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HILOSOPH1CAL INSTRUMENTS

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PIKE'S

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ILLUSTRATED

DESCRIPTIVE CATALOGUE

O F

OPTICAL, MATHEMATICAL,

AND

PHILOSOPHICAL INSTRUMENTS,

MANUFACTURED, IMPORTED, AND SOLD BY THE AUTHOR; WITH
THE PRICES AFFIXED AT WHICH THEY ARE OFFERED IN 185R.

WITH UPWARDS OF 750 ENGRAVINGS,

MOSTLY ORIGINAL DESIGNS FROM THE INSTRUMENTS OP HIS E3T A BM3HMENT
IN THE VARIOUS DEPARTMENTS OP

ELECTRICITY, MECHANICS,

GALVANISM, OPTICS,

MAGNETISM, ASTRONOMY,

ELECTRO-MAGNETISM, SURVEYING,

PNEUMATICS, NAVIGATION,

HYDROSTATICS, METEOROLOGY,
CHEMISTRY, &c., &c.

Designed to aid Professors of Colleges, Teachers, and otnera,

in the Selection and Use of Illustrative Apparatus.

in every Department of Science.

- BY BENJAMIN PIKE, JR., OPTICIAN.

I N T WO VOLUMES.

VOL. I.
SECOND EDITION, ENLARGED.

NEW YORK:
PUBLISHED AND SOLD BY THE AUTHOR,

AT HIS OPTICAL, MATHEMATICAL, AND PHILOSOPHICAL

INSTRUMENT MANUFACTORY,

294 BROADWAY,

A FEW DOORS ABOVE THE PARK.

1856.

ENTERED, according to Act of Congress, in the year ]848,

By BENJAMIN PIKE, JR.,

In the Clerk's Office of the District Court for the Southern District
of New York.

PREFACE.

BENJAMIN PIKE. Jr., in presenting to his friends
and the public the following Catalogue of Instruments,
desires to say, that he has been induced to undertake
the collection of materials for such a volume, from the
fact that no work corresponding to it is to be found,
and the information which it is intended to impart, can
only be gathered from a great variety of sources, many
of which are works not published in this country.
The rapid strides with Avhich the sciences are advanc-
ing, and the fact that the arts and manufactures are
calling in the aid of some of these instruments to
facilitate their processes, while others may be employed
in every day use, renders such a volume as this alto-
gether appropriate and useful, if, indeed, it be not abso-
lutely indispensable.

He wishes it borne in mind, that he is not a man
of letters, but a mechanic,— a practical workman : this
will account for whatever imperfections may be found
in style, arrangement, &c.

The instruments illustrated in our modern works on
natural philosophy are too frequently represented by
old and obsolete cuts, mere copies, book after book, for
many years back, furnishing but little idea of more
modern articles.

In presenting this volume, the first design has been
to illustrate by good drawings, and brief descriptions,
articles manufactured in his establishment, or imported

VI PREFACE.

by him, in order that those desirous of obtaining appa-
ratus, and not having an opportunity of personal
examination, may yet be able to judge of the style,
quality, and price. The usual brevity of the descrip-
tions has in a few instances been departed from, where
the instrument has demanded a more extended notice.

Particular pains have been taken, and a large ex-
pense incurred, in the illustrations (numbering over 750)
of this Catalogue ; they are mostly original, and drawn
from the most modern and approved instruments.

These articles embrace every variety kept in an
extensive Optical and Philosophical Instrument Store ;
and include almost every instrument used in natural
and experimental philosophy.

The author having devoted himself from early youth
to the manufacture of these instruments on a some-
what extensive scale, is satisfied that his collection of
instruments is not surpassed, if equalled, by any in the
country, for extent, style, quality, or cheapness; he
therefore solicits with confidence a continuance of that
encouragement which he has in past years received,
and which he is determined to merit.

Professors of the sciences will find in his establish-
ment a full assortment of instruments suitable for
illustration and practical purposes. To his stock have
been recently added many large and valuable instru-
ments, and it will be his endeavor to continue to keep
pace with the growing demand for good instruments
among the scientific community.

Parents and guardians of youth, who feel desirous
of promoting a taste for Chemistry and Natural Phi-
losophy in the minds of the young, from seeing what
rapid advances these sciences are making, and how
necessary their acquaintance to all, will find nothing

PREFACE. Vll

promote their wishes, nor their children's enjoyment,
more than procuring for them an assortment of appa-
ratus, whereby they may be able to follow up practi-
cally those experiments of which they have read in
text books of science, or have seen in lectures. The
moderate prices of some of these articles are enumera-
ted at the end of this volume.

In the construction of apparatus, it will be the
maker's aim to use the various pieces of apparatus to
the best advantage, by adapting them to the perform-
ance of as great a variety of purposes and experiments
as is possible.

The writer might enumerate to his patrons a num-
ber of diplomas and silver medals received for his
Air-Pumps, Galvanic Batteries, Magnetic Machines,
Barometers, Theodolites, Magic-Lanterns, Sliders, &c.,
at various Fairs of different Institutes ; and also the
commendatory letters of distinguished Professors in
various Colleges and Universities, who are using in-
struments of his manufacture ; but having been long
established in this business, he trusts that the charac-
ter of his instruments is understood, without further
reference.

He would beg leave to notice his improved Magnetic
Machines for medical purposes ; and though, unlike
many that have followed in his wake, he has not
trumpeted abroad the various cures the instrument has
accomplished, yet the remarkable cures it has and still
is effecting, are beyond question, although he has de-
clined to publish cases, from the fact that the most
remarkable are among some of the very first families
of this city, and elsewhere, to whom it would not be
agreeable to have an account of their infirmities seen
in print. Let it suffice to say, that this instrument arose

Vlll PREFACE.

to its high reputation, by no efforts of his own to give
it publicity, but solely by the cures it accomplished,
and which are now very generally known.

As every maker of these instruments claims to make
the best, and the last usually makes the loudest claim,
he would simply state that his instrument has been,
without solicitation, purchased and used by every Hos-
pital and Medical Institution in this city and vicinity,
and by almost every Physician, as well as by over one
thousand of our own citizens, and also by distinguished
persons in various parts of this country and in foreign
lands.

His stock of Telescopes and Microscopes will be
found very extensive, and together with Optical Lenses
and Sliders for the Magic Lantern, form the principal
articles that are imported ; and for obtaining these
from London and Paris direct, and at low rates, he is
possessed of unusual facilities.

As the Microscope is capable of affording a vast field
for amusement and instruction, opening a new world
and displaying the most extensive scenes of creative
power, wisdom, and design ; and it being difficult to
find in print any information concerning it, a minute
description of one of the kinds is given, which will be
found applicable to all the others ; also particular
directions for procuring and applying some of the most
interesting subjects for examination.

In regard to Spectacles, Eye-Glasses, and Lenses for
optical purposes of every description, his assortment is
most extensive and complete. To this branch of his
business he devotes special attention, furnishing Glasses
or Pebbles that are truly ground, and properly adapted
to the sight ; feeling that so important a matter as

PREFACE. IX

vision should receive more attention than is usually
given.

He also begs leave to inform his patrons and the
public, that he has recently much enlarged his estab-
lishment, increased his stock of instruments, and added
to his machinery, tools, and fixtures; and as these
instruments are mostly manufactured on his own
premises, he is enabled to improve and simplify their
construction, and personally attend to the finishing,
proving, and packing of the same. With very few ex-
ceptions, they are kept ready made, and orders will be
executed without delay.

Extracts from Notices of the First Edition by the
Press.

"A new and useful work, in two neatly-printed and profusely illus-
trated volumes, and can not but be exceedingly useful as giving pub-
licity to one of the best assorted and beautifully finished collections of
Philosophical, Mechanical, and Chemical Apparatus, in the country.
Each instrument is described, and its price appended, together with
much other valuable information, not easily obtained elsewhere." —
Farmer and Mechanic.

"In these volumes the latest and most improved Chemical, Mathe-
matical, and Philosophical instruments of all kinds, are fully described
and arranged under appropriate heads. An engraving of each accom-
panies the description, which embraces the particulars of the construc-
tion, and uses of each article, and also the price at which it can be
procured." — Day-Book.

" This book will be found a convenient manual of reference for in-
struction in the necessary manipulations of philosophical apparatus :
the requisite information upon which has hitherto been scattered

through many volumes An instance of private enterprise to

which no parallel exists in this country; nor indeed are we aware of
anything, covering so large a field, being put forth in the unpretend-
ing shape of a list of manufactured articles, even from European

presses Such a catalogue must be a valuable boon to all who

are engaged in scientific pursuits ; and professors of colleges, teachers,
and others, will find it of infinite service ' in the selection and use of
illustrative apparatus in every department of science." " — Lit'y World.

" The information embodied in this work must prove valuable, if
not indispensable, to men of science and skill, to the manufacturer
and mechanic, and indeed to all who have taken an interest in the ex-
perimental operations of natural philosophy, and the progressive ad-
vancement of science. It will interest the curious in such matters,
while it becomes a vademecum to the man of science." — Merchant's May.

" No similar catalogue can be found elsewhere. The work is not a
mere catalogue ; it is a museum to which the lovers of science may re-
sort, and where they may examine the various apparatus which have
been contrived to illustrate and explain the phenomena of nature, or
to explore ' the heavens above and the earth beneath, and the waters
that are upon the earth.' The work is embellished with over seven
hundred and fifty good engravings of all manner of instruments, which
are here thoroughly delineated and described, in the various depart-
ments of the arts — Electricity, Galvanism, Magnetism, Pneumatics,
Hydrostatics, Mechanics, Optics, Astronomy, Meteorology, Naviga-
tion, Surveying, Chemistry, &c. The prices of the article are plain-
ly designated. The work is neatly bound and finished — altogether,
being a curious and interesting publication." — Tribune.

" These two volumes contain cuts and descriptions illustrative of
the construction and uses of the great variety of instruments, &c.,
manufactured by the author. 'Pike's' has long been a resort for
everything in the way of instruments in use by the different learned
professions." — N. Y. Observer.

CATALOGUE, & c ,

A CASE OF MATHEMATICAL INSTRUMENTS.

A Pocket Case of Mathematical Instruments (see Fig. 1,
next page) usually contains the following, viz. :

1 Pair of 5 -inch plain compasses,

2 Pair of 6 -inch drawing compasses, with one leg or point

movable,

3 Pencil point,

4 Ink point,

5 One for dotting,

6 Drawing pen, with a protracting pin in the handle,

7 Protractor in the form of a semicircle,

8 Plain scale,

9 Parallel rule,

10 Sometimes a sector,

11 Also sometimes a bow pen,

12 Pencil.

Price $3.50 ; $5.00 ; $8.50.

A Magazine Case of Instruments (see Fig. 2, page 14),
of fine quality, contains —

1 Pair of 6-inch drawing compasses, with a movable leg,

2 Ink point,

3 Pencil point,

3 Lengthening piece,

4 Pair of 5-inch hair compasses,

5 Drawing pen, with ivory handle,

6 Bow pen,

7 Bow pencil,

8 Knife, file, key, and screw-driver, for the compasses, in

one piece,

12 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

(Fig. 1.)

MATHEMATICAL INSTRUMENTS. 13

0 Drawing pencil,

x 0 Ivory sector,

11 Ivory parallel rule,

12 Ivory protractor and plane scale combined.

The most extensive sets contain, in addition —

13 Pair of proportional compasses,

14 Pair of triangular compasses,

15 Pair of bisecting compasses,

16 Pair of fine steel bow dividers,

17 Fine steel bow pen,

18 Fine steel bow pencil,

19 Small fine drawing pen,

20 Double drawing pen,

21 Fine dotting instrument with set of movable rollers,

22 Needle holder.

Price, mounted in German silver, $20.00.
" larger sets, $35.00 to $80.00.
" plain brass sets, $3.25 ;
$3.75;
$4.50;

" " " $5.00;

" " " $9.00.

14 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

(Fig. 2.)

MATHEMATICAL INSTRUMENTS. 15

COMPASSES.

COMPASSES are made of brass, or fine German silver, and
with steel points. In good instruments the joints should
be framed of different substances ; one side or part should be
of German silver or brass, and the other of steel, as the
difference in the metals diminishes the wear and promotes
uniformity in their motion ; all shake and irregularity at the
joint is a sign of imperfection. The points should be of
steel, so tempered as neither to be easily bent nor broken;
fine and tapering, and meeting closely when shut.

Plain compasses are used to measure small distances, and
for subdividing them ; drawing circles, arches, or for con-
structing any proposed figure ; in plotting, or making plans.
The use of the compasses occurs in every branch of prac-
tical mathematics.

The Drawing Compass. — (Fig. 3, page 17.) — These com-
passes are chiefly designed for drawing circles and circular
arches ; and it is often necessary they should be drawn with
different materials, and therefore this pair of compasses has,
in one of its legs, a triangular socket and screw, to receive
and fasten the following parts or points for that purpose, viz. :

1. A steel point, which, being fixed in the socket, makes
the compasses then but a plain pair for drawing blank circles,
setting off lines, &c.

2. A pencil point (Fig. 4, page 17), for receiving a pencil
or crayon, in using which the lines can be easily rubbed out
if not right.

3. The dotting points (Fig. 5, page 17), or dotting pen,
with a small indented wheel at the end, moving very freely,
and receiving ink from the pen over it, communicates the
same in equal and regular dots upon the paper, where dotted
lines are chosen. In the most costly instruments one of the
blades of this instrument is jointed, and by loosening the
strew, may be separated from the other* and wheels mark-
ing- different figures used ; as a dot, a short line, a long line,
a dot and a line, two dots and a line, &c. Also, by taking
off the wheel it may be used as a pen for drawing very wide

16 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

ink lines, the pen causing the ink to flow freely in a v*ry
wide line,

4. The ink point, or pen, (Fig. 6, page 17), for drawing
and describing lines in ink ; for this purpose the two blades
or sides of the pen are opened or closed with an adjusting
screw, that the line drawn may be as fine or as coarse as
you please ; in fine instruments, one of the blades is framed
with a joint, that the points may be separated, and thus
cleaned more conveniently. In the pencil point, dotter, and
pen point, there is a joint by which you can set the lower
part always perpendicular to the paper, which is necessary
for drawing a line well in every opening of the compasses.

5. Lengthener. — (Fig. 7, page 17.) — One or two additional
pieces are often applied to the best compasses ; these by
lengthening the leg enable them to strike larger circles, or
measure greater extents than they would otherwise per-
form, and that without the inconvenience that would attend
using long compasses.

Compasses of the best kind are frequently framed at the
end of the shank, so as to form a strong spring, and the
points and lengthener slide into this socket, and are firmly
held. The best description are furnished with joints in one
or both legs, that they may be placed perpendicular to the
paper. Price, in German silver, $12 to $18.

Hair Compasses. — (Fig. 8, page 19.) — They are so named,
on account of a contrivance in the shank to set them with
greater accuracy than can be effected by the motion of the
joint alone. One of the steel points is fastened near the
top of the compasses, and may be moved very gradually by
turning the screw either backwards or forwards. To use
these compasses, 1st, place the leg to which the screw is
annexed, outermost ; 2d, set the fixed leg on that point from
whence the extent is to be taken ; 3d, open the compasses
as nearly as possible to the required distance, and then
make the points accurately coincide therewith, by turning
the screw. Price, in brass, $2.00 to $3.00.

" in German silver, $2.00 to $4.00.

The Drawing Ren. — (Fig. 9, page 19.) — This pen is used
to draw straight lines ; it consists of two blades with steel
points fixed to a handle. The blades are so bent that the
ends of the steel points meet, and yet leave a sufficient cavity

MATHEMATICAL INSTRUMENTS.

Fig. 3.

Fig. 7.

Fig. 5

Fig. 4.

18

for the ink ; the blades may be opened more or less by a
screw, and being properly set, will draw an equal and regu-
lar line of any desirable thickness. One of the blades is
formed with a joint, but the points may be separated and
thus cleaned more conveniently. A small spring is some-
times inserted between the blades, to act against the mov-
able blade, and serves to steady it in drawing wide lines ; in
pens with metal handles there is usually inserted in the
middle part a fine point, which, when unscrewed, can be used
for making a nice dot, or mark, on paper ; or to set off
divisions from the protractor. Price, $1.25.

The Steel Drawing Pen. — (Fig. 10, page 19.) — Is form-
ed of two blades of steel joined at the top, both immovable
except from the spring of the steel, and terminated with
very fine points. The screw in the middle of the blades
will draw the points close together, or allow them to sepa-
rate sufficiently to clean. This pen is mostly used for very
fine lines, and is mounted with an ivory handle.

Price, $1.25.

The Road Pen (Fig, 11, page 19), or double drawing
pen, is formed of two steel pens joined together with a
haHdle, and having a screw whereby they can be set nearer
or wider, at the pleasure of the drawer, and will draw two
parallel lines in any direction ; is much used in laying down
roads and canals, in drawings where they are required.

Price, $3.00 and $3.50.

The Dotting Pen. — (Fig. 12, page 19.) — This instrument
consists of two blades of metal, formed as the drawing pen,
one of which is jointed, and by loosening the screw may be
separated from the other at its point ; near the point of the
fixed blade is fastened a short pin, on which small indented
steel wheels of different figures can be placed, and allowed
to revolve freely when passed over paper ; it is fed with ink
from the blades over it, and communicates the same in equal
and regular dots, lines, ar a combination of dots and lines,
according to the figure of the wheels or rollers used. This
instrument is particularly useful where a number of courses
are to be laid down on one map or plan, and it is required
to distinguish each readily. It may also be used without
the rollers as a drawing pen for drawing very wide ink lines ;

MATHEMATICAL INSTRUMENTS.

Fig. 9.

Fig. 10. Fig. 11. Fig. 12. Fig. 13

Fig. 8.

10

Fig. 14.

20 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

the width of the point and the pin causing the ink to flow
freely, in a much wider line than the usual drawing pen.
This is a very beautiful instrument, and when well made
its use may be of great advantage in many drawings.

Price, $2.25 to $6.00.

Needle Holder. — (Fig. 13, page 19.) — Is used for holding
a needle, or other fine point, in pricking off spaces from the
protractor, scales, etc. It consists of an ivory handle,
terminated with a small round metallic shaft and point,
perforated with a small hole and slit, on this moves a slide ;
when the needle is introduced, the slide is drawn down, and
the needle held firmly for use ; the top of the handle is
made to screw off, having a cavity for holding the needles.
Price, in German silver, $1.25.

(Fig. 14, page 19.) — The knife, file, key, and screw-
driver for the compasses in one piece. Price $1.25.

Bow Compasses. — The common compasses are not so well
adapted for small drawings as this small kind, Called
Bows ; they are used to describe small circles and arches,
which may be nicely drawn with them, as, from the shape
of the head, which is a short stem or shaft, the instrument
may be made to roll with great ease between the fingers.

Bow Pen. — (Fig. 15, page 21.) — The same as the last
with the ink point or pen, instead of the plain point.

Price, in brass, $1.00.

" in German silver, $1.38.

Bow Pencil.— (Fig. 16, page 21.) — The same, with the
pencil point in place of the plain point.

Price, in brass, $1.00.

" in German silver, $1.38.

Bow Pen, jointed in the legs. — (Fig. 17, page 21.)

Price, in brass, $3.00.

" in German silver, $3.75.

Bow Pencil, jointed in the legs. — (Fig. 18, page 21.)

Price, in brass, $3.00.

" in German silver, $3.75.

MATHEMATICAL INSTRUMENTS.

21

22 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fine French Bow Pen.—(Yig. 19, page 21.)

Price $1.75 to 3.00.

Bow Compass, with shifting leg and points, — (Fig. 20,
page 21.) — The general construction is the same as the
ordinary compass, with a socket in the leg to insert the ink
or pencil point at pleasure, as in the large drawing com-
passes. Price,"$2.50 to 3.50.

Steel Bow Dividers.— (Fig. 21, page 21.)— These are a
still finer description of instrument, much used by good
draughtsmen in forming small centres, repeating divisions
of a small but equal extent, etc. Price, $2.00.

Steel Bow Pen.— (Fig. 22, page 23.)— The same as the
steel bow, with the ink point in place of the plain point.

Price, $2.25.

•

Steel Bow Pencil. — (Fig. 23, page 23.) — The same as
the steel bow, with the pencil point in place of the plain
point. Price, $2.25.

The Universal Bow is formed as a bow pencil, and has a
shaft with one end finely pointed, and on the other a pen
for ink, either end of this can be inserted in the pencil
holder, and secured by its spring or screw ; thus combining
the three in one instrument. Price, $3.00 to 4.00.

Needle Point Instruments. — (Fig. 24, page 23.) — Com-
passes and bow instruments are sometimes formed with
arrangements for using needles for their points, and are
called needle point instruments, and serve very well for
delicate purposes. We give here a representation of a bow
instrument with needle point, and the ink and pencil points
to turn on a swivel, either of which can be in a moment
brought into use ; the bow is also jointed in the legs. It
is a very desirable and useful instrument.

Price, $3.50 to 7.00.

Proportional Compasses (Fig. 25, page 25), consists of
two parts or sides of brass, which lie upon each other so
nicely as to appear but one when they are shut. These
sides easily open, and move about a centre which is itself

MATHEMATICAL INSTRUMENTS. 23

movable in a hollow canal cut through the greater part of
their length. To this centre, on each side, is affixed a slid-
ing piece of a small length, with a fine line drawn on it,
serving as an index, to be set against other lines or divisions
placed upon the compasses. Thus, by placing the index
against 1, and screwing it fast, if you open the compasses
then the distance between the points at each end will be
equal. If you place the index against 2, and open the com-
passes, the distance between the points of the longer legs
will be twice the distance between the shorter ones; and
thus a line is bisected, or divided, into two equal parts. If
the index be placed against 3, and the compasses opened,
the distance between the points will be as 3 to 1, and so a line

Fig. 24.

Fig. 22.

24 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

is divided into three equal parts ; and thus you proceed for
any number of parts under 10 or 12. There are also some-
times placed on the face, a scale of plans, solids, and circles.
They are sometimes made with an adjusting screw, or a
tooth and pinion to move the slide, and which admits of
great nicety in the adjustment of the index.

Price, in brass, $4.50 ; with rack and ) ~fi

pinion motion, j"

" German silver, $7.00 ; " " $8.50.

" with adjusting points, $2.00 extra.

Bisecting Compasses, or whole and halves. — (Fig. 26,
page 25.) — A name given to these compasses, because,
when the longer legs are opened to any given line, the
shorter ones will be opened to the half of that line ; being
always a bisection.

Price, in brass, $2.00 to $3.00.

" in German silver, $3.00.

Triangular Compasses. — (Fig. 27, page 25.) — They con-
sist of a pair of compasses, to whose head a joint and
socket is fitted for the reception of a third leg, which may
be moved in almost every direction. These compasses,
though exceedingly useful, are but little known ; they are
very serviceable in copying all kinds of drawings, as from
two fixed points they will always ascertain the exact posi-
tion of a third point.

Price, in German silver, $5.00 and $7.00.

The Pillar Compasses. — (Fig. 28, page 27.)— A universal
instrument, and is, when opened, about six inches long;
the points are made to turn up so as to occupy but about
half that space ; within the two legs are contained the ink
and pencil points, held firmly by a spring joint ; either of
these can be taken out and the plain points inserted in their
places. Thus, by shifting them around, making a pair of
compasses with plain point, ink point, and pencil point.
Also, the points can be used — taken out of the legs of the
instrument — as bow pen, and bow pencil, there beino- a
small head attached to each for that purpose. This instru-
ment forms in itself a pocket case of instruments.

Price, in brass, $4.00 to $6.50.

" in German silver, $5.00 to $10.00.

MATHEMATICAL INSTRUMENTS.

25

Fig 25.

Fig. 26.

Fig 27.

26 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

The Universal Tube Compass, with points to turn. —
(Fig. 29, page 29.) — This instrument consists of two Ger-
man silver or brass tubes, connected by a joint as other
compasses, having other tubes sliding firmly and evenly
within them ; at the outer ends of the inner tubes are affixed
a joint and pieces, to which are attached the points, which
are fixed in pairs; the pencil point at one end, and a plain
point at the other, in one arrangement, and the ink point
and a plain point in the other arrangement ; each of which
is movable in a swivel, and can be turned round so as to
bring either point into use as may be required. When a
longer space is wanted than can be conveniently extended
in the ordinary state of the instrument, the movable tubes
can be drawn out, and thus a larger pair of compasses form-
ed. They also can be used as a beam compass within the
limits of the slides, having both the points turned parallel
to each other, and also perpendicular with the paper.

Price, in German silver, $12.00.

Beam Compasses (Figs. 30 and 31, page 27) are used
for describing large arches, and bisecting lines or arches.
These compasses consist of a long beam, made of brass or
wood, furnished with two brass boxes, the one fixed at
the end, the other sliding along the beam, to any part of
which it may be firmly fixed by a screw. An adjusting
screw is adapted to the box at the end of the beam ; by
this the point connected therewith may be moved with
extreme regularity and exactness.

Price, $4.00 to 10.00.

Drawing Pins (Fig. 32, page 29), are used for fastening
to the drawing board paper, for which purpose one is
pressed through each corner of the paper into the board,
firmly securing the paper thereby.

Price, in brass, per dozen, 75cts.

" in German silver, do. 88cts.

Metal Centres, having two or more very delicate pins, to
fasten to the paper used in drawing, where the points of the
dividers are frequently to be placed on one centre, and
preventing the injury to the paper that would arise from
placin"1 the points thereon many times.

Price, 25 to 50cts.

MATHEMATICAL INSTRUMENTS.

Fig 28.

28 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

The Protractor (Fig. 33, page 30) is an instrument used
to protract, or lay down an angle containing any number
of degrees, or to find how many degrees are contained in
any given angle.

The Semicircular Protractor is divided into one hundred
and eighty equal parts or degrees, which are numbered at
every tenth degree each way, for the convenience of
-reckoning either from the right hand towards the left, or
from the left towards the right ; or the more easily to lay
down an angle from either end of the line, beginning at
each end with 10, 20, etc., and proceeding to 180 degrees.
The straight side is the diameter of the semicircle, and the
mark or small notch in the middle points out the centre.
Price, in brass, 4 inch SOcts.
5 " 75cts.

6 inch, divided to one-half degrees, $1.25.

7 inch, $1.50.

Ivory Protractors (Fig. 34, page 31), in the form of a
parallelogram, or long square, are usually contained in the
best cases of mathematical instruments, and are more exact
than the common semicircular ones for angles to forty or
fifty degrees ; because at and about each end the divisions
being further from the centre are larger ; the side of these
protractors to be applied to the paper is flat, on which is
marked the lines of the plane scale, and that whereon the
degrees are marked is sloped away to the edge, that an
angle may be more easily measured, and the divisions set
off with greater exactness. Price, $1.50 to $4.00.

Protractors of Horn are, from their transparency, very
convenient in measuring angles, and raising perpendiculars.
When they are out of use they should be kept in a book to
prevent their warping. Price, 4 inch, 2 Sets.

'• 5 " 50cts.

6 inch, divided to half degrees, 88cts.

7 " * • " " $1.25.

The Plane Scale.— (Fig. 35, page 33.)— The divisions
used for measuring straight lines are called scales of equal
parts, and are of various lengths, for the convenience of
delineating any figure of a larger or smaller size, according
to the fancy or purposes of the draughtsman. They are a
measure in miniature for laying down upon paper, &c.,

MATHEMATICAL INSTRUMENTS.

Fig. 29.

Fig. 30.

29

Fig. 31.

1
J

Fig. 3-2.

3*

30

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

Fis 33- any known measure, as

chains, yards, feet, &c. ;
and the plan will be
larger or smaller as the
scale contains a smaller
or greater number of
parts in the inch. Hence
a variety of scales are
useful to lay down lines
of any required length,
and of a convenient pro-
portion with respect to
the size of the drawing.
If none of the scales
happen to suit the pur-
pose, recourse should
be had to the sector.

The plane scale (Fig.
35),in the common cases
of instruments, has the
following lines of scales
upon it, viz. 1. A line
of 6 inches. 2. A line
of 50 equal parts. 3. A
diagonal scale. 4. A
line of chords marked
C. 5. Seven particular
scales of equal parts,
or decimal scales of dif-
ferent sizes. The num-
bers placed at the beginning of each denote how many of
the small divisions at the beginning are contained in one
inch, viz. 20, 25, 30, 35, 40, 45, 55. On the lines over the
spaces containing the decimal divisions, is marked a line of
twelve parts to the same space, answering for measures re-
duced from feet and inches.

The line of chords. — This line is used to set off an angle
from a given point in any right line, or to measure the quan-
tity of an angle already laid down. Thus, to draw an
angle of a given number of degrees, say 35, open your
compasses to the extent of 60 degrees upon the line of
chords, and with that opening of the compasses describe an
arch ; then, taking the extent of 35 degrees from the chord

MATHEMATICAL INSTRUMENTS.
Figs. 34.

32 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

line, set it in the arch described, and the angle formed by
lines drawn through these points is 35 degrees. The de-
grees contained in an angle to be measured, are found in
nearly the same manner.

Price, in ivory, 6 inch, 88cts.; 12 inch, $3. 00 to $8.00.
" in brass, " " $1.50 " " $3.00.

The Sector. — (Fig. 36, page 35.) — Of all mathematical
instruments that have been contrived to facilitate the art of
drawing, there is none so extensive in its use as the sector.
It is a universal scale. It not only contains the most useful
lines, but by its nature renders them of general application ;
uniting, as it were, angles and parallel lines, the rule and
the compass. The sector is usually six inches long when
closed, and forms a rule of twelve inches long when open.
The sector consisting of two pairs, or legs, movable upon a
central joint, it is requisite that the lines should be laid on
the sector by pairs, viz. one of a sort on each leg, and all
of them issuing from the centre ; all of the same length,
and every two containing the same angle. The scales or
lines graduated upon the faces of the instrument, and which
are used as sectoral lines, are, 1, two scales of equal parts
called the line of lines, and marked L ; 2, two scales of
chords, marked c ; 3, two scales of secants, marked s ; 4, a
line of polygons, marked POL. Upon the other face ; 5,
two lines of sines, marked s ; 6, two lines of tangents, mark-
ed T ; 7, another line of tangents extending from 45 to 75
degrees ; the first only extending to 50. Besides these,
when the sector is quite opened, there is on one side, 1,
Gunter's line of artificial numbers, marked N ; 2, line of
artificial sines, marked s : 3, line of artificial tangents,
marked T ; and on the other side a line of twelve inches
divided in tenths, and on the edge, the foot divided into
100 parts. To explain the proper use of all these sectoral
lines would require more space than can be given in this
work. A few examples will be given.

1. In the line of equal parts. — Having three numbers
given to find a fourth proportional. To do this, take in
your compasses the lateral extent of sixteen divisions in the
line of lines, and apply it by a proper opening of the sector
from 4 to 4 in these lines ; then take the parallel distance
from 7 to 7 in your compasses, with the same opening of
the sector, and apply one foot of the compasses to the com-

MATHEMATICAL INSTRUMENTS

'I!

33

*TT

31

JU

rm

Q

6?

34 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

mencement of these lines, and the other will fall on 28, the
number required. For as 4 is to 7 so is 16 to 28.

2. In the Lines of Chords. — Suppose it required to lay
off an angle equal to 25 degrees, with any convenient
opening of the sector, take the extent in the lines marked
c, from 60 to 60, and with it describe an arch indefinitely ;
then, with the same opening of the sector, take the parallel
distance from 25 to 25, and set it in the arch described,
lines drawn from these points in the arch to its centre, will
give the angle required.

3. In the Lines of Sines. — The lines of sines, tangents,
ind secants, are used in conjunction with the line of lines in
the solution of all the cases of plain trigonometry ; thus,
suppose we are 230 feet from a spire, or elevation, the
n eight of which we wish to measure, we ascertain the angle
rormed at that distance by the base and point of the spire
Dy means of a quadrant, and find it to be 36 degrees and
30 minutes ; consequently, the other angle being its com-
plement must be 53^ degrees ; we now take the lateral
distance, 230, from the line of lines, and make it a parallel
from 53;f degrees to 53^ degrees in the line of lines ; then
the parallel distance between 36 j in the same lines, will
reach lateially from the centre to 170 in the line of lines,
for the height of the spire 170 feet.

4. Polygons. — If we open the sector any convenient
distance, and take with the compasses the distance 6 and 6
on these lines, and inscribe a circle, the whole circumference
will be divided by it into 6 parts ; then, if you take the
distance 4 and 4 on the same lines, it will be divided into
four parts, and you have a square inscribed in the circle ;
if you take 7 and 7 you have a heptagon, or seven sided
figure, and so on with all the divisions of these scales.

A great number of problems of much interest may be
solved by means ot these, and the other lines of the sector.

Price, in ivory, $1.50.
" in brass, $1.50.

Architect's Scale. — (Fig. 3"/, page 37.) — Scales are usually
divided into tenths ; those expressly for architects are divided
into twelve parts, to correspond to the measure used by
carpenters and masons. They are usually made of ivory,
and six, nine, and twelve inches long ; one side is slanted
off ai each edge, having scales of |, |, |, 1 inch, marked

MATHEMATICAL INSTRUMENTS
Figs. 33.

35

- "» H H

36 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

thereon ; these are very convenient, as any proportion may
be marked off, from the edge, directly on the drawing,
without the use of a pair of dividers ; the scales on the
other part are usually f , |, f , f-, and on the other side of
the scale 1±, 1£, If, 2, 2±, 2|, 3 inch.

Price, 6 in. "in ivory, $2.50~ ; 9 in. $3.00.; 12 in. $4.00.
" in brass, from - - $1.00. to $3.00.

The Parallel Rule (Fig. 38, page 37) is used for drawing
one or more lines parallel to, or equally distant from, any
line proposed. It consists of two straight rules, which are
connected together, and always maintained in a parallel
position by the two equal and parallel bars, which move
very freely on the centre, or rivets, by which they are
fastened to the straight rules.

Price, in black ebony, 6 in., 62c. ; 9 in., 88c. ; 12 in., $1 ;
15 in., $1.25; 18 in., $1.50:
24 in., $2.50 ; 36 in., $5.00.
" in ivory, 6 in., $1.50 ; 12 in., $3.00.

Double Parallel Rule. — (Fig. 39, page 38.) — This instru-
ment consists of two equal flat rules, and a middle piece ;
they are connected together by four brass bars. The ends
of two bars are riveted on the middle line of one of the
straight rules ; the ends of the other t\vo bars are riveted
on the middle line of the other straight rule ; the other
ends of the brass bars are taken two and two, and riveted
on the middle piece, as is evident from the figure ; the brass
bars move freely on their rivets, as so many centres. The
advantage of this rule is, that in using it the movable rule
may always be so placed, that its ends may be exactly over,
or even with, the ends of the fixed rule ; whereas, in the
former kind, they are always shifting away from the ends
of the fixed rule. Price, 6 inch, ivory, $3.50.

" 12 " "" $7.00.

EcTchardCs, or Rolling Parallel Rule. — (Fig. 40, page
38.) — This is a rule of black ebony, with slips of ivory laid
on the edges of the rule, and divided into inches and tenths.
The rule is supported by two small wheels, which are con-
nected together by a long axis, the wheels being exactly of
the same size, and their rolling surfaces being parallel to the
axis ; when they are rolled backwards or forwards, the axis

MATHEMATICAL INSTRUMENTS.

Figs. 37.

T

fi

•

Fig. 38.

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

and rule will move in a
^^^^_ direction parallel to them-
selves. The wheels are
somewhat indented, to pre-
vent their sliding on the
paper ; small ivory cylin-
ders are sometimes affixed
to the rollers, as in the
figure. The circumferences
of these are so adjusted,
that they indicate with ex-
actness the parts of an inch
moved through by the
rule.

In rolling these rules,
one hand only must be used,
and the fingers should be
placed nearly in the mid-
dle of the rule, that one
end may not have a ten-
dency to move faster than
the other ; the wheels only
should touch the paper
when the rule is moving,
and the surface of the pa-
per smooth and flat.

Price, 12 in., $5.50.

The T Square.— (Figs.
41 and 42, page 39.) —
This is a very useful article
in drawing. A ruler, about
two to three feet in length,
made of hard wood, or
steel, is fixed, as a square,
to the middle of a piece
of hard wood, about one
foot long and two inches
wTide, and on one side a loose piece is fastened by a thumb
screw, which passes through both pieces, allowing both to be
clamped together at any angle, thus forming a bevel.

The head of the square, applied close to the edge of a
true drawing board, will admit of true lines being drawn as

MATHEMATICAL INSTRUMENTS. 30

Fig. 4.. Fig. 42. Fig. 43.

Fig. 44. Fig. 46.

40 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

well as oblique ones, with more ease and expedition than by
the common parallel rule.

Price, 75 cts. to $2.50.

with steel blade, $3.00 to $5.00.

The T Square and Protractor. — (Fig. 43, page 39.) —
This instrument is formed of a divided arc of brass, usually
about ten inches in diameter, whose graduation commences
at the middle, and is continued each way to 90 degrees ; at
the centre of the arc is attached a movable arm, about 30
inches long ; at the shorter end is a vernier, running on the
graduated arc, and subdividing the degrees of the arc into
minutes, and having a spring bent over to the under side of
the arc, with a screw to clamp it fast in any position. Used
on a true drawing board, this instrument is simple and con-
venient, answering all the purposes of plotting and protract-
ing of a square and bevel, and for drawing parallel lines in
different directions. Price, $7.00 to $12.00.

Gauge for measuring Diameters, Interiors, etc. — (Fig. 44,
page 39), with steel blades and brass sliding bars, the bars
sliding within each other, and graduated to inches and
tenths, with one, two, or three slides.

Price, $1.50 to $7.50.

Draughtsman's Squares. — (Figs. 45 and 46, page 39.) —
These squares are best made of hard wood, and are used
with a common flat ruler, one of the edges of the square
being placed against the rule, and by holding the rule fast,
and moving the square, parallel lines may be drawn with
ease and accuracy. One of the squares represented is a
solid one, having a hole for the finger to move it by. The
other is open in the centre, and is used where they are
required of a large size.

Price 25 cents to 75 cents.

Curves. — (see pages 41, 42, 43.) — These are various in
shape and size, and from 0 to 24 inches long. Their use is
to present a variety of forms for drawing curves, and they
are extensively used in naval architecture and other draw-
ings. Price, 38 cents to 50 cents each.
. The set of 25, $7.

MATHEMATICAL INSTRUMENTS. 41

Fig. 47. Fig. 48. Fig. 49. Fig. 50.

yj

Fig. 51. Fig. 52. Fig. 53. Fig. 54. Fig. 55.

42 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 56. Fig. 57. Fig. 58. Fig. 59.

MATHEMATICAL INSTRUMENTS. 43

Fis.G3. Fig. 66. Fig. 67. Fig. 68.

Centrolinead. — (Fig. 74, page 45.) — The Centrolinead is an
instrument used in perspective drawing, for drawing lines to-
wards a distant centre, as towards a distant vanishing point.
They are made in pairs right and left. In the cut, the blades
are represented as broken off. Price, with blades, each $10.

Improved Circular Protractor. — (Fig. 75, page 45.) —
This instrument consists of an entire circle, A A, connected

44 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

with its centre by four radial bars, a a. &c. The centre of
the metal is removed, and a circular disk of glass fixed in
its place, on which are drawn two lines crossing each other
at right angles, and dividing the small circle into four quad-
rants, the intersection of the lines denoting the centre of the
protractor. When the instrument is used for laying down
an angle, the protractor must be so placed on the paper
that its centre exactly coincides with, or covers the angular
point ; which may easily be done, as the paper can be seen
through the glass centre-piece.

Round the centre, and concentric with the circle, is fitted
a collar, b, carrying two arms, c c, one of which has a
vernier at its extremity adapted to the divided circle, and
the other a milled-head, d, which turns a pinion, working
in a toothed rack round the exterior circle of the instrument ;
sometimes a third arm is applied at right angles to the
other two, to which the pinion is attached, and a vernier
can then, if required, be applied to each of the other two,
and it also prevents the observer disturbing that part of the
instrument with his hand when moving the pinion. The
rack and pinion give motion to the arms, which can thus be
turned quite round the circle for setting the vernier to any
angle that may be required. Upon a joint near the extremi-
ty of the two arms (which form a diameter to the circle)
turns a branch, e e, which for packing may be folded over
the face of the instrument, but when in use must be placed
in the position shown in the figure : these branches carry,
near each of their extremities, a fine steel pricker, the two
points of which, and the centre of the protractor, must, for
the instrument to be correct, be in the same straight line.
The points are prevented from scratching the paper as the
arms are moved round, by steel springs, which lift the
branches a small quantity, so that, after setting the centre
of the protractor over the angular point, and the vernier in
its required position, a slight downward pressure must be
given to the branches, and each of the points will make a
fine puncture in the paper ; a line drawn through one of
these punctures and the angular point will be the line
required to form the angle.

Any inaccuracy in placing the centre of the protractor
over the angular point may easily be discovered, for, if in-
coriectly done, a straight line " drawn through the two
punctures in the paper will not pass through the angular
point, which it will do, if all be correct.

MATHEMATICAL INSTRUMENTS.

45

The face of the glass centre-piece, on which the lines are
drawn, is placed as nearly even with the under surface of the
instrument as possible, that no parallax may be occasioned
by a space between the lines and the surface of the paper.

By help of the vernier, the protractor is graduated to
single minutes, which, taking into consideration the numer-
ous sources of inaccuracy in this kind of proceeding, is the
smallest angular quantity that we can pretend to lay down
with certainty. Price, $18.00 to $40.00.

Fig. 74,

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.
Fig. 76.

The Pantagraph. — (Fig. 76, as above.) — The pantagrapli
is usually made of ebony or brass, from 12 to 24 inches long,
and consists of four flat rules, two of them long and two of
them short. The two longer are joined at the end by a
double pivot, which is fixed to one of the rules, and works in
two small holes placed at the end of the other. Under the
joint is an ivory castor, to support this end of the instrument.
The two smaller rules are fixed by pivots near the middle of
the larger rules, and are also joined together at their other
end ; by the construction of this instrument, the four rules
always form a parallelogram. There is a sliding box on the
longer arm, and another on the shorter arm. These boxes
may be fixed at any part of the rules, by means of their
milled head screws ; each of these boxes is furnished with
a cylindrical tube, to carry either the tracing point, crayon,
or fulcrum. The fulcrum or support, B, Fig. 76, is a leaden
weight ; on this the whole instrument moves when in use,
there being movable rollers under different parts of the in-
strument to facilitate the movement thereof. The gradua-
tions are placed on two of the rules, B and D, with the pro-
portions of ^, ^-, ^, &c., to yV, marked on them. The pencil

MATHEMATICAL INSTRUMENTS. 47

holder, tracer, and fulcrum, must in all cases be in a right
line, so that when they are set to any number, if a string be
stretched over them, and they do not coincide with it, there
is an error either in the setting or the graduations. The long
tube that carries the pencil, or crayon, moves easily up or
down in another tube, passing afterwards through the holes
in the three small knobs to the tracing point, where it may,
if necessary, be fastened. By pulling this string, the pencil
is lifted up occasionally, and thus prevented from making
false or improper marks upon the copy.

To Reduce in any proportions, £, |, {, etc., as marked on
the bars. — Suppose, for example, ^ is required : place the
two sockets at \ on the bars B and D, place the fulcrum
or lead weight at B, the pencil socket with pencil at D,
and the tracing point at C. Fasten down upon a smooth
board, or table, a sheet of white paper under the pencil D,
and the original map, &c., under the tracing point C ; al-
lowing yourself room enough for the various openings of
the instrument. Then, with a steady hand, carefully move
the tracing point C over the outlines of the map, and the
pencil D will describe exactly the same figure as the original,
but half the size. In the same manner for any other propor-
tion, by only setting the two sockets to the number of the
required proportion. The pencil holder moves easily in the
socket to give way to any irregularity in the paper. There
is a cup at the top for receiving an additional weight, either
to keep down the pencil to the paper, or to increase the
strength of its mark.

If the original should be so large, that the instrument
will not extend over it at any one operation, two or three
points must be marked on the original, and the same to cor-
respond on the copy. The fulcrum and copy may then be
removed into such situations as to admit the copying of the
remaining part of the original; first observing, that when
the tracing point is applied to the three points marked on
the original, the pencil falls on the three corresponding points
upon the copy. In this manner, by repeated shiftings, a
pantagraph may be made to copy an original of ever so
large dimensions.

To enlarge in any of the proportions, ^, ^, j, (fee. — Sup-
pose £. You set the two sockets at J, as before, and have
only to change places between the pencil and tracing point,
viz. to place the tracing point at D, and the pencil at C.

48 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

To copy off the same size, but reversed, place the two
sockets at J, the fulcrum at D, and the pencil at B.
Price, ebony bars and brass mounting, $7.50 to $14.00.
" all brass, - - - $15.00 to $30,00.

SURVEYING INSTRUMENTS,

SURVEYOR'S LAND CHAIN.

GUNTER'S Chain (Fig. 77, page 51) is the one now com-
monly used in taking the dimensions of land ; it is sixty-six
feet, or four poles, in length, and is divided into 100 links,
each of which is joined to the next by three rings; the
length of each link, including the connecting rings, is 7.92
inches, and at the end of every tenth link is attached a piece
of brass (each of a different shape) for more readily count-
ing the odd links.

Short distances, or offsets from the chain line, are usually
measured with a rod, called an off-set staff, the most con-
venient length for which is 6 feet 7.2 inches, being equal to
10 links of the chain, and it should be divided accordingly.

With the chain should be provided ten arrows, which may
be made of strong iron wire, about 12 or 15 inches long,
pointed at one end for piercing the ground, and turned up
at the other, in the form of a ring, to serve as a handle:
their use is to fix in the ground at each extremity of the
chain whilst measuring, and to point out the number of
chains measured. Price, 2 pole, $1.00 and $1.25.

" 4 " $2.25 to $2.75.

Perambulator, or Measuring Wheel. — (Fig. 78, page 51.)
— An instrument which being run along a road or other
level surface indicates and registers the exact distance it
passes over. The general form of the instrument, and its
system of wheel-work, are as follows : —

The wheel is 8^- feet in circumference, and consequently

measures exactly a pole in every two revolutions. The

number of revolutions made, and consequently the distance

passed over, is seen on the dial-plate, where there are two

5

50 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

hands, one moving round a circle, upon which are inscribed
yards, poles and furlongs ; the other, that is the shorter
hand, indicates the number of miles travelled.

Price, $50.00.

Tape Measure, — (Fig. 79, page 51.) — This instrument
consists of a tape prepared and painted, or varnished, on
which is divided feet and inches, one end of which is attach-
ed to a brass axis having a handle, by turning which the
tape is wound up in a small compass, and inclosed usually
in a leather box ; to the other end of the tape a ring is at-
tached, by which the tape may be drawn out, the measure-
ment commencing at the ring ; on one side there are frequently
divided links, 100 of which make a chain, or 66 feet.

Price, 25 feet long, $1.25 ; 30 feet long, $1.37.

" 40 " " $1.50; 50 " " $1.75.

60 " " $2.00; 100 " " $3.00.

Pocket Tape Measure. — (Fig. 80, page 51.) — These are

from three to twelve feet long, and mounted in a variety of

styles, some having springs by which the tape is drawn in

when required, and are mounted in brass or German silver.

Price, 3 feet, brass case, - - $0.63.

6

a « »

- $0.88.

12

« « <

- $1.25.

3

(( <( t

with spring, $1.25.

6

n « <

$1.50.

3

" Germans ver, " " $2.00.

Plumb Bob. — (Fig. 81, page 51.) — This consists of a cone
of metal with steel point and rounded top, suspended by a
cord, for which a small perforated piece of brass is screwed
into the top, within which the knot fastening the cord is
tied. Price, 2 inch, $1.25; 3 inch, $2.00.

" 4 " - $2.50.

Pocket Compass. — (Fig. 82, page 53.) — The pocket com-
pass is a very valuable instrument to travellers, and persons
visiting pathless forests, or unfrequented places, as by the
help of this little instrument they may direct their course
with certainty in any direction ; they are usually made in
small brass boxes, from one inch to two inches in diameter,
and half an inch thick ; the points of the compass are repre-

SURVEYING INSTRUMENTS.
Fig. 77. Fig. 78.

51

52 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

sen ted on a card at the bottom of the box, and over it the
magnetic needle is suspended on a fine point, a glass cover
ing the needle, and a brass cap covering the Avhole.

Price, - 3 Sets.

" two sizes larger 50cts., and 63cts.

(Fig. 83, page 53) represents a pocket compass in ?
watch form, with a pendant, the case usually gilt and neatly
and lightly made. Price, $1.00.

(Fig. 84, page 53) represents a pocket compass of the
best make, having an enamelled dial with all the 360 degrees
and all the points of the compass marked thereon, having a
fine edge bar needle with agate centre, a stop to lift the
needle from the fine point on which it turns, to prevent
unnecessary wear when not in use ; the case is either of
silver or well gilt, and is enclosed in a morocco case.

Price, strong gilt case, $9.00.
" silver case, $12.00.

Pocket Compasses (Fig. 85, page 53) in square wood cases,
with lever to stop the magnetic needle when the lid is closed,
but on opening the lid, is left free to assume its directive
tendency.

Price, 2 inch, $1.25 ; 2£ inch, $1.50 ; 3 inch, $2.00.

The Mariner's Compass (Fig. 86, page 53) consists of a
magnetic needle, formed of a thin plate of steel, about six
inches long, and half an inch wide, having at its centre a
cap fitted to it, usually having an agate centre, which is
supported on a sharp pointed pivot fixed in the base of the
instrument ; beneath the needle is fixed a circular card, on
the circumference of which are divided 360 degrees, while an
inner circle, described on it, is marked with the thirty-two
points, of which the four, viz. North, South, East, and
West, are called cardinal points, .while intermediate between
these are N.E. or north-east, S.E. or south-east, s.w. ot
south-west, N.W. or north-west, N.b.E. is north by east, N.N.E
is north of north-east, etc. ; the pivot of support rises from
the bottom of a circular box, which contains the needle and
its card, and is covered with a glass ; the compass box i?
suspended within a larger square box, by means of twe
concentric brass circles, or gimbals, as they are called, th<?

SURVEYING INSTRUMENTS.
Fig. 82. Fig-. 83.

54 BEXJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

outer one being fixed by horizontal points, both to the inner
circle which carries the compass box, and also to the outer
box ; and the two sets of axes being in directions at right
angles to one another, by the combinations of movements
determined by these axes, the inner circle, with the compass
box and its contents, always retains a horizontal position dur-
ing the rolling of the ship ; and the pilot, by looking at the
position of the needle, can steer his course in any required
direction. Although the north pole of the magnet, in every
part of the world, when freely suspended, points to the
northern parts, and the south pole to the southern parts,
yet its ends seldom point exactly towards the poles of the
earth. The angle in which it deviates from due north and
south is called the angle of declination, or the variation of
the compass ; and this declination is said to be east or west,
according as the north pole of the needle is eastward or
westward of the astronomical meridian of the place. This
deviation from the meridian is not the same in all parts of
the world, but is different in different places, and it is even
continually varying in the same place ; the present declina-
tion of the needle is

Price, with wood bowl, $2.50.
Fjg-87 " " brass " $4.50.

Brass Boat Compass. — (Fig. 87.) — The brass
boat compass with nautical floating card.

Price, 2£ inch diameter, $2.25.
" 3" " " $2.75.

