifteen or seventeen minutes. In
the torrid zone of the New Continent, I have found the regu-
ATMOSPHERIC PRESSURE. 309
larity of .this ebb and flow of the aerial ocean undisturbed
either by storm, tempest, rain, or earthquake, both on the
coasts, and at elevations of nearly 13000 English feet above
the sea, where the mean temperature sinks to 7° Cent.
(44°. 6 Eah.) The amount of horary oscillation decreases
from the Equator to 70° N. lat. (where we have very accu-
rate observations made by Bravais (383) at Bosekop), from
1.3-2 to 0.18 French lines (0.117 to 0.016 English inches).
It has been supposed that much nearer to the pole the mean
height of the barometer is really less at ] 0 A.M. than at
4 h. P.M., so that the hours of maximum and minimum are
inverted ; but this can by no means be concluded from Parry's
observations at Port Bowen in 73° 14' N.
Owing to the effect of the ascending current, the mean
height of the barometer is rather less at the equator and ge-
nerally under the tropics, than in the temperate zone, (384) and
it appears to reach its maximum in Western Europe in the
parallels of 40° to 45°. If with Kamtz we combine, by
isobarometric lines, those places which present the same
mean difference between the monthly extremes of the ba-
rometer, we obtain curves whose inflections and geographic
positions furnish important conclusions respecting the in-
fluence which the form of the land and the distribution of
land and sea exercise on the oscillations of the atmosphere.
Hindostan, with its lofty mountain chains and triangular
peninsulas, — the eastern coast of the New Continent,
where the warm current of the Gulf Stream is deflected
to the east by the banks of Newfoundland, — shew greater
isobarometric fluctuations than do the West Indies and
Western Europe, Pievailing winds exercise a principal
310 PHYSICAL GEOGRAPHY.
influence on the diminution of the pressure of the atmo-
sphere ; in accompaniment with which, according to Daussy,
as we have already noticed, the mean level of the sea 13
raised. (385)
As the most important fluctuations of atmospheric pres-
sure, whether regular and periodical, or irregular or acci-
dental and then often violent and dangerous, (386) havefor their
principal cause, like all other phsenomena of weather, the
heating power of the sun's rays, — it has long been customary
(partly as proposed by Lambert) to compare the direction of
the wind with the height of the barometer, and with changes
of temperature and the increase or decrease of moisture.
Tables of atmospheric pressure accompanying different
winds, which have received the name of barometric
windroses, afford a deep insight into the mutual rela-
tion of meteorological phsenomena. (387) Dove, with ad-
mirable sagacity, has recognised in the " law of rotation" in
both hemispheres, which he has propounded, the cause of
many important processes and extensive movements in the
aerial ocean. (388) The difference of temperature between
the equatorial and the polar regions of the globe produces
two opposite currents; one in the higher portion of the
atmosphere, the other near the surface of the earth. The
difference between the rotatory velocity at the poles and at
the equator causes the air flowing from the poles to undergo
an easterly, and the equatorial current a westerly deflection :
on the opposition of these two currents, on the place where
the upper one descends to the surface of the earth, and on
the alternate displacement of one by the other, depend the
principal phenomena of atmospheric pressure, of the heating
ATMOSPHERIC PRESSURE. 311
and cooling of different strata of the air, of aqueous precipi-
tations, and even, as Dove has truly represented, the formation
of clouds and their shape and aspect. Thus the particular
form of cloud, which is often a characteristic and animating
feature of the landscape, announces the processes which are
taking place in the upper regions of the air ; and when the
air is calm, the clouds on a hot summer's day will sometimes
present a " projected image" of the diversities of form of the
heat- radiating surface of the Earth beneath them.
In parts of the globe where radiation acts on very ex-
tensive continental and oceanic surfaces in certain relative
positions to each other, as between the east coast of Africa and
the west coast of the Peninsula of India, its effects are shewn
in the monsoons of the Indian Seas (389) — the Hippalos
of the Greek navigators : as the direction of the monsoons
varies with the declination of the Sun, their periodical cha-
racter was early recognised and turned to the use of man.
In the knowledge of the monsoons, — which has doubtless ex-
tended for ages over both Hindostan and China, and among
the Arabs to the west and the Malays to the east, — as well
as in the still more ancient and more general knowledge of
land and sea breezes, there lay, as it were enveloped and con-
cealed, the hidden germ of that meteorological science which
is now making such rapid progress. The long chain of
magnetic stations extending from Moscow to Pekin through
the whole of Northern Asia, and which have also for their
object the investigation of meteorological relations, will
furnish data of great importance towards the investigation
of the Law of the Winds. Eor example, the comparison
of stations so many hundred miles apart will determine,
whether the same east wind blows from the elevated desert
312 PHYSICAL GEOGRAPHY.
plains of Gobi to the interior of Russia, or whether the
direction of the current originates in the middle of the chain
of stations by a descent of the air from the upper regions.
"We shall thus learn in the strictest sense " where the wind
comes from/' If at the present moment we take a result
on this point exclusively from stations where observations
have now been made for above twenty years, we find (ac-
cording to Wilhelm Mahlmann's most recent and careful
calculation), that in the middle latitudes of the temperate
zone, and in both continents, the prevailing direction of the
wind is west south-west.
We have gained a clearer insight into the distribution of
heat in the atmosphere, since the attempt has been made to
connect graphically by lines those points, where accurate
observations have indicated equality of mean annual, mean
summer, or mean winter temperature. The system of
Isothermal, Isotheral, and Isochimenal lines, which I fust
employed in 1817, if gradually perfected by the united
efforts of investigators, may perhaps prove one of the chiei
foundations of a Comparative Climatology. It is thus
that researches on terrestrial magnetism have become a
science, from the period when partial results were combined
in a graphic form in lines of equal Declination, equal Incli-
nation, and equal Intensity.
The expression climate, taken in its most general sense,
signifies all those states and changes of the atmosphere which
sensibly affect our organs : temperature, humidity, variation
of barometric pressure, a calm state of the air or the effects
of different winds, the amount of electric tension, the purity
of the atmosphere or its admixture with more or less dele-
terious exhalations, and lastly the degree of habitual trans-
CLIMATOLOGY. 313
parency of the air and serenity of the sky, which has an
important influence not only on the organic development of
plants and the ripening of fruits, but also on the feelings
and the whole mental disposition of man.
If the whole surface of the earth consisted either of a
homogeneous fluid mass, or of strata of rock perfectly alike
in colour, density, and smoothness, and of equal capacity
both for the absorption of the sun's rays, and for radiat ing
heat through the atmosphere into space, the isothermal;
isotheral, and isochimenal lines would all be parallel to the
equator. In this hypothetical condition of the earth's
surface, the power of absorption and emission of light and
heat would, under equal latitudes, be every where the same.
From this mean, and, as it were, primitive condition, which
neither excludes currents of heat in the interior of the globe
or in its external covering, nor the propagation of heat
by atmospheric currents, the mathematical consideration of
climate proceeds. Whatever alters the power of absorption
and of radiation, in any of the several parts of the earth's
surface under the same parallel of latitude, causes inflections
in the isothermal lines.
The progress of climatology has been remarkably favoured
by the circumstance that European civilisation has extended
over two opposite coasts, having passed from our western
shores to a coast on the other side of the Atlantic valley having
an eastern aspect. When, after the ephemeral colonisation
from Iceland and Greenland, the British formed the first
permanent settlements on the coast of the United States of
America, and the colonists (whose numbers were rapidly
augmented by the effects of religious persecution, fanaticism,
314 PHYSICAL GEOGRAPHY.
and the love of liberty,) spread over the whole extent from
North Carolina and Virginia to the banks of the St. Law-
rence, they were astonished at the degree of winter cold which
they had to endure, when compared with the climates of Italy,
France, and the British Islands, in corresponding parallels of
latitude. But, however well fitted to awaken attention, the
comparison bore no fruit until it could be based on nu-
merical results of mean annual temperature. If between
58° and 30° of north latitude, we compare Nain on the
coast of Labrador with Gottenburg, Halifax with Bor-
deaux, New York with Naples, and St. Augustin in Florida
with Cairo, we find the differences of mean annual tempera-
ture under equal latitudes, in Eastern America and Western
Europe, commencing with the northernmost pair of stations,
and proceeding southwards, successively 11°.5, 7°.7, 3°.8,
and almost 0° Cent. (20°.7, 13°.8, 6°.8, and almost 0°Fah.)
The gradual diminution of the differences in this series,
which extends over twenty-eight degrees of latitude, is
striking. Farther to the south, under the tropics, the iso-
thermal lines in both parts of the world are every where
parallel to the equator. "We see from the above examples,
that the questions often asked in society, — how many degrees
America (without distinction of its eastern or western coast),
is colder than Europe? — or how much the mean annual
temperature of Canada and the United States is lower than
that of the corresponding latitudes in Europe ? — have, when
thus generally expressed, no definite meaning. The differ-
ence is not the same under different parallels ; and unless we
compare separately the winter and the summer temperatures
of the opposite coasts, we shall not be able to form any clear
CLIMATOLOGY. 315
idea of their climatic relations, as influential on agriculture
and other industrial pursuits, and on the comfort and well-
being of man.
In enumerating the causes which exercise a disturbing
influence on the form of the isothermal lines, I have distin-
guished between those which raise and those which depress
the temperature. To the first belong, — the vicinity of a
western coast in the temperate zone; a divided or inter-
sected configuration of the land, with projecting peninsulas,
and deep re-entering bays and inland seas ; aspect, or the
position *of the land relatively to a sea free from ice ex-
tending within the polar circle, or to a considerable mass
of continental land situated beneath the equator, or at
least within the torrid zone; prevalence of southerly and
westerly winds on the western side of a continent, in the
temperate zone of the northern hemisphere ; chains of
mountains acting as screens or protecting walls against
winds from colder regions; infrequency of swamps or
marshes, which retain the ice in spring and early summer;
absence of woods on a dry sandy soil ; constant serenity
of sky during the summer months ; and lastly, the vicinity
of an oceanic current, bringing water of a higher tempera-
ture than that of the surrounding sea.
Among the cooling causes which modify the mean
annual temperature, I consider elevation above the sea level,
especially when not forming an extensive table land; the
vicinity of an eastern coast in the higher and middle lati-
tudes ; the compact and massive form of a continent, having
a coast line little varied by indentations ; an extension of
the land in the direction of the pole far into the frozen
regions (there being no intervening sea free from ice during
316 PHYSICAL GEOGEAPHY.
the winter) ; a geographical position in which the tropical
portions of the same meridians are occupied by sea, implying
the absence under those meridians of extensive tropical land
powerfully heated by the sun's rays, and giving out great
heat by radiation; chains of mountains which, by their
direction and precipitous form, impede the access of warm
winds; the neighbourhood of isolated peaks, causing the
descent of currents of cold air on their declivities ; extensive
forests, preventing the heating of the ground by the direct ef-
fect of the sun's rays, and, by means of the vital organic action
of their leafy appendages, causing great evaporation, while,
by the extension of those organs they increase the quantity
of surface cooled by radiation, thus operating in a threefold
manner, by shade, evaporation, and radiation; extensive
marshes, which, in the north, form a kind of subterranean
glacier in the plains, lasting until the middle of summer ;
a cloudy summer sky, or frequent mists, which impede the
action of the sun's rays ; and lastly, a very serene and clear
winter sky, favouring the escape of heat by radiation. (39°)
The inflections of the isothermal lines are determined by
the joint action, or total effect of the simultaneous operation,
of all the disturbing causes, whether belonging to those
which raise or to those which depress the temperature, but
especially by the relative extent and configuration of the
continental and oceanic masses. Local perturbations occa-
sion the convex and concave summits of the isothermal
curves. Since there are different orders of disturbing causes,
each should first be viewed singly ; and afterwards, in order
to learn their total effect on the form of the isothermal line
in the part of the earth under consideration, we must consider
their joint influence; and the operation of each, in modi-
CLIMATOLOGY.
317
fying, destroying, or enhancing the effect of others, as small
undulatory movements which encounter and intersect each
other are known to do. Such is the spirit of the method
by which I persuade myself it will some day be possible to
combine by empirical laws, numerically expressed, vast series
of apparently insulated facts, and to manifest their reciprocal
dependence.
The trade winds (which are easterly winds blowing
within the tropics), are the occasion of the west and west-
south-west winds which prevail in both the temperate
zones. These are of course land winds to eastern coasts,
and sea winds to western coasts. The surface of the ocean
not being susceptible of being cooled in the same degree as
that of the land, by reason of the mass of its waters, and the
tendency of its particles to sink immediately they are cooled
and to be replaced by cooler from below, it follows that,
where easterly winds prevail, western coasts should be warmer
than eastern coasts, except a counteraction exists in oceanic
currents. Cook's young companion on his second voyage of
circumnavigation, the ingenious George Porster, to whom I
em indebted for the lively interest which prompted me to
undertake distant travels, was the first who distinctly called
attention to the difference of temperature between the
eastern and western coasts of the two continents; and
to the similarity of temperature, in the mean latitudes, of
the west coast of America and the west coast of Europe. (391)
Even in more northern latitudes, exact observations shew
a striking difference between the mean annual temperatures
of the east and the west coasts of America. Nain, in
Labrador, in 57° 10' N. lat., has a mean annual temperature
of _3°.8 Cent. (25°.2 Fah.), or 6°.8 Fah. below the freezing
318 PHYSICAL GEOGRAPHY.
point; while Sitka, on the west coast of America, in
57° 3' N. lat,,- has a mean temperature of 6°.9 Cent. (44°.4
Fall.), being 12°.4 Fall, above the freezing point. At Nain
the mean summer temperature hardly attains 6°. 2 Cent.
(43°.2 Fah.), while at the Sitka it is 13°.8 Cent. (56°.8 Fall.)
Pekin, on the east coast of Asia, in lat, 39° 54', has a mean
annual temperature of 11°.3 Cent. (52°.3 Fah.), being more
than 9° Fah. lower than that of Naples, which is in a rather
more northern latitude. The mean winter temperature of
Pekin is at least 3° Cent. (5°.4 Fah.) Mow the freezing
point ; while in Western Europe, the winter temperature of
Paris, in lat. 48° 50', is fully 3°.3 Cent. (6°.0 Fah.) above
the freezing point. The mean winter temperature of Pekin
is 2°.5 Cent. (4°.5 Fah.) lower than that of Copenhagen,
situated seventeen degrees farther to the north.
I have already alluded to the slowness with which the
great mass of water in the ocean follows the variations of
temperature in the atmosphere, and the consequent influence
of the sea in equalizing temperatures ; it moderates both the
asperity of winter and the heat of summer : hence arises a
second important contrast, — that between insular or littoral
climates (enjoyed also in some degree by continents whosk
outline is broken by peninsulas and bays), and the climate
of the interior of great masses of solid land. Leopold von
Buch was the first writer who entered fully into the subject
of this remarkable contrast, and the varied phenomena re-
sulting from it; its influence on vegetation and agriculture, —
on the transparency of the atmosphere and serenity of the
sky, — on the radiation from the surface, — and on the height
of the limit of perpetual snow. In the interior of the Asiatic
continent, Tobolsk, Barnaul on the Obi, and Irkutsk, have
CLIMATOLOGY. 319
summers which, in mean temperature, resemble those of
Berlin and Munster, and that of Cherbourg in Normandy,
*nd during this season the thermometer sometimes re-
mains for weeks together at 30° and 31° Cent. (86° or
87°.8 Pah.) ; but these summers are followed by winters in
which the coldest month has the severe mean temperature
of —18 to —20 Cent. (— 0°.4 to + 4°.0 Fah.) Such con-
tinental climates do indeed deserve the name of excessive
which they received from Buffon, and the inhabitants
of those countries almost seem condemned in Dante's
words, (392)
" A sofferir tormenti caldi e geli."
I have in no part of the earth, not even in the Canary
Islands, in Spain, or in the south of France, seen more
magnificent fruit, especially grapes, than at Astrachan.
near the shores of the Caspian, in lat. 46° £1'. With
a mean annual temperature of about 9° Cent. (48°
Fah.), the mean summer temperature rises to 21°. 2 Cent.
(70°. 2 Fah.), which is that of Bordeaux; while not only
there, but also still more to the south, at Kislar at the
mouth of the Terek (in the latitude of Avignon and Eimini),
the thermometer sometimes falls in winter to — 25° or — 30°
Cent. (—13° to —22° Fah.)
Ireland, Guernsey and Jersey, the peninsula of Brittany,
the coast of Normandy and that of the south of England, all
present, by the mildness of their winters, and by the low tem-
perature and clouded skies of their summers, the most
striking contrast to the continental climate of the interior of
eastern Europe. In the north-eastern part of Ireland, in lat.
54° 56', under the same parallel as Konigsberg, the myrtle
VOL. r. z
820 PHYSICAL GEOGRAPHY.
flourishes as luxuriantly as in Portugal. The mean tern-
perature of the month of August, in Hungary, is 21° Cent.
(69°.8 Pah.) ; in Dublin, which is situated on the same
isothermal line (or line of equal mean annual temperature)
of 9 J° Cent. (49°.2 flab.), it is barely 16° Cent. (60°.8 Fah.) ;
the mean winter temperatures of the two stations being
2°.4 Cent. (27°.7 Fah.) at Buda, and 4°.3 Cent. (39°8 Fah.)
at Dublin. The winter temperature of Dublin is 2° Cent.
(3°.6 Fah.) higher than that of Milan, Pavia, Padua, and of
the whole of Lombardy, although they enjoy, on the mean
of the whole year, a temperature of at least 12°. 7 Cent.
(54°.8 Fah.) Stromness, in the Orkneys, not half a de-
gree south of Stockholm, has a winter temperature of 4°
Cent. (3 9°. 2 Fah.), being nearly as mild as London, and
milder than Paris. Even in the Faroe Islands, in lat. 62°,
under the favouring influences of the sea and of westerly
winds, the inland waters never freeze. On the lovely coast
of Devonshire, where Salcombe Bay has been called, on ac-
count of its mild climate, the Montpellier of the North, the
Agave Mexicana has been seen to blossom in the open air,
and orange trees trained against espaliers, and only slightly
protected by mats, have borne fruit. There, and at Pen-
zance and Gosport, as well as at Cherbourg in Normandy, the
mean winter temperature is above 5°.5 Cent. (41°.8 Fah.),
that is, only 1°.3 Cent. (2°.4 Fah.) lower than that of
Montpellier and Florence. (393) Hence we perceive in what
a variety of ways the same mean annual temperature may bo
distributed in the different seasons of the year, and the im-
portant influence of this distribution, whether considered in
reference to vegetation, to agriculture, to the ripening of
fruits, or to the comfort and well-being of man.
CLIMATOLOGY. 821
We have just seen, that the lines which I have called
isochimenals and isotherals (or lines of equal icinter and
equal summer temperature), are by no means parallel with
the isothermals, or lines of equal annual temperature. If,
however, in countries where the myrtle grows wild, and the
snow does not continue on the ground during winter, tho
temperature of summer and autumn is barely sufficient to
ripen apples thoroughly, — and if the vine (to produce drink-
able wine) avoids islands, and in almost all cases proximity
to coasts, — the reason is by no means exclusively the low-
summer temperature of such situations, shewn by the
thermometer suspended in the shade: it is also to be
sought in a difference which has been hitherto but little
considered, although known to be most actively influential in
other classes of phenomena (for example, in the bursting into
flame of a mixture of hydrogen and chlorine), — I mean the
difference between direct and diffused light ; or that which
prevails when the sky is clear, and when it is veiled by cloud
or mist. I long since (394) attempted to call the attention
of physicists and vegetable physiologists to this difference,
and to the heat, unmeasured by thermometers, which is
locally developed in the vegetable cells by the action of
direct light.
If we form a thermic scale of different kinds of cultiva-
tion, (395) beginning with that which requires the hottest
climate, and proceeding successively from vanilla, cacoa,
spices, and cocoa nuts, to pine apples, sugar cane, coffee, fruit-
bearing date trees, cotton, citrons, olives, sweet chestnuts, and
vines producing drinkable wine, an exact consideration of
their various limits, both on plains and on the declivities of
mountains, will teach us that in this respect other climatic re-
322 PHYSICAL GEOGRAPHY.
lations than those of mean animal temperature must be sought.
Taking only one example, the cultivation of the vine, —
the production of drinkable wine (396) requires not only a
mean annual temperature of above 9 J° Cent, (or 49 °.2 Fall.),
but also a winter temperature of above 0°.5 Cent. (32°. 8
Pah.), followed by a mean summer temperature of at least
18° Cent. (64°.4 Pah.) At Bordeaux, in the valley of the
Gaioime, in lat. 44° 50', the mean temperature of
the year, the winter, the summer, and the autumn, are
respectively 13°.8, 6°.2, 21°.7, and 14°.4 Cent. (56°.8,
43° 2, 71°.0 and 58°.0 Pah.) On plains in the vicinity of
the Baltic in lat. 52J°, where a wine is produced which
though it is used can scarcely be called drinkable, these num-
bers are respectively 8°.6, — 0°.7, 17°.6, and 8°.6 Cent.
(47°.5, 30°.8, 63°.7, and 47°.5 Pali.) If it should appear
strange that these great differences in the influence of cli-
mate on the production of wine do not shew themselves still
more markedly in the indications of thermometers, it should
be remembered that an instrument suspended in the shade,
and carefully protected from the direct rays of the sun, and
from nocturnal radiation, cannot shew at all seasons of the
year, and during all the periodical changes of temperature,
the true heat of the surface of the ground, which receives
the whole effect of the sun's rays.
The relation of the mild, equable, littoral clim,ate of the
peninsula of Brittany, to the colder winters and hotter sum-
mers of the more compact mass of the rest of France, re-
sembles, to a certain degree, the relation of the climate of
Europe generally to that of the great continent of Asia,
of which it is the western peninsula. Europe owes its mildei
climate to its intersected form and deeply indented coast, —
CLIMATOLOGY. 323
to its exposure to the prevailing west winds which have
blown across the ocean, — to the sea free from ice which
separates it from the polar regions, — and lastly, to the
existence and position of Africa, with its wide extent of
tropical land favourable to the ascending current, while the
equatorial region to the south of Asia is for the most part
covered by the ocean. The European climate would there-
fore become colder, (397) if Africa were to be overflowed by
the ocean, — or if the fabulous Atlantis were to rise from the
waves, and connect the two continents, — or, finally, if either
the Gulf stream were to cease to extend its warming in-
fluence to the Northern Sea, or if a tract of land were to be
elevated by volcanic forces between the Scandinavian penin-
sula and Spitzbergen. If in Europe the mean annual
temperature decreases as we proceed easterly on a parallel
of latitude, from the Atlantic coast of Prance through
Germany, Poland, and Eussia, to the chain of the Ural ; —
the principal cause of this phsenomenon is to be sought
in the form of the continent being gradually less inter-
sected, and becoming more compact and extended, — in the
increasing distance from the sea, — and in the feebler influence
of westerly winds. Beyond the Ural, westerly winds blow-
ing over wide expanses of land covered during several
months with ice and snow, become cold land winds. It is
to such circumstances of configuration and of atmospheric
currents that the cold of western Siberia is due, and by no
means to a great elevation of the surface above the level of
the sea, as anciently assumed by Hippocrates and Trogus
Pompeius, (398) and still related by travellers of some celebrity
in the eighteenth century.
If from differences of temperature at a uniform level, we
324 PHYSICAL GEOGEAPHY.
proceed to the inequalities of the form of the surface of
our planet, we have to consider mountains, either in re-
ference to their influence on the climate of neighbouring
lowlands, or to the climatic effects of their hypsometric re-
lations on their own summits, which often spread out into
elevated plains. Mountain chains divide the surface of the
earth into different basins, which are sometimes narrow and,
as it were, walled in, forming circular vail eys or calderas, which
(as in Greece and in parts of Asia Minor) occasion climates
locally individualised in respect to .warmth, humidity,
atmospheric transparency, and frequency of winds and
tempests. These circumstances have at all times exer-
cised a powerful influence on natural products, and on
cultivation; as well as on manners, institutions, and the
feelings with which neighbouring tribes mutually regard each
other. The character of geographical individuality, if we
may be permitted to use the expression, reaches its maximum
in countries where the variety of the form of the ground io
the greatest possible, both in the vertical and the horizontal
direction, both in relief and in the configuration of the coast
line. The greatest contrasts to this variety of ground are
found in the steppes of Northern Asia, in the grassy plains
(savannahs, llanos, and pampas)- of the new continent, in the
heaths of Europe, and in the sandy and stony deserts of Africa.
The law of the decrement of heat with increasing eleva-
tion in different latitudes has a most important bearing on
meteorological processes, on the geography of plants, on the
theory of terrestrial refraction, and on the different hypo-
theses on which the height of our atmosphere is estimated.
In the many mountain journeys which I have undertaken,
both within and beyond the limits of the tropics, the invest!-
CLIMATOLOGY. 325
gation of this law'has always been an especial object of my
researches. (399)
Since we have obtained a somewhat more exact knowledge of
the distribution of heat on the surface of the earth,— namely,
of the inflections of the isothermal, isotheral, and isochim-
enal lines, and of their unequal distances apart in the
different systems of temperature of Eastern and Western
Asia, of central Europe, and of North America, — it is no
longer admissible to ask as a general question, to what fraction
of the mean annual or mean summer temperature a change of
one degree of geographical latitude, taken in a particular
meridian, corresponds. In each system of isothermal lines
of equal curvatvfre, there reigns an intimate and necessary
connection between three elements ; — the decrease of heat in
a perpendicular direction from below upwards, — the variation
of temperature corresponding to a change of one degree of
geographical latitude, — and the relation which exists between
the mean temperature of a station on a mountain, and the
latitude of a point situated at the level of the sea.
In the system of Eastern America, the mean annual tem-
perature varies from the coast of Labrador to Boston 0°.88
Cent. (1°.58 Pah.) for each degree of latitude ; from Boston
to Charleston 0°.95 Cent. (1°.71 Pah.) ; from Charleston to
the tropic of Cancer in the island of Cuba, the variation
diminishes, being only 0°.66 Cent. (1°.19 Pah.) Within
the tropic the diminution decreases to such a degree that
from Havannah to Cumana, the variation is not more than
0°.20 Cent. (0°.36 Pah.) for each degree of latitude.
In the system of isothermal lines of central Europe, the
case is quite otherwise. Between the parallels of 38° and
71°, I find the decrease of temperature to be with considera-
326 PHYSICAL GEOGKAPHY.
qle uniformity 0°.5 Cent. (0°.9 Fall.) for one degree of
latitude. But as a decrease of temperature of 1°.0 Cent.
(l.°8 Fah.) corresponds to an increase of vertical elevation
of 480 to 522 French feet (512 to 556 English), it follows
that a difference of elevation of 240 to 264 French
feet (256 to 278 English) produces the same effect on the
annual temperature as a change of one degree of latitude.
The mean annual temperature at the Convent on the Great
St. Bernard, at the elevation of 7668 French (8173 English)
feet in lat. 45° 50', should therefore be found at the level of
the sea in lat. 75° 50'.
In that portion of the chain of the Andes which falls
within the tropics, observations, made by myself at various ele-
vations from the sea-level to a height of 18000 French feet
(19185 English), gave a decrease of temperature of l°Cent.