The Azimuth Compass. — (Fig. 88, page 55.) — The azi-
Aiuth compass differs from the ordinary mariner's compass,
only in the circumference of its inner box being provided
with sights, through which any object, either in the horizon
or above it, may be seen, and its bearings from the magnetic
points of the compass determined, by reference to the posi-
tion of the card, with respect to the sights. For this pur-
pose the whole box is hung in detached gimbals, which
turn on a strong vertical pin fixed below the box, which is
thus capable of being moved around horizontally, and of
the sights being directed to whatever object is to be viewed
through them. On one side of the box there is usually
inserted a nut, or stop, which, when pushed in, presses
against the card and stops it ; this is done to enable the

SURVEYING INSTRUMENTS.
t- 83.

55

observer to read off the number of degrees from the card,
which correspond with an index, or perpendicular line,
drawn on the inside of the box.

Description. — The semicircle A B is fixed by a screw at its
middle, or lowest point, to a stand at the bottom of the
outer box containing the whole apparatus, in such a manner
as to admit of its being turned round horizontally, and
placed in all azimuths. To the upper extremities of this
semicircle a brass circle c D is fixed by two pivots, constitut-
ing a horizontal axis of motion ; while the inner cylindrical
brass box p Q, containing the compass, is attached to the
brass circle c D by similar pivots, of which one is seen at g,
forming a horizontal axis at right angles to the former, and
both together acting as gimbals. The compass with its
card is balanced in the usual manner on a pointed pivot
rising from the centre of the bottom of the inner box, the
upper side of which is covered with a circular glass. The
two sights E and o are fixed vertically on the upper side of
the cylinder of this box, diametrically opposite to each other ;
the one, E, to which the eye is intended to be applied, con-

56 BENJ. PIKE 8, JR., DESCRIPTIVE CATALOGUE.

sists of a brass slip, having a narrow vertical slit ; the other,
o, which is turned to the object, is a similar slip, having an
oblong aperture containing a fine thread, passing along the
middle of the open space in a vertical direction. Two ver-
tical lines are also marked on the inside of the box, which
are prolongations of the slit in the sight for the eye, and of
the thread in that for the object. These lines are intended
as indexes for the measurement of the angular distance in
azimuth of an object viewed through the two sights, from
the place of the magnetic meridian, as shown by that por-
tion of the graduated edge of the card which coincides with
the line with which it is compared.

Price, 88.00 to $20.00.

The Prismatic Compass. — (Fig. 89, as below.) — The use
of this little instrument is to measure horizontal angles only,
and from its portability it is particularly adapted for military
surveying, or where but little more than a sketch map of the
country is required. It is also very useful in filling in the
detail of a map, where all the principal points have been
correctly fixed by means of the theodolite. It may likewise
be used for determining approximately the direction of the
true meridian, the variation being determined by comparing
the observed azimuth of a celestial object, with its true
azimuth deduced from an observation made for the purpose.

Fig. 89.

SURVEYING INSTRUMENTS. 5*1

In the preceding figu- e, A represents the compass box, and
B the card, which, being attached to the magnetic needle,
moves as it moves, round the agate centre, a, on which it
is suspended. The circumference of the card is usually
divided to 30' of a degree ; c is a prism, which the
observer looks through in observing with the instrument.
The perpendicular thread of the sight-vane, E, and the
divisions on the card appear together on looking through th(
prism, and the division with which the thread coincides
when the needle is at rest, is the magnetic azimuth of what-
ever object the thread may bisect. The prism is mounted
with a hinge joint, D, by which it can be turned over to
the side of the compass box, that being its position when
put into the case. The sight-vane has a fine thread stretched
along its opening, in the direction of its length, which is
brought to bisect any object, by turning the box round
horizontally ; the vane also turns upon a hinge joint, and
can be laid flat upon the box, for the convenienceof car-
riage. F is a mirror, made to slide on or off the sight-vane,
E ; and it may be reversed at pleasure, that is, turned face
downwards ; it can also be inclined at any angle, by means
of its joint, d ; and it will remain stationary on any part of
the vane, by the friction of its slides. Its use is to reflect
the image o'f an object to the eye of the observer when the
object is much above or below the horizontal plane. When
the instrument is employed in observing the azimuth of the
sun, a dark glass must be interposed; and the colored
glasses represented at G, are intended for that purpose ;
the joint upon which they act allowing them to be turned
down over the sloping side of the prism box.

At e is shown a spring, which, being pressed by the
finger at the time of observation, and then released, checks
the vibrations of the card, and brings it more speedily to
rest. A stop is likewise fixed at the other side of the box,
by which the needle may be thrown off its centre ; which
should always be done when the instrument is not in use,
as the constant playing of the needle would wear the point
upon which it is balanced, and upon the fineness of the
point much of the accuracy of the instrument depends. A
cover is adapted to the box, and the whole is packed in a
case, which may be carried in the pocket without incon-
venience.

The method of using this instrument is very simple. First

58

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

raise the prism in its socket, b, until you obtain distinct
vision of the divisions on the card, and standing at the
place where the angles are to be taken, hold the instrument
to the eye, and looking through the slit, c, turn round till
the thread in the sight- vane, bisects one of the objects
whose azimuth or angular distance from any other object
is required ; then, by touching the spring, e, bring the needle
to rest, and the division on the card which coincides with
the thread on the vane, will be the azimuth or bearing of
the object from the north or south points of the magnetic
meridian. Then turn to any other object, and repeat the
operation ; the difference between the bearing of this object
and that of the former, will be the angular distance of the
objects in question. Suppose the former bearing to be 40°
30', and the latter 10° 15', both east, or both west, from
the north or south, the angle will be 30° 15.' The divi-
sions are generally numbered 5°, 10°, 15°, etc., round the
circle to 360°. A stand can be had with the instrument,
if required, on which to place it when observing, instead of
holding it in the hand. Price, $16.00 and $20.00.

The Plane- Table.— (Fig. 90, as below.) — Before the theo-
dolite came into general use, the plane-table was extensively
employed in the practice of surveying ; it is still sometimes,
chough seldom, used in surveying small plots of ground, or

Fig. 90.

SURVEYING INSTRUMENTS. 59

(where great accuracy is not required) in forming a sketch
map, or laying down the details of a country where the
relative situation of the principal conspicuous objects have
been previously fixed by triangulation. The expedition with
which such work may.be performed, by a person who is expert
in the use of this instrument, is its chief recommendation.

The construction and size of the plane-table have been
varied at different times, to suit both the convenience and
intentions of the surveyor ; but the annexed figure is a re-
presentation of that which is now in most general use. It
is a board, as A, about sixteen inches square, having its
upper edge rabbeted, to receive a boxwood frame, B, which
being accurately fitted, can be placed on the board in any
position, with either face upwards. This frame is intended
both to stretch and retain the drawing paper upon the board,
which it does by being simply pressed down into its place
upon the paper, which for this purpose must be cut a little
larger than the board.

One face of the frame is divided to 360 degrees, from a
centre, 0, fixed in the middle of the board, and these are
subdivided as minutely as the size of the table will admit.
The divisions are frequently numbered each way, to show
at sight both an angle and its complement to 360°. There
is sometimes a second centre piece, D, fixed on the table, at
about a quarter of its width from one of the sides, and at
exactly half its length in the other direction. From this cen-
tre, and on the other side of the frame, there are graduated
180° ; each of these degrees is subdivided to 30 minutes,
and numbered 10, 20, 30, &c., both ways, to 180. The
object of these graduations is, to make the plane-table sup-
ply the place of the theodolite, and an instrument formerly
in use called a semicircle. The reverse face of the frame is
usually divided into equal parts, as inches and tenths, for
the purpose of ruling parallel lines or squares, and for shift-
ing the paper, when the work requires more than one sheet.
G is a compass-box, let into one side of the table, with a
dove-tail joint, and fastened with a milled-headed screw,
that it may be applied or removed at pleasure. The com-
pass, besides rendering the plane-table capable of answering
the purpose of a circumferentor, is principally useful in
setting the instrument up at a new station parallel to any
position that it may have had at a former station, as well as
a check upon the progress of the work.

CO BEXJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

The ruler or index, E, is made of brass, as long as the
diagonal of the table, and about two inches broad ; it has a
sloping edge, like that of a Gunter's scale, which is called
the fiducial edge. A perpendicular sight vane, F F, is fixed
to each extremity of the index, and the eye looking through
one of them, the vertical thread in the other is made to
bisect any required distant object. Upon the flat surface
of the index, there are frequently engraved scales of various
kinds, such as lines of equal parts, with diagonal scales, a
line of chords, &c.

To the under side of the table, a centre is attached with
a ball and socket, or parallel plate-screws like those of the
theodolite, by which it can be placed upon a staff-head ;
and the table may be set horizontal, by means of a circular
spirit-level placed upon it for that purpose.

Price, $20.00 to $35.00.

Fig. 91.

Surveyor's Cross. — The surveyor's cross
(Fig. 91) consists of two pair of sights,
placed at right angles to each other. These
sights are sometimes pierced out in the
circumference of a thick tube of brass, or
sides of a square box, about three inches
in diameter. It has a socket, which, when
in use, is screwed on a staff, having a sharp
point at the bottom to stick in the ground.
The more improved instruments are made
octangular, having the intermediate angle
of 45 degrees also pierced.

Price $3.00 to $6.00.

Circumferentor, or Surveyor s Compass. — (Fig. 92, next
page.) — This instrument consists of a brass plate, usually
about fourteen or fifteen inches long, with sights at each
end, and in the middle thereof a circular box with a glass
cover, usually from five to seven inches diameter ; within
the box is a brass graduated circle, the upper surface divid-
ed into 360 degrees, and frequently subdivided into half
degrees, and numbered from the north and south points
each way from 0 to 90. On the face of the plate are en-
graved the principal points of the compass, a fleur de lis
answering for the north. In the middle of the box is placed
a steel pin finely pointed, called the centre pin, on which is

SURVEYING INSTRUMENTS.

61

poised a magnetic needle, which, if freely mounted, will rest
in the position called the magnetic meridian ; and however
the instrument may be moved about, the bearing or angle
which any line makes with the magnetic meridian is at once
shown. The sights at the ends of the plate are fastened in

Fig. 92.

62 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

their position, perpendicular to the plate, by milled-head
screws, and may be detached for convenient transportation ;
in each sight there is a large and small aperture, or slit, the
one over the other ; these are alternate, that is, the large
aperture being above the smaller in one of the sights, and
below it in the other ; a fine piece of sewing silk is fastened
vertically through the middle line of the large slit, through
small holes for the purpose. Under the compass box is a
socket to fit in the pin of the staff ; the instrument may be
turned around on this pin, or fixed in any situation by the
milled-head screw ; it may also be readily fixed in a hori-
zontal direction by the ball and socket of the staff, moving
for this purpose the box, till the ends of the needle are
equidistant from the bottom, and traverse or play with
freedom.

There are usually one or two levels on the plate of the
instrument, for more accurately finding a horizontal position.
A spring is also placed within the box, having a milled-head
screw acting against it, by which the magnetic needle can
be lifted off the centre pin and the cap pressed against the
glass, to preserve the point of the centre pin from being blunt-
ed by the continual friction of the cap of the needle. The
most improved instruments have a loose plate, to which is at-
tached the compass box, having a vernier over a graduated arc
on the face of the brass plate ; by this contrivance the compass
box may be moved about its centre without moving the
plate to which the sights are attached ; a long screw with a
milled head being on the opposite side of the compass box, for
the purpose of giving a slow motion when required. Sup-
pose the needle to rest between two of the divisions on the
graduated circle ; by this vernier the number of minutes
contained between the needle and either of the divisions is
indicated. The sights also are improved, having small slits
in both the upper and lower part, in which holes are placed
alternately, for taking sight through.

To use the Circumferentor, or Surveyor's Compass, — Sup-
pose a given angle to be measured ; the instrument being
fixed on the staff, place its centre over one of the points of
the angle, set it horizontal by moving the ball in its socket
till the needle is parallel to the bottom of the compass box,
or the levels indicate a horizontal position ; turn the end of
khe compass box on which the N or fleur de lis is engraved
next the eye, look through the sights to one of the objects

SURVEYING INSTRUMENTS.

forming the angle to be measured, and observe at vhat
degree the needle stands, suppose 40, turn the instrument
around on the pin of the ball and socket till you can see the
object forming the other angle, and suppose the needle now
to stand at 85, take the former from the latter, and the
remainder, 45, is the required angle.
Packed in a mahogany case, with lock,

Price, with 4 in. needle, $14.00.

" with 5 in. needle,

" with 6 in. needle,

" with nonius, 5 in.

" with nonius, 6 in.

$20.00 and $22.50.
$28.00 and $32.00.
$30.00.
$35.00 to $42.

Fi- 93.

Plane Surveyor's Compass. — The above engraving (Fig. 93)
represents a low-priced surveyor's compass, that is very use-
ful to farmers and others, in running lines and laying out their

G4 BEXJ. PIKE'S, JR.. DESCRIPTIVE CATALOGUE.

fields, as well as in surveying them. It is used by setting it
on the top of a post, fence, &c. Its diameter is 4 inches.
Packed in a mahogany case, Price $5.00.

Fig. 91

The Graphometer, and Four Sighted Tfieodolite. — (Fig. 94,
as above.) — The error arising from the use of an instrument,
where the whole dependence is placed on the needle, being
frequently influenced by local attractions, has rendered it
necessary for some other method to be employed to measure
angles with accuracy ; among these the common theodolite
with four sights has taken the lead.

It is simple in its construction, and easy in its use.

The annexed figure represents the graphometer, a brass
plate or part of a circle about twelve inches in diameter,
graduated on its edge from 0 to 180 degrees; in the open-
ing between the moving centre and the graduated arc, is a
compass about four inches in diameter ; two sights are fixed
on the graduated arc, one at 0 a~nd the other at 180°. Per-
pendicular to the plane of the instrument, there is a movable
limb attached to the limb of the arc, but a little shorter, and
having the extremities slanted off, one of which forms a
nonius, subdividing the degrees on the limb to minutes, and
having two sights, one at each end ; in each sight there is a
large and a small aperture, placed alternately, the large
aperture in one sight being always opposed to the narrow
aperture in the other ; underneath the plate is a spring to
fit on the pin of a ball and socket, which fixes it the single
or three legged staff, as may be required. In the figure the
ball and socket are represented detached from the instrument.

The Four Sighted Theodolite is the same instrument, ex-

SURVEYING INSTRUMENTS. 65

cept that the circle is entire, and the compass is placed in
the centre of the circle.

Cautions in using the instrument. — 1. Spread the legs that
support the theodolite rather wide, and thrust them firmly
into the ground, that they may neither yield nor give un-
equally during the observation. 2. Set the instrument
horizontal. 3. Screw the ball firmly in its socket, that in
turning the index the theodolite may not vary from the ob-
jects to which it is directed. 4. Where accuracy is required,
the angles should always be taken twice over, oftener where
great accuracy is material, and the mean of the observation,
must be taken for the true angle.

To measure an angle with the Theodolite. — Let ABC repre-
sent the angle to be measured ; place the theodolite over
the angular point A, and direct the fixed sights along one of
the lines, till you see through the sights the point B ; at this
screw the instrument fast ; then turn the movable index till
through its sights you see the other point, c ; then the de-
grees cut by the index upon the graduated limb or ring of
the instrument show the quantity of the angle.

The fixed sights are always to be directed to the last
station, and those of the index to the next.

Price, 8 inch, in case, $15.00.
" 12 " " $30.00.

The Quadrant. — (Fig. 95, next page.) — The Quadrant
consists of an arc firmly attached to two radii, or bars,
which are strengthened and bound together by two braces.

Of the Index. — The Index is a flat bar of brass attached
to the centre of motion. At the lower end of the index
there is an oblong opening ; to one side of this opening a
nonius scale is fixed to subdivide the divisions of the arc.
At the bottom, or end of the index, there is a piece of
brass, which bends under the arc, carrying a spring to make
the nonius scale lie close to the divisions ; it is also fur-
nished with a screw to fix the index in any desired position.
The best instruments have an adjusting screw fitted to the
index, that it may be moved more slowly, and with greater
regularity and accuracy than by the hand. The circular
arcs on the arc of the quadrant are drawn from the centre
on which the index turns. The position of the index on ths
arc, after an observation, points out the number of degrees
and minutes contained in the observed angle.
6*

66 BENJ. PIKE S, .JR., DESCRIPTIVE CATALOGUE.

Of the Index Glass. — Upon the index, and near its axis,
is fixed a plain speculum, or mirror of glass, quicksilvered.
It is set in a brass frame, and is placed so that the face of

Fig. 93.

A. Frame and arc ; B. Index : C. Nonius scale ; D Index glass ; E. Dark glass
er screens; F. Horizon glass ; G. Vane or sight

SURVEYING INSTRUMENTS. 67

it is perpendicular to the plane of the instrument; this
mirror being fixed *to the index, moves along with it, and
has its direction changed by the motion thereof; this glass
is designed to receive the image of the sun, or any other
object, and reflect it on the horizon glass. The brass frame
with the glass is fixed to the index by screws which serve
to adjust it in a perpendicular position.

Of tlie Horizon Glass. — On the radius of the frame is a
small speculum, the surface of which is parallel to the index
glass, when the counting division of the index is at O on
the arc, and receives the reflected rays from the object, and
transmits them to the observer. -The horizon glass is not
entirely quicksilvered, but only on its lower half, or that
next to the frame of the quadrant, the other half being
transparent ; and the back part of the frame is cut away, that
nothing may impede the sight through the unsilvered part
of the glass. The edge of the foil of this glass is about pa-
rallel to the plane of the instrument, and ought to be very
sharp, and without a flaw ; the glass is set in a brass frame,
to which there is an axis which passes through the wood-
work, and is fitted to a lever on the under side of the
quadrant; by this lever the glass may be turned a few
degrees on its axis, in order to set it parallel to the index
glass ; the lever has a contrivance to turn it slowly. To
set this glass perpendicular to the plane of the quadrant
there are two sunk screws, one before and one behind the
glass ; these screws pass through the plate on which the
frame is fixed, into another plate, so that by loosening one,
and tightening the other of these screws, the direction of
the frame, with its mirror, may be altered, and thus set
perpendicular to the plane of the instrument.

Of the Shades. — These are two red, or dark, and one
green glass ; they are used to prevent the rays of the sun
from hurting the eye at the time of observation ; they are
each of them set in a brass frame, which turns on a centre,
so that they may be used separately, or together, as the
brightness of the sun may require. These glasses are fixed
on the frame, between the index and the horizon glasses.

Of the Sight Vane. — This is a piece of brass fixed on the
frame opposite the horizon glass, perforated with two small
holes, one exactly at the height of the quicksilvered edge
of the horizon glass ; the other somewhat higher, to direct
the sight to the middle of the transparent part of the mirror

68 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

for those objects that are bright enough to be reflected from
the unsilvered part of the mirror. •

The Arc and Nonius. — The Arc is divided into 90 degrees
from the right to the left, and each degree is subdivided
into three parts, or 20 minutes, which are again subdivided
by the Nonius into every minute. The Nonius is numbered
at every fifth of three divisions, from the right to the left,
with 5, 10, 15 and 20. The first division to the right hand
being to be considered the index division.

Directions to hold the Quadrant. — It is recommended
to support the weight of the instrument by the right hand,
and reserve the left to govern the index ; place the thumb
of the right hand against the edge of ihe quadrant, under
the swelling part on which the sight stands, extending the
fingers across the back of the quadrant, so as to lay hold on
the opposite edge, placing the .forefinger above, and the
other fingers below the swelling part, or near the horizon
glass ; thus the instrument may be supported conveniently
in a vertical position, by the right hand only. By resting the
thumb of the left hand against the side, or the fingers
against the middle bar, you may move the index gradually
either way.

To adjust the Quadrant. — It is a peculiar excellence of
the Quadrant that the errors to which it is liable are easily
detected and soon rectified ; the observer may, therefore, if
he will be attentive, always put his instrument in a fit state
for accurate observation.

1. To adjust the Index Glass, or make it perpendicular
to the Plane of the Instrument. — Hold the Quadrant in a
horizontal position, with the index glass close to the eye,
look nearly in a right line down the glass, and in such a
manner, that you may see the arc of the quadrant by direct
view, and by reflection at the same time. If they join in
one direct line, and the arc seen by reflection forms an
exact plane with the arc seen by direct view, the glass is
perpendicular to the plane of the quadrant ; if not, the
error must be rectified by altering the position of the screws
behind the frame.

2. To adjust the Horizon Glass, and set it parallel to the
Index Glass. — Set the index line of the nonius exactly at o
on the limb, and fix it there by the screw at the under side.
Now look through the sight at some distant small object ;
the object will be seen directly through the unsilvered part

SURVEYING INSTRUMENTS. 69

of the glass, but by reflection in the silvered part ; if the
object in the silvered part exactly meets, and forms one con-
tinued line with that seen through the unsilvered part, then
is the instrument said to be adjusted, and the horizon glass
to be parallel to the index glass ; but if the objects do not
coincide, then loosen the screw on the under side of the
quadrant, and turn the horizon glass on its axis, by means
of its adjusting lever, till you have made them perfectly
coincide. This adjustment ought to be examined before
every important observation.

3. To adjust the Horizon Glass perpendicular to the Plane
of the Quadrant. — Incline the quadrant on one side as much
as possible, provided the distant object continues to be seen
in both parts of the glass at the same time. If, when the
instrument is thus inclined, the object continues to form an
unbroken line, the quadrant is perfectly adjusted ; but if the
reflected object be separated from that seen by direct vision,
the glass is not perpendicular to the plane of the quadrant ;
and if the observer is inclined to the right, with the face of
the quadrant upward, and the reflected object appears higher
than the real object, you must slacken the screw before the
horizon glass, and tighten that which is behind it ; but if the
reflected object appears lower, the contrary must be per-
formed. Care must be taken in these adjustments to loosen
one screw before the other is screwed up, and to leave the
adjusting screws tight, or so as to draw with a moderate
force against each other.

Price $14.00 to $18.00.

Sextant. — (Fig. 96, page 70.) — The annexed figure re-
presents a sextant of Trough ton's construction, having a
double frame, A A, connected by pillars, a at &c., thus
uniting strength with lightness. The arc, B C, is generally
graduated to 10' of a degree, commencing near the end, C,
and it is numbered towards B. The divisions are also con-
tinued on the other side of zero, towards C, forming what
is called the arc of excess, which is useful in determining
the index error of the instrument, as will be explained here-
after. The limb is subdivided by the vernier, E, into 10",
the half of which (or 5") can be easily estimated : this
small quantity is easily distinguishable by the aid of micro-
scope, H, and its reflector, b, which are connected by an arm
with the index, I E, at the point, c, round which it turns as

70 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 96.

11

a centre, affording the means of examining the whole ver-
nier, the connecting arm being long enough to allow the
microscope to pass over the whole length of it.

To the index is attached a clamp to fasten it to the limb,
and a tangent-screw, J (in the plate, the clamp is concealed
from view), by which the index may be moved any small
quantity after it is clamped, to render the contact of the
objects observed more perfect than can be done by moving
it with the hand alone. The upper end, I, terminates in a
circle, across which is fixed the silver-indexed glass, F, over
the centre of motion, and perpendicular to the plane of the
instrument. To the frame at G is attached a second glass,
called the horizon-glass, the lower half of which only is
silvered : this must likewise be perpendicular to the plane
of the instrument, and in such a position that its plane shall
be parallel to the plane of the index-glass, F, when the
vernier is set to 0° (or zero) on the limb, B C. A devia-
tion from this position constitutes the index error before
spoken of.

SURVEYING INSTRUMENTS. l

The telescope is carried by a ring, L, attached to a stem,
e, called tlie up-and-down piece, which can be raised or
lowered by turning the milled screw, M : its use is to place
the telescope so that the field of view may be bisected by
the line on the horizon-glass that separates the silvered from
the unsilvered part. This is important, as it renders the
object seen by reflection, and that by direct vision, equally
bright ; two telescopes and a plain tube, all adapted to the
ring, L, are packed with the sextant, one showing the objects
erect, and the other inverting them ; the last has a greater
magnifying power, showing the contact of the images much
better. The adjustment for distinct vision is obtained by
sliding the tube at the eye-end of the telescope in the inside
of the other ; this also is the means of adapting the focus
to suit different eyes. In the inverting telescope are placed
two wires, parallel to each other, and in the middle of the
space between them the observations are to be made, the
wires being first brought parallel to the plane of the sextant,
which may be judged of with sufficient exactness by the
eye. When observing with this telescope, it must be borne
in mind, that the instrument must be moved in a contrary
direction to that which the object appears to take, in order
to keep it in the field of view.

Four dark glasses, of different depths of shade and color,
are placed at K, between the index and horizon glasses ;
also three more at N, any one or more of which can be
turned down to moderate the intensity of the light, before
reaching the eye, when a very luminous object (as the sun)
is observed. The same purpose is effected by fixing a dark
glass to the eye-end of the telescope: one or more dark
glasses for this purpose generally accompany the instrument.
They, however, are chiefly used when the Sun's altitude is
observed with an artificial horizon, or for ascertaining the
index error, as employing the shades attached to the instru-
ment for such purposes, would involve in the result any
error which they might possess. The handle, which is shown
at 0, is fixed at the back of the instrument. The hole in
the middle is for fixing it to a stand, which is useful when
an observer is desirous of great steadiness.

Of the adjustments. — The requisite adjustments are the
following : the index and horizon-glasses must be perpen-
dicular to the plane of the instrument, and their planes
parallel to each other when the index division of the vernier

72 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

is at 0° on the arc, and the optical axis of the telescope must
be parallel to the plane of the instrument. We shall speak
separately of each of these adjustments.

To examine the adjustment of the Index-glass. — Move the
index forward to about the middle of the limb, then, hold-
ing the instrument horizontally with the divided limb from
the observer, and the index-glass to the eye, look obliquely
down the glass, so as to see the circular arc, by direct view
and by reflection, in the glass at the same time ; and if they
appear as one continued arc of a circle, the index-glass is
in adjustment. If it requires correcting, the arc will appear
broken where the reflected and direct parts of the limb
meet. This, in a well-made instrument, is seldom the case,
unless the sextant has been exposed to rough treatment.
As the glass is in the first instance set right by the maker,
and firmly fixed in its place, its position is not liable to alter,
therefore no* direct means are supplied for its adjustment.

To examine the Horizon-glass, and set it perpendicular to
the Plane of the Sextant. — The position of this glass is
known to be right, when by a sweep with the index, the
reflected image of any object passes exactly over or covers
its image, as seen directly ; and any error is easily rectified
by turning the small screw, i, at the lower end of the frame
of the glass.

To examine the Parallelism of the Planes of the two
Glasses, when the Index is set to Zero. — This is easily ascer-
tained ; for, after setting the zero on the index to zero on
the limb, if you direct your view to some object, the sun
for instance, you will see that the two images (one seen by
direct vision through the unsilvered part of the horizon-
glass, and the other reflected from the silvered part) coin-
cide or appear as one, if the glasses are correctly parallel to
each other ; but if the two images do not coincide, the
quantity of their deviation constitutes what is called the
index error. The effect of this error on an angle measured
by the instrument is exactly equal to the error itself; there-
fore, in modern instruments, there are seldom any means
applied for its correction, it being considered preferable to
determine its amount previous to observing, or immediately
after, and apply it with its proper sign to each observation.
The amount of the index error may be found in the follow-
ing manner : clamp the index at about 30 minutes to the
left of zero, and looking towards the sun, the two images

SURVEYING INSTRUMENTS. 73

will appear either nearly in contact, or overlapping each
other ; then perfect the contact, by moving the tangent-screw,
and call the minutes and seconds denoted by the vernier, the
reading on the arc. Next, place the index about the same
quantity to the right of zero, or on the arc of excess, and
make the contact of the two images perfect as before, and
call the minutes and seconds on the arc of excess the read-
ing off the arc ; and half the difference of these numbers is
the index error ; additive when the reading on the arc of
excess is greater than that on the limb, and subtractive
when the contrary is the case.

EXAMPLE. , „

Reading on the arc - - 31 56

off the arc - 31 22

Difference - - - - 0,34

Index error - = — 017

In this case, the reading on the arc being greater than
that on the arc of excess, the index error, = 17 seconds,
must be subtracted from all observations taken with the
instrument, until it be found, by a similar process, that the
index error has altered. One observation on each side of
zero is seldom considered enough to give the index error
with sufficient exactness for particular purposes : it is usual
to take several measures each way ; " and half the differ-
ence of their means will give a result more to be depended
on than one deduced from a single observation only on each
side of zero."

To make the Line of Collimation of the Telescope parallel
to the Plane of the Sextant. — This is known to be correct,
when the sun and moon, having a distance of 90 degrees or
more, are brought into contact just at the wire of the tele-
scope which is nearest the plane of the sextant, fixing the
index, and altering the position of the instrument to make
the objects appear on the other wire ; if the contact still
remains perfect, the axis of the telescope is in proper ad-
justment ; if not, it must be altered by moving the two
screws which fasten, to the up-and-down piece, the collar
into which the telescope screws. This adjustment is not
very liable to be deranged.

Of the sextant, it has been said, that it is in itself a port-

74

BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

able observatory ; and it is doubtless one of the most gene-
rally useful instruments that has ever been contrived, being
capable of furnishing data to a considerable degree of ac-
curacy for the solution of a numerous class of the most use-
ful astronomical problems ; affording the means of deter-
mining the time, the latitude and longitude of a place, &c.,
for which and many other purposes, it is invaluable to the
land-surveyor as well as the navigator.

Price, $100 to $120.

Single Framed, 50 to 80.

" Ebony " 35.

Fig. 97.

Pocket Sextant. — (Fig. 97.) — This useful little instrument
is represented in the above figure. The principle of its
construction and adjustment is precisely the same as the
sextant before described ; a minute description, therefore,
would be little more than a recapitulation of what has
already been advanced. A is the index, which, instead of
being moved along the divided limb, ef, by the hand, has a
motion given to it by a rack and pinion, concealed within
the box, and turned by the milled head, B, which acts as the
tangent-screw does to the index of the large sextant. The
glasses (shown at C and D) are within the box, by which
they are protected from injury, and their adjustments, when

SURVEYING INSTRUMENTS. 75

once perfected, kept secure : so much so, that it would re-
quire considerable violence to derange them. The horizon-
glass, D, alone has a contrivance for adjustment at a and
d, both to set it perpendicular to the plane of the instru-
ment, and to correct or reduce the index error, which, in
this instrument, had better be kept correct, as it is not so
likely to get out of order as in the large sextant, which, as
we have before observed, seldom admits of its index error
being rectified. The key, c, is formed to fit both squares at
a and d, to make the adjustments, and it is generally tapt
into some square place in the instrument, as at c, that it
may be always safe and at hand.

It is supplied with a telescope, E, which screws into a
shoulder-piece, F, and can be attached to the box by the
screw G : this can be applied or not, at the pleasure of the
observer, as there is a contrivance at H to enable him to
observe without the telescope, if he prefers plain sights.
Two dark glasses are placed within the box, and there is
also one adapted to the eye-end of the telescope.

The angle is read off by the help of the glass, I, which
being mounted with a joint, can be moved over the vernier
on any part of the limb. The instrument is divided to 30
minutes of a degree, and by the vernier is subdivided to
single minutes, one half of which, or 30 seconds, can be ob-
tained by estimation.

The divided limb is numbered both to the right and left,
commencing at 0° to 120°.

The lid of the box is contrived to screw on the bottom (as
is shown in the plate), where it makes a convenient handle
for holding the instrument. Price $35.00 to $40.00.

Reflecting Circle. — (Fig. 98, next page.) — This instrument,
in principle and use, is the same as the sextant. It has
three vernier readings, ABC, moving round the same cen-
tre as the index-glass, E, which is upon the opposite face
of the instrument. One of the verniers, B, carries the
clamp and tangent-screw. D represents the microscope for
reading the verniers ; it is similar to the one used in reading
the sextant, and is adapted to each index-bar, by slipping it
on a pin placed for that purpose, as shown in the figure.
The horizon-glass is shown at F. The barrel, G, contains
the screws for giving the up-and-down motion to the tele-
scope ; it is put in action by turning the milled head under

76 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 98.

the barrel. H is the telescope; adapted to the instrument
in a manner similar to that of the sextant. I and J are two
handles fixed parallel to the plane of the circle, and a third
handle, K, is screwed on at right angles to that plane, and
can be transferred to the opposite face of the instrument
by screwing it into the handle, I ; the use of this extra
handle is for convenience in reading and in holding the in-
strument, when observing angles that are nearly horizontal ;
it can be shifted, according as the face of the instrument is
held upwards or downwards. The requisite dark glasses
are attached to the frame-work of the circle, to be used in
the same manner and for the same purposes as those of the
sextant. With respect to the adjustments and application
of this instrument, we cannot do better than use the words

SURVEYING INSTRUMENTS. 77

of the inventor, Mr. Troughton, contained in a paper which
he calls

Directions for observing with the Reflecting Circle. — Pre-
pare the instrument for observation by screwing the tele-
scope into its place, adjusting the drawer to focus, and the
wires parallel to the plane, exactly as you do with a sex-
tant ; also set the index forwards to the rough distance of
the sun and moon, or moon and star ; and holding the
circle by the short handle, direct the telescope to the fainter
objects, and make the contact in the usual way. Now
read off the degree, minute, and second, by that branch
of the index to which the tangent-screw is attached ; also,
the minute and second shown by the other two branches ;
these give the distance taken on three different sextants ;
but as yet, it is only to be considered as half an observa-
tion : what remains to be done, is to complete the whole
circle, by measuring that angle on the other three sextants.
Therefore set the index backwards nearly to the same dis-
tance, and reverse the plane of the instrument, by holding
it by the opposite handle, and make the contact as above,
and read off as before what is shown on the three several
branches of the index. The mean of all six is the true
apparent distance, corresponding to the mean of the two
times at which the observations were made.

When the objects are seen very distinctly, so that no
doubt whatever remains about the contact in both sights
being perfect, the above may safely be relied on as a com-
plete set ; but if, from the haziness of the air, too much
motion, or any other cause, the observations have been
rendered doubtful, it will be advisable to make more ; and
if, at such times, so many readings should be deemed trou-
blesome, six observations and six readings may be con-
ducted in the manner following : Take three successive
sights forwards, exactly as is done with a sextant ; only
take care to read them off on different branches of the
index : also make three observations backwards, using the
same caution ; a mean of these will be the distance required.
When the number of sights taken forwards and backwards
is unequal, a mean between the means of those taken back-
wards and those taken forwards will be the true angle.

It need hardly be mentioned, that the shades, or dark-
glasses, apply like those of a sextant, for making the objects
nearly of the same brightness ; but it must be insisted on,

78 BEXJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

that the telescope should, on every occasion, be raised or
lowered, by its proper screw, for making them perfectly so.

The foregoing instructions for taking distances, apply
equally for taking altitudes by the sea, or artificial horizon,
they being no more than distances taken in a vertical plane.
Meridian altitudes cannot, however, be taken both back-
wards and forwards the same day, because there is not
time: all therefore that can be done, is, to observe the
altitude one way, and use the index-error; but even here,
you have a mean of that altitude, and this error, taken on
three different sextants. Both at sea and land, where the
observer is stationary, the meridian altitude should be
observed forwards one day, and backwards the next, and so
on alternately from day to day; the mean of latitudes,
deduced severally from such observations, will be the true
latitude ; but in these there should be no application of
index-error, for that being constant, the result would in
some measure be vitiated thereby.

When both the reflected and direct images require to be
darkened, as is the case when the sun's diameter is measur-
ed and when his altitude is taken with an artificial horizon,
the attached dark glasses ought not to be used ; instead of
them, those which apply to the eye-end of the telescope
will answer much better ; the former having their errors
magnified by the power of the telescope, will, in proportion
to this power, and those errors, be less distinct than the
latter.

In taking distances, when the position does not vary from
the vertical above thirty or forty degrees, the handles which
are attached to the circle are generally most conveniently
used ; but in those which incline more to the horizontal,
that handle which screws into a cock on one side, and into
the crooked handle on the other, will be found more appli-
cable.

When the crooked handle happens to be in the way of
reading one of the branches of the index, it must be remov-
ed, for the time, by taking out the finger-screw, which
fastens it to the body of the circle.

If it should happen that two of the readings agree with
each other very well, and the third differs from them, the
discordant one must not on any account be omitted, but a
fair mean must always be taken.

It should be stated, that when the angle is about thirty

SURVEYING INSTRUMENTS. 79

degrees, neither the distance of the sun and moon, nor an
altitude of the sun, with the sea horizon, can be taken back-
wards ; because the dark glasses at that angle prevent the
reflected rays of light from falling on the index-glass;
whence it becomes necessary, when the angle to be taken is
quite unknown, to observe forwards first, where the whole
range is without interruption ; whereas, in that backwards,
you will lose sight of the reflected image about that angle.
But in such distances, where the sun is out of the question,
and when his altitude is taken with an artificial horizon (the
shade being applied to the end of the telescope), that angle
may be measured nearly as well as any other ; for the rays
incident on the index-glass will pass through the transparent
half of the horizon-glass, without much diminution of their
brightness.

The advantages of this instrument, when compared with
the sextant, are chiefly these : the observations for finding
the index-error are rendered useless, all knowledge of that
being put out of the question, by observing both forwards
and backwards. By the same means the errors of the dark
glasses are also corrected ; for, if they increase the angle
one way, they must diminish it the other way by the same
quantity. This also perfectly corrects the errors of the
horizon-glass, and those of the index-glass very nearly.
But what is of still more consequence, the error of the cen-
tre is perfectly corrected, by reading the three branches of
the index ; while this property, combined with that of ob-
serving both ways, probably reduces the errors of dividing
to one-sixth part of their simple value. Moreover, angles
may be measured as far as one hundred and fifty degrees,
consequently the sun's double altitude may be observed
when his distance from the zenith is not less than fifteen
degrees ; at which altitude, the head of the observer begins
to intercept the rays of light incident on the artificial horizon ;
and, of course, if a greater angle could be measured, it
would be of no use in this respect.

This instrument, in common with the sextant, requires
three adjustments. First, the index-glass perpendicular to
the plane of the circle. This being done by the maker, and
not liable to alter, has no direct means applied to the pur-
pose ; it is known to be right, when, by looking into the
index- glass, you see that part of the limb which is next to
you, reflected in contact with the opposite side of the limb,

80 BEXJ. PIIiE's, JR., DESCRIPTIVE CATALOGUE

as one continued arc of a circle ; on the contrary, when tho
arc appears broken, where the reflected and direct parts of
the limb meet, it is a proof that it wants to be rectified.
The second is, to make the horizon-glass perpendicular.
This is performed by a capstan-screw, at the lower end of
the frame of that glass ; and is known to be right, when,
by a sweep of the index, the reflected image of any object
will pass exactly over, or cover the image of that object
seen directly. The third adjustment is, for making the line
of collimation parallel to the plane of the circle. This is
performed by two small screws, which also fasten the collar
into which the telescope screws to the upright stem on which
it is mounted : this is known to be right, when the sun and
moon, having a distance of one himcLed and thirty degrees,
or more, their limbs are brought in contact, just at the out-
side of that wire which is next to the circle ; and then,
examining if it be the same, just at the outside of the other
wire : its being so is the proof of adjustment.

Piioe $150 to $200.

Theodolite. — (Fig. 99, next page.) — As an angular instru-
ment, the theodolite has from time to time received such
improvements that it may now be considered as the most
valuable instrument employed in surveying. Instruments
of this kind, of the best construction, may to a certain ex-
tent be used as altitude and azimuth instruments ; and seve-
ral astronomical operations, such as those required for de-
termining the time, the latitude of place, &c., may be per-
formed by them, and to a degree of accuracy sufficient for
most of the purposes that occur in the ordinary practice of
a surveyor.

There are various modes of constructing theodolites to
suit the convenience or the views of purchasers ; but we
shall confine ourselves to a description of one of the most
perfect, as a person acquainted with the details of its adjust-
ments and use, will find no difficulty in comprehending those
of others.

Description of the Theodolite. — This instrument consists of
two circular plates, A and B, called the horizontal limb, the
upper or vernier plate, A, turning freely upon the lower, and
both have a horizontal motion by means of the vertical axis,
C ; this axis consists of two parts, external and internal, the
former secured to the graduated limb, B, and the latter to

SURVEYING INSTRUMENTS.
Fig 99.

81

the vernier plate, A. Their form is conical, nicely fitted
and ground into each other, having an easy and a very steady
motion ; the external centre also fits into a ball at D, and the
parts are held together by a screw at the lower end of the
internal axis.

The diameter of the lower plate is greater than that of
the upper one, and its edge is chamfered off and covered
W'th silver, to receive the graduations : on opposite parts of

82 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

the edge of the upper plate, or 180° apart, a short space, a,
is also chamfered, forming with the edge of the lower plate
a continued inclined plane ; these spaces are likewise covered
with silver, and form the verniers. The lower limb is usu-
ally graduated to thirty minutes of a degree, and it is sub-
divided by the vernier to single minutes, which being read
off by the microscope, E, half or even quarter minutes can
easily be estimated.

The parallel plates, F and G, are held together by a ball
and socket at D, and are set firm and parallel to each other,
by four milled head-screws, three of which, b b b, are shown
in the figure : these turn in sockets fixed to the lower plate,
while their heads press against the under side of the upper
plate, and being set in pairs, opposite each other, they act
in contrary directions ; the instrument by this means is set
up level for observation.

Beneath the parallel plates is a female screw adapted to
the staff head, which is connected by brass joints to three
mahogany legs, so constructed that when shut up they form
one round staff, secured in that form for carriage by rings
put on them ; and when opened out they make a very firm
stand, be the ground ever so uneven.

The lower horizontal limb can be fixed in any position, by
tightening the clamping screw, H, which causes the collar c
to embrace the axis, C, and prevents its moving ; but it be-
ing requisite that it should be fixed in some precise position
more exactly than can be done by the hand alone, the whole
instrument, when thus clamped, can be moved any small
quantity by means of the slow-motion screw, I, which is
attached to the upper parallel plate. In like manner the
upper or vernier plate can be fixed to the lower, in any posi-
tion, by a clamp (in the plate this clamp is concealed from
view), which is also furnished with a slow motion, the screw
of which is generally called the tangent-screw. The motion
of this limb and of the vertical arc, hereafter to be described,
is sometimes effected by a rack and pinion ; but this is
greatly inferior, where delicacy is required, to the slow
motion produced by the clamp and 'tangent-screw.

Upon the plane of the vernier plate, two spirit-levels, d,
d, are placed at right angles to each other, with their proper
adjusting screws ; their use is to determine when the hori-
zontal limb is set level ; a compass also is placed at J.

The frames K and L support the pivots of the horizontal

SURVEYING INSTRUMENTS. 83

axis of the vertical arc, or semicircle, M, on which the tele-
scope is placed. The arm which bears the microscope, N,
for reading the altitudes or depressions, measured by the
semicircle, and denoted by the vernier, e, has a motion of
several degrees between the bars of the frame, K, and can
be moved before the face of the vernier for reading it off.
Another arm clamps the opposite end of the horizontal axis
by turning the screw, 0, and has a tangent-screw of slow
motion at P, by which the vertical arc and telescope are
moved very small quantities up or down, to perfect the con-
tact when an observation is made.

One side of the vertical arc is inlaid with silver, and
divided to single minutes by the help of its vernier ; and
the other side shows the difference between the hypothenuse
and base of a right-angled triangle, or the number of links
to be deducted from each chain's length, in measuring up
or down an inclined plane, to reduce it to the horizontal
measure. The level, which is shown under and parallel to
the telescope, is attached to it at one end by a joint, and at
the other by a capstan-headed screw, /, which, being raised
or lowered, will set the level parallel to the optical axis of
the telescope, or line of collimation ; the screw, g, at the
opposite end, is to adjust it laterally, for true parallelism in
this respect. The telescope has two collars, or rings, of
bell metal, ground truly cylindrical, on which it rests in its
supports, h h, called Y's, from their resemblance to that
letter; and it is confined in its place by the clips, i i, which
may be opened by removing the pins, j j, for the purpose
of reversing the telescope, or allowing it a circular motion
round its axis, during the adjustment.

In the focus of the eye-glass are placed three lines,
formed of spider's web, one horizontal, and two crossing it,
so as to include a small angle between them ; a method of
fixing the wires which is better than having one perpendi-
cular wire, because an object at a distance can be made to
bisect the said small angle with more certainty than it can
be bisected by a vertical wire. The screws adjusting the
cross wires are shown at m : there are four of these screws,
two of which are placed opposite each other, and at right
angles to the other two, so that by easing one and tighten-
ing the opposite one of each pair, the intersection of the
cross wires may be placed in adjustment.

The object-glass is thrust outwards by turning the milled

84 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

head. Q, on the side of the telescope, that beir.g the means
of adjusting- it to show an object distinctly.

A brass plummet and line are packed in the box with the
theodolite, to suspend from a hook under its centre, by
which it can be placed exactly over the station from whence
the observations are to be taken ; likewise, if required, two
extra eye-pieces for the telescope, to be used for astrono-
mical observations ; the one inverts the object, and has a
greater magnifying power, but having fewer glasses pos-
sesses more light ; the other is a diagonal eye-piece, which
will be found extremely convenient when observing an
object that has a considerable altitude ; the observer avoid-
ing the unpleasant and painful position he must assume in
order to look through the telescope when either of the
othei eye-pieces is applied. A small cap, containing a
dark-colored glass, is made to apply to the eye-end of the
telescope, to screen the eye of the observer from the inten-
sity of thtf sun's rays, when that is the object under observ-
ation. A magnifying glass, mounted in a horn frame, a
screw-driver, and a pin to turn the capstan-screws for the
adjustments, are also furnished with the instrument.

The V tamer. — This is a contrivance for measuring parts
of the space between the equidistant divisions of a graduat-
ed scale. It is a scale whose length is equal to a certain
number of parts of that to be subdivided, depending on
the degree of minuteness to which the subdivision is intend-
ed to be carried ; but it is divided into parts which in number
are one more or one less than those of the primary scale
taken for the length of the vernier : in modern practice, the
parts on the vernier are generally, one more than are con-
tained in the same space on the primary scale.

If it is required to measure to hundreclths of an inch, the
parts of a scale which is graduated to lOths. it may be done
by means of a scale whose length is nine tenths of an inch,
and divided into 10 equal parts ; or by one whose length is
eleven tenths of an inch, and divided into 10 equal parts ;
for in either case the difference between the divisions of the
scale so made and those on the primary scale is the hun-
dredth of an inch. Such a scale, made to move along the
edge of that to be subdivided, is called a vernier. By its
application, either to straight lines or arcs of circles, the
subdivisions of graduated instruments are read off.

The adjustments. — The first adjustment is that of the line

SURVEYING INSTRUMENTS. 85

of collimation ; that is, to make the intersection of the cross
wires coincide with the axis of the cylindrical rings on which
the telescope turns : it is known to be correct, when an eye
looking through a telescope observes their intersection con-
tinue on the same point of a distant object during an entire
revolution of the telescope. The usual method of making
this adjustment is as follows :

First, make the centre of the horizontal wire coincide
with some well-defined part of a distant object ; then turn
the telescope half round in its Y's till the level lies above
it, and observe if the same point is again cut by the centre
of the wire ; if not, move the wire one half the quantity of
deviation, by turning two of the screws at in (releasing one,
before tightening the other), and correct the other half by
elevating or depressing the telescope ; now if the coinci-
dence of the wire and object remains perfect in both positions
of the telescope, the line of collimation in altitude or depres-
sion is correct, but if not, the operation must be repeated
carefully, until the adjustment is satisfactory. A similar
proceeding will also put the vertical line correct, or rather
the point of intersection, when there are two oblique lines
instead of a vertical one.

The second adjustment is that which puts the level at-
tached to the telescope parallel to the rectified line of colli-
mation. The clips, ii, being open, and the vertical arc
clamped, bring the air-bubble of the level to the centre of
its glass tube, by turning the tangent-screw, P ; which done,
reverse the telescope in its Y's, that is, turn it end for end,
which must be done carefully, that it may not disturb the
vertical arc, and if the bubble resume its former situation in
the middle of the tube, all is right ; but if it retires to one
end, bring it back one half, by the screw/, which elevates
or depresses that end of the level, and the other half by
the tangent-screw, P ; this process must be repeated until
the adjustment is perfect ; but to make it completely so, the
level should be adjusted laterally, that it may remain in the
middle of the tube when inclined a little on either side from
its usual position immediately under the telescope, which is
effected by giving the level such an inclination, and if neces-
sary turning the two lateral screws at g ; if making the
latter adjustment derange the former, the whole operation
must be carefully repeated.
8

86 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

The third adjustment is that -which makes the azimuthal
axis, or axis of the horizontal limb, truly vertical.

Set the instrument as nearly level as can be done by the
eye, fasten the centre of the lower horizontal limb by the
staff-head clamp, H, leaving the upper limb at liberty, but
move it till the telescope is over two of the parallel plate-
screws ; then bring the bubble of the level under the tele-
scope, to the middle of the tube, by the screw P ; now turn
the upper limb half round, that is 180°, from its former po-
sition ; then, if the bubble returns to the middle, the limb is
horizontal in that direction ; but if otherwise, half the differ-
ence must be corrected by the parallel plate-screws over
which the telescope lies, and half, by elevating or depress-
ing the telescope, by turning the tangent-screw of the ver-
tical arc ; having done which, it only remains to turn the
upper limb forward or backward 90°, that the telescope
may lie over the other two parallel plate-screws, and by
their motion set it horizontal. Haying now levelled the
limb-plates by means of the telescope level, which is the
most sensible upon the instrument, the other air-bubbles
fixed upon the vernier-plate, may be brought to the middle
of their tubes, by merely giving motion to the screws which
fasten them in their places.

The vernier of the vertical arc may now be attended to ;
it is correct, if it points to zero when all the foregoing ad-
justments are perfect ; and any deviation in it is easily rec-
tified, by releasing the screws by which it is held, and tight-
ening them again after having made the adjustment ; or,
what is perhaps better, note the quantity of deviation as an
index error, and apply it, plus or minus, to each vertical
angle observed. This deviation is best determined by re-
peating the observation of an altitude or depression in the
reversed positions, both of the telescope and the vernier
plate : the two readings will have equal and opposite errors,
one half of their difference being the index error. Such a
method of observing angles is decidedly the best, since the
mean of any equal number of observations taken with the
telescope reversed in its Y's, must be free from the effects
of any error that may exist in the adjustment of the vernier,
or zero of altitude.

The theodolite, as constructed in the manner we have
described, is not inconveniently heavy, as the diameter of
the horizontal limb seldom exceeds five inches ; but when

SURVEYING INSTRUMENTS. 87

tLe diameter is increased, the other parts must be made
proportionably large and strong, and the instrument becomes
too weighty and cumbersome to be easily carried from station
to station. The object of increasing the dimensions, is to
enable the instrument to furnish more accurate results, by ap-
plying a telescope of greater power, and by a more minute
subdivision of the graduated arcs. With the increase of
size, a small variation takes place in the construction, prin-
cipally consisting in the addition of a second telescope, and
in the manner of attaching the supports, K and L, to the
horizontal limb, to afford the means of adjusting the hori-
zontal axis, and of course, making the telescope and vertical
arc move in a vertical plane. In the smaller instruments
this is done by construction, but in the larger ones, the sup-
ports, K and L, are attached to a stout frame, which also
carries the compass-box, instead of being fixed, as repre-
sented in our figure, to the upper horizontal -plate. The
frame is attached to the limb by three capstan-headed
screws forming an equilateral triangle, two of them lying
parallel to the horizontal axis, and the third in the direction
of the telescope ; the adjustment is made by means of these
screws. To prove its accuracy, set up the theodolite in such
a situation that some conspicuous point of an elevated
building may be seen through the telescope, both directly
and by reflection, from a basin of water, or, what is better,
of oil or quicksilver. Let the instrument be very correctly
levelled, and if, when a vertical motion is given to the tele-
scope, the cross-wires do not cut the object seen, both
directly and by reflection, it is a proof that the axis is not
horizontal ; and its correction is effected by giving motion to
the screws above spoken of, which are at right angles to the
telescope, or in the direction of the horizontal axis. The
third screw, or that which is under the telescope, serves for
adjusting the zero of altitude, or vernier of the vertical arc.
A second telescope is sometimes attached to the instru-
ment beneath the horizontal limb ; it admits of being moved,
both in a vertical and horizontal plane, and has a tangent-
screw attached for slow motion ; its use is to detect any
accidental derangement that may occur to the instrument
whilst observing, which may be done by it in the following
manner. After levelling the instrument, bisect some very
remote object with the cross-wires of this second telescope,
and clamp it firm ; if the instrument is steady, the bisection

88 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

will remain permanent whilst any number of angles are
measured, and by examining the bisection from time to time,
during the operation at the place where the instrument is
set up, any error arising from this cause may be detected
and rectified.

Price, 5 inch, brass arches, $100.00 to $120.00
" 5 " silver " $125.00
" 6 " " " $150.00
" Y " " " $250.00 to $300.00.

The Spirit Level (Fig. 100) con-
sists of a glass tube, nearly filled
with a liquid, spirits of wine being
now used, on account of its mobility, and not being liable
to freeze, the bubble of which, when the tube is placed
horizontally, would rest indifferently in any part, if the tube
could be made mathematically straight ; but that being im-
possible to execute, and every tube having some slight
curvature, if the convex side be placed upwards, the bubble
will occupy the higher part ; such a tube firmly fastened on
a straight bar, and marked at two points distant by the
length of the bubble, if so placed that the bubble shall
occupy this interval, has one definite relation to the horizon ;
for were it ever so little moved one way or other, the bubble
would shift its place, and run towards the elevated side.

The accuracy of the indications of the level depends in a
considerable degree on the regularity of the interior surface
of the tube. They are commonly made of glass tubes, in
the same state as they are obtained from the glass-house ;
but when very great accuracy is required, the inside is
ground, to give them a regular spherical curvature. The
larger the bubble, the more freely it moves. The spirit
level is extensively used in instruments for surveying, and
for astronomical and geological purposes ; the glass tube
being inclosed in a brass case, which is cut out on the upper
side, so that the bubble may be seen.

The Pocket Spirit Level. — (Fig. 101, next page.) — This cut
represents a brass pocket spirit level ; they are made from
three to twelve inches long, are mounted on a stout brass
plate, having the bottom ground true, and supported by a
small pillar at each end, on the upper part of which are
two nuts, between which the level is supported by projec-

SURVEYING INSTRUMENTS.

89

tions from the ends of the brass tube in which it is enclosed,
and thus affording facilities for accurate adjustment.

They are made sometimes with sights at each end, and
adapted to a staff, serving for conducting small parcels of
water, draining a field, &c.

The adjustment of these levels is very easily proved, or
made, by bringing the bubble in the middle, upon
any table, or base ; if upon reversion in the same
place precisely, the bubble keeps to the middle,
it is adjusted ; if not, turn one of the screws at
the end, till it be so raised or depressed as to
cause the bubble to stand the reversing, at the
same time altering the inclination of the plane on

which the level is tried.

Price, $2 to $6.

The Masons' or Carpenters' Level. — (Fig. 102.)
— This spirit level is mounted in a mahogany
stock, or frame, usually from Fig. 101. Fig. 102.
one to two feet long, but some-
times as small as three inches ;
the glass tube is sunk in the
wood, and cemented fast ; a
stout brass plate covering the
wood around, leaving a long
aperture through which to view
the bubble ; occasionally the
ends of the wood are capped
with stout brass, to prevent
wear.

They are made sometimes
with sights, for the purpose of
sighting through for levelling
long distances.

Price, 88cts. to $1.50.

The Level and Plumb. — (Fig.
103.) — This is made similar to
the last, with the addition of a
cross level, for which the stock
is made a little wider ; the cross
level is enclosed in a tube and
accurately fixed in the stock,
having a large circular or semi-

90

BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

circular hole for viewing the bubble ; when placed against
a wall, post, or the like, will indicate if it is plumb, or not.
This is a valuable instrument for masons, carpenters, mill-
wrights, &c., for setting their work perpendicular, with more
expedition than the plumb-bob and string.

Price, $2.00.

Common Surveying Level. — The annexed cut (Fig. 104)
is a representation of a spirit level of a plainer construction
than those that we shall describe, and though not having
the accuracy of the Y levels that are used by engineers, yet
will answer an ordinary purpose in the construction of
ditches, mill-seats, &c. The telescope is from twelve to
fourteen inches long, having adjusting tubes, and cross
hairs within, and is attached to a strong brass bar by screws
that have adjusting nuts ; the level is attached to the tele-
scope with the usual adjustments, and beneath the bar a
socket with a milled-head screw, for the purpose of firmly
mounting on the staff. Price, $12.00.

Fig. 104.

The T Spirit Level. — (Fig. 105,) on the following page,
represents this instrument; it has an achromatic telescope
mounted in Y's like those of the theodolite, and is furnished
with a similar system of cross wires for determining the axis
of the tube, or line of collimation. By turning the milled -
headed screw, A, on the side of the telescope, the internal
tube, a, will be thrust outwards, which carrying the object-
glass, it is by this means adjusted to its focal distance, so
as to show a distant object distinctly.

. The tube, c c, carrying the spirit-bubble, is fixed to the
under side of the telescope by a joint at one end, and a

SURVEYING INSTRUMENTS.
Fig. 105.

91

z

c

1

' f\ 0>

capstan-headed screw at the other, which sets it parallel to
the optical axis of the telescope ; at the opposite end is
another screw, e, to make it parallel in the direction side-
ways. One of the Y's is supported in a socket, and can be
raised or lowered by the screw B, to make the telescope
perpendicular to the vertical axis. Between the two sup-
ports is a compass-box, C, having a contrivance to throw
the magnetic needle off its centre when not in use ; it is
convenient for taking bearings, and is not necessarily con-
nected with the operations of levelling, but extends the use
of the instrument, making it a circumferentor. The whole
is mounted on parallel plates and three legs, the same as
the theodolite.

It is evident, from the nature of this instrument, that
three adjustments are necessary. First, to place the inter-
section of the wires in the telescope, so that it shall coincide
with the axis of the cylindrical rings on which the telescope
turns ; secondly, to render the level parallel to this axis ;
and lastly, to set the telescope perpendicular to the vertical
axis, that the level may preserve its position while the
instrument is turned quite round upon the staves.

To adjust the Line of Collimation. — The eye-piece being
drawn out to see the wires distinctly, direct the telescope to
any distant object, and by the screw, A, adjust to distinct

92 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

vision ;* bring the intersection of the cross wires to coincide
with some well-defined part of the object, then turn the
telescope round on its axis as it lies in the Y's, and observe
whether the coincidence remains perfect during its revolu-
tion; if it does, the adjustment is correct; if not, the wires
must be moved one -half the quantity of error, by turning
the little screws near the eye-end of the telescope, one of
which must be loosened before the opposite one is tightened,
which, if correctly done, Avill perfect this adjustment.

To set the Level parallel to the Line of Collimation. —
Move the telescope till it lies in the direction of two of the
parallel plate-screws, the clips which confine the telescope
in the Y's being laid open, and by giving motion to the
screws, bring the air-bubble to the middle of the tube,
shown by the two scratches on the glass. Now reverse the
telescope carefully in its Y's, that is, turn it end for end ;
and should the bubble not return to the centre of the level
as before, it shows that it is not parallel to the optical axis,
and requires correcting. The end to which the bubble
retires must be noticed, and the bubble made to return one-
half the distance by the parallel plate-screws, and the other
half by the capstan-headed screw at the end of the level,
when, if the halves have been correctly estimated, the air
bubble will settle in the middle in both positions of the tele-
scope. This and the adjustment for the coilimation gene-
rally require repeated trials before they are completed, on
account of the difficulty in estimating exactly half the
quantity of deviation.

To set the Telescope perpendicular to the Vertical Axis. —
Place the telescope over two of the parallel plate-screws,
and move them, unscrewing one while screwing up the
other, until the air-bubble of the level settles in the middle
of its tube ; then turn the instrument half round upon the
vertical axis, so that the contrary ends of the telescope may
be over the same two screws, and if the bubble again settles
in the middle, all is right in that position ; if not, half the

* The eye-piece must first be drawn out until the cross wires are
perfectly well defined, then the object-glass moved till distinct
vision is obtained without parallax, which will be the case, if, on
looking through the telescope at some distant object, and moving the
eye sideways before the eye-glass, the object and the wires remain
steadily in contact; but it' the wires have any parallax, the object
will appear flitting to and from them.

SURVEYING INSTRUMENTS. 03

error must be corrected by turning the screw, B, and the
other half by the two parallel plate-screws over which the
telescope is placed. Next turn the telescope a quarter
round, that it may lie over the other two screws, and make
it level by moving them, and the adjustment will be
complete.

Before making observations with this instrument, the
adjustments should be carefully examined and rectified,
after which the screw, B, should never be touched ; the
parallel plate-screws alone must be used for setting the
instrument level at each station, and this is done by placing
the telescope over each pair alternately, and moving them
until the air-bubble settles in the middle. This must be
repeated till the telescope can be moved quite round upon
the staff-head, without any material change taking place in
the bubble.

A short tube, adapted to the object-end of the telescope,
will occasionally be found useful in protecting the glass
from the intensity of the sun's rays, and from damp in wet
weather. Price, $80 and $100.

Troughtons Level— (Fig. 106.)— The telescope, A B,
rests upon the horizontal bar, a b, which turns upon the
staff-head (similar to the one employed in the Y level and
the theodolite). On the top of the telescope, and partly
imbedded within its tube, is the spirit-level, c d, over which
is supported the compass-box, C, by four small pillars ; thus
admitting the telescope to be placed so close to the horizon-
tal bar, a b, that it is much more firm than in the former
instrument. The bubble of the level is sufficiently long for
its ends to appear on both sides of the compass-box ; and
it is shown to be in the middle by its coinciding with scratches
made on the glass tube as usual.

The wire plate (or diaphragm) is generally furnished with
three threads, two of them vertical, between which the*
station-staff may be seen ; and the third, by which the ob-
servation is made, is placed horizontally.

The telescope is generally constructed to show objects
Inverted ; and as such a telescope requires fewer glasses than
jne which shows objects erect, it has the advantage in point
jf brilliancy ; and when an observer is accustomed to it, the
apparent inversion will make no difference to him. A diago-
nal eye-piece, however, generally accompanies the instru-

04 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 106.

ment, and by it objects can be seen in their natural position.
A cap is adapted to the object-end of the telescope, to
screen the glass from the rays of the sun, or from the rain :
when the cap is used, it should be drawn forwards as much
as possible.

* The requisite adjustments for this instrument are the
same as those of the Y level ; viz. that the line of collima-
tion and the level be parallel to each other, and that the
telescope be exactly perpendicular to the vertical axis ; or
in other words, that the spirit bubble preserve its position
while it is turned round horizontally on the staff-head. The
adjustment of the level is effected by correcting half the
observed error by the capstan-screws, e, f, which attach the
telescope to the horizontal bar, and the other half by the

SURVEYING INSTRUMENTS. 95

parallel plate-screws : the capstan-screws, e, f, have brass
covers to defend them from injury or accidental disturbance,
but admit their adjustment when necessary.

The spirit level itself has no adjustment, being firmly
fixed in its cell by the maker, and therefore the line of col-
limation must be adjusted to it, by means of two screws,
near the eye-end of the telescope ; the manner of doing this
is as follows : — Set up the instrument on some tolerably level
spot of ground, and, after levelling the telescope by the
parallel plate-screws, direct it to a staff held by an assistant
at some distance (from ten to twenty chains) ; direct him by
signals to raise or depress the vane, until its wire coincides
with the horizontal wire of the telescope (or central division
of the micrometer scale): now measure the height of the
centre of the telescope above the ground, and also note the
height of the vane on the staff; let, for example, the former
be four feet and the latter six, their difference shows that
the ground over which the instrument stood is two feet
higher than where the staff is placed. Next make the
instrument and staff change places, and observe in the same
manner as before, and if it gives the same difference of level,
the instrument is correct ; if otherwise, take half the differ-
ence between the results, and elevate or depress the vane
that quantity, according as the last observation gives a
greater or less difference than the first. Again, direct the
telescope to the staff, and make the coincidence of the hori-
zontal wire and that on the vane perfect, by turning the
collimation screws. Price, $100.

Levelling Staves. — (Fig. 107.) — A mahogany Fi°- 107-
rod, about 12 feet long, and two inches wide,
is divided into feet and hundredths. A target
of brass, about 8 inches square, or round,
slides on the rod, by means of a brass box, on
the back, having a spring to give ease and
regularity to the movement ; on the face of the
target is an aperture, over the divisions of the
rod, having a vernier, which reads to thousands
of a foot. The face is varnished in sectors of
different colors, as white and black, affording
a very distinct dividing line to the observer.
A stout cord is fastened to the upper part of
this box, on one side, and is carried around the whole length

96 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

of the rod, passing through pulleys in the ends, and is at-
tached to the lower part of the box. By means of this cord
the target may be moved up or down, when out of the
reach of the vane man. Price, $5.00 to $8.00 each.

Portable Levelling Staves. — Two mahogany station-staves
generally accompany the spirit-level ; they consist of two
parts, capable of being drawn out when considerable length
is required. They are divided into feet and hundredths, or
feet, inches, and tenths, and have a sliding-vane, with a wire
placed across a square hole in the centre, as shown in
Fig. 107 : this vane being raised or lowered by the as-
sistant, until the cross-wire corresponds with the horizontal
wire of the telescope, the height of the wire in the vane,
noted on the staff, is the height of the apparent level above
the ground at that place.

When both the staves are used, they should be set up at
equal distances on each side of the spirit level : the difference
of the heights of their vanes will be the absolute difference
of level between the two stations. But when one staff only
is employed, the difference between the height of the vane
and the height of the centre of the telescope of the instru-
ment, will be the apparent difference of level, which, if the
distance between the staff and instrument is great, requires
to be corrected for the curvature of the earth.

Price, $5.00 to $8.00 each.

>• 108< Angle Meter, or Level

for Slopes. — (Fig. 108.) —
This level, used for mea-
suring the angle of strata
in mines, geological form-
ations, and any inclination
or slope, consists of a stout
brass plate, about 6 inches
long, jointed at one end
to another plate, having a
level at the side, and hav-
ing a graduated arc at-
tached to the lower plate,
and moving in a slide on the back of the level plate, and also
jointed for portability. In use the lower plate is placed on
the slope, and the jointed plate moved till the bubble of the

SURVEYING INSTRUMENTS.

97

level stands in the middle of the opening, the angle being
shown on the divided arc.

Price, $6.00 and $8.00.

Dipping Needle.— The Fig. 109.

dipping needle (Fig. 109)
is usually a flat oblong
piece of steel, about 6 in.
long, accurately centred,
and balanced previous to
being magnetized, and
having a slender cylin-
drical axis, fixed at right
angles through its centre,
and moving freely on its
supports. The mounting
consists of a brass plate,
supported by three screws.
In the centre of this brass
plate is another, concen-
tric with the former, and
movable round a centre-
pin, like the movable plate
of a theodolite. To this
plate are attached two levels, the one placed at right an-

fles to the other, and used to adjust the plate horizontally,
'our pieces of brass support the circular case of the dipping
needle, the two faces of which are of plate glass, within
which two straight bars of brass are firmly fixed across in n
horizontal direction; other two brass pieces are fixed b\
screws to the centre of the bars, and carry two finely polished
planes of agate, on which the axis of the needle rests, and
upon which it turns with very little friction. There is a
contrivance inside the box, connected with a small knob
outside, by which the observer can lift, by means of Y's,
the needle from the agate plates, or lower it upon them at
pleasure ; the Y's being carefully adjusted so as always to
leave the axis of the needle on the same part of the agate
planes, and in the centre of the graduated circle, and from
which graduated circle, the angle the needle makes with
the horizon is indicated ; this circle is usually divided to
half or quarter degrees, and there is sometimes a vernier
attached to the end of the needle, and also a reading micro-

9

98

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

scope attached to the rim of the glass face, movable so as
to be easily placed on any part of it, for the purpose of
reading off the dip with greater accuracy.

To use the instrument, set the graduated rim in the plane
of the magnetic meridian by means of a common compass,
levelling it by means of the screws of the stand.

Price, $40.00 to $50.00.

The Goniometer.— (Fig.
110.) — An instrument for
measuring ano-les, and more

£3 & "

particularly the angles form-
ed by the faces of crystals.
The common goniometer
consists of a pair of steel
blades moving on a centre,
as shown in the cut ; the
edges, a a, are carefully ad-
justed to the faces of the
crystal, whose inclination to each other it is required to as-
certain; and then the instrument being applied to the
divided semicircle, the angle contained is at once read off.
An approximate measurement, within one or two degrees,
can be easily obtained by this instrument, provided the planes
of the crystal be tolerably perfect, and large enough for the
purpose. Price, $3.00 to $5.00.

Fig. in. Wollastoii's Reflecting Goniometer. —

(Fig. 111.) — The reflecting goniometer
is a very superior instrument, its indica-
tions being correct within the fraction of
a degree ; it is applicable also to the
measurement of the angles of crystals
of very small size, the only conditions
required, being, that their planes be
smooth and brilliant. It consists of a
brass circle, A, graduated on the edge,
and furnished with a vernier, E, by which
the divisions may be read accurately to minutes. The circle
moves in a vertical plane, and is supported on a stand. The
axis of the circle is a hollow tube, within which is a smaller
axis, fitting so tightly that when turned round it carries the
other axis, and consequently the wheel, along with it, unless

SURVEYING IXSTIIUMENTS. 99

the latter is purposely prevented from moving. The interior
axis is furnished with a milled-head, c, and the exterior with
a milled-head, B, also ; so that when the head, c, is held
and the other turned, the circle may be moved independent-
ly of the smaller axis ; and when the outer one, B, is held,
and the inner one, c, turned, the smaller axis may be turned
independently of the circle. Attached to the end of the
smaller axis is a sort of universal joint, D, capable of being
fixed in different positions. The crystal to be examined is
attached to the joint at F, by a little soft wax, and placed
so that its edge shall be parallel to the axis of motion ;
which adjustment is obtained by placing it so that the image
of some horizontal object, as the bar of a window, succes-
sively reflected from the two faces of the crystal, coincides
with another horizontal line seen by direct vision. When
this adjustment has been made, the instrument is turned till
the horizontal object is seen reflected from one of the faces.
The smaller axis is then held fast, and the other turned till
the index of the vernier points to the zero of the graduated
limb. The circle is then turned round, along with the
smaller axis, till the same object is seen in the same position,
by reflection from the other face of the crystal ; when the
arc passed through by the circle is obviously the supplement
of the angle formed by the two faces of the crystal. In
order, however, to avoid calculation, the supplements of the
angles are marked on the limb, so that the angle to be
measured is read off immediately. Price, $20.00.

The Artificial Horizon. — When the altitude of a celestial
object is to be taken at sea, the observer has the natural,
or sea horizon, as a line of departure ; but on shore, he is
obliged to have recourse to an artificial one, to which his
observations may be referred : this consists of a reflecting
plane, parallel to the natural horizon, on which the rays of
the sun or other objects falling, are reflected back to an eye
placed in a proper position to receive them ; the angle
between the real object and its reflected image being then
measured with the sextant, is double the altitude of the
object above the horizontal plane.

Various natural, as well as artificial, reflecting surfaces
have been made by mechanical arrangements, to afford the
means of obtaining double angles ; such as pouring water,
oil, treacle, or other fluid substances into a shallow vessel ;

100

BENJ. PIKK'b, JR., DESCRIPTIVE CATALOGUE.

and to prevent the wind giving a tremulous motion to its
surface, a piece of thin gauze, talc, or plate-glass, whose
surfaces are perfectly plane and parallel, may be placed
over it, when used for observation. But the most accurate
kind of artificial horizon is that in which fluid quicksilver
forms the reflecting surface, the containing vessel being
placed on a solid basis, and protected from the influence of
the wind. The adjoining figure (No. 112) represents an
instrument of this kind. The mercury
is contained in an oblong wooden trough,
placed under the roof A, in which are
fixed two plates of glass, whose surfaces
are plane and parallel to each other.
This roof effectually screens the surface
of the metal from being agitated by the wind, and when it
has its position reversed at a second observation, any error
occasioned by undue refraction at either plate of glass will
be corrected. Price, $20.00 and $25.00.

Fig. 112.

Fig. 113.

Another and more portable contrivance
for an artificial horizon, is represented in
the annexed figures, which consists of a
circular plate of black glass, about two
inches diameter, mounted on a brass
stand, half an inch deep, with three foot
screws, a b c, to set the plane horizontal ;
the horizontally being determined thus
by the aid of a short spirit-level, d, hav-
ing under the tube a face ground plane,
on which it lies in contact with the re-
flecting surface ; place the level on the
glass, in a direction parallel to the line
joining two of the three foot-screws, as
a and b, then move one of these screws
till the bubble remains in the middle of
the tube, in both the reversed positions
of the level, and the plate will be hori-
zontal in that direction ; then place the
level at right angles to its former posi-
tion, and turn the third foot-screw back
or forwards till the bubble again settles
in the middle of its tube, the former

SURVEYING INSTRUMENTS. 101

levelling remaining undisturbed, and the plane will then be
horizontal. Price, $6.00 to $10.00.

When an artificial horizon is used, the observer must
place himself at such a distance that he may see the re-
flected object as well as the real one; then, having the
sextant properly adjusted, the upper or lower limb of the
sun's image supposing (that the object) reflected from the
index-glass, must be brought into contact with the opposite
limb of the image reflected from the artificial horizon, ob-
serving that when the inverting telescope is used, the upper
limb will appear as the lower, and vice versa; the angle
shown on the instrument, when corrected for the index-
error, will be double the altitude of the sun's limb above
the horizontal plane ; to the half of which, if the semi-
diameter, refraction, and parallax be applied, the result
will be the true altitude of the centre.

9*

ASTRONOMICAL INSTRUMENTS,

GLOBES.

Eighteen inch Globes of the Society for the Diffusion of
Useful Knowledge. — (Fig. 115, next page.) — In these globes
an endeavor has been made to combine a degree of accu-
racy, such as is only possessed by the best modern maps,
with the lowest price at which excellence can be attained.
The terrestrial globe has been compiled from the most recent
geographical surveys, with the aid of the accounts given by
the best travellers; and there is annexed on the 18-inch
globe a table of the population of the different countries in
the world, compiled from the latest official returns, and,
where these are wanting, the best authorities which could
be obtained by Mr. G. 8. Brent, Fellow of the Statistical
Society of London.

The astronomical information which has been supplied
of late years upon the position and nomenclature of the
fixed stars, has rendered a perfectly new celestial globe a
most desirable acquisition to the student of astronomy.
The labors of Piazzi, Bradley, Lacaille, Johnson, &c., in de-
termining the places of the stars, and those of Baily in the
correction of their nomenclature (in the new edition of the
" British Catalogue"), have been carefully consulted in the
celestial globe which is now advertised. The stars in the
northern hemisphere are all which are given by Piazzi, with
the addition of such of Bradley 's (from the Tabulae Regio-
montanae) as are not in Piazzi. The stars in the southern
hemisphere comprise all those given by Lacaille and Johnson.
The magnitude of each star is that by which it is designated
in the catalogue from which its place is taken : and the
several orders of magnitude are so distinguished from each
other as to be read, after a little practice, without the ne-

ASTRONOMICAL INSTRUMENTS.

103

cessity of counting the number of points in the star-figure.
The double and multiple stars have been marked from the
catalogues of Sir W. Herschel and Sturve, and Flamsteed's
numbers have been annexed as they stand in Mr. Baily's

104 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

edition of the " British Catalogue ; " which work has also
been followed in the omission of all letters except those
which are found in Bayer's maps. All the positions have
been brought up to 1850.

The figures of the constellations are printed from different
plates and in a distinct color from that of the more import-
ant parts.

Price, on high mahogany frames, the pair, $78.00.
" " " " " and com-

passes, the pair, - $85.00.

Thirteen-inch Globes. — The artificial globe is a round body
or sphere, having on its surface a map of the earth, or of
the celestial constellations, as delineated, with the principal
circles of the sphere. In the former case it is called the
terrestrial — in the latter, the celestial globe. — (See Figs. 116,
opposite page.) — Artificial globes are used for the purpose of
conveying to young persons the first ideas of the figure and
rotation of the earth, of latitude and longitude, and the
situation of places with respect to each other, and to the
sun at the different seasons of the year. It is usual to
employ them also for the purpose of solving mechanically a
few elementary problems of astronomy, relative to the dif-
ference of the hour of the day at different places ; the
times of the rising and setting of the sun ; the limits of the
visibility of eclipses, etc.

The fundamental parts of these instruments which are
common to both, are, first, the two poles whereon the
globe is supported, representing those of the world; second,
the brazen meridian, which is divided into degrees, and
passes through the poles ; third, the wooden horizon,
whose upper side represents the real horizon, and is divided
into several circles ; fourth, a brass quadrant of altitude ;
fifth, two hour circles, one moving round each pole as a
centre, and divided into twice twelve hours, to indicate
those of the day and night. The best globes have also a
magnetic compass attached to the frame. Upon the surface
of the globes are depicted the lines of latitude and longi-
tude, the equator, ecliptic, tropics, and polar circles. On
one globe, in addition to these, are the various countries,
seas, etc., of the world ; and on the other, the stars in their
relative positions.

ASTRONOMICAL INSTRUMENTS.
Figs 116.

105

Price, the pair,

825.00.

with high mahogany frames, $35.00.

and compasses,
10 inch, -

106 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 117. Fig. 118.

Fig. 119.

Globes with Inclined Axis, on neat Mahogany Bases. — (See
Fig. 117, as above.)

9 in. globes, terrestrial and celestial, the pair, $15.00.

6 in. globes, terrestrial and celestial, the pair, $ 7.50.

3 in. globes, terrestrial and celestial, the pair, $ 3.50.

5 in. globes, terrestrial and celestial, the pair, $ 2.50.

5 in. terrestrial globe, - $ 1.25.

3 in. terrestrial globe, - $ 0.75.

5 in. terrestrial globe, with moon attached, - $ 2.00.

Small Globes, with Brass Meridian and Horizon. — (Fig.
118, as above.)

5 in. terrestrial globe, - $ 1.50.

3 in. terrestrial globe, - $ 1.00.

Altitude or Globe Quadrant (Fig. 119, as above,) consists
of a thin, flexible strip of brass, movable at one end, around
a joint in the lower part of a square head, which is furnished
with a tangent screw. Its use is, that when fastened on to
the brazen meridian of an artificial globe, it shall indicate
the relative position of places, and other purposes connected
with that part of geography commonly called the use of
the globes. The strip of brass is graduated from zero to
90°, and the size of the instrument must be accordant to the
size of the globe with which it is to be used.

Price, 12 in. or 13 in., $1.25.
" 18 in., - - $2.00.

ASTRONOMICAL INSTRUMENTS. 107

The Armillary Sphere.— (Figs. 120 and 121, page 109.)
— Of the instruments contrived to elucidate the elements of
astronomy, none imprint so clearly on the mind the nature
and use of those circles which astronomers have supposed
to be applied to the concave sphere of the heavens, as the
armillary sphere.

If the circumference of a circle be turned about its diame-
ter as an axis, it will generate in its motion the surface of a
globe or sphere.

And the centre of the circle will be the centre of the globe.

All straight lines reaching from the centre of a globe to
its surface are equal.

Every straight line that goes through the centre of a
sphere, and is terminated at both ends by the surface, is a
diameter.

The diameter about which any sphere turns is its axis.

The extremities of such diameter or axis are its poles.

On the surface of a globe or sphere several circles may
be described ; those circles, whose centre is the same with
the centre of the globe, are called by way of distinction
great circles ; these divide the sphere into two equal parts.
The angular distance of two points situated on the surface
of the sphere, is measured by the arc of a great circle
intercepted between them.

Lesser circles divide the sphere into two unequal parts.

The sphere before you, by its real circles, serves to re-
present, and will enable me to explain to you those imagina-
ry circles by which astronomers divide the heavens into the
same parts or portions as you see these circles divide the
sphere. If your eye could be placed in the centre of this
sphere, you would see its circles upon or against those very
points of the heavens where the imaginary circles of the
astronomers are supposed to be situate. It is called armil-
lary, because it consists of a number of rings of brass, called
by the Latins armillse, from their resembling bracelets or
rings for the arms.

There are six great circles of the sphere : the horizon,
the meridian, the equator, the ecliptic, the equinoctial colure,
and the solstitial colure.

The sphere is sustained in a frame, on the top of which
is a broad circle representing the horizon, which represents
that imaginary circle which bounds or terminates the view
of the spectator, dividing the sphere into two equal parts ;

108 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

that which is above the horizon is called the upper or visible
hemisphere ; that which is below, the lower or invisible
hemisphere. When the sun, moon, or stars, descend below
this circle, we say they are set ; on the contrary, when they
appear above it, we say they have risen.

On the broad circle, representing the horizon, are marked
the thirty-two points of the mariner's compass ; the east,
west, north, and south points, are principally to be regard-
ed ; these are called cardinal points.

On the inside of the horizon are two notches for receiving
a strong brass circle representing the meridian.

It is suspended on two pins, at two opposite points of
the meridian ; these pins are a continuation of the axis of
the sphere both ways, and as the sphere turns round upon
them, they are considered as poles, and are called, one the
north, the other the south pole.

The equator is that circle which goes round the sphere
exactly in the middle between the two poles.

The ecliptic is that circle which crosses the equator ob-
liquely ; it is divided into twelve parts, each of which consists
of thirty degrees.

The equinoctial colure is the great circle which passes
through those two points of the equator that are intersected
by the ecliptic.

The solstitial colure is the other great circle at right
angles to the equator.

There are four lesser circles of the sphere, two tropics,
and two polar circles ; these four circles are all parallel to
the equator.

The tropic of Cancer is the parallel which is on the north
side of the equator, and 23^ degrees distant therefrom.

The tropic of Capricorn is situate on the south side of the
equator, and also 23£ degrees distant therefrom.

The two polar circles are at the same distance from the
two poles that the tropics are from the equator, that is,
twenty-three degrees and a half.

That towards the north pole is called the arctic circle,
that towards the south pole, the antarctic circle.

The point in the heavens which is directly over the head
of the spectator, is called the zenith. The point which is
directly under his feet, is called the nadir.

To rectify the Sphere, elevate the pole till the same num-
ber of degrees is above the plane of the horizon, as the pole

ASTRONOMICAL INSTRUMENTS.

no

10

110 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

of the place you are considering is above the horizon, and
then the circles on the sphere will, with respect to the globe
within it, correspond with the imaginary circles of astrono-
mers in the heavens.

The Hour Circle is a small circle fixed about the north
pole, with a hand on the axis of the sphere, so that by turn-
ing the sphere on its axis the index will be carried round the
circle.

This circle is used to convert the degrees of the equator
into time ; it is divided into twenty-four equal parts, answer-
ing to twenty-four hours, or the time of an entire revolution
of the heavens. The index, by pointing successively to those
hours, shows in what space of time any part of that revolu-
tion is performed.

The Quadrant of Altitude. — This is a long slip of brass
with a nut at top to fix it to the meridian ; it is divided into
ninety degrees, and being fixed at the zenith it reaches to
the horizon ; it may be carried to any part of the sphere,
and thus will show the height or altitude of any point above
the horizon in any position of the sphere.

Price, best 13 inch diameter, $40.00.

" plain, $20.00 and $25.00.

" common fig., 9 inch, $ 4.00.

" 12 " $ 5.00.

Planetarium. — (Fig. 122, next page.) — A planetarium
may be considered in some sort as a diametrical section of
our universe, in which the upper and lower hemispheres are
suppressed.

The upper plate is to answer for the ecliptic ; on this are
placed, in two opposite but corresponding circles, the days
of the month, and the signs of the ecliptic, with their res-
pective characters ; by this plate you may set the planetary
balls so as to be in their respective places in the ecliptic, for
any day in the year.

Through the centre of this plate, you observe a strong
stem, on which is a brass ball to represent the sun ; round
the stem are different sockets to carry the arms, by which
the several planets are supported. The planets are repre-
sented by white or gilt balls. We can with ease either take
off, or put on, any of the planets, as occasion may require.
About the primary planets are placed the secondary planets

ASTRONOMICAL INSTRUMENTS.
Fig. 122.

Ill

or moons, which are in these instruments only movable by
the hand.

We turn the handle, and all the planets are put in motion,
moving round that ball which represents the sun. Now, if
you take the earth's motion as a standard, they move with
nearly the same relative velocities and periodical times that
they observe in the heavens. We scarcely need observe,
that it is impossible to give an idea of the proportion and
distances of the planets in the compass of an instrument so
small as that before you, or indeed of any instrument what-
soever.

112 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

The motions are carried on by a train of wheel- work con-
cealed in the brass box, under the ecliptic.

In the centre of the system is the sun, placed in the
heavens by that Almighty Power, who said, "Let there be
light, and there was light," to be the fountain of light and
heat to all the planets revolving round him.

The nearest planet to the sun is Mercury ; observe the
part of the ecliptic he is at, and also the place where the
earth is situate. I now turn the handle, Mercury is arrived
at the place from whence he set out, and our earth has gone
over 88 days of the ecliptic ; the velocity we here give the
planet is inconsiderable, but in his course in the heavens he
is supposed to move with a velocity equal to 100,000 miles
in an hour.

Venus is the next planet in the system ; in the heavens
she is distinguished by the superiority of her lustre, appear-
ing to us the brightest and largest of all the planets. By
observing her course through the ecliptic, and comparing it
with the days passed over by the earth in the same time,
you will find, in the instrument, Venus revolving round the
sun in 225 days ; in the heavens she moves at the rate of
80,955 miles in an hour.

The third planet in the solar system is the Earth ; dimi-
nutive as it appears before you in this instrument, its real
diameter is near 8000 miles ; it revolves round the sun in
the space of 365 days, into which number the brazen eclip-
tic is divided ; this revolution constitutes our year, while its
revolution round its axis forms day and night.

The little ball, close and annexed to the earth, represents
the Moon.

The planet Mars is the next in order, being the first
above the earth's orbit ; he revolves round the sun in about
686 days ; so that our earth, as you will observe by the
instrument, goes nearly twice round, while he is performing
his revolution; he is supposed to move at the rate of 55,783
miles in an hour. To this planet our earth and moon will
appear like two moons, sometimes half or three quarters
illuminated, but never full.

Jupiter, the largest of all the planets, is next beyond
Mars ; and our earth must have gone nearly twelve times
round the ecliptic for one revolution of Jupiter ; yet so far
is its path removed from the sun, that to go round it in
this space of time, it moves at the rate of 30,193 miles an

ASTRONOMICAL INSTRUMENTS. HJJ

hour. It is attended by four satellites, represented by four
balls ; they are invisible to the naked eye, but appear beau-
tiful through a telescope.

Saturn, the next planet, is still higher in the system,
performing its circuit in about thirty years of our time ; it
moves at the rate of 22,298 miles an hour ; it is accompa-
nied by seven satellites, and a large luminous ring.

Greorgium Sidus, or Herschel. is the seventh planet in our
system ; it is nearly twice the distance of Saturn from the
sun, round which it revolves in about 90 years ; its diame-
ter is 34,1 70 miles, and it is accompanied by six satellites.

Price, $50.

Fig. 123.

Improved Planetarium. — (Fig. 123, as above.) — This in-
strument has received the entire approbation of teachers,
and others, who have used it, and has been adopted in
most of our academies and schools. It is substantially made,
the planets moving by a crank and wheel-work within the
box, on the top of which is an engraved plate representing
the signs of the zodiac, &c., and the whole as useful an
instrument as the more costly one preceding.

Price, with brass stand, $15.00.

" with mahogany stand, $ 7.50.

The Common Orrery. — (Fig. 124.) — The following shows
one of these instruments of a simple form : — It consists of a
table, upon the top of which are delineated the signs of the
zodiac, points of the compass, days of the month, and
months of the year. In the centre is a strong wire or brass
10*

114 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fi-. 12 1.

rod, terminated by a brass ball to represent the sun. On
this rod are several rings, each bearing a long wire, turned
up near the end. These have balls of various sizes at their
points, representing the planets of our system, with such
moons as naturally belong to them. The length of the
wires and size of the balls cannot be made accordant with
the real size of the planets and their orbits, on account of
the very great extent of space which would be required.
The planets are seen in their natural order of Mercury,
Venus, the Earth and moon, Mars, Jupiter and four moons,
and Saturn with seven moons. Herschel is for want of space
omitted. Price, $5.00.

The Tellurium. — The sun, the earth, and the moon, are
bodies, which, from our connexion with them, are so inter-
esting to us that the annexed instrument has been contrived
expressly for their elucidation. This instrument (Fig. 125)

Fig. 125.

ASTRONOMICAL INSTRUMENTS. 115

shows in an accurate and clear manner the phenomena
arising from the annual and diurnal motion of the earth ; the
change of the seasons ; the revolution of the moon round
the earth, moving in an orbit inclined to that of the ecliptic,
and illustrating the subject of eclipses. The gilt ball repre-
senting the sun can be taken off, and a lamp substituted in
its place, illuminating the earth in one hemisphere only, and
the moon differently in its various positions. There are
four distinct motions given to this instrument, three by
means of wheels with cords passing round them, and one
with toothed wheels, also a screw at the end to tighten the
cords when required ; the globe is three inches in diameter,
and all the continents, seas, etc., may be distinctly seen ;
the equator, the ecliptic, tropics, and other circles, are very
visible, so that problems, relative to particular places, may
be satisfactorily solved ; the axis of the earth is inclined to
the ecliptic in an angle of 66^ degrees, and preserves its
parallelism during the whole of its revolution ; when the
north pole is turned directly towards the sun, the globe is
in the position of the earth for the longest day in our
northern hemisphere, or the 21st of June ; turn the handle
of the instrument till the earth and moon have revolved
half round the sun, and the north pole is directed from the
sun, and we have the shortest day, or the 21st of December;
there are two intermediate positions in the revolution of the
globe, answering to the positions on the 21st March and the
21st of September, when the two poles are equally exposed
to the sun, and when the days and nights are of a length
all over the earth. The phases of the moon are clearly ex-
hibited by this instrument. When the moon is between the
earth and the sun, we call it new moon, the enlightened
part being then turned from us ; but when the earth is be-
tween the sun and moon, we call it full moon, the enlight-
ened part being then turned towards us; in the intermediate
positions we have the first and last quarter of the moon.
Price, on brass stand, $13.50.

" on mahogany stand, $7.00.

Eclipse Instrument. — (Fig. 126, next page.) — This instru-
ment consists of a painted ball of four inches in diameter,
representing the sun, mounted on a mahogany base twenty
inches long ; there is supported from each end a two inch
terrestrial globe ; to the axis of one of these is supported a

116

Fig. 126.

ball, representing the moon, which is movable nearly around
the globe ; brass wires proceed from the sun, representing
the rays of the sun's light falling on the side of the earth
turned towards the sun. From this end of the instrument
various eclipses may be shown. From the other side of the
sun there is a ball representing the moon, by which the
earth is eclipsed, and wires representing rays from the sun,
for explaining the shadows called penumbra and umbra,
and is a valuable instrument in explaining both solar and
lunar eclipses. Price, 85.00.

The Tide Dial. — (Fig. 127, next page.) — This instrument
consists of a circular piece of wood, on which there is re-
presented a dial having the twenty-four hours of the day ;
connected at the centre, to an axis, is a movable disk repre-
senting the ocean, and bearing an arm having a ball attached
to the end, representing the moon ; the water appearing at
high tide in that direction ; the outer disk representing the
earth. On the back of the dial is a crank, giving motion to
the wheel-work, and causing the earth and moon to revolve ;
the earth revolving twenty-nine times faster than the moon.

The tides are occasioned by the ebbing and flowing of the
sea, which are caused by the attraction of the sun and
moon, but chiefly by the latter.

The attraction causes the water to assume a spheroidal
figure, the longest axis being in the direction of the moon.

This oval of the waters keeps pace with the moon in its
monthly course round the earth ; while the earth, by its
daily rotation on its axis, presents each part of its surface to
the direct action of the moon, twice every day, and thus
produces two flood and two ebb tides. But because the
moon is in the mean time passing from east to west in its
orbit, it comes to the meridian of any place later than it
did the preceding day ; consequently the two floods and
ebbs require nearly twenty-five hours to complete them.

The tides are greatest at the new and full moons, and are

ASTRONOMICAL INSTRUMENTS.
Fig. 127.

117

thence called spring tides, and least at the first and last
quadratures, and are thence called neap tides, and the highest
tides are near the time of the equinoxes. Price, $4.00.

Centrifugal Hoops for showing the Earth an Oblate Sphe-
roid.— (Fig. 128, next page.) — An astronomical instrument,
to show that the earth, if revolving at all, must revolve
upon its shortest axis, and that owing to centrifugal force.

118 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 129.

The structure of the instrument is very simple : it consists
of two or more hoops of thin tin, or brass. These are
fastened below to a spindle, so that they must turn with it,
but move easily up and down that spindle when put in mo-
tion. The spindle has a pulley below, and is supported at
top by a cross arm. The pulley is turned by a string pass-
ing over a multiplying wheel. Upon turning this wheel, the
hoops being put in motion will endeavor to fly out by cen-
trifugal force, and assume the shape represented by the
dotted line ; that is, will become an oblate spheroid, or a
globular body flattened towards either pole.

Price, $4.50.

Fig. 129, as above, represents a cheaper construction of
this instrument, having a three inch globe in the centre.
The motion is given by turning it rapidly with the finger.

Price, $2.50.

Astronomic Telescope on Brass Stand. — No invention in
the mechanic arts has ever proved more useful and enter-
taining than the production of the telescope ; its utility,
both by sea and land, is well known ; in respect to the
heavenly bodies, much of our knowledge is due to the
invention of the telescope.

ASTRONOMICAL INSTRUMENTS.
Fig. 130.

11')

The Astronomical Telescope (Fig. 130, as above) consists
of an object and eye-glass fitted into a long brass tube.
The object-glass is placed at the end of the tube nearest
the object. The eye-glass is that which is nearest the
eye ; and when there are more lenses than one in the tube,
besides the object-glass, they are called eye-glasses also.
The tube is mounted on a brass stand having a joint and
swivel at the top, by which the telescope may be directed
to any position in the heavens.

The short tube, C, adjusts in or out the body of the tele-
scope, by a rack and pinion, worked at A ; to the end of
which, the eye-tube, B, and the various powers are applied.

The eye-tube, B, contains four glasses. To increase the
power, unscrew the eye-head of this tube, b, and take out

TJO BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

the sliding pipe, which contains the two first glasses, and in
its place substitute the higher power, 2. Observe, the
highest power, 1, is screwed into the adjusting tube, C,
without the long eye-tube, and is preferred for astronomical
uses.

The legs of the brass stand are jointed and fold together,
and the whole instrument neatly packed in a mahogany
case.

Price, the main tube 20 inches long, $42.00.

" 30 " 60.00.

" " " 36 " 90.00.

" 42 " 150.00 and $200.

" 30 inch, without box and ast. eye-piece, 48.00.

Astronomical Telescope. — (Fig. 131, next page.) — Figure
1 in the plate represents the telescope, supported in the
centre of gravity, with its rack- work motions, and mounted
on its mahogany stand, the three legs of which are made fo
close up together by means of the brass frame, a a a, which
is composed of three bars, connected together in the centre
piece by three joints, and also to the three legs of the
mahogany stand by three other joints, so that the three
bars of this frame may lie close against the insides of the
legs of the mahogany stand when they are pressed together
for convenience of carriage.

The brass pin, under the rack-work, is made to move
round in the brass socket, b, and may be tightened by
means of the finger-screw, d, when the telescope is directed
nearly to the object intended to be observed. This socket
turns on two centres, by which means it may be set perpen-
dicular to the horizon, or to any angle required in respect to
the horizon ; the angle may be ascertained by the divided
arc, and then made fast by the screw, e. If this socket be
set to the latitude of the place at which the telescope is
used, and the plane of this arc be turned on the top of the
mahogany stand, so as to be in the plane of the meridian,
the socket, b, being fixed to the inclination of the pole of
the earth, the telescope, when turned in this socket, will
have an equatorial motion, which is always very convenient
in making astronomical observations.

Figure 2 in the plate represents a stand to be used on a
table, which may be more convenient for many situations
than the large mahogany stand. The telescope, with its

ASTRONOMICAL INSTRUMENTS.
Fig. 131.

121

rack- work, may be applied to either of the two stands, as
occasion may require, the sockets on the top of both being
made exactly of the same size. The sliding rods may be
applied to the feet of the brass stand, so that the telescope
may be used with the same advantages on one as on the
other.

11

122 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

The tube A A may be made either of brass or mahogany
of three and a half feet long. The achromatic object-glass
of three and a half feet focal distance has an aperture of
two inches and three quarters.

The larger size is with a tube five feet long, and has an
achromatic object-glass of three inches and one quarter
aperture.

The eye-tube, as represented by B, contains four eye-
glasses, to be used for day or any land objects. There are
three eye-tubes, as C, which have two glasses in each, to
be used for astronomical purposes. These eye-tubes all
screw into the short brass tube at D. By turning the
button or milled head at /, this tube is moved out of the
larger, so as to adjust the eye-glasses to the proper dis-
tance from the object-glass, to render the object distinct to
any sight with any of the different eye-tubes.

The magnifying power of the three and a half feet tele-
scope with the eye-tube for land ' objects, is forty-five
times, and of the five feet, for land objects, sixty-five times.
With those for astronomical purposes, with the three and a
half feet, the magnifying powers are eighty, one hundred
and thirty, and one hundred and eighty ; and for the five
feet, one hundred and ten, one hundred and ninety, and two
hundred and fifty times.

Stained glasses, as g, are applied to all the different eye-
tubes, to guard the eye in observing the spots on the sun.
These glasses are to be taken off when the eye-tubes are
used for other purposes.

The rack-work is intended to move the telescope in any
direction required, and is worked " by means of the two
handles at h. When the direction of the tube is required
to be considerably altered, the worm screws, which act
against the arc and the circle, must be discharged ; then
the screw d being loosened, the pin of the rack-work will
move easily round in the socket, b.

For the more readily finding or directing the telescope to
any object, particularly astronomical objects, there is a
small tube or telescope, called the finder, fixed near the
eye-end of the large telescope. At the focus of the object-
glass of this finder there are two wires which intersect each
other in the axis of the tube, and as the magnifying power
is only about six times, the real field of view is very large ;
therefore any object will be readily found within it, which

ASTRONOMICAL INSTRUMENTS.

123

being brought to the intersection of the wires, it will then
be within the field of the telescope.

In viewing astronomical objects (and particularly when
the greatest magnifying powers are applied) it is very
necessary to render the telescope as steady as possible ; for
that purpose there are two sets of brass sliding rods, i i, as
represented in the plate. These rods connect the eye-end
of the telescope with two of the legs of the stand, by which
any vibrations of the tube, that might be occasioned by the
motion of the air or otherwise, will be prevented, and the
telescope rendered sufficiently steady for using the greatest
powers. These sliding rods move within one another with
so much ease as to admit of the rack-work being used in the
same manner as if they were not applied.

Improved Astronomical Telescopes. — This elegant instru-
ment, represented below, in Fig. 132, is one of the latest
and most approved construction ; the stand is of polished
mahogany, the legs jointed and supporting the telescope

Fig. 132.

124

BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

conveniently and steadily, having a brass pillar movable by
a tooth and wheel adjustment — by which it may be set at
any height required — with vertical brass joint and horizontal
motion, and rack and pinion motion to the tubes ; the length
of the tube is five feet, the aperture is three inches, having
terrestrial and celestial eye-pieces. The construction of the
various parts may be understood by reference to the one
previously described. Price, $150.00.

Fig. 133.

Another form of these splendid astronomical instruments
is represented in the above cut, Fig. 133, of a larger construc-
tion than the preceding ones, and is mounted on a stand of
a new and highly approved construction. It possesses the
advantage of supporting the telescope in two places, which
renders it extremely steady, a property of great importance
when viewing celestial objects with high magnifying powers.
It possesses, likewise, the advantage of enabling the observer
to continue seated at the same height from the floor, although
the telescope be raised to any altitude, the elevation being

ASTRONOMICAL INSTRUMENTS. 125

\

entirely at the object end, although it be changed from the
horizon to the zenith.

In the other constructions, where the centre of motion is
nearly in the middle of the tube, it is at times inconvenient
to stoop to the eye-end of the telescope when the altitude
of the object is considerable ; this new and improved con-
struction of a stand remedies this inconvenience, which,
together with its unusual steadiness, recommends it highly
to astronomical observers. The frame-work is composed of
bars of hard wood, firmly braced, and screwed together in
a very durable manner, and is mounted on three castors ;
these castors may, by the motion of a lever, be so arranged
that the stand may rest on the floor more steadily without,
the rollers, when the proper position of the telescope has
been obtained. For the horizontal and vertical motion of
the telescope, the arrangements are very complete ; the
former being a toothed wheel and arch ; the latter having
a small wheel moving a larger wheel, at the ends of the axis
of which there are cog wheels working in links, forming an
endless chain, or band, for drawing up one part of the
frame, and elevating the telescope. The tubes are of brass,
five and a half feet in length, the aperture of the object
glass four inches, having two terrestrial and two celestial
eye-pieces. Price, $275.00 to $350.00.

The Transit Instrument. — (Fig. 134, next page.) — The
transit is a meridional instrument, employed, in conjunction
with a clock or chronometer, for observing the passage of
celestial objects across the meridian, either for obtaining
correct time, or determining their difference of right ascen-
sion ; the latter of which, in the case of the moon and cer-
tain stars near her path, that differ but little from her in
right ascension, affords the best means of determining the
difference of longitude between any two places where cor-
responding observations may have been made. Such being
more especially the use of the portable transit instrument, it
forms a valuable accession to the apparatus of the scientific
traveller, who, remaining a short time at any station, is
enabled thereby to adjust his time-keepers both with ease
and accuracy, and to obtain the best data for finding his
longitude. It also may be employed very successfully in
determining the latitude.

The following figure represents this instrument as con-
11*

126 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 134.

structed by Mr. Troughton, when the telescope does not
exceed twenty inches, or two feet focal length. The tele-
scope-tube, A A, is in two parts, and connected together by
a sphere, B, which also receives the larger ends of two cones,
C C, placed at right angles to the direction of the telescope,
and forming the horizontal axis. This axis terminates in two
cylindrical pivots, which rest in Y's fixed at the upper end

ASTRONOMICAL INSTRUMENTS. 127

cf the vertical standards, D D. One of the Y's possesses a
small motion in azimuth, communicated by turning the
scre\v, a ; in these Y's the telescope turns upon its pivots.
But, that it may move in a vertical circle, the pivots must
be precisely on a level with each other, otherwise the tele-
scope will revolve in a plane oblique (instead of perpendicu-
lar) to the horizon. The levelling of the axis, as it is called,
is therefore one of the most important adjustments of the
instrument, and is effected by the aid of a spirit-level, E,
which is made for this purpose to stride across the telescope,
and rest on the two pivots.