(1°.8 Fah.) for 576 French feet (614 English). My friend
Boussingault found, as a mean result, thirty years afterwards,
540 French feet (575 English). By a comparison of places
in the Cordilleras, at equal elevations above the level of the sea.,
but situated some on the declivities of mountains, and others
on extensive table lands, I found that the latter class of stations
shewed a higher annual temperature varying from 1°.5 Cent.
to 3° Cent. (2°.7 to 4°.2 Fah.) ; and the difference would be
still greater if it were not for the cooling effect of nocturnal
radiation. As the various climates are here placed successively
stage above stage, from the cacao plantations of the lowlands
to the limit of perpetual snow, and as the differences of tem-
perature in the course of the year are very small, we may^
obtain a tolerably accurate representation of the climates
experienced by the inhabitants of the large towns in the
Andes, by comparing them with the temperatures of parti-
LIMIT OF PERPETUAL SNOW. 827
cular months in the plains of Prance and Italy. While the
heat which prevails daily on the forest-covered banks of the
Orinoco is 4°.0 Cent. (7°.2 Fah.) greater than that of the
month of August at Palermo, we find on ascending the
chain of the Andes, at Popayan, (at an elevation of
5826 English feet), the mean temperature of the three
summer months at Marseilles ; at Quito, (at a height of
9541 English feet), that of the end of the month of May
at Paris; and, on the paramos, (at an altitude of 11510
English feet), where only dwarf Alpine bushes grow
though flowers are still numerous, that of the beginning of
April at Paris.
The ingenious Peter Martyr de Anghiera, one of the
friends of Christopher Columbus, seems to have been the
first to recognise (in the expedition undertaken in October
1510 by Rodrigo Enrique Colmenares) that the snow line
becomes always higher as the equator is approached. We
read in the fine work, entitled De rebus Ocean im (4()0) : —
" The river Gaira comes from a mountain (in the Sierra Ne-
vada of Santa Martha), which, according to the report of
Colmenares's travelling companions, is higher than any
mountain hitherto discovered ; doubtless it must be so, if in
a zone distant not more than 10° from the equinoctial line,
it yet retains snow permanently." The lower limit of per-
petual snow in a given latitude is the boundary line of the
snow which resists the effect of the summer ; it is the highest
elevation to which the snow line recedes in the course of
the whole year. We must distinguish between the limit
thus defined, and three other phenomena ; viz, the annual
fluctuation of the snow line ; the phsenomenon of sporadic
falls of snow ; and the existence of glaciers, which appear to be
328 PHYSICAL GEOGRAPHY.
peculiar to the temperate and cold zones, and on which,
since the immortal work of Saussure, a new light has of late
years been thrown by Venetz and Charpentier, and by the
meritorious arid intrepid perseverance of Agassiz.
We know only the lower and not the upper limit of
perpetual snow, for the highest mountains of the earth are
far from attaining to those strata of highly rarefied and ex-
cessively dry air, concerning which we may suppose, with
Bouguer, that they no longer contain vesicular vapour
capable of being converted into crystals of snow, and of thus
becoming visible. The lower limit of perpetual snow is not,
however, a mere function of the geographical latitude, or of
the mean annual temperature, nor is it even under the
equator as was long supposed, or even within the tropics,
that the snow line reaches its greatest elevation above the
level of the sea. The phsenomenon is a very complicated
one, depending generally on relations of temperature and
moisture, and on the peculiar shape of the mountains : if
these relations are subjected to a still more particular
analysis, which a great number of recent determinations
renders possible, (401) we shall recognise, as concurrent causes,
the differences of temperature in the different seasons of the
year, — the direction of the prevailing winds, and whether
they have blown over land or sea, — the degree of dryness
or of moisture of the upper strata of air, — the absolute
thickness of the accumulated mass of fallen snow, — the
relation of the height of the snow line to the total height of
the mountain, — the position of the latter in the chain of
which it forms a part, — the steepness of its declivities, — the
vioinity of other summits also covered with perpetual
snow, — the extent, position, and elevation of the plain from
LIMIT OF PERPETUAL SNOW. 329
which the snow-capped mountain rises, either solitarilf, or as
a portion of a group or chain, — and whether this plain may
be part of the sea coast, or of the interior of a continent,
whether wooded or grassy, of arid sand or rock, or, on the
contrary, wet and marshy.
Under the equator in South America, the height of the
snow line is equal to that of the summit of Mount Blanc in
Europe, and descends, according to recent measurements,
960 French feet (1023 English) lower in the highlands of
Mexico, in lat. 19° North; in the southern tropic, on the
contrary, in 14-V0 to 18° S. lat., it ascends, according to
Pentland, to an elevation of 2500 French (2665 English)
feet above that which it attains under the equator not far
from Quito, on Chimborazo, Cotopaxi, and Antisana ; this
ascent of the snow line does not take place in the eastern
part of the Cordilleras, but in the western and maritime
chain of the Andes of Chili. Dr. Gillies affirms that
even much farther to the south, on the declivity of the
volcano of Peuquenes (lat. 33°), he found the snow line
reach an elevation of between 2270 T. and 2350 T.
(14520 and 15030 English feet). The evaporation of the
snow in the excessively dry air of summer and under a
doudless sky is so powerful, that the volcano of Aconcagua,
north-east of Valparaiso, in S. lat. 32^-° (the elevation of
which was found by the Expedition of the Beagle to be
1400 feet above that of Chimborazo), was once seen free from
enow. (402) In an almost equal northern latitude (30° 45
to 31°) the snow line on the southern declivity of the
Himalaya lias an elevation of 12180 French feet (12982
English), which is nearly that which might have been con-
jecturally assigned to it from many combinations and com-
330 PHYSICAL GEOGRAPHY.
parisons with other mountain chains ; but on the northern
declivity, under the influence of the high lands of Thibet;
whose mean elevation appears to be about 10800 French
feet (11510 English), the snow limit attains a height of
15600 French feet (16630 English). This phenomenon
was long contested both in Europe and in India, and
I have developed my views respecting its causes on several
occasions since the year 1820 : (403) it is interesting in
another point of view besides the purely physical one,
for it has exercised an important influence on the mode
of life of numerous tribes ; meteorological processes in the
atmosphere either favour or forbid an agricultural or a pas-
toral life to the inhabitants of extensive tracts of continent.
As the quantity of moisture in the atmosphere increases
with the temperature, this element, so important for the whole
organic creation, varies with the hour of the day, the season
of the year, and the degree of latitude and of elevation. Our
knowledge of the hygrometric relations of the atmosphere
has been materially argumented of late years by the method
now so generally and extensively employed, of determining
the relative quantity of vapour, or the condition of moisture
of the atmosphere, by means of the difference of the dew
point and of the temperature of the air, according to the ideas
of Dalton and of Daniell, and by the use of the wet bulb
thermometer. Temperature, atmospheric pressure, and the
direction of the wind, have all a most intimate relation to
the atmospheric moisture so essential to organic life,
influence, however, of humidity on organic life, is less
consequence of the quantity of vapour held in solution und<
different zones, than of the natur* and frequency of the
aqueous precipitations which refresh \>M ground in the form of
HYGROMETRY. 831
\
dew, mist, rain, or snow. According to Dove, f404) in our
northern zone ' ' the elastic force of the vapour is greatest with
south-west, and least with north-east winds ; it diminishes
on the western side of the windrose, and rises on the eastern
side. On the western side of the windrose, the cold, dense,
and dry current represses the warm and light current con
taining an abundance of aqueous vapour, while, on the eastern
side, the contrary takes place. The south-west is the
equatorial current which has descended through the lower
current tc the surface of the earth ; the north-east is the
polar current prevailing undisturbed."
The agreeable and fresh verdure which many trees preserve
in districts within the tropics, where for from five to seven
months no cloud is seen on the vault of heaven, and no per-
ceptible dew or rain falls, proves that their leaves are
capable of drawing water from the atmosphere by a
vital process of their own, wliich perhaps is not simply
that of producing cold by radiation. The absence of rain in
the arid plains of Cumana, Coro, and Ceara (in North
Brazil), is contrasted with the abundance of rain which
falls in other places within the tropics ; for example, at the
Havannah, where, by the average of six years of observation
by Ramon de la Sagra, the mean annual quantity of rain
is 102 Parisian inches, which is four or five times as much
as falls at Paris or at Geneva. (405) On the declivities of
the chain of the Andes, the quantity of rain as well as
the temperature decreases with increasing elevation. (406)
My South American travelling companion, Caldas, found
that the annual quantity of rain at Santa Fe de Bogota, at
an elevation of nearly 8700 English feet, did not exceed
37 Parisian inches, little more than on some of the western
coasts of Europe. At Quito, Boussingault sometimes
332 PHYSICAL GEOGRAPHY.
saw Saussure's hygrometer recede to 26°, with a temperature
of 12° to 13° C. (53°.6 to 55°.4 Pah.) Gay-Lussac,
in his great aerostatic ascent, in a stratum of air 6600
French feet (7034 English) high, with a temperature of
4° C. (39°.2 Pah.) saw the same hygrometer at 25°.3. The
greatest degree of dryness which has yet been observed on
the surface of the globe in the lowlands is probably that
which Gustav Rose, Ehrenberg, and myself, found in
Northern Asia, between the valleys of the Trtysch and the
Obi. In the steppe of Platowskaia, after south-west winds
had blown for a long time from the interior of the continent,
with a temperature of 23°.7 C. (74°.7 Fall.), we found the dew
point — 4°.3 C. (24° Pah.); the air, therefore, contained only
sixteen parts in a hundred of the quantity of vapour required
for saturation. (407) Accurate observers, Kamtz, Bravnis, and
Martins, have in the last few years raised doubts concerning
the greater dryness of mountain air, which appears to follow
from the hygrometric measurements made by De Saussure and
myself in the higher regions of the Alps and of the Cordilleras.
The more recent observations referred to furnish a com-
parison of the strata of air at Zurich and on the Paulhorn ;
but the latter scarcely deserves the name of an elevated
mountain station. (408) The moisture by which, in the
tropical region of the paramos (near the part where snow
begins to fall, between 12000 and 14000 English feet of eleva-
tion,) some kinds of large-flowered myrtle-leaved alpine shrubs
are almost perpetually bathed, does not necessarily imply
the presence of a large absolute quantity of aqueous vapour
at that height ; it only proves, as do the abundant mists on
the fine plateau of Bogota, the frequency of aqueous precipi-
tations. At such elevations, with a calm state of the atmo-
sphere, mists arise and disappear several times in the course
ATMOSPHERIC CHANGES. 333
of an hour. These rapid alternations characterise the elevated
plains and paramos of the chain of the Andes.
The electricity of the atmosphere, whether considered
in the lower regions of the air or in the canopy of the clouds,
whether studied in its silent problematical diurnal march, or
in explosions in the lightning and thunder of the tern-
pest, shews itself in manifold relation to the phenomena
of the distribution of heat, — of the pressure of the atmosphere
and its disturbances, — of hydro-meteoric phenomena (or
watery precipitations), — and probably also of the magnetism
of the outer crust of the globe. It acts powerfully on the whole
animal and vegetable world, not only indirectly through the
agency of meteorological processes, the precipitations of
aqueous vapour, and the acid or ammoniacal combinations
occasioned by it, but also in a direct manner as an electric force
stimulating the nerves and promoting the circulation of the
organic juices. This is not the place to renew the discussion
concerning the proper source of atmospherical electricity when
the sky is clear. Its existence has been ascribed, sometimes
to the evaporation of impure fluids (impregnated with earths
or with salts), (409) sometimes to the growth of plants, (41°)
or to chemical decompositions taking place at the surface of
the earth, sometimes to the unequal distribution of heat in
the atmospheric strata, (411) and, lastly, sometimes, according
to Peltier's ingenious investigations, to the influence of a
constant charge of negative electricity in the terrestrial
globe. (412) The physical description of the universe,
limiting itself to the results given by electrometric observa-
tions, (particularly those made with the ingenious electro-
magnetic apparatus first proposed by Colladon), has only
334 PHYSICAL GEOGRAPHY.
to notice the incontestable increase of the tension of positive
electricity accompanying the increased elevation of the
station and the absence of neighbouring trees, (413) its
daily variations, which take place, according to Clarke's
experiments at Dublin, in more complicated periods than
those found by Saussure and myself, and its variations at.
different seasons of the year, at different distances from the
equator, and under different relations of continental or
oceanic surface.
The electric equilibrium is more rarely disturbed where
the aerial ocean rests on a liquid base, than where it rests
on land ; but it is very striking to notice in extensive seas
the influence which small groups of islands exercise on the
state of the atmosphere in occasioning the formation of storai9.
In fogs, and in the commencement of falls of snow, I have
seen the previously permanent vitreous electricity pass rapidry
into resinous, and the two alternate repeatedly, during long
series of experiments made both in the plains of the colder lati-
tudes and in the paramos of the Cordilleras, at elevations from
11000 to 15000 English feet under the tropics. The alter-
nate transition was quite similar to that shewn by the electro-
meter a short time before and during a thunderstorm. (414)
"When the vesicular vapour has condensed into clouds with
definite outlines, the electricity of the separate vesicles of
vapour passes to the surface of the cloud, and contributes to ilk-
crease the general electric tension of the exterior surface. (415)
According to Peltier's experiments at Paris, slate-grey clouds
have resinous, and white, rose, and orange-coloured clouds
have vitreous electricity. Thunder clouds not only envelop
the highest summits of the Andes, — (I have myself seen the
vitrifying effects of lightning on one of the rocky pinnacles
ATMOSPHERICAL ELECTRICITY. 335
which rise above the crater of the volcano of Toluca, at an
elevation of nearly 15300 English feet), — but they have also
been seen over the lowlands in the temperate zone at a
measured vertical elevation of 25000 (26650 English) feet.
On the other hand, the stratum of cloud in which thunder is
taking place sometimes sinks to a height of only 5000 or
even 3000 feet above the plain.
According to Arago's investigations, which are the most
complete and comprehensive that we yet possess on this
difficult portion of meteorology, the disengagement of light
(lightning) is of three kinds: the zigzag form, sharply
defined at the edges ; lightning without definite form, illumi-
nating at the same instant the whole cloud, which appeals
as it were to open and display its inner recesses; and
lightning in the form of balls of fire. (416j The duration
of the two first kinds is scarcely the thousandth part of a
second; but the globular lightning moves far more slowly,
its appearance lasting for several seconds. Recent observa-
tions confirm the phenomenon described by Nicholson and
Beccaria, in which, without any audible thunder or any indi-
cation of storm, isolated clouds remain stationary for
some time high above the horizon, and lightning pro-
ceeds uninterruptedly both from their interior and from
their margins : hailstones, drops of rain, and flakes of
snow, have also been seen to appear luminous with
electric light when there has been no thunder. In the
geographical distribution of thunder-storms, the Peru-
vian coast, where thunder and lightning are unknown. (417j
presents the most striking contrast to the rest of the torrid
zone, in which at certain seasons of the year storms take
place almost daily, four or five hours after the sun has reached
VOL. I. 2 A
336 PHYSICAL GEOGRAPHY.
its meridian altitude. According to the testimony of navi-
gators (Scoresby, Parry, Ross, and Franklin), as collected
by Arago, it is undoubted that in general in the high northern
regions, between 70° and 75° of latitude, electric explosions
are exceedingly rare. (418)
The meteorological portion of the description of nature,
which we are now concluding, shews thatthe various processes
which the vast aerial ocean presents, — the absorption of
light, the disengagement of heat, the variation of elastic force,
the hygrometric condition, and the electric tension, — are all so
intimately connected, that each separate meteorological pro-
cess is simultaneously modified by all the rest. This com-
plexity of disturbing causes, (which reminds us involuntarily
of those which the near, and especially the small, cosmical
bodies, the satellites, comets, and shooting stars, encounter in
their course through space), makes it very difficult to give
the full interpretation of meteorological phsenomena; and
the same cause greatly limits or wholly precludes the possi-
bility of that prediction of atmospheric changes, which would
be so important for agriculture and horticulture, for navi-
gation, and for the convenience and pleasures of life. Those
who place the value of meteorology not in the knowledge of
the phsenomena themselves, but in this problematical power
of prediction, are imbued with a firm persuasion that this
branch of science, for the sake of which so many journeys
in distant mountain regions have been undertaken, has for
centuries achieved no progress whereof to boast. The confi-
dence which they refuse to physical philosophers they bestow
on changes of the moon, and on certain days long marked
in the calendar.
Great deviations from the mean distribution of teua-
MUTUAL DEPENDENCE OF METEOROLOGICAL PHENOMENA. 337
perature are seldom local in their occurrence; they
are for the most part distributed in a uniform manner
over extensive districts. The amount of deviation has its
maximum at some one determinate place, in receding from
which it decreases gradually until its limits are reached ; and
when these limits are passed, great deviations in the oppo-
site direction are met with. Similar relations of weather
extend more often from south to north than from west to
east. At the end of 1829 (when I had just completed my
Siberian journey) the maximum of cold was at Berlin, while
North America enjoyed unusual warmth. The assumption
that a severe winter will be followed by a hot summer, or
a mild winter by a cool summer, is a wholly arbitrary one,
resting on no foundation. Opposite conditions of weather
in adjacent countries, or in two corn-producing continents,
are the means of effecting a beneficial equalisation in the
prices of many products of cultivation.
It has been justly remarked that it is the barometer alone
which indicates to us what is taking place in all the strata
of air above the place of observation, (419) while the thermo-
meter and hygrometer are purely local, and can only inform
us concerning the warmth and moisture of the lowest
stratum in close proximity to the ground. The simultaneous
thermic and hygrometric modifications of the upper regions
of the atmosphere (when direct observations on mountains
or in aerostatic ascents are wanting), can be sought only by
hypothetical combinations, whereby the barometer may indeed
serve also to determine temperature and moisture. Impor-
tant change^ of weather do not usually arise from a local
cause situated at the place of observation itself : their origin
is to be looked for in a disturbance of the equilibrium
338 PHYSICAL GEOGRAPHY.
of the currents of the atmosphere which has begun afar
off, and generally not at the surface of the earth but in the
higher regions, and which, bringing with it either warm or
cold, dry or moist, air, either renders the sky and the
atmosphere cloudy and thick, or serene and clear, by trans-
forming the towering masses of cumuli into light feathery
cirrous clouds. As, therefore, the inaccessibility of the
primary phenomena is added to the multiplicity and com-
plication of disturbances, it has always appeared to me that
meteorology must seek its foundations and its advance first
in the torrid zone ; in those more favoured regions where
the same breezes always blow, and where the ebb and flow of
atmospheric pressure, the course of hydro-meteors, and the
phenomena of electric explosions, all recur periodically.
Having now passed through the entire circle of terrestrial
inorganic nature, — having considered our planet in respect to
its form, its internal heat, its electro-magnetic charge, its
polar luminous effusions, the reaction of its interior on its
variously composed crust, and finally the phenomena of its
oceanic and atmospheric envelopes, — the view which we have
essayed to trace in broad and general outlines might be re-
garded as complete, and would be so according to the limi-
tation formerly adopted in physical descriptions of the
globe. Bu! the plan which I have proposed to myself has
a more elevated aim, and I should regard the contemplation
of nature as deprived of its most attractive feature, were
it not also to include the sphere of organic life with
its many gradations of development. The ide| of life is
so intimately connected with the moving, combining,
forming, and decomposing forces which are incessantly in
ORGANIC LIFE. 339
action in the globe itself, that the oldest mythical represen •
tations of many nations ascribe to these forces the produc-
tion of plants and animals, and represent the epoch in which
the surface of our planet was unenlivened by animated forms,
as that of a primeval chaos of conflicting elements. But
investigations into primary causes, or into the mysterious
unresolvable problems of origin, do not enter into the domain
of experience and observation ; nor has the obscure com-
mencement of the history of organisation a place in the de-
scription of the actual condition of our planet. (42°) These
reservations once made, it should still be noticed in the
physical description of the world, that all those substances
which compose the organic forms of plants and animals are
also found in the inorganic crust of the earth ; and that the
same powers which govern inorganic matter are seen to pre-
vail in organic beings likewise, combining and decomposing
the various substances, regulating the forms and properties
of organic tissues, but acting in these cases under conditions
yet unexplained, to which the vague term of " vital phse-
nomena" has been assigned, and which have been systemati-
cally grouped according to analogies more or less happily
imagined. Hence has arisen a tendency of the mind to trace
the action of physical forces to their extremest limits in the
development of vegetable forms, and of those organisms which
are endowed with powers of voluntary motion : and here,
also, the contemplation of inorganic nature becomes con-
nected with the distribution of organic beings over the sur-
face of the globe, i. e. the geography of plants and animals,
Without attempting to enter on the difficult question of
" spontaneous motion," or the difference between vegetable
840 ORGANIC LIFE,
and animal life, it may be remarked that if nature had
endowed us with a microscopic power of vision, and if the
integuments of plants had been perfectly transparent, the
vegetable kingdom would be far from presenting to us that
aspect of immobility and repose which our perceptions now
ascribe to it. The internal parts of the cellular structure are
incessantly animated by the most various currents : ascending
and descending, rotating, ramifying, and continually changing
their direction, they manifest themselves by the move-
ments of a granular mucilaginous fluid in water plants
(naiades, characese, hydrocharidese), and in the hairs of phe-
nogamous land plants, Such is the peculiar molecular
movement discovered by the great botanist Robert Brown
(which is indeed perceptible, not only in vegetables, but also
in all matter reduced to an extreme state of division) ;
such is the gyratory current (cyclose) of globules of
cambium; and, lastly, such are the articulated filamen-
tary cells which unroll themselves in the antherides of
the chara, and in the reproductive organs of liverworts
and algse, and in which Meyen, too early lost to science,
believed that he recognised an analogy to the spermatozoa
of the animal kingdom. If we add to these various currents
and molecular agitations the phenomena of endosmose,
the processes of nutrition and of growth, and internal
currents of air or gases, we shall have some idea of the powers
which, almost unknown to us, are incessantly in action m
the apparently still life of the vegetable kingdom.
Since the time when, in an earlier work (" Ansichten der
Natur," "Tableaux de la Nature"), I attempted to describe
the universal diffusion of organic life on the surface of the
CENEEAI VIEW. 341
globe, and its distribution in height and in depth, our
knowledge has been wonderfully augmented by Ehrenberg's
brilliant discoveries (iiber das Verhalten des kleinsten
Lebens in dem Weltmeere wie in dem Eise der Polar-
lander), which rest not on ingenious combinations and infe-
rences, but on direct and exact observation. By these dis-
coveries the sphere of animated existence — we may say the
horizon of life -—has expanded before our view. " Not only is
there no interruption of minute microscopic forms of animal
life in the vicinity of either Pole where larger animals can-
not maintain themselves, but we find among the micro-
scopic animals of the South Polar Seas, collected in the
Antarctic Expedition of Captain James Ross, a remarkable
abundance of new forms, which are often of great elegance.
Even in the residuum obtained from melted ice which floats
in rounded fragments in lat. 78° 10' S., there have been
found above fifty species of siliceous -shelled polygastrica, and
even coscinodiscse with green ovaries, which were there-
fore certainly living and able to resist the extreme severity
of the cold. In the Gulf of the Erebus and Terror, sixty-
eight siliceous-shelled polygastrica and phytolitharia, together
with a single calcareous-shelled polythalamia, were brought
up by the lead from depths of 1242 to 1620 English feet/'
By far the greater number of the oceanic microscopic
forms hitherto observed belong to the siliceous-shelled in-
fusoria, although the chemical analysis of sea-water has not
shewn silica to be one of its essential constituents, and it
could only indeed exist in water in a state of simple mixture
or suspension. It is not only in particular localities, in
inland waters or in the vicinity of coasts, that the ocean
3 42 ORGANIC LIFE.
is thus thickly peopled with living atoms invisible to
the naked eye. Samples of water taken up by Schayer
in 57° S. lat., on his return from Van Diemen Island, as
well as those taken between the tropics in the middle of
the Atlantic, shew that the ocean water in its ordinary con-
dition, without any appearance of discoloration, contains
innumerable microscopic organisms, quite distinct from
the siliceous filaments of the genus Chsetoceros, floating in a
fragmentary state like the oscillatoria of our fresh waters.
Some polygastrica which have been found mixed with sand
and excrements of penguins in the Cockburn Islands, appear
to be generally distributed over the globe ; other species belong
to both the arctic and antarctic polar regions. (421) Thus we
see that animal life reigns in the perpetual night of the depths
of the ocean, while on continents, vegetable life, stimulated
by the periodical action of the solar rays, chiefly predominates,
The mass of vegetation on the earth very far exceeds that of
the animal creation ; for what, in point of bulk, would be an
assemblage of all the great cetacese and pachydermata living at
one time, compared to the thickly-crowded colossal trunks of
trees of 8 and 12 feet in diameter from the tropical forests
which cover only one region of the earth, namely, that eonv
prised between the Orinoco, the Amazons, and the Rio da
Madeira ? If the characteristic aspect of different portions of
the earth's surface depend conjointly on all external pheno-
mena,— if the contours of the mountains, the physiognomy
of plants and animals, the azure of the sky, the form of the
clouds, and the transparency of the atmosphere,— all combine
in forming that general impression which is the result of the
whole, yet it cannot be denied that the vegetable covering
GENERAL VIEW.
with which the earth is adorned is the principal element in
the impression. Animal forms are inferior in mass, an 1
their individual power of motion often withdraws them from
our sight; vegetable forms,, on the contrary, produce a
greater effect by reason of their amplitude and of their con-
stant presence. The age of trees is announced by their
magnitude, and the union of age with the manifestation ot
constantly renewed vigour, — the ancient trunk with the fresh
verdure of spring, — is a charm peculiar to the vegetable
creation. (422) In the animal kingdom (and this knowledge
is also a result of Ehrenberg's discoveries) it is precisely
the minutest forms which, owing to their prodigious fe-
cundity, (423) occupy the greatest space. The minutest in-
fusoria (the Monadines) only attain a diameter of -s-oWth of
a French line, and yet these siliceous-shelled animalcula
form in humid districts subterranean strata of many fathoms
in thickness.
Those whose minds and feelings are awakened to the in-
fluences of the contemplation of nature, are impressed, under
every zone, by the diffusion of life over the surface of the
globe ; but this impression is most powerful in the regions
where the palms, the bamboos, and the tree-ferns flourish,
and where the ground rises from the margin of a sea filled
with mollusca and corals to the limit of perpetual snow.
The distribution of animal and vegetable life is scarcely
arrested by height or depth : organic forms descend even
into the interior of the earth, not only where the labours of
the miner have opened extensive excavations, but also in
closed natural caverns into which rain or snow-water can
only penetrate tlirough minute fissures. In such a cavern,
344 OBGANIC LIFE.
when opened by blasting, I have observed the snow-white
stalactitic walls covered by the delicate net-work of an Usnea.
Podurellse are found in fissures of the glaciers of Monte
Rosa, and of those of the Grindelwald and the upper
Aar ; the Chionsea araneoides, described by Dalman, and the
microscopic Discerea nivalis (formerly called Protococcns),
live in the polar snows as well as in those of our high
mountains. The red colour of long-fallen snow had been
noticed by Aristotle, who had probably observed it in the
Macedonian mountains. (424) On the highest summits of
the Swiss Alps, lecidese, parmelise, and umbilicarise, scantily
tinge the surface of the rocks where they are denuded of snow ;
but on the chain of the tropical Andes, beautiful phsenogamous
plants, the woolly Culeitium rufescens, Sida pinchinchensis,
and Saxifraga boussingaulti, present, isolated flowers, at
elevations of about 15000 English feet above the level of the
sea. Thermal springs contain small insects (Hydroporas
thermalis), gallionellse, oscillatoria, and confervse : whilst their
waters nourish the fine fibres of the roots of phsenogamous
plants. Not only are earth, air, and water, filled with life,
and that at the most different temperatures, but also the
interior of the various parts of animal bodies : there are
animalcula in the blood of frogs and of salmon : according
to Xordmann, the fluids of the e^es of fishes are often filled
with a worm which lives by suction (Diplostomum) ; and the
same naturalist has even discovered in the gills of the Bleak
an extraordinary double animal (Diplozoon paradoxon)
having two heads and two caudal extremities disposed in
rectangular directions.