The standards, D D, are fixed by screws upon a brass
circle, F, which rests on three screws, bed, forming the
feet of the instrument, by the motion of which the opera-
tion of levelling is performed. The two oblique braces,
G G, are for the purpose of steadying the supports, it being
essential for the telescope to have not only a free but a
steady motion. On the extremity of one of the pivots,
which extends beyond its Y, is fixed a circle, H, which
turns with the axis while the double vernier, e e, remains
stationary in a horizontal position, and shows the altitude
to which the telescope is elevated. The verniers are set
horizontal by means of a spirit-level, /, which is attached
to them, and they are fixed in their position by an arm of
brass, g, clamped to the supports by a screw at h. The
whole of this apparatus is movable with the telescope, and
when the axis is reversed, can be attached in the same man-
ner to the opposite standard.

Near the eye -end, and in the principal focus of the tele-
scope, is placed the diaphragm, or wire-plate, which, in the
theodolite or levelling telescope, need only carry two cross
wires, but in this instrument it has five vertical and two
horizontal wires. The centre vertical wire ought to be fixed
in the optical axis of the telescope, and perpendicular with
respect to the pivots of the axis. It will be evident, upon
consideration, that these wires are rendered visible in the
daytime by the rays of light passing down the telescope to
the eye ; but at night, when a very luminous object, as the
moon, is observed, they cannot be seen. Their illumination
is therefore effected by piercing one of the pivots, and ad-
mitting the light of a lamp fixed on the top of one of the
standards, as shown at I ; which light is directed to the
wires by a reflector placed diagonally in the sphere B ; the

128 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

reflector having a large hole in its centre, does not interfere
with the rays passing clown the telescope from the object,
and thus the observer sees distinctly both the wires and the
object at the same time ; when, however, the object is very
faint (as a small star), the light from the lamp would over-
power its feeble rays. To remedy this inconvenience, the
lamp is so constructed, that by turning a screw at its back,
or inclining the opening of the lantern, more or less light
may be admitted to the telescope, to suit the circumstances
of the case.

The telescope is furnished with a diagonal eye-piece, by
which stars near the zenith may be observed without incon-
venience.

Of the adjustments. — Upon setting the instrument up, it
should be so placed that the telescope, when turned down
to the horizon, should point north and south as near as can
possibly be ascertained. This of course can be but approx-
imate, as the correct determination of the meridian can only
be obtained by observation, after the other adjustments are
completed.

The first adjustment is that of the line of collimation.
Direct the telescope to some small distant well-defined ob-
ject (the more distant the better), and bisect it with the
middle of the central vertical wire ; then lift the telescope
very carefully out of its angular bearings, or Y's, and re-
place it with the axis reversed ; point the telescope again to
the same object, and if it be still bisected, the collimation
adjustment is correct ; if not, move the wires one half the
error, by turning the small screws which hold the diaphragm
near the eye-end of the telescope, and the adjustment will
be accomplished ; but as half the deviation may not be cor-
rectly estimated in moving the wires, it becomes necessary
to verify the adjustment by moving the telescope the other
half, which is done by turning the screw a ; this gives the
small azimuthal motion to the Y before spoken of, and con-
sequently to the pivot of the axis which it carries. Having
thus again bisected the object, reverse the axis as before,
and if half the error was correctly estimated, the object
will be bisected upon the telescope being directed to it ; if
not quite correct, the operation of reversing and correcting
half the error, in the same manner, must be gone through
again, until, by successive approximations, the object is found
to be bisected in both positions of the axis ; the adjustment

ASTRONOMICAL INSTRUMENTS. 129

will then be perfect. The collimation adjustment may
likewise be examined from time to time, by observing the
transit of Polaris, or any other close circumpolar star, over
the first three wires, which gives the intervals in time from
the first to the second, and from the first to the third wire ;
and then reversing the axis, observe the same intervals in a
reverse order, as the wires which were the three first, in the
former position, will now be the three last : if the intervals
in the first observations are exactly the same as the intervals
in the second, the collimation adjustment is correct; but
should the corresponding intervals differ, such difference
points out the existence of an error, which must be removed
as before described, one half by the collimating screws, and
the other half by the azimuthal motion of the instrument.

It is desirable that the central, or middle wire (as it is
usually termed), should be truly vertical ; as we should then
have the power of observing the transit of a star on any
part of it, as well as the centre. It may be ascertained
whether it is so, by elevating and depressing the telescope :
when directed to a distant object, if it is bisected by every
part of the wire, the wire is vertical ; if otherwise, it should
be adjusted by turning the inner tube carrying the wire-
plate, until the above test of its vertically be obtained, or
else care must be taken that the observations are made near
the centre only ; the other vertical wires are placed by the
maker equidistant from each other and parallel to the middle
one — therefore, when the middle one is adjusted, the others
are so too ; he also places the two transverse wires at right
angles to the vertical middle wire. These adjustments are
always performed by the maker, and but little liable to de-
rangement. When, however, they happen to get out of
order, and the observer wishes to correct them, it is done
by loosening the screws which hold the eye-end of the tele-
scope in its place, and turning the end round a small quantity
by the hand until the error is removed. But this operation
requires very delicate handling, as it is liable to remove the
wires from the focus of the object-glass.

The axis on which the telescope turns must next be set
horizontal. To do this, apply the level to the pivots, bring
the air-bubble to the centre of the glass tube, by turning
the foot-screw, b, which raises or lowers that end of the
axis, and consequently the level resting upon it ; then re-
verse the level by turning it end for end, and if the air-

130 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

bubble still remains central, the axis will be horizontal, but
if not, half the deviation must be corrected by the foot-
screw, b, and the other half by turning the small screw, i,
at one end of the level, which raises or lowers the glass-
tube (containing the air-bubble) with respect to its supports,
which rest upon the pivots. This, like most other adjust-
ments, frequently requires several repetitions before it is
accomplished, on account of the difficulty of estimating
exactly half the error.

Having set the axis on which the telescope turns, parallel
to the horizon, and proved the correct position of the cen-
tral wire or line of collimation, making it describe a great
circle perpendicular to that axis, it remains finally to make
it move in that vertical circle which is the meridian.

The correction of this error may be effected by turning
the screw, a, if the angular value of one revolution be
known, unless the instrument possesses an azimuth circle,
by which the telescope may be set exactly that quantity
from its present position.

But if the quantity of motion to be given to the adjust-
ing-screw, a, is not a matter of certainty, the observer, after
ascertaining the difference of the intervals, must make the
adjustment which he considers sufficient, and again proceed
to verify it by observation, until, by continued approxima-
tion, he succeeds in fixing his instrument correctly in the
meridian. Price, according to size, <fec., $150 to $300.

The Altitude and Azimuth Instrument. — (Fig. 135, next
page.) — To the centre of the tripod, A A, is fixed the verti-
cal axis of the instrument, of a length equal to about the
radius of the circle ; it is concealed from view by the ex-
terior cone, B. On the lower part of the axis, and in close
contact with the tripod, is centred the azimuth circle, C,
which admits of a horizontal circular motion of about three
degrees, for the purpose of bringing its zero exactly in the
meridian ; this is effected by a slow-moving screw, the
milled head of which is shown at D. This motion should,
however, be omitted in instruments destined for exact work,
as the bringing the zero into the meridian is not requisite,
either in astronomy or surveying ; it is in fact purchasing a
convenience too dearly, by introducing a source of error not
always trivial. Above the azimuth circle, and concentric
with it, is placed a strong circular plate, E, which carries

ASTRONOMICAL INSTRUMENTS.
Fig-. 131.

the whole of the upper works, and also a pointer, to show
the degree and nearest five minutes to be read off on the
azimuth circle ; the remaining minutes and seconds being
obtained by means of the two reading microscopes, F and
G ; this plate, by means of the conical part, B, which is
carefully fitted to the axis, rests on the axis, and moves con-
centrically with it. The conical pillars, H H, support the
horizontal or transit axis, I, which being longer than the
distance between the centre of the pillars, the projecting
pieces, c c, fixed to their top, are required to carry out the
Y's, a a, to the proper distance for the reception of the
pivots of the axis ; the Y's are capable of being raised or

132 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

lowered in their sockets by means of the milled-headed
screws, b b, for a purpose hereafter to be explained. The
weight of the axis, with the load it carries, is prevented
from pressing too heavily on its bearings, by two friction
rollers on which it rests, one of which is shown at e. A
spiral spring, fixed in the body of each pillar, presses the
rollers upwards, with a force nearly a counterpoise to the
superincumbent weight ; the rollers on receiving the axis
yield to the pressure, and allow the pivots to find their
proper bearings in the Y's, relieving them, however, from
a great portion of the weight.

The telescope, K, is connected with the horizontal axis,
in a manner similar to that of the portable transit instru-
ment. Upon the axis, as a centre, is fixed the double circle,
J J, each circle being close against the telescope, and on
each side of it. The circles are fastened together by small
brass pillars ; by this circle the vertical angles are mea-
sured, and the graduations are cut on a narrow ring of
silver, inlaid on one of the sides, which is usually termed
the face of the instrument ; a distinction essential in making
observations. The clamp for fixing, and the tangent-screw
for giving a slow motion to the vertical circle, are placed
beneath it, between the pillars, H H, and attached to them,
as shoAvn at L. A similar contrivance for the azimuth cir-
cle is represented at M. The reading microscopes for the
vertical circle, are carried by two arms bent upwards near
their extremities, and attached towards the top of one of
the pillars. The projecting arms are shown at N, and the
microscopes above at O.

A diaphragm, or pierced plate, is" fixed in the principal
focus of the telescope, on which are stretched five vertical
and five horizontal wires : the intersection of the two centre
ones, denoting the optical axis of the telescope, is the. point
with which the terrestrial object is bisected, when observing
angles for geodesical purposes. The vertical wires are used
for the same purpose as those in the transit telescope, and
the horizontal ones for taking altitudes of celestial objects.
A micrometer having a movable wire is sometimes attached
to the eye-end of the telescope, but it is not generally ap-
plied to instruments of portable dimensions. The illumina-
tion of the wires at night is by a lamp, supported near the
top of one of the pillars, as at d, and placed opposite the
end of one of the pivots of the axis, which, being perfo-

ASTRONOMICAL INSTRUMENTS. 1?3

rated, admits the rays of light to the centre of the tele-
scope-tube, where, falling on a diagonal reflector, they are
reflected to the eye, and illuminate the field of view ; the
whole of this contrivance is precisely similar to that de-
scribed as belonging to the transit instrument.

The vertical circle is usually divided into four quadrants,
each numbered, 1°, 2°, 3°, &c., up to 90°, and following
one another in the same order of succession ; consequently,
in one position of the instrument, altitudes are read off, and
with the face of the instrument reversed, zenith distances ;
and an observation is not to be considered complete till the
object has been observed in both positions. The sum of the
two readings will always be 90°, if there be no error in the
adjustments, in the circle itself, or in the observations.

It is necessary that the microscopes, 0 O, and the centre
of the circle, should occupy the line of its horizontal diame-
ter ; to effect which, the up-and-down motion (before spoken
of) by means of the screws, b b, is given to the Y's, to raise
or lower them, until this adjustment is accomplished. A
spirit-level, P, is suspended from the arms which carry the
microscopes : this shows when the vertical axis is set per-
pendicular to the horizon. A scale, usually showing seconds,
is placed along the glass-tube of the level, which exhibits
the amount, if any, of the inclination of the vertical axis.
This should be noticed repeatedly whilst making a series of
observations, to ascertain if any change has taken place in
the position of the instrument after its adjustments have
been completed. One of the points of suspension of the
level is movable up or down, by means of the screw, /, for
the purpose of adjusting the bubble. A striding level simi-
lar to the one employed for the transit instrument, and used
for a like purpose, rests upon the pivots of the axis. It
must be carefully passed between the radial bars of the
vertical circle to set it up in its place, and must be removed
as soon as the operation of levelling the horizontal axis is
performed. The whole instrument stands upon three foot-
screws, placed at the extremities of the three branches which
form the tripod, and brass cups are placed under the spheri-
cal ends of the foot-screws. A stone pedestal, set perfectly
steady, is the best support for this as well as the portable
transit instrument.

Use of the Altitude and Azimuth Instrument. — This is the
most generally useful of all instruments for measuring an-
12

134 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

gles, being applicable to geodesical as well as astronomical
purposes. In the hands of the surveyor, it becomes a the-
odolite of rather large dimensions, measuring with great
accuracy both vertical and horizontal angles. It does not
^possess the power of repetition ; but the effect of any error
of division on the azimuthal circle, may be reduced or de-
stroyed, by measuring the same angle upon different parts
of the arc ; thus, after each observation, turn the whole in-
strument a small quantity on its stand, and adjusting it,
again measure the required angle. A fresh set of divisions
is thus brought into use at every observation, and the same
operation being repeated many times, where great accuracy
is required, the mean result may be considered as free from
any error that may exist in the graduation. A repeating
stand has, of late years, been frequently added to this in-
strument, and is a most powerful and convenient appendage,
when great accuracy is required in the measurement of
azimuthal angles. The two opposite micrometers being read
off at each observation, will always remove the effect of any
error in the centring. The vertical angles shou]/1 in all
cases, be taken twice, reversing the instrument before taking
the second observation, when, as before observed, one of the
readings will be an altitude, and the other a zenith distance ;
the sum of the two readings, therefore, if the observation be
made with accuracy, and no error exists in the adjustments
of the instrument, will be exactly 90° ; and whatever the
sum differs from this quantity is double the error of the in-
strument in altitude, and half this double error is the correc-
tion to be applied -f- or — to either of the separate observa-
tions, to obtain the true altitude or zenith distance, + when
the sum of the two readings is less than 90°, and — when
greater.

In applying the instrument to astronomical purposes, it
was formerly the custom to clamp it in the direction of the
meridian, and after taking an observation, or series of ob-
servations, with the face of the instrument one way, to wait
till the next night, or till opportunity permitted, and then
take a corresponding series of observations of the same
objects, with the face of the instrument in a reversed posi-
tion. But this method being attended both with uncer-
tainty and inconvenience, it is now usual to complete at once
the set of observations, by taking the altitudes in both posi-
tions of the instrument as soon as possible after each other.

ASTRONOMICAL INSTRUMENTS. 135

When the meridian altitude is required, several observations
may be taken, a short time both before and after the meri-
dianal passage, with the face of the instrument in one
direction, and with it reversed, noting the time at each
observation ; and if we have the exact time of the object's
transit, its hour angle in time, or its distance from the meri-
dian at the moment of each observation, may be deduced.
This, with the latitude of the place (approximately known)
and the declination of the object, affords data for computing
a quantity called the reduction to the meridian, which added
to the mean of the observed altitudes, when the object is
above the pole, and subtracted when the object is below the
pole, will give the meridional altitude of the object, and
vice versa, for zenith distances. The nearer the observa-
tions are taken to the meridian, the less will the results
depend upon an accurate noting or knowledge of the time.

Price, $500 and upwards.

Fig. 136.

The Sun Dial (Fig. 136, as above) is an instrument for
showing the hour of the day by means of the sun's shadow.
In constructing this instrument, the object is to find, by
means of his shadow, the sun's distance at any time from
the meridian ; when this distance is known, the hour is also
known. Sun dials are usually constructed on a plane sur-
face of brass or other material, placed parallel to the horizon,

136 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

having a style, or gnomon, which is usually the edge of a
plate of metal, or a cylindrical rod, fixed at an angle equal
to the latitude of the place where the dial is to be used.

The face of the dial is divided into hours, from 5 to 12
on one side of the gnomon, and from 12 to 7 on the other;
there are intermediate divisions for half, quarter hours, and
minutes ; also, the principal points of the compass are drawn
on it. Fig. 137 represents the face of the dial, and Fig.
138 the gnomon and side view.

Fig. 137.

Fig 138.

The time indicated by the sun dial, is solar or true time,
and agrees with mean time, or that shoAvn by a clock, only
on four different days in the year. To find the mean time,
it is necessary to apply a correction, called the equation of
time.

Price, in brass, for any lat. required, 6 in. diam. $4.50.

" ' " " 7 " " $5.50.

« tt « (< « 3 « «< $7.50.

" in marble, " " " 7^ " " $4.00.

11 " " $6.50.

13 "• " $8.00.

" " " " " 18 " " $18.00.

The Sun Dial with Lens and Cannon. — (Fig. 139, next
page.) — This instrument is so arranged, that, the heat of the
sun falling through a lens, and being concentrated on the
touch-hole of a loaded cannon, it will precisely at noon be
fired. It consists of a slab of marble, having a sun dial of
the usual construction on one portion, and on another part a
brass cannon, at the sides of which there are two quadrants
with movable arms, by which a lens of about two and a

ASTRONOMICAL INSTRUMENTS.

137

half to three inches in diame- Fis- 139-

ter set in brass mounting is
supported ; the focus of the
lens corresponding to the dis-
tance of the touch-hole of the
cannon. On one of the quad-
rants there is marked a scale,
showing the altitude the lens
is to be set for every day in
the year, and corresponding
to the declination of the sun.
In setting the dial it should
be as near horizontal as possible, and the 12 o'clock line
north and south; when it will be found, that at 12 o'clock
the sun will shine through the lens and fall exactly on the
priming of the cannon, and the explosion take place.

Price, 7J in. diam. $8.50; 9J in. diam. $12.50.

Fig. 140.

Universal Ring Dial. — The Universal or Astronomical
Ring Dial (Fig. 140, as above,) is an instrument which
serves to find the hour of the day in any part of the earth ;
it consists of two rinses or flat circles, from 4 to G inches in

138 BEN.T. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

diameter, and their breadth, <fec., proportionable. The out-
ward ring represents the meridian of any place you are at,
and contains two divisions of 90° each, diametrically oppo-
site to one another, serving the one from the equator to the
north, the other to the south pole. The inner ring repre-
sents the equator, and turns exactly within the outer, by
means of two pivots in each ring, at the hour XII. Across
the two circles goes a thin reglet or bridge, with a cursor,
that slides along the middle of the bridge. In the cursor is
a little hole for the sun to shine through. The middle of
this bridge is conceived as the axis of the world, and the
extremities as the poles ; and on the one side are drawn the
signs of the zodiac, and on the other the days of the
month. On the edge of the meridian slides a piece, to which
is fitted a ring to suspend the instrument by. On the sur-
face of the inner ring the hours and parts are engraved.

To USE THE UNIVERSAL RING DIAL. — To find the Sun's
Declination and his place in the Ecliptic. — Set the slider on
the diameter or bridge, to the day of the month, and, answer-
ing to it on the other side, is the sun's place and his declina-
tion, either north or south, as the letters so marked direct.

To find the Latitude of the Place. — Find the sun's decli-
nation for that day ; then, if it be north, set the slider or
hanging piece to so many degrees on the front of the dial
marked S ; but if it be south declination, set the hanging
piece on that side of the graduated circle marked N. Put
a pin or wire in the small hole on the back side of the
instrument ; hold it up by the ring, the pin towards the
sun, so that the shadow thereof falls amongst the divisions
on the back of the dial ; then watch for the greatest alti-
tude ; which, counted from the lowermost part of those
degrees, the shadow so cut will be the latitude required.

To find the Hour of the Day. — Set the slider on the me-
ridian to the latitude of the place, and the slider on the
bridge or axis to the day of the month ; then open the hour
circle (now holding the instrument by the little ring, that
it may hang freely), turn the bridge towards the sun, till
you can see a small speck of light come through the slider
of the bridge, and fall on the middle line of the hour circle ;
and that point in the middle line where the speck falls,
shows the hour of the day at that place. The instrument
hanging in this position, the meridian, equinoctial, poles,
axis, <fec., are all of them correspondent to those supposed
in the heavens. Price, $6 to $20.

ASTRONOMICAL INSTRUMENTS.
Fig. 141.

139

Universal Joint Dial and Compass. — (Fig. 141, as above.)
— First set up the arc, which moves upon a joint, and con-
tains 90° of latitude ; then raise the plane of the dial that
has the hours engraved upon it, to the number of degrees
required for the latitude of your place.

Example. — For New York 40° 40' ; suffer the compass
needle to traverse freely upon its centre ; then turn the
compass till the north pole of the needle (which is denoted
by a cross wire near the extremity) settles at the north point
on the face of the compass, then level the whole by means
of the three feet or adjusting screws, and the spirit levels
contained within the compass.

The pole, or gnomon, must be raised perpendicular to the
plane of the dial, from the 10th of March to the llth of
September, between which times your hour-shadow will fall
on the plane of the dial ; and from the llth of September
to the 10th of March, the pole or gnomon must be reversed,
the shadow of which will then fall on the inside of the ring
which contains the corresponding hours with those on the
lane.

140 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

For the time in the forenoon, the shadow of that edge of
the gnomon next those hours, and parallel with the 6 o'clock
line, is that which is to be taken ; and for the afternoon, the
edge next its hours.

Note. — When the shadow comes to the meridian, or 12
o'clock, the whole thickness of the gnomon falls within that
space numbered XII.

It is proper to know the variation of the compass at your
place, and the right allowance made.

A little study with the instrument in the sunshine, will
clearly illustrate the foregoing directions.

Price, $5.00 to $20.00.

TJie Time Glass. — An instrument serving to measure the
flux of time, by the descent or running of sand from one
glass vessel into another. Small ones running from two to
five minutes are frequently mounted in bronzed metallic
frames. (Fig. 142.) Price, 50c. and 63c.

Fig. Ma

Fig. 142.

Larger time glasses (Fig. 143, as above,) are mounted in
frames of wood, either plain or highly polished, and may be
had running quarter, half, one hour, or two hours. Hour
glasses are used at sea for reckoning ; also, in academies
and schools where lessons are to be pursued for a given time.
Price, in plain frames, 1 hour, 88c. ; \ hour, $1.00;

1 hour, $1.25 ; 2 hours, $1.75.
" in polished rosewood frames, 1 hour, 81.88 ;
£ hour, $2.00 ; hour, $2.25 ; 2 hours, $3.

MOTION, MECHANICS,

ETC.

. Inertia Apparatus. — Inertia is that
property of matter by which it resists
any change of state, whether of rest
or motion.

This interesting piece of appara-
tus (Fig. 144) consists of a common
card and a brass ball of one inch or
more in diameter, supported on a
short pillar with a suitable base. To
one side of the base there is fixed a
steel spring, and a lever for drawing it back : on drawing
the spring and suddenly relieving it, the card is struck and
driven from under the ball off the pillar, while the ball rests
on the pillar as firmly as though the card had not been
knocked from under it. Price, $1.50.

Fig. 145.

Adhesion Plates. — These consist of two plates of glass
(Fig. 145), with knobs for handles, the flat surfaces ground
perfectly true. On pressing these together, they can be
separated only by the exertion of considerable force, the

142

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

power required being in proportion to. the area of the plates.
About 2^ to 3 inches in diameter is the usual size.

Price, $1.50.

Bohnenberger' s Machine. — This apparatus (See Fig. 146,
below) consists of three movable rings, A B C, mounted on
a stout base. The two inner rings are mounted on pivots ;
those on the smallest ring at right angles to the middle one ;
in the smallest ring is supported a metal ball, having a
roller on one of its pivots ; around the roller a string may
be wound, and when pulled off a rapid rotary motion may
be given to the ball. This motion may be given with its
axis in any position required, and when communicated, the
ring supporting the ball will resist considerable effort to
alter its position, and whatever way the instrument may be
turned, its axis will continue to maintain the position it had
when set in motion, illustrating the inertia, or that property
of matter which resists any change of state, whether of rest
or motion. Price, $5.00.

Fig. 146.

Fig. 147.

Instrument for illustrating Impenetrability . — (Fig. 147,
as above.) — By impenetrability is meant the fact, that two
bodies cannot occupy the same space at the same time.
The instrument to illustrate this principle consists of a glass
jar, A, to which is fitted, air-tight, a large cork, through
which a funnel, B, with small neck, and bent glass tube, C,
are inserted ; one end of the latter is to be immersed in a
vessel of water, D. If, now, water is poured into the fun-
nel and enters the jar, it will be found that the same

MOTION, MECHANICS, ETC.

143

quantity of air will escape through the water, the water
displacing the air, not penetrating it. Price, $1.00.

Tubes for Capillary Attraction. — (Fig. 148, as below.) —
These consist of a number of small glass tubes of different
sized bore, attached to a piece of wood, which may be
placed in a glass vessel, allowing all the tubes to be immers-
ed at one end. The liquid will rise to different heights in
the several tubes, and highest in the tubes having the small-
est bore. Price, $1.00.

Fig. 149.

Fig. 148.

Glass Plates for Capillary Attraction. — Fig. 149, as
above, consists of two plates of glass about five inches
square, joined at two of their edges, and separated at the
other a small space, forming an angle of about two degrees.
When immersed about an inch in water, the water will rise
between the plates, and will rise higher as the space is
smaller, forming a curve called a hyperbole. The effect is
shown best if the liquid is colored.

Price, $1.00 and $2.00.

Collision Balls for Action
and Reaction. — (Fig. 150). —
This apparatus consists of a
number of ivory balls, sus-
pended contiguous to each
other by strings of equal
length, sometimes mounted
on a frame, having a gradu-
ated arch over which the
balls may oscillate freely.

Fig. 150.

144 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Let two ivory balls of equal weight be suspended by
threads, as in the annexed figure ; if the former be then
drawn aside and suffered to fall against the latter, it will
drive it to a distance equal to that through which the first
ball fell ; but it will itself rest, having given up all its own
moving power to the second ball.

If five ivory balls, of equal weight, be hung by threads
of the same length, and the ball A be drawn out from the
perpendicular, and then let fall against the second, that and
the other two will continue stationary ; but the last ball,
B, will fly off the same distance as that through which the
first ball fell. For when the first ball strikes the second, it
receives a blow in return, which destroys its motion. The
second ball, although it does not appear to move, strikes
against the third, the reaction of which sets it at rest : the
action of the third ball is destroyed b}7 the reaction of the
fourth, and so on, till motion is communicated to the last
ball, which, not being reacted upon, flies off. Therefore,
when one body strikes against another, the quantity of mo-
tion communicated to the second body is lost by the first,
but this loss proceeds — not from the blow given by the
striking body — but from the reaction of the body which it
struck.

Price, set of 5, £ inch ivory balls, $1.25.

5, 1 " " " $2.00.

5, li " " " $3.00.

5, li " " " $4.50.

" mounted on mahogany frame

with graduated arch, $7.00 to $12.00.
" set of 5, li inch boxwood
balls, on mahogany
frame, with arch, $3.50 to $7.00.

" set of 5, li inch boxwood balls, $1.00.

Machine for showing the Composition of Forces. — Composi-
tion of forces is the finding the quantity and direction of a
single force, which is equivalent to two or more forces, act-
ing each differently, and of which the quantity and direction
are given. This machine (Fig. 151, next page) will prove
how two forces will conspire to produce one motion, and
that intermediate between them.

At bottom is a square frame or table ; at one corner rises
a slender rod, and on each side of it an upright wire, bear-

MOTION, MECHANICS, ETC.

145

ing a ball, which by a hole
is made to slip easily up and
down. In the centre beneath
is a third ball, resting loosely
on the table. If the ball A
falls, it would strike the ball
c, and drive it to D ; if B falls,
it would drive it to E, but if
both A and B are suffered to
fall at exactly the same time,
the ball c would obey the
impulse of both at once, and
take an intermediate course ;
that is, be propelled across the board to E.

Price, $5

Fig. 152.

Rocking Horse. — (Fig. 152.) —
This is an amusing figure, represent-
ing a horse and rider, and sometimes
used to illustrate the effect of plac-
ing the centre of gravity very low.
The figure is a light toy in the form
of a horse, having a wire and heavy
ball fastened to it, as represented
in the cut. If the hind feet of the
horse be placed on the table with-
out the ball being attached, the
centre of gravity will be beyond
the table, and the horse will of
course fall. But if the ball be at-
tached the centre of gravity will be below, and the line of
direction fall within the table ; the horse will consequently
be supported, and may be vibrated in an amusing manner.

Price, 75cts.

Also a variety of blocks, wheels, and figures, illustrating
the centre of gravity. Price, 50cts. to $1.50.

The Mechanic Powers. — The following instruments are
included under a set of mechanic powers: 1. Several sys-
tems of various kinds of pulleys. 2. The various kinds of
levers. 3. Inclined plane and carriage. 4. Wheel and
axle. 5. Wedge. 6. Screw. Also a set of weights to
use with them.

18

146 BENJ. PIKES, JR., DESCRIPTIVE CATALOGUE.

Fig. 153.

BENJ* PtKE J« 293- SRQADWfl

The Pulleys. — (Fig. 153, as above.) — The pulleys are
mounted on a neat polished mahogany base, 30 inches long
and 8 inches wide, with turned columns, 24 inches high, be-
hind which are fastened narrow scales, divided into inches
and parts thereof, the one scale numbering from the top,
and the other from the bottom, having a cord drawn across
the frame at each inch, dividing the whole into twenty-four
equal parts, for observing the distance each weight passes
through in use. The pulleys and their mountings are made
of brass, highly polished, having steel centres, connected
with which is a set of brass weights from ^ oz. to 1 6 ounces.

MOTION, MECHANICS, ETC. 147

In the best instruments there are seven systems of pulleys,
viz. 1. a fixed pulley with one wheel or sheave, turning on
pivots by a cord ; 2. one fixed and one movable pulley con-
nected ; 3. two fixed pulleys in one block, and two movable
pulleys in one block ; 4. two fixed pulleys in one block, the
one above the other, and two movable pulleys one above
the other ; 5. three pulleys arranged as the last in both the
moving and fixed pulley ; 6. a fixed pulley and four single
pulleys, having the cord supported from a fixed point ; 7.
White's pulley, which consists of a fixed pulley, having five
or more concentric grooves on the face of the wheel, with
diameters, as 1, 3, 5, and one movable pulley with another
such wheel, having corresponding grooves with diameters,
as 2, 4, 6, on the lower block; the cord being passed in suc-
cession over the grooves, as represented in the cut, it will be
thrown off by the action of the power in the same manner
as if every groove formed a separate and independently re-
volving wheel.

It is to be observed in using the pulleys, that the pulley
is to be balanced before the weights, representing the
power, are applied ; for this purpose a cup with hooks is
supplied, into which shot is placed till the pulley is accu-
rately balanced.

Price, with levers, screw, inclined plane, wheel

and axis, and set of brass weights, - $35.00.

The Levers. — The principal lever (Fig. 153, opposite page)
is a bar of brass about twelve inches long, supported on a
steel pivot, called the fulcrum, at about four inches from
one end, which end is made thicker than the longer one,
that they may equally balance. On the under side of the
lever is a succession of hooks, at one inch from the fulcrum,
and from each other, for the whole length ; and on the up-
per side of the lever a succession of hooks, on the longer
side only. The lever is attached by its fulcrum to the upper
part of the frame supporting the pulleys. Over the lever
is a frame supported by two brass pillars, having a sliding
pulley, which may be placed in* such a manner as to carry
the cord from any of the hooks on the upper side of the
lever, as weuld be required in using the lever in the second
and third order. On the top of the frame there is a series
of three levers, the shorter arm of the one acting on the
longer arm of the next, forming a compound lever. Also,

148 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

a bent lever, having holes at the distance of one inch apart
in both arms, and supported on a brass pillar, near which is
placed another brass pillar, on the upper part of which
there is a frame with sliding pulley, that can be set at any
height required for supporting the cord from the arm of
the bent lever.

Fig. 154.

The Inclined Plane. — (Fig. 154, as above.) — This con-
sists of two flat pieces of mahogany, about twelve inches
long and five inches wide, movable on a joint at one end,
and having a graduated semicircular arch divided into de-
grees, and numbered from 0° to 90? both ways, and having
a clamp, spring, and milled-head screw, to fasten it at any
angle desired ; at the other end of the plane is fixed a
pulley. A small carriage rolling on three wheels, and of a
size to move conveniently on the inclined plane, and weigh-
ing exactly four ounces, is used for showing the power gained,
being attached to a silk cord, which is passed over the
pulley, and the weight attached to the end ; if the length
of the inclined plane be twice its elevation, two ounces will
balance the carriage weighing four ounces, and the smallest
weight added to it will draw it up.

The Wedge.— (Fig. 155.) ^ 155-

— This is usually formed

of two equally inclined

surfaces, hinged together

at the base, and when

open forming two inclined

planes, and when closed, a wedge ; is usually made of

mahogany, about eight inches long. The principal use of

the wedge consists in its being urged by the stroke of a

MOTION, MECHANICS, ETC.

149

hammer, mallet, &c. A smart blow of a hammer of half a
pound weight, overcoming more resistance than the weight
of many pounds laid on the top of the wedge.

The Screw. — (Fig. 156, as below) — This piece of appa-
ratus consists of a screw, about 8 inches long, entering a
board supported on a base by two pillars ; in the top of the
screw there is a hole for the introduction of a lever. Fixed
in the same frame there is usually a brass spiral in the form
of the thread of a screw, having a lever, or handle, project-
ing through the frame, by which it is turned, and is used in
explaining the screw as an inclined plane, used in connexion
with the lever.

Fig. 157.

Fig. 156.

The Wheel and Axis— (Fig. 157, as above,)— This ap-
paratus consists of a mahogany wheel, the diameter in the
groove being 5 inches, on the side of which is a smaller
wheel of 2i inches diameter; they are mounted on an axis,
the diameter of which near the wheel is one inch, and the
other end half an inch. Both of these have silk cords fixed
to them, for suspending the weights ; the axis is supported
at the ends by small pivots, moving in a brass frame, Avhich
is usually attached to the frame supporting the system of
pulleys. #

150 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 153.

The above cut (Fig. 158) represents a set of mechanic
powers, in which arrangement a few of the articles are
modified, having the four most important systems of pulleys
arranged as those described, and having two straight levers
on the frame, and one bent lever, and a movable pulley at-
tached to a brass pillar with a nut on the bottom, by which
it can be shifted to different holes in the top of the frame,
for passing the cord over, in using the lever in the second
and third order, and also for the bent lever ; the inclined

MOTION, MECHANICS, ETC.

151

plane, wheel and axis, wedge and screw, are the same as
described in the preceding set.

Price, complete with inclined plane, wedge,

screw, and brass weights, 816.00.

Fig. 159.

Improved Set of Mechanic Powers. — (See Fig. 159, as
above.) — In this elegant set of mechanic powers, there are
five arrangements, or systems of pulleys ; others may be
made by altering the cords. On the top of the frame there
is mounted a wheel and axis, the axis being one inch in
diameter, and there being three different diameters to the

152 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

wheel, two, five, and ten inches, also having a number of
spokes, or handles, on the circumference.

The levers are conveniently arranged on a separate stand,
the principal one being arranged for explaining the balance.

The inclined plane and wedge are mounted also on a
separate stand.

The screw has a brass spiral, mounted in the same frame,
for conveniently explaining this power.

A set of brass weights accompany the set, from twenty
ounces down to one quarter of an ounce.

There is also added an apparatus for the showing the
composition and resolution of forces.

The frames are made uniform, and the three first instru-
ments are about three feet high, the brass work highly
finished, and the wood work well polished, forming an
imposing apparatus.

Price, for the whole, mounted on four frames, $60.00.

The Pulleys. — Two equal weights suspended to the ends
of a string that goes over a fixed pulley, will balance each
other, for they are equally stretched by the weights, and if
either of them be pulled down through any given space, the
other will rise through an equal space in the same time ;
and, consequently, as the velocity and the weights are equal
they must balance.

Though this pulley gives no mechanical advantage, it is a
source of great convenience, as it takes off the necessity a
man would be otherwise under of ascending along with the
weight, and thus lessens his labor; besides having this
further convenience, that by means thereof the joint strength
of several persons may be made use of to raise the same
weight. Either of the two first pulleys, A, in this set (Fig.
159) may be used to illustrate this arrangement, in which
case the movable pulley represented in the plate is discon-
nected.

B. The Movable Pulley in this arrangement has a weight
hanging at the lower end, and one end of the cord going
round the pulley, is fastened to a hook in the lower part of
the fixed pulley above, while the other end goes over the
fixed pulley, and is sustained by the weight. The two cords
support the whole weight, each supporting one half ; what-
ever holds the upper end of either rope, sustains one half
the weight. If you take hold of the cord and pull upwards

MOTION,, MECHANICS, ETC. 153

you will feel only half the weight, the cord attached to the
hook supporting the other half ; if you put the cord over
the fixed pulley, this only changes the direction, and, there-
fore, in pulling the cord downwards, you only feel half the
weight ; one ounce suspended from the cord passing over
the fixed pulley, will balance two ounces from the movable
pulley, and you will be enabled to lift twice as much weight
by the assistance of a single movable pulley, as you could
raise by your own actual strength. The power moves twice
as fast as the pulley with the weight ; therefore, the space
described by the power will be equal to twice the space
described by the weight, or the velocity of the weight is to
that of the power as one to two ; and it will be observed
that when the weight has been raised two inches, the power
has descended four inches.

c. When the upper and fixed block contains two pulleys,
which only turn on their axis, and the lower movable block
contains also two, which not only turn on their axis, but
rise with the block and weight, the advantage gained is as
four to one.

D. When there are three pulleys in the fixed block, and
three in the movable one, D, and the number of cords six,
the power is as six to one ; the advantage is the same whe-
ther the pulleys are placed parallel to or under each other.

E. In this arrangement the pulleys do not, as in the pre-
ceding systems, rise together in one block with the weight,
but act upon one another, so that each pulley doubles the
power. A power of one ounce will be in equilibrio with
two ounces at the first movable pulley, with four at the
second, with eight at the third ; and the velocity of the
power will be eight times that of the weight.

White's pulley described in the first set of mechanic pow-
ers is sometimes added to this set.

The Wheel and Axis (Fig. 159, page 151) is a machine
much used, and which is applied in a variety of forms. The
power acts on the circumference of the wheel ; the weight
is fastened to one end of a cord or rope, whose other end
winds round an axis that turns with the wheel. The axis,
F, and wheel, G, in Fig. 159, are fastened together so that
one cannot move without the other ; when a weight, w, is
to be raised by this engine, it is fixed to the end that goes
round the axis, but the power, p, is applied to one of the

154 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

several circumferences of the wheel. Pulling at the rope, p,
to turn the wheel once round, as much cord must be drawn
off as winds once about the circumference of the wheel, and
the cord to which the weight is suspended will wind once
around the axis, and the weight raised through as much
space as the circumference of the axis. If the diameter of
the wheel be ten inches, and the diameter of the axis be one
inch, then one ounce acting as a power, p, will balance ten
ounces as a weight, w ; and a small additional weight will
cause it to descend, and turn the wheel and its axis, and so
raise the weight, w ; and for every inch the weight rises, the
power, P, will fall ten inches ; if the diameter of the wheel
be five inches, it will balance with two ounces applied as a
power, and descend five inches ; or, supposing one ounce to
be the power, it will balance a weight of five ounces at the
axis ; if the diameter be two inches, or of any other size, the
same proportions will be maintained. The wheel and axis
may be considered as a lever, whose fulcrum is a line passing
through the centre of the wheel and middle of the axis, and
whose long and short arms are the radii of the wheel and
axis that are parallel to the horizon, and from whose extre-
mities the chords hang perpendicularly. Suppose that the
power does not act by a rope winding round a wheel, but
that it is moved by a man's strength applied immediately to
the spokes or handles, i, H, K ; if the man first lay hold of
the handle, H, and push it down to K, his hand passes through
the space, H K, and the handle will be brought down to K ;
he then lays hold of i, and pushes it to H, and so on till he
has turned the wheel once round ; and his hand, which is
now the power, will describe the whole circumference of a
circle, which is to be considered as the circumference of the
wheel. A wheel and axis may therefore be considered as a
kind of perpetual lever, on whose arms the power and
weight always act perpendicularly, though the lever turns
round its fulcrum ; and in like manner, when wheels and
axis move each other by means of teeth on their circumfer-
ence, such a machine may be considered as a perpetual
compound lever.

The Levers. — (Fig. 160, next page.) — In this arrangement
of levers, there is a brass beam or lever, A, having arms of
equal length, supported on its fulcrum at the side of the
pillar, which pillar is attached to a mahogany base ; in each

MOTION, MECHANICS, ETC.
Fig. 160.

lor,

arm of the lever there are eight holes, one inch apart, for
the purpose of attaching weights, or the scale pans, when
used to illustrate the balance. By this arrangement the
levers of the three orders may be readily illustrated ; in the
second and third order the pulleys, B, supported by a pillar
which is placed on the top of the frame, are used for sup-
porting the cord over the lever ; this pillar is movable in a
groove, and may be fixed in any position required, and fas-
tened by a thumb-screw projecting beneath the frame.

There are also two levers, c, D, of different lengths, that
at one end have a counterpoise consisting of a brass ball,
and which may be used as levers of the second and third
orders — the smaller one being represented in the cut as
arranged in the second order, having a weight of six ounces
supported at two inches from the axis, balanced by a weight
of two ounces supported at six inches from the axis, the
cord being supported by one of the movable pulleys, B.

The Bent Lever is represented at E, supporting a weight
on the horizontal arm, of six ounces, at a distance of two
inches from the axis, and balanced by a weight of two ounces

156

BENJ. PIKES, JR., DESCRIPTIVE CATALOGUE.

at a distance of six inches on the upright arm ; the cord in
this case also passing over and being supported by one of
the movable pulleys, B. Each of the levers on the upper
frame may be moved, or taken away, by loosening the thumb
screw attached, and the two levers may be arranged to illus-
trate a compound lever, and also may be arranged for this
purpose, connected with the lever A, attached to the pillar.

The Inclined Plane, represented in Fig. 171, consists of a
mahogany board, about 16 inches long and 3 or 4 inches
wide, hinged on the top of the frame and movable, having a
graduated arch, with screw to fasten it at any angle required.

Fig. 161.

There is a pulley at the end for supporting a cord from the
carriage, which carriage is on three wheels, and weighs ex-
actly four ounces. If the inclined plane be fixed at a height
equal to one-half the length of the plane and the carriage
placed thereon, having a cord passed over the pulley, and a
weight of two ounces attached thereto, it will be exactly
balanced ; or if the inclined plane be fixed at a height equal
to one-fourth the length of the plane, one ounce attached to

MOTION, MECHANICS, ETC. 15 7

the cord will balance the carriage, weighing four ounces,
and a small additional weight will draw it up.

The Wedge. — To the frame there are hinged two maho-
gany boards, which are drawn together by a brass frame-
work, to which cords are attached, which pass over and are
supported by pulleys, having weights at the lower ends of
the cords. Rollers are also fixed in this frame-work, against
which a wedge is introduced, having a cord and weight at-
tached, which weight, with that of the wedge, is to be con-
sidered as that of the impelling power. The weights at-
tached to the cords and supported over the pulleys, are to
be considered as the resistance of the wood acting equally
against the opposite sides of the wedge. If the back of the
wedge, D, is of the same length as each of the sides, the
wedge, with a weight sufficient to make it equal ten ounces,
will be in equilibrio against ten ounces, suspended from each
of the cords, B and c. If the back of the wedge, E, be equal to
one half the length of each of the sides, it will be in equilibrio
with twenty ounces from each of the cords, B and c, or the
power is to the weight as the back to the sum of the sides.

Fig. 162.

The Screw (Fig. 162, as above) consists of two parts, a
solid cylinder, around the surface of which passes what is
called the thread of the screw, and a corresponding cylin-
drical cavity.

One part is commonly fixed, whilst the other is turned
round ; and in each revolution the movable part is carried
in the direction of the cylinder, through a space equal in
length to the interval between t\vo contiguous threads. A
screw is seldom used without the application of a lever to
assist in turning it ; consequently, as much as the circumfer-
ence of a circle, described by this handle or winch, is greater
than the intervals or distance between the spirals, so much

14

158

BENJ. PIKE S. JR., DESCRIPTIVE CATALOGUE.

is the force of the screw. Supposing the distance between
the spirals to be one quarter of an inch, and the length of
the winch to be six inches, the circle described by the
handle of the winch, where the power acts, is nearly 38
inches, or 152 quarter inches, and consequently 152 times
as great as the distance between the spirals ; and, therefore,
a power at the handle, where the power acts, of no more
than one pound, will balance 152 pounds acting against the
screw, and as much additional power as is sufficient to over-
come the friction, will raise the 152 pounds.

Apparatus for the Composition and Resolution of Forces. —
(Fig. 163.) — This consists of a round table, usually about
18 inches in diameter, to the edge of which may be fixed
any number of brass pulleys, varying their direction at

Fig. 1G3.

pleasure. To use, place a circular paper upon the round
table, so that its centre may coincide with that of the table.
Upon this paper a triangle A B c is delineated, whose sides

MOTION, MECHANICS, ETC.

159

are to one another, as 2, 3, and 4. Draw c E parallel to
A B, and continue A c towards D.

I take three strings, which are joined in one point by a
knot ; and placing the point over c, stretch the strings over
c D, c E, c B, and place the pulleys, T, T, T, to coincide Avith
the direction of the strings ; then putting the strings over
their respective pulleys, at the end of the thread, c D, sus-
pend a weight of four pounds, to c E three pounds, and to
c B two pounds. These weights will remain in equilibrio
while the knot remains over c ; but if it be removed out of
that point, they will not be at rest.

It is evident from this experiment, that power is always
lost in the composition of forces ; for here a weight of
three pounds, and another of two, only counterpoise a
weight of four.

Screw Press. — (Fig. 164.) — This represents a small model
of a screw, as mounted in a press, extensively used in the
arts, as for pressing cotton, for book-binders, etc.

Price, $2.25.

Fig. 165.
Fig. 164.

The Endless Screw.— (Fig. 165.) — This consists of a
screw combined with a wheel and axle, in such a manner
that the threads of the screw work into the teeth fixed on
the periphery of the wheel. Suppose the power applied to
the handle of the screw, and the weight attached to the
axle of the wheel, then there will be equilibrium when the
power is to the weight as the distance between the threads
multiplied by the radius of the axle, is to the length of the
lever or handle, multiplied by the radius of the wheel.

Price, in brass, $8.00.

160 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

The Capstan. — (Fig. 166.) — One of the most efficient
forms of the wheel and axle is the capstan, used on board
of ships and in dock-yards. It consists of a vertical spindle
fixed firmly as in the deck of the vessel, but turning on its
axis, and supporting a drum, or solid cylinder connected
with it, and having its periphery pierced with holes directed
towards its centre. It is then worked by long levers, in-
serted in the holes, by men who walk in succession round
the capstan, and thus make it revolve ; a rope or cable
wound about the axle may act with force sufficient to weigh
a ponderous anchor, or warp a heavy laden vessel into
harbor.

Small models made in mahogany, 6 inches high, serve to
illustrate the use of this instrument. Price, $2.50.

Fig. 166. Fig. 1G7.

Double Cone and Inclined Plane. — (Fig. 167.) — This is a
simple mechanical experiment, to show that although it is a
natural law that the centre of gravity of a body always
tends to, and endeavors to obtain the lowest station, yet
there may be cases in which it appears to roll upwards.

The double cone rests upon the two sides of a sloping
railway ; if the cone be placed at the narrow end of this, it
will roll towards the other, and as the other is the higher
end, the cone appears to roll upwards ; though upon observ-
ing the height of the apex at each end, at the beginning
and end of its course, it will be seen that in reality it rolls
downwards ; the centre of gravity being situated in the axis.
Price, $1.00 to $2.00.

" with screws, $3.00.

The Whirling Table. — A description of the whirling table,
or machine for exhibiting and demonstrating by experiments
the nature of central forces, or the principal laws of gravita-
tion of the planetary motions in their orbits :

The whirling-table may be considered by a lecturer as an
essential part of his mechanical apparatus.

MOTION, MECHANICS, ETC.
Fig. 168.

Ifll

(Fig. 168, as above.) — A A is a strong frame of wood,
B a winch or handle fixed on the axis, C, of the wheel, D,
round which is the catout string, F, which also goes round

14*

1(52 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

the small wheels, G and H, crossing between them and the
great wheel, D. On the upper end of the axis of the wheel
(T, above the frame, is fixed by a screw the bearer, M. On
the axis of the wheel, H, is fixed the bearer, N T Z : and it
is easy to see, that when the winch, B, is turned, the wheels
and bearers are put into a whirling motion.

Each bearer has a wire fixed and screwed tight into it by
nuts on the outside. And when these nuts are unscrewed,
the wires may be drawn out in order to change balls U
and V, which slide upon the wires, thus keeping the balls
up from touching the wood below them. A strong silk
line goes through each ball, and is fixed to it at any length
from the centre of the bearer to its end, as occasion requires,
by a nut-screw at the top of the ball ; the shank of the
screw goes into the centre of the ball, and presses the line
against the under side of the hole that it goes through. The
line goes from the ball, and under a small pulley fixed in
the middle of the bearer ; then up through a socket in the
round plate, see S and T, in the middle of each bearer ; then
through a slit in the middle of the frame at the top, 0 and
P, of each tower, and going over a small pulley on the top,
comes down again the same way, and is at last fastened to
the upper end of the socket fixed in the middle of the above
mentioned round plate. These plates, S and T, slide up
and down upon the pillars supporting the tower. The balls
and plates being thus connected, each by its particular line,
it is plain, that if the balls be drawn outwards, or towards
the ends, M and N, of their respective bearers, the round
plates, S and T, will be drawn up to the top of their re-
spective towers, 0 and P.

There are several brass weights, some of two ounces,
some of three, and some of four, to be occasionally put
within the towers, 0 and P, upon the round plates, S and T :
each weight having a round hole in the middle of it, for
going upon the sockets or axes of the plates, and is slit
from the edge to the hole, for allowing it to be slipt over
the aforesaid line, which comes from each ball to its respec-
tive plate.

The experiments to be made by this machine are as fol-
lows : —

1. The propensity of matter to keep the state it is in. — Take
away the bearer, M X, and fasten on the round board (Fig.
169, opposite page), and the ivory ball, a, to' which the line

MOTION, MECHANICS, ETC. 163

or silk cord, b, is fast- Fis- 169.

ened at one end ; and
having made a loop
on the other end of
the cord, put the loop
over a pin fixed in the
centre of the board,
d. Then turning the
winch, B, to give the board a whirling motion, you will see
that the ball does not immediately begin to move with the
board, but, on account of its inactivity, it endeavors to con-
tinue in the state of rest which it was in before. Continue
turning until the board communicates an equal degree of
motion with its own to the ball, and then turning on, you
will perceive that the ball will remain upon one part of the
board, keeping the same velocity with it, and having no re-
lative motion upon it, as is the case with everything that
lies loose upon the plane surface of the earth, which, having
the motion of the earth communicated to it, never endeavors
to remove from that place. But stop the board suddenly
by hand, and the ball will go on, and continue to revolve
upon the board until the friction thereof stops its motion ;
which shows, that matter being once put in motion, will
continue to move for ever, if it meet with no resistance. In
like manner, if a person stands upright in a boat, before it
begins to move he can stand firm ; but the moment the boat
sets off, he is in danger of falling towards that place which
the boat departs from : because, as matter, he has no natural
propensity to move. But when he acquires the motion of
the boat, let it be ever so swift, if it be smooth and uniform,
he will, stand as upright and as firm as if he were on the plane
shore ; and if the boat strike against any obstacle, he will
fall towards that obstacle, on account of the propensity he
has, as matter, to keep the motion which the boat has put
him into.