Although the existence of meteoric infusoria is more
GEOGRAPHY OF PLANTS AND ANIMALS. 345
than doubtful, it is certainly very possible that small in-
fusoria may be passively carried up with ascending aqueous
vapour, and may float for a time in the atmosphere like the
pollen of the flowers of pines which falls every year from the
air. (427) This circumstance deserves to be especially con-
sidered in any renewal of the old discussion respecting
" spontaneous generation •" (426) and the more so, because,
as I have before noticed, Ehrenbsrg has discovered the re-
mains of eighteen species of siliceous-shelled polygastric
infusoria, in the dust or sand which often falls on ships
navigating the ocean near the Cape Yerd Islands, at a
distance of 380 geographical miles from the African coast.
The geography of plants and animals may be considered
either with reference to the differences and relative numbers
of typical forms, (the distribution of genera and species
in different localities,) or to the number of individuals
of each species on a given surface. Both in plants and in
animals it is essential to distinguish between social or grega-
rious, and solitary species. Those species of plants which I
have termed
nomeua proper to each day of the year are indicated ; such as the iirst blos-
soming of plants, arrival of birds, &c. The 10th of August is marked by the
word meteorodts. It was this indication, combined with the tradition of the
fiery tears ol St. Lawrence, which were the immediate occasion of Dr. Forster's
zealous inquiry into the August phenomenon. (Quetelet, Corresp. Mathe-
Wian^v.c, btrie ui. T. i. 1837, p. 433).
(;;) p. 115.— Hnmboldt, Rel. Hist. T. i. pp. 519—527- Ellicot, in the
Transactions of the American Soc. 1804, Vol. vi. p. 29. Arago says of the
November phenomenon, "Aiusi se confirme de plus en plus 1'existencc
d'une zone compo&ee de millions de petits corps dont les orbites rencontreut
le plan de I'ecliptique, vtrs le point que la terre va occuper tons les ans, du 11
au 13 Novembre. C'cst un noavcau monde planetaire, qni commence a se
reveler a nous." (Anuuaire, 1836, p. 296.)
P) p. 115.— Compare Muschcubroek, Introd. ad Phil. Nat. 1762, T. il
p. 1061. Howard, Climate of London, Vol. ii. p. 23 ; observations of 1806 ;
seven years, therefore, after the earliest observations of Brandes, in Beuzen-
berg iiber Steruschnuppen, S. 240 — 244. August Observations of Thomas
Forster, in Quetelet's Corr. Math. pp. 438—453. Observations by Adolph
Ermau, Boguslawski and Kreil, in Schumacher's Jahrbuch, 1838, pp.
317 — 330. Respecting the point of origin in Perseus on the 10th of August,
1839, see the exact measurements of Bessel and Erman (Schum. Astr. Nachr.
Nr. 385 und 428) ; but on the 10th of August, 1837, the path does not
appear to have been retrograde. See Arago, in- the Comptes-rendus, 1837f
T. ii. p. 183.
(74) p. 115. — On the 25th of April, 1095, "innumerable eyes saw in
France the stars fall from heaven as thick as hail" (ut grando, nisi lucereut,
NOTES. XXIX
ph) densitate putaretur, Baldr. p. 88) ; and this event was spoken of at the
Council of Ciennont as prognosticating the great movement in Christendom
(Wilkeo, Gesch. der Kmwziige, Bd. i. S. 75). On the 22d of April, 1800, a
great fall of sliootiug stars was seen in Virginia and Massachusetts : it was " a
fire of rockets which lasted two hours." Arago was the first to call attention
to this (April) "trainee d'asteroules" as a recurring phenomenon (Annuaire,
1836, p. 297). The fall of aerolites iu the beginning of the month of De-
cember is also deserving of notice. In favour of their periodical recurrence
as a meteoric stream, we have the early observation of Brandes in the night
6 — 7 December, 1798, when he counted 2000 shooting stars (Brandes,
Unterhalt fiir Freunde der Physik, 1825, Heft i. S. 65) ; and perhaps the
immense fall of aerolites oil the llth of December, 1836, in Brazil, by the
river Assu, near the village of Macao (Comptes-rendus, T. v. p. 211).
Capocci, in the interval from 1809 to 1839, has made out twelve actual falls
of aerolites between the 27th and 29th of November, as well as others on the
13th of November, 10th of August, and 17th of July (Comptes-reudus,
T. ii. p. 357). It is remarkable that hitherto no periodical falls of shooting
stars, or streams of aerolites, have been observed in that part of the Earth's
orbit to which the months of January and February, and, perhaps, also the
month of March, correspond, although I myself witnessed a striking display
of shooting stars on the 15th of March, 1803, in the Pacific; and a great
number had been seen in the city of Quito a short time before the great
earthquake of Riobamba (4th of February, 1797). Reviewing what has beea
stated, the epochs most deserving of attention appear to be —
22—25 April.
17 July (17—26 July?) (Quetelet, Corr. 1837, p. 435).
10 August.
12 — 14 November.
27 — 29 November.
6—12 December.
The frequency of these streams ought not to astonish us, if we remember the
my rinds of comets which fill the regions of space, great as is the diflerenct
between insulated comets and rings composed of asteroids.
p) p. 116.— Ferd. v. "Wiangel, Reise laugs der Nordkiiste von Sibirien in
den Jahren 1820—1824, Th. ii. S. 259. Respecting the return of the
denser swarm of the November stream after a period of 34 years, see Gibers,
in the Jahrbuch, 1837, S. 280. I was told at Cuinana that, a short time
before the terrible earthquake of 1766, — 33 years, therefore, before the great
XXX NOTES.
•hower of shooting stars of 11 — 12 November, 1799, — a similar display liad
been seen. The earthquake, however, was not in November, but on the 21st
of October, 1766. It may still, perhaps, be possible for some traveller to
ascertain in Quito the precise day on which, during a whole hour, the volcano
of Cayamba appeared as if veiled by the number of falling stars, and the
alarmed inhabitants instituted processions. (Relat. Hist. T. i. Chap. iv.
p. 307; Chap. x. pp. 520 and 527.)
f6) p. 117. — From a letter to myself, dated January 24, 1838. The
prodigious fall of shooting stars of November 1799, was seen almost exclu-
sively in America, where it was witnessed from Neu-Hcrrnhut in Greenland,
to the Equator. In 1831 and 1832, the phenomenon was seen in Europe,
and scarcely elsewhere; and, in 1833 and 1834, was seen only in the United
States of North America,
(77) p. 118. — Lettre de M. Edouard Biot a M. Quetelet sur les anciennes
apparitions d'etoiles filantes en Chine ; Bulletin de 1' Academic de Bruxelles,
1843, T. x No. 7, p. 8. On the notice from the Chronicon Ecclesise Pragensis,
see Boguslawski (the son), in. Poggend. Annalen, Bd. xlviii. S. 612. Add to
Note 42, that the paths of the four comets of 568, 574, 1337, and 1385,
have also been calculated exclusively from Chinese observations. See John
.Russell Hind, in Schumacher's Astronomische Nachricten, 1844, Nr. 498.
(rs) p. 118. — "II paroit qu' tin nombre, qui semble mtpuisable, de corps
trop petits pour etre observes, se meuveut dans le ciel, soit autour du soleil,
soit autour dcs planetes, soit peut-etre meme autour dc-s satellites. On suppose
qne quand ces corps sont rencontres par notre atmosphere, la difference entre
lent Vitesse et celle de notre planete est assez grand pour que le frottement
qu'ils t'prouvent centre Pair, les echaufle au point de les rendre mcandcscents,
et quelquefois de les laire eclater. — Si le groupe des etoiles filautes forme un
anneau continu autour du soleil, sa vitesse de circulation pourra etre tres
diflercnte de celle de la terre, et ses deplacemeus dans le ciel, par suite des
actions plauetaires, pourront eucore rendre possible on impossible, a diflerentes
tpoqucs, le phtiiomtne de la rencontre dans la plan del'ecliptique." (Poisson,
Etchtrtb.es sur la Probabilite des Jugemeuts, pp. 306 — 307.)
C79) p. 119.— Humboldt, Essai polilique sur la Nouvelle Espagne (2m« edit.)
T. iii. p. 310.
C*) p. 119. — Pliny has remarked the peculiar colour of the crust of aerolites,
" colore adusto" (ii. 56 and 58). The expression "lateribus pluisse," also
refers to the burnt appearance of their exterior.
(«) j. 120.— Humboldt, Rel. Hist. T. ii. Chop. xx. pp. 299—302.
NOTES. XXXI
f2) p. 121. — Gustav Rose, Reise nach dem Ural, Bd. ii. S. 202.
C33) p. 121.— Gustav Rose, in Poggend. Ann. 1825, Bd. iv. S. 173—192.
Rammelsberg, Erstes Suppl. zura chem. Handworterbuche der Mineralogie,
1843, S. 102. Olbers acutely observes, that "it is a remarkable circum-
stance, not hitherto noticed, that no fossil meteoric stones have as yet been
found, like fossil shells, in secondary and tertiary formations. Are we to infer
that, previous to the last and present arrangement of the surface of our planet,
no meteoric stones had fallen upon it, although, according to Schreibers, it is
probable that 700 falls of aerolites now take pTace in each year ?" (Olbers, in
Schum. Jahrb. 1838, S. 329.) Problematical uickeliferous masses of native
iron have been found in Northern Asia (Gold-washing work of Petropa\vlo\vsk,
80 geographical miles south-east of Kusaezk), at a depth of 31 French feet,
and recently among the Carpathian mountains (Magura, near Szianic?).
Both these masses are very like meteoric stones. Compare Erman, Archiv
fiir wissenschaftliche Kunde von Russland, Bd. i. S. 315, and Haidinger'a
Bericht iiber die Slaniczer Schiirfe in Ungarn.
(84) p. 121.— Berzelius, Jahresber. Bd. xv. S. 217 and 231 , Rammelsberg,
Handworterbuch, Abth. ii. S. 25—28.
(K) p. 122.— Sir Isaac said, "he took all the planets to be composed of the
same matter with this earth, wz. earth, water, aud stones, but variously cou-
cocted." Turner, Coll. for the Hist, of Grantham, cont. authentic Memoirs
of Sir Isaac Newton, p. 172.
(®) p. 123.— Adolph Ermau, in Posrgendorff's Annalen, 1839, Bd. x!vii«'.
S. 582 — 601. Biot had previously thrown some doubt on the probability of
the reappearance of the November stream at the beginning of May (Comples-
rendus, 1836, T. ii. p. 670). Mndler has examined the mean depressiOD of
temperature on the three ill-reputed days in the mouth of May, viz. llth,
12th, and 13th, by 86 years of observations at Berlin (Verhandl. des Vereius
zur Beford. des Gartenbaues, 1834-, S. 377); and has found a retrogressioa
of temperature of 1°.22 Cent. (2°. 2 Fahr.) just at the season which is very
nearly that of the most rapid advance of temperature. Jl is much to be wished
that this phenomenon, which some have been inclined to attribute to the
cooling effect of the melting of large masses of ice in the north -eastern part of
Europe, should be examined at distant parts of the globe, as in North America,
and in the southern hemisphere. Compare Bulletin, de 1'Acad. Imp. de St..
Petersbourg, 1843, T. i. No. 4.
(87) p. 123. — Plut. Vitse par. in Lysandro, cap. 22. The account given
by Damachos (Daimachos) of a fiery cloud, throwing out sparks like shooting
XXX11 NOTES,
stars having been seen in the sky without interruption for the space of seventy
days, at the end of which it descended nearer to the earth, and let fall the
stone of JEgos Potamos, " which was only an inconsiderable portion of the
cloud," is very improbable, because it would require the direction and velocity
of the ball of fire to be for so many days the same as the Earth's ; in the case
of the fire-ball of July 19, 1686, described by Halley (Phil. Trans. Vol. xxix.
p. 163), this only lasted for a few minutes. It is somewhat uncertain whether
the Daiinachos, the writer irtgi eumi-minor axis, 3261139'33 T. ; the ellipticity,
_^.T7,? ; and the length of a mean degree of the meridian, 57013*109 T. with
a probable error of 2'8403 T. ; whence the length of a German geographical
mile, 15 to a degree, is 3807'23 T. [In British measures, the semi-major
axis is 20924774 feet; the semi-minor axis, 20854821 feet; the length of a
mean degree of the meridian, 364596'0 feet, with a probable error of 18'16
feet ; and that of a geographical mile, 60 to a degree, G086'76 feet. ED.] Pre-
vious combinations of measurements of degrees varied between -§±-3 and ^T :
thus Walbeck (De Forma et Magnitudine Telluris in Demensis Arcubus Meri-
diani definiendis), in 1819, gives -g^rg; Ed. Schmidt, (Lehrbuch der math,
tmd phys. Geographic, S. 5), in 1829, gives ^r •** from seven measures.
Respecting the difference of the compression deduced from measurements in
different longitudes, see Bibliotheque universelle, T. xxxiii. p. 181, and
T. xxxv. p. 56 ; also Connaissance des Terns, 1829, p. 290. From the luiiar
inequalities, Laplace found, by the older tables of Burg, s^V? (Expos, du
Syst. du Monde, p. 229), and subsequently, by employing the observations
of the moon discussed by Burckhardt and Bouvard, ^VT (Mecan. celeste,
T. v. pp. 13 and 43.)
(131) p. 157. — The values of the compression deduced by means of the
pendulum are as follows : — The general result of Sabine's great expedition.
(1822 and 1823, from the equator to 80° N. lat.), ^%.T ; Freycinet, exclud-
ing the experiments at the Isle of France, Guam, and Mowi, 5-5^.5 ; Foster,
EF5-7?; Duperrey, £^g.7; Liitke (Partie nautique, 1836, p. 232), from 11
stations, ^^ . Lesser ellipticities have been given by the pendulum observa-
tions between Formentera and Dunkirk, g^s-i? according to Mathieu (Con-
naissance des Terns, 1816, p. 330) ; and by those between Formentera and
Unst, 3-71* according to Biot. Baily, Report on Pendulum Experiments, in
the Memoirs of the Royal Astr. Society, Vol. vii. p. 96 ; also Borenius, in
the Bulletin de 1'Acad. de St.-Petersbourg, 1843, T. i. p. 25. The first
proposal to adopt the length of the pendulum as a standard of measure, and
to establish the third part of the seconds pendulum (supposed to be every
where of equal length) as a pes honor arius, — the measure of a unity which
might be recovered at any future age of the earth, and by nations dwelling on
any part of its surface, is found in Huygens' Horologium oscillatorium, 1673,
Prop. 25. In 1742, the same wish was publicly enounced in an inscription
on a monument erected at the equator by Bouguer, La Coudamine, and Godin.
On a handsome marble tablet, which I have seen uninjured in the old Jesuits'
College at Quito, it is said : — " Penduli simplicis eequinoctialia uniua minuti
VOL. I 2 E
xv NOTES.
secundi arclietypus, mensurse naturalis exemplar, utiiiara universalis !" Prom
what La Condamiue has said, in his Journal du Voyage a 1'Equateur, 1751,
p. 163, respecting parts of the inscription which are not filled up, and a dif-
ference between Bouguer and himself about the numbers, I had conjectured
that I should find considerable discrepancy between the tablet and the inscrip-
tion as published in Paris ; but, after a careful comparison, I discovered only
two discrepancies of little importance, — "ex area graduum 3£," instead of
" ex arcu graduum plus ptam trium;" and the date of "1745," instead of
•' 1742." The date of 1745 is singular, because La Condamine returned to
Europe in 1744, Bouguer in June of the same year, and Godin left South
America in July 1744. The most necessary and useful amendment of the
numbers of the inscription would have been the astronomical longitude of
Quito. (Humboldt, Recueil d'Observ. astron. T. ii. pp. 319 — 354.) Nouet's
latitudes, engraved on Egyptian monuments, offer a more recent example of
the danger of perpetuating, thus solemnly, erroneous or imperfectly computed
results.
(132) p. 158. — On the increased intensity of gravitation in volcanic islands
(St. Helena, Ualan, Fernando de Noronha, Isle of France, Guam, Mowi, and
the Galapagos), Rawak (Liitke, p. 240) being an exception, perhaps, on
account of its proximity to the high land of New Guinea, see Mathieu, in
Delambre, Hist, de FAstronomie au 18me siecle, p. 701.
[The fact of the increased intensity of gravitation in volcanic islands was,
I believe, first made known by myself (Pendulum Experiments, 1825, pp.
237 — 341), as the results of my own experiments at the islands of Ascension
and of St. Thomas (in the gulph of Guinea), and at other stations of
different geological character. The comparison of the whole series furnished
a numerical scale of local influence in which the volcanic islands of Ascension
and St. Thomas occupied the higher extremity, and stations of alluvial soil
and sand the lower extremity, whilst the intermediate gradations of local
influence were seen to correspond in a remarkable manner with the density of
the superficial strata. " The scale afforded by the pendulum for measuring
the intensities of local attraction appears to be sufficiently extensive to render
it an instrument of possible utility in inquiries of a purely geological nature.
It has been seen that the rate of a pendulum may be ascertained with proper
care to a single tenth of a second per diem ; whilst the variation of rate occa-
sioned by the geological character of stations has amounted in extreme case*
to nearly ten seconds per diem : a scale of 100 determinate parts is thus
afforded in which the local attraction dependent on the geological accidents
NOTES. xv
may be estimated." (Tend. Exp. p. 341 .) Tlie work from which this passage
is taken was published before M. Mathieu's notice in Delambre's History of
Astronomy, and is referred to by M. Mathieu in the passage to which M. de
Humboldt alludes. — EDITOB.]
(133) p. 158. — Numerous observations shew great irregularities in the
length of the pendulum in continental as well as in insular and littoral locali-
ties, and which are also ascribed to local attraction. (Delambre, Mesure de
la Meridienne, T. iii. p. 548; Biot, Mem. de 1' Academic des Sciences,
1829, T. viii. pp. 18 and 23. In crossing the south of France and Lombard/
from west to east, we find a minimum of intensity of gravitation at Bordeaux
thence it increases rapidly at the more eastern stations of Figeac, Clermont-
Ferrand, Milan, and Padua, at which last city it reaches a maximum. In
the opinion of Elie de Beaumont (Recherches sur Ics Revolutions de la
Surface du Globe, 1830, p. 729), the influence of the Alps on the variations
of gravitation on their southern side is not alone to be ascribed to their
mass, but still more to the rocks of melaphyre and serpentine which have
elevated the chain. On the slope of Mount Ararat (which, with Caucasus,
may be said to be situated near the centre of gravity of the old con-
tinent, consisting of Europe, Asia, and Africa), Fedorow's very exact pen-
dulum experiments indicate likewise the presence of dense volcanic masses in
lieu of cavities (Parrot, Reise zum Ararat, Bd. ii. S. 143). In the geoJcsical
operations of Carlini and Plana in Lombardy, differences of 20" to 47".8
have been found between geodesical measurements and the direct determi-
nations of latitude ; see the instances of Andrate and Mondovi, Milan and
Padua, in Operations geodes. et astron. pour la mesure d'un arc du parallele
moyeu, T. ii. p. 347; Effemeridi astron. di Milano, 1842, p. 57. It
follows from the French triangulation that the latitude of Milan, deduced
from that of Berne, is 45° 27' 52"; whereas direct astronomical observation
gives it 45° 27' 35". As the perturbations extend in the plain of Lombardy
to Parma, far south of the Po (Plana, Operat. geod. T. ii. p. 847), we may
conjecture that there are deflecting causes in the plain itself. Struve has
met with the same anomalies in the most level parts of eastern Europe
(Schumacher, Astr. Nachr. 1830, Nr. 164, S. 399). On the influence of
dense masses supposed to exist at a small depth equal to the mean height of
the chain of the Alps, see the analytical expressions which Hossard and Rozet
have inserted in the Comptes-rendus, T. xviii. 1844, p. 292, and compare
them with Poisson, Traite de Mecanique (2mt e"d.), T. i. p. 482. The
earliest notices of the influence which rocks of different kinds might exercise
xlvi
NOTES.
ou the vibrations of the pendulum were given by Thomas Young, in the Phil.
Trans, for 1819, pp. 70 — 96. But in drawing conclusions from the length
of the pendulum relatively to the curvature of the earth, it ought not to be
overlooked that the crust of the earth may possibly have been hardened pre-
vious to metallic and dense basaltic masses having penetrated from great
depths through open channels and clefts, and approached the surface.
(134) p. 158.— Laplace, Expos, du Systeme du Monde, p. 231.
(135) p. 159. — La Caille's pendulum experiments at the Cape of Good Hope,
which Mathieu has calculated with great care (Delambre, Hist, de 1'Astr. an
18me siecle, p. 479), give an ellipticity of 5^.7; fr°m several comparisons of
observations in equal latitudes in the two hemispheres (New Holland and the
Falkland Islands compared with Barcelona, New York, and Dunkirk), there is
as yet no ground for supposing the mean ellipticity of the southern hemisphere
to be greater than that of the northern (Biot, in the Mem. de 1'Acad. des
Sciences, T. viii. 1829, pp. 39—41).
(136) p. 159. — The three methods of observation give the following results : —
1st, from the deflection of the plumb-line by the proximity of the Schehallien
Mountain (Gaelic, Thichallin), in Perthshire, 4'713, resulting from the expe-
riments of Maskelyne, Hutton, and Playfair, 1774 — 1776 and 1810) according
to a method which had been proposed by Newton ; 2d, by pendulum vibra-
tions on a mountain, 4'837 (Carlini's observations on Mount Cenis compared
with Biot's observations at Bordeaux, Effemer. astr. di Milano, 1824, p. 184) ;
3d, by the balance of torsion in Cavendish's experiments with an apparatus
originally devised by Mitchell, 5'48 ; or, according to Huttou's revision of
the calculation, 5'32, or Eduard Schmidt's revision, 5'52 (Lchrbuch der
math. Geographic, Bd. i. S. 487) ; by the balance of torsion in Reich's expe-
riments, 5'44. In the calculation of these experiments of Professor Reich,
which are a model of exactness, the original mean result (having a probable
error of only 0'0233) was 5'43 ; which, being increased by the quantity by
which the centrifugal force of the earth diminishes, the force of gravity for
the latitude-of Freiberg (50° 55') becomes 5'44. The employment of masses
of cast iron instead of lead has not shewn any sensible difference, or none which
Ls not well within the limits of observation error, disclosing therefore no traces
of magnetic influence (Reich, Versuche iiber die mittlere Dichtigkeit der Erde,
1838, S. 60, 62, und 66). By the assumption of too small an ellipticity
of the earth in the calculations, and by the difficulty of forming a correct
estimate of the density of rocks on the surface, the mecn density of the earth,
previously deduced from the experiments on or near mountains, appeared^ too
NOTES.
xlvii
smnll, vis. 4'?61 (Laplace, Me'canique celeste, T. v. p. 46,) or 4'785 (Eduard
Schmidt, Le.hrb. der math. Geog. Bd. i. § 387 nnd418). On Halley's hypo-
thesis of the earth being a hollow sphere, alluded to in the following page,
(and which was the germ of Franklin's notions respecting earthquakes), ?ce
Phil. Trans, for the year 1693, Vol. xvii. p. 563. " On the structure of ths
internal parts of the earth, and the concave habited arch of the shell."
[Carlini's result, by the second method noticed by M. de Humboldt, requires
a correction which has not yet been applied to it, and which would probably
alter it considerably; namely, for the true reduction to a vacuum of the
vibrations of the pendulum observed at Bordeaux and on Mont Cenis. The
height above the sea of the station at Mont Cenis was 6374 English feet ; nnd
the difference in the density of the air, in which the pendulum was vibrated at
the two stations, must have been quite sufficient to occasion a verv sensible
error in the difference in the lengths of the respective pendulums computed
by the mode of reduction practised before Bcssel's discovery, alluded to
in page 26 of the text of Cosmos, was made. The pendulum employed by
Carliui was that of Biot (with few but valuable modifications) ; and the
true reduction to a vacuum for pendulums of that description has not yet been
experimentally investigated. As an instrument for ascertaining the density
of the earth, the pendulum is so much inferior to the torsion- balance employed
by Cavendish and lleich, and still more recently by Baily (whose results do
not appear to have been known to M. de Humboldt when this volume of
Cosmos was published), that if the true reduction to a vacuum of Biot's
pendulum were required only for the correction of the mean density of the earth
derived from the experiments on Mont Cenis, it might not be worth while to
undertake its determination : but it should not be forgotten that, until such a
determination has been made, the true results of the laborious experiments by
which M. Biot himself sought to ascertain the length of the seconds pendulum
at Paris, and at various other stations in France and elsewhere, are unknown :
there can be little doubt that the absolute lengths computed at the time will
have to receive very large corrections ; and though the relative lengths will
certainly be less seriously affected, they may be altered to a degree which
may influence, in part at least, the conclusions which M. de Humboldt has
drawn in Note 133, respecting the variations of gravity in the South of
France. — E D ITOR.]
(1:5~) p. 162. — To these belong the excellent analytical investigations of
Fourier, Biot, Laplace, Poisson, Duhamel, and Lame. Poisson, in his work
entitled " Theorie mathe'matique de la Chaleur," 1835, p. 3, 428 — 430, 436,
xlviii NOTES.
and 521 — 524 (see also the extract which de la Rive has made in the " Bib-
liotheque universelle de Geneve," T. k. p. 415), has developed an hypothesis
wholly different from Fourier's views ; " Theorie analytique de la Chaleur."
Poisson denies the actual fluidity of the interior of the Earth ; he thinks " that
in the process of cooling by radiation to the medium surrounding the earth, the
particles which were first solidified at the surface sunk, and that by a double
current, descending and ascending, the great inequality was diminished which
would otherwise take place in a solid body cooling from its surface." It
seemed to this great geometer more probable that the solidification should
have begun in the strata nearer the center ; " that the phenomenon of the
temperature increasing with increasing depth does not extend to the whole
mass of the Earth, and is merely a consequence of the movement of our
planetary system in space, of which some parts are of very different tempera-
ture from others, by reason of stellar heat (chaleur stehaire)." Thus, accord-
ing to Poisson's views, the warmth of the waters in our Artesian wells would
be merely a warmth which had penetrated into the Earth from without ; and
" the earth itself might be compared to a mass of rock conveyed from the
equator to the pole so rapidly as not to have entirely cooled. The increase of
temperature in such a block from the surface inwards would not extend to its
center." The physical doubts which have been justly raised against this sin-
gular cosmical view (attributing to the regions of space that which is better
explained by the transition from a primitive gaseous to a solid state) will be
found collected in Poggendorff's Annalen, Bd. xxxix. S. 93 — 100.
(13S) p. 163. — The increase of temperature has been found in the Puits de
Crenelle at Paris to be 1° C. for 98.4 (104.9 Eng.) feet ; in the mine at Neu-
Salzwerk, near Minden in Prussia, for nearly 91 (97.0 Eng.) feet ; and, ac-
cording to Auguste de la Rive and Marcet, the same (viz. 1° C. for 91 French feet
at Pregny near Geneva, although the mouth is situated 1510 (1609 Eng.) feet
above the level of the sea. The agreement between the results derived by
a method first proposed by Arago, in 1821 (Annuaire, 1835, p. 234), from
mines that are severally 1683 (1794 Eng.) feet, 2094 (2232 Eng.) feet, and
680 (725 Eng.) feet, in absolute depth, is remarkable. It is probable that
if there are two points on the Earth's surface situated at a small vertical
distance above each other, whose annual mean temperatures are exactly deter-
mined, they are to be found at the Paris Observatory, where the mean tem-
perature of the external air is 10°.822 C. (51°.48 F.), and of the Caves de
T0bservatoirell°.834 C. (53°.3 F.) ; the difference being lc.012 (1°.8 F.) for
28 metres (91.9 English feet). Poisson, Theorie matn.d la Clialeur, p. 15
NOTES.
and 462. In the course of the last 1? years, from some cause which lias not
been completely ascertained, the indications of the lower thermometer have
increased 0°.220 ; but this probably is not due to any actual increase in the
general temperature of the caves. Results obtained by means of Artesian wells
are, indeed, liable to error, from infiltration, or from penetration from lateral
crevices; but currents of cold air, and other circumstances, are still more
injurious to the accuricy of the many laborious series of observations that have
been made in mines. The general result of Uoi«-h's extensive examination
into the temperature of the mines in Snxony, gives a somewhat slower in-
crease of the terrestrial heat, or 1° C. to 41.84 metres (1° F. to 76.26 English
feet) — Reich, Beob. iiber die Tcmperatur des Gesteins in verschiedenen
Tiefen, 1831, S. 13 4). Phillips, however, found, in the coal mine of Monk-
wearrnouth near Newcastle, in which, as I have already remarked, wordings
are carried on at a depth of nearly 1500 English feet below the level of the
sea, 32.4 metres, or 106.3 English feet to 1° C. (1° F. to 59.06 English feet),
a result almost identical with that found by Arago from the Puits de Crenelle
(Poggend. Ann. Bd xxxiv. S. 191).
(139) p. 165. — Bo'issiiigauH, Sur la Profondeur a laquelle se trouve la
couche de Tempcnluro ii-variable entre les Tropiques, in the Auuales de
Chimie et de Physique, T. iii. 1833, p. 225—24?.
[The observations of Mr. Caldecott at Trevandrum in 1842 and 1843
(Quetelet, Climot de laBelgique, p. 137, et seq.) have shown that the stratum
of invariable temperature is not always found within the tropics at so small a
depth. At Trevandrum, at the depth of six French feet, the mean temperature
of different months, instead of being constant, varies as much as 3° 6' Fah. ;
and the curve of annual ttmperature at that depth exhibits in very marked
characters two maxima corresponding to the double passage of the sun over
the zenith of Ticvandmm. — EDITOR.]
(14°) p. 166— Laplace, Exp. du Syst. du Monde, p. 229 and 263; Meca-
Dique celeste, T. v. p. 18 and 72. It should be remarked, that the fraction
Troth of a centesimal degree of the mercurial thermometer, given in the text
as the limit of the permanency of the temperature of the globe since the days of
Hipparchus, rests on the supposition that the dilatation from heat of the sub-
stances of which the E;irth is composed is equal to that of glass, or Tcrrnroo^
for 1° C. Respecting this hypothesis, see Arago, Annuaire pour 1834,
p. 177—190.
(141) p. 167.— William Gilbert, of Colchester, whom Galileo entitled "great
to a degree which might be envied," said, " Magnus magnes ipse est globui
1 NOTES.
terrestris." He ridiculed the loadstone mountains which TYacastoro, the great
contemporary of Columbus, supposed to constitute the magnetic polea — " roji-
cicuda cst vulgaris opiuio de montibus magneticis aut rupe aliqua magnctica,
ant polo phaatastico a polo mundi distante." Ho assumed the declination of
the magnetic needle to be invariable at each point of the surface of the Earth
(" vavialio uniuscujusquc loci constans est") ; and explained the inflexions oi
the iso<_'onic linos by the form of the continents and the relative positions of
the sea-basins, which exercise a less degree of magnetic force than the solid
portions which rise above the le^el of the ocean (Gilbert de Magnete, ed. 1633,
p. 42, 98, 152, and 155).
(u-) p. 16?.— Gauss, Allgemdne Theorie des Erdmagnetismus, in den
Resultaten aus den Beob. des magnet. Vercins, 1838, § 41, S. 56. Trans-
lated in " Taylor's Scientific Memoirs," Vol. ii. P. vi. Art. v.
O p. 168. — There are also perturbations which do not extend to such
great distances, and of which the causes are more local, and are seated, per-
haps, at less depths. I made known, some years ago, a rare instance of this
kind, in which the disturbance manifested itself in the Freiberg mines, but not
at Berlin. (Lettre de M. de Humboldt a S. A. R. le Due de Sussex sur le»
moyens propres a perfectiouner la connaissance du magnet isme terrestre,
published in Becquercl's Trait e experimental de 1'electricite, T. vii. p. 442).
Magnetic storms, which were felt simultaneously from Sicily to Upsala, did
not extend from Upsala to Allen (Gauss and Weber, Resultate des Magnet.
Vereins, 1839, S. 128 ; Lloyd, in the Comptes-rendus de 1' Academic dea
Sciences, T. xiii. 1843, Sem. ii. pp. 725 and 827). Amongst the numerous
and recent examples of disturbances extending simultaneously over wide por-
tions of the earth's surface, which are assembled in Sabine's important work
(Observ. on Days of Unusual Magnetic Disturbance, 1843), one of the most
memorable is that of September 25, 1841, which was observed at Toronto in
Canada, at the Cape of Good Hope, at Prague, and partially at Van Dienien
Island. The English observatories suspend their operations on Sundays, and,
owing to the difference of longitude, the midnight of Saturday took place at
Van Dienien Island soon after the commencement of the disturbance, of which,
probably, the greater portion thus escaped observation.
[The disturbance of Sept. 24th and 25th appears also to have extended to
Macao (Phil. Trans. 1843, p. 133) ; and it is worthy of remark that, from Sir
Edward Belcher's observations, it may be inferred that the intensity of the
horizontal force was increased at Macao at the same hours when it waa
diminished elsewhere. — EDITOJI.]
UOTES, II
»
C144) p. 108. — I have described, in the Journal de Physique of Lametherie
(1804, T. lix. p. 449), the application of the magnetic Inclination to deter-
minations of latitude along a coast running north and south, and, like that of
Chili and Peru, constantly enveloped by mist (garna) during part of the
year. In the particular locality alluded to, this application is the more
practically important, by reason of the strong southerly current, ex-
tending to Cape Farina, which causes great loss of time to navigators, who
have inadvertently passed to the north of the latitude of the port to whicli
they are bound. In the Pacific, from Callao to Truxillo, I have found,
for a difference of latitude of 3° 5?', a change of Inclination of ^8°.l ; an4
from Callao to Guayaquil, for a change of latitude of 9° 50', a change o»
Inclination of 20°.7 (Relation historique, T. iii. p. 622). At Guarmey (la*
10° 4' S.), Huaura Gat. 11° 3' S.), and Chancay (lat. 11° 32').. the Inclination*
were respectively : — 6°.l, 8°.l, and 9°.3. The determination of the ship's
place by means of the magnetic Inclination, when her course nearly
intersects the isoclinal lines at right angles, is distinguished from all other
methods by its independence of the time of the day, and by its not, therefore,
requiring the sight of any of the heavenly bodies. I have very recently
learned that, as early as the end of the sixteenth century, scarcely twenty years
after Robert Norman invented an Inclinatorium, William Gilbert, in his
great work " De Magnete," proposed the determination of latitudes by means
of the Inclination of the magnetic needle. In his Physiologia nova de Magnete,
Lib. v. cap. 8, p. 200, he extols the advantages of this method in thick weather,
" acre caliginoso." Edward Wright, in the preface which he has added to the
work of his illustrious master, says that this proposal is " worth much gold."
As he shared Gilbert's error in believing the isoclinal lines ( j be parallel to
the geographical equator, he did not perceive that the method is only appli-
cable in particular localities.
(145) p. 1GS. — Gauss and Weber, Resultate des inagnctischen Vereins,
im J. 1838, § 31, S. 46.
(146) p. 168.— According to Faraday (London and Edinburgh Philosophical
Magazine, 1836, Vol. viii. p. 1?8), pure cobalt is not magnetic. I am aware
that other distinguished chemists (Hcinrich Rose and Wohler) do not consider
this a settled point ; but it appeal's to me that if one of two carefully-purified
masses of cobalt, both supposed to be free from any alloy of nickel, is found to be
non-magnetic, it is probable that the magnetism shewn in the other mass is due
to a want of purity ; and I am inclined, therefore, to believe Faraday's view
to be the more correct.
Iii BOXES.
(14J) p. 169. — Arago, in t!ie Annales de Ohhnie, T. xxxii. p. 214 ; Brewst«rf
1 realise on Magnetism, 1837, p. Ill i Baumgarlner, in the Zeitschrift fiii
i'Dys. und Mathem. EL ii. S. 419.
(148) p. 169. — Humboldt, Examen critique de PHist. de la Geographic,
T. iii. p. 36
(14C) p. 169. — Asie cent. T. i. Introduction, p. xxxvii. — xlii. The western
nations, the Greeks and the Romans, knew that magnetism could be imparted
permanently to iron — (" sola hsec muteria ferri, vires a magnete lapide accipit
'.etinelque lonyo lempore" Plin. xxxiv. 14.) The gr,at discovery of the
earth's directive force wou'd, therefore, also Lave been made in the west, if
any one had accidenta^y observed a fragment of loadstone more long than
broad, or a magnetised bar of iron suspended bv a thread, or floating freely on
the surface of water on a wooden support.
(15°) p. 170. — Topographical surveys, made solely by compass, and without
any provision for corrections for changes of terrestrial magnetism, cannot fail
ultimately to produce great confusion in the boundary lines between different
properties, excepting in those parts of the earth where the magnetic declina-
tion is either invariable, or at least is subject only to exceedingly small secular
changes. Sir John Herschel says, "The while mass of "West India property
has been saved from the bottomless pit of endless litigation by the invariability
of the magnetic declination in Jamaica and the surrounding archipelago, during
the whole of the last century, all surveys of property there having been con-
ducted solely by the compass. Compare Robertson, in the Phil. Trans, for
1806, Part ii. p. 348, on the pe.maneney of the compass in Jamaica since
1660. In the mother country (England), the magnetic declination has altered
during the same period fully 1*°.
(151) p. 171. — I have shewn elsewhere that the documents of Columbus's
voyages which have come down to us, give, with much certainty, three
determinations of points in the Atlantic line of no declination for September 13,
1492, May 21, 1496, and August 16, 1498. The direction of this curve was
at that time from N.E. to S.W.; and it touched the continent of South
America, a little to the east of Cape Codera, instead of, as at present, in the
northern part of Brazil, (Examen critique de 1'histoire de la Geographic, T. iii.
pp. 44—48). We learn from Gilbert's Physiologia nova de Maguete, Lib. iv.
cap. i. the remarkable fact that, iii tb. year 1600, as in the time of Columbus,
the magnetic needle had scarcely any declination in the \ icinity of the Azores. I
think that I have shewn satisfactorily, from documentary evidence (in my Exa-
inc'ii critique, T. iii. p. 54), that the famous line of demarcation by which Pope
NOTES. liii
Alexander VI. divided the western hemisphere between Spain and Portugal,
was not drawn through the westernmost of the group of the Azores, because
Columbus was desirous of converting a physical into a political division. He
attached great importance to the zone (raya), " in which the compass ceases
to shew any variation, where the air and the sea assume a new character, where
the sea is covered with weeds, and cool breezes begin to blow, and where the
form of the Earth is no longer the same." The last supposition was ail in-
ference from erroneous observations of the Pole star.
C52) p. 171. — It is a question of the highest interest towards the solution
of the problem of the physical causes of terrestrial magnetism, whether the
two remarkable systems of closed isogonic curves will continue to move forward
for centuries to come, still preserving this closed form, or whether they will
open out and lose their peculiar character. In the Asiatic system, the decima-
tion increases from without inwards ; in the Pacific system, the contrary is the
case ; no line of no declination, — indeed, no line below 2° east, — is now known in
the Pacific to the east of Kamschatka, (Erman, in Poggend. Annalen, Bd. xxi.
S. 129): but it appears that, in 1616, on Easter-day, Cornelius Schouten
found no declination a little to the S.E. of Nukahiva, in 15° S. lat. and 132°
W. long, (from Paris), and, therefore, in the middle of the present closed
system (Hansteen, Magnetismus der Erde, 1819, S. 28). In all these con-
siderations it must not be forgotten, that we can only trace the lines of magnetic
direction and force in their progressive displacements by observations which
are confined to their intersection with the surface of the Earth.
(153) p. 172.— Arago, Annuaire, 1836, p. 284; and 1840, pp. 330—338.
(154) p. 172.— Gauss, Allgemeine Theorie der Erdmagnetismus, § 31.
(155) p. 172. — Duperrey, de la configuration de 1'e'quateur magnetique, in
the Annales de Chimie, T. xlv. pp. 371 and 379 ; also Morlet, in the Memoires
presentes par divers savans a 1'Acad. Roy. des Sciences, T. iii. p. 132.
(156) p. 173.— See, in Sabine's Contributions to Terrestrial Magnetism,
1840, p. 139, the remarkable map of the isoclinal lines in the Atlantic Ocean
for 1825 and 1837.
(157) p. 174. — Humboldt, iiber die seculare Veranderung der magnetischen,
Inclination, in Poggeud. Annalen, Bd. xv. S. 322.
(!«) p. 174. — Gauss, Resultate der Beob. des magn. Vereins im Jahr 1838,
§ 21 ; Sabine, Report on the Variations of the Magnetic Intensity, p. 63.
[The progress of investigation, since the first volume of " Cosmos" was
written, has continued to confirm the opinion expressed by M. de Humboldt in
tlic text (p. 174), that in respect to the theory of terrestrial magnetism, the
v NOTES.
isodynamic lines are those from which the most fruitful results are to be er-
pected. Researches into the amount of the magnetic force at different points
of the earth's surface, and graphical representations of the results by line*
drawn through the points where the force has an equal intensity, have shown,
that there are two foci or points of maximum force in each hemisphere, and
consequently four on the whole surface of the globe. The isodyuamic lines
which surround each of the two points of maximum in an hemisphere, are not
circles, but are of an ovate form, having the larger axis in a direction which,
if prolonged, would connect the two foci by the shortest line, or nearly so, which
can be drawn between them on the surface of the globe. As the ovala
successively recede from the focus they correspond to weaker and weaker
degrees of force, each in its turn enclosing the ovals of higher intensity.
This continues to be the case until the two systems ot ovals encounter in a
point intermediate between the foci : the isodynamic line which corresponds
to the force at this point has consequently the form of a figure of 8, each of
the loops enclosing a focus with its surrounding ovals : this form is called by
geometricians a lemniscate ; there is but one such isodynamic line in the
extra-tropical part of each hemisphere , and it separates the isodynamics of
higher intensity than itself which are within the loops, each surrounding a
single point of maximum only, from those which correspond to weaker degrees
of force than that of the L-mniscate, and are exterior to it : each of the
exterior isodynamics surrounds both the foci, but without meeting or crossing
in the point between them : their general form is that of parallelism with tho
external figure of the lemniscate, but the inflections which produce the doublo
loop become progressively less marked in the isodynamics of weakest force.
If the two foci in an hemisphere were points of equal force, the ovals sur-
rounding e^ch would be similar in force and area, and the point at which ths
two systems would encounter each other would be half way between the foci.
Such, however, does not appear to be the case : the intensity at one of the
foci is greater than at the other : it is so in both hemispheres, and the ratio
of the force at the major and minor focus appears to be nearly the same in
both. The focus of greater intensity in the Northern hemisphere is in Ncrt1!
America, where its position has been ascertained, by a recent survey conducted
by Captain Lefroy of the Royal (British) Artillery, to be in the vicinity of
the S.W. shores of Hudson's Bay in 52° of latitude, (Phil. Trans. 1840.
Art. xvii). The weaker focus, of which the approximate position has been de-
termined by MM. Hansteen, Erman, and Due, is in the north of Siberia
about 120° of East longitude from Greenwich. The middle of the lemniscate
which encloses both, or the point where its loops are connected, appears to bo
NOTES. ]v
in the Polar Sea, to the North or North east of Bering's Strait, and consequently
nearer to the Siberian than to the American focus. The corresponding
ph&nomena of the southern hemisphere are not yet determined with an equa
precision, but appear to have the same general characteristics. The two major
foci, one in the northern, the other in the southern hemisphere, are not at
opposite points of the globe to each other, nor are the two minor foci. Sym-
metry as regards geographical distribution is also departed from in another
lespect: the foci in each hemisphere are not separated from each other by an
equal number of degrees of geographical longitude ; they are nearer to each
other in the southern than in the northern hemisphere.
It is well known that in the extra-tropical latitudes of the northern hemi-
sphere, the forces which attract the north end of a magnet (so called, because
in the greater part of the accessible portions of the globe it is that end
of the magnet which is directed towards the north), and repel the south
end, preponderate ; and that conversely, in the extra-tropical parts of the
southern hemisphere, the forces which attract the south end and repel the
north predominate. At both the foci of the northern hemisphere the pre-
dominance is of the forces which attract the north end and repel the south ;
and at both the foci in the southern hemisphere the converse is the case.
The line which separates the preponderance of the northern from that of
the southern attracting force, is a line drawn through the points in each
meridian of the globe where the intensity of the force is weakest on that
meridian. Every where on the north side of this line the preponderance of
the force attracting the north end of the magnet, and repelling the south,
increases ; and every where on the south side 6f the line the preponderance
of the force attracting the south end, and repelling the north, increases.
This line is not one of those which has been characterised or referred to
by M. de Humboldt, but it is an important one in the view which it enables
us to take of the magnctical relations of different portions of the globe.
Its inflections are various, as will easily be imagined Avhen it is considered
that they take place in conformity with forces which produce four points
of maximum on the surface of the globe unsymmetricaUy distributed, and
also unsymmetrical in respect to the intensity of the force at each. The
most remarkable inflection is the large convexity towards the south, which
advances into the southern Atlantic nearly to the latitude of 20° S., in
consequence of the wide separation which exists in that quarter between
the major and minor foci of the southern hemisphere.
The measurement of the magnetic force in parts of an absolute scale,
suggested by M. Poisson, and brought into use by M. Gauss, has added greatly
Ivi NOTES.
to the value of researches on he tterrestrial magnetic force, because the de-
terminations which are now made will be comparable with those which may
be made at future epochs. The unit of force in this scale is that amount of
magnetic force which, acting on the unit of mass through the unit of time, gene-
rates in it the unit of velocity. Taking the units respectively, as a grain, a
second, and a foot in British measure, the ratio of the force at the major
focus in North America determined by Captain Lefroy's survey is 13'9 ;
at the minor focus in Siberia, from the Observations of MM. Ilanstecn and
Due, it is 13-3 ; and at St. Helena, which is nearly on the line of least intensity,
and at its weakest par!",, and where cor.sc-quertly the force is nearly a
minimum on the surface of the globe, its value is 6'4. The observations
made in Sir James Clark Ross's expedition, referred to in page 175 of the
text, and which appear to have been made nearly in the centre of the highest
isodynamie oval, give 15'6 as the approximate value of the force at the major
focus in the southern hemisphere j whilst the observations of the same
voyage render it probable that the value at the minor focus does not much
exceed or much fall short of 14'9, which is in the same ratio to 15'6, as
13'3 to 13'9. It has been already noticed that the two foci are nearer to
each other in the south than in the north : assuming the general charge of
the two magnetic hemispheres to be the same, the greater proximity of the
two points of maximum in the south might readily be imagined to aug-
ment the force at both, whilst in the opposite geographical longitudes of
the hemisphere the intensity would be less than in the analogous positions
in the north : the isodynamie maps shew that such is the case, and give
reason to believe, that the charge of the two magnetic hemispheres may
not differ in the aggregate, although the distribution of the force at the
surface of the globe is not precisely similar.
The view which we are now enabled to take of the magnetic system of
the globe, by means of the knowledge which we have acquired of the mag-
neto-dynamic variations at its surface, furnishes an explanation of many features
in the isoclinal and isogonic lines which had previously occasioned per-
plexity. We now perceive why the higher isoclinals should be ellipses
instead of circles, and why there should be inflection* at opposite points of
the ellipse nearer to one of its extremities than to the other, causing the
Jsoclinal line to resemble in its general form a curve inclosing a lemniscate,
of which one of the loops should be larger than the other. This remarka-
ble conformation of the isoclinal lines has been well described by Erman,
ia Posy;. Ann. der Phys. vol. rd. We now see also a confirmation of the
"KOTES. Ivii
conclusion which the sagacity of Halley enalled him to draw more than
150 years ago (Phil. Trans. 1683, No. 148, p. 208), that the complexity
and seeming irregularity of the declination observed in different parts of the
earth were due to forces which must produce two points of greatest at-
traction in each hemisphere.
The interval which has elapsed since the phenomena of the magnetic force
have been an object of attention, has been too short to admit of any direct
inference being drawn in regard to the effect of secular change on the
isodynarnic lines : but an attentive consideration of features which are ob-
viously connected with each other in the three systems of elementary
lines, confirms — what indeed could scarcely have been doubted — that altera-
tions which are known to have taken place in the configuration and posi-
tion of the isogonic and isoclinal lines in the last two and half centuries,
have been accompanied by corresponding changes in the lines of equal force.
The influence of secular change appears chiefly to affect the portions of
the isodynamic lines which are most nearly connected with the two minor
foci : from considerations which need not be particularised here, these foci
appear to have moved in opposite directions — the Siberian from west to
east, and the minor focus in the south from east to west. The remarkable
closed systems of isogonic lines in Siberia and in the south Pacific, to which
M. de Humboldt has referred in page 171 of the text, and in note 152, appear
to have undergone a movement of translation in the same directions as the
minor foci. The ./Etiology of this science is of so remarkable a character,
that it seems not improbable that the secular changes, wliich now appear
to us the most mysterious branch of the phseuomena presented to our notice,
may eventually prove a means of conducting to a solution of the problem
of highest interest— that of the physical causes of terrestrial magnetism.
Although it is scarcely safe to anticipate that any portion of phenomena
may be less deserving of attention than another, yet, as M. de Humboldt
has remarked that meteorology must seek its foundations and its advance
first within the tropics, because the phsenomena may there be viewed under an
aspect of less complexitythan. elsewhere, — so the converse may be remarked
in respect to magnetism; inasmuch as the characteristics of the magnetic
system are less distinctly marked within the tropics than in the higher
latitudes, and the influences of the two hemispheres are so blended in the
inflexions of the magnetic lines within the tropics, that to understand them
it is necessary to have continually present in the mind the phenomena of both
Iviii NOTES.
hemispheres ; and it is not always easy to discriminate, without much patient
consideration, to which hemisphere a particular effect is due. — EDITOR.]
(159) p. 174. — The following is the historical account of the discovery of an
important law in terrestrial magnetism, that of the general increase of the
intensity of the force with the increase of magnetic latitude. When, in
1798, I was about to join the expedition of Captain Baudin, on a voyage of
circumnavigation, Borda, who took a warm interest in my intended proceed-
ings, proposed to me to observe, in different latitudes and both hemispheres,
the oscillations in a vertical plane of a needle moving freely in the magnetic
meridian, for the purpose of examining whether the magnetic force varied, o»
was every where the same. In my subsequent voyage to the equinoctial
regions, this investigation formed one of the principal objects which I had in
view. I observed the same needle perform in ten minutes, at Paris, 245 oscilla-
tions ; at Havanna, 246 ; at Mexico, 242 ; at San Carlos del Rio Negro (lat. 1°
53' N., long. 80° 40' W. from Paris) 216 ; on the magnetic equator, or on the
line where the inclination = 0, in Peru (in 7° 1' S. lat., 80° 40' W. long, from
Paris), only 211 ; and in Lima (12° 2' S. lat.) again 219 oscillations. I thus
found that at that time, 1799— 1803,— if the intensity of the total magneti*
force were taken as = 1,0000 on the magnetic equator,— in the Peruvian chain
of the Andes between Micuipampa and Caxamarca, it should be expressed, in
Paris, by 1,3482; in Mexico, by 1,3155; at San Carlos del Rio Negro, by
1,0480; and at Lima, by 1,0773. When, in a Memoir, the mathematical
portion of which belonged to M. Biot, I developed to the French Insti-
tute in the Seance du 26 Frimaire, An. xiii. de la Republique, this law
of the variable intensity of the terrestrial magnetic force, supporting it by
numerical values obtained by observations at 104 different points of the
Earth's surface, the fact was regarded as perfectly new. It was not until
after the reading of this Memoir, as Biot has said in it most distinctly,
(Lametherie, Journal de Physique, T. lix. p. 446, note 2,) and as I have re-
peated in my " Relation historique," T. i. p. 262, note 1, that M. de Rossel
communicated to Biot his six previous observations of the oscillations of a needl*
made between 1791 and 1794 in Van Diemen's Land, Java, and Amboina.
These observations shewed the law of decreasing force to exist also in the
Indian Archipelago. It seems reasonable to conjecture that this excellent
man had not recognised in his observations the regularity of the increase and
decrease of the magnetic intensity, since he had never spoken of this surely
not unimportant physical law to our common friends, Laplace,
NOTES. lix
Prony, and Biot, before the reading of my Memoir. It was not until 1808,
four years after my return from America, that his observations were published
in the Voyage d'Entrecasteaux, T. ii. pp. 287, 291, 321, 480, and 644.
The custom of expressing all observations of the magnetic force made in any
part of the globe in terms of the force found by me on the magnetic equator
in the North of Peru, in which arbitrary scale the force at Paris is taken ;is
= 1'348, has been continued, even up to the present time, in all the tables
of magnetic intensity which have been published in Germany (Hansteen's
Magnetismus der Erde, 1819, S. 71 ; Gauss, Beob, des Magnet. Vereins, 1838,
S.36— 39 ; Eruiau, Physikal. Beob. 1841,8.529— 579): m England, (Sabine's
Report on Magnetic Intensity, 1838, pp. 43—62 ; and Contributions to Ter-
restrial Magnetism, 1840, etseq.) : and in France, (BecquereljTraited'Electricite
et de Magnetisme, T. vii. pp. 354 — 367.) Still earlier than Admiral Rossel's
observations were those made by Lamanon, in the unfortunate expedition of
La Perouse, from its stay at Tenerifle, 1785, to its arrival at Macao, 1787,
and which were sent to the Academic des Sciences. It is known, with certainty,
(Becquerel, T. vii. p. 320), that they had reached the hands of Condorcet in
July, 1787 , but all the attempts which have been hitherto made to discover
them have proved fruitless. Captain Duperrey is in possession of a copy of a
very important letter, written by Lamanon to the then perpetual secretary of
the Academy, and which was omitted to be printed in the " Voyage de La
Perouse." It is expressly said in this letter, " Que la force attractive de
1'aiinant est moindre dans les tro^iques qu'en avancant vers les poles, et que
1'intensite magnetique deduite du nonibre des oscillations de 1'aiguille de la
boussole d'inclinaison change et augmcnte avec la latitude." If the Academy
had at that time thought itself justified iu anticipating the then hoped-for
return of La Perouse. and in making known a truth which was eventuallf
discovered independently by three travellers unknown to each other, Lamanok.
De Rossel, and myself, the theory oi% terrestrial magnetism would have been
advanced eighteen years earlier by the knowledge ot a new class ot phenomena.
This simple narrative of facts may, perhaps, be held to justify the statement con-
tained in the following passage of my " Relation historique," Vol. iii. p. 615 -. —
" Les observations sur les variations du magnetisme terrestre auxquelles jc me
suis livre pendant 32 aiis, au moyen d'instrumens comparables entre eux en
Ame'rique, en Europe et en Asie, embrassent, dans les deux hemispheres,
dcpuis les frontieres de la Dzoungarie chinoise jusque vers 1'ouest a la Mer da
Sud qui baigne les cotes du Mexique et du Pe'rou, un espace de 188° de
longitude, depuis les 60° de latitude nord jusqu'aux 12° de latitude sud. J'ai
VOL. I. 0 r<
IX NOTES.
regarde la loi du decroissement des forces magnetiques, du pole a 1'equateur,
comme le resultat le plus important de mon voyage americam." It is not
certain, but it is very probable, that Condorcet read Lamanon's letter of July,
1787, at a meeting of the Academy of Sciences at Paris ; and I regard such
reading as a sufficient act of publication (Anauaire du Bureau des Longitudes,
1842, p. 463). The first recognition of the law belongs, therefore, indis-
putably, to the companion of La Perouse ; but, long unheeded or forgotten, it
appears to me that the knowledge of the law of the variation of the magnetic
force with the latitude only obtained a real scientific existence by the publication
of my observations of 1798 — 1804. The object and the length of this note
will not be surprising to those who are familiar with the recent history of
magnetism, and the doubts excited by it, and who know, from their own
experience, that one attaches some value to that which has formed a subject
of constant occupation during five years of laborious research in tropical
climates, and in dangerous mountain journeys.