2. Take away this ball, and put a longer cord to it, which
may be put down through the hollow axis of the bearer,
M X, and wheel, G, and fix a weight to the end of the
cord below the machine ; which weight, if left at liberty,
will draw the ball from the edge of the whirling board to
its centre.

Bodies moving in orbits have a tendency to fly out of these
crbits. — Draw off the ball a little- from the centre, and turn

1G4 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

the winch ; then the ball will go round and round with the
board, and will gradually fly off further and further from the
centre, and raise up the weight below the machine ; which
shows, that all bodies revolving in circles have a tendency
to fly off from these circles, and must have some power
acting upon them from the centre of motion, to keep them
from flying off. Stop the machine, and the ball will con-
tinue to revolve for some time upon the board ; but as the
friction gradually stops its motion, the weight acting upon
it will bring it nearer and nearer to the centre in every revo-
lution, until it brings it quite thither. This shows, that if
the planets met with any resistance in going round the sun,
its attractive power would bring them nearer and nearer to
it in every revolution, until they fell upon it.

3. Bodies move faster in small orbits than in large ones. —
Take hold of the cord below the machine with one hand,
and with the other throw the ball upon the round board as
it were at right angles to the cord, by which means it will
go round and round upon the board. Then observing with
what velocity it moves, pull the cord below the machine,
which will bring the ball nearer to the centre of the board,
and you will see, that the nearer the ball is drawn to the
centre, the faster it will revolve ; as those planets which are
nearer the sun revolve faster than those which are more re-
mote ; and not only go round sooner, because they describe
smaller circles, but even move faster in every part of their
respective circles.

4. Their centrifugal forces shown. — Take away this ball,
and apply the bearer, M X, whose centre of motion is in its
middle at w. Then put two balls, Y and U, of equal weights
upon their bearing wires, and having fixed them at equal
distances from their respective centres of motion, w and x,
upon their silk cords, by the screw nuts, put equal weights
in the towers 0 and P. Lastly, put the catgut strings, E
and F, upon the grooves, G and H, of the small wheels,
which, being of equal diameters, will give equal velocities
to the bearers above, when the winch, B, is turned : and the
balls, U and V, will fly off towards M and N ; and will
raise the weights in the towers at the same instant. This
shows, that when bodies of equal quantities of matter revolve
in equal circles with equal velocities, their centrifugal forces
are equal.

5. Take away these equal balls, and instead of them put

MOTION, MECHANICS, ETC. 165

a ball of six ounces into the bearer, M X, at a sixth part of
the distance, w z, from the centre, and put a ball of one
ounce into the opposite bearer, at the whole distance, x y,
which is equal to w z, from the centre of the bearer ; and
fix the balls at these distances on their cords, by the screw
nuts at top, and then the ball U, which is six times as heavy
as the ball Y, will be only a sixth part of the distance from
its centre of motion ; and, consequently, will revolve in a
circle of only a sixth part of the circumference of the circle
in which V revolves. Now, let any equal weights be put
into the towers, and the machine be turned by the winch,
which, as the catgut string is on equal wheels below, will
cause the balls to revolve in equal times, but V will move
six times as fast as U, because it revolves in a circle of six
times its radius ; and both the weights in the towers will
rise at once. This shows that the centrifugal forces of re-
volving bodies, or their tendencies to fly off from the circles
they describe, are in direct proportion to their quantities of
matter multiplied into their respective velocities ; or into
their distances from the centres of their respective circles.
For, suppose U, which weighs six ounces, to be two inches
from its centre of motion, w, the weight multiplied by the
distance, is 12 ; and supposing V, which weighs only one
ounce, to be 12 inches distant from the centre of motion, x,
the weight one ounce, multiplied by the distance, 12 inches,
is 12. And as they revolve in equal times, their velocities
are as their distances from the centre, namely, as 1 to 6.

If these two balls be fixed at equal distances from their
respective centres of motion, they will move with equal
velocities ; and if the tower, 0, have six times as much
weight put into it, as the tower, P, has, the balls will raise
their weight exactly at the same moment. This shows that
the ball U, being six times as heavy as the ball V, has six
times as much centrifugal force, in describing an equal circle
with an equal velocity.

6. A double velocity in the same circle is a balance to a
quadruple power of gravity. — If bodies of equal weights re-
volve in equal circles with unequal velocities, their centri-
fugal forces are as the squares of the velocities. To prove
this law by an experiment, let two balls, U and V, of
equal weights, be fixed on their cords at equal distances
from their respective centres of motions, w and x ; and then
let the catgut string, E, be put round the wheel, K, whose

166 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

circumference is only one -half of the circumference of the
wheel, H or G, and over the pulley, s, to keep it tight ; and
let four times as much weight be put into the tower, P, as
into the tower, O. Then turn the winch, B, and the ball, V,
will revolve twice as fast as the ball IT, in a circle of the same
diameter, because they are equidistant from the centres of
the circles in which they revolve ; and the weights in the
towers will both rise at the same instant ; which shows, that
a double velocity in the same circle will exactly balance a
quadruple power of attraction in the centre of the circle.
For the weights in the towers may be considered as the at-
tractive forces in the centres, acting upon the revolving
balls ; which, moving in equal circles, is the same thing as
if they moved in one and the same circle.

7. If bodies of unequal weights revolve in unequal circles,
in such a manner that the squares of the times of their
going round are as the cubes of their distances from the
centres of the circles they describe ; their centrifugal forces
are inversely as the squares of their distances from those
centres. For, the catgut string remaining as in the last ex-
periment, let the distance of the ball, V, from the centre, x,
be made equal to two of the cross divisions on its bearer ;
and the distance of the ball, U, from the centre, w, be
three and a sixth part ; the balls themselves being of equal
weights, and V making two revolutions by turning the
winch, in the time that U makes one ; so that if we suppose
the ball, V, to revolve in one second, the ball, U, will re-
volve in two seconds, the squares of which are one and four,
for the square of 1 is only 1, and the square of 2 is 4 ;
therefore the square of the period, or revolution of the ball,
V, is contained four times in the square of the period of the
ball, U. But the distance of V is 2, the cube of which is
8, and the distance of U is 3£, the cube of which is 32, very
nearly, in which 8 is contained four times ; and, therefore,
the squares of the periods of Y and U are to one another
as the cubes of their distances, from x and w, which are the
centres of their respective circles. And if the weight in the
tower, O, be four ounces, equal to the square of 2, the dis-
tance of V from the centre, x j and the weight in the tower,
P, be ten ounces, nearly equal to the square of 3|, the dis-
tance of U from w ; it will be found, upon turning the
machine by the winch, that the balls, U and V, will raise
their respective weights at the same instant of time. Which

MOTION, MECHANICS, ETC. 167

confirms that famous proposition of Kepler, viz. That the
squares of the periodical times of the planets round the sun,
are in proportion to the cubes of their distances from him;
and that the sun's attraction is inversely as the square of
the distance from his centre ; that is, at twice the distance,
his attraction is four times less ; and thrice the distance,
nine times less ; at four times the distance, sixteen times
less ; and so on to the remotest part of the system.

8. Take off the catgut string, E, from the great wheel, D,
and the small wheel, H, and let the string, F, remain upon
the wheels D and G. Take away also the bearer, M X, from
the whirling-board, and instead thereof put the machine,
A B (Fig. 170) upon it, fixing this machine to the centre of
the board by its screw. In this

machine are two glass tubes, a
and b, close stopped at both «£
ends, and inclined to an angle f
of 30 or 40 degrees; and each
tube is about three quarters full
of water. In the tube, a, is a
little quicksilver, which naturally
falls down to the end a, in the water, because it is heavier
than its bulk of water ; and on the tube, b, is a small cork,
which floats on the top of the water at e, because it is lighter ;
and it is small enough to have liberty to rise or fall in the
tube. While the wheel, with this machine upon it, continues
at rest, the quicksilver lies at the bottom of the tube a,
and the cork floats on the water near the top of the tube b.
But, upon turning the winch, and putting the machine in
motion, the contents of each tube will fly off towards
the uppermost ends, which are furthest from the centre of
motion, the heaviest with the greatest force. Therefore the
quicksilver in the tube, a, will fly off quite to the end /, and
occupy its bulk of space, there excluding the water from that
place, because it is lighter than quicksilver ; but the water
in the tube, b, flying off to its higher end, e, will exclude the
cork from that place, and cause the cork to descend towards
the lowermost end of the tube, where it will remain upon
the lowest end of the water, near 6 ; for the heavier body,
having the greater centrifugal force, will therefore possess
the uppermost part of the tube ; and the lighter body will
keep between the heavier and the lowermost part.

9. If one body move round another, both of them must move

168 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

round their common centre of gravity. — If a body be so placed
on the whirling-board of the machine, that the centre of
gravity of the body be directly over the centre of the board,
and the board be put into ever so rapid a motion by the
winch, B, the body will turn round with the board, but will
not remove from the middle of it ; for, as all parts of the
body are in equilibrio round its centre of gravity, and the
centre of gravity is at rest in the centre of motion, the cen-
trifugal force of all parts of the body will be equal at equal
distances from its centre of motion, and therefore the body
will remain in its place. But, if the centre of gravity be
placed ever so little out of the centre of motion, and the
machine be turned swiftly round, the body will fly off to-
wards that side of the board on which its centre of gravity
lies. Thus, if the wire, C, with its little ball, B (Fig. 171),
be taken away from the demiglobe A, and the flat side, ef,
of this demi-globe be laid upon the whirling -board of the
machine, so that their centres may coincide ; if then the
board be turned ever so quick by the winch, the demi-globe

Fig. 171.

will remain where it was placed. But if the wire, C, be
screwed into the demi-globe at d, the whole becomes one
body, whose centre of gravity is now at or near d. Let the
pin, c, be fixed in the centre of the whirling-board, and the
deep groove, b, cut in the flat side of the demi-globe, be put
upon the pin, so that the pin may be in the centre of A,
and let the whirling- board be turned by the winch, which
will carry the little ball, B, with its wire, C, and the demi-
globe, A, all round the centre pin, c i ; and then, the centri-
fugal force of the little ball, B, which weighs only one ounce,
will be so great as to draw off the demi-globe, A, which
weighs two pounds, until the end of the groove, at e, strikes
against the pin, c, and so prevents the demi-globe, A, from
going any further; otherwise, the centrifugal force of B
would have been great enough to have carried A quite off
the whirling-board ; which shows, that if the sun were
placed in the very centre of the orbits of the planets, it could
not possibly remain there ; for the centrifugal forces of the

MOTION, MECHANICS, ETC. 109

planets would carry them quite off, and the sun with them ;
especially when several of them happened to be in any one
quarter of the heavens. For the sun and planets are as
much connected by the mutual attraction that subsists be-
tween them, as the bodies A and B are by the wire C, which
is fixed into them both. And even if there were but one
single planet in the whole heavens to go round ever so large
a sun in the centre of its orbit, its centrifugal force would
soon carry off both itself and the sun. For, the greatest
body placed in any part of free space might be easily moved ;
because, if there were no other body to attract it, it could
have no weight or gravity of itself; and consequently,
though it could have no tendency of itself to remove from
that part of space, yet it might be very easily moved by
any other substance.

10. As the centrifugal force of the light body, B, will
not allow the heavy body, A, to remain in the centre of
motion, even though it is twenty-four times as heavy as B ;
let us now take the ball, A (Fig. 172), which weighs six
ounces, and connect it by the wire,
C, with the ball, B, which weighs
only one ounce ; and let the fork, E,
l>e fixed in the centre of the whirl-
ing-board ; then hang the balls upon
the fork by the wire, C, in such
manner, that they may exactly ba-
lance each other ; which will be
when the centre of gravity between
them, in the wire at d, is supported
by the fork. And this centre of
gravity is as much nearer to the
centre of the ball, A, than to the centre of the ball, B, as
A is heavier than B, allowing for the weight of the wire
on each side of the fork. This done, let the machine be
put into motion by the winch ; and the balls, A and B, will
go round their common centre of gravity, d, keeping their
balance, because either will not allow the other to fly off with
it. For, supposing the ball, B, to weigh only one ounce, and
the ball, A, to be six ounces ; then, if the wire, C, were
equally heavy on each side of the fork, the centre of gravity,
d, would be six times as far from the centre of the ball, B,
as from that of the ball, A, and, consequently, B will revolve
with a velocity six times as great as A does ; which will

170 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

give B six times as much centrifugal force as any single
ounce of A has : but then, as B is only one ounce, and A
six ounces, the whole centrifugal force of A will exactly
balance the whole centrifugal force of B : and, therefore,
each body will detain the other so as to make it keep in its
circles. This shows, that the sun and the planets must all
move round the common centre of gravity of the whole
system, in order to preserve that just balance which takes
place among them. For, the planets being as inactive and
dead as the above balls, they could no more have put them-
selves into motion than these balls can ; nor have kept in
their orbits without being balanced at first with the greatest
degree of exactness upon their common centre of gravity,
by the Almighty hand that made them and put them in
motion.

Perhaps it may be here asked, that since the centre of
gravity between these balls must be supported by the fork,
E, in this experiment, what prop it is that supports the
centre of gravity of the solar system, and consequently
bears the weight of all the bodies in it ; and by what is the
prop itself supported ? The answer is easy and plain ; for
the centre of gravity of our balls must be supported, be-
cause they gravitate towards the earth, and would therefore
fall to it : but, as the sun and planets gravitate only towards
one another, they have nothing else to fall to ; and therefore
have no occasion for anything to support their common
centre of gravity : and if they did not move round that cen-
tre, and consequently acquire a tendency to fly off from it
by their motions, their mutual attractions would soon bring
them together; and so the whole -would become one mass
in the sun : which would also be the case if their velocities
round the sun were not quick enough to create a centrifugal
force equal to the sun's attraction.

11. Take away the fork and balls from trie whirling-board,
and place the frame, A B (Fig. 173), thereon, fixing its
centre to the centre of the whirling -board by the screw. In

MOTION, MECFIANICS, ETC. l7l

this frame are two balls, D and E, of unequal weights, con-
nected by a tube,/, and made to slide easily upon the wire,
C, stretched from end to end of the frame, and made fast
by nut-screws on the outside of the ends. Let these balls
be so placed upon the wire, C, that their common centre of
gravity, g, may be directly over the centre of the whirling-
board. Then turn the machine by the winch, ever so swiftly,
and the trough and balls will go round their centre of gravity,
so as neither of the balls will fly off; because, on account of
the equilibrium, each ball detains the other with an equal
force acting against it. But if the ball, E, be drawn a little
more towards the end of the frame at A, it will remove the
centre of gravity towards that end from the centre of mo-
tion ; and then, upon turning the machine, the little ball, E,
will fly off, and strike with considerable force against the
end, A, and draw the great ball, B, into the middle of the
frame, or if the great ball, D, be drawn towards the end, 13,
of the frame, so that the centre of gravity may be a little
towards that end from the centre of motion, and the
machine be turned by the winch, the great ball, D, will fly
oft* and strike violently against the end, B, of the frame, and
will bring the little ball, E, into the middle of it. If the
frame be not made very strong, the ball, D, will break
through it.

The earth's motion demonstrated. — From the principles
thus established, it is evident, that the earth moves round
the sun, and not the sun round the earth ; for the centri-
fugal law will never allow a great body to move round a
small one in any orb whatever ; especially when we find,
that if a small body moves round a great one, the great one
must also move round the common centre of gravity be-
tween them. And it is well known, that the quantity of
matter in the sun is 227,000 times as great as the quantity
of matter in the earth.

Now, as the sun's distance from the earth is at least
81,000,000 of miles, if we divide that distance by 227,000,
we shall only have 357 for the number of miles that the
centre of gravity betAveen the sun and earth is distant from
the sun's centre. And as the sun's semidiameter is one-
fourth of a degree, which, at so great a distance as that of
the sun, must be no less than 381,500 miles, if this be
divided by 357, the quotient will be 1268|, which shows,
that the common centre of gravity between the sun and

172

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

Fig. 174.

earth is within the body of the sun; and is only the 1068|
part of his semidiameter from his centre towards his surface.
All globular bodies, whose parts can yield, and which do
not turn on their axes, must be perfect spheres, because all
parts of their surfaces are equally attracted towards their
centres. But all such globes which do turn on their axes
will be oblate spheroids ; that is, their surfaces will be
higher, or further from the centre, in the equatorial than in
the polar regions. For, as the equatorial parts move
quickest, they must have the greatest centrifugal force ; and
will therefore recede furthest from the axis of motion. Thus
if two circular hoops, A B and C D
(Fig. 174), made thin and flexible,
and crossing one another at right
angles, be turned round their axis, E
F, by means of this machine, and the
axis be loose in the pole or intersec-
tion, e, the middle parts A, B, C, D,
will swell out, so that the whole will
appear of an oval figure, the equa-
torial diameter being considerably
longer than the polar. That our
earth is of this figure is demonstrable
from actual measurement of some
degrees on its surface, which are found to be longer in the
frigid zones than in the torrid ; and the difference is found
to be such as proves the earth's equatorial diameter to be
thirty-six miles longer than its axis. Price, $7o.OO.

Whirling Table. — A simpler construction of the whirling-
table is represented in the next page (Fig. 175), capable of
performing most of the preceding experiments in a satisfac-
tory manner. Having all the apparatus of the former, and
the bearers constructed in a simpler manner, not working so
elegantly, but being a less costly arrangement, the frame is
made three feet long and one foot wide. Price, $30.00.

MOTION, MECHANICS, ETC.
Fig. 175.

173

Atwood's Apparatus for making experiments on the Recti-
lineal Motion of Bodies which are acted on by constant forces.

This elegant and accurate machine, represented in Fig. 176,
page 175, is the contrivance of Mr. Atwood, and renders
sensible to the eye and ear, by means of a set of friction

174 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

wheels, various weights, and a clock, the laws of motion
uniformly accelerated or retarded, as well as those of uni-
form motion, and that without employing a space for the
weights, of more than five and a half or six feet, which
causes it to be extremely convenient and demonstrative for
a course of lectures.

Mechanical experiments are of two kinds ; the one relating
to the quiescence of bodies, and the other to their motion.

Among the former are included those which demonstrate,
or rather make evident to the senses, the equilibrium of the
mechanic powers, and the corresponding proportions of the
weights sustained, to the forces which sustain them, the
properties of the centre of gravity, the composition and
resolution of forces, &c.

By the latter, or those on motion, are shown the laws of
collision, of acceleration, and the various effects of forces
which communicate motion to bodies.

Of mechanical experiments it may be proper to observe
to you, that those wherein an equilibrium is formed, will
frequently appear coincident with the theory, although con-
siderable errors are committed in their construction. This
arises from the effects of friction, tenacity, and other causes.
The case is different in experiments concerning the motion
of bodies ; in which, whatever care be taken to render the
proportion of the forces, and the weights moved, such as is
required by the theory ; yet the interference of friction, which
renders the former apparently more perfect than they really
are, causes these to differ from the theory.

If the experiments are only designed to assist the ima-
gination, by substituting sensible objects instead of abstract
and ideal quantities, an apparent agreement between the
theory and experiment may be sufficient to answer this pur-
pose, although it may be produced from an erroneous
construction : such experiments cannot, however, impress
the mind with that satisfactory conviction that arises from
experiments accurately made.

Dr. Desaguliers tried the effect of falling bodies, by letting
a leaden ball fall from the inner cupola of St. Paul's church,
whose altitude from the ground is 272 feet. The ball de-
scended through this space in four seconds and a half ; in
which time, from theory, it should have descended through
325 feet, which makes a difference of about one-fifth of the
actual descent between the experiment and the theory. Dr.

MOTION, MECHANICS, ETC.

175

Fig. 176.

17G BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Desaguliers shows, in his fifth lecture, that this difference
arose principally from the resistance of the air. To remedy
the defects of these experiments, Mr. Atwood contrived his
apparatus.

Of the mass moved. — In order to obtain an adequate idea
of the laws that are observed in the communication of mo-
tion, and observe the effects of the moving force, the inter-
ference of all other force should be prevented. The bodies
impelled should be conceived to exist in free space, and be
void of gravity or weight ; so that to a given substance va-
rious degrees of force may be applied. This indeed cannot
be effected in bodies falling freely near the earth's surface ;
we cannot abstract the natural gravity or weight from any
substance whatsoever ; for the same substance is always im-
pelled by the same force of gravity, which admits not of
increase or diminution.

Yet, this difficulty may be obviated by balancing two
equal weights, joined by a flexible line, which goes over a
pulley. The axle of the pulley must rest on wheels con-
structed for the purpose of diminishing friction.

The motive force of gravity being destroyed by the con-
trary and equal action of the weights, they will remain
quiescent till some force is applied to them. When any im-
pulse is communicated to them in a vertical direction, they
will afterwards be observed to describe equal spaces in
equal times, or will move uniformly ; and the velocity com-
municated will be precisely the same, as if the same impulse
had been impressed on a quantity of matter equal to the
two bodies existing in free space without gravity, due allow-
ance being made for the inertia of" the wheels.

Thus, in this instrument (Fig. 1*76, page 175), which is
constructed to illustrate this subject experimentally, there
are two equal weights, A, B, affixed to the extremity of a
very fine and flexible silk line. This line is stretched over a
brass wheel, abed, movable round a horizontal axis. The
two weights, A, B, being precisely equal, and acting against
each other, when the least weight is super-added to either,
it will preponderate.

When the weights, A, B, are set in motion by the action
of any weight, which Mr. Atwood called m, the sum of A
added to B, added to m, would constitute the whole mass
moved ; but then there is to be added the inertia of the
materials which must necessarily be used in the communica-

MOTION, MECHANICS, ETC. 177

tion of motion. These materials are: 1. The large wheel,
abed; 2. The four brass friction- wheels, on which the
axle of the wheel, abed, rests ; these wheels are used to
prevent the loss of motion, which would be occasioned by
the friction of the axle, if it revolved on an immovable sur-
face ; 3. The weight of the line ; but this is too inconsider-
able to have any sensible effect.

Of the resistance from the inertia of the pulleys. — If the
whole mass of the wheels were accumulated in the circum-
ference of the wheel, abed, its inertia would be truly
estimated by the quantity of matter moved. If their figures
were regular, and the density distributed uniformly in each,
mathematicians would furnish us with rules for finding a
weight, which, being accumulated uniformly in the circum-
ference, a b c d, would exert an inertia equal to that of the
wheels. But as the figures are wholly irregular, recourse
must be had to experiment for the discovery of such a
weight.

For this purpose a weight of thirty grains was affixed to
a silk line which did not weigh one-quarter of a grain ; this
line being wound round the wheel, the weight of thirty
grains, by descending from rest, communicated motion to
the wheel, and, by many trials, Avas observed to describe a
space of thirty-eight and a half inches in three seconds.
From these data we find the mass equivalent to the inertia
to be two ounces and three quarters. This is a mass equi-
valent to the inertia of the wheel, abed, and the friction-
wheels together.*

The resistance to motion, therefore, arising from the
wheel's incrtion will be the same as if it were absolutely re-
moved, and a mass of 2£ were accumulated in the circum-
ference of the wheel, abed.

This being premised, suspend the pieces, or brass boxes,
A, B, by a silk line passing over the wheel, abed, and
make them balance each other ; now, if I add any weight,

* Mr. Atwood proves in his work, t that the following formula
will give the required mass .£^=p — x, where p signifies the

weight, 30 gr. ; t the time, 3 seconds; d the space described by a
body in a second, 16 feet 1 inch, or 193 inches; s the space described
by the body, 38.5 inches ; and x the inertia sought.

That is in figures for the present case, 3 o M 9 M i 9—30 equal to
1323 grains, or 2 3-4 oz. 335

178 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

m, to A, so that it shall descend, the exact quantity of
matter moved will be ascertained, for it will be A added to
B, added to m, added to 2£ oz.

In order to avoid troublesome computations in adjusting
the quantities of matter moved, and the moving force, one-
quarter of an ounce is assumed as a standard weight of
convenient magnitude, to which all others are referred ; this
weight is called m. Now the inertia of the wheel, being 2f
oz., will be denoted by 11 m j A and B, the pieces or boxes
to which the different weights are applied, are each, together
with the hooks by which they are suspended, equal 1^ oz.
or 6 m. We have a variety of different weights, some of
which are equivalent to 4m, others to 2 m, some equal m,
and others to aliquot parts thereof.

If then we apply 19 m to each of the pieces, A B, these,
with those pieces, will each be equal 25 m, balancing them-
selves, and the whole mass will be 50 m, which being added
to II m, the inertia of the wheels, the whole mass will be
61 m j now add m to both A and B, and the whole mass
will be 63 m, perfectly in equilibrio and movable by the least
weight, added to either, setting aside the effect of friction,
in the same manner precisely as if the same weight or force
were applied to communicate motion to the mass 63 m, ex-
isting in a free space and without gravity.

Of the moving force. — As the natural weight,, or gravity,
of any given substance is constant, and the exact quantity
easily estimated, we shall apply a weight as a moving force ;
thus, when the system consists of a mass equal 63 m, I
apply a weight, m, to A, and it communicates motion to the
whole system ; the whole quantity of matter moved is 64
m; the moving force m, this gives us the force which ac-
celerates the descent of A, being ™m, or | part of the
accelerated force, by which the bodies descend freely to the
earth.

You see by this example, that the moving force may be
altered without altering the mass moved ; for, suppose the
three weights m, two of which are placed on A and one on
B, be removed, then A will balance B.

Now place the weights 3 m on A, and the moving force
will be 3 m, and the mass moved 64 as before, and the force
which accelerates the descent of A equal g|jj|.

To make the moving force 2m, remove the three weights
m, A and B will balance one another, and the whole weight

MOTION, MECHANICS, ETC. 179

will be 61 m ; add 1-2 m to A and 1-2 m to B, and the
mass moved will be 61 m r ; now place 2 m on A, and the
mass moved is 64 as before, whereof the force of accelera-
tion is equal to 1-32 part of the acceleration of gravity.

Of t/ie space described. — The body, A, descends, as you
perceive, in a vertical line, along the scale, C C, which is
about sixty-four inches long, and is graduated into inches
and tenths ; the scale is so adjusted as to be vertical, and
so placed that the descending weight may fall in the middle
of the stage D, fixed to receive it at the end of the descent ;
the beginning of the descent is estimated from O, on the
scale, when the bottom of A is level or even with 0 ; the
descent of A is terminated, when the bottom strikes the
stage ; the situation or distance of the stage may be varied
at pleasure within the range of the sixty-four inches.

Of the time of Motion. — The time of the motion is ob-
served by the beats of this pendulum, E, affixed to the
pillar, G, and which vibrates seconds. The number of
seconds is shown by the index and dial-plate above.

Many mechanical devices might be applied for letting the
weight, A, begin its descent at the instant of the beat of
the pendulum ; but it is simpler, and Mr. Atwood thinks
better, to let the bottom of the piece, or box, A, when even
with 0 on the scale, rest on a flat rod held in the hand
horizontally, its extremity being coincident with 0 ; by at-
tending to the beats of the pendulum, you may, with a little
practice, remove the rod which supports the box, at the
instant the pendulum beats, so that the descent of A shall
commence at the same instant.

Of the velocity acquired. — I have only now to show you
in what manner the velocity acquired by the descending
weight, A, at any given point of the space through which
it has descended, is made evident to the senses.

The velocity of A's descent being continually accelerated,
will be the same in no two points of the space described ;
this is occasioned by the constant action of the moving
force ; and since the velocity of A, at any instant, is mea-
sured by the space which would be described by it moving
uniformly for a given time, with the velocity it had acquired
at that instant, this measure cannot be experimentally ob-
tained, but by removing the force which caused the accele-
ration of the descending body.

To effect this, there are some weights or movino- forces in

180

form of bars or flat rods, m, to be laid on A ; there is also
a circular frame, H, to be fixed to the scale at any proper
height, in such manner that A will pass centrally through it ;
when A passes through this frame, it leaves the bar by
which it had been accelerated on the circular part of the
frame. After the moving force, m, has been intercepted at
the end of the given space or time, there will be no force
operating upon any part of the system to accelerate or re-
tard its motion, and consequently the instant m is removed,
A will proceed uniformly with the velocity it had acquired
that instant, and the velocity being uniform, will be mea-
sured by the space described in any convenient number of
seconds.

It may here be necessary to observe, that Mr. At wood
has clearly shown, that the weight of the line can have no
sensible effect on the experiments, for the inequality of the
motion occasioned by it does not amount to more than
-(fo^Tz °f a second, a quantity too small to be distinguished
by the senses.

The resistance of the air does not affect these experi-
ments; for, as the greatest velocity communicated in these
experiments does not exceed 26 inches in a second, and the
pieces A and B being only about If inch in diameter, the
resistance of the air can never increase the time of the de-
scent in so great a proportion as 240 to 241, and will be
therefore insensible in experiment.

The effects of friction are almost wholly removed by the
axis of the wheel, abed, acting on the four friction wheels,
e, f, g, h. If the weights, A and B, be balanced in perfect
equilibrio, and the whole mass consist of 63 m, a weight of
two grains, added to A or B, will communicate motion to
the whole, which shows how inconsiderable the friction is ;
in some cases, however, particularly in experiments on re-
tarded motion, the effects of friction become sensible, but
may be very readily and exactly removed by adding rather
less than two grains to the descending weight ; the weight
should be always less than what is sufficient to put the
whole in motion.

The space which bodies describe in one second, by falling
freely from rest, is 193 inches; but in the ensuing experi-
ments, the space is taken at 192 inches, which will be pro-
ductive of no error, in order to avoid fractions, which would
render the use of the instrument less easy and intelligible.

MOTION, MECHANICS, ETC. 181

The pendulum of the clock, which is fixed to the pillar
of the instrument, vibrates seconds ; it has only one wheel
which immediately acts on the pendulum : the small weight
which continues the pendulum's motion, after it has been
wound up, is half an hour in descending to the ground.
The clock will be sufficiently exact if it keep time with a
common well regulated clock for this half hour.

When the axis of the wheel, abed, has been adjusted
horizontal, let two equal weights, A and B, be suspended
from the extremities of a silk line of proper length, the
thickness of which is no greater than is just sufficient to
sustain the weights. When these weights are perfectly
quiescent, a small impulse being applied to either, in a ver-
tical direction, will set the whole in motion ; which will be
continued uniform till one of the boxes arrives at the ex-
tremity of the scale. When the box, A, is at the bottom
of the scale and quiescent, it must be observed whether the
middle line on the scale be everywhere exactly opposite to
the line sustaining A ; or, in other words, whether the line
in the middle of the scale be in the same vertical plane with
the line which sustains A. If it be not, the lower extremity
of the scale must be moved along the arm of the base until
the adjustment is correct. It is also to be observed, whether
the line be everywhere at equal perpendicular distances from
the middle line on the scale : if it be not, the lower extremity
of the scale must be removed further from, or nearer to the
silk line, until the distances are everywhere equal. The
middle line on the scale will now be vertical, and the circular
frame must be so constructed, that the box, A, may pass
centrally through it, when the adjustments are correct.

In letting the box, A, begin to descend at any beat of the
pendulum, the observer must not wait until he hears the
beat, at which he intends A's descent shall begin ; for, in
this case, A's descent will always commence too late ; the
proper method is to attend to the beats of the pendulum,
until an exact idea of their succession is obtained : then the
extremity of the rod being withdrawn from the bottom of
the box, A, directly downwards at the instant of any beat,
the descent will commence at the same instant.

Having now sufficiently explained the instrument, we shall
proceed to the construction of some experiments with it.

Let two equal weights, A and B, be suspended by a line,
joining them, and going over a fixed pulley. If any weight
13

182

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

be added to them, it will preponderate, and in its descent will
describe sjiaces which are as the squares of the times of falling
from rest.

The equal weights are, in the present case, each equal
26 m, and the additional weight applied as a force to com-
municate motion m. Then the mass moved is m -f 52 m +
the inertia of the wheels 11 m, making in all 64 m. Now it
will be seen, that the preponderating weight descending
from quiescence during 1, 2,3, seconds, describes in the first
second, 3 inches ; in two seconds, 3 X 4 or 12 inches; in
three seconds 3X9 or 27 inches ; the spaces being respec-
tively as the squares of the time of motion.

To prove this, fix the stage to 3 on the graduated scale,
bring the under surface of the piece, A, to coincide with o, on
the scale, and let it fall at a beat of the pendulum, and you
will find it strike the stage when the pendulum beats again ;
it has done so, having passed through three inches in one
second. We shall now place the stage at 12 inches, and the
weight will strike it exactly at the second second ; when
placed at 27, the stroke of the weight will coincide with the
third second.

We subjoin a table of some experiments of the same kind,
which will rivet the theory more perfectly on the mind, and
render it more easy of application to particular cases. Let
A hold 36.3-4?^; B, 36. 1-4 m. The spaces described, &c.
will be as in the following table.

A TABLE.

Moving
force.

Mass Accelerating
moved. force.

Times of motion
in seconds.

Spaces described from rest
estimated in inches.

1

1

2

4

3

9

lm

96m

_JL_

4

16

5

25

6

36

7

49

8

64

If different forces be successively applied to accelerate
equal quantities of matter from quiescence, the spaces describ-
ed in any given time will be in the same proportion with the
force*.

MOTION, MECHANICS, ETC. 183

If any body, equal to 64 m, fall freely, or be acted upon
by its own natural weight, it will describe 192 inches in the
first second of its fall ; but if the same mass be impelled by
only _i_ of its accelerating force, or I m, it will describe only
a 64th part of the former space ; that is, only three inches,
a proportional effect.

To prove this, let A and B be each made equal to 25 m,
then will A and B be equal to 50 m ; to this add 1 1 for the
inertia of the wheels, and we have 61 m ; now put 2 m on
A, and 1 m on B, and the mass moved will be 64 m, and
the moving force 1 m.

Set the stage to three inches, and let the weight descend
as before, and you will find it strike the stage at the first
second.

If the same force impel different quantities of matter for any
given time, the spaces described from rest will be inversely as
the quantities of matter moved.

Let the force be m, and the mass 64 m, then the space
described, during one second, will be three inches.

Let the force be m, and the mass 32 m, then the space
described in the same time will be six inches.

If the, force be increased or diminished in the same propor-
tion with the mass moved, the spaces described from rest in the
same time, ivill be equal.

Let m, 2 m, and 4 m, be the moving forces which impel
the quantities of 32 m, 64 m, 128 m, respectively ; then m
will impel 32m through six inches in a second, 2 m will im-
pel 64 m, and 4 m will impel 128 m through the same space
in the same time.

From hence you may infer, that when different quantities
of matter describe equal spaces in equal times, being accele-
rated from quiescence, the forces must be in the same pro-
portion with the quantity of matter moved.

If a body be moved from quiescence during any given time,
it will, at the end of that time, have acquired such a velocity,
as will, if continued uniform, carry it through double the space
which the body has already described to acquire that velocity.

Let the mass moved be 64 m, the force, m , but let m,
which is applied to A, as the moving force, be one of the
flat rods, m, Fig. 176. Place the circular frame so that A
may, in descending, pass through it, and its height be such,
that the instant the lower surface of A arrives at 12 inches,
the rod, m, may be intercepted by the surface of the circular

184 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

frame, and thereby be prevented from the further accelera-
tion of the system. Let the other stage be set at 36 inches,
that is, 24 from the circular frame.

Now, let the weight begin to descend from o, on the
scale at any beat of the pendulum ; at the end of the second
beat, you will hear the rod strike the circular frame, having
described twelve inches with a uniformly accelerated motion ;
and at the fourth beat of the pendulum, it will strike against
the square stage at 36, having described 24 inches with a
uniform motion.

If the same force act on the same mass for different times,
one second, two seconds, and three seconds, the velocities gene-
rated will then be six inches, 6x2 inches, and 6x3 inches in a
second respectively, being in the same proportion with the times
wherein the given force acts.

Set the circular frame to three inches, and the stage to
nine inches, let the mass moved be 64 m, the moving force,
m ; the weight, A, beginning its descent at any beat of the
pendulum, the rod will strike the circular frame at the next
beat : here the rod is removed, and A describes the next
six inches uniformly in one second, striking the stage at nine
at the second beat. By trying the apparatus in other in-
stances, you will constantly find the experiments coinciding
with theory.

These experiments show, that if the force by which bodies
are accelerated be the same, the velocities generated will
be in the same proportion as the times wherein the given
force acts.

If a body be moved from rest through the same space by
different forces, the velocities generated will be in a subdupli-
cate ratio of the forces.

Let the mass be 64 m, and the force m,— you will find
the velocity acquired in describing twelve inches in two
seconds, will, when the force is removed, carry it through
twelve inches in one second. Now, let the mass be 64 m,
and the force 4 m, and you will find that the body, in de-
scribing twelve inches, will acquire a velocity of twenty-four
inches, being in the ratio of 1 to 2 ; whereas the accelerating
forces are in the ratio of 1 to 4.

If different quantities of matter be impelled through the
same space, and acquire the same velocity, the moving forces
must be in the same ratio as the quantities of matter moved.

Let the quantities of matter be 64 m and 48 m, the space

MOTION, MECHANICS, ETC.

185

twelve inches, — the moving forces must be as 4 to 3. The
following experiments will illustrate this truth.

Moving

Quant-ties of

Accelerating ' Spaces described in

Velocities acquired in

forces.

matter.

forces.

inches.

inches per second.

in

64 m

eV

12

12

3m

2
3m

96 m

eV

12

12

T

48 m

eV

12

12

You may infer, from the two last sets of experiments,
that the moving forces, which impel bodies through the
same spaces, are in the joint ratios of the quantities of
matter moved, and the squares of the velocities generated.

If a given quantity of matter be impelled from rest through
different spaces by tlie action of the same force, the velocities
generated will be in a subduplicate ratio of the spaces described.

Let the quantity of matter be 64 m, the force m, the
spaces 3 inches and 2V inches, — the velocities will be in the
ratio of 1 to 3 ; for it will descend in the first experiment
through six inches in a second ; in the next you will find it
go through 18 inches in a second. Now the spaces are 3
and 27, or as 1 to 9 ; the velocities acquired as 6 to 18, or
as 1 to 3.

Experiment* on uniformly retarded Motion. — The laws
observed during the motion of uniformly accelerated bodies,
having been made evident to the senses by the preceding
experiments, I shall now proceed to illustrate the properties
of uniformly retarded motion.

When a body is thrown perpendicularly upwards from
the earth's surface, it is continually resisted by a force
which is equal to the body's weight ; and the weights of all
substances being proportional to the quantity of matter they
contain, it follows, that the force which retards the perpen-
dicular ascent of any body, being measured by its weight
divided by the ascending mass, is the same, being such as
destroys a velocity of 32£ feet in each second of the body's
motion. But in order to illustrate, by experiment, the
general laws according to which bodies are retarded by the
action of constant forces, such methods should be made use
of as will enable us to apply different resisting forces to the
same mass of matter, and the same resisting force to differ-

186 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

ent masses of matter, both of which conditions will be satis-
fied by the instrument now before you.

A resisting force is to be understood as conveying pre-
cisely the same idea as the term moving force ; except so
far as regards the directions in which those forces act in re-
spect to the body's motion, these directions being contrary
to each other.

If equal quantities of matter be projected in free space,
with any given velocity, and be resisted by different but in-
variable forces, the spaces described before the whole mo-
tion is destroyed, will be inversely as the resisting forces.

Let the mass projected be 61 m, with a velocity of 18
inches in a second, and let it be resisted successively by the
forces m,2m,3 m ; the spaces described before the motion
of the body is destroyed will be ^ -^-fj ¥| ¥ ; these spaces
being in the inverse proportion of the resisting forces.

Make A equal 24 m, B equal 25^ m ; apply to the up-
per surface of A two rods, each equal to m ; then will the
weight, A, preponderate and descend by the action of a
moving force equal m, the whole mass moved being equal
to 63 m. Set the circular frame to 26.44 ; then the weight,
A, by describing from rest the space 26.44 inches, will
acquire a velocity = V ^4+L93-+26.44^ equai to 18 inches
in a second ; and at that instant the two rods, each equal to
m, being removed, the weight will continue to descend with
a uniformly retarded motion, which will be precisely the
same as if a mass of 61 m were projected with a velocity
of 18 inches in a second, in free space, and a force of resist-
ance equal to m were opposed to its motion; wherefore A,
with the other parts of the system, will lose its motion

gradually, and will describe a space equal to .' ^ 6 1 = 25.6
inches before its motion be entirely destroyed. You will,
therefore, have to descend as low as 52 inches, before it
begins to ascend by the superior weight of B.

If any body, moving in a free space uniformly, be resisted
by a constant force, for any given time less than tJiat in which
the whole motion would be destroyed, the space described will
be the difference between the space which measures the initial
velocity of motion, multiplied into a number expressing the
given time, and that space which the body would describe, if
accelerated, during the given time, from quiescence, by a force
equal to that of resistance.

MOTION, MECHANICS, ETC. 187

Let a mass, 63±m, be projected with a velocity of 11.877
inches in a second ; if it be resisted by a force equal to | m,
it will describe 21.95 inches in three seconds. To this end,
make A equal 2G m, and B equal 26^ m, and apply a flat
rod, 1^ m, to the upper surface of A ; set the circular
frame to 11.877 on the scale, then will A descend, the
moving force being m, and the mass moved equal to 65 m.
When it has described 11.877 inches, it will have acquired
a velocity of 11.877 inches in a second ; and the rod being
at that time intercepted, A will begin to descend with a
uniformly retarded motion, and will strike the square stage
set at 33.83, at the fifth beat of the pendulum, and thus
describe 21.95 inches in three seconds.

For the account of various other useful and scientific ex-
periments, the reader had best consult the treatise of Mr.
At wood.

This instrument has many other uses, which it is not
necessary to describe particularly here ; such as, The ex-
perimental estimation of the velocities communicated by the
impact of bodies, elastic and non-elastic ; The quantities of
resistance opposed by fluids, as well as for various other
purposes ; The motion of bodies, resisted by constant forces,
are reduced to experiment, by means of this instrument, with
as great ease and precision as the properties of bodies uni-
formly accelerated ; and, The verifying practically the pro-
perties of rotary motion. The two last are clearly shown
in Mr. Atwood's work. This very useful and illustrative
instrument requires to be well made, and nicely adjusted.

The wheels and their mahogany bases can be separated
from their stand, and the various weights and other appa-
ratus, the scales, C, C : the ring, H ; the stage, D ; the
pillar, G ; and clock, E, are also made so as to be separated
and packed in a portable and convenient manner.

Price, with clock, $100.

AIR PUMPS AND APPARATUS,

IMPROVED LEVER AIR PUMP.

THIS elegant instrument (Fig. 17 7, opposite page), mounted
on a strong and highly polished frame, or table, made of
mahogany or rosewood, consists of two rectangular boards
two inches thick, twenty-seven inches long, and seventeen
inches wide ; supported twenty-four inches apart by four
hollow pillars, and connected together by iron rods secured
in the legs beneath, and having brass knobs at the top of
the frame ; thus binding the whole strongly together, and
affording facilities for separating the parts readily. The top
of the frame stands at thirty-nine inches from the floor,
which is the most convenient height for use. The cylinder,
or pump barrel, is screwed to its cap and base by large po-
lished steel screws, and is of heavy and highly polished
brass, securely bolted to the bottom board of the table. The
piston rod is of steel, working through a packing box, air
tight, in the cap of the cylinder, projecting above the upper
board and moving in a socket attached to the frame, which
has a square opening for this and the parallel motion, which
is connected with the piston rod and end of the lever. The
lever is of wrought iron, polished or handsomely japanned,
is three feet long, and supported by a steel axle moving in
two stout brass sockets, firmly bolted to the table ; at the
end of the lever is a turned handle. The receiver plate is
truly ground, and made of brass, or stout glass set in brass
mounting ; in the centre of the plate there is the usual
screw by which apparatus is connected ; beneath which a
brass connecting pipe having a stop-cock, passes to the
bottom board of the table, where it is terminated in a socket,
having a pipe running lengthwise with the bottom board of

AIR PUMPS AND APPARATUS.
Fig. 177.

18ft

190 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

the table, and connecting with the base of the pump barrel,
which is perforated, and the channel terminated by a valve
opening upwards. The piston and cap of the pump barrel
also have valves opening upwards ; the one on the cap hav-
ing a bent pipe ground into the cover of the valve, for con-
veying the oil driven over by the action of the pump into an
oil box which is attached under the frame, and may be
slided out to empty of oil. On the connecting pipe between
the cylinder and socket, there is a projection, with aperture,
having a screw the same size as that of the receiver plate,
and having a large milled-head screw to close it, and where
occasionally connexion may be made with the gauge, appa-
ratus, &c. There is from the under part of the receiver
plate, and running lengthwise on the top of the frame nearly
to the end, a brass pipe terminating in a brass cap, with
screw, to which a large stop-cock is attached, supporting a
mercury gauge. The gauge consists of a glass tube bent in
an U form, hermetically sealed at one end, which tube, and
a small portion of the bottom of the other, is filled with
mercury ; the tube is attached to a silver scale, graduated
to inches, and tenths thereof, and is about eight or nine
inches long. The scale and tube are secured within a stout
glass shade, which is cemented by a brass cap fitting the
large stop-cock as above.

A long barometer gauge sometimes accompanies the pump,
consisting of a strong tube, 33 inches in length, open at both
ends, having a reservoir of mercury at the bottom, and at-
tached above to the under side of the cap supporting the
short gauge. The scale is divided into inches and tenths.
This gauge, owing to the great length of the tube, requires
great care in using, as, by an accident, the mercury may be
drawn into the pump, materially injuring it thereby. On
this account it is most usually dispensed with. The stop-
cock in the connecting pipe is to close the communication
between the receiver and pump-barrels, and that beneath
the gauge, to close the communication between the gauge and
the receiver. The length of the cylinder is nearly one foot,
the diameter 3£ inches, the plate 10 inches. Oil should be
occasionally supplied by pouring that which is perfectly
clean into the aperture in the receiver-plate, and also into the
cup over the packing-box, through which the piston moves.
The plate and receivers are ground true, and require but a
little tallow or oil to prevent the scratching of the two sur-

AIR PUMPS AND APPARATUS.

191

faces. In experiments requiring accurate exhaustion, care
should be taken that the receiver and various parts of the
pump be free from moisture, the vapor of which arising
would form an atmosphere, which would continue to rise as
long as any moisture remained. The operator should be pro-
vided with a number of receivers, of various kinds and sizes,
some open at top, having a brass plate with sliding rod ;
others with closed top, having a knob ; also a few glass jars,
for supporting fruit, &c.

Price, $70, $75, and $85, according to style and finish.

French Table Air Pump.— (Fig. 178, as below.)— This

192 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

instrument in its general arrangement is the same as the
usual table air pump, but made in a more elegant style,
being framed wholly of brass and highly finished. Between
the pump barrels and the receiver plate, there is a large
stop-cock, which, when closed, prevents any leakage from
the various joints into the receiver. The mercurial gauge
has a metallic scale, and is placed within a glass shade, and
supported on a large stop-cock, by which communication or
not may be made with the receiver.

Price, largest size, $75.00.
" smaller " $50.00.

Large Double Barrel Air Pump. — (Fig. IT 9, as below),

AIR PUMPS AND APPARATUS. 193

represents the usual style of the large size, double barrel,
table air pump, and consists of two barrels of brass, accu-
rately bored, and finished of a uniform calibre. These, with
their bases, are firmly held in a perpendicular situation to
the square mahogany base, by the mahogany head of the
air pump, which is pressed upon them by screws at the top
of the two brass pillars, one of which is placed each side
of the barrels. In the centre of the base there is a true
ground receiver plate, having in the centre a hole, with
screw, for the attaching of any apparatus, and a concealed
channel communicating with the point, where a screw is
fixed to let in air occasionally. From the above mentioned
channel there is a perforation at right angles to the former,
going to the centre of the basis of each barrel ; at each of
these centres a valve is placed, opening upwards to admit
the air into the barrels ; there is a piston so fitted to each
barrel, that the air cannot pass between it and the sides of
the barrel ; to each piston there is a valve opening upwards,
through which the air in the lower part of the barrel mav
escape into the common air ; the pistons are also connected
to a rack, and are raised or depressed by a handle, the lower
part of which is fixed to the axis of a cog-wheel, whose
teeth take into the rack ; one piston is raised, and the other
depressed by the same turn of the handle.

Two barrels are advantageous, not only as performing the
work quickly, but also because the weight of the atmosphere,
pressing upon the rising piston, is counter-balanced by the
same weight pressing upon the other piston descending.

The operation of air depends on the elasticity thereof.
When either of the pistons is drawn upwards, a vacuum is
left behind it, and the pressure being thus removed from the
valve in the bottom of the barrels, this valve will be opened
by the elasticity of the air in the receiver ; and the air,
rushing through it, will be uniformly diffused in the receiver,
the canal connecting this with the lower valve, and in the
barrel. But upon depressing the piston, the valve at the
bottom of the barrel will be closed, and the air therein
being condensed, will open the valve in the piston and escape ;
thus the air contained in the barrel is discharged, and, by
every turn of the winch, a quantity of air equal to the con-
tents of the barrel, and equally dense with that in the re-
ceiver, is exhausted.

Behind the large receiver, there is a small plate for sus-

194

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

taining a small receiver, from the hole at the centre of this
plate there is a canal communicating with that which goes
from the large receiver to the barrels ; under this receiver is
a small tube filled with mercury freed from air, this is called
the short barometer-gauge. As the air is taken out of the
small receiver at the same time that it is taken from the larger
one, the descent of the mercury in the tube will point out
the degree of rarefaction in the receivers ; the mercury does
not begin to descend in this tube till near three-fourths of
the air have been extracted ; and the air is said to be as
many times rarer than the atmosphere, as the column of
mercury sustained in this tube is less than that of the mer-
cury, at that time, in the common barometer.

Price, $40.00 and $45.00.

Double Barrel Air Pump. — (Fig. 180, as below.)— This
cut is a representation of the usual style of the double barrel
air pump described, with the omission of the gauge, and
being made of a smaller size. Price, $22.50 and $25.00.

Fig. 180.

Pike's Improved Double Barrel Air Pump. — (Fig. 181,
page 195.) — This instrument, in its general construction,
corresponds to the preceding one described (Fig. 179),
but of a larger and more elegant finish, the frame being sub-
stantially and elegantly finished, of rosewood or mahogany
highly polished, conveniently mounted from the floor on
four feet, and having the plate raised on a stage supported
on four pillars, beneath which the gauge is attached, which
is the same as described in the large lever pumps ; the

AIR PUMPS AND APPARATUS.
Fig. 181.

195

pump is conveniently worked by a large double lever
handle ; the barrels of the pump are thirteen inches long,
two and a half inches internal diameter ; the whole with
the receiver standing about four feet from the floor.

Price, with mahogany frame, $65.00.
" " rosewood " $70.00.