(16°) p. 175. — The greatest intensity of the magnetic force hitherto observed
on the surface of the Earth is 2,071, and the least, 0,706. Both are in the
southern hemisphere : the geographical position of the first is, lat. 60° 19' SM
long. 131° 20' E. from Greenwich, observed by Sir James Ross, where the in-
clination was 83° 31', (Sabine, Contributions to Terrestrial Magnetism, No. V.
Phil. Trans. 1843, p. 231). The minimum was observed by Erman in
20° 00' S., and 324° 57' E. from Greenwich, (Ermaii, Phys. Beob. 1841,
S. 570), at which point the inclination was 7° 56'. These values of the force
are in the ratio to each other of 1 to 2'933. It was long supposed that the
ratio of the greatest to the least intensity of the force on the surface of the
Earth was as 2 to 1 (Sabine, Report on Magnetic Intensity, p. 82).
[This note is slightly altered from the original, with M. de Humboldt's
concurrence, in order to bring it into more exact accordance with the facts. —
EDITOR] .
(161) p. 176. — Speaking of amber (sucdmim, glessum,) Pliny says, xxxvii.
8, " Genera ejus plura. Attritu digitorum accepta caloris anima trahunt in
se paleas ac folia arida quse levia sunt, ac ut magues lapis ferri ramenta
quoque." Plato, in Timseo, p. 80 ; Martin, Etudes sur le Time'e, T. ii. pp.
343—346 ; Strabo, xv. p. 703, Casaub, ; Clemens Alex. Strom, ii. p. 370,
.where a singular distinction is made between rb crovxtov and TO eAeirrpoi/).
If Thales, in Aristot. de anima, 1, 2, and Hippias, in Diog. Laertio, 1, 24,
ascribe to the magnet aud to amber a spirit, it is obvious that the word i
meant simply to express a force or a cause of motion.
NOTES. hi
0") p. 176.— "The magnet draws iron as amber attracts the smallest grains
of mustard seed. It is as if a mysterious breath of air passed through both,
and communicated itself with the swiftness of an arrow." Such are the
expressions used by Kuopho, a Chinese writer of the beginning of the fourth
century, in a speech in praise of the magnet. (Klaproth, Lettre a M. A. de
Humboldt, sur 1'invention de la boussole, 1834, p. 125).
(163) p. 177. — "The phenomena of periodical variations depend manifestly
on the action of solar heat, operating probably through the medium T)f thermo-
electric currents induced on the Earth's surface. Beyond this rude guess,
however, nothing is as yet known of the physical cause. It is even still a
matter of speculation whether the solar influence be a principal or only a
subordinate cause, in the phseuomena of terrestrial magnetism" (Observ. to
be made in the Antarctic Expedition, 1840, p. 35).
(164) p. 177.— Barlow, in the Phil. Trans, for 1822, Part i. p. 117 ; Sir
David Brewster, Treatise on Magnetism, p. 129. The influence of heat in
diminishing the directive force of the magnetic needle had been taught in the
Chinese work, Ou-thsa-tsou, long before the time of Gilbert and Hooke,
(Klaproth, Lettre a M. A, de Humboldt, sur 1'invention de la boussole,
p. 96).
O63) p. 178. — See the Memoir on Terrestrial Magnetism in the Quarterly
Review, 1840, Vol. Ixvi. pp. 271—312.
(l66) p. 178. — Vvfhen the first proposal to establish a system of observatories*
forming a net-work of stations, all provided with similar instruments, was
made by myself, I could hardly entertain the hope that I should actually live
to see the time when, thanks to the united activity of excellent physicists and
astronomers, and especially to the munificent and persevering support of two
governments, the Russian and the British, both hemispheres should be covered
with magnetic observatories. In 1806 and 1807, my friend, M. Oltmanns,
and myself, frequently observed the march of the declination needle at Berlin,
for five or six days and nights consecutively, from hour to hour, and often
from half hour to half hour, particularly at the equinoxes and solstices. 1
was persuaded that continuous uninterrupted observations (olservatio per*
petua), during several days and nights, were preferable to detached observations
continued during an interval of many months. The apparatus employed was
Prony's magnetic telescope, placed in a glass case, and suspended by a thread
without torsion, by which angles of 7 or 8 seconds could be read on a finely-
divided scale, placed at a distance, and illuminated at night by a lamp.
Magnetic perturbations, or storms recurring sometimes at the same hours for
Ixii NOTES.
several successive nights, led me even then to express an earnest wish for the
employment of similar instruments, to the east and west of Berlin, to enable
us to distinguish between general phenomena and those which might belong
to local perturbations from the unequally heated crust of the Earth, or the
atmosphere in which clouds are formed. My departure for Paris, and the
long political troubles of Europe, prevented the accomplishment of my wishes
it that time. The light which, in 1820, the great discovery of Oersted threw
on the intimate connection between electricity and magnetism, excited, after a
'ong slumber, a general and lively interest in the periodical variations in the
Earth's electro-magnetic charge. Arago, who had began several years before
at the observatory at Paris, with an excellent declination apparatus of Gambey,
the longest uninterrupted series of hourly observations existing in Europe, shewed,
by the comparison with simultaneous perturbations at Kasan, the great advantage
which might be derived from such comparisons. "When I returned to Berlin,
after a residence of eighteen years in France, I had a small magnetic observa-
tory erected during the autumn of 1828, not only for the purpose of con-
tinuing the work which I had begun in 1806, but also and especially for the
purpose of instituting a series of simultaneous observations, at concerted hours,
at Berlin, Paris, and at Freiberg, at the depth of 216 feet below the surface.
The simultaneity of the perturbations, and the parallelism of the movements
for October and December, 1829, were represented graphically at the time
in Pogg. Ann. Bd. xix. S. 357, Tafel i. — iii. An expedition, undertaken
under the orders of the Emperor of Russia, in 1829, to Northern Asia, gave
me an opportunity of carrying out my plan on a more extensive scale. It was
developed in the Report of a Commission specially appointed by the Imperial
Academy of Sciences ; and under the protection of Count Cancrin, Chef du
Corps des Mines, and the able direction of Professor Kupffer, magnetic stations
were established throughout Northern Asia, from Nicolaieff by Cathariuenburg,
Barnaul, and Nertchinsk, to Pekin. The year 1832, (Gottinger gelehrte
Anzeigen, S. 206), forms an epoch in the history of the science ; for it was
then that the illustrious founder of a general theory of terrestrial magnetism,
Friedrich Gauss, established in the Gottingen Astronomical Observatory
apparatus constructed on new principles. The magnetic observatory of
Gottingen was completed in 1834 ; and in the same year (Resultate der
Beob. des magnetischen Vereins im Jahr 1838, S. 135, und Poggend. Annalen,
Bd. xxxiii. S. 426), by the zealous and active assistance of an ingenious
physicist, "Wilhelm "Weber, Gauss's instruments and methods were made
known and brought into use throughout Italy, Sweden, and a large prrt »(
NOTES. Ixiii
Germany. A ** magnetic union," of which Gottingen was the centre, was
thus established, making simultaneous observations four times a year, be-
ginning from 1836, for periods of 24 hours. The appointed days, which
were called " magnetic term days," did not coincide with the epochs which I
had adopted and proposed in 1830, viz. those of the equinoxes and solstices.
Great Britain, thongh the nation which possesses the greatest trade and most
extensive navigation of the world, had hitherto taken no part in the movement
which, since 1828, had begun to promise such important results towards the
establishment of the science of terrestrial magnetism on a sure basis. In
April, 1836, by a request, addressed in a public manner directly to the then
President of the Royal Society of London, the Duke of Sussex, (Lettre de M.
de Humboldt a S. A. R. le Due de Sussex sftr les moyens propres a perfec-
tionner la connaissance du magnetisme terrestre par 1'etablissement de station*
magnetiques et d' observations correspondantes), I had the happiness of es~
citing in those who had so much in their power a feeling of interest in an
undertaking the enlargement of which had long been the object of my warmest
wishes. In this letter I urged upon the Duke of Sussex the establishment of
permanent stations in Canada, St. Helena, at the Cape of Good Hope, in the
Isle of France, in Ceylon, and in New Holland, — all localities which, five years
previously, I had pointed out as desirable. A joint physical and meteorological
committee, appointed by the Royal Society irom among its Fellows, proposed
to the government the establishment of fixed magnetic observatories in both
hemispheres, and, in addition, the equipment of a naval expedition for magnetic
observations in the Antarctic Seas. I need not here dwell on how deeply
science Is indebted to the great and zealous exertions, on this occasion, of
Herschel, Sabine, Airy, and Lloyd, and to the powerful support of the British
Association for the Advancement of Science at its meeting at Newcastle In
1838. In June, 1839, the magnetic Antarctic expedition was determined on,
and placed under the command of Captain James Clark Ross. It has now
returned, crowned with success and honour ; having enriched science with
most important geographical discoveries in the vicinity of the Southern Pole,
with simultaneous observations on eight or ten magnetic term days,— [and with
a determination of the lines of equal Declination, equal Inclination, and equal
Force, over three-fourths of the accessible portion of the high latitudes of the
southern hemisphere. — EDITOR.]
(167) p. 179. — Instead of attributing the internal heat of the Earth to the
transition from a nebulous to a solid state of the matter of which it is formedj
Ampere proposes what appears to me a very improbable hypothesis, in which
NOTES.
the heat is regarded as resulting from the lono'-contiTwed chemical action of a
nucleus, composed of the metals of the earths and alkalies, on an already
oxydized external crust. In his great work, " Theorie des phenomenes electro-
dynamiques," 1826, p. 99, he says, " On ne peut douter qu'il existe dans
riuterieur du globe des courants electro-magnetiques, et que ces courants sont
les causes de la chaleur qui lui est propre. Us naissent d'un noyau metallique
central compose des metaux que Davy nous a fait connaitre, agissant sur la
couche oxidee qui entoure le noyau."
(163) p. 179. — The remarkable resemblance between the magnetic and the
isothermal lines was first pointed out by Sir David Brewster in the Transac
tions of the Royal Society of Edinburgh, Vol. ix. 1821, p. 318, and in his
" Treatise on Magnetism," 1837, pp. 42, 44, 47, and 268. This distinguished
physicist supposes the existence of two poles of maximum cold in the northern
hemisphere ; one American (lat. 73°, long. 100° W., near Cape Walker) ;
and one Asiatic (lat. 73°, long. 80° E.) ; and he considers that these occasion
two meridians of maximum heat, and two meridians of maximum cold. In
the sixteenth century, however, Acosta taught the existence of four lines of
no declination, which he inferred from the observations of a very experienced
Portuguese pilot (Historia natural de las Indias, 1589, Lib. i. Cap. 17).
This opinion would seem to have had some influence on Halley's theory of
four magnetic poles, if we may judge from some discussions between Henry
Bond, Author of " The Longitude Found," 1676, and Beckborrow. See my
" Bxamen critique de 1'hist. de la Geographic," T. lii. p. 60.
C69) p. 179.— Halley, in the PhiL Trans. Vol. ixix. (for 1714—1716),
No. 341.
(17°) p. 180. — Dove, in PoggendoriTs Annalen, Bd. xx. S. 341, Bd. xix.
S. 388 : " The declination needle is acted upon nearly like an atmospheric
electrometer, of which the divergence increases until a spark (lightning) is
produced." See also the ingenious comparisons of Professor Kamtz, in his
Lehrbuch der Meteorologie, Bd. iii. S. 531—519; Sir David Brewster,
Treatise on Magnetism, p. 280. See also Casselmann's Observations (Mar-
burg, 1844), S. 56 — 62, on the magnetic properties of the galvanic flame, of
luminous arch, in a Buusen's carbon and zinc battery.
(1?1) p. 181. — Argelander, in the important Memoir on the Aurora which
he has incorporated in the " Vortragen, gehalten in der physikalisch-
okonomischen Gesellschaft zu Konigsberg," Bd. 1834. S. 257—264.
f1'2) p. 181. — On the results of the observations of Lottin, Bravais, and
8iV)«rstrom, who passed a winter at Bosekop on the coast of Lapland (Lat.
NOTES. v
70°), and saw 160 Auroras in 210 nights, see Comptes-rendus de 1'Acad.
des Sciences, T. x. p. 289, and Martins' Me'te'orologie, 1843, p. 453 ; also
Argelander, in the "Vortragen, gehalten in der Konigsberg Gesellsohaft,"
Bd. i. S. 259.
(173) p. 183. — Captain John Franklin, " Narrative of a Journey to the
Shores of the Polar Seas in the years 1819—1822," pp. 552 and 597 ;
Thienemann, in the Edinburgh Philos. Journ. Vol. xx. p. 366 ; Farquharson,
in the same journal, Vol. vi. p. 392; Wrangel, Phys. Beob. S. 59. Parry
saw the Aurora borealis in plain day-light (Journal of a Voyage performed in
1821 — 1823, p. 156.) A nearly similar observation was made in England
on the 9th of September, 1827 (Journal of the Royal Institution, 1828, Jan.
p. 489).
(174) p. 183. — On my return from America, I described, under the name
of " polar bands," cirro-cumuli, in which the small detached masses were
distributed at very regular intervals, as if by the action of repulsive forces.
I made use of the expression " polar bands," because their perspective points of
convergence usually appeared at first in the prolongation of the dipping needle,
so that the parallel lines of cirrus corresponded with the magnetic meridian.
Sometimes the point of convergence appeared to move first in one direction,
and then in the opposite ; and, at other times, to advance gradually in one
direction. These bands usually shew themselves completely formed only in one
quarter of the sky ; and their movement is first directed from south to north,
and then gradually from east to west. I do not think the movements can be
explained by variations in the currents of air in the higher regions of the
atmosphere. The bands are seen when the air is extremely calm, and the
sky very serene ; and they are much more frequent within the tropics than in
the temperate and frigid zones. I have seen the phenomenon develope itself
in a manner so strikingly similar on the Andes, at an elevation of 14000
French feet, almost under the equator, and in Northern Asia, in the plains of
Krasnojarski, to the south of Buchtarminsk, that it seems difficult not to
regard it as a process depending on very general and widely-diffused natural
forces. See the important remarks of Kamtz (Vorlesungen iiber Meteorologie,
1840, S. 146 ; and the more recent ones of Martins and Bravais (Meteorologie,
1843, p. 117.) Arago observed at Paris, June 23, 1844, in the day-time,
south polar bands, consisting of extremely light clouds, and saw dark rays
shoot upwards from an arc having an east and west direction. In page 181
of the text, mention is made of the appearance of black smoke-like rays in
brilliant nocturnal auroras.
Jxvi
•N'OTES,
.('"•) p. 184. — In the Shetland Islands, the auroral streamers are called
"the merry dancers" (Kendal, in the Quarterly Journal of Science, new
series, Vol. iv. p. 395.)
(176) p. 184. — See the excellent article of Muncke, in the last edition of
Gehler's Physikalisches Worterbuch, Bd. vii. 1, p. 113—268 ; and particularly
p, 15S.
, (l") p. 144.— Farqnharson, iu Ediiib. Pliilos. Journal, Vol. jvi. p. 304;
Phil. Trans, for 1829, p. 113.
(178) p. 187.— Kamtz, Lehrbuch der Meteorologie, Bd. in. S. 498 and 501.
P) p. 189.— On the dry fogs of 1783 and 1831, which appeared lumi-
nous at night, see Arago, in the Annuaire du Bureau des Longitudes. 1832,
pp. 246 and 250 ; and on some singular phenomena of light from clouds not
being storm or thunder clouds, in his " Notices snr le Tonnerre," in the
Annuaire pour 1'an 1838, pp. 279 — 285.
[Being at Loch Scavig, in the Island of Skye, in a friend's yacht, in Ancnst
1836, the summit of the mountain which rises on the east side of the
harbour to the height of 2000 feet or thereabouts, was enveloped during
the day by a thin veil of mist, extending 3 or 400 feet below the summit,
and so thin as to permit the outline of the hill, as well as the rocky in-
equalities of the surface, to be seen through it : as night came on the
mist remained, but became distinctly and decidedly luminous, still continu-
ing so thin that the hill was seen through it : towards 8 or 9 o'clock in
the evening, streamers of the Aurora ascended from it for about 10° or
15° towards the zenith, and continued to do so for an hour or thereabouts. —
EDITOR.]
(18°) p. 191. — Herod, iv. 28. The ancients were prepossessed with an idea
that Egypt is exempt from earthquakes (Plin. ii. 80) ; although the necessity
of restoring the statue of Memnon is, in some degree, evidence to the con-
trary (Letronne, La Statue vocale de Memnon, 1833, pp. 25—26.) It is,
however, true that the valley of the Nile is situated outside the earthquake
district of Byzantium, the Archipelago, and Syria (Ideler ad Aristol. Meteor
p. 584.)
(l81) |). 191. — Saint-Martin, in the learned notes which he has appended to
Lebeau's Histoire du Bas Empire, T. is. p. 401.
O p. 191.— Humboldt, Asie Ceritrale, T. ii. pp. 110—118. On the
difference between the agitation of the surface and that of the inferior st&ta,
see Gay-Lussac, in the Annales de Chiinie et de Physique. T. xxii. p. 429.
O p. 192.— Tutissimum est cum vibrat crispante aedificiortun crepito ;
NOTES. lxvii
et cum iuturaescit assurgens alternoque motu residet, innoxium et cum
concurrentia tecta contrario ictu arietant ; quoniam alter motus alteri renititur.
Undantis inclinatio et fluctus more qwedam volutio infesta est, aut cum in
unam partem totus se motus impellit (Plin. ii. 82).
(184) p. 193. — The absence of any connection between earthquakes, and the
state of the weather or appearance of the sky immediately preceding their
occurrence, begins to be recognised even in Italy. The numerical data
obtained by Friedrich Hofimann on this subject agree perfectly with the
experience of the Abbate Scina of Palermo. See F. Hoffmann's " hinterlassens
Werke," Bd. ii. S. 366—375. I have indeed myself observed more than
once the appearance of reddish clouds a short time before earthquake shocks ;
and on the 4th November, 1799, I experienced two strong shocks simul-
taneously with a violent clap of thunder (Relation historique, Liv. iv. chap. 10) ;
and a physicist of Turin, Vasalli Eandi, observed great disturbance in Volta's
electrometer during the long-continued earthquakes at Pignerol, which lasted
from April 2 to May 17, 1808 (Journal de Phys. T. lxvii. p. 291). But we
have no reason for regarding any of these phenomena, such as haze or clouds,
disturbances in the electric state of the atmosphere, or calms, as having any
general and necessary connection with earthquakes ; for in Quito, Peru, and
Chili, as well as in Canada and Italy, shocks have been felt when the sky
was most serene and free from clouds or haze, and when the freshest land or
sea breezes were blowing. But although we have no reason to believe that
earthquakes are preceded or accompanied by any particular meteorologies
indications, yet we ought not peremptorily to reject altogether the popular
belief of the influence of particular seasons, the vernal and autumnal equinoxes,
the settmg-in of tropical rains after long-continued drought, and the change
of the monsoons, solely because we do not at present understand the causal
connection which may exist between meteorological and subterranean pheno-
mena. Numerical data, collected with great care by M. de Hoff, Peter Merian,
and Friedrich Hoffmann, for the purpose of elucidating the comparative
frequency of earthquakes at the different seasons of the year, indicate a
maximum about the times of the equinoxes. It deserves notice, that Pliny, at
the end of his fanciful theory of earthquakes, terms these awful phenomena
"subterranean storms," not so much on account of the noise resembling
thunder, which often accompanies them, as from a notion that the elastic
forces which by their increasing tension thus agitate the ground, accumulate
beneath the sin-face of the earth when they are wanting in the atmosphere :
Ixviii NOTES.
Ventos iu causa esse non dubium reor. Neque enim unquam intremiscnnt
terree, nisi sopito mari cocloque adeo tranquillo, ut volatus avium non
pendeant, subtracto omni spiritu qui vehit ; nee unquam nisi post ventos con-
ditos, scilicet in venas, et cavernas ejus occulto afflatu. Neque aliud est in
terra tremor, quam in nulie tonitruum ; nee hiatus aliud quam cum fulmen
erumpit, incluso spiritu luctante et ad libertatem exire nitente (Plin. ii. 79).
We find in Seneca (Nat. dusest. vi. 4 — 31), the germ of all that has been
observed or imagined up to very recent times regarding the causes of
earthquakes.
(185) p. 193.— In my Relation historique, T. i. p. 311 and 513, I have
given evidence that the horary march of the barometer continues undisturbed
both before and after the occurrence of earthquake shocks.
(186) p. 194.— Humboldt, Rel. hist. T. i. p. 515—517.
(187) p. 196. — On the "bramidos" of Guanaxuato, see my Essai polit.
snr la Nouv. Espagne, T. i. p. 303. The town of Guanaxuato is situated
6420 French feet above the level of the sea. The subterranean thunder was
not accompanied by any sensible shock either in the deep mines or at the
surface : it was not heard on the neighbouring plateau, but only in the
mountainous part of the Sierra, from the Cuesta de los Aguilares, not far
from Marfil, to the north of Santa Rosa. The waves of sound did not reach
detached portions of the Sierra situated 24 to 28 miles north-west of
Guanaxuato, in the neighbourhood of the thermal spring of San Jose de
Comangillas beyond Chichimequillo. Measures of extraordinary severity were
adopted by the magistrates of the city, when the panic caused by the sub-
terranean thunder was at the highest. The flight of a family was punished by
a fine of 1000 piastres or by two months' imprisonment, and the militia were
commanded to arrest and bring back thfc fugitives. The most curious circum-
stance, however, was the confidence which the authorities, — " el cabildo," —
seemed to have reposed in their own superior knowledge, saying, in a proclama-
tion of the period, which I had an opportunity of seeing — "the magistracy in
their wisdom (en su sabiduria) will be well aware of the period of real and
imminent danger, should it arise, and they will then give orders for flight ;
but for the present it is sufficient to continue the processions." A famine
ensued, as the inhabitants of the tabb lands were prevented by their feara
from bringing corn to the town. The ancients were acquainted with tiie pirn:-
nomenon of subterranean noises unaccompanied ly earth aake : see Arislot.
Meteor, ii. p. 802 ; and Plin. ii. 80. The singular noiso which was heard in
the Dalmatian isknd of Meleda, 16 miles from. Bagusa, from March 1822 to
September 1824, was occasionally accompanied by shocks. Much light has
been thrown on this phceuomenon by Partsch.
(188) p. 198.— Drake, Nat. and Statist. View of Cincinnati, p. 232—238 ;
Mitchell, in the Trans, of the Literary and Philosophical Society of New
York, Vol. i. p. 281 — 308. In the Piedmontese county of Pignerol, glasses
filled to the brim with water exhibited agitation for several hours.
(189) p. 199. — The Spanish expression is, "rocas que hacen puente." These
local interruptions to the transmission of the shock through the zipper strata,
seem analogous to the remarkable phenomenon which took place in the deep
silver mines of Marienberg, in Saxony, at the beginning of the present cen-
tury, when earthquake shocks drove the miners in alarm to the surface, where,
meanwhile, nothing of the kind had been experienced. The converse phseno-
menon was observed in November 1823, when the workmen in the mines of
Palun and Persberg felt no movement whatsoever, whilst above their heads a
violent shock of earthquake spread terror among the inhabitants at the surface.
(19°) p. 200.— Sir Alex. Burnes, " Travels into Bokhara," Vol. i. p. 18 ;
Wathen, " Mem. on the Usbek State," in the Journal of the Asiatic Soc. of
Bengal, Vol. iii. p. 337.
(191) p. 201.— Phil. Trans. Vol. xlfr. p. 414.
(192) p. 202.— On the frequency of earthquakes in Kashmir, see Troyer's
translation of the ancient Radjatarangini, Vol. ii. p. 297 ; and Carl von
Hugel's Travels, Bd. ii. S. 184.
(193) p. 203. — Strabo, Lib. i. p. 100, Casaub. It is evident from another
passage (Strabo, Lib. vi. p. 412) that the expression ir^Aou Stairvsov VOTOL^V
signifies lava, and not erupted mud. Compare Walter, iiber Abnahme der
rulkanischen Thatigkeit in historischen Zeiten, 1844, S. 25.
(194) p. 205. — Bischofs valuable memoir, Warmelehre des inneren
Erdkorpers.
(195) p. 205.— On the artesian fire-wells (Ho-tsing) of China, and the anti-
quity of the use of portable gas (carried in tubes of bamboo) in the city of
Khiung-tscheu : see Klaproth, in my Asie centrale, T. ii. p. 519—530.
(196) p. 205. — Boussingault (Annales de Chimie, T. Hi. p. 181) did not
observe any hydrochloric acid in the exhalations from the volcanoes of New
Grenada ; whereas it was found in immense quantities by Mouticelli, during
the eruption of Vesuvius in 1813.
(')p. 206.— Humboldt, Recueil d'Observ. astronomiques, T. i. p. 311
(Nivellement barometrique de la Cordiliere des Andes, No. 206.)
ixx NOTES.
CM) p. 206.— Adolphe Brongniart, in the Annales des Sciences natu-
relles, T. xv. p. 225.
(1M) p. 207.— Bischof, Warraelehre des inneren Erdkorpcrs, S. 324,
Anm. 2.
(**>) p. 207.— Homboldt, Asie centrale, T. i. p. 43.
(S01) p. 208. — On the theory of the isogeothermal lines (chthonisothermals;,
gee the ingenious discussions of Kupffer, in Poggend. Ann. Bd. xv. S. 184,
and Bd. xxxii. S. 270 ; in his Voyage dans 1'Oural, p. 382—398 ; and in
the Edinburgh Journal of Sciences (New Series, vol. iv. p. 355). Compare
also Kamtz, Lehrb. der Meteor. Bd. ii. S. 217 ; and on the rising up of the
isogeotherrnals in mountainous countries, see Bischof, S. 174 — 198.
£°9 p- 208. — Leopold von Buch, in Poggend. Ann. Bd. xii. S. 405.
f3) p. 208.— See my Rel. hist. T. ii. p. 22. The temperature of drops
of rain at Cumana was 22°'3 C. (72°'2 Fah.), when that of the air was 30°
and 31° C. (86° to 88° Fah.) ; and during the fall of rain the temperature o
.the air sunk to 23'4 C. (about 74° Fah.) The initial temperature of the
drops depends on the height of the cloud in which they are formed, and on the
heat which its upper surface may have received from the direct effect of the
gun's rays ; but this temperature alters during their fall. The latent heat, set
free in their formation, causes them to have at first a temperature rather
above that of the surrounding medium ; and as they pass through lower and
warmer strata of air, this is somewhat raised, while at the same time their size
is increased by the condensation of the aqueous vapour contained in thos
strata. (Bischof, Warmelehre des inneren Erdkorpers, S. 73). The increase
of temperature from the cause described is, however, compensated by the loss
of heat which the drops undergo from evaporation from their surface. Apart
from the effect probably due to atmospheric electricity in thunder showers
the cooling influence of rain may be ascribed, first to the low initial tempera-
ture which the drops have acquired in the higher regions of the atmosphere,
and to the colder air of the higher strata which they bring down with them ;
and, lastly, to evaporation from the wet ground. This is the ordinary course
of the phenomenon; but in some rare instances (Humboldt, Rel. hist. T. iii.
p. 513) the drops are warmer than the lower strata of the atmosphere through
which they fall ? this may possibly be caused either by warm upper currents,
or by the heating of an extensive surface of thin cloud by the sun's rays.
Arago, in the Annuaire for 1836, p. 300, has shewn the connection
between the phenomenon of " supplementary rainbows," which are explained
by the interferences of luminous rays, and the size and increasing bulk of
NOTES.
Ixxi
falling drops of rain. This ingenious discussion also shews how, under certain
conditions, an accurately observed optical phenomenon may throw light on
difiicuit meteorological phsenomena.
(M) p. 208. — Boii'singault's researches appear to me to leave no douht on
the fact, that within tlie tropics the temperature of the ground, at a very small
depth below the surface, corresponds with the mean atmospheric temperature.
I subjoin a few examples : —
Stations.
Temperature at
the depth of
one foot.
Mean tempera-
ture of the air.
Elevation.
Guayaquil . . .
78-80° Fah.
78-08° Fah.
0 Eng.ft.
Anserma nuevo . .
74-66
74-84
3443
Zupia .....
70-70
70-70
4018
Popayan . • . .
64-76
65-66
5930
Quito .....
59-90
59-90
9559
The doubt respecting the temperature of the earth within the tropics, to
which T may myself have given occasion by my observations in the caves of
Guaripe Cueva del Guacharo (Rel. hist. T. in. p. 191 — 196), is removed by
considering that I compared the presumed mean temperature of the air at the
convent of Caripe (18°'5 C., 65°'3 Fah.), not with the temperature of the air
in the cavern (which was 18°'7 C., or 65°'6 Fah.) but with that of the sub-
terranean rivulet (16°'8 C., or 62°'2 Fah.), although I had before remarked
(Vol. iii. p. 164 and 194) that the waters of the cavern might very probably
be affected by waters coming from greater heights. [See addition to note 139.
—EDITOR.]
C205) p. 209.— Boussingault, in the Annales de Chimie, T. Iii. p. 181. The
temperature of the spring of Chaudes-Aigues, in Auvergne, is not more than
80° C. (176° Fah.) It may also be remarked, that while the aguas calientes
de las Trin cheras, south of Porto Cabello (in Venezuela), issuing from granite
divided in beds, show a temperature of 97° (206°'6 F.), all the springs on the
still active volcanoes of Pasto, Cotopaxi, and Tunguragua, have temperatures
of only 36° to 54° C. (96°'8 to 129'°2 Fah.)
t206) p. 210.— See the descriptions of the Kassotis (the fountain of St.
Nicholas), and of the Castalian spring at the foot of the Phedriades, in
Pausanias, x. 24 — 5, and x. 8 — 9 ; of the Pirenean spring (Acrocorinthus),
in Strabo, p. 379 ; of that of Erasinos (on the Chaon, south of Argcs), in
Ixxii NOTES.
Herodotus, vi. 67, and Pausanias, ii. 34, 7 ; of those of J2depsos in Eubsea (of
which some have a temperature of 31° C. (870>1 Fah.,) and others of 62° to
75° C. (or 143°'6 to 167°'0 F.,) in Strabo, p. 60, 447, and Athenams, ii.
3, 73 ; the hot springs of Thermopylae, at the foot of Mount Oeta, having
a temperature of 65° C. (149° Fah.,) are described by Pausanias, x. 21, 2.—
These references are taken from manuscript notes of Professor Curtius, the
learned travelling companion of Otfried Miiller
C207) p. 210.— Plin. ii. 106; Seneca, Epist. 79, § 3, ed. Ruhkopf; Beau-
fort, Survey of the Coast of Karamania, 1820, art, Yanar, near Deliktash, the
ancient Phaselis, p. 24. Compare likewise Ctesias, Fragm. cap. x. p. 250, ed
Bahr; and Strabo, lib. xiv. p. 665, Casaub.
f08) p. 211.— Arago, Annuaire, 1835, p. 234.
f») p. 211.— Acta S. Patricii, p. 555, ed. Ruinart, T. ii. p. 385, Mazochi.
Dureau de la Malle first called attention to this remarkable passage, in the
" Recherches sur la Topographic de Carthage," 1835, p. 276. (Compare
Seueca, Nat. Quaest. iii. 24.)
O210) p. 213.— Humboldt, Rel. hist. T. iii. pp. 562—567 ; Asie centrale, T. i,
p. 43, T.ii. pp. 505 — 516; Vues des Cordilleres, PI. xli. On the Macalubi (from
the Arabic Makhlub, overturned, from the root Khalaba,) and on "fluid
earth issuing from the Earth," see Solinus, cap. v. ; idem ager Agrigentinus
eructat limosas scaturigines, et ut vena3 fontium sufficiunt rivis subministrandis,
ita in hac Siciliae parte solo nunquam deficiente, ceterna rejectatione terrain
terra evomit.
C211) p. 214.— See the excellent little map of the island of Nisyros, in Rosa,
Ecisen auf den griechischen Inseln, Bd. ii. 1843, S. 69.
C212) p. 215.— Leopold von Buch, Phys. Beschreibung der Canarischsn
Inseln, S. 326 ; and the same author, tiber Erhebungscratere und Vulcane, in
Poggend. Ann. Bd. xxxvii. S. 169. Strabo distinguishes extremely well between
two modes of formation of islands, when he is speaking of the separation of Sicily
from Calabria, Lib. vi. p. 258. Casaub. He says, " Some islands are detached
parts of the main land ; others have been raised from the bottom of the sea,
as we still see. The islands of the open sea, i. e. those far from the shore,
have probably been raised from the bed of the sea ; and those situated near
promontories have been detached from the main land."
(213) p. 215. — Ocre Fisove (Mons Vesuvius.) The word owe is true Urn-
brian, and, according to Festus himself, signifies " mountain" in the ancient
Umbriaii language (Lassen, Deutung der Eugubinischen Tafeln, im Rhein.
NOTES.
Museum, 1832, S. 387). If, according to Voss, At-mj is of Grecian origin,
and connected with aiQw or ouQivos, Mtna would signify a burning and shining
mountain ; hut the learned Parthey doubts the Grecian origin, both, from
etymological considerations, and also because ./Etna could not have been a
beacon light for Greek navigators and travellers, like the continually-active
volcano, Stromboli (Strongyle), which Homer appears to refer to in the
Odyssey (xii. 68, 202, and 219), although the geographical position is only
very vaguely indicated. I imagine that the word jEtna would more probably
be found to belong to the language of the ancient Siculi, if any considerable
portions of it were in our possession. According to Diodorus (v. 6), the
Sicani, who were the aboriginal inhabitants of Sicily before the arrival of the
Siculi, were forced by the eruptions of JStna, which lasted several years, to
take refuge in the western part of the country. The oldest recorded eruption
of .(Etna is that mentioned by Pindar and ./Eschylus as having taken place in
the reign of Hiero, in the second year of the 75th Olympiad. Hesiod was
probably aware of devastating eruptions of ./Etna having occurred previous to
the Greek settlements. There are, however, some doubts respecting the word
AtrvTj, which I have discussed at some length in my Examen. critique de la
Geographic, T. i. p. 168.
(214) p. 215.— Seneca, Epist. 79,
O215) p. 215— JSlian. Var. hist. viii. 11.
(216) p. 218.— Petri Bembi Opuscula (^Etna Dialogus), Basil. 1556, p. 63;
" Quicquid in Mtuss matris utero coalescit, nunquam exit ex cratere supcriore
quod vel eo incendere gravis materia non queat, vel, quia inferius alia
spiramenta sunt, non fit opus. Despumant flammis urgentibus ignei rivi pigro
fluxu totas delambentes plagas, et in lapidem indurescunt."
(^ p. 218. — See my drawings of the volcano of Jorullo, of its " Hornitos,"
and of the upraised Malpays, in the Vues des Cordilleres, PI. xliii. p. 239.
O p. 219.— Humboldt, Essai sur la Geographic des Plantes et Tableau
physique des Regions equinoxiales, 1807, p. 130, and Essai geognostique sur
le gisement des roches, p. 321. A consideration of the greater part of the
volcanoes of the Island of Java is sufficient to shew that the entire absence of
lava currents, during a period of uninterrupted activity, cannot be ascribed to
the form, situation, and absolute elevation of the mountains. (Fide Leop.
von Buch, Descr. phys. des lies Canaries, p. 419 ; Reinwardt and Hoffmann,
in Poggend. Ann. Bd. xii. S. 607).
C219) p. 221. — See the comparison of my measurements with those of
NOTES.
Saussure and Earl Minto, in the Abhandlungen der Academic der Wiss. zu
Berlin aus den J. 1822 and 1823, S. 30.
(^ p. 222. — Pimelodes cyclopum, vide Humboldt, Recueil d' Observations
de Zoologie et d' Anatomic comparee, T. i. pp. 21 — 25.
C221) p. 224. — Leop. von Buch, in Poggend. Ann. Bd. xxxvii. S. 179.
C222) p. 224. — On the chemical origin of specular iron in volcanic masses,
see Mitscherlich, in Poggend. Ann. Bd. xv. S. 630 ; and on the disengage-
ment of hydrochloric acid gas in craters, see Gay-Lussac, in the Annales de
Chimie et de Physique, T. xxil p. 423.
(^ p. 226. — See the fine experiments on the cooling of masses of stone,
in Btschofs Warmelehre, S. 384, 443, 500—512.
P) p. 226.— Berzelius and Wdhler, in Poggend. Annalen, Bd. i. S. 221,
and Bd. xi. S. 146 ; Gay-Lussac, in the Annales de Chimie, T. xiiii. p. 422 ,
Bischof, Reasons against the Chemical Theory ol Volcanoes, in the English
edition of his Warmelehre, pp. 297—309.
(^ p. 227. — In Plato's geognostical ideas, as developed in the Phscdon,
the Pyriphlegethon plays nearly the same part, in respect to the activity of
volcanoes, as that which we now assign to the internal heat of the globe,
increasing with increasing depth, and to the state of fusion ot the deeper
strata. (Phtedon, ed Ast. pp. 603 and 607, Annot. pp. 808 and 817).
" Within and around the Earth there are subterranean channels of various
magnitudes. Water flows through them abundantly, as do currents of fire,
and streams of liquid mud, more or less impure, like the flow of mud which,
in Sicily, precedes the issuing forth of torrents of fire, both alike overwhelming
every thing in their path. The Pyriphlegethon pours itself into a wide space,
where a strong fire burns fiercely, and it there forms a lake larger than our
sea, in which the water and mud are always boiling; and, re-issuing thence,
it rolls its troubled and muddy waves around the earth." This river of molten
earth and mud is so far the general source of volcanic phenomena, that Plato
says expressly, in his continuation, " Such is the Pyriphlegethon, of which
the fiery currents (o< pvctKes), wherever they are found on the earth (OTTTJ av
Tux and
also in Abulgasi (Ilistoria Mongolorum et Tatarorum), the Kirghis are
called JCirkiz. Similarity of manners and customs, where the nature of the
country determines their principal characters, is a very uncertain evidence of
identity of race. The life of the steppes produces among the Turks (Ti Tukiu,)
the Baschkirs (Fins,) the Kirghis, the Torgodi, and the Dsungari (Mongolians,)
the customs common to a monade life, and the same use of felt tents, carried
on waggons, and pitched among the herds of cattle.
NOTES. CXV
t441) r. 354.— Wilhelm von Humboldt, iiber die Verschiedenheit dea
menschlichen Sprachbaues, in his great work, Ueber die Kawi-Sprache au£
der Insel Java, Bd. i. S. xxi. xlviii. and ccxiv.
(442) p. 355. — The cheerless and since often repeated doctrine of inequality in
men's right to freedom, and of slavery as an institution in conformity with nature,
is found, alas ! very systematically developed in Aristotle's Politica, i. 3, 5, 6.
f443) p. 357. — Wilhelm von Humboldt, iiber die Kawi-Sprache, Bd. iii.
S. 426. I here subjoin another extract from the same work, S. 427 :— " The im-
petuous conquests of Alexander, the more politic and deliberate extension of
the Roman dominion, the savagely cruel wars of the Mexicans, and the
despotic territorial acquisitions of the Incas of Peru, have contributed in both
hemispheres to terminate the segregation of nations, and to form more exten-
sive societies. Men of great and powerful minds, as well as whole nations,
acted under the dominion of an idea, to which nevertheless, in its moral purity,
they were entire strangers. Christianity first made known its true signifi-
cancy and profound charity : and even from her voice it has obtained but a slow
and gradual reception. Until that voice had spoken, a few solitary accents
alone foreshadowed this great truth. In modern times an increased impulse
has been given to the idea of civilization ; and the desire of extending more
widely friendly relations between nations, as well as the benefits of intellectual
and moral culture, is increasingly felt. Even selfishness begins to perceive
that its interests are thus better served, than by forcibly maintaining a con-
strained and hostile isolation. Language, more than any other faculty, binds
mankind together. Diversities of idiom produce, indeed, to a certain extent,
separation between nations ; but the necessity of mutual understanding
occasions the acquirement of foreign languages, and reunites men without
destroying national peculiarity."
INDEX TO VOL. I.
ACOSTA (Joseph de), Historia natural de las Indias, Notes 25, 168.
JSgos Potamos, meteoric stone of, p. 109, 124; Notes 62, 69, 87.
Aerolites, (falling stars, meteors, meteoric stones,) p. 105—127; Notes 58, 87.
Their cosmical and planetary character, p. Ill, 113, 116, 117; Notes 72, 78.
November stream of, p. Ill, 114—118; Notes 66, 70, 72, 75, 76. August
stream of, p. 112, 114, 116, 118; Note 71. Other annual epochs deserving
attention, p. 115 ; Note 74. Chinese accounts of aerolites, p. 118; Note 77.
Their planetary velocity, p. 51, 109, 112 ; Note 69. Proceed from a common
point in the heavens, p. Ill, 112. Their composition similar to that of ter-
restrial minerals, p. 51, 120, 121. Peculiarities, p. 119, 120, 121.
Agassiz, fossil fishes, p. 264 ; Notes 14, 300, 307. Glaciers, p. 328.
Amber, vegetable origin of, p. 273.
Amber-tree of the ancient world (Pinites succinifer), p. 273.
Ampere, on electro-dynamic forces, p. 179; Note 167.
Anaxagoras, on aerolites and the origin of heavenly bodies, p. 124 ; Notes 69, 89.
Andes, see Cordilleras.
Anghiera (the friend of Columbus), on the discovery of palms and pines growing
together, p. 272. On the gulf stream, p. 300. On the snow line under the
tropics, p. 327 ; Note 400.
Anning (Miss Mary), her discovery of an ancient sepia at Lyme Regis and of
coprolites, p. 260 ; Note 297.
Apian (Peter), direction of tails of comets, p. 94.
Apollonius Myndius, on comets, Note 48.
Arago, on chromatic polarisation, p. 37, 97 ; Notes 16, 51. On comets, p. 95, 97 ;
Notes 43, 45, 51. On the light of stars and nebulae, p. 142 ; Notes 31, 115, 119.
On magnetism of rotation, p. 169 ; Note 147. On magnetic storms, p. 180.
On the faint light of densely clouded nights and of certain fogs, p. 188 ; Notes
98, 179. On Artesian wells, p. 211 ; Note 208. On the temperature of the
Mediterranean, p. 296. On lightning, p. 335 ; Notes 416, 417. On meteoric
dust, Note 61. On a periodical fall of aerolites in April, Note 74. On the
increase of temperature at increasing depths, Note 138. On the supposed
existence of a line of no horary variation of the declination, p. 172; Note 153.
Hourly observations of declination at Paris, and simultaneous disturbance at
Paris and Kasan, Note 166 On " polar bands" of cirrous clouds, Note 174.
CXV111 INDEX.
On rain and supplementary rainbows, Note 203. On the constancy of tropi-
cal ocean temperatures, p. 296; Note 364. On the mean annual quantity of
rain in Paris, Note 405.
Argelander, on comets, p. 102. On the proper motion of the solar system, p. 135.
138; Note 102. On the aurora, p. 181 ; Note 17.1.
Aristarchus of Samos, his just cosmical views, p. 53.
Aristotle, Physics, p. 45; Note 21. On comets, p. 96; Note 48. On the eleva-
tion of an island of eruption, Note 230. On the red colour of long-fallen snow,
p. 344 ; Note 424.
Artesian wells, p. 162, 211 ; Notes 124, 138. See Springs.
Atmosphere, general account of, p. 304-312; Notes 375-389. Its composition
and adventitious admixtures, p. 305—307 ; Notes 375—380. Humidity of the,
p. 308, 330—333; Notes, 404—408. Electricity of the, 308, 333-336; Notes
409—418. Pressure of the, 307. See Barometer.
Aurora, general account of, 179-189; Notes 169—179. Description of, p. 180—
182. Cases of coincidence in appearance of aurora and falling stars or meteors,
p. 115, 116. Editor's description of an aurora in Loch Scavig, Note 179.
Aztec manuscript, supposed notice of zodiacal light, p. 129; Note 93.
Babbage, on the influence of temperature in the elevation and subsidence of
strata, Note 348.
Bacon, on physical similitudes in the configuration of the world, p. 282.
Baer (Von), on the meteorology of the northern regions, Note 418.
Barometer, variations of the, p. 307—310; Notes 381—388. Horary variations of
the, p. 308, 309.
Barometric windrose, p. 310 ; Note 387.
Batten (Mr.), letter on the limit of perpetual snow on the two declivities of the
Himalaya, Note 403.
Beaufort (Captain), observed emissions of gas on the Caramanian coast, p. 210.
Beaumont (Elie de), on the upheaval of mountain chains, p. 34, 291, 292; Note
357. On some of the geological causes of the influence exercised by the Alps
on pendulum experiments, Note 133. On the metamorphic action of primi-
tive rocks on secondary strata in the Tarantaise, p. 249 ; Note 272.
Beccaria, on luminous clouds, p. 188. On lightning clouds without audible
thunder, p. 335.
Beechey (Capt.), observations on sea temperatures and densities, Note 368.
Beer (Wilhelm), on the distance between the planet Saturn and its nearest satel-
lite, p. 89. On the dimensions and mass of the Moon, Note 40. On the
libration of the Moon, Note 41.
Belcher (Sir Edward), observation of magnetic disturbance at Macao, Note 143
(Editor).
Bembo (Cardinal), on eruptions ot Etna, p. 218 ; Note 216. Supposed theory of
ditto, Note 234. On the zones of vegetation on the acclivities of Etna, p. 346 ;
Note 429.
Benzenberg, on the velocity of the movements of aerolites, p. 112. On the perio-
dic return of the August meteors or aerolites, p. 115.
Berzelius, on the chemical elements of meteoric masses, p. 120, 121 ; Note 84.
On the changes of level of the Swedish coast, Note 35.
Bessel, on the theory of the oscillations of a pendulum in air, p. 26 ; Note 136
(Editor). Pendulum experiments with various substances, 51, 52. On the
parallax of 61 Cygni, p. 79, 103, 144 ; Note 34. On comets, p. 94—96 , Notes
INDEX. CX1X
46, 47, 50. On aerolites, p. 117; Note 70. On the proper motion of the
whole solar system, p. 134 ; Note 105. On the mass of 61 Cygni, p. 138 ;
Note 107. On measurements of meridian arcs, p. 157 ; Note 130. On the
possible influence of geological changes on gravitation, Note 349.
Biot, on twilight, p. 110, 133; Note 63, 100. Pendulum experiments, Notes 131,
133, 136 (Editor).
(Kdouard), on Chinese observations of comets, p. 94, 102. On Chinese
records of aerolites, p. 118 ; Note 77.
Bischof, on the internal heat of the globe, Notes 194, 199, 235, 261, 348.
Blumenbach, on races of men, p. 353.
Boguslawski, on a shower of aerolites in 1366, p. 118; Note 66.
Bon-iland and Humboldt, on the great fall of aerolites at Cumana, November
1799. Note 66.
Bopp, on Sanscrit roots, and on the derivation or the word Kosmos, Note 27.
Boussingault, on the depth below the surface of the earth at which the mean
annual temperature of the air is found at all seasons within the tropics, p. 165,
208; Notes 139, 204. On the earthquake in New Granada, 1827, p. 195. On
extreme dryness at Quito, p. 331, 332. On the decrease of temperature with
increasing altitude in the chain of Andes, Note 6. On the temperature of the
hot springs of Las Trincheras, p. 209. On the composition of the atmosphere,
p. 305 ; Notes 375, 379. On the mean annual quantity of rain at some places
in South America, Note 406.
Bouvard, discussion on the question of a lunar atmospheric tide, and failure in
detecting it in the barometric observations at Paris, Note 381.
Bramuios y truenos, loud subterranean noises heard at Guanaxuato, p. 196;
Note 187.
Brandies, on the velocity of the motion of aerolites, p. 112. On the diameter of
ditto, Note 62. On the elevation of ditto, p. 112; Note 67. On a fall of
ditto in December 1798, Note 74.
Bravais, on the aurora, p. 185, 187. On the horary variation of the barometer in
70U N. latitude, p. 309 ; Note 383. On the height of the lines of the ancient
sea level near North Cape, p. 287 ; Note 352. On the amount of rain in
different seasons in middle Europe, Note 405.
Bronguiart (Adolphe), luxuriance of the ancient vegetation independently of lati-
tude, p. 206. On the fossil flora of the coal formation, p. 270 ; Note 323.
• (Alexandre), on fossil geology, p. 262.
Brown (Robert), on peculiar molecular movements in vegetables, and generally
in matter reduced to an extreme state of division, p. 340.
Buch (Leopold von), theory of the elevation of mountain chains and continents,
p. 27, 286 ; Note 357. On craters of elevation and the circular form of the
island of Palma, p. 214 ; Note 212. On volcanoes and volcanic islands, p. 228,
230, 235; Notes 226, 231. On metamorphic action, p. 249, 252, 255; Notes
271, 282, 288. On the changes of level of the Scandinavian coasts, p. 287.
On the origin of the dolomite and masses of granular limestone containing1
garnets, &c. in the neighbourhood of Vesuvius, p. 224; Note 221. On a re-
cent sea-formed bank of oolite near Lancerote, p. 238 ; Note 245. On the
origin of certain conglomerates, p. 258; Note 296. On ceratites, arietes,
and goniatites, p. 266; Note 311. On the origin of erratic blocks, p. 274;
Note 333. On the barometric windrose, Note 387.
(Buckiaud, on coprolites, Note 297. On the floras of the coal formation and brown
coal, Notes 32j, 332.
CXX INDEX.
i
Buffon, on the geographical distribution of animals, p. 347.
Burckhardt, on the volcano of Medina in 1276, p. 234.
Burnes (Sir Alexander), on aerolites, and on the serene sky and transparent
atmosphere of Bokhara, p. 107 ; Note 60.
Caldas, on the annual quantity of rain at Santa Fe de Bogota, p. 331.
Caldecott, on the existence of an annual variation of temperature at a depth of
six French feet at Trevandrum, Note 139, (Editor).
Capocci, recurring falls of aerolites, p. 115; Note 74.
Carlini, pendulum experiments, Note 136, and additions by Editor.
Carus, his definition of " nature," p. 22 ; Note 11.
Casselmann, on the magnetic properties of the galvanic aame, Note 170.
Cassini (Dominic), on the zodiacal light, p. 129, 130; Notes 92, 96. On the CQm,
pression of Jupiter, p. 155 ; Note 129.
Cautley and Falconer, gigantic fossil land tortoise from the Himalaya, p. 268.
Cavanilles, watched the rapid growth of a bamboo shoot by means of the wires
of a telescope, p. 139.
Cavendish, application of the torsion balance to the determination of the mean
density of the earth, Note 136, and addition by Editor.
Celestial phenomena, p. 73— 145; Notes, 31— 123.
Chardin, comet of 1668, called " nyzek" by the Persians, p. 129 ; Note 92.
Charpentier, on glaciers, p. 328. Fossil remains in granular, or so-called primi-
tive, limestone, Notes 272, 277.
Chemical affinity, p. 50.
Chevandier, calculations of the small amount of carbon derivable from a given
area of the present forests of the temperate zone, p. 271 ; Note 327.
Childrey, gives the first notice of the zodiacal light in 1661, p. 129, 130 ; Note
91.
Chinese accounts of aerolites, p. 117, 118. Of comets, p. 92, 94, 102; Note 42,
Of " fire springs," Note 124. Of magnetic attraction, p. 176 ; Note 162. Use
of magnetic compass, p. 169. Notice of streams of lava, p. 233.
Chladni, on aerolites, meteoric stones, &c. p. Ill, 113, 123, 125; Notes 65, C9.
" Figures of sound," p. 125.
Chromatic polarisation, -see Light.
Cirro-cumulus, see Clouds.
Cirro-stratus, see ditto.
Clarke's experiments on atmospheric electricity at Dublin, p. 334.
(J. G., of Maine, U.S.), description of the comet of 1843, Note 43.
Clausen, on comets, p. 101. On the plutonic action of dioritic veins in Brazil,
p. 255.
Climatic distribution of heat, p. 307.
Climatology, general account of, p. 312—327 ; Notes 390—397.
Clouds, luminous, p. 188. Seen above shoals, p. 302, 303. Dove's remarks on,
p. 311. Sometimes present a "projected image" of the inequalities of the
surface of the ground beneath, p. 311. Connection of cirro-cumulus and
cirro-stratus with changes of temperature, &c. p. 338. Connection of cirro-
stratus with aurora, p. 182, 183; Note 174. Thunder clouds, their electric
state, colour, appearance, altitude, &c. p. 334, 335; Note 415. Volcanic,
formed of volcanic steam, p. 222, 223.
Coal, formed from the vegetation of the ancient world, p. 269, 271 ; Note 326, 32».
Coal measures, depth of, p. 150 ; Note 125.
INDEX. CXX1
Colebrooke, on the height of the snow line on the two declivities of the Himalaya,
Note 5.
Colladon, electro-magnetic apparatus, p. 333.
Columbus, found no variation of the compass near the Azores in 1492, p. 170, 171 ;
Note 151. Remarks that palms and pines grow together on the coast of
Cuba, and distinguishes Podocarpus from Pinus, p. 272; Note 329. His
notice of the equatorial current, p. 300 ; Note 370. Of the Sargasso sea or
portion of the ocean covered with Fucus natans, p. 301. His dream, p. 304 ;
Note 374.
Comets, general account of, p. 91—105 ; Notes 42—57. Supposed danger of their
collision with the earth, p. 24, 25, 100. Small density of, p. 77, 96 ; Notes
49, 50. Multitude of, p. 91. Small mass of, p. 100. Paths of, and distances
from the sun, p. 98—104, 133. Chinese accounts of, p. 92, 93 ; Notes 42, 77.
Fears occasioned by, in former times, 104, 105 ; Note 57. Imaginary connec-
tion of, with a fine vintage, p. 105. Examination of the light of, by chromatic
polarisation, p. 97 ; Note 51. Changes in the appearance of comets and appa-
rent vibrations in tails, p. 94, 95, 91, 132 ; Notes 45, 46, 99. Comets of short
period, p. 99—102. Of long period, 102. Comet seen in Persia in 1683, and
called " nyzek," or small lance, p. 129; Note 92. Biela's, p. 25, 77, 99, 104,
Blanpains, p. 101. Clausen's, 101. Encke's, p. 24, 25. The existence of a
resisting medium inferred from the diminishing period of revolution of
Encke's comet, p. 24, 77, 98, 99. Faye's, p. 101. Halley's, p. 94, 97, 99, 101,
102. Lexell and Burkhardt's, p. 101, 103. Messier's, p. 101. Olbers's,
102. Pons's, p. 102. Possible encounter of Biela's and Encke's comets,
p. 100. Comet of 1843, p. 94 ; Note 43.
Compass, early knowledge by the Chinese, p. 169.
Condamine (La), inscription on a monument at Quito on the length of the seconds*
pendulum at the equator, and on the Peruvian arc of the meridian, Note 131.
Conde", notice of a great fall of aerolites seen in Arabia in October 902, Note 66.
Coraboenf and Delcros, geodesic determinations near the line of the Pyrenees,
shewing that no sensible difference of level exists between the Atlantic and
Mediterranean, p. 297 ; Note 366.
Cordilleras, scenery and vegetation of the, p. 9, 11—13.
Cosmos, author's purpose in the essay on the, p. 32, 57—60. Discussion of the
term, and of the meaning of the science of the, p. 55—58, 68 ; Note 27.