Single Barrel Air Pump. — (Fig. 182, next page.) — This
pump consists of a tube, or barrel of brass with equal bore,
having a piston moving by means of a rod and handle ; the
barrel is attached to its base by a screw, which is firmly
clamped to the square mahogany table supporting the
whole ; in the centre of the table there is a receiver plate,

IDG

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

Fis-182- truly ground, having in the

centre a screw to fit the stop-
cocks of the usual apparatus
accompanying these instru-
ments, and beneath a pipe
connecting with the brass
base of the barrel of the
pump, having a valve open-
ing upwards, there being one
also in the piston opening
the same way ; the action is
the same as described in the
large double barrel air pump.
Suppose the receiver to be
placed on the plate, care being taken that it is free from
dust and grit, and a small quantity of oil rubbed thereon,
draw the handle up, and a vacuum will be formed under-
neath the piston. The air then in the receiver will, by its
elasticity, force against the valve at the bottom of the barrel,
and rush up to fill the vacant space. When the piston is
forced down again, it compresses the air beneath it, which
closes the valve at bottom, and at the same time opens the
valve which is in the piston itself, and the compressed air
thereby escapes ; thus a quantity of air equal to the capacity
of the barrel is got rid of — a second lift will withdraw a
second portion, and so the operation may be continued at
pleasure. Price, small size, with receiver, $7.00.

Fi 183 " medium size> $9.00.

This cut (Fig. 183)
represents a larger
size single barrel
air pump and re-
ceiver, having in
the drawing the
barrel cut away,
to show the piston
and valves ; the
construction is the
same as the one
above described.
Price, with re-
ceiver, $12.

AIR PUMPS AND APPARATUS.
Fig. 181.

197

Pike's Improved Single Barrel Air Pump with raised
plate. — This powerful and simple arrangement of the large
single barrel air pump, is represented in Fig. 184, as above.
The barrel is of brass, fourteen inches long and two inches
diameter, having a broad brass base, firmly bolted to the
frame by screws beneath. The piston is worked by standing
with the feet on the frame and grasping the handle with
both hands, by which means a much larger piston may be

198

BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

worked than in the ordinary construction, and being also
less fatiguing to the operator. The pump plate is support-
ed by four mahogany pillars, on a table elevated about
twenty-eight inches. The connexion between the pump-
plate and the cylinder is by a brass pipe, having a stop-cock
for shutting off the communication when required. The
frame is of polished mahogany ; the base twenty-two inches
long and fourteen inches wide. Price, $20.00.

Condensing Apparatus. — The condenser is a syringe by
which a large quantity of air may be forced into a given
space. It is constructed on the same principle as the air
pump ; only the valves are disposed in the contrary order,
that is to open inward instead of outward.

Fig. 185 represents a syringe fur-
Fig. 185. nished with a handle, moving a solid
piston air-tightly in a cylindrical
barrel, which barrel is furnished with
a valve at the foot, and either a
small hole near the top of the barrel,
or else the piston, instead of being
solid, is perforated, and has a valve
also opening downwards. It will be
evident, that working the handle up
and down will alternately fill the
barrel with air from the upper part,
and condense it into any vessel at-
tached to the screw at the foot.

The air vessel is a strong globular
shaped glass vessel, supported on a
foot, having a neck to which a brass
cap with stop -cock is fitted ; to the
stop-cock is fastened a pipe, reaching
nearly to the bottom of the vessel ;
to the upper screw of the stop-cock
is attached a tube, and a variety of
jets ; one a plain jet, one a globular
jet, pierced with many holes, another flat on top pierced
with a cross ; also, there is usually accompanying them, a
revolving jet, as represented in the cut, which may be moved
either for air or water. To use, the vessel is about half
filled with water, and the condensing syringe being screwed
to the tube, and the stop-cock opened, air is to be forced

AIR PUMPS AND APPARATUS.

199

into the bottle, which rising through the water, will by its
density press strongly on the surface of that liquid ; then
after turning the stop-cock the syringe is to be removed,
and a small jet-pipe being fitted to the tube, the stop-cock
is to be opened, and the elasticity of the condensed air in
the bottle, will drive up the liquid in a jet.

Price, $10.00.

" revolving jet, $2.00.

Air Condensing Apparatus, with Fis- 186-

Copper Chamber. — (Fig. 186.) —
This condensing apparatus consists
of a brass condensing pump or
syringe, nine inches long, and one
and a half inch diameter. A cop-
per chamber or vessel for contain-
ing the air, having a stop -cock
with screws on the top, with a
tube descending nearly to the
bottom, and also a stop -cock on
the side near the top, there being
a tube connected with this aper-
ture descending nearly to the bot-
tom. To the stop-cocks are at-
tached several jets ; a straight jet,
a compound jet, and a revolving
jet. To use this apparatus fill
the chamber about half full of
water and screw on the stop -cock,
connect the condensing pump,
and condense the air therein, then
turn the stop-cock to confine the
air, and removing the pump, screw on the straight jet ; on
turning the cock, the pressure of the air within the chamber
will force the water out in a stream with great force. If
the compound jet be used, it will produce a great number
of streams, and pour out with great beauty. Also the re-
volving jet will form a pleasjng circle in the air, as the water
is rapidly forced out. All these jets may also be used on
the stop-cock at the side of the chamber.

The long brass cylinder, or gun-barrel, represented in the
cut, and having a screw fitting the stop -cocks, is designed
to illustrate the air gun. To use, screw the barrel to the

200

BENJ. PIKE S, JR., DESCRIPTIVPJ CATALOGUE.

stop-cock attached to the side of the chamber, having pre-
viously condensed sufficient air therein, place a bullet, pea,
or cork ball within the barrel, and quickly open the stop-
cock ; the ball will be thrown violently out of the barrel.

Price, of the whole apparatus, $12.00.
Fig. is/. " condenser only, $5.00.

smaller size, $4.00.

Lever Condenser on Frame. —
In this instrument (Fig. 387),
the barrel of the condenser is
sunk into the air chamber,
which is supported on the un-
der side of the frame by four
stout rods passing through the
frame ; and also .a round board
{it the bottom of the air cham-
ber clamping them firmly to-
gether by means of screw
m;ts. The piston is worked
by a lever and arm fastened to
the frame ; on one side of the
air chamber is a stop-cock.
Price, $20.00.

Fig. 188.

Swelled Receivers for the Air Pump. — (Fig. 188, as above.)
— The receivers of the air pump are large glass vessels
•placed on the pump plate and over an orifice, in order to be
exhausted of air ; being thus called from their being the re-
cipients of those things on which the experiments are made.

AIR PUMPS AND APPARATUS.

201

In order that the contact with the plate of the pump may
be air tight, the bottoms of the receivers are ground perfectly
true. They are made of various shapes ; straight sides and
swelled, open top and with knob.

Price, 4 in. $0.75; 5 in. $1.00; 6 in. $1.25.

7 in. $1.50 ; 8 in. $1.75 ; 9 in. $2.00.

10 in. $2.50; 12 in. $4.00.

Low Receivers for the Air Pump. — Fi=- 189-

(Fig. 189.) — These receivers are used
where the articles placed under them do
not occupy much height, and consequent-
ly can be exhausted quicker than where
higher ones are used.

Price, 5 in. $0.75 ; 6 in. $1.00.
7 in. $1.37; 8 in. $1.75.

The Gallows Connector.— (Fig. 190.)—
This convenient apparatus is used in con-
nexion with the flexible tube, for con-
necting apparatus with the air pump that
otherwise could not so conveniently be at-
tached. The lower part of the ball has a
socket entering the gallows, which, by
loosening the screw over the ball, may be
readily disconnected. The connexions are
made with male screws ; a double female
connector is sometimes attached, where a
female screw is required.

Hand Glass.— This cut (Fig. 191) re-
presents a swelled glass receiver, about
5 inches in diameter, open at both ends,
and ground perfectly true and flat ; the
one end is about 4 inches in the aperture,
and the other two inches. Set the large-
end on the plate of the air-pump, and
place the hand on the small end, so as to
cover the glass ; then begin to exhaust,
and you will feel the pressure of the air ; for the air being
taken from under your hand out of the glass, the external
air will press your hand to the glass, so that you can scarce
move it. Upon letting in the air it will be loosened again.

Price, $1.50.

Fig. 191.

202 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

The spring of the air in your flesh is also shown by this ex-
periment, the flesh of the inside of your hand swelling down-
wards within the exhausted glass. Price, 75 cents.

The Bladder Glass. — Cover the large end
of the last described receiver (Fig. 192) with
a piece of wet bladder, and leave it to dry.
After it is perfectly dry place the open end
on the pump-plate, and exhaust the interior
air till the weight of the air on the bladder
causes it to burst with a loud report. If,
instead of the bladder, a piece of sheet india
rubber is used, it will expand and fill the glass vessel.

Price, 75 cents.

Fig. 193. Bladder Glass with Cap and Stop- Cock.

— (Fig- 193.) — This arrangement of the
bladder glass when attached to a flexible
tube, and connected with the air pump,
admits of its being turned in any direction,
and may be seen by a large audience to
more advantage than when used on the
pump plate. It may also be used to show
the expansion of air, by closing the stop-
cock, and placing under a receiver, when
the bladder will be forced out, and if the
exhaustion be continued, it will be broken

by the expansive force of the air within the glass.

The experiment may be varied by using a piece of sheet

india rubber, which will not be broken, but swell out, or

be drawn in, as the instrument may be used.

Price, $2.00,

Fig. 194. Apple Cutler. — (Fig. 194.) — This consists of

a metallic cylinder, or cone, open at each end,
having a base ground true, and fitting air tight
the pump plate, and at its upper end a sharp
edge. To use, place the cone on the air pump,
an apple on the top of the cone, and exhaust
the air ; the pressure of the air on the outside
of the apple will cause the apple to be cut, and
forced through the opening.

Price, $1.50.

AIR PUMPS AND APPARATUS.

203

Pressure Glass. — (Fig. 195.) — This instrument
consists of a glass globe, about three and a half
inches in diameter, with a neck inverted in a glass
vessel of about the same size, which is to be
nearly filled with water, and placed under the re-
ceiver of the air pump. As the receiver is ex-
hausted, bubbles of air pass out of the globe
through the water and escape away, but as soon
as the pressure is restored the water is forced out
of the lower vessel upwards into the globe. The
instrument may now be used to illustrate the expansion of
air, by again exhausting the receiver, when the small bubble
of air left at the top of the last experiment, will expand and
fill the whole globe. Price, 75cts, larger size, $1.00.

Fig. 196.

Bolt Head Experiment (Fig. 196) consists
of a glass globe of four or five inches in di-
ameter, with neck about thirty inches long,
having cemented on the neck a plate fitting
the open top air pump receiver. To use, the
plate is set on the open top receiver with the
end of the neck immersed in a jar of water,
which, to render the experiment more con-
spicuous, is usually colored red or blue ; on
exhausting the air from the receiver, the air
in the globe is expanded and escapes from
the neck, and is seen bubbling through the
water. On returning the air to the receiver,
it cannot enter the globe, but pressing on the
water forces it up the neck into the globe,
occupying the place of the air that escaped
by its expansion, and showing the quantity.
Price, $1.00. Glass jar, 25c. J

Magdeburg Hemisphere. — (Fig. 197, next

age). — This instrument consists of two hol-

ow hemispheres of brass, which are made to
fit upon each other by a ground joint, ren-
dered air tight by a little oil. Having screw-
ed off the handle, put both the hemispheres together, and
screw them into the pump-plate, and turn the cock so that
the pipe may be open all the way into the cavity of the
hemispheres ; then exhaust the air out of them, and turn

204 BKNJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 197. the Cock ; unscrew the hemispheres from the
pump, and having put on the handle, let two
strong men try to pull the hemispheres asunder
by the rings, which they will find it difficult to
do ; for if the diameter of the hemispheres be
four inches, they will be pressed together by the
external air with a force equal to 190 pounds.

We have recently improved this article by
manufacturing them of iron, which is not so
liable as brass to be bent by an accidental
blow.

Price, 3^ in. brass, $4.00 ; 4| in. brass, $6.00.
" 3^ in. iron, $4.00 ; 4£ in. iron, $5.00.

Lever and Stand for weighing a column of air. — Fig. 198
consists of a strong base, having a short pillar serving as the
fulcrum of a lever fixed therein ; on the short end of the
lever the handles of the hemispheres are supported, the
stop-cock being screwed to the base. This arrangement is

Fig 198.

designed to prove the pressure of the air on the hemispheres
to be about fifteen pounds on every square inch. If the
diameter of the hemispheres be four inches, the area is
twelve and a half inches, which multiplied by fifteen gives
187 Ibs. ; the power requisite to separate them when ex-
hausted, as shown by the lever. The exhausted hemispheres
will of themselves come asunder under an exhausted receiver.

Price, $5.00.

Spouting Tube. — Fig. 199 consists of a long glass tube,
having a brass cup and stop-cock. To use, exhaust the air
by the air-pump, and turn the stop-cock ; then plunge the
end of the cock in water, and open the cock, when the water
will violently rush in, and nearly fill the tube.

Price, $2.50.

AIR PUMPS AND APPARATUS.

205

Fig. 231

Fig. 2 '2.

The Fountain in Vacua. — (Fig. 200, as above.) — The
fountain consists of a tall receiver, of glass, about five inches
wide in the swell, but contracted at the top, and cemented
by a neck at the lower end to a brass cap, having within a
jet pipe attached to a stop-cock, which screws into the cap ;
the whole is mounted on a stand when not in use. To use,
the fountain is connected with the air pump by means of
the stop-cock and tube ; after the air is exhausted out of the
receiver, the cock is shut to prevent its return ; then the
whole is unscrewed from the plate of the receiver, and the
lower end of the tube is immersed in a vessel of water ; on
opening the stop-cock, the pressure of the atmosphere on
the surface of the water in the vessel having no counterpoise
from the interior of the cylinder, forces up the fluid through
the jet-pipe with considerable velocity, which forms a pleas-
ing jet-d'eau, or fountain in vacuo.

Price, $4.50 ; larger, $5.00.

206 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Expansion Fountain. — (Fig. 201, page 205.) — This appa-
ratus consists of a glass globe with feet, having a cap, stop-
cock, and jet, reaching down to the bottom, and an open
vessel with cap screwed to the upper end of the cock. To
use, the lower vessel is nearly filled with water, and the
stop and jet screwed in and placed on the air pump under
a receiver ; as you exhaust the air from the receiver, the
air in the upper part of the globe is expanded, and the
liquid forced through the jet into the upper vessel : in return
ing the air to the receiver, the water descends.

Price, $3.50.

Three Globe Fountain, by Elasticity. — (Fig. 202, page 205.)
— This consists of a double globe on a foot, with open
end, having a jet pipe extending from the bottom of the
lower globe to the top of the second, and another globe
with a neck covering the jet pipe. To use, fill the lower
globe nearly full of water, or a colored liquid, screw in the
jet pipe, and cover it with the upper globe ; place it on the
air pump and cover with a receiver ; exhaust the air, which
removes the pressure from the upper vessels and expands
the air in the lower globe, forcing the liquid up the pipe
into the upper vessel, and from thence falling into the second.
Return the air to the receiver, and the water is forced into
the upper vessel, and from thence again into the lower one.

Price, $2.50.

Fig'21'3- Lungs Glass.— (Fig. 203.)— An instru-

ment or apparatus used with the air pump,
intended to prove the elasticity of the air.
It consists of a glass globe of about four
inches diameter, with a foot to it, and also a
brass cap at the top ; within the glass is a
small bladder, tied to a short tube, which
is attached to the cap, and projects an inch
or so within the glass. This tube passes
out at the top, and is terminated by a small
orifice. The lungs glass is placed under the
receiver of the air pump, and as the air is
exhausted the bladder collapses ; being admitted it expands
again, showing the exact action of the animal lungs in re-
spiration. Price, $2.00.

AIR PUMPS AND APPARATUS.

207

Fig. 204.

Guinea and Feather Experiment. — (Fig. 204.) — This in-
strument consists of a tall glass receiver, open at the bottom,
and having the top closed, so as to be air-tight, by a brass
cap or cover, through which passes a wire, fitting close, but
capable of being turned without admitting the air. The
lower end of the wire is made to support a small stage, the
two sides of which will fall and separate, when the wire is
turned in a transverse direction. Then, the stage being fixed,
a sovereign and a feather, or any two small bodies differing
greatly in their comparative weight, may be laid on the stage,
and the bell-glass, or, as it is called, receiver, being placed
on the plate of an air pump, must be
exhausted of the air it contained. This
being done, if the two bodies are
made to fall by turning the wire, it
will be found that they will both strike
the plate of the air pump beneath
them at the same point of time.

Price, $10.00.

Guinea and Feather Tube. — This
piece of apparatus (Fig. 205) consists
of a strong glass tube, usually from 2
to 4 feet long, and 1£ to 3 inches in
diameter, closed at the upper end, and
having a brass cap and stop-cock at
the lower end, with a screw plug, of
sufficient size for the introduction of a
guinea and feather. To use, turn the
tube up, and it will be observed that
the feather is several seconds longer
in falling than the guinea ; connect
the stop-cock with the air pump, and exhaust the
tube, and it will now be found that the guinea
and feather fall at the same instant. Air may
also be condensed within the tube by a con-
densing pump, and a greater difference shown
than in the first experiment.

The apparatus described as the aurora tube is often used
for showing these experiments, though the ball and the
point, at times, interfere with the descent of the feather, and
piece of metal, which is not the case in the proper tube.

Price, $4 and $6.

208

BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 203. Bladder and Weights. — A pneumatic in-

strument (Fig. 206) to show the elasticity of
atmospheric air. It is formed of a circular
base, hollowed out in the middle into a cup
shape, having three stout brass wires connect-
ing with the top, and between these wires, a
movable box, the bottom of which is hol-
lowed out as the base. A small bladder, with
a small quantity of air in it, is placed in the
cavity below the box, and the box filled with
shot, or any heavy weight. The weights and
cup slide easily up and down between the wires. When
this instrument is put under the receiver of an air-pump,
and the air exhausted from around it, the elasticity of the
air within the bladder will expand it so much as to raise up
the heavy weights above it, and thus show its rarefaction.

Price, $1.75 and $2.

Fig. 207.

Weight Lifter by the Expansion of
Air. — Fig. 207 consists of a cylin-
der of brass, having a closed bottom,
attached to a small frame by a flange
at the top of the cylinder, within
which a solid piston moves freely, to
the rod of which there is a small
stage, on which weights may be
placed. When the piston rod is
down, there is a space in the lower
part of the barrel containing air, the
expansion- of which, when placed
under a receiver and exhausted, will
raise a heavy weight.

Price, $5.00.

The Improved Weight Lifter, or Upward Pressure Appa-
ratus.— (Fig. 208, page 210.) — This apparatus consists of a
very stout brass cylinder, having a stout flange at the top,
set in a stand supported on three iron legs about thirty
inches in height. The piston is accurately fitted to the
bore of the tube, and a ring attached to the under side of
the piston, from which weights are attached by a stout leather
strap. The stop of the glass cylinder is ground perfectly

AIR PUMPS AND APPARATUS. 209

flat, and has a brass plate also truly ground to cover it,
having a hole in the centre with screw, to which one end of
an elastic tube or hose is fixed ; the other end of the tube
being connected with the hole in the centre of the pump
plate. The air being then exhausted from the tube, the
piston with the weights will be raised the whole length of
the cylinder. The number of pounds that can be raised,
may be ascertained by multiplying the number of square
inches contained in the area of the cylinder by fifteen. The
iron legs unscrew for convenient transportation.

Price, with 3 inch cylinder, $6.00.

" 31 " " $8.00.

" best flexible tube with

screw connectors, $2.50 to $3.50.

Large Weight Lifter. — (Fig. 209, page 210.)— The con-
struction of this instrument is nearly the same as the preced-
ing, but of a larger make ; the cylinder is twelve inches
long and four inches wide, mounted on a strong mahogany
frame over five feet high. To the piston is attached by a
leather strap, a large platform, on which any convenient
weight may be placed. The instrument being capable of
raising over one hundred pounds.

Price, complete, with best English flexible

tube, 3 feet long, $15.00.

Brass Barrel Weight Lifter.— (Fig. 210, page 210.)— This
consists of a brass cylinder, or barrel, about two and a half
inches in diameter, and eight inches long, open at the bottom,
and screwed to a mahogany frame by a flange around the
lower end of the cylinder, within which there is a solid
piston, having a stout rod which is bent in the form of a
hook at the end, to which a heavy weight may be attached ;
the upper end of the cylinder has a brass cap and stop-cock,
to which a flexible tube, proceeding from the air pump, may
be attached ; on exhausting the air, it will be found, that
the atmosphere pressing on the under side of the piston will
raise it, and a weight of about fifty pounds.

Price, $7.50.
18*

210 BENJ. PIKE'S, j;i., DESCRIPTIVE CATALOGUE.

Fig. 28. Fig. 210.

Fig. 209.

AIR PUMPS AND APPARATUS.

211

The Air Shower.— (Fig. 211.)— This ap-
paratus consists of a block of wood, having
a long piece of wood, c, fixed lengthwise
through it, the under side of the block
being turned perfectly true, to fit the top
of a receiver, A. To use, place it in the re-
ceiver, A, which is also used as a hand glass,
place a tumbler of water, B, under, so that
the end of the wood is immersed in the
water ; place your thumb on the top of the
wood, and while the receiver is exhausting,
you will see the air pass out of the pores of the wood in*o
the water. Take off your thumb, and a vast stream of ait-
will flow through the wood. This experiment shows that
wood is pervious to air, and that the course of the air vessels
is lengthwise. Price, 75cts. ; receiver, 75cts.

Mercury Shower. — A pneumatic apparatus, Fij?- 2l '•
to show that, if the pressure of the atmo-
sphere be removed from an under surface, the
pressure still remaining on the surface above
has the effect of driving a fluid readily through
the pores of such substance as it would not
otherwise penetrate. A is a wooden cup.
B is a plug or nozzle of oak wood fastened
through the bottom of the cup and projecting
downwards two or three inches. C is a vessel
put beneath it when in use ; and D the open
topped receiver of an air pump. To use the
instrument, put a little mercury into A, and exhaust the ah
from D, when the mercury will soon filter through the oak
and fall into the cup C.

Fig. 212, as above, consists of a mahogany cup, through
the bottom of which a solid piece of oak wood, about two
inches long, is fixed ; the bottom of the cup is fitted
air tight on the top of the receiver. The receiver used
for the hand, called the hand glass, is used for this
experiment. When mercury is poured into the cup, and
the air exhausted out of the receiver, the pressure of the at-
mosphere on the surface of the mercury in the cup, will
force it through the pores of the solid piece of wood, and
it will fall like a silver shower to the bottom of the bottle,
and the mercury be collected in a glass vessel beneath. In

212

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

this experiment, and in all others where mercury is used,
great care must be taken to prevent the introduction of any
mercury into the air pump, as it would cause considerable
njury. Price, $1.00 ; receiver, Tocts.

Shower of Mercury Tube. — (Fig. 213.) — This
consists of a glass tube, about one and a half inch
in diameter, and from twelve to twenty-four inches
long, with a cap and screw at one end, fitting the
air pump on the inside, having a small glass tube
with a hole at the side, for preventing the mer-
cury being drawn into the pump, and at the top
of the tube a hard wood cap, within which a
piece of oak wood is supported, having a funnel
or cap of hard wood screwing over it, into which
the mercury is placed ; on exhausting the tube
by the air pump, the mercury will pass through
the pores of the wood, and descend into the tube
in a silver shower.

Price, $4.00 and $5.00.

Fig. 214. Flask for Weighing Air. —

Fig. 214 consists of a glass
flask or globe, having a cap
and stop-cock fitting the air
pump, supported by a hook to
a scale beam. To use, first
weigh the flask of air, as re-
presented in the cut, by plac-
ing the requisite weights in the
scale pan ; then exhaust the

flask of air by the air pump, and weigh it again in the same
manner ; the difference in the weights will give the weight
of air, or gas taken out.

Price, flask with stop-cock,

" mounted with steel beam and stand, $6.00.

AIR PUMPS AND APPARATUS.

213

Balance Beam and Cork Ball— F'^ 215-

(Fig. 215.) — This consists of a bal-
ance, to one end of which is sus-
pended a piece of lead, in equilibrio
with a piece of cork, or other light
material, at the other end of the
beam. Place the beam and stand
under a receiver, and having ex-
hausted the air, the cork will pre-
ponderate ; for, as its bulk is greater
than that of the piece of lead, it
must be more sustained by the air ;
re-admit the air, and the equilibrium
will be restored. Price, $3.50.

Sliding Rod Receiver— (Fig. 216.)— A
receiver for the air pump of any convenient
size or shape, having a brass cap cemented
to the neck, and a rod passing air tight
through a collar of leathers secured in a
cavity, and covered with a screw ; the rod
has a ring or handle at the top, and a hook
on the end within the receiver. One of the
many experiments for which this receiver is
used is the following : suspend a small re-
ceiver from the hook of this, and exhaust it
of air ; now let down the small receiver in
contact with the plate. While the outer one
is fixed, the inner one may be easily moved,
but on letting in the air, the inner is fixed
and the outer one loose ; observe in this ex-
periment the small receiver must not cover <
the hole in the centre of the receiver plate,
but be placed at the side.

Price, with plain receiver, $3.50 and $4.00.
" with swell " $4.00 and $4.50.

The Bell Glass Receiver with Sliding Rod. — This piece of
apparatus (Fig. 217, next page) consists of a swelled bell
glass receiver, usually about 10 inches in diameter, having
an opening in the top of 2i to 3 inches in diameter, accu-
rately ground to fit a brass plate of a little larger size, hav-
ing a screw in the centre, into which a packing-box, with

214 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 219.
Fig. 218.

rod movable, though perfectly air-tight, may be fixed ; on
the outer end of the rod there is a ring, serving as a handle
for depressing the rod, and within a hook for suspending
from. This, or a similar arrangement, is used with the
improved bell, flint and steel, &c., and parts of this may be
used for other experiments, the screws being made uniform
in their size. Price, complete,

" plate, with slide rod, $3.00.

Bell in Vacua.— (Fig. 218, as above.)— This is an appara-
tus to show that sound is not propagated in vacuo, and
thereby to prove that sound is but the air in vibration. It
consists of a small bell mounted within a glass receiver, and
supported from the top by a wire attached to a plug moving
air tight in a socket, and having a handle above the cap, by
which the bell may be rung ; when rung in a vacuum a
great diminution of the sound will take place, and were it
possible to produce a perfect vacuum, and insulate the bell
from all sonorous bodies, no sound would be heard. Three
sizes. Price $2.25, $2.50 and $3.00.

Improved Bell in Vacuo. — This form of the bell in vacuo
(Fig. 219, as above) has a spring-lever hammer, working
within the bell, and rung by depressing the rod having a

AIR PUMPS AND APPARATUS. 215

cap on the top, by means of a sliding rod attached to the
receiver. The bell is mounted on a neat metal foot, and
placed on a round piece of wood, or leather, when used ;
to prevent, as far as possible, the transmission of the sound.

Price, $3.00.

Float Wheel for showing the resistance Fig. 220.
of the air, — Fig. 220 consists of two light \
metal floats, or vanes, fixed to a centre and
turning freely on a pin fixed in a handle.
These vanes may be so placed on the pin
that their whole surface may strike the air ;
or, on the contrary way, that only the
edge of the vanes may strike the air. To
use, place the vanes on the pin so that the whole surface
strikes the air, and give it motion with the finger, and it will
soon stop, owing to the resistance of the air. Place it now
in the position in which the edge only strikes the air, and
give it motion, and it will be continued for several minutes.

Price, $0.75.

Torricellian Experiment. — (Fig. 221, next page.) — A stout
barometer tube of thirty-one inches in length, hermetically
sealed at the upper end ; the lower end immersed in a cup
of mercury ; the whole covered by a tall bell glass receiver.
On exhausting the air in the receiver, the air in the tube is
expanded, and escapes through the mercury ; on returning
the air to the receiver, the mercury is supported in the tube
to a height proportioned to the degree of exhaustion obtained
therein. Price, with receiver, $5.00.

Torricellian Experiment with Sliding Tube. — (Fig. 222,
next page.) — This drawing represents a more perfect arrange-
ment for the Torricellian experiment. The tube is supported
in the neck of a swelled bell glass receiver, having a brass
cap with packing-box and screw, containing collars of leather
through which the tube slides readily. To use, the tube is
exhausted with the end out of the mercury, and then im-
mersed by sliding down the tube through the collar of
leathers ; on returning the air to the receiver the mercury
rises in the tube, showing the exact degree of exhaustion
obtained. Price, $3.50 and $4.00.

216 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 222.

% Fig. -,23.

Fig. 221.

Fig. 221.

Torricellian Experiment with Flexible Tube. — (Fig. 223,
as above.) — This apparatus consists of a stout barometer
tube of forty inches in length, bent at one end as represent-
ed in the drawing, and having a stop-cock with flexible tube
for connecting with the air pump. The barometer tube is
graduated to thirty-one inches, marked on the glass. To
use, the lower end of the tube is immersed in a cup of mer-
cury, and the stop-cock connected with the air pump by a
flexible tube ; on exhausting the air the mercury will rise
in the tube in proportion to the degree of exhaustion.

Experiments in the condensation of air, may also be illus-
trated by this apparatus ; close the stop-cock, pour mercury
in the long end of the tube, to the height of thirty inches
above the surface of the mercury in the shorter leg. It
will be found that the air in the shorter leg has been com-

AIR PUMPS AND APPARATUS.

217

pressed into half its former bulk ; being pressed by one
additional atmosphere.

Price, of the tube, graduated, with cap

and stop-cock, - $5.00.

Water Pump in Vacuo. — (Fig. 224, opposite page.) — This
represents an open top receiver with the common water
pump placed on the top ; the tube of the pump being within
the receiver, and the end immersed in a vessel of water.
On working the piston the water will readily flow ; but ex-
haust the air from the receiver, and when a good vacuum is
obtained the water cannot be raised by working the pump.
This shows that all the phenomena of suction and pumps
are not owing to the abhorrence of a vacuum in nature, but
to the pressure of the air. Price, $8.00.

Fig. 223. Freezing Apparatus. — Prof. Leslie's

experiment of freezing water in vacuo,
by its own evaporation (Fig. 225) is
shown by a shallow glass vessel, as a
watch-glass, for containing the water
to be frozen, which is supported over
a wide glass basin, containing strong sulphuric acid, the
whole covered by a low receiver. When the air is exhaust-
ed from the receiver, the acid will absorb the vapor from
the water as rapidly as it is found, thereby abstracting the
sensible heat from the water, till congelation ensues.
Price, $1.50 and $2.00.

Fig. 226.

Freezing Apparatus with Thermo-
meter.— (Fig. 226.) — The same appa-
ratus as the last described, used un-
der the receiver with sliding rod, in
place of the low receiver, and having
a delicate thermometer with exposed
bulb dipping into the water, indicating
the gradual reduction of temperature
during the process.

Price, $3.00.

" with slide rod receiver,

$5.00 and $7.00.
" thermometer only, $1.00.
19

218 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 223.

Wollastons Chryophorus in Vacuo. — The cliryophorus
in this arrangement (Fig. 227, as above) has a circular piece
of brass, truly ground on the under side, and fitting the
open top receiver, and also having in the centre a block of
wood, well varnished, to render air-tight and surrounding
the tube of the chryophorous ; by this contrivance one of
the balls may be introduced within the receiver, and a va-
cuum obtained.

To use : cover the interior ball with a sponge, or cotton,
which may be tied on, and wet it well with ether ; turn all
the water in the upper ball. On exhausting the receiver, the
vapor in the interior ball of the chryophorus will be con-
densed by the evaporation of the ether, which will produce
evaporation from the surface of the water in the upper ball,
which vapor continues to condense, producing continual
evaporation from the surface of the water in the upper ball,
till the water therein is frozen. To prevent injury to the
pump from ether entering therein, a cup is placed on the
plate to receive any drops from the sponge.

Price, $5.00.

The Flint and Steel in Vacuo. — In the best construction
of this instrument (Fig. 228) a gun lock is supported in a
brass frame, and attached by a pillar to the centre of the
pump plate ; the lock has a brass arm terminated in a small
cup at one end, and at the other fixed to the lever of the

AIR, PUMPS AND APPARATUS.

219

cock ; the whole is covered with the receiver having a sliding
rod, and let off by depressing the rod on the cup. If the
receiver be exhausted, and the flint be made to strike the
steel, no sparks will appear ; and if there were powder in
the pan it would be burned. The sparks produced by the
flint and steel, are owing to small portions of steel struck
off by the percussion, and burning in the air ; without the
air the combustion of the steel cannot take place.

Price, with brass frame, $5.00.
" common construction, $3.00.

229- Apparatus to fire Gunpowder in

Vacuo. — (Fig. 229.) — This apparatus
consists of a bell glass, with brass
cap, having a large stop-cock and
funnel ; in the key of the stop-cock
there is a cavity, into which a small
quantity of powder falls ; on turning
the key a little, the aperture is en-
tirely closed, and when half round
the powder falls on a round piece of
iron, previously made red hot, and
supported on a stand within the bell
glass receiver. The powder will
burn, but no explosion takes place ;
the smoke remaining at the bottom.

Caution is required in performing the experiment, and the
bell glass should be exhausted after each charge is burnt.

Price, $4.50.

Apparatus for showing the effects
of burnt air. — (Fig. 230.)— This ap-
paratus consists of a glass receiver,
with aperture in the top about
three inches in diameter, truly
ground, covered by a brass plate
with stop-cock, to which a bent
metallic tube is screwed. To use,
place a pan of lighted charcoal so
that the end of the tube may be in
the flame ; first having exhausted the receiver, then open
the stop-cock, and the burnt air will pass through the tube
into the receiver, with which it may soon be filled. Take

220

BENJ. PIKE 8, JR., DESCRIPTIVE CATALOGUE.

off the plate and pipe, and if any animal be let down into
the receiver it will immediately "be killed. If a candle be
let down into the receiver when filled with the air, it will
go out, but will purify the air as far as it goes ; for you may
let it down the second time lower than the first, and so on
till the whole air is purified. The receiver and plate used
with the slide rod apparatus before described, answer for
this experiment by connecting the tube thereto.

Price of the whole apparatus, $6.00.
" bent tube only, - $1.50.

Fig. 231. Bursting Squares, or Crushed Bottle. —

— (Fig. 231.) — These are thin square glass
bottles, of about half a pint capacity. To
use, take one of the bottles and put in a
cork ; then seal it with wax so that no air
can escape ; then set it on the pump with
a receiver over it : and when you begin to
exhaust, the air within the bottle will ex-
pand itself so as to break it.

Or, cement on the neck of the bottle a
brass cap, with valve opening outwards ;
place under the receiver and exhaust the air, which will
escape from the bottle also ; return the air to the receiver,
and the valve closes and prevents the air from entering the
bottle, which is broken ; the square sides not being strong
enough to resist the pressure of the atmosphere. A wire
guard is sometimes used to cover the bottle, and prevent
the breaking of the receiver. When you have made this
experiment, wipe the pump plate so that none of the glass
remain, as it may spoil another experiment.

Price, glass squares, each, $0.16.
" cap with valve, each, $0.31.
F1«-232. « guard of wire gauze, $0.75.

Transferer.—(Yig. 232.)—
An instrument used with the
air pump, as a movable portion
or plate, for numerous purposes
of experiment. There are sin-
gle transferers and double trans-
ferers ; the latter of which is
shown annexed. It consists of

AIR PUMPS AND APPARATUS. 221

two plates, ground truly flat, and having pipes beneath,
communicating with each other by connecting tubes, and a
large pipe and cock below, which fits on to the table of the
air pump. If a glass receiver be placed over each trans-
ferer plate, they may be exhausted of air, and the lower
cock being turned, they may be removed from the air pump,
and set aside, that the continued result of the experiment,
whatever it may be, may be noted afterwards, and the air
pump in the interim used for other purposes.

Price, large size, with two gallon receivers, $15.00.

half " " $12.00.

quart " $10.00.

pint " $8.00.

" single transferer plate, with stop-cock

and stand, - $3.50 to $6.00

Fig. 233. Fountain by Elasticity of Air.—(Yig. 233.) —

A pneumatic apparatus, showing the elasticity
of the air. It is a glass vessel with a brass top,
and a tube within it, extending to near the
bottom of the glass. When this glass is partly
filled with water, and placed under a tall re-
ceiver of the air pump, the air being exhausted
by the action of the pump, the elasticity of that
air which remains within the vessel, drives the water through
the tube, and makes it play into the receiver like a fountain.
This action continues either until almost all the water is
driven out, or else until the air has become so rarefied that
it no longer has sufficient force to overcome the resistance.

This apparatus should only be used with a transferer, as
the water is liable to be drawn into the air pump, and the
pump injured thereby. Price, $2.00.

Water Hammer with Stop-cock. — This apparatus (Fig. 234,
next page) consists of a glass tube about 2 feet long, closed
at one end, and the other having a brass cap and stop-cock,
to which may be connected a hose or flexible tube, commu-
nicating with the air pump. To use, the tube is half filled
with water and exhausted, when bubbles of air will be seen
to rise with great rapidity ; when completely exhausted
turn the cock and unscrew the hose. Now turn up and
down the tube, and the water will be found to descend with
a force like the stroke of a hammer. Price, $2.50.

19*

222 BEXJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 236.

Fig. 233.

Fig. 231.

The Water Hammer. — (Fig. 235.) — This consists of a
glass tube usually about twelve inches long and one inch
in diameter, having three or four inches of water included
in it, above which a vacuum has. been formed, and then her-
metically sealed. On shaking such a tube vertically, the
water, rising a few inches and sinking suddenly to the bottom
of the tube, produces a sound like that arising from the
stroke of a small hammer on a hard body, whence the name
of this instrument, the action of which depends entirely on
the exclusion of the air, so that the water moves in a dense
mass. Price, 12 inch, $0.75 and $1.00.

24 " $1.50.

Pressure Gauge. — (Fig. 236.) — The pressure gauge is an
instrument to determine the pressure exerted in hydrostatic
or pneumatic machines, as the hydrostatic press, the air
pump, steam engine, etc. When the pressure is very great,

Alii PUMPS AND APPARATUS. 223

1 1, is usual to measure it by the compression of a certain
quantity of air contained in a tube of sufficient strength. It
consists of a stout glass tube, the bore about one tenth of
an inch in diameter, closed at one end, and bent up at the
other, having a ball about twice the capacity of the tube,
with a small hole on the side or top, and which is half filled
with mercury ; the tube is attached to a silvered plate,
graduated to the various pressures, which are represented
in pounds to the square inch ; the scale and tube are in-
closed in a stout glass shade, two inches in diameter, and
about ten inches long, cemented to a brass cap, and screw
ing on a large stop-cock, having a stout flange at its side,
with holes for screws for supporting the whole from the
wall, or posts, etc. ; at the lower end of the stop-cock is a
coupling box, for connecting a pipe communicating with the
apparatus or engine, the stop-cock closes the communication
when required ; under the ordinary pressure of the air the
mercury will stand at 0 on the scale, near the bottom of
the tube ; under a greater pressure the mercury will be
forced into the tube, and when occupying one half the
original space, will indicate the additional pressure of our
atmosphere, or fifteen pounds to the square inch ; when
occupying one third, a pressure of thirty pounds ; one fifth,
ninety pounds, etc. Price, $12.50.

Vacuum Gauge, or Indicator. — The arrangement of this y
instrument is the same as represented in Fig. 236, in regard
to the exterior mounting, but having the tube entirely filled
with mercury under the pressure of atmosphere, and on the
removal of the pressure the mercury falls, and the approach
to a vacuum is .indicated by the scale, which is graduated to
correspond to the common barometer ; thirty inches being
assumed as a vacuum. Price, $12.00.

HYDRAULICS AND HYDROSTATICS.

Fig. 327.

Scaled and Weights. — Small scales and weights (Fig. 23*7)
used for weighing in chemical experiments, packed in a
small case ; the weights ranging from half a grain to a quarter
of an ounce. Price, - $1.25 ; fine quality, $2.50.

" larger scales, with stand, on mahogany
box, with weights, &c. - $10.00

The Hydrometer. — (Fig. 238, next page.) — Hydrometers
are instruments used by dealers in wines, spirits, acids,
alkalies, syrups, and all commercial liquids, for ascertaining
their comparative strength.

This instrument, as represented in the figure, consists of a
hollow glass ball, B, with a smaller ball, C, appended to it,
and which, from its superior weight, serves to keep the in-
strument in a vertical position, to whatever depth it may be
immersed in a liquid. From the large ball rises a cylindrical
stem, a d, on which are marked divisions into equal parts ;
and the depth to which the stem will sink in water, or any
other liquid fixed on as the standard of specific gravity, being
known, the depth to which it sinks in a liquid whose specific
gravity is required, will indicate, by the scale, how much
greater or less it is than that of the standard liquid.

Those most celebrated, are the scales of Baume, Cartier,
Twaddell, and Guy Lussac. Most of these scales are arbi-
trary, and formed after the ideas of their projectors, but hav-
ing no particular reference by which they may be understood.

HYDRAULICS AND HYDROSTATICS.

The centesimal hydrometer, by
Guy Lussac, is an exception, the
extreme points being water and
absolute alcohol ; this space is
divided into one hundred parts,
thus showing in alcoholic mix-
tures the percentage of alcohol
in the liquid. They are made of
glass, brass, and silver, usually
from six to ten inches long, of
the form represented in the cut
(Fig. 239), the graduations being
marked on the stem.
Price, Baume's and Car-
tier's, for spirits,
in glass,
" " " " in brass,

Fig. 238.

$0.50.
$3.50.

in silver, $5.50.

"acids,

$6.00.

in brass, $4.00.
in glass, $0.75.

Twaddell's,
Guy Lussac,

$1.00.

in brass, $6.00.
in silver, $9.00.

Table showing the Comparative Scales of Guy Lussac and
Baume, with the Specific Gravities and Proof, at t/ie
Temperature of 60 Degrees.

GUY LUSSAC'S SCALE.

BAUME'S SCALE.

SPECIFIC GRAVITY.

PROOF.

101)

45

796

IdO

^ 95

40

815

92 «

90

36

833

62 ^

85

JTJ

848

7-2 -5 2

2 80

31

863

62 £ A

75

28

876

52 ^ £

5 70

26

889

42 £5

£ 65

24

911

32

o 60

23

912

2-2 4th proof.

8> 55

21

9-23

12

5 50

19

933

0 Proof.

45

18

9,2

8

W 40

17

951

18 l-s

S3 35

16

958

29 1|

^ 30

15

964

35 DP-

25

14

970

48

226

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

Explanation of Baume s Scale. — Manufacturers who em-
ploy Baume's hydrometer, or have occasion to know the
value of the degrees on his scale, may find the following
formula useful.

Let B = Baume's degree, and 100 = water. Then
Specific gravity = ~^—

r^ o */ j A\ D

That is to say, 144 divided by the difference between 144
and the given degree of Baume, is the specific gravity in
question, stated in reference to water assumed = 100.
Thus, suppose Baume = 66°. Then,
Specific gravity = j—^g or ~ = 1.846 = specific gravity.

Scale of Specific Gravities indicated by TwaddelVs Scale.

Twaddell. Sp. Gr.
0 lOUO
10 105 )
20 111)0
30 1150
40 1200

Twaddell. Sp. Gr.
50 1250
60 13 JO
70 1350
8,) 1400
9J 1450

Twaddell. Sp. Gr.
K'O 150 i)
1 10 1550
120 1600
130 1650
140 1700

Twaddell. Sp. Gr.
150 1750
160 1800
170 1850
18i) 1900
190 1950

Fig- 24a Hydrometer with Weights.

—(Fig. 240.) — There is
a variety of kinds of hy-
drometers, with weights ;
the principal ones are
Dica's and Sike's, they
are used for ascertaining
the strength of spirituous
.liquors. One packed in a
case is here represented,
and is formed wholly of brass, and may be described
as consisting of three parts ; the scale, the ball, and the
stem, which terminates in a small knob, intended to keep
the instrument upright when in use. Upon this being put
into a long glass, containing spirits of wine, etc., it will sink
to a certain depth. If the spirit be very weak, it may not
sink low enough to cover the ball, in which case one of the
weights is placed above the knob of the lower stem. Ac-
cording to the weight used, and the degree to which the
instrument sinks, reference being had also to the tempera-
ture of the fluid, the degree of strength is ascertained.

Price, $12 to $25.

HYDRAULICS AND HYDROSTATICS.

227

Nicholson's Portable Balance. — Fig. 241. Fig. 242.
(Fig. 241.) — This consists of a hollow
cylinder of metal terminated at each
end by a cone ; from the top of the
upper cone rises a small stem of brass,
terminated by a cnp, a, which may be
slipped off ; from the end of the lower
cone is suspended a cup, e, that is
loaded with a weight, sufficient to sink
the instrument in water nearly to the
base of the upper cone ; by placing
weights in the cup, a, at the top, it is
immersed to the mark on the stem ;
if the weights be removed and a solid
body, whose weight is less than theirs,
placed in the cup, it may be immersed
again to the same mark, by placing weights along
with the solid in the cup, and thus the weight of
the solid obtained ; now place the solid in the cup
attached to the weight and weigh it in water;
having now the weight of the body in air, and its
loss of weight in water, its specific gravity may be
ascertained by dividing the weight in air by the
loss of weight in water, the quotient is the specific
gravity. Price, $3.50.

Nicholson's Hydrostatic Balance. — (Fig. 242, as above.) —
This instrument is made of brass, highly finished, and having
a cage over the counterpoise for confining any solid body
that is lighter than water. Price, $6.00.

Frye's Lactometer. — (Fig. 243, next page.) — For testing
the quality of milk ; made under the direction of the Board
of Agriculture of the American Institute, in the city of
New York, who have strongly recommended it to the
public patronage.

This instrument was invented for the purpose of ascer-
taining the density, and fixing the standard weight, of pure
unadulterated milk, as it is produced in the best grazing
districts in the country, and with a view of detecting the
frauds practised by adulterating milk with water, so often
complained of by the consumer, in large towns and cities
throughout the Union.

228

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

Fig. 243.

Croton water,

i milk and f water,

i milk and ^ water,

milk and £ water,

Pure Orange Co. milk,

w

20

40

GO

80

100

Directions for using the In-
strument.— Fill the tin tube,
which accompanies the in-
strument, with the milk to
be tested at a temperature
of about 60 degrees, and sus-
pend the lactometer in the
milk, and it' the milk is
proof, the instrument will
sink to the degree marked
100 on the scale, or P, show-
ing that the milk is at par ;
but if the milk has been
adulterated with water, or
lias been taken from cows
that have been fed on slops
from breweries, and kept
confined in stables i;i warm
weather, the instrument
will, in all such cases, sink
below par, and show the
per centage of adulteration,
which, in some instances,
will be 25 per cent, below
par; but if the milk is supe-
rior, the instrument will
rise above P, and show the
per centage above par,
which, in some instances,
will be 10 per cent. Each
division 011 the scale is 5 per
cent.

Any person can test the
correctness of the lactometer
by mixing water with pure
milk, and note the per cent-
age of water which they
use, and suspend the instru-
ment in the mixture, and it
will give the proportion of
water added.

To farmers the instrument
has proved to be very valu-
able, as a ready means of
testing the relative quality
of their cows, by inspecting
their milk, and also showing
the effects produced by a
change of the animals' food,
as its quality will change
the density of the milk.

Price, $1.00.

HYDRAULICS AND HYDROSTATICS. 229

Fig. 244. The Oleometer. — (Fig. 244.) — The point indicating
pure sperm oil, is 0 and S on the top of the stem ;
that of whale oil, 100 and W. The temperature is
graduated at 60 degrees, and for every five degrees
colder you will deduct two marks ; and for every five
degrees warmer, add two marks. After you get the
correct graduation, then all variations will show you
the per centage of whale oil. Each mark on the
stem is two per cent. Price, $2.00.

The Urinometer. — (Fig. 244.) — This small instru-
ment is intended to ascertain the strength or acidity
of the urine, and thereby determine the comparative health
of the body, particularly with reference to the disorder called
diabetes, or the involuntary discharge of urine.

The graduated side of the scale is marked with degrees,
by which the comparison may be made on the reverse side ;
at the upper part is marked the letter W, being the point at
which the instrument rests when immersed in pure water.
The next division, marked by the letter H, is the point at
which it rests when immersed in urine when the body is in
good health ; the letter S is marked to signify strong, but a
less degree of health ; and the last division, the point at
which the instrument rests when the disorder of diabetes
has taken place, and its progress, may be ascertained by the
surface of the fluid marking an increased degree on the
scale.

This instrument is accompanied with a small glass vessel
for containing the urine, one half ounce of which is sufficient
to float the instrument therein ; the whole is packed in a
small round case about four inches long. Price, $2.00.

Urinary Cabinet. — (Fig. 245, next page.) — The cabinet
consists of urinometer in case, graduated glass for containing
the urine, bottles for acids, spirit lamp, test tubes, watch
glasses, dropping tube, thermometer, test papers, &c., com-
plete, as represented in the cut ; forming a useful and im-
portant apparatus for the medical practitioner, and the
whole of a size that may be conveniently carried in the
pocket. Price, $8.00.

20

230 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 215.

Fig. 246. Tube to shoiv the Relative Weight of Fluids.—
YJFig. 246 consists of a glass tube, bent and graduated
as represented in the margin; on pouring into the
upright branches, equal quantities by weight of the
respective liquids, their relative weights would ap-
pear on inspection ; being inversely as the heights to
which they would rise in the branches of the tube.
The accuracy and utility of such an instrument are
augmented by filling the lower portion of the tube
\-/ with mercury, and the graduated branches being of
equal diameter, given weights of any liquids, which
would not act chemically on the mercury, will show, by
their respective heights on either side, how much greater
space an ounce, a dram, or any other quantity of one liquid
would take up than an equal quantity of the other ; and
hence it would appear how far the specific gravity of the
latter exceeded that of the former.

Price, $0.75 and $1.50.

Hydrostatic figures. — (Fig. 247, opposite page.) — This
consists of a tall glass jar, supported on a foot, and nearly
filled with water, or alcohol and water, to prevent its freez-
ing in cold weather, into which small hollow glass figures,
as men, a balloon and car, etc., are floated ; they are made
of variously colored glass and curiously ornamented ; they
have a small hole in the lower part, through which they are
partly filled with water, till they will just float in the liquid,
and the addition of a little more weight would cause them

HYDRAULICS AND HYDROSTATICS.

'231

to sink. The jar is covered at its mouth air-tight
with a piece of gum elastic, over which is tied a
piece of fancy leather. If the leather be now
pressed inwards with the finger, the water being
almost incompressible, and the air highly so, that
contained in the little images will yield to the com-
pressing force, and becoming contracted water, will
enter, and the images thus becoming specifically
heavier than they were at first, will descend to-
wards the bottom of the jar ; on the pressure above
being removed, the air in each image recovering
its elastic force, will expel the water, and the
images will rise as before.

Price, - $2.50 and $4.00.

Figures, only, $1.00 and $2.00.

The Siphon (Fig. 248) is an instrument used
to decant fluids, or convey them from one place,
over an obstacle that is higher than their surface,
to another that is lower ; its form is exceedingly simple, be-
ing nothing more than a crooked tube.

If a common siphon, with one side longer than the other,
be filled with water, and inverted or held with the open
ends downward, the atmospheric pressure acting equally on
both sides, and the liquid columns being unequal, the water
will escape through the longest leg, falling in virtue of its
specific gravity ; but if, when such a siphon is filled, its
shortest leg be plunged beneath the surface of the water,
not only will the liquid all run out of the longer
leg, but it will also rise in the shorter and be dis-
charged from the other in a continued stream, till
it sinks below the open end of the shorter leg ;
if the siphon be used without previously filling it
with the liquid about to be decanted, though
the liquid will rise in the shorter leg, it will not
ascend beyond its own level so as to pass over
the bend in the tube and escape, unless it be
drawn out of the longer leg.

The siphon represented here has an additional
tube, open at the upper end, and communicating
below with the longer leg of the siphon; the
shorter leg then being plunged in any vessel of
liquor, the opening in the longer leg is to be

Fig. 248.

232

BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

stopped with the hand or otherwise, and by suction at the
end of the additional tube, the liquor may be made to pass
over the bend, and fill the longer leg, when, being suffered
to escape, it continues to flow as long as the extremity is
immersed in it. Price, in glass, $0.75 and $1.00.

" in metal, $0.75 and $1.25.

" without suction tube, $0.37.

Fig. 249.

B

The Wirtemberg Siphon. — This in-
strument (Fig. 249), when once filled
with liquid, will remain so, and hence
may be hung up in that state ready
for use. One leg being plunged into
a vessel of the liquid to be drawn off,
it will escape through the open extre-
mity of the other leg, in consequence
of the additional pressure of the liquid
in the vessel. Siphons can only be
used for transferring liquids from
higher to lower levels.

Price, 38 cts. and 75 cts.

Fig. 250.

Tantalus Cup. — Fig. 250 consists of a cup
with a siphon so adapted to the cup, that the
short leg being in the cup, the long leg may
go down through the bottom of it. When a
liquid is poured into the cup, it will rise in
the cup until the height of it is above that
of the bend of the siphon, when the siphon
will begin to act, and the whole of the water
run out. It is called Tantalus Cup, because
the siphon is usually concealed by a small
figure endeavoring to drink, but who is foiled,
for immediately the water reaches his mouth it flows away.

Price, $2.50.

Fig. 251.

Double-bodied Vessel— (Fig. 251.)— This
cut represents a piece of apparatus called a
double-bodied vessel, the only communica-
tion between the upper and lower portions
of which is through the tubes C and D ; if
the part B be filled with water to the neck,
and A with port wine, so as to rise above

HYDRAULICS AND HYDROSTATICS. 233

the tube, D, still no mixture or alteration in the state of the
liquids will take place, for the lightest occupying the
highest situation will retain it undisturbed. But if the
lower part be filled with port wine, and the upper with
water, the former fluid will ascend through the tube, D,
;uul the latter descend through the tube, C, till they have
entirely changed places. Price, $1.50.

Lifting Pump. — (Fig. 252, next page.) — Represents a
model of the common or lifting pump ; it consists of a glass
cylinder or chamber, u c, having a piston or box, c, with a
valve opening upwards, the piston being raised or depressed
by the rod D and handle E ; also, having a valve, H, opening
upwards, at the bottom of the chamber, to which is attached
a pipe, A, of sufficient length to reach the water. At the
top of the chamber is a reservoir, having a pipe as an outlet
for the water. To use, take hold of the handle, E, and
thereby draw up the bucket from B to c, which will make
room for the air in the pump, all the way below the bucket,
to dilate itself, by which its spring is weakened, and then its
force is not equivalent to the weight or pressure of the out-
ward air upon the water in the vessel below ; and, therefore,
at the first stroke the outward air will press up the water
into the lower pipe, and after a stroke or two, will penetrate
through the valve, H, and occupy the cylinder or barrel, B c.
Upon depressing the bucket again, the water cannot return,
because any force applied above will necessarily close the
valve, H, and the bucket in returning will press upon the
water, until the pressure of the water upon the under surface
of the valve in G, will open the valve at that part, and
escaping through the hole, will occupy a space above the
bucket G. The next stroke of the handle will have a double
effect, it will draw up the water from the well, as in the
former instance, so that it shall again fill the cylinder, but
with fresh water ; for it will be readily seen, that the lifting
of the bucket after the water has obtained access above it,
does not replace that water as before, but the very circum-
stance of lifting the handle will close the valve above, and
the water will be lifted up at the same time, filling the
reservoir, D, which will discharge by the pipe, F.

Price, $3.00 and $4.50.

20*

234 BEXJ. PIKE'S, JTI., DESCRIPTIVE CATALOGUE.

Fig. 253.

Forcing Pump. — (Fig. 253, as above.) — A pump which
is capable of driving a stream of water above the pump
barrel by means of compressed air, and illustrates the action
of the fire engine. It consists of a glass cylinder, D, with
solid piston, G, connected by a rod to a handle, E ; at the
bottom of the cylinder there is a valve, H, opening upwards,
having a pipe for communicating with the water, a strong
glass air vessel, K, at the top of which is a cap and jet, the
lower part, i, extending nearly to the bottom of the air
vessel, where there is a valve, P, opening upwards, and a
bent tube, M, connecting the air vessel with the cylinder of
the pump ; the jet is sometimes made so that it may be
turned in any direction. To use, the pump-handle and piston
are drawn up ; a vacuum being produced below the piston,
the pressure of the atmosphere on the water of the well

HYDRAULICS AND HYDROSTATICS.

235

drives the water through the valve at the bottom of the
pump cylinder, and thus the cylinder is filled with water;
when the piston is forced down again, the water cannot pass
through it, nor back again into the lower part of the pump,
and it is forced through the bent pipe into the air vessel, K,
or condenser ; and when the piston is raised again the valve
shuts, and prevents the water in the air vessel from returning.
Thus, by repeated strokes, the water is forced into the air
vessel till it rises above the end of the jet pipe, i, and then
begins to compress the air, which is more and more com-
pressed, as the water rises up the pipe, and the air begins
to act forcibly by its spring against the surface of the water,
and this action drives the water up through the pipe, i, from
which it spouts to a great height, and is supplied by alter-
rately raising and depressing the handle, E ; and as the spring
cf the air continues while the piston is being raised, the
stream, or jet, will be uniform as long as the pump is
worked. Price, $5.00 and $6.00.

Fig. 254.

Forcing and Lifting
Pump in Frame. — These
models (Fig. 254) consist
of a forcing and lifting
pump, mounted in a ma-
hogany framed stand,
having a reservoir to hold
water. In the forcing
pump there is a variation
from the former descrip-
tion, the jet pipe being
connected near the neck
of the air vessel, and not
on the top, as before de-
scribed. .

Price, $10.00 and
112.00.

Hydrostatic Instrument for showing the Rise of Water to
its Level, and other Experiments. — This instrument (Fig.
255, next page) consists of a large glass vessel, with a neck
on the lower part cemented into a brass cup, and supported

236 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 255.

long-
tube

on a brass base ; to the sides of the brass cup are soldered
brass tubes, about one inch in diameter, and five inches
; at the end of one there is a joint having a long glass
, which may be inclined to any angle ; the other tube is
terminated in a socket, into which tubes of various shapes
may be inserted, a variety of which, each attached to a cork
fitting the socket, accompany the instrument ; also a siphon
tube to illustrate intermitting springs, etc. This instrument
is designed to show that in tubes that have a communication,
whether they be equal or unequal, short or oblique, the
fluid always rises to the same height. Price, $7.50.

Fig. 256.

Hydrostatic Equilibrium. — (Fig. 256, as above.) — This
arrangement consists of a tjn box, A B, formed as repre-
sented in the cut, with the two raised extremities open at
top ; the sides are made of glass, water tight, having four
differently shaped tubes, cemented into caps, on the surface
of the oblong part. To use, fill the vessel with water to

HYDRAULICS AND HYDROSTATICS. 237

the height marked by the horizontal line marked in the cut,
which is a little above the upper ends of the four tubes ; it
will be found that the liquid will pass laterally into the
tube, C, ascend directly in D, and circuituously in E, while it
first descends and then ascends in F, rising equally in all the
tubes, and spouting out till the water is reduced in the side
tubes to the level of the summits of the internal ones, when,
the equilibrium being established, the liquid will remain at
rest. Thus, it follows, that any number of columns of a
liquid, freely communicating, whatever may be their re-
spective diameters and figures, will always have the same
vertical height. Price, $2.50 and $4.00.

Hydrostatic Equilibrium. — (Fig. 257.) — Another appa-
ratus to exhibit the same effect as the last, in which a small
column of water supports a much larger quantity.

Price, $3.00

Fig. 257. Fig. 258.

Hydrostatic Paradox. — Fig. 258 consists of a pair of scales
mounted on a brass stand, having a wide mouthed glass jar,
or cup. suspended from one end, and the other end having
the usual scale pan. On the pillar supporting the scales,
there is a brass slide with a milled-head screw for fastening
it at any height required, to which there is an arm bearing
a round block of wood loosely fitting the glass vessel. To
use, let the jar, nearly filled with water, be poised by loading
the opposite pan with the requisite weights ; then after
marking exactly the height the liquid stands, pour out a
part of it and immerse the block of wood, supported by the
arm free from the sides and bottom, just deep enough to
raise the remaining liquid to the same height as at first, at
which it is screwed fast, when the balance will be again

238

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

exactly equipoised. This effect of the vertical pressure of
liquids may be variously exhibited, and the results are curi-
ous and important. Piice, $5.00.

Fig. 239.

The Hydrostatic Bellows.
—(Fig. 259.) — This instru-
ment is sometimes called
the hydrostatic paradox,
from the fact, that a very
great weight may be bal-
anced by a small weight of
water. It consists of two
round boards, from one
foot to one and a half in
diameter, attached to one
another by leather going
all round them, and making
the space within them
water tight ; there is a hole
in the upper board over
which is screwed a metal
pipe, about four feet long,
with a funnel at the top,
for conveniently introduc-
ing water, and filling the
space between the boards
till the water stands to a
height of three or four feet
in the tube, when it will
sustain the weight of one
or two men without forcing
the water out. The leather
is stout, and prepared so
as to be water tight under
a great presure ; the tube
jointed that it may be more
portable, and also showing
the effect of a column of
water of a less height.
Price, $5.00.

" extra large, $7.00.

HYDRAULICS AND HYDROSTATICS. 230

Vessel for Spoutitiy Fluids. — (Fig.
260.) — This instrument consists of a
japanned tin vessel as represented in
the cut, usually from twenty-four to
thirty inches high, having five pipes or
jets, with exactly the same sized aper-
tures fixed on the side of the vessel at
equal distances apart ; the top of the
vessel is enlarged for a reservoir, and
the whole is mounted on a circular
base.

In estimating the lateral pressure of
liquids, the vertical height must be
taken into the account ; since the ef-
fective force with which a liquid acts
against any given point in the side of
the containing vessel will depend on
the depth of that point beneath the
surface of the liquid.

This will appear from the manner
in which water flows from apertures in the side of a cistern,
as the velocity of the stream will always be exactly pro-
portioned to the distance of the point of discharge from the
superior surface, and the consequent degree of pressure
which takes place. Suppose a vessel, A, to be filled with
water, and to have three or more tubes or pipes, B, c, D, of
equal lengths and diameter, fitted into lateral apertures at
different heights ; then if the liquid were suffered to flow
from the pipe D alone, the others being stopped, a greater
quantity of water would be discharged in a given time than
by the pipe c alone, and a greater quantity would issue
from the latter in the same time than by the pipe B only ;
the water being kept at the same level, so as to maintain an
equality of pressure during the whole time it was flowing.
And if all the pipes were opened together, the water would
spout to a greater distance from the pipe D than from either
of the others.

The quantity of water spouting from any hole in a given
time, must necessarily be as the velocity with which it flows ;
and if, therefore, the hole D is supposed to be four times as
deep below the surface A, as the hole B is, it follows that D
will discharge twice the quantity of water, that can flow
from B in the same time, because 2 is the square root of 4.

240

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

So in like manner, if D had been nine times the depth of B,
three times the quantity of water would issue from it, 3
being the square root of 9. Price, $5.00.

Fig. 261.

. Archimedes' Screw (Fig. 261, as above) is a machine for
raising water ; it is represented and described as follows :

A is a hollow pipe, coiled around a cylindrical axis ;
which axis is inclined at an angle with the ground, and sup-
ported at each end upon pivots, the upper pivot being fur-
nished with a handle. When this is turned round, the lower
end of the pipe dips into the water in the well below, and
turning upwards directly scoops up some of the water.
When the end points up, the part B will become lower than
it ; therefore the water will fall to B. Another half turn of
the handle brings C to the lowest point, and the first water
will occupy that part of the tube ; at the same time more
water will be scooped up at the end. In a number of turns
of the handle, equal to that of the coils of the tube, the first
water will reach, and flow out at the top ; and from that
time a flow will take place at every revolution of the
machine. Price, $9.00.

Barker's Mill, — (Fig. 262, next page.) — This engine, as
represented in the annexed figure, consists of a hollow cy-
lindrical metal pipe, A B, of considerable height, and ter-
minating above in a funnel-shaped cavity. The pipe is
supported in a vertical position, by resting below on a
pointed steel pivot, turning freely in a brass box, adapted
to receive it ; and the upper part has a cylindrical steel
axis, C D, passing through a board, supported by uprights
at the sides. The hollow tube, A B, communicates with a

HYDRAULICS AND HYDROSTATICS.

211

cross tube, E F, closed at the extremities,
but having adjustable orifices at the opposite
sides, near each end of the cross tube. A
pipe, G, above, communicates with a supply
of water, which it discharges into the funnel
at the top of the vertical pipe, B ; and the
supply must be so regulated that the pipe
may be kept constantly filled with water
without running over; while the orifices in
the cross-pipe at E and F will deliver the
water with a force proportioned to the height
of the column in the tube, A R, and the aper-
tures being in opposite directions, the spout-
ing currents will communicate a centrifugal
motion to the vertical tube and its axis, C D, to which may be
attached a toothed wheel connected with any other machi-
nery. The action of this machine does not, as sometimes stat-
ed, depend on the resistance of the atmosphere to the jets
from the cross-pipe ; but is wholly owing to the hydrostatic
pressure of the column of water in the vertical tube, which,
exerting great force on the interior of the horizontal tube, and
that force being removed from the points whence the water
issues, the pressure on the corresponding points, on the
opposite parts of the interior of the tube, tends to make it
revolve, the action of both jets producing motion in the
same direction. Price, $5.00.

Centrifugal Pump. — (Fig.
263.) — A machine for raising
water, dependent upon centri-
fugal force, combined with the
pressure of the atmosphere.
It consists of one, two, or more
arms, erect below, and branch-
ing out above, joined to a ver-
tical axle. Near the upper
extremity of each arm is a
clack valve opening upwards ;
while near the bottom of the
vertical tube, or the bottom
of each (if there are more than
one), is a similar valve, also
opening upwards. Water be-
21

242

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

ing poured into the machine before using, and a rapid mo-
tion being given to it by a handle at top, the water in the
arms acquires a centrifugal force, opens the valves at the
end, and flies out into a circular trough prepared for it.
This machine is simple, but not so effective, as a well-made
pump. Price, $10.00.

Brahma's Hydraulic
Press.— (Fig. 264.)— This
is a valuable instrument,
and one by which a pro-
digious power is obtained
with the greatest ease,
and in a very small com-
pass. The size of the
model represented is usu-
ally about twelve to four-
teen inches square, with a
cylinder about four inches
diameter.

Its action depends upon
the principle that fluids
transmit pressure equally
in all directions. A solid
piston, E, is constructed
so as to move water-tight
in a cylinder. The space
beneath the piston is filled
with water, and communi-
cates by a small pipe with a forcing pump, worked by the
piston, B, by means of the lever, A, and by which the water,
which is contained in the cistern, G, is forced through the
valve, D, into the large cylinder. The large piston being
thereby driven up, carries with it the bed, H, and presses
closely together whatever may be above it. Whatever pres-
sure is exerted upon B, is transferred to E, and is increased
according to the relative size of the two pistons. Suppose,
for example, the piston at B to have a superficial area of one
inch, and the large cylinder of ten inches, then every ten
pounds pressure put upon B, will be increased by E ten-fold,
and become one hundred pounds; and as a person may
exert a force of fifty pounds on the lever, this weight alone
will give a pressure of 100X50 pounds, or more than 2 tons,

HYDRAULICS AND HYDROSTATICS.

243

and that with a pump, the large cylinder of which is not
more than 4 inches diameter ; and by decreasing the smaller
tube from one inch diameter to half an inch the power will
be increased four-fold, or to nearly 9 tons.

Price, $40.00.

Fig. 265.

Hydrostatic Paradox with Movable Piston. — The displac-
ing of any portion of fluid by a fixed solid, whatever be the
weight of the solid, produces no difference in the weight of
the fluid, provided it stands at the same height as before,
and raising the height of the fluid by plunging a solid into
it, increases its pressure, or apparent weight. If the fluid
is raised by pressing or forcing it upwards, in however thin
a column, provided the vessel be kept full, and closed in all
directions, the pressure of the fluid and the apparent weight,
of the vessel will be increased, although nothing whatever,
either solid or fluid, is added to it. To illustrate this prin-
ciple, the instrument represented in the above cut (Fig.
265), is used. The cylindrical vessel, A B c D, has a glass
tube closely fitted into its top, and a rod, E c, fixed to a
plate, F G, moving up and down, water-tight, in the cylinder

244 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

which is represented fitted to a frame with the end of the
rod, E, attached to one end of a balance.

The plate being at the bottom, c D, water is poured into
the vessel, so that it rises nearly to A B, but does not rise in
the tube. It is then balanced by a weight in the scale, L.
If the rod E K is drawn up so as to raise the plate and
force some of the water into the tube, the water will seem
to weigh more than it did ; and to restore the balance, more
weight must actually be put into the scale L. If the vessel
is three inches diameter, every inch that the water rises
in the tube will require more than four ounces to be added
to the weight, whatever be the bore of the tube ; for the
pressure of the water in all directions will be increased by
the weight of a body of water, whose height is the height
of the water in the tube, and whose base is the extent of
the surface of the water pressing on the top, A B, of the
vessel. Now the top being three inches diameter, its surface
is about 7Tj square inches ; and a portion of water one
inch high, and 7T'j square inches broad, is Yy'j cubic inches
of water, which weigh about four ounces. Thus, raising the
rod a foot will add three pounds to the apparent weight of
the water.

This principle, from its extraordinary illustrations, is call-
ed the hydrostatical paradox ; paradox being a word from
the Greek, and signifying something, which, though true,
appears when first considered to be untrue. When we are
told that any quantity of water, however small, may be so
employed as to balance any quantity of water, however
great, we are at first startled by the apparent impossibility
of the statement. But when -we come to examine it more
closely, we find it to be accurately true ; for the small tube
in the foregoing figures may be made ever so narrow, and
to hold ever so little water, while the wide tube communi-
cating with it may be made ever so large, and holding ever
so much water ; and the level at which the water stands in
both tubes will be the same. So in the scales you may
plunge as large a body as you please into the vessel of
water, and leave as little water in the vessel as possible ;
still, if what you leave stands as high as the whole quantity
stood, it will, by weight and pressure together, produce as
much effect as the whole quantity of fluid.

Everything, under these circumstances, depending upon

HYDRAULICS AND HYDROSTATICS. 245

the height and the surface, and very little upon the bulk of
the fluid, we may easily perceive what mischief may be done
by a very small quantity of water, if it happens to be ap-
plied or distributed, so as to stand high, in however thin a
body or column, and to spread over a wide but, confined and
shallow &>-*•,

Pnce, Tfitn t»ajance and irame, complete, #25.00.

ELECTRICAL APP1MTCT

PIKE'S IMPROVED PLATE ELECTRICAL MACHINE.

THIS elegant electrical machine (Fig. 266, opposite page)
is mounted on a large base, supported from the floor by four
stump feet, and on the top there are fastened by screw bolts
two turned columns, with a cap also fastened by screw
bolts ; near the centre of the columns, the axle, made of
polished steel, is supported, bearing the plate, which is
pressed at opposite sides of its circumference, by two pairs
of elastic rubbers, secured between the columns ; the press-
ure of the rubbers may be regulated at pleasure ; to one
end of the axle the winch and handle is fixed, by which the
plate is easily turned. The conductor consists of two up-
right brass tubes, two and a half to three inches in diameter,
having large brass balls at each end and in the middle,
also a cross tube connecting the two together at the top,
and having a ball in the centre. From the lower balls and
opposite the centre of the plate; there are brass arms extend-
ing half across the plate, with rows of teeth for collecting
the fluid from both sides of the plate. The conductor is
supported on bases, by four strong glass pillars, set at each
end in brass sockets, and secured to the base by screw bolts,
all of which may be taken apart for convenient transporta-
tion. These machines are made with plates of 24, 27, 30, 36,
and 44 inches in diameter, with framework in proportion
made of mahogany or rosewood, handsomely polished, and
with conductors of brass, highly finished, from four to seven
feet high, having balls, wires, and suitable holes for connect-
ing other apparatus. These machines are by far the most
durable and elegant in their construction of any in use ;

ELECTRICAL APPARATUS.
Fig. 266.

248 BEXJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

many of our first institutions are using them with the
highest satisfaction.

Price, with mahogany frame,

24 inch plate, $75 ; in rosewood, $85.

27 " " $85; " $95.

30 " " $110; " $120.

36 " " $130; " $140.

40 " " $165; " $180.

44 " " $200; " $220.

Plate Electrical Machine, with upright Conductor. — This
plate (Fig. 267) represents a convenient and substantial

Fig. 267.

ELECTRICAL APPARATUS.

249

mode of constructing the conductor of a plate machine, occu-
pying but little room on the lecture table. The machine,
as regards the mounting of the plate, is arranged as Cuth-
bertson's, having a longer base and stout glass supports at
each end ; beyond the edge of the plate and opposite thereto,
on which are placed the conductor, which is formed of long
brass tubes about 2 inches in diameter, having large balls at
each end, and connected together at the top by a tube of the
same size. To the lower balls are arms, having rows of
points, and collecting the fluid from both sides of the plate.
There are suitable holes in different parts of the conductor
for inserting electrometers, wires, &c.

This construction of the electrical machine has given the
highest satisfaction to those who have used them.

Price, 13-inch, $25.00.

" 16-inch, $30.00.

20-inch, $38.00.

Fig 268.

CutJibertsori's Plate Electrical Machine. — This machine
(Fig. 268, as above) consists of a plate of glass, of not less
than 12 inches diameter, turning on an axis that passes at

250

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

right angles through its centre. It is rubbed by two pair
of cushions, fixed at opposite parts of the circumference by
elastic frames of thin mahogany, which are constructed so
as to press the glass plate between them with the requisite
force, by means of regulating screws. A brass prime con-
ductor, supported by a stout glass rod, is fixed to the frame
of the machine, terminated at one end by a wire, with a
brass ball, and having branched extremities opposite each
other, and near the extreme diameter of the plate, in a
direction at right angles to the vertical line of the opposite
cushions. The branched extremities of the conductor are
furnished with pointed wires, that serve to collect the elec-
tricity from the surface of the excited plate. This form of
ihe* plate electrical machine is now little used, the more
modern style being preferable. Price, 12 inch, $25.00.

15 " $30.00.

18 " $38.00.

F^269- Plate Glass Electrical

Machine (French Plan). —
This arrangement (Fig. 269)
represents one of the French
forms of mounting the plate
glass electrical machine,
having but one pillar sup-
port, made very stout, to
the axis of the machine.
Two pairs of rubbers at-
tached to large brass balls,
are supported by insulated

£lass Pillars> the balls be-
m& connected together by a
brass tube, in the form of
an arch, extending over the
plate, forming the negative conductor to which the rubbers
are attached. The positive conductor with circular arms,
having rows of brass teeth at the ends, is mounted on a sepa-
rate movable insulated stand.

Price, with 20-inch plate, $50.00.

Plate Electrical Machine, for positive and negative Elec-
tricity.— This electrical machine, having a frame of maho-
gany or rosewood, in the form of a cross, is represented in

ELECTRICAL APPARATUS.

Fig. 270.

251

Fig. 270, and is mounted on four stump feet, about 6 or 8
inches from the floor, or table, on which it is used. On the
shorter arms of the frame, two pillars are attached by screw
nuts for receiving the axle of the plate, which axle is made
of polished steel, with a brass crank and rosewood handle.
The rubbers consist of two cushions of leather, connected

252 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

together by a stout brass spring, having a screw to give
them the required pressure ; supported on a stout swelled
glass pillar, cemented into a polished brass base, and being
tirmly held by a screw and nut beneath the frame. Over
the rubber is mounted a large and well-polished brass ball,
which is the negative conductor. The positive conductor is
a well polished brass cylinder, having swelled ends ; the one
having arms embracing the plate with rows of points for col-
lecting the fluid ; the other having a wire with a ball. The
conductor is supported on a stout swelled glass pillar,
mounted in a socket, by which the pillar can be separated
from the conductor, and at the frame cemented in a base, as
the rubber, with nut and screw to fasten. The frames are
made of mahogany or rosewood, highly polished, and the
brass work elegantly finished. The plate and all the pillars
are attached by nut and screw, and may be taken off for
convenient transportation.

Price, 16-inch, $20.00 and $25.00.

20-inch, $34.00 and $38.00.

24-inch, $50.00.

30-inch, $85.00.

36-inch, $130.00.

42-inch, $200.00.

Nairne's Cylinder Electrical Machine (Fig. 271, next page)
consists of a hollow cylinder of glass, usually eight to ten
inches in diameter, supported on a rectangular base, as in
the preceding machines described. Two hollow metallic
conductors, about twenty inches in length and four inches
in diameter, having hemispherical ends, are placed parallel
to the cylinder, one on each side, upon two insulating pillars
of glass, which are cemented into two separate pieces of
wood, that slide across the base so as to allow of their being
brought within different distances of the cylinder, and having
screws entering the base for clamping fast. To one of these
conductors the cushion is attached, being fastened to it by
a spring and two brass rods fastened to the cushion, the
rods entering holes for the purpose in the conductor, and
moving freely therein ; the spring causing it to press equally
against the cylinder in every part of its revolution. The
pressure of the cushion is also further regulated by the
adjusting screw at the base. From the upper edge of the
cushion there proceeds a flap of black silk, which is

ELECTRICAL APPARATUS.
Fig. 271.

253

on the cushion about a quarter of an inch from the upper
edge ; it extends over the upper surface of the glass cylinder
to within an inch of a row of metallic points, proceeding like
the teeth of a rake from a horizontal rod, which is fixed to
the adjacent side of the opposite conductor. The motion is
given by a simple handle — formerly a multiplying wheel
was used, but it has many disadvantages and is more labori-
ous. The conductors are usually made of metal, japaned
black, perforations being made at the ends and on the top

254 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

about the size of a quill, for the purpose of attaching wires
and other kind of apparatus. This machine is the best for
showing the effect of positive and negative electricity. The
conductor to which the rubber is attached is the negative,
and the one having the points the positive or prime conductor.
If it be required to accumulate positive electricity, a chain
must be carried from the negative conductor to the floor.
If, on the other hand, negative electricity be required, then
the positive conductor must be put in connexion with the
ground, and the other insulated.

Price, with two conductors, 8 inch, $22.00.

" " " 9 inch, $25.00.

" " " " 10 inch, $28.00.

To use the Electrical Machine. — Let the machine be care-
fully wiped with a clean silk or linen cloth, to free it entirely
from dust ; spread a little amalgam evenly along the cushion,
turn the machine with rapidity for some time, observing if
the whole surface of the cushion is covered with the amal-
gam ; remove all the amalgam adhering to the glass, attach
a chain to the rubber to connect with the floor, or place the
hand on the rubber, gently pressing it, frequently wiping the
whole machine with a silk cloth free from dust, which in an
excited state it readily attracts.

The most powerful excitation of the machine is produced
as follows. Let the machine be placed within the influence
of a good fire, but not so near as to injure any of its parts
by the action of the heat. With a flat round-pointed knife
spread a little amalgam evenly along the cushion, and return
it to its place ; turn the cylinder a few times round ; then
take off the cushion, and observe carefully those parts on its
surface that have not been touched by the cylinder while
revolving ; on these parts put a little more amalgam, and
repeat the process of turning the cylinder, and supplying
ihe defective parts with amalgam, till every point of that
part of the surface of the cushion which presses on the
cylinder appears to be properly supplied with amalgam.
Take now a piece of leather, about five or six inches square,
and spread over one side of it a quantity of amalgam;
Inrow back the silk flap, and, turning the machine gently
round, applied the amalgamed side of the leather to the
cylinder, for the space of two minutes or more, as circum-
stances may require, during which time the excitation will be

ELECTRICAL APPARATUS. 255

observed to increase rapidly. The cylinder must next be
wiped perfectly clean with an old silk handkerchief, and
afterwards with a soft dry linen cloth. Let the cushion be
again removed, and the amalgam which appears above and
below the line of contact with the cylinder carefully scraped
off, the silk flap wiped with the linen cloth, and the whole
returned to its place and made fast. If now the cylinder be
turned slowly round, streams of the electric fluid will be
seen rushing from the silk flap round the lower pan of the
cylinder, attended with a hissing and snapping noise, while
large brushes of the same, of several inches in length, may
be observed flying off from the lower edge of the silk into
the surrounding air. The machine is now fit for use, and
may be fastened to the table ; after which the whole of its
parts are to be well wiped with a warm and dry linen cloth,
to free them from dust.

The operator, however, must not expect this high and
rich state of excitation to be of long duration. The cylinder
will soon cool ; dust will be attracted by the action of the
machine ; and the moisture produced in the air of the room
by the breaths of his audience, will, by their united effects,
render all his efforts to produce a copious supply of elec-
tricity entirely fruitless.

To remedy this defect, which gentlemen who deliver
public lectures on electricity have often found to be a griev-
ous one, and surround it with a dry atmosphere entirely
preventing the deposition of the moisture of the room from
settling on the machine, provide a box of thin plate iron, ten
or twelve inches long, four inches wide, and one inch and a
half in depth, with a lid to fit very easily over it. In this
box a piece of bar iron, of about six inches in length, three
in breadth, and half an inch in thickness, after being heated
in the fire to a dull red heat, is to be placed, the lid of the
box put on, and the whole, on a suitable iron stand, placed
under the cylinder, on the board of the machine, in a longi-
tudinal direction. The radiation of heat from the iron will
effectually preserve the equality of the temperature of the
surrounding air for a considerable length of time, and in-
deed for any length of time required, since, by employing
two bars of iron, the one may be kept in the fire, while the
other is in the box, and thus no other interruption in the
course of the experiments will be necessary beyond what is
occasioned by the changing of the irons. By this means

256 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

the machine may be made to act in full vigor under the
most disadvantageous circumstances.

Fig. 272.

fke Cylinder Electrical Machine (Fig. 272, as above)
consists of a hollow cylinder of glass, usually about six tc

ELECTRICAL APPARATUS. 257

ten inches in diameter, and from eight to fourteen inches in
length, supported on a rectangular base by two upright
turned columns, by means of caps on the ends of the cylinder,
the one having a short pivot, the other a long one, passing
through the column, and terminated by a winch and handle
by which the cylinder is turned on its axis. The upper part
of the 'column is divided horizontally at the centre of the
pivot, or axle, and secured by screws each side of the axle ;
by this arrangement the cylinder may easily be taken out
and put in the frame. Before the cylinder is a cushion,
which extends in length to within an inch of either end of
the cylinder, which should be soft and yielding ; the cushion
is supported by a glass pillar where negative electricity is
required, but more commonly by a turned mahogany pillar,
having at its base a slide to move backwards and forwards,
with a stout screw to clamp it fast, whereby the pressure on
the cushion can be regulated ; the conductor is a cylinder
of metal from fourteen to eighteen inches in length, and
about four inches diameter, with rounded ends, usually
japanned black, and is supported on the side of the cylinder
opposite the rubber, having a row of brass points on the side
towards the cylinder for collecting the fluid ; there are
sockets with holes at each end of the conductor, and also
on the top for attaching apparatus, wires, &c. To the up-
per edge of the cushion is attached a piece of black silk, of
the width of the rubber, which extends over the cylinder to
within an inch of the row of points.

Price, 4 inch, $ 8.00 ; 5 inch, $10.00.

" 6 " $12.00; 7 " $14.00.

" 8 " $16.00; 9 " $18.00.

10 " $22.00.

The Small Cylinder Electrical Machine. — This plate (Fig.
273, next page) represents the cylinder electrical machine,
in the simplest and one of the most convenient forms in
which it can be constructed. The base is a rectangular
piece of wood, having upright pieces of wood firmly attached
at the base, and supporting the caps attached to the cylin-
der ; to one of which is a handle, by which the cylinder is
turned. On one side is a cushion of leather fixed to a pillar,
and having a screw at the base to regulate the degree of
pressure on the cylinder. On the other side of the cylinder
i*i R metal cylinder with rounded ends, supported by a ghiss

258 BEXT.T. PIKES, JR., DESCRIPTIVE CATALOGUE.

Fig. 273.

rod. On one side is a row of sharp points, to draw the
electricity from the glass ; and on the other, a hole, having
a wire with a brass ball thereon. A flap of black silk, or
oiled silk, is attached to the rubber, to prevent the dissipa-
tion of the electricity from the surface of the cylinder before
it reaches the points. Price, 4-inch, $8.00.

" 5-inch, $10.00.

" 6-inch, $12.00.

The Electrophorus. — (Fig. 274, next page.) — The electro-
phorus is certainly a very remarkable source of electrical
accumulation, and is an instrument which, for many light
experiments, forms a good substitute for the electrical
machine. It consists of a metallic plate, with a rim about
half an inch deep, containing a resinous plate, formed of
equal parts of shellac, rosin,. and Venice turpentine melted
together, and about ten to fourteen inches in diameter, and
half an inch thick, on which rests a brass or metal plate,
from eight to twelve inches in diameter, having well-rounded
edges, and a glass handle at the centre about ten inches
long, for the purpose of lifting without drawing off the
electricity ; a wire with a brass knob is usually connected
with the plate for taking the sparks ; a, a, a, represent
brass rods connected with the lower plate having their tops
level with the plate of resin, by which is avoided the trouble

ELECTRICAL APPARATUS. 259

Fig. 274.

and tediousness of establishing a communication between
the insulated cover and the earth by means of the finger.

To use the electrophorus, rub the upper surface of the
resinous plate with a piece of dry fur (cat's skin is reckoned
the best), and it will be excited negatively. Place the upper
conductor upon it, and then raise the same by its insulating
handle ; it will be found to exhibit very faint, if any elec-
trical signs. Replace the conductor, and whilst it lies on
the surface of the excited plate, touch it with a finger or
any other uninsulated conductor, and then raise it again by
its handle.

It will now be positively electrified, and afford a spark ;
if it be then replaced on the resinous plate, touched, and
again raised, another spark will be procured, and this pro-
cess may be repeated for a considerable time without any
perceptible diminution of effect. Jars may be charged by
bringing them in contact with the conductor each time it is
lifted ; with an instrument of this kind, only six inches in
diameter, Cavallo charged a jar several times successively,
and such was the strength of the charge that it was capable
of piercing a card.

This instrument, properly constructed, has been known
to retain its electricity so long as three weeks, without requir-
ing fresh excitation.

Price, $3.00 to $6.00.

260 BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

Fig. 275.

Insulated Stool. — (Fig. 275.) — This consists of a ma-
hogany board of well-baked wood, having stout legs,
cemented in sockets for the purpose, sometimes having
screws for separating them from the top, for convenient
transportation. To use ; having wiped it clean and dry,
let a person stand upon it, holding in his hand a chain or
wire communicating with the prime conductor; on setting
the machine in action, sparks of fire may be drawn from any
part of his person, he becomes indeed a part of the conduc-
tor, and is strongly electrified ; his hair will stand on end,
and if he hold in his hand a silver spoon, containing some
warm spirits of wine, another person may set it on fire by
touching it quickly with his finger.

Price, $3.00 ; with legs in brass sockets

to unscrew, - $4.00 and $4.50.

Fig. 276. LegdenJar—(Yig. 276)— is so called from

the circumstance of its properties having been
first observed at Leyden. It consists of a
glass jar of any convenient size, usually a
quart, having the outside and inside coated
with tin foil to within two or three inches of
the top, and a brass wire, the upper part of
which terminates in a ball of the same metal,
and the lower part in a fine chain, or a piece
of fine wire, that it may touch the inside of the
jar, passing through a cap of baked wood
which fits into the mouth of the jar. If a jar
thus constructed be held by the lower part
with the hand, and the knob be brought into
contact with the prime conductor while the machine is in
action, it will become charged ; and if a communication be
then formed between its outside and inside coatings, by the
other hand being brought to the knob, that sensation called

ELECTRICAL APPARATUS. 261

the electrical shock will be felt, and the jar will thus be
discharged. Price, pint, $1.00 and $1.25.

" quart, $1.25.

" half gallon, $1.75.

" gallon, $2.50.

Discharger. — (Fig. 277.) —
This is formed of two wires
with balls at the outer ends,
and jointed at the lower ends
where they are received into
a socket, into which a glass
handle is fastened. Hold the
common discharging rod firm-
ly, and discharge a phial by
it, he will not receive a shock.
If the phial be a very large
one, or if he hold it lightly,
he will feel perhaps a slight
tingling of the fingers when
the shock passes, but this is
all. If he be furnished with
the glass-handled discharging rod, or jointed discharging
rod, as it is called, he may, by setting its knobs at a proper
distance, discharge even the largest battery without danger.
It is usual for the sake of convenience to fasten a chain to
one of the arms of the discharging rod, which communicates
with the outside of the phial.

Price, $1.25 to $2.00.

" with moveable joints, $3.00 and $4.00.

Pith Ball Electrometer — (Fig. 278, next page) — consists
of a small stand, supporting a glass rod, bent at right angles
at the top, and having a hole to attach a pith ball, which is
suspended by a silk string. If an excited glass tube be
held near the electrometer, the ball will be attracted, and
after adhering for a short time, it will be repelled to a con-
siderable distance, nor will it again be attracted until it has
touched some body connected with the earth, and thus given
up the electricity which it had acquired from the tube, or
until, by remaining undisturbed for some time, it has lost it
by dissipation into the atmosphere. Price, 50 cts.

262

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

Fig 278.

Fig 279.

If two pith balls be suspended by
two silk threads, and excited either by
glass or by resin, on removing the ex-
citing material, they
will no longer fall
into the vertical po-
sition, but repel each
other in the manner
shown in Fig. 279,
the balls acquiring a
property relative to
each other similar to
that which the glass
and single ball ex-
hibited after contact
in the preceding ex-
periment.

Price, 50 cts.

Fig. 280.

le Balance Electro-
meter.—{Fig. 280.)— This
is an instrument of great
delicacy. It consists of a
fine beam of metal, sus-
pended on a pivot affixed
to a glass rod in the cen-
tre. It is accurately ba-
lanced, and has at each
end a pith ball. The glass
rod must be very dry when
the instrument is to be
used ; an excited stick of

sealing-wax or glass held towards one end will occasion it
to move round its centre, and thus indicate plainly the ex-
citement of the wax, or glass. Price, $1.00.

The Quadrant Electrometer. — This instrument (Fig. 281,
next page) consists of an upright stem of wood, furnished at
the lower end with a brass ferule and pin, by which it may
be inserted in the conductor. To the upper part of the stem
is affixed a graduated semicircle of box wood, or ivory, at
the middle of which is supported on an axis, an index, which
consists of a very slender ivory rod, and reaches from its

ELECTRICAL APPARATUS. 203

axis at the centre of the graduated plate, to the ferule at the
end of the stem ; and to its extremity is fixed a delicate
pith ball. This index rises as the charge increases, and the
strength is determined by the degree indicated on the gradu-
ated circle. Price, in box wood, $1.25.
" in ivory, $1.75 and $2.00.

Fig. 282. Fig. 283.

Bennett's Gold Leaf Electrometer. — (Fig. 282, as above.)
— Consists of a brass' foot, which supports a glass tube about
two and a half inches wide and five long. This has two
slips of tin foil pasted on the opposite sides, as represented.
The cylinder is closed at top by a brass cap, which fits
tight round the sides, but takes off and on, in order that
if the two slips of gold leaf which hang from the middle of
the cap in the inside should become broken, they may be
repaired. The cap should not in any other case be removed.
The gold leaves are about three inches long, and a quarter
of an inch wide ; they are best fastened on by a little piece
of flatted brass, soldered to the inner side of the cap, and
the leaves attached by gum water, gold size, paste, or any-
thing similar. They should hang so as to touch each other
when not in an electrified state, and when divergent, as
shown in the cut, they should approach to the slips of tin
foil on the glass. The cap has occasionally a point which
screws upon it, as shown ; this, however, is never used, except
in trying experiments upon the electricity of the atmosphere.

Price, $2.50.

Saussure's Gold Leaf Electroscope, which is represented in
Fig. 283, as above, differs from the former in the manner

204

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

in which the gold leaves are insulated. The cap is a flat
plate with a wire soldered beneath. The gold leaves are
soldered at the lower end of the wire, and the whole wire
is inclosed in a giass tube. The outer surface of this tube
is best covered with sealing-wax, as the insulation of resinous
substances is much better in damp weather than that of
glass, which rapidly attracts the moisture of the breath, or
of the apartment. The diameter of the glass may be four
inches, the height of it eight inches. The size of the plate
at top from two to four inches, as most convenient. The
cap which incloses the top of the glass, and into which the
glass tube is cemented, may be of wood or metal.

Price, $2.00.

Volta's Condenser (Fig. 284) shows a pair of these con-
densing plates attached to a gold leaf electroscope. The
plate, A, is connected with the cap, and is of course insu-
lated. The plate, B, is supported upon glass, but is con-
nected with the ground by the chain ; it turns upon a joint
at c. It is sometimes connected with another condenser
when the plate B becomes insulated by taking off the chain.
The two plates have a thin coat of gum lac varnish on their
inner sides, to prevent contact, and in consequence entire
dispersion. To use the instrument, touch the cap or plate,
A, with the excited body, B being withdrawn, then approach
B to A, and touch A again ; it may afterwards be made to
touch a third or fourth time, or more, until the gold leaves
show signs of divergence. Price, $6.00.

Fig. 285.

fiennefs Electrical DouUer. — (Fig. 285, as above.)— This

ELECTRICAL APPARATUS. 265

instrument is an improvement upon Yolta's, it being more
susceptible. It consists, as the cut represents, of a simple
gold leaf electrometer, the top of which is a flat metallic
plate, marked A, of a similar plate, B, which has a glass
handle, and of a third plate, c, also with a glass handle.
The plates c and B are covered on their under-sides with
sealing-wax varnish. To use the instrument ; first put the
plate B upon A, touch the plate B with the finger, and then,
before the finger is removed, touch the plate A with the
object to be tested. Take away the object, and also the
finger ; take up B by its handle ; place c on B, and touch c
with the finger. By this a portion of the electric fluid is
disturbed in c, so that c becomes electrified plus, or minus,
in the same manner as A. Place B upon A, and touch B
with the finger, and apply the edge of c to A ; the electricity
of c will then flow to A. Remove c, take the finger from B,
and raise B from A. Proceed in the same manner for three
or four times more, until so much electricity is accumulated
in A as to occasion the divergence of the gold leaves.

Price, $5.00.

Fig. 28,

The Universal Discharger. — (Fig. 286, as above.) — An in-
strument that will be found convenient in a great variety
of experiments in which the electrical battery is to be used.
It consists of a flat board, about fifteen inches long, four
broad, and one thick, having two glass pillars cemented in
two holes upon the board, and furnished at top with brass
caps, each of which has a turning joint, and supports a
spring tube, through which the wires slide. Each of the
caps is composed of three pieces of brass, connected so that
the wires, besides their sliding through the sockets, have a
horizontal and vertical motion. Each of the wires is fur-
nished with an open ring at one end, and at the other it has
a brass ball, which, by a short spring socket, is slipped upon
the pointed extremity, and may be removed. There is a
23

266

BENJ. PIKES, JR., DESCRIPTIVE CATALOGUE.

circular piece of wood, having on its surface a slip of ivory
inlaid, and furnished with a foot, which is fastened in the
middle of the bottom.

To this* discharger belongs the small press (Fig. 287, pre-
vious page), the stem of which fits into the socket, instead of
the circular table. On the top of the stem are two oblong
boards, which are pressed together by means of two screws.
Between these boards may be placed any substance which re-
quires to be pressed while the electric fluid is sent through it.

The construction of this instrument is such as to enable
the operator to use it with advantage in numerous experi-
ments, such as the oxidation of metallic leaves between slips
of card or of glass ; splitting small pieces of oak, firing
gunpowder, &c.

By far the most interesting and brilliant application of the
powers of the Leyden jar is the melting of metallic wires.
When a strong charge is passed through a slender iron wire,
the wire is ignited or dispersed in red-hot globules. The
power of large batteries was formerly considered essential
to the production of this effect ; but if the wire be suffi-
ciently fine, a single jar, exposing a coated surface of about
190 square inches, Will be found sufficient to exemplify the
experiment. Price, $6.00 and §7.50.

Fig. 288. Medical Jar. — (Fig. 288.)— This is like an or-
dinary Leyden jar, covered and lined to a certain
height with tin-foil, as at B. A wooden cap is
then prepared for it, and a hole just admitting a
glass tube, A, is bored in the middle of the cap.
The tube reaches below to within two inches of
the bottom, and projects upwards above the
cap, about three inches. This tube is also partly
lined and covered with tin-foil, so placed that
rather more than an inch of the glass is left un-
covered at the lower end, and about two inches
at the upper end. The tube is cemented to the
top of the bottle, and a smaller cap cemented on
the top of the glass tube ; but before this last is
cemented on, three holes are drilled in it ; one
for a hook wherewith to suspend the phial from the con-
ductor, the two others are to be left open ; one of them to
admit a wire to touch the inner coating of the tube, the
other a second wire, sufficiently long to reach to the coating

ELECTRICAL APPARATUS.

267

of the phial — these are shown in the cut at c and D. A
wire is also twisted round the outer coating of the inner
tube, which projects outwards sufficiently to touch the inner
coating of the phial. On the outer coating of the phial is
fastened a hook, marked F, for the convenience of attaching
a chain. Price, $2.50.

289- Discharging or Medical Elec-

trometer.— A Ley den jar will
endeavor to throw off its elec-
tricity from the inside to the
outside, the more as it becomes
charged with greater intensity ;
and if the two coatings be placed
so close to each other that the attraction between the two
coatings overcome the resistance of the glass, a discharge
necessarily takes place. On this fact the discharging elec-
trometer is constructed. A is supposed to be a cross sec-
tion of the prime conductor of an electrical machine. B is
a brass cap, forming the end of the electrometer. It is made
with a wire beneath to fit the hole of the conductor. C is a
bent glass tube. D a brass ball at the end of it. E is a
wire with a brass ball at each end, which wire is movable
backwards and forwards. When a shock is to be taken, the
ball E is placed at a certain distance from the surface of A.
A is connected with the inside of the Leyden jar, which
communicates the shock, and the chain is connected with
the outside of the jar. When the jar is charged to such a
degree of intensity as to acquire force enough to strike across
from A to E, the discharge will spontaneously take place.
The ball at E must be set at a greater or less distance from
A, according to the strength of shock required. If a shock
is to be given to a company, when this electrometer is to be
used, they must form part of the circuit between the outside
of the bottle and the electrometer. Price, $2.00.

Cuthbertson's Balance Electrometer (Fig. 290, next page)
is an excellent and elegant regulator of the strength of the
charge requisite for fusing different lengths of wire, expe-
rimenting on metallic oxides, &c. .It consists of a mahogany
base, A B, about eighteen inches long, and six inches wide,
in which are fixed two glass supports, mounted with brass
balls, the one, c, set in the middle of the base, and the other,

268 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 293.

d, about seven inches therefrom ; under or at the side of one
of the balls, d, is a hook ; the other ball, e, has at its side a
brass rod, c e, with upright arm, c f, about four inches long,
each having balls, c f, at their ends ; the rod is about seven
inches long, extending in a direction opposite to the insulated
ball with a hook ; also connected by a brass tube about four
inches long with another ball, b, formed of two hemispheri-
cal brass cups, the one fitting within the other, and within
this is balanced a brass rod, g h, about fourteen inches long,
with a knife edge centre in the middle, placed a little below
the centre of gravity, and equally balanced with a hollow
brass ball, g h, at each end, the centre or axis resting upon
a proper shaped piece of brass fixed in the inside of the ball,
each part of the hemisphere being cut out to permit the end
towards the insulated brass ball to descend, and the other to
ascend ; to the arm is attached a small slider moving freely
over a line divided into 60 grains, the slider to be set at the
number of grains the experiment requires.

To use the instrument ; suppose the slider to be set at 15
grains, it will cause the arm, g h, bearing the slide, to rest
on the ball,/, beneath, with a pressure equal to that weight ;
as the charge increases in the jar, or battery, the balls be-
come more and more repulsive to each other, and when the

ELECTRICAL APPARATUS.

269

force of this repulsion is sufficient to raise 15 grains, the
arm, g, rises, the slider moves forward, and the ball, h, at
the other end of the arm, coming rapidly in contact with the
ball, d, connected by the chain with the jar, discharges the
electricity accumulated. And as the force of the repulsion
depends upon the intensity of the charge, the weight it has
to overcome affords a measure of this intensity, and enables
the experimenter to regulate the amount. A quadrant
electrometer, K, is also usually attached to the top of the
instrument. Price, $8.00 to $10.00.

Fig. 291.

BEMJ.PIKE JR294BBOA'DWAY.NV

I - ^IBrihiiilii

Electrical Battery, with four Jars. — (Fig. 291.) — When
great force is required from the electric fluid, a number of
jars of the above description are placed on a metal coating
which forms a communication between their outside coatings
and the earth, and the insides of the jars have conducting
wires which pass to the prime conductor. In this manner
any number of jars may be charged with the same facility
as a single one, and from the powerful effect of the electric
fluid when it is thus collected, it is called an electric battery.
One with four jars is represented in the above figure.

Price, four gallon jars, $10.00.

" half " $8.00.

" quart " $6.50.

23*

270

BENJ. PTKE'8, JR.. DESCRIPTIVE CATALOGUE.

Electrical Battery, with fifteen Jars. — (Fig. 292.) — This
represents an electrical battery of fifteen jars in the act of
being charged from the conductor of an electrical machine,
with Cuthbertson's balance electrometer, and an arrange-
ment for striking metallic oxides attached.

Price, fifteen quart jars, $22.50.
" half gallon " $30.00.
" gallon " $40.00.

Leyden Jar with Movable Coatings. — (Fig. 293, next page.)
— This consists of a glass jar, with a double set of movable
coatings, either of which may be adapted to it at pleasure,
the outer coating being a tin case large enough to admit
the jar easily within it, and the inner coating a similar case
sufficiently small to pass readily in the inside of the jar.
The charging wire of the inner ( iting should be surrounded

ELECTRICAL APPARATUS.

271

by a glass tube covered
with sealing-wax, to serve
as an insulating handle, by
which the inner coating
may be lifted from the jar
when that is charged with-
out communicating a shock
to the operator. Arrange
the jar with its coatings, and
charge it, it will act in every
respect as an ordinary coated jar ; charge the jar, and
without discharging it, remove the inner coating by its insu-
lating handle. If this coating, when removed, be examined,
it will be found not at all, or but slightly electrified ; lift the
jar carefully from within its outer coating, and examine that
— it also will evince no sign of electricity. Fit the jar up
with -the other pair of movable coatings, that have not been
electrified, and apply the discharging rod ; an explosion and
spark will ensue, proving that the coatings are only the con-
ducting materials from one side of the glass to the other,
and that it is the glass itself on which the fluid is accumu-
lated. The annexed cut shows the usual form of these jars.
Price, with one set of coatings, $2.00.
" two " " $3.00.

Magic Pictures. — (Fig. 294.) — Fig. 294.

This consists of a frame of maho-
gany, or other wood, about twelve
inches square, sometimes having a
handle on one side to hold by,
having in a groove a plate of glass
confined, about ten inches square,
the middle of which is coated .with
tin-foil on both sides of the glass
to within one or one and a half
inches of the edge, one side of
which is connected with the frame
and handle, and the other having
a picture pasted over the tin-foil.
To use, lay a piece of money on
the picture, and holding it by the
frame or handle, charge the picture by presenting a ball
from the conductor to the money. When charged, take

272

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

hold of the frame by the other hand, at the handle or some
other part of the frame, and direct another person to hold
that part which you have just quitted with one hand, and
to take off the money with the other. His attempt to do
so will discharge the sheet of glass, and he will receive a
shock in the fingers, while he will be quite unable to take
off the money. Price, $1.75.

Sulphur Cone. — (Fig. 295, as below.) — This apparatus is
formed from a large wine glass. This is cleaned, and a part
of the outside, as represented, covered with tin foil. A wire
is twisted round this covered part, and bent so as conve-
niently to hold a pair of pith balls suspended on very fine
wires, or on linen threads. Within the glass is poured
melted sulphur, to about the same height, or a little above
the edge of the tin foil, and the end of a glass rod, or else
of a silk cord, dropped into the sulphur while melted.

Fig. 296.
Fig. 295.

To use, lift up by the glass handle, the sulphur within
the conical glass, and, at the moment of separation, the pith
balls will diverge, or separate from each other. Let the
sulphur drop down again into the glass, and this action of

ELECTRICAL APPARATUS.

273

the balls will cease. Again produce separation of contact,
and they will again diverge ; and thus, for a considerable
time, the alternate action will be kept up, even indeed for
days and weeks. Price, $0.75.

Electrical Bells. — (Fig. 296, previous page.) — The electri-
cal bells furnish a pleasing illustration of the attraction and
repulsion of the electric matter. They are variously con-
structed, but the form exhibited in the figure is one of the
simplest. The two outer bells are suspended by brass
chains ; the middle bell and the two clappers by fine silk
threads. When the bells are attached to the conductor,
and the machine is turned very slowly, the fluid will pass
along the chains to the two outer bells, but will not pass
along the silk to the clappers and middle bell. Thus the
outer bells being charged with an extra quantity of electri-
city, will attract the clappers, but the moment they touch
the bells they become charged, and are repelled with such
force as to cause them to strike against the middle bell, on
which they deposit their electricity, and are again attracted.
By this means a constant ringing is kept up while the
machine is turned. From the inside of the middle bell a
brass chain passes to the table, for the purpose of convey-
ing away the fluid deposited on it by the clappers.

Price, $2.00.

Fig. 297.

Set of two Electrical Bells. — (Fig. 297.) —
This is the simplest form of the experiment,
one of the bells communicating with the
prime conductor, and the other with the
ground ; they are made to ring by the alter-
nate blows of a small brass ball suspended
between them. Price, $1.25.

Chime of five Bells. — Fig. 298, next page,
represents a more elegant form of mounting
the electrical bells. It consists of a swelled
glass pillar, on the top of which is cemented a cap, bearing
a brass cross ; the four outer bells are affixed to the ends
of this by wires, and the clappers are suspended from the
middle by silk cords ; the middle bell communicates with
the ground by the mahogany foot which supports the

274 BENJ. PIT Vs, JR., DESCRIPTIVE CATALOGUE.

Fig. 300

Fig. 298.

;hole. To use, the cross is connected by a chain with the
mme conductor, when a pleasing chime will commence.

Price, $4.00.

French Arrangement for illustrating the Chiming of Bells
by Electric Action. — Fig. 299 represents the apparatus, one
of the bells being in connexion with the interior coating of a
Leyden jar, while the other bell communicates with the
outer coating. When the jar is moderately charged, the
vibration of the little ball, which is suspended between the
bells by a dry filament of silk, produces the chiming, which
is more or less rapid as the distance between the bells is in-
creased or decreased. Price, $4.00.

Electrical Plates for Dancing Images. — Fig. 300, as above,
consists of a metallic plate six or eight inches in diame-
ter, supported on a stand, and another plate of somewhat
smaller size, suspended to the prime conductor at about
three or four inches distant. Place on the lower plate any
little figures cut out of paper or pith. Take care that the
lower plate is supported upon some conducting substance ;
turn the machine, and the figures will raise themselves, and
fly up and down between the two plates, forming a most
ludicrous dance.

Support the lower plate upon a glass bottle, or other

ELECTRICAL APPARATUS.

275

insulator, and although all the rest of the apparatus remain
as before, yet the figures will not dance. The reason is this,
the upper plate being charged by its connexion with the
machine, the figures are attracted by it, they becoming charg-
ed are repelled by the upper, and attracted by the lower
plate. When they touch this their charge is removed by
that contact, and conveyed to the earth, while the figures
jump again for a fresh supply, and thus they move alter-
nately from the one to the other plate. When the lower
plate, however, is insulated, the extra portion brought to it
cannot escape, and it becomes charged in the same manner
as the upper one, therefore the figures have no tendency to
move between them.

If in cutting out the figure the head is heavier than the
feet, it will dance head downwards ; damping the feet in
the mouth will usually remedy the defect, but this, at the
same time, gives them a tendency to adhere to the upper
plate, while wetting the head makes them dance on the
lower plate. Female figures usually dance more regularly
because of the weight of the lower part of the dress. In
all the figures the head should be somewhat pointed, either
by the adjunct of a steeple-crowned hat, or something similar
put upon it. Price, in copper, $1.25 and $1.50.

Electrical Plates for Dancing
Images, with adjusting Rod. — A
more elegant arrangement for
dancing images (Fig. 301) con-
sists of a polished mahogany base,
about 8 inches long and 10 inches
wide, on which is fastened a me-
tallic plate, about 8 inches in
diameter, having a hook connect-
ed with the plate from the under
side of the base. A glass pillar,
attached to a brass base at the
bottom, and having at the top a
cap, supporting a curved wire,
terminating in a ball having a
hole, through which a rod slides
vertically, one end of which has
a knob, and the other a metallic plate, with well rounded
edges, and supported directly over the plate in the base.

270

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

and may be placed at any distance therefrom, and fastened
by a screw attached to the ball through which the rod
passes. Price, $3.50.

Fig. 302. Dancing Pith Balls. — (Fig. 302.)

— The dancing pith ball experiment
is exhibited as follows. Fasten to
the conductor of the electrical ma-
chine, a pointed wire. Mold a dry
and warm tumbler over the point and
turn the machine. After a few turns
the tumbler will be charged within-
side with positive electricity. Place
upon the metallic plate (the larger
plate used for the dancing images
will answer) about a dozen pith balls,
and cover them over with the charged
tumbler ; they will now jump up and
down, each one conveying some of
the fluid away from the glass, and
not towards it. They will continue to
dance for a long time, and when their
motion has ceased altogether, it may
be renewed by a touch of the hand to the outside of the
tumbler, when a fresh portion of electricity will be set
free on the interior, and the attraction and repulsion of the
balls will again take place, and thus for many times success-
ively the action will be renewed until the glass returns to
its natural state.

The experiment may be varied thus. Hang to the con-
ductor a chain, which touches this tumbler ; upon turning
the machine, although glass intervenes between the exciting
power and the balls acted upon, yet the balls will fly rapidly
up and down within the glass tumbler. In this instance,
the outer part of the glass is by contact electrified posi-
tively ; the inner part, therefore, will be. by induction,
(afterwards to be explained), electrified negatively ; and
the balls are flying up and down to supply the deficiency
of the glass, each ball coming to deposit its load, and flying
down again for another.

Price, pith balls per dozen, $0.25.

ELECTRICAL APPARATUS.

277

Cylinder for Dancing Pith Balls. — (Fig. 303.) —
This electrical apparatus consists of a glass cylinder
having metallic ends, one end supported on a small
stand, the other having a knob, or hook, to connect
with the prime conductor of an electrical machine ;
on exciting the machine, the pith balls placed
within the cylinder will dance up and down, carry-
ing the electricity from the upper to the lower
plate.

Price, $1.50.

Fig. 3!>3.

Diverging Threads. — (Fig. 304.) — Tie
twenty fine linen threads together at eacli
end, so that there may be about 8 inches
distance from knot to knot ; hang this by
a wire loop, fastened to one of the knots,
to the conductor of the machine. Upon
charging the conductor, the threads will
recede from each other, forming a curious
balloon-shaped body.

Expanding Threads. — Instead of tying
the threads at both ends, let the lower end
be loose, and upon turning the machine
they will form a brush. Price, 25 cts.

The Head of Hair. — Fis. 305.

(Figs. 305 and 306.) —
These are usually carved
figures of wood, having
long hair on their head.
They are supported by a
wire from the prime con-
ductor. When electri-
fied, the hair stands on
end in the most grotesque
manner. Each fibre is
in a state of repulsion to
its neighbor, but present
the point of a penknife,
and they will all fall
down. Price 75 cts. and $1.00.

24

Fig. 304.

Fig. 303.

278

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

Fig. 337.

Radiating Feathers. — (Fig.
307.) — This is a metallic ring,
supported on a glass pillar, and
at six or eight equally distant
points around this ring tie a
thread, not silk, a few inches
long, the other end of which
bears a feather. Connect the
metal ring with the conductor
of the machine, by a wire or
chain, and the feathers being
electrified will repel each other
until they will stand at equal
distances like the spokes of a
wheel. Price, $1.50.

Fig. 308.

The Electrical
Swing (Fig. 308) is
another amusing in-
strument, and acts,
as will be immedi-
ately perceived, up-
on the principle of
attraction and re-

Eulsion. The insu-
lted brass ball, A,
is connected with
the prime conductor,
while the opposite
ball, B, communi-
cates with the earth.
The light figure re-
presented as sitting
on a silken cord is
first drawn towards
A, where it receives
a charge which it
discharges on B, and thus is kept swinging between the two
balls. Price, $3.00.

Electrical See- Saw. — (Fig. 309, next page.) — Consists of
a mahogany base about one foot long, supporting at its
centre a brass beam, after the manner of a scale beam, made

ELECTRICAL APPARATUS.

279

very light, and supporting near its extremities small figures.
A glass pillar supports a brass ball at one end of the stand,
and a metal rod another ball at the other end ; these balls
connected with the Leyden jar, will cause the beam to move
up and down with a pleasing effect. Price, $3.00.

Fig. 310.

Fig. 309.

L

O

Electrical Pendulum. — (Fig. 310, as above.) — This is a
plate of glass about ten inches square, mounted on a wooden
base, and having a delicate balance suspended on the top of
the plate, the ends having pith balls attached ; this is made
so as to vibrate easily, the balls alternately touching the
sides of the glass plate, which is coated with tin foil to within
an inch and a half of the edge, which, when charged, will
cause the pendulum to vibrate, and thus discharge the plate.

Price, $2.50.

Electrical Spider and Jar. — (Fig. 311, next page.) — A
small object in the shape of a spider, formed of cork, or pith,
having legs of thread, and supported by a silken thread
between two Leyden jars, or between one jar and a ball con-
nected with the outside coating of the jar, the spider will
be attracted from the one to the other, thus discharging the
jar. Price, $2.75.

Jar with Ball from Outer Coating. — (Fig. 312, next page.)
— There is attached to the outside coating of the jar, a, ex-
posing about a square foot of coated surface, a curved wire,
b, terminated by a metallic ball, c, rising to the same height
as the knob of the jar, d ; charge the jar, and suspend

280 BENJ. PIKE'S, JR. DESCRIPTIVE CATALOGUE.

Fig. 312.
Fig. 311.

Qe

midway between c and d by a silken thread, a small ball of
cork or elder pith. The ball will immediately be attracted
by d, then repelled to c, again attracted, and again repelled,
and this will continue for a considerable time : when the
motion has ceased, 'apply the discharging rod to the jar, no
spark or snap will result — proving that the phial has been
gradually discharged by the pith or cork ball, the motion of
which from d to c likewise proving the opposite electrical
states of the outer and inner coatings. Price, $2.50.

Fig. 313.

Electrical Flyer. — The electrical fly (Fig. 313, as above)
represents a light brass fly, consisting of fine wires pro-
ceeding from a common centre, and having their pointed
ends turned back at right angles, and all in the same direc-
tion. If this fly be poised on its centre on a pointed wire
inserted in the prime conductor, and the machine be put in

ELECTRICAL APPARATUS.

281

action, a stream of fluid will issue from each point, and pro-
duce a locomotion in the fly, propelling it in a direction con-
trary to that of the points : the points will of course appear
luminous, and if the room be darkened, a beautiful circle of
fire will be distinctly seen, formed by the revolution of the fly.

Price, $0.50 to $1.00.

Revolving Horsemen. — (Fig.
314.) — This is a very pleasing
experiment; it consists of a
swelled glass pillar, mounted
on a mahogany stand, having
a cap terminating in a point, on
which is balanced an electrical
flyer about twelve inches wide,
as described Fig. 313 ; to each
of the points is attached small
figures of horsemen; to the
cap is attached a hook for con-
necting with the prime con-
ductor, which, when excited,
will cause the horsemen to re-
volve with great rapidity.

Price, with 4 horse-
men,
" 6 " $3.00.

!.50.

Fig. 314.

Set of Electrical Flyers
(Fig. 315), consisting .of five
mounted ; one in the centre,
and four on branches from the
centre.

They sometimes are made
having one large flyer, and
four small ones, revolving on
the revolving flyer, causing re-
volutions within revolution.
Price, $4.50.
24*

Fig. 315.

282 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 316.

^m y

Electrical Orrery. — (Fig. 316.) — This apparatus is seen
above. It represents the sun, earth, and moon. The
earth and moon are balanced at their centre of gravity,
upon a pointed wire, bearing at its other end the sun : this
wire has a point projecting sideways near its furthest extre-
mity. The moon also bears a side point, thus (every part
being nicely balanced), the earth and moon revolve round
each other, and both together round the sun — making one
of the best possible illustrations of the real motion of these
heavenly bodies. Price, $2.50.

The Electrical In-
clined Plane. — (Fig.
317)— This is a beauti-
ful experiment, and sa-
tisfactorily shows that
the electrical matter is-
suing from a number
of points possesses force
sufficient to counteract
the power of gravity in light bodies. It consists of a board
of mahogany, fourteen inches long and four inches broad,
having four glass pillars, three-tenths of an inch in thick-
ness ; the length of the two longer is seven inches, and
that of the two shorter is five inches.

From the longer to the shorter pillars are stretched two
fine brass wires, parallel to each other, and tightened by
screws which pass through the brass balls which surmount

ELECTRICAL APPARATUS.

283

the pillars. On these wires the axis of the fly rests, the
ends of which are formed like a small pulley, having a
groove in them to prevent their slipping off the wires, and
to guide the fly when in action. It is obvious that if the fly
be placed on the upper part of the wires, it will roll down
them by its own gravity ; but when it has reached the
bottom of the plane, if the upper end of the wires be con-
nected with the machine while in action, the escape of the
fluids from the points will cause it to roll very rapidly up
the plane till it reach the top of it.

These experiments may be varied to a great extent, and
models of corn-mills, water-pumps, astronomical clocks, etc.,
constructed of cork and pasteboard, are readily put in action
by directing against their main wheels a stream of electricity
from a strong pointed wire inserted into the prime con-
ductor. Price, $3.00.

Fig. 318

The Electrical Sportsman. — (Fig. 318, as above.) — Tin's
experiment is to illustrate the fact that a jar will be liable to
discharge itself when the two coatings are too close to each
other. The inner coating of the Leyden jar is connected
with two wires, one of which proceeds to the birds — the
other proceeds to within a short distance of the muzzle of
the gun. The birds are made of small bits of pith, with a
portion of feathers to each, to represent wings. They are
attached to pieces of linen thread, four or five inches long.
The gun is connected with the outer coating of the wire pro-
ceeding from it to the figure, and a slip of tin-foil which is

284 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

pasted along the figure to the muzzle. Connecting the wire
with the electrical machine in action it will of course become
charged, during which time the birds will elevate themselves
by electrical repulsion ; when the bottle is charged to a cer-
tain extent, the distance between the muzzle of the gun and
ball near it will not be sufficient to restrain the passage of
the fluid, which wTill therefore pass between them, occasion-
ing at the same time a flash of light, a loud report, and the
falling of the birds. Price, with Leydenjar, $3.00.

without " " $1.50.

The Electrical Rope-dancer. — (Fig. 319.) — This consists of
two stout brass rods, having knobs at each end, and about a
foot long. The upper rod is connected with the conductor by
a small chain or hook ; the lower one is hung to this, at the
distance of two or three inches, by a silk thread at each end ;
the lower wire is also connected with the ground by a chain.
Place on the lower wire a paper or pith figure, and upon
putting the machine in action, it will move alternately and
briskly between them. In the cut given below, the two
wires appear unconnected with each other, the lower one
having a stand of its own. This is a better form of the ap-
paratus, because, when connected together by silk, the figure
put to dance is apt to cling to the silk, which destroys the
effect intended to be produced. Price, $2.00.

Fig. 319.

Electrical Swan. — (Fig. 320, as above.) — This is a small
metallic swan, made light and capable of floating on water.
Let the swan float in a basin of water, which is supported

ELECTRICAL APPARATUS.

285

upon a glass stand ; suffer a chain to fall from the prime
conductor to dip into the water ; turn the machine, and hold
a piece of bread to the swan, it will immediately turn to it,
and approach as if to eat the bread. Price, $0.50.

Fig. 3-21.

Fig. 322.

Rolling Glass Halls.— (Fig. 321, as above.)— This instru-
ment for rolling glass balls is an admirable contrivance for
illustrating electrical attraction and repulsion. Three or
four glass balls made as light as possible, are supported on
an insulated glass plate, on the under part of which strips
of tin -foil are so pasted as to form a broad circle or border
near the margin, and four radii to that circle ; on the upper
part of the plate is a flat brass ring supported on small
glass pillars, so as to have its inner edge immediately over
the exterior edge of the tin foil. The brass ring being in com-
munication with the prime conductor, and the tin-foil with
the rubbers of the machine, the ring and foil will be oppo-
sitely electrified. The glass balls being attracted by the
ring, become positively electrified in the part which comes
in contact with it. Thus electrified, they will be attracted
by the foil, and communicating the charge, return to the
ring to undergo another change. Different parts undergo
in succession these changes, and the various evolutions of
the balls are very striking and curious. Price, $5.00.

The Electrical Pail. — (Fig. 322, as above.) — This con-
sists of a small pail, two or three inches in diameter, with
a spout near the bottom, in which is a hole just large enough

286 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

to let the water out by drops ; it is to be filled with water
and made fast to the prime conductor ; on turning the ma-
chine, the water, which before descended from the spout in
small drops only, will fly from it in a stream, which in the
dark appears like a stream of fire ; or a sponge saturated
with water may be suspended from the prime conductor,
when the same phenomenon will be observed, which is re-
ferable to the mutual repulsive property of similar electrified
particles.

Suspend one pail from a positive conductor, and another
from a negative conductor, so that the ends of the jets may
be about three or four inches from each other. The stream
proceeding from one will be attracted by that which issues
from the other, and form one stream, which will be lumi-
nous in the dark.

Hang two pails about four inches apart on the same con-
ductor, and the streams which issue from them will recede
from each other. Price, $0.75 and $1.50.

F5&- m _ The Phosphorus Cup. —

Fig. 323 represents two
hollow brass balls, about
three quarters of an inch
in diameter, insulated on
separate glass pillars, by
which they are supported
at a distance of about two
inches from eash other ;
the upper part of each ball
is hollowed into a cup into
which a small piece of phosphorus is to be put. A small
candle has its flame situated midway between the balls, one
of which is connected with the positive, and the other with
the negative conductor of a powerful machine. When the
balls are electrified, the flame is agitated, and, inclining
towards the one which is negative, soon heats insufficiently
to set fire to the phosphorus it contains, whilst the positive
ball remains perfectly cold, and its phosphorus unmelted.
On reversing the connexions of the balls with the machine,
the phosphorus in the other ball will now be heated, and
will inflame. Price, $3.50.

ELECTRICAL APPARATUS.

287

Electrical Wheel.— (Fig. Fi«- 3:4'

324.) — This arrangement
is mounted on a wooden
base, having at each end a
glass pillar with a ball at
the top, supporting pointed
wires, which are fastened
towards each other, and
about four inches apart,

in the centre of which a very light vertical wheel, with
floats on the edge, is supported by a suitable stand. Upon
connecting the wires with the electrical machine, the one
with the positive conductor, and the other with the negative
conductor, and putting it in motion, the wheel will turn
from the positive to the negative side. Price, $5.00.

Electrical Saw Mill.— (Fig. 325.)— Fi*' 325

The electrical saw mill represented in
the cut, consists of two brass pillars,
supported on a mahogany base ; from
near the centre of the glass pillars
there is supported an axle, with six or
eight glass spokes, each terminated
with a metallic ball ; this revolves
easily just over a large brass ball at-
tached to the base. On each of the
pivots of the axle there is a crank,
turned in opposite directions, with rod
attached to each ; these alternately
draw up and down light frames repre-
senting saws, which are movable in a
framework supported on top of the
lass supports ; another large brass

ll being supported from the framework.

To use, connect the upper brass ball with the prime con-
ductor, and the lower ball with the table, or ground ; on
exciting the conductor, the nearest ball on the wheel will be
attracted by a large ball connected with the conductor, and
on being fully charged will be repelled by it, and thus bring
the next ball near, which in turn will be repelled ; these, in
coming near the lower ball, will be attracted and discharged ;
thus a constant carrying of electricity from the upper to the
lower ball will take place, and a rotary motion in the wheel

gl
ba

SJ88 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

be produced, which, by means of the cranks and rods, will
move the saws up and down. Price, $0.00.

Fig. 326.

Rotating Bell Glass. — (Fig. 326.) — To a mahogany base is
supported two uprights, one of metal and the other of glass,
each having a brass cap and socket, with sliding rod, the
outer ends of the rods being formed into hooks. Between
the inner ends of these rods there is supported on a point,
and metal centre, a bell glass, having pieces of tin foil pasted
on its sides. A chain, connecting the insulated rod with the
prime conductor of an electrical machine, will cause the rod,
and glass covered by one of the strips nearest to the rod, to
be electrified, and consequently to be repelled ; thus bring-
ing another portion near the rod, which in like manner is
charged, and repelled ; and tlius each portion will be charged
in succession ; each of which, in revolving near the rod con-
nected with the ground, will be discharged, and thus a con-
tinued rotary motion produced. Price, $4.00.

Electrical Vane. — (Fig. 327.)— This is a light wheel of
paper or pasteboard, suspended on a stand by a delicate
point, having a support to sustain it in a horizontal plane ;
on the edge of the wheel are a number of floats, which
when placed before the end of a point attached to the
prime conductor, will be put into rapid rotary motion.

The wheel may be suspended vertically, instead of hori-
zontally, and a system of wheelwork put in motion by the
same means. Price, $2.00.

ELECTRICAL APPARATUS.

289

Fig. 327.

Fig. 323.

Electrical Windmill. — (Fig. 328, as above.) — This con-
sists of a house made of wood, having up its centre a wire,
the lower end fitting a hole in the conductor of an electrical
machine, the upper end supporting a pivot, put crossways,
so that its end projects through the mill, bearing the sails,
which are of paper or pasteboard, a fine wire running
along the back and end of each, having a point projecting
beyond the outer edge ; upon turning the machine the mill
will revolve rapidly. Price, $5.00.

Fig. 329. Fig. 330.

Electrical Cross. — (Fig. 329.) — This is a cross formed of
two thin leaves of talc, on which are fastened spangles of
tin-foil nearly touching each other and having a wire point
at each end ; the cross supported delicately on a suitable
support. Price, $2.50.

25

290

BENJ. PIKES, JR., DESCRIPTIVE CATALOGUE.

Spiral and Flyer. — (Fig. 330, preceding page.) — This
consists of a glass tube coated as a spiral, and having a cup
with a pointed wire projecting, in which is placed a flyer.

Price, $3.00.

Fig. 331.

Fig. 3 .2.

Revolving Glass G7ofo.— (Fig. 331.)
— This apparatus consists of a glass
globe delicately suspended on a point,
and having a mahogany base ; on one
side and opposite the centre of the
globe, there is a brass ball mounted
on a glass pillar, having a hook for at-
taching a chain ; on the other side
there is a brass ball with metallic support,
having a point projecting towards the centre
of the globe. To use, connect the insulated
ball with the conductor of the electrical ma-
chine by a chain, and the other ball with the
floor, or ground ; give the glass globe a rotary
motion with the hand ; the globe, on passing
the insulated ball, will on that side be charg-
ed, and repelled ; but on coming near the
point on the opposite side, will be attracted,
and the fluid drawn off, thus keeping up a
continued rotary motion. Price, $2.50.

The Aurora Tube.— (Fig. 332.)— This inte-
resting and beautiful experiment is shown by
a glass tube of from twenty to forty inches in
length, and from one and a half to two and a
half inches in diameter, having brass caps
cemented on each end ; the lower end having
a stop-cock and a brass ball within the tube,
the upper end a pointed wire within the tube
and a brass ball on the outer end ; the whole
is mounted on a base for a support. To use,
the tube is exhausted of air by attaching the
stop-cock to an air pump ; present the ball
to the prime conductor of an electric machine,
when the fluid will pass in a continued and
beautiful stream, the appearance presented
being exactly that offered by the aurora bore-

ELECTRICAL APPARATUS.

291

alls in high latitudes. To insure success, the tube should be
thoroughly dried previous to use, to free it from all damp-
ness.

This apparatus is also commonly used for showing the
guinea and feather experiment in pneumatics, having a piece
of metal and feather within the tube.

Price, three sizes, $4.50 ; $6.00; $10.00.

Aurora Flask.— (Fig. 333.)— This consists of a Fig. 333.
glass flask, holding about a quart, coateil with tin
foil at the end of the globular part, covering about
one-third of the sphere to the neck. There is ce-
mented a brass cap, with screw, for attaching to
the air-pump, and having a valve on the end of the
screw to prevent the return of the air, over which
a nut is screwed to prevent any leakage. To imi-
tate the aurora borealis — make the flask very hot
before the fire, hold it by the tin foil, and hold its
ball to a charged prime conductor. Very long and
brilliant flashes will pass along the partly exhaust-
ed flask. The flashes will continue long after the removal
of the tube from the machine. Price, $2.50.

Fig. 334.

The Luminous Discharger.
— (Fig. 334.) — This consists of
a bent glass tube, having a
brass ball at each end, con-
nected by an iron chain which
passes through the tube, and
having a wooden handle.

Discharge any Leyden jar
with this discharging rod, and
it will appear beautifully lu-
minous. Price, $2.00.

Spiral Tube.—(F\g. 335, next page.)— This consists of
two glass tubes, placed one within the other. On the
outside of the inner tube are fastened spangles of tin-foil ;
the two ends of the tubes are wrapped round with tin-foil,
and cemented each into a brass cap. To use the spiral
tube, hold one end in the hand and the other apply to the
conductor, when a spark will pass along the whole length.

Price, $2.00 and $2.50.

292

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

Set of Spirals.— (Fig. 336.)
— This is an instrument of ex-
treme beauty. It consists of
five spirals, enclosed in glass
tubes, about 14 inches long,
connected by brass sockets
to a handsome polished maho-
gany stand ; on the top of
each spiral is a cap terminat-
ing in a brass ball ; in the
centre of the stand is a swell-
ed glass pillar with a cap, and
terminating in a pointed wire,
on which is mounted to turn
easily, a wire terminated by
balls, so that as it revolves it
shall come very near to each
of the spiral tubes in succes-
sion ; to the cap of the swelled
pillar there is a hook, to attach
a wire to the prime conductor ;

if the movable flyer be started it will continue to re-
volve, communicating a spark to each of the spirals,
and they will be rapidly illuminated.

Price, $10.00.

Luminous Word. — (Fig. 337, next page.) — The luminous
word is formed by pasting strips of tin foil on a plate of
glass, having portions cut out as represented in the cut.
The side of the glass coated is protected from injury by
another glass plate, and both fixed in a frame, having a
handle, or mounted on a stand. A brass knob and wire
connect with the first piece of foil, and a hook and chain
with the last. On presenting the knob to the conductor,
the chain being connected with the ground, lines of fire re-
presenting the word, occasioned by sparks passing at the
same moment through all the spaces, will be seen.

Price, $3.00.

Luminous Crescent. — (Fig. 338, next page.) — This is the
same instrument in principle, and formed in the same man-
ner, having a frame about fourteen inches square representing
luminous lines in the form of a crescent. Price, $3.00.

ELECTRICAL APPARATUS.
Fig. 337. Fi£. 333.

293

Fig. 340.

Spotted Jar.— (Fig. 339.)— This is fitted
up like the Ley den phial, only the tin-foil
coating is gummed on in little square pieces
at some distance from each other ; so that
when the bottle is charged in the dark, the
sparks will be seen flying across the spaces,
from one square to another. If it be dis-
charged gently, by bringing a pointed wire
gradually to the knob of the jar, the fluid
will pleasingly illuminate the uncoated parts,
and make a crackling noise in passing the
spaces. Price, pint, $2.25.

" quart, $3.00.

The Egg Stand.— (Fig. 340.)— This con-
sists of a wooden frame, with a piece of metal
let into the bottom ; a chain attached to this
is connected with the outside of a Leyden
jar. There are three wooden slides to hold
as many eggs. A wire and ball pass through
the upper part of the frame, so as to touch
the top egg, and the eggs are to touch each
other. A shock is passed through the eggs
by touching the upper ball with a discharg-
ing rod, which reaches to the inside of the
charged jar, whose outside is united to the
chain at bottom. The eggs will become
beautifully luminous, and the shock in pass-
ing will make a sound as if the egg shells were broken, as
indeed they will be if the shock be large. A quart jar is
quite sufficient for this experiment. The eggs, if eaten im-
Zo

294

BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

mediately, will have a strong taste of phosphorus ; and will
very soon afterwards become putrid, that is to say, in two
or three days. When broken, the white and yelk will be
found completely intermingled with each other, if several
shocks have been passed through the eggs.

Price, 81.50.

Fig. 341.

Fig. 312.

Electrical Fire House. — (Fig. 341.) — This is a neatly-made
tin house, having in the front five windows and a door, which
are handsomely painted, and the front crossed off to repre-
sent brick or stone. On the one side of the house, attached
to the chimney, there is a glass tube, terminated by a brass
ball, A, within which is a wire, proceeding down the tube
into the house, where it is terminated by a second ball, B.
Through the opposite side of the house is a second glass
tube, wire, and two balls, marked at C and D. The wire of
this part is capable of sliding backwards and forwards, that
the balls withinside may be made to approach each other
more or less according to the strength of shock to be passed
through them. The balls C and D are loosely covered with
tow, and dipped in or sprinkled with powdered yellow
rosin. When the shock is passed from A to D, the rosin
will be inflamed, and the fire appear through the windows.

Price, $3.50.

The Belted Bottle. — (Fig. 342.)— This is a glass jar coated
as represented in the figure, having an arm attached to the
bottom supporting a rod of glass, to which a sliding piece
is attached, to connect the belt with the lower part. This

ELECTRICAL APPARATUS. 295

instrument shows the passage of the fluid during the charg-
ing of the bottle. The coating both inside and outside is
put on as represented. The belt on the outside is only
put in contact with the lower part of the coating by means
of the sliding piece on the outside. The wire within is at-
tached to the inside of the bottom. In charging, the lower
part becomes charged first, and the fluid will be seen to pass
upwards inside in flashes, wrhile if the connecting piece be
withdrawn, the fluid will be seen to pass downwards on the
outside from the belt to the lower part. Price, $3.00.

The Electrical Cannon. — Fig. 343.

(Fig. 343.) — This is a brass
cannon, about five inches long
and one inch in diameter,
mounted on a wooden stock ;
the ball at the top has a
wire attached to it, which passes down a short tube of ivory
into the chamber of the cannon, to within an eighth of an
inch of the opposite side, and through this space the spark
passes to explode the gas, which may be formed by putting
a handful of iron nails, or the same quantity of pieces of
zinc, into a wine bottle ; to these add half a pint of water and
a wine glass full of sulphuric acid. Have ready prepared
for the bottle a cork which fits it, and through which the stem
of a tobacco pipe passes. The mixture will soon throw up
bubbles of gas ; when it is supposed that these have dis-
placed the air of the phial, cork it up, so as to suffer the
gas to pass out only through the stem of the pipe. Here it
may be collected in a collapsed bladder fastened to the
other end of the stem, or, if preferred, the bladder may be
tied to the top of the cork itself. The gas will soon fill the
bladder. When enough for use has been collected, the stem
may be broken, so as to separate the bladder and the bottle ;
then holding the cannon with the mouth down, press the
gas into the cannon, which, by its levity, will partially dis-
place the atmospheric air, mixing therewith, and producing
an explosion when the spark is passed through. The mouth
of the cannon must be well corked to prevent the escape of
the gas previous to firing. Price, $2.00.

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

Fig. 344.

Electrical Mortars. —
(Fig. 344.) — These are
formed as the preceding,
only in the shape of a
mortar.

Price, $3.00.

Fig. 345

Electrical Pistol— (Fig. 345.)—
The simplest and best form of the
hydrogen pistol is seen in the cut.
It consists of a tube of brass,
about an inch in diameter, and eight inches long, fastened
on to a baked wooden handle, shaped like that of a common
pistol. Where the trigger is ordinarily placed, is a short
ivory tube, which fastens into the brass tube, so as to reach
about half way across it. This piece of ivory is pierced so
that a wire may pass through it. The inner part of the
wire is at a small distance from the inner part of the top of
the tube, and the outer end of it is terminated by a small
ball. If then a spark be taken by the barrel, and at the
same time that the linger touches the ball of the trigger, a
spark will pass from the tube to the point of the wire inside,
and thence to the trigger to the hand.

Price, $2.00 and $3.00.

Fi&- 316- Apparatus for Firing Gun-

powder by the Electrical Spark
— (Fig. 346) — consists of a ma-
hogany base, about six inches
long and four wide, supporting
two insulating glass pillars ; to
the one is attached a bent wire,
terminating in a small brass
ball, and the other a wooden
cup for the powder, each hav-
ing a crook for attaching a
chain. The powder is placed in the wooden cup, A, either
dry or made up into a pyramidal form with a little water.
The brass ball, b, is brought immediately over it; the chains,
c d, being connected with the outer and inner surfaces of a
Ley den jar. The discharge takes place, and the powder is
inflamed. Price, $3.50.

ELECTRICAL APPARATUS.

297

Apparatus to Fire *'& 3ir-

Spirits of Wine, or
£ther.— '(Fig. 347.)
— This consists of a
rod, having a knob
at each end, support-
ed horizontally on
an insulated stand.
Through one of the
balls slides a wire,
vertically,with a knob
at one end, beneath
which is placed a me-
tallic cup for the spi-
rits.— To use, place it
so that the ball, a, can receive sparks from the prime con-
ductor. Pour spirits of wine into the cup, e, till the bottom
is just covered. Place the cup under the wire, d, then turn
the machine, and the sparks that are received by a will fly
from the wire through the cup, and inflame the spirits.
Warming the spirits will cause it to take fire more readily.

Price, $2.25.

Stand for the Fusion of Wire by F]s- 313.

the Electric Spark.— (Fig. 348.)—
The fusion of wire is sometimes
employed as the test of electrical
power, in which case it should be
taken that the length of the circuit
is always the same, and that the
degrees of ignition are uniform ;
for a wire may be melted with but
slight variations of appearance,
when very different quantities of
electricity have been transmitted
through it. The lowest degree of
perfect ignition ought therefore to be obtained in all compa"
rative experiments, and its phenomena should be uniform »
that is, as soon as the discharge is made, the wire should
become red hot in its whole length, and then fall into drops.
In order to ensure a perfect uniformity in this respect
throughout a series of experiments, Professor Hare has in-
vented the apparatus shown in the cut. This consists of

298 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

two bent arms, which diverge from a centre, as a pair of
compasses, and when adjusted are held tight by a screw at
the centre. A reel of tine pendulum wire is fixed at one
end by a screw, and at the other by a small pair of nippers.
The whole is of baked wood, with glass supports.

Price, $3.00.

Fig. 349. Ignition of Charcoal Points in Chlorine.

— (Fig. 349.) — This consists of a glass
globe, or other vessel, having two necks,
each having brass caps, the lower one a
stop-cock for connecting with the air
pump, and the upper one a brass rod
sliding in a stuffing box, on the interior
end of which is a pair of forceps for hold-
ing a charcoal point, another similar point
being fixed to the stop-cock below. To
use, fill the vessel with chlorine gas, and
adjust the wires, so that their points shall
nearly touch each other. When the
electric current is made to pass through
the wires, the charcoal points will be ig-
nited, becoming of a red heat, yet the chlorine will not be
affected, however long the action may be pursued.

Price, $6.00.

Fig. 350. The Sphere and Point.— (Fig. 350.)— Faraday's
| hollow brass sphere and tubular handle, with
pointed sliding wire within, for the purpose of
showing the influence of surfaces in electrical dis-
charges. When the sphere is employed a bright
spark is observable at each discharge, provided the
point of the sliding wire be within the sphere, but
if it projects without, the discharge changes its form
to that of a brush. Price, $1.50.

Biot's Movable Hemispheres and Ball. — (Fig.
351, next page.) — For showing that electricity re-
sides on the surface only. When a substance be-
comes charged with electricity, it is extremely
probable that the fluid is confined to its surface,
or, at any rate, that it does not penetrate into the
mass to any extent. A ball formed of any material will be

ELECTRICAL APPARATUS. 299

equally electrified whether it be solid or hollow, and if it be
hollow, the charge which it receives from any source of
electricity will be the same whether the shell of matter of
which it is formed be thick or thin.

Fig 352.
Fig. 351.

To demonstrate practically the distribution of electricity
on the surface of a conductor, the following apparatus was
contrived by Biot. A sphere of conducting matter, a, is
insulated by a silk thread, and two thin hollow covers, b b,
of brass or copper, are provided with glass handles, c c, and
correspond with the shape and magnitude of the conductor.
The sphere, a, is electrified, and the covers are then applied,
being held by the glass handles. After withdrawing them
from a, they are found to be charged with the same kind of
electricity as was communicated to a, which will be found to
have lost the whole of its charge, proving that it resided on
the surface only.

But although electricity may be considered as confined to
the surfaces of bodies, its intensity is not on every part the
same. On a sphere, of course the symmetry of the figure
renders the uniform distribution of electricity upon it inevi-
table ; but if it be an oblong spheroid, the intensity becomes
very great at the poles, but feeble at the equator.

Price, - $4.00.

„ mounted on an insulated stand, $5.00.

Faraday's Bent Electrical Conductor. — (See Fig. 352, as
above.) — Faraday's bent brass electrical conductor, with two
different sized balls at the extremities, for illustrating that
between conducting surfaces, the spark, in disruptive dis-
charges, is modified by the differences of the dimensions of
the discharging or receiving surfaces. Price, 81.75.

300

BKNJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

Fig. 353. Apparatus to show that extending the

Surface diminishes the Quantity of
Electricity. — This instrument (Fig. 353)
consists of a series of metallic plates,
increasing in size from the top, and sus-
pended from each other by metallic
threads, the upper one having a handle
of glass, or a silk cord being attached to
the upper plate. Let the plates rest on
each other, and placing the whole toge-
ther upon the top of a gold-leaf elec-
troscope, electrify them so that the gold
leaves diverge ; then gradually draw
them up by the silk thread at tli3 top,
when the diverging will diminish in
proportion, and again increase when let down as at first.

Price, $2.00.

- 354-

been

Insulated Conductor for showing
d Electricity In/ Induction. — (Fig,
354.) — This is formed of a cylinder
of brass or tin, with well rounded
ends, and supported on a glass
stand, and furnished with a pith
ball electroscope, and let e be an
excited glass tube. On approach-
ing this tube within about six inches
distant from d, the pith balls will
instantly separate, indicating the
presence of free electricity. Now,
in this case the electric, e, has not
sufficiently near to the conducting body to

brought

communicate to it a portion of electricity, and the moment
that it is removed to a considerable distance the balls fall
together, and appear unelectrified ; on approaching e to d
the balls again diverge, and so on. The fact is, this is a
case of what is termed induction, the positive electricity of
e decomposes the neutral and latent combination in d a c,
attracting the negative towards d, and repelling the positive
towards e, and the balls consequently diverge, being posi-
tively electrified. On removing e the force which separated
the two electricities in c? a c is removed, the separated ele-
ments re-unite, neutrality is restored, and the pith balls fall

ELECTRICAL APPARATUS. 301

together. The electricity of e induces a change in the elec-
tric state of d c. Price, japanned tin, $2.00.

" brass, $2.50 to $3.50.

Set of three Conduct- Fie-

ors for Experiments on
Induction. — (Fig. 355.)
— This arrangement con-
sists of three conductors
mounted on glass pillars,
with mahogany stands ;
the conductors are form-
ed of brass, or japanned tin, with well rounded ends. These
instruments, when excited either by the proximity of a charg-
ed conductor, or by an excited glass rod held towards them,
beyond the conductor, N, draw away the central conductor,
and also the excited rod ; the central conductor, o, Vvill not
be charged at all, that marked P will be positive, and that
at N negative.

When charged as before, as soon as o is removed, place
the conductor, N, so as to touch p. The disturbance of
both will be neutralized by each other, showing that the
quantity which is plus in one, exactly counterbalances that
which is deficient in the other.

Price, $3.00 ; $5.00 ; and $8.00.

The Double Jar.— (Fig. 356.)— To the knob Fis- 336.
of a large Leyden jar a metallic stage, c, is
adapted on which is placed a smaller Leyden
jar. This instrument is used for various ex-
periments, and shows how necessary it is to
connect the outside and inside of the same jar
together, before it will be discharged. Place
the double bottle on a table not insulated, and
charge the upper bottle, A, positively, by con -
necting its ball with the conductor. The out-
side of A, therefore, and also the inside of B
will be negative, and the outside of B positive.
Now connect by the discharging rod the outer
coating of B with the inner coating of A, and
no shock will pass between them. Again,
connect the outside of B with the inside of B,

302

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

and a shock will pass. Now connect the inside of A with
the inside of B, and a second shock will be obtained. A
series of bottles may thus be arranged, and a series of
shocks obtained by one charge only. Price, $3.00.

Insulated Stand. — (Fig. 357.)
— This is a metallic plate having
a brass knob, and insulated by a
glass pillar cemented into a ma-
hogany base, and useful in many
experiments. Place the jar, A,
on the insulating stand, B, and
attempt to charge it from the
prime conductor, you will find
it impossible : now apply the
knuckle to the outside coating,
and continue to turn the ma-
chine : for every spark that
enters the jar, one will pass be-
tween the outside coating and
the knuckle, and on applying the
discharging rod, the jar will be
found to have received a charge.
Instead of the knuckle, the knob
of a second uninsulated jar, c, may be applied, and both
jars will receive a charge. Price, $2.00.

Fig 358.

Series of Insulated Jars. — (Fig. 358, as above.) — This
cut represents three or four Leyden jars, each mounted on
a base, insulated by a glass pillar, and supported in a hori-
zontal manner, by a band encircling the jar, one of them
having a hook for the purpose of attaching a chain.

No charge of any amount can be given to a Leyden jar,
if it be insulated ; for, in proportion as the positive electri-

ELECTRICAL APPARATUS.

303

city is communicated to its interior coating, it is necessary
that the same quantity should be removed from the exterior,
which would otherwise counteract the negative electricity
by which the charge is sustained. To effect this, a com-
munication is established with the earth, or with the interior
coating of a second jar, the outside coating of which again
may communicate with the interior of a third, and thus a
series of insulated jars may be charged from each other, as
shown in the figure, taking care to withdraw the opposing
electricity from the last. Price, each, $2.25.

Leyden Jar with Discharging Fi£- 359-

Electrometer. — Fig. 359 repre- ,»
sents the arrangement for pro-
ducing a series of discharges
from a Leyden jar, for any par-
ticular purpose, without the in-
terference of the operator, and
also the mode of use ; a, repre-
sents the prime conductor of an
electrical machine ; 6, a Leyden
jar ; on the wire communicating
with the interior is fixed an arm
of glass, c, on the end of which
is cemented the brass knob D,
through this knob a wire, f d,
slides, so that the ball d may be brought to any required
distance from the knob of the jar, e. A careful inspection
of the figure will show how this discharging electrometer
acts, and how, by increasing or lessening the distance be-
tween d and e, the strength of the charge may be regulated.

Price, $2.50 and $3.00.

Eudiometer. — (Fig. 360.) — This instrument is Fis- 360.
used for exploding gases, which being inflamed
by the electric spark has given rise to various
instruments called eudiometers, one of the most
simple of which is shown in the margin. It
consists of a thick glass tube closed at the upper
end, and open below, where it dips into a cup or
basin of mercury. It is graduated along the
side, and has two wires through the upper part
which approach each other. The tube may be

304 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

supported in any convenient manner. The tube is filled
with mercury or water (according to the kind of gas
to be operated upon) ; it is then reversed, and the gas to
be operated upon suffered to ascend the tube, until a cer-
tain quantity has been introduced. The electric spark or
shock is then passed from the one wire to the other, when
the gas is inflamed. The result is seen by the product left.
Price, $3.00 ; graduated, $4.00; stand, $1.00.

Fis- 361. Apparatus for passing an

Electrical Spark through
Gases.-Psiss a spark through
a vessel filled with nitrogen,
and it becomes intensely
brilliant, and of a splendid
blue color, equal to that of
burning brimstone. The ap-
paratus, which is convenient,
for trying experiments of this kind, is as follows (Fig. 361).
A is a glass receiver, holding about a pint ; it has a wire and
ball inserted in two opposite sides, B and C. B is capable
of sliding backwards or forwards, so that it may be made to
approach or recede from the other. The receiver is placed
in the pneumatic trough, and is filled with the required gas,
in the ordinary way practised by chemists. For some gases
a mercury or oil trough must be employed. During the
experiment one of the balls must be connected by a wire
with the prime conductor, as at D, and the wire of the other
held in the hand.

An instrument is made, answering the same purpose, con-
sisting of a globe of glass having two necks, one of them
attached to a cap connected with a stop-cock, and having a
brass ball entering the neck of the globe. The other neck
a cap with sliding rod, having brass balls at each end. The
globe is exhausted of air by the air-pump, and the gas to
be experimented with introduced.

Price, $3.00 to $6.00.

Kinnersley^s Electrical Air Thermometer. — (Fig. 362.) —
This is an instrument for showing the expansion of air when
an electrical shock is passed through the instrument. It
consists of a glass tube, ten inches long and two inches in

ELECTRICAL APPARATUS.

305

diameter, closed air-tight at both its ends by Fl's- 362-
two brass caps ; a small glass tube, open at
both ends, the lower one bent at a right angle,
passes through the bottom cap, and enters the
water contained in the lower portion of the
large tube. Through the middle of each of the
brass caps a wire is introduced, terminating in
a brass knob within the tube, and capable of
sliding through the caps, so as to be placed at
any distance from each other. If the two knobs
be brought into contact, and a Leyden jar
discharged through the wires, the air within
the tube undergoes no change in volume ; but
if the knobs are placed at some distance from
each other when the jar is discharged, a spark
passes from one knob to the other ; the consequence is a
sudden rarefaction of the air in the tube, shown by the wa-
ter instantaneously rising to the top of the small tube, and
then suddenly subsiding ; after which it gradully sinks to
the bottom of the tube, the air slowly recovering its original
volume. Price, $3.00.

Cavallo's Rain Mec- Fig. 363.

troscope (Fig. 363), repre-
sented in the cut. A is a
strong glass tube, about
two feet and a half long,
having a tin funnel cemented to its extremity, which funnel
defends part of the tube from the rain. The outside surface
of the tube is wholly covered with sealing wax ; c is a piece
of cane, round which brass wires are twisted in different
directions, so as to catch the rain easily, and at the same
time to make no resistance to the wind. The cane is fixed
into the tube, and a piece of wire proceeding from it, goes
through the tube, and is terminated by a ring, upon which
a pair of pith balls are suspended. This instrument is sus-
pended by the side of a window frame, with the funnel pro-
jecting outwards, while the pith balls are preserved dry
within. Price, $2.50.

Cavallos Bottle Electroscope (Fig. 364, next page) is
formed by two silver wires, each carrying at one of its

306

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

Fig. 3G4. enc[ri n httle j^ij mac[e Of pith ; the other ends
of the wires being suspended from a cork, which
is rather long and tapering at both ends, so as to
fit either way into the mouth of a varnished glass
tube, serving both as a handle to the instrument
when in use, and as a case for it when carried in
the pocket. When it is to be employed as an
electroscope, the cork is so placed that the wires
hang out of the tube, and will indicate by their
divergence any electricity that may be communi-
cated to them. When not in use, reversing the
cork closes up the instrument, and renders it more
portable. Price, $0.50.

Fig. 33.5. Coulomb's Tortion Balance.— (Fig. 365.)

a . — This delicate contrivance consists of a

thread of silk, a b, from which a needle of
shellac, c, is suspended ; it is attached to
the screw, d, by which it can be twisted
round its axis ; the needle carries a ball of
pith gilt, which is balanced by a counter-
poise on the other ; e is a metallic wire
passing through the glass shade, and ter-
minated by a metallic ball at each end ; the
ball of the needle and the interior brass
ball of the wire are brought into contact
by turning the screw, d, and the index
then points to the o on the scale, which is
marked on the circumference of the glass.
When the ball, e, is electrified, it acts on the
ball within that is attached to the needle,
repelling it to a certain distance, which
distance, and consequently the degree of
electrization, is indicated by the graduated scale.

Price, $12.00.

The Dry Pile, or Electrical Chime. — (Fig. 366, next
page.) — This instrument consists of a number of alternations
of two metals, with paper interposed ; the elements may
be circular discs of thin paper, covered on one side with
or silver leaf, about an inch in diameter, and similar

ELECTRICAL APPARATUS.

307

sized pieces of thin tin-foil, so arranged
that the order of succession shall be
preserved throughout, viz. zinc, silver,
paper, zinc, silver, paper, etc. ; about
one thousand pairs of such discs, in-
closed in perfectly dry glass tubes, ter-
minated at each end with brass caps
and screws, to press the plates tight
together, will produce an active arrange-
ment ; the positive end of one column is
placed lowest, and the negative end of
the other, their upper extremities being
connected by a wire, that they may be
considered as one column. A small bell
is situated between each extremity of
the column and its insulating support ; a brass ball is sus-
pended by a thin thread of raw silk, so as to hang midway
between the bells, and at a very small distance from each
of them. For this purpose the bells are connected, during
the adjustment of the pendulum, by a wire, that their at-
traction may not interfere with it ; and when this wire is
removed, the motion of the pendulum commences. The
whole apparatus is placed upon a circular mahogany base,
in which a groove is turned to receive the lower edge of a
glass shade, with which the whole is covered.

Price, $20.00.

Thunder House. — (Fig. 367.) — This in-
genious article is made of an upright piece
of baked mahogany, formed like the gable
of a house, as B B, and placed upon a
wooden stand. A wire marked c, runs
downwards throughout its whole length.
It is terminated above by a ball, A, which
being unscrewed