Cosmography, p. xix, of the Author's Preface. P. 57, 73—79.
Craters of elevation, p. 214—216; Note 211, 212. See Volcanoes.
Curtius, temperatures of several springs in Greece, Note 206.
Cuvier (George), with Brongniart, pre-eminently the founders of the science of
fossil geology, p. 262, 264. Fossil crocodiles in tertiary formations, p. 263.
Daimachos, fall of the stone of Mgos Potamos, Note 87.
Dalman, on the Chionaea araneoides found in snow, p. 344.
Dalton observed aurora australis in England, p. 183. On the dew-point, p. 330.
Daniell, on the dew-point, p. 330.
Darwin (Charles), on vegetable fossils in the travertin of Van Diemen Island,
p. 212. Analogy of the floras of the southern temperate regions with fossil
floras, p. 272 ; Note 330. On changes of level in the sea bottom of the Pacific,
p. 288; Note 355. On the abundance of organic life in the ocean, p. 303.
On the sand which sometimes falls on the Cape Verd Islands, p. 307. On the
fiords of the south-eastern termination of South America, Note 347, Ou
CXX11 INDEX.
the parallel roads of Glen Roy, Note 352. On the altitude of the volcano of
Aconcagua, seen on one occasion entirely denuded of snow, p. 329 ; Note 402.
Davy (Sir Humphry), renounced his chemical hypothesis of volcanic eruptions,
p. 226. On a cause of the low temperature of water on shoals, p. 302.
Daussy, investigations on the influence of the height of the barometer on the level
of the sea, p. 290, 310. Computation of the velocity of the equatorial current,
p. 300.
Dechen (Von), on the depth of the Liege coal basin and of certain mines, Notes
124, 125.
Delcros, see Coraboeuf and Delcros.
Density of comets, earth, planets, &c. see those heads respectively.
Descartes, fragments of an intended work, entitled " Monde," p. 55. On the
tails of comets, Note 92.
Deshayes and Lyell, on the numerical relations of the successive types of organic
life, p. 264.
Dicearchus, on the greatest extent of the old continent from east to west, some-
times termed the "parallel of the diaphragm of Dicearchus," p. 280, 281.
Diogenes of Apollonia, on aerolites (especially the stone of ^Egos Potamos), and
on the origin of heavenly bodies, p. 124.
D'Orbigny, fossil ammonites and gryphaea from the Himalaya, p. 266.
Dove, "law of rotation" of the winds, p. 310; Note 388. On the form of clouds,
p. 311. On the hygrometric windrose, p. 331 ; Note 404. On the resem-
blance between the disturbance of the needle during an aurora anil the move-
ments of an atmospherical electrometer, Note 170. On the diurnal variation
of the pressure of the dry air at Buitenzorg in Java, Note 382 (Editor). On
the difference of the heat received by the ground and the indications of a
thermometer placed in the shade, Note 396.
Doyere, experiments on infusoria, Note 425.
Drake, tremblings of the earth in the United States in 1811 and 1812, p. 198;
Note 188.
Due, magnetic observations in Siberia, Note 158 (Editor).
Dufre"noy with Elie de Beaumont, Description ge"ologique de la France, Notes
238, 254, 260, 270, 276, 284.
Dumas, chemical analysis of the atmosphere, p. 305; Note 378.
Dtfperrey, magnetic equator, p. 172 ; Note 155. Pendulum experiments, Note 131.
Duprez, influence of trees on atmospheric electricity, p. 334 ; Note 413.
Earth, its place in the solar system, p. 82. General view of the earth, p. 145—
154; and terrestrial phenomena generally, 145, 357. Figure of the, p. 30,
154—159; Notes 127—135. Density of the, p. 159—161 ; Note 136. Tempe-
rature of, p. 161—167 ; Notes 137—140. Mean temperature unchanged from
the time of Hipparchus, p. 165, 166 ; Note 140. Early high temperature,
p. 28, 161—164. Internal heat at increasing depths, p. 27, 151, 162—164,
189 ; Notes 137, 138. Reaction of the interior on its exterior generally, p. 27,
189—235. General view of this reaction, 189—191.
Earthquakes, p. 191—205; Notes 180—193. Peculiar impression produced by
earthquakes on men and animals, p. 204. Of Riobamba, p. 192, 193. Of
Lisbon, p. 197. Noises accompanying earthquakes, p. 194 — 197.
Eandi (Vasalli), on electric disturbance during earthquake movements in Pied-
mont, Note 184.
Editor, his Preface, p. vii.— ix. Notes added by him to Notes 132 and 136, on
INDEX. CXX111
the pendulum. To Note 139, on the depth of the stratum of invariable tem-
perature within the tropics. To Note 143, on magnetic disturbances. To
Note 158, on the isodynamic magnetic lines. To Note 160, on the greatest
and least intensity observed on the globe. To Note 166, on magnetic obser-
vatories and expeditions. To Note 179, on luminous fogs, mists, and clouds,
and their connection with aurora. To Note 373, on oceanic currents. To
Note 381, on the lunar atmospheric tide at St. Helena. To Note 382, on
barometric variations.
Ehrenberg, infusoria in polishing slate, chalk, and other mineral substances,
p. 28, 141, 265, 343; Notes 308, 421,424, 425, 426. Infusoria in the ocean
and polar ice, p. 341. On the peculiar structure of chalk, Note 276.
and Humboldt, summer range of tigers in Asia, p. 348 ; Note 430.
Electricity, its connection with magnetism, p. 175, 176, 179; Notes 163, 167;
Atmospheric electricity, p. 308, 333—336 ; Notes 409 — 1!8.
Electro-magnetic currents and electro-magnetism, p. 32 ; Note 167.
Elevation (Von Buch's theory of the elevation of) mountain chains and of conti-
nents, p. 27, 286. See Mountains, and Beaumont (Elie de.)
ndogenous, see Rocks.
Ellicott, Cumana fall of meteors in 1799, p. 115; Note 72.
Encke, computation of the point in space from which the aerolites of the great
shower of 1833 proceeded, p. Ill ; Note 66. (Also, see Comets.)
Ennius, p. 57 ; Note 28.
Epicharmus, p. 57 ; Note 28.
Eratosthenes, p. 281, 283.
Erman (Adolph), on the three cold days of May, p. 123 ; Note 86. On declination
lines in Asia, &c. p. 171; Note 152. On the magnetic intensity, p. 175;
Notes 158 (Editor), 160. Non-disturbance of the horary variations of the
barometer and declination needle during an earthquake, p. 193. Isoclinal
magnetic lines, Note 158 (Editor).
Erratic blocks, p. 274.
Eruptions (volcanic) of various substances from the earth,— lavas, mud, water,
gas, &c. p. 147, 200—302, 205—207 ; Notes 193, 195, 196.
Exogenous, see Rocks.
Falconer, Himalaya fossil land tortoise, p. 268.
Faraday, radiant heat, electro-magnetism, and magnetism, p. 32, 169, 175, 176;
Note 146. Evolution of light by the action of magnetic forces, p. 179.
Farquharson, on the aurora, Notes 173, 177.
Faye, p. 101 ; Note 55. See Comets.
Fedorow, pendulum experiments, Note 133.
Feldt, aerolites, p. 114.
Feldspar crvstals accidentally produced in a furnace, Note 293.
Ferdinandea, elevation of the island of, p. 231.
Fogs, luminous, p. 131; Note 179. Mephitic, p. 307.
Forster (George) difference of temperature between eastern and western coasts,
p. 317; Note 391.
(Reinhold) pyramidal form of continents, p. 282.
- (Dr. Thos.) adduces an early notice of the August aerolites, Notes 71, 73.
Fossil remains of plants and animals, p. 251, 259—274; Notes 279, 298—332.
1 suited to a tronical climate now found in cold and temperate
regions, p. 28.
Foster (Captain), pendulum experiments, Note 131.
VOL. I. f K
INDEX.
Fourier, terrestrial heat, p. 146, 162, 166 ; Note 137.
Fracastoro, direction of the tails of comets, p. 94.
Franklin (Benjamin), low temperature indicative of the presence of shoals, p. SOIL
-- (Captain) on the aurora, p. 182, 185, 187 ; Note 173.
Freycinet, pendulum experiments, Note 131.
Galileo, p. 177 ; Note 49. Vibrations of pendulums, p. 157.
Galvani, first discovery of galvanism, p. 36.
Gasparin, rain In Europe, Note 405.
Gauss, on terrestrial magnetism, p. 168 ; Notes 142, 145, 154, 158.
Gaudin, artificial production of rubies, Note 294.
Gay-Lussac, electric tension of surfaces of cloud, p. 223 ; Note 415. Chemical
analysis of the atmosphere, p. 305 ; Notes 380, 394. Hygrometric observations
in aerostatic ascent, p. 332. Specular iron, Note 290.
Geography, comparative and general, by Carl Ritter, p. 30, 54; Note 26. By
Bernhard Varenius, p. 54 ; Note 25.
-- physical, p. 35, 45—49, 2*8-338.
- of plants and animals, p. 47—49, 339, 345—350.
-- palaeo, p. 274—278.
Geological description of the earth's surface, p. 236—278; Notes 241—383.
Gerard (Captains Alexander and John), on the height of the snow-line, and on
vegetation on the two declivities of the Himalaya, Notes 5, 403.
Geyser, intermitting fountains of, p. 209.
Giesecke, on the aurora, p. 185, 186.
Gilbert (Sir Humphry), on the gulf stream, p. 300.
- (William), terrestrial magnetism, Notes 141, 144. Line of no declination
in 1600, Note 151.
Gillies (Dr.), snow-line in Chili, p. 329 ; Note 402.
Girard, composition of basalt, p. 241.
Goethe, p. 29, 37 ; Notes 15, 17.
Goldfuss, remains of flying saurians, Note 305.
GOppert, origin of amber, amber tree, and ancient v gelation of the Baltic, p. 273,
274 ; Note 326. Fossil cycadeae, Notes 320, 331.
Granite, p. 238—240, 275, 276 ; Notes 249, 260.
Grimm (Jacob), fanciful meaning given to falling stars m the Lithuanian mytho-
logy, Note 58.
Gulf-stream, p. 300, 301 ; Notes 370-373 (Editor).
Hall (Sir Jas.), experiments on the fusion of mineral substances, p. 250; Note 261.
Halley, large meteor, p. Ill ; Note 87. Light of stars, p. 142. Hypothesis concern-
ing terrestrial magnetism, p. 161 ; Note 136. Connection of aurora with mag-
netism, p. 179 ; Note 169. Just view of the general phenomena of terrestrial
magnetism, Note 158 (Editor).
Hansen, mass of the moon, Note 40.
Hansteen, magnetic declination lines in Asia and the Pacific, p. 171 ; Note 152.
Magnetic intensity in Siberia, Note 158 (Editor).
Hearne, aurora, p. 186.
Hedenstrom, " wood hills" in New Siberia, Note 327.
Hegel, quotation from, p. 64.
Heine, crystals of feldspar accidentally produced in a furnace, Note 293.
Heinsius, changes of form observed in the comet of 1764, p. 94.
Henderson, aurora, p. 186.
INDEX. CX*V
Herodotus, speaks of Scythia as free from earthquakes, p. 191 ; Note 180. Golden
shower (supposed aerolites), Note 61.
Herschel (Sir William), inscription on his monument at Upton, p. 78. Discovered
two of the satellites of Jupiter, p. 87. Diameter of comets, p. 93 ; Note 44.
"Star gauging," p. 140. Starless spaces, p. 142, 143; Note 117. On
the time required for the light of the remotest nebulae to reach the earth,
p. 144 ; Note 121. Comet of 1811, Note 46.
— . (Sir John), Magellanic clouds, p. 76 ; Note 32. Retrograde movement
of satellites of Uranus, p. 90. Diameter of nebulous stars, p. 130. Saw, at
the Cape, ^ Argus suddenly increase in brightness, p. 144 ; Note 120. Trans-
lation from Schiller, Note 9. Volume and light of planetary nebulae, Note 95.
Describes a nebula resembling our sidereal system, p. 141 ; Note 112. Light
of single stars and clusters, p. 142; Note 114. Magnetic declination un-
changed in West Indies, p. 170 ; Note 150. Number of observations in the
present system of magnetic observations, noticed in an article on magnetism
in the Quarterly Review, p. 178 ; Note 165.
Hevelius, change of volume in the nucleus of a comet, p. 98.
Himalaya Mountains, their elevation, p. 10 ; Note 2. Their vegetation, p. 10 ;
Notes 3, 4. Elevation of snow-line on their northern and southern declivities,
p. 10, 11 ; Notes 5, 403.
Hippalos, see Monsoons.
Hodgson, snow-line in the Himalaya, Note 403.
Hoff, estimation of the frequency of earthquakes at different seasons, Note 184.
Hoffmann (Friedrich), ditto, Note 184. Fissures of eruption m the Lipan Islands,
Note 226.
Hood, aurora, p. 186, 187.
Hooke, anticipations of the modern science of fossil geology, p. 260 ; Note 297.
Undulations of the tails of comets, Note 99.
Horary variations of the barometer, p. 307—309 ; Note 381—383. Undisturbed by
earthquakes, p. 193 ; Note 185.
magnetic declination, p. 171, 172; Note 153. Undisturbed
by earthquakes, p. 193.
Ho-tsing (Chinese fire-springs), Notes 124, 195.
Howard, mean quantity of rain in London, Note 405.
Hugel (Carl von), snow-line on the Himalaya, Note 403.
Humboldt (Alexander von), titles of works referred to : —
Abhandlungen der Akad. der Wissensch. zu Berlin, Notes 219, 397.
Annales de Chimie et de Physique, Notes 5, 275, 403.
Annales des Sciences Naturelles, Note 2.
Annalen (Poggendorft), Notes 157, 227, 347, 384.
Ansichten der Natur, p. xx. (preface), Notes 422, 428.
Asie centrale, Notes 2, 5, 6, 124 (twice), 149, 182, 200, 210, 237, 249, 252,
285, 339, 340, 342, 353, 358, 359, 360, 363, 365, 366, 390, 393, 396, 401.
403, 407, 430, 440.
Atlas g^ographique du Nouveau Continent, Notes 6, 241.
De Distributione Geographica Plantarum, Notes 394, 395.
Deutschen Vierteljahrs-Schrift, Note 315.
Essai sur la Geographic des Plantes, Notes, 6, 218, 384.
g^ognostique sur le Gisement des Roches, Notes 218, 285.
politique sur la Nouvelle Espagne, Notes 79, 187, 229.
Examen critique de 1'Histoire de la Geographic, Notes 92, 128, 148, 151,
213, 336, 344, 370, 371, 372, 373, 374, 388. 440.
CXXV1 INDEX.
Flora Fribergensis, Notes 420, 427.
Journal de Physique, Note 346.
Lettre au Due de Sussex, Notes 143, 166.
Me"moires de la Socie'te' d'Arcueil, Note 393.
Monumens des Peuples indigenes de 1'Am^rique, Note 93.
Recueil d'Observations astronomiques, Notes 2, 131, 197, 399.
de Zoologie et d' Anatomic compare, Note 220.
Relation historique du Voyage aux Regions equinoxiales, Notes 60, 66, 69,
72, 81, 144, 159 (twice), 184, 185, 186, 203, 204, 210, 244, 250, 342, 346,
356, 358, 362, 366, 369, 382, 384, 399, 414.
Synopsis Plant. ^Equinoct. Orbis Novi (Humboldt et Bonpland), Note 328.
Tableau physique des Regions Equinoxiales, Note 218.
Humboldt (Wilhelm von), early seat of Hindoo civilization, p. 14. Quotation from
sonnets, p. 145; Note 122. Extract from an inedited manuscript, p. 356. 357.
On the Kawi language, Notes 8, 441. On the union of mankind, Note 143.
Humidity, p. 308 ; see Hygrometry.
Hutton (Lieutenant), on the snow-line in the Himalaya, Note 403.
Huyghens, polarisation of light, p. 37.
Hygrometry, p. 330— 333; Notes 404-408.
Hypogene rocks, Note 241.
Jacquemont (Victor), on the snow-line and vegetation on the two declivities of the
Himalaya, Note 5.
Imbert, Account of Chinese Fire-springs, Note 124.
Impressions, mental, produced by different kinds of natural scenery, p. 6, 7. By
the view of the ocean, p. 303, 304.
Inclination, magnetic, see Magnetism and Lines.
Intensity, magnetic, see ditto.
Ionic school of philosophy, p. 53, 65, 74, 124, 176.
Jorullo, elevation of, p. 199, 210.
Isothermal, isodynamic, &c. see Lines.
Italic school, p. 70.
Justin, speculations of the ancients on the causes of volcanic eruptions, p. 231 ;
Note 234.
Karatz, p. 332 ; Note 170, 174, 201. Isobarometric lines, p. 309.
Kant, on the limits of physical explanations, p. 33. Earthquake at Lisbon, p. 197.
Keilhau, changes of relative level of sea and land on the coast of Spitsbergen, 287.
Kendal, aurora, p. 185.
Kepler, p. 86, on the multitude of comets, p. 91. On extraordinary obscurations
of the sun's disk, p. 122, 123. On the relative distance of stars of different
magnitudes, Note 35. On the volumes and densities of planets, Note 38.
On aerolites, Note 59. On radiation of heat from fixed stars, Note 90.
KlOden, November aerolites, p. 114; Note 66.
Krug of Nidda, Geyser fountains, p. 209.
Krusenstern, on a large meteor having a tail of long continuance, Note 60.
Kuopbo, on the attraction of the magnet and of amber, p. 176 ; Note 162.
Kupffer, on isogeothennal lines, Note 201. Magnetic stations in Russia, Note 166.
Lamanon, letter to the Secretary of the Academic des Sciences in 17S7, respecting
the observations of Magnetic force in the voyage of La Perouse, Note 159.
Lambert, comparison of the direction of the wind with changes of atmospheric
pressure, temperature, and humidity, p. 310.
INDEX. CXXV11
Lament, mass of Uranus, p. 84. Satellites of Saturn, p. 87.
Land, general view of the dry, p. 278—294 ; Notes 335—361. Its superficial extent
compared with that of the ocean, p. 279, 280 ; Note 335. Its distribution and
configuration, and the influence of these on climate and human affairs, p. 279,
280, 283, 285, 286, 291, 292, 315—319, 322, 323 ; Notes 342—344. Elevation and
subsidence of, occasioned by different causes and forces, p. 286—290; Notes
348- 355. Height of the center of gravity of the, above the level of the ocean
in different parts of the globe, p. 293 ; Note 360.
Language, its reaction on thought, p. 41. The German extolled, p. 41.
Languages, p. 354, 355 ; Notes 441, 443.
Lap'ace, Systeme du Monde, p. 31. On the mass of comets, p. 100. Ellipticity
of the earth inferred from the lunar inequalities, p. 157, 158 ; Note 130. In-
ferior density of the ocean requisite for its stable equilibrium, p. 298. Theory
of tides, p. 299. On the difference between the attraction of masses and mole-
cular attraction, Note 22. On the zodiacal light, Note 35. On the hypothesis
of the lunar origin of aerolites, Note 69. On the laws which determine the
extreme limit of the atmosphere of a rotating cosmical body, p. 130 ; Note 94.
On the unchanged length of the day and temperature of the earth from the
time of Hipparchus, p. 166; Note 140.
Laugier, calculations shewing the identity of Halley's comet with the comet of
1378 mentioned in Chinese tables, p. 102 ; Notes 42, 56.
Lava, chemical composition, p. 224; Note 222.
Lawrence (Saint), fiery tears of, or August meteorodes, 114; Note 71.
Lefroy (Captain), determination of the focus of greatest magnetic intensity in the
northern hemisphere. Note 158 (Editor).
Lehman, on the tails of comets, Note 47.
Leibnitz, supposed relation between the volume of planets and their distance
from the sun, Note 38. »
Lenz, on differences in the saline contents of different ocean zones, p. 297.
Leonhard (Karl von), hypothesis respecting the origin of granular limestone found
in fissures in certain localities, p. 252 ; Note 281.
Lewy, observations on the quantity of oxygen in the atmosphere at different
seasons, p. 305 ; Note 377.
Lexell, see Comets.
Liebig, ammoniacal vapours in the atmosphere supplying azote to plants, p. 305;
Note 376.
Light, of comets, p. 97, 98. Of fixed stars (as Capella), p. 97. Independent, of
Venus, p. 97. Terrestrial, p. 188, 189. Polarisation and chromatic polarisa-
tion of, p. 37, 97. Of certain nights, p. 133 ; Notes 99, 100. Successive
propagation of, p. 143—145; Note 121. See Aurora, Zodiacal Light, and
Phosphorescence of the Sea.
Lignite, p. 273.
Limits of physical science, p. 32, 33. Of the solar atmosphere, p. 130.
Line of no magnetic dip or magnetic equator, p. 172—174; Notes 155—157. Of
least magnetic intensity, Editor's addition to Note 158. Of no horary varia-
tion of the declination, p. 1 72. Snow, or lower limit of perpetual snow, p. 326
—330.; Notes 5, 403.
Lines of equal magnetic intensity (or isodynamic), of equal magnetic inclination
(or isoclinal), and of equal magnetic declination (or isogonic), p. 170—175.
Isodynamic, p. 170, 174, 175; Notes 158—160. Isoclinal, p. 170, 172—174;
Notes 154-156. Isogonic, p. 170, 171 ; Notes 150-152. Isobarometric, p.
cxxviii INDEX.
309. Isothermal, isotheral, and isochimenal, p. 312—326 Iso^eothermal,
p. 208; Note 201.
Littrow, Beschreibende Astronomic, Notes 37, 55.
Lord, on the snow-line on the two declivities of the Himalaya, Note 5.
Lottin, on auroras, p. 185, 187, ; Note 172.
Lowenorn, discerned the corruscations of an aurora during bright sunshine, p. 182.
Lyell, successive variations of the general types of organic life, p. '264. Hypogene
rocks, Note 241. Uniformity of inetamorphic action in different parts of the
world, Note 259.
Lygian " field of stones," Note 61.
Mackenzie, description of a great volcanic eruption in Iceland, p. 226.
Maclear, parallax and distance of a Centauri, p. 144; Note 34. Increased
brightness of i) Argus, p. 144 ; Note 120.
Madler, compression of Uranus, p. 87. Distance of the innermost satellite of
Saturn from that planet, p. 89. Mass of the moon, p. 87 ; Note 40. Libration
of the moon, p. 90; Note 41. The three cold days of May (llth, 12th, 13th),
Note 86. Conjectures respecting the average mass of the double stars, p. 138 ;
Note 108.
Magellanic clouds, p. 76 ; Note 33.
Magnetism, terrestrial, p. 167—180 ; Notes 141—170. Electro- and thermo-, p. 167,
175-178; Notes 142, 163, 164, 167, 170.
Magnetic attraction, p. 176 ; Note 162. Declination, p. 170— 172; Notes 150-153.
Movement of closed systems of, Note ]52. Horary variations of, p. 171, 172 ;
Note 153. Equator, p. 172—174; Notes 155-157. Inclination, p. 172-174;
Notes 154—157. Intensity, p. 174, 175 ; Notes 158—160. Lines, (see Lines).
Stations or observatories, p. 24, 178, 311 ; Note 166. Storms or disturbances,
p. 24, 167; Note 143— their connection with aurora, 179—187; Notes 169, 170, 172.
Magnussen (Soemund), volcanic eruption in Scotland, p. 226.
Mahlmann, prevailing direction of the wind in the middle latitudes of the tempe-
rate zone in both continents, p. 312.
Mairan, described a jet of sparks in the zodiacal light, p. 131. Zodiacal light,
Notes 91, 92, 95.
Malle (Dureau de la), noticed a remarkable passage of St. Fatricius on tin
origin of thermal springs, Note 209.
Man, p. 350—357 ; Notes 433-443.
Marbles, Parian and Carrara, p. 251 ; Notes 278—280.
Margarita Philosophica of Gregorius Reisch, p. 44 ; Note 19.
Marius (Simon), first described the nebulae in Andromeda, p. 129.
Mars, see Planets.
Martins, found the air on the Faulhorn to contain as much oxygen as the air at
Paris, p. 306. On polar bands of cloud, Note 174. On the distribution of the
annual fall of rain in the different seasons of the year, Note 405.
Maskelyne, Hutton, and Playfair, experiments on the deflection of the plumb-line
by the attraction of SchehalHen, Note 138.
Matthieu, on the increased intensity of gravitation in volcanic islands shewn by
pendulum experiments, Note 132.
Matthiessen, letter to M. Arago on development of light and heat by electric
tension in finely divided matter of very small mass in proportion to its surface,
Note 98.
Mayer (Tobias), on the proper motion of the solar system, Notes 102, 105.
INDEX. CXX1X
Maximilian (Prinz, zu Wied), on the American race, Note 434.
Mean numerical values, their importance in modern physical science, p. W.
Mean state of phenomena, p. 17, 18.
Melloni, on radiant heat and electro-magnetism, p. 32.
Menzel, first use of the term "geography of plants" in an unedited flora of Japan,
p. 347.
Messier's, comet, p. 101, see Comets. Nebula, nearly resembling our own
sidereal system, p. 141.
Metamorphic, see Rocks.
Meteors, meteoric stones, &c. see Aerolites.
Meteorology, p. 304—338 ; Notes 375 -419. Editor's note on, addition to Note 382.
Meteorological observations, see Magnetical observatories (or stations).
Methone, elevation of the hill of, p. 230.
Meyen on the reproductive organs of liverworts and algae, p. 340. On a thermic
scale of cultivation, p. 321 ; Note 395.
Meyer (Hermann von), on Saurians and flying saurians, Notes 303, 305.
Milky way, p. 80, 96, 140—142 ; Notes 109, 110, 113. Nebulous, p. 141.
Minerals, artificial formation of, p. 257 ; Notes 292—294.
Mines, depth of several, Note 124. Temperature of, Note 138. Earthquake
movements in, Note 189.
Mitchell, earthquake movements or tremblings of the ground in North America,
Note 188.
Mitscherlich, on the influence of temperature on the axes of crystals, p. 248 ;
Notes 263, 266. On the melting point of granite, Note 13. On the chemical
origin of specular iron in volcanic masses, Note 222. Light thrown on geology
by chemical combinations, p. 245 ; Note 25S. On the artificial production of
minerals, Notes 292, 294.
Monsoons, p. 311 ; Note 389.
Moon, p. 87,88, 90, 91 ; Notes 40, 41.
Monticelli, on hydrochloric acid exhalations in an eruption of Vesuvius, Note 196.
On crystals of mica in the lava of Vesuvius, Note 270.
Morton (Samuel George), his fine work on the American race, Note 434.
Moser's, pictures, p. 189.
Mountains, the elevation, scenery and vegetation of different, and chains of, in
America, Asia, and Europe, p. 9-14; Notes 2—6, see Cordilleras, and Hima-
laya. Influence of, on climate, natural productions, and human affairs,
p. 152, 291, 292, 324. Elie de Beaumont's views on the relative age of different
chains of, p. 34, 291—294 ; Note 361. Decrease of temperature and cor-
responding zones of vegetation on the declivities of, p. 11 — 13, 324—327, 346 ;
Notes 5, 6, 399, 429. Limit of perpetual snow on, or snow-line, p. 326—330;
Notes 5, 403.
Mud volcanoes, see Volcanoes and Salses.
Aliiller (Johannes), on races of plants, animals, and men, p. 352 ; Note 438.
Muncke, on the prevalence of auroras in particular districts or zones of longitude,
p. 184 ; Note 176.
Mundus, origin and derivation of the term, p. 57.
Murchison, period of the Paleosaurus and Thecodontosaurus, p. 263. Description
of a fissure through which melaphyre has been ejected in a co;,i mine, Note
260. His general classification of the older fossiliferous rocks, Note 314.
Muschenbrock, in the middle of the last century, called attention to the frequency
of meteors in August, p. 115 ; Note 73.
Nature, import of the term, p. 22, 69, 71. Systems of, p. 30. Philosophy of nature,
CXXX INDEX.
or ancient doctrine of the Cosmos, p. 5, 15. Order, unity, beauty, and harmony
of, p. 5—8, 20, 21. Pliny's History of, p. 59.
Nebulae, p. 74—77, 141—143 ; Notes 32, 112.
Nebulous milky way, p. 141, 142 ; Note 113.
Nebulous stars and planetary nebulae, p. 75, 76, 130, 143 ; Notes 31, 95.
Nebulous matter, supposed origin of the heavenly bodies from, by condensation,
p. 73—75, 85, 86, 90.
Newton, raised the question of the difference between the attraction of masses and
molecular attraction, p. 50 ; Note 22. Approved strongly of Varenius's Gene-
ral arid Comparative Geography, p. 54 ; Note 25. Considered that the other
planetary bodies of the solar system are probably " composed of the same
matter with this earth : viz. earth, water, and stones, but variously concocted,"
p. 122 ; Note 85. Assigned 7^75- as the compression of the earth on the hypo-
thesis of homogeniety, p. 155, 156 ; Note 129.
Newtonian axiom, of the identity of the force of gravitation in the most various
bodies, confirmed by pendulum experiments, especially those of Bessel, p. 52.
Nicholson, description of lightning clouds without audible thunder, p. 335.
Nilsson, depression of the south coast of Sweden, p. 287.
Nobile (Antonio), experimental investigations on the influence of the height of the
barometer on the level of the sea, p. 290.
Noggerath, counted 792 annual rings in a trunk found in lignite or brown coal,
p. 273.
Nomenclature, scientific, and changes in it proposed at different periods, p. 44, 45.
Nordmann, on certain minute animals in the eyes and gills of fishes, p. 344.
Norman (Robert), invented the inclinatorium, or dipping needle, in the sixteenth
century, Note 144.
Numbers, power of, in science, p. 70, see Mean numerical values.
Ocean (general account of), p. 279, 294—304 ; Notes 362—374. Its extent relatively
to that of the dry land, p. 279, 280 ; Notes 335, 336. Its depth, p. 150, 294.
Decrease of temperature at increasing depths, p. 295, 296. Its general uni-
formity and constancy of temperature, p. 296 ; Notes 363, 364. Immense
abundance of animal life, p. 303, 341, 342. Influence on climate, p. 296,
815—321, 323 ; Notes 389. On human affairs, p. 153, 283, 286, 304. Tides,
p. 298, 299 ; Note 367. Currents, p. 299—302 ; Notes 368-373, and Editor's
addition to 373. Phosphorescent light, p. 189, 303. Impression produced by
its contemplation, p. 303, 304.
Oersted, connection of magnetism with electricity, p. 175, 176; Note 166.
Olbers on comets, p. 96, 102 ; Note 49. Explanation of a supposed occasional
upward movement of aerolites, p. 114; Note 65. Periodicity of the August
meteors, p. 115. Expected return of an exceedingly brilliant display of
November aerolites in 1867, p. 117 ; Note 75. Supposed retardation of Novem-
ber aerolites, Note 66. On the variations in the intensity of the Zodiacal
light and vibrations in the tails of comets, p. 132 ; Note 99. On the light of
stars and the transparency of celestial space, p. 142 ; Note 116. Mean num-
ber of aerolites visible per hour, Note 60. Velocity of aerolites computed on
the hypothesis entertained by Laplace of a lunar origin, Note 69. Remark
that no fossil meteoric stones or aerolites have yet been found in secondary
and tertiary formations, Note 83.
Olmsted (Denison), of Newhaven, Massachusetts, on the great fall of November
aerolites in North America in 1833, p. Ill, 114, 116 ; Note 66. Small and very
numerous aerolites resemblin phosphorescent lines," p. 107; Note 59.
INDEX. CXXxi
Conjectured connection of aerolites with the passage of the earth through the
zodiacal nebulous ring, Note 96.
Oltmanns, observed, with the Author, the march of the declination needle at short
intervals at Berlin, Note 166.
Organic life, general view, p. 338—357 ; Notes 420—432.
Ovid, description of the volcanic elevation of the hill of Methone, p. 230 ; Note 230.
Oviedo calls the gulf weed "praderias de yerva," p. 301.1
Owen, on the great fossil Myl6don, p. 267. On the Dinornis, p. 378.
Palaeogeography, p. 274—278.
Palaeontology, p. 28, 259-268 ; Notes 297—316.
Palaeophytology, p. 28, 268—274 ; Notes 317—332.
Palaeozoology. (See Palaeontology.)
Palmer, observed the great November shower of aerolites in North America, in
1833, p. 114. Recalled the occurrence of a similar phenomenon in November
1799, p. 115.
Paramos, p. 13, 327, 332.
Parallax, of fixed stars, p. 79, 144; Note 34.
Parry, auroras, and their association with magnetic disturbances, p. 185—187.
Barometic observations at Port Bowen, p. 309. Rare occurrence of thunder
in high northern latitudes, p. 336. Saw an aurora in clear daylight, Note 173.
Patricius (Bishop of Pertusa in the third century), his correct views respecting
the origin of hot springs, p. 211 ; Note 209
Peltier, on different sources of atmospheric electricity, p. 333 ; Notes 409, 412,
415. Attributes to slate-grey clouds resinous electricity ; and to white, rose,
and orange-coloured clouds, vitreous electricity, p. 334.
Pencati (Count Marsari), calcareous beds partially inflected by the contact of
syenitic granite in the Tyrol, p. 250.
Pendulum experiments, p. 26, 157—160; Notes 131—136. Made for the purpose
of determining the ellipticity or figure of the earth, p. 156, 157 ; Note 131.
Influence of local attraction on, affording indications respecting rocks and
strata otherwise inaccessible, p. 26, 158; Notes 132, 133, and Editor's Note
appended to Note 132. Those of Bessel, establish the identity of the action of
gravitation on very various bodies, including fragments of aerolites, p. 51, 52.
Pentland, elevation of the Sorata and Illimani, Note 2. Skulls from the highlands
ofTitiaca, Note 434.
Permian system, Note 314.
La Perouse, first experiments on the variations of the magnetic force made on his
expedition, Note 159.
Pertz, notice of a large meteoric stone or aerolite, p. 109 ; Note 62.
Peters (Dr.), on the velocity with which stones are ejected from Etna, Note 69.
Phillips, experiments on the temperature of mines at depths, Note 138.
Philosophy, abuse of speculative, p. 63—66. " Philosophy of nature," p. 5, 15.
Pythagorean, p. 52, 53, 56, 57, 70. Ionic, p. 53, 65, 74, 124, 176.
Phosphorescence of the sea, p. 189, 303. Of Venus, p. 188.
Physical science, its limits, p. 33. Its intellectual value and its influence on the
prosperity of nations, p. 36—39.
description of the universe (cosmography), p. xix. and p. 40, 41.
Pindar, oldest recorded eruption of Etna, Note 213.
Plana, influence of local gravitation on the direction of the plumb-line (and that
on determinations of latitude) in Lombardy, Note 133.
cxxxri INDEX-
Planets, general account, p. 81—87; Notes 37—39. Astrea, Editor's Preface,
p. viii. Ceres, p. 82, 84. Earth, 82—90. Juno. p. 82, 84. Jupiter, p. 82—89,
Mars, 82—87, 122. Mercury, p. 82—86. Pallas, 82—85. Saturn, 82—89.
Venus, p. 82—86. (Her independent or phosphorescent light, p. 97, 188.)
Vesta, p. 82—85. Uranus, 82—85, 86—90 ; Note 39. Closely connected orbits
of the small planets, with the exception of Pallas, p. 116.
Plato ascribed thermal springs and all volcanic phenomena to the Pyriphlegethon
or subterranean fire, p. 227 ; Note 225.
Playfair, on the Schehallien experiments, Note 136. On the rise of the mainland
in Sweden, Note 350.
Pliny (the elder), his physical description of the world, p. 59. On the smallness
of the earth relatively to the universe, p. 155 ; Note 128. On the attraction
of amber when rubbed, and of the loadstone, p. 176 ; Note 161. Remarked
the peculiar burnt appearance of the crust of aerolites, Note 80. Aware that
magnetism can be imparted permanently to iron, Note 149. On the stone of
./Egos Potamos, Note 69. Remarks on earthquakes, Notes 183 and 184. De-
scribed flames fed by emissions of inflammable gas, as the Lycian Chimera,
p- 210 ; Note 207. Remarks on jasper, Note 274. On the uniudented form of
the continent of Africa, Note 344.
(the younger), volcanic ashes, and description of the great eruption of
Vesuvius, p. 225.
Plutarch, truly conjectured aerolites to be celestial bodies, p. 123. Supposed
relation between the depth of the sea and the heights of mountains, Note 360.
Poisson, on the identity of the mass of the planet Jupiter, as determined from its
influence on his own satellites, on Encke's cornet, and on the small planets,
p. 52 ; Note 23. Surmises the possibility of aerolites igniting far beyond the
range of our atmosphere, p. 110 ; Note 63. Hypothesis to explain the occa-
sional non-appearance of August and November aerolites, p. 118; Note 78.
Hypothesis respecting the temperature of the globe and the degree of warmth
observed in mines arid Artesian wells, p. 166, 167 ; Note 137. First suggested
the measurement of the magnetic force in parts of an absolute scale, since
accomplished and brought into use by Gauss, Note 158 (Editor).
Polarisation, chromatic, of light, p. 37, 97 ; Notes 16 and 51. (See "chromatic"
and « light.")
Polybius and Eratosthenes, on the pyramidal form of the Iberian, Italic, and
Hellenic peninsulas, p. 283.
Pons, comet, p. 102.
Posidonius, description of the " Lygian field of stones" at the mouih of the
Rhone, Note 61.
Pouillet, ascribes atmospheric electricity to the growth of plants, p. 333 ; Note 410.
Prevost, ephemeral apparition of the igneous island of Ferdinandea, p. 231 ;
Note 233.
Prichard on the dark-coloured African nations, p. 351, 352 ; Note 436. Divides
mankind into seven races, p. 353 ; Note 439.
Pyramidal form of the southern terminations of great masses of land, p. 30, 282,
283 ; Note 344.
Pyriphlegethon, p. 227 ; Note 225.
Pythagoras, and Pythagorean philosophy, p. 56, 57 ; Note 27.
Quarterly Review, article on magnetism, by Sir John Herschel, p. 178; Note I6b.
Quenstedt, on the lower limit of belemnites, p. 266; Note 312.
Quetelet, with Olbers and Benzenberg, first made known the periodicity of the
INDEX. cxxxiii
August meteors, p. 115. On the mean number of aerolites, per hour, within
the range of vision of one individual, Note 60.
Quotations from Arago, Notes 51, 72, 364. Aristotle, p. 136, 230. St. Augustine,
Note 426. Bacon, p. 37. Beaumont (Elie de), Note 272. Bembo (Cardinal),
Notes 21 6, 234. Burke, p. 20. Burnes (Sir Alexander), Note 60. Carus, p. 22 ;
Note 11. Cassini (Dominic), Note 96. Childrey, Note 91. Columbus, Notes
329, 374. Gilbert (William), Note 141. Goethe, p. 29, 37. Herschel (Sir John),
translation of part of Schiller's Walk, Note 9. Description of the two Magel-
lanic clouds, Note 32. Herschel (Sir Wm.), p. 142, 143, Note 121. Humboldt
(Alex, von), Notes 394, 420. Humboldt (Wilhelm von), p. 145, 356, 357 ; Note
443. Kepler, p. 91 ; Notes 34, 54, 59, 90. Jacquemont (Victor), Notes 5, 231,
426. Justin, Notes 234, 426. Laplace, Notes 35, 69. Newton, Note 85.
Gibers, Notes 83, 99. Ovid, p. 230 ; Note 230. Plato, Note 225. Pliny, Notes
48, 09, 149, 183, 184, 344. Poisson, Notes 63, 78. Rennell, Note 370. Saint-
Pierre (Bernardin de), p. 7. Schiller, p. 15 ; Note 9. Seneca, Notes 48, 228.
Solinus, Note 210. Tacitus, N. 433. Terzago, Note 69.
Rain, p. 331, 332. Mean quantity at different places, Notes 405, 406.
Reich, determination of the mean density of the earth by experiments with a
balance of torsion, p. 160 ; Note 136. On temperatures at depths in the mines
of Saxony, Note 138.
Reinwardt and Hoffman, on volcanoes, which, during violent eruptions of scoriee,
hot water, and other substances, do not emit lavas, Notes 218, 240.
Reisch (Gregorius), his Encyclopaedia, written in the 15th century, entitled,
Margarita Philosophies, p. 44; Note 19.
Remusat (Abel), on the existence of active volcanoes in central Asia at a great
distance from the ocean, p. 232 ; Note 236. Notice of a supposed very larga
aerolite near the sources of the Yellow River, Note 62.
Rennell (Major), on the equatorial current in the Caribbean Sea, Note 370. Clas-
sification of currents into drift and stream currents, Note 373 (Editor).
Richard, on Cycadeae and Coniferae, Note 329.
Richardson, on the connection of aurora with cirro-stratus, p. 182, 183. On the
noise supposed to be occasioned by the aurora, p. 185, 186.
Richer, pendulum experiments, Note 25.
Ritter (Carl), praise of his great work, entitled, Geography in relation to Nature
and to the History of Men, or General Comparative Geography, p. 18, 30, 54.
Rive (De la), on the increase of temperature at depths, Note 138. On the unequal
distribution of heat in the atmospheric strata as a cause of atmospheric elec-
tricity, p. 333; Note 411.
Robert (Eugene), ancient sea line marked at a high level on the coast of Spitz-
bergen, p. 287.
Robertson, on the permanency of the magnetic declination in Jamaica since 1660,
Note 150.
Rocks, fundamental classification of, p. 235—238. Endogenous or erupted, p.
238—241, 246—248; Notes 247— 257, 260, 261. Exogenous or sedimentary,
241—244. Metamorphic, p. 244— 257 ; Notes 258— 295. Conglomerates formed
of detritus, p. 257, 258. General chemical constituents of, p. 258, 259.
Classification of fossiliferous, p. 267.
Rose (Gustav), on the texture, composition, and appearance of different aerolites,
p. 121. Investigations on the structure of volcanic rocks, p. 225. On some
remarkable masses of granite, p. 239; Notes 249, 251, 252, 260. On crystals
CXXX1V INDEX.
contained in granite, Note 249. On the effects produced on certain argilla-
ceous schists by the contact of granite, p. 249. On different minerals and
their mode of formation, composition, &c. Notes 257, 258, 262, 268, 294.
Ross (Captain Sir James Clark), soundings with 4600 fathoms of line, p. 150.
New forms of microscopic animals from the Antarctic Polar Seas, p. 341
Magnetic observations near the centre of the highest isodynamic oval, Notes
158 (Editor) and 160. Determination of the lines of equal declination, equal
inclination, and equal intensity, over three-fourths of the accessible portion
of the high southern latitudes, Note 166 (Editor).
Rossel (Admiral), observations of magnetic intensity. Their bearing and date of
publication discussed, Note 159.
Rothmann, first recorded notice of the zodiacal light, mistaking it, however, for
a phenomenon of twilight, Note 99.
Royle (Forbes), snow-line on the two declivities of the Himalaya, Note 403.
Rozier, observed a steady luminous appearance in clouds, p. 188.
Rumker, Encke's comet seen with the naked eye in New Holland in 1822, p. 98.
Ruppell contradicts the existence of active volcanoes in Kordofan, Note 237.
Russegger (and Berton), barometric measurements shewing a great depression of
the Dead Sea and the valley of the Jordan below the level of the Mediterranean,
Note 124, 353.
Sabine (Edward), on the western movement of the intersection of the line of no
dip with the geographical equator in the Atlantic from 1825 to 1837, p. 173 ;
Note 156. On the particular importance of the isodynamic lines to the theory
of terrestrial magnetism, p. 174; Note 158. On the variations of the mag-
netic intensity over the surface of the globe, p. 174, 175. On the highest
intensity on the globe, Note 160. Magnetic intensity at Melville Island near
the magnetic pole compared with New York, p. 175. Determination of ellip-
ticity by pendulum experiments, Note 131. Increased intensity of gravitation
in volcanic islands, Note 132 (Editor's addition). Magnetic disturbances,
Note 143. Observes the current of the river Amazon 300 miles from the
mouth of the river, Note 373 (Editor's addition). Diurnal variation of the
pressure of the dry air at Bombay, Note 382 (Editor's addition). See Editor.
Sagra (Ramon de la), mean annual quantity of rain at the Havannah, p. 331.
Salses, or mud volcanoes, p. 211—213.
Santorin, island of, affords " a type of islands of elevation," p. 230 ; Note 231.
Sargasso Sea, or portion of the ocean covered with the gulf weed, p. 301.
Satellites, revolving round the primary planets of the solar system, general ac-
count, p. 86—90. Of the Earth, see Moon. Of Jupiter, p. 87—89. Of
Saturn, p. 87—90, 116. Of Uranus, p. 20, 87—90.
Saturn, see Planets.
Saussure, measurements of the crater of Vesuvius, p. 221 ; Note 219. Found
traces of ammoniacal vapours in the atmosphere, p. 305. On glaciers, p. 328.
Hygrometric observations at heights, p. 332. Diurnal variation of atmo-
spheric electricity, 334.
Bchayer, microscopic animals in ocean water, p. 342.
Schelling, quotation from his Giordano Bruno, p. 65 ; Note 30.
Scheuchzer's fossil salamander once supposed to be a human skeleton, p. 263.
Schiller, quotation from, p. 15; Note 9.
Schleiden, on the germs of organisation and development of vegetable cells, p.
349 ; Notes 431, 432.
INDEX. CXXXV
Schnurrer attributed some remarkable obscurations of the solar light to the pas-
sage of aerolites, p. 123.
Schouten (Cornelius) observed the magnetic declination in 1616 in the Pacific
Ocean, Note 152.
Schouw, on the fall of rain in the different seasons of the year, Note 405.
Schreibers, fragmentary character of aerolites, p. 110.
Schwann, on organic development. Note 431.
Scina (Abbate), earthquakes unconnected with previous meteorological circum-
stances, Note 184.
Scoresby, rare occurrence of thunder in the high northern latitudes, p. 336.
Sea, see Ocean.
Sefstrom, on crystals of olivine found in the scoriae of artificial works, Note 293.
Seneca, remarked the usual direction of the tails of comets in reference to the
sun, Note 45. Aware of the cosmical nature and long orbits of comets,
Note 48. Remarked that stars are seen through the tails of comets, Note 49.
On the supposed ominous character of comets, Note 57. Speculations on the
causes of earthquakes, Note 184. Inclined to believe that Etna was becoming
extinct, p. 215 ; Note 214. On volcanic action and on the supposed lowering
of Etna, p. 229 ; Note 228.
Shoals, their presence indicated by a diminished temperature of the sea, by mists,
and by clouds, p. 302.
Sidereal systems, p. 79—81, 141 ; Notes 34, 112.
Siljerstrom, on the height of auroras, p. 181 ; Note 172.
Sirowatskoi's discovery of the Wood-hills in New Siberia, Note 327.
Snow, limit of perpetual, p. 10, 11, 326—330; Notes 5, 400—403. Forms of
organic life in polar and mountain snows, p. 344. Red snow, 344.
Social plants, p. 6, 345, 346.
Solar system, general account of, p. 81— 134; Notes 35— 100. Its place in space
inferred from a kind of stellar scale, p. 80. Its proper motion, or movement
of translation, p. 134, 135, 138;. Notes 101—105.
Solinus, on mud volcanoes, or " fluid earth issuing from the earth," Note 210.
Somerville (Mrs.), on the comparative volumes of the small planets and the largest
aerolites, Note 62. On the volume and the light of planetary nebulae, Note
95.
Sommering, on the fossil remains of the larger vertebrated animals, p. 261.
Springs, cold and hot, general account of, p. 207—211 ; Notes 202—209. Causes
which influence the temperature of ordinary cold, p. 207, 208 ; Note 202, 203.
Deepest Artesian wells the warmest, p. 21 1 . Constancy to the same spot,
p. 210; Note 206. Formed from volcanic steam, p. 225. Thermal, p. 208—
211 ; Notes 205, 206, 209. Connection with earthquakes and volcanic phaeno-
mena, p. 197, 210. Beds of travertin deposited from cold and warm, p. 237c,
Stars, (fixed stars) p. 77—81, 134—145. Nebulous, p. 75, 76, 130, 143. Telescopi.
p. 143. Vast multitude in the Milky Way, p. 140. Double and multiple,
p. 20, 136—138. Parallax and distance, p. 137, 138, 144 ; Notes 34, 106. Ap-
parent diameter and computed volume and mass, p. 137, 138. Proper motions,
p. 134—140. Successive propagation of the light of, p. 143—145; Note 121.
Appearance of new, and changes of brightness of previously known, p. 144,
145; Note 120.
Sternberg (Count), fossil cycadeae in an old carboniferous formation, Note 320.
Strabo, conjectured an unknown land to exist between Iberia and Thinae, in the
46th parallel of latitude, p. 281 Extolled the varied configuration of Europe
CXXXV1 INDEX.
as favourable to civilisation, p. 283. Cessation of earthquake movements on
the issue of a stream of lava, p. 203 ; Note 193. Distinguished between islands
adjacent to and severed from the main land, and islands distant from the
shore and raised from the bottom of the sea, Note 212. " Burning mud of the
Lelantine plains" and other volcanic phenomena and hypotheses relating to
them, Notes 225, 228, 230, 234.
Struve, parallax of stars, p. 144. Local disturbances of gravitation in level parts
of Europe, Note 133.
Sun, his revolution round the centre of gravity of the whole solar system, p. 134.
Movement of translation in space, p. 134, 135 ; Notes 101, 102. His mass and
volume compared to those of other fixed stars, p. 137, 138. Limits of the at-
mosphere of the, considered in reference to the zodiacal light, and in com-
parison with nebulous stars, p. 130, 131 ; note 95. Views of Anaxagoras and
others respecting the, note 69.
Symond (Lieut.), depression of the Dead Sea below the level of the Mediterranean
determined by trigonometrical measurements, Note 353.
Tacitus, distinguishes the influence of climate from that of race, note 433.
Temperature, early high, mean, and internal temp, of the globe, see Earth.
Local causes which raise or depress, p. 315, 316, and 316 — 324 ; Notes 390, 391,
and 393 — 398. Of several places on the globe, both annual and at different
seasons, p. 317—320, 322, 325—327 ; and Note 396. Decrease of, with increasing
elevation, p. 11, 324, 326, 327 ; Notes 6, 399. Increase of, with increasing
depth (in the earth), p. 162, 163; Notes 137, 138. General decrease of, with
increasing depth in the ocean, p. 295, 296. General uniformity and constancy
of, in the same part of the surface of the ocean, p. 296 ; Notes 363, 364. Zones
of greatest oceanic temp., p. 296, 297. Great modifications of, by currents,
p. 301 ; by shoals, p. 302. Depth to which the periodical variations of temp
descend in the earth, p. 164, 165 ; Note 139. See Thermic scale, Isothermal
Isotheral, and Isochimenal lines.
Theodectes (an ancient tragic poet), on the black colour and curled hair of th
Ethiopians, p. 352.
Theophylactus, speaks of Scythia as free from earthquakes, p. 191 ; Note 181.
Thermal springs, see Springs.
Thermic scale, of different kinds of cultivation, p. 321 ; Note 395.
Thermometer, see Temperature.
Thienemann, on cirrous clouds as the substratum of the Aurora, p. 182 ; Note
173. Absence of audible sound in Auroras, p. 185.
Tides of the ocean, p. 298, 299.
Tiedemann, on the brain of Negroes and Europeans, p. 351.
Tillard (Capt.), temporary appearance of the Island of Sabrina, p. 230.
Tournefort, zones of vegetation on Mount Ararat, and first notice of the similar
influence of increasing elevation and increasing latitude on vegetation,
p. 346, 347.
Tralles, on the negative electricity developed in the neighbourhood of lofty cas-
cades, Note 41 5.
Trogus Pompeius, his views respecting volcanic phenomena and the supposed
necessity of their vicinity to the sea, p. 231 ; Note 234.
Tropical regions, advantages presented by them towards a scientific knowledge
of the regularity of natural laws, p. 11, 12, 338.
Truenos of (Juanaxuato, p. 196. See Bramidos.
INDEX. cxxxvii
Urville (D'), on the geographical distribution of ferns, Note 319.
Valenciennes, fossil mammalia allied to marsupial animals, p. 265.
Valz, change of magnitude in the nucleus of a comet at its aphelion and perihelion,
p. 98.
Varenius (Bernhard), his general and comparative geography, and its approval by
Newton, p. 54 ; Note 25.
Vegetation, zones of, on the declivities of mountains, p. 12, 13, 343, 344, 346 ;
Notes 5, 6, 429. See also Mountains, Himalaya, Cordilleras. Distribution of,
over the surface of the earth, or the geography of plants, p. 10, 11, 47 — 49,
342, 343, 345—349 ; Notes 3, 420, 427—429. Germs of vegetation, cells, inter-
nal movements, &c. p. 340, 349; Notes 431, 432. Fossil, see Palseophytology.
Venetz, glaciers, p. 328.
Venus, see Planets, p. 82 — 86. Her independent or phosphoric light, p. 97, 188.
Vico, satellites of Saturn, p. 87.
Vigne, snow-line on the two declivities of the Himalaya, Note 403.
Vine, influence of climate on its successful cultivation, p. 319, 321, 322; Note 396.
See Wine.
Volcanoes and volcanic phenomena generally, p. 9, 10, 13, 14, 146, 147, 151, 152,
189, 201—203, 213—235; And in the most general sense, 189—235; Notes
213—241. Mud, p. 211—213. Volcancitos, p. 213 ; Note 210. See also Ther-
mal springs. Effects of volcanic action shewn on the surface of the earth
and the moon, p. 27, 216.
Volcanic ashes, p. 225. Steam, p. 222, 223, 225. Storms, 223.
Voltaic pile, p. 32, 36.
Vrolik, anatomical researches, p. 351.
Wagner (Rudolph) on race, p. 351 ; Note 435—438.
Wallich, his Flora Indica, Note 3.
Walter, volcanic phenomena, Note 193.
Wartmann, on the different number of shooting stars observed at the same time
at two places very near each other, Note 60.
Webb, measurements of elevation and snow-line in the Himalaya, Notes 5, 403.
Weber, anatomical researches, p. 351.
Wentzel (Dr.), attributes sounds heard dunng aurora to other natural causes,
p. 186.
Winds, p. 311, 312. Trade, p. 317. See Monsoons.
Wine, influence of climate on its successful production and quality, p. 321, 322;
Note 396.
Witham, first recognised the existence of couiferse in the vegetation of the* carbo-
niferous period, Note 322.
Wollaston, assumption respecting the limits of the atmosphere, p. 294.
Wrangel, coincidence between the fall of aerolites and the brightening of auroras,
p. 116 ; Note 75. Connection of aurora with cirro-stratus, p. 183; Note 173.
With particular districts, p. 184. Absence of audible sounds connected with
aurora, and those sometimes heard attributed to other natural causes, p. 185,
186. Wood-hills of New Siberia, Note 327.
Xenophanes, comets, p. 92. Marine fossils in the marble quarries of Syracuse
and Faros, p. 25U
CXXXV111
INDEX.
/iimmerman (Carl), hypsometric remarks on the elevation of the Himalaya, and
of the high plateaus and summits north of the chain, Note 5.
Zodiacal light, p. 76, 82, 127-133; Notes 91-99. Earliest notice of, p. 129;
Note 91. Apparent variations in its intensity, p. 131, 132. Picturesque de-
scription of, p. 127, 128.
Zones of latitude or elevation, as characterised by different vegetable forms
p. 48, 49, 346.
VOL. J.
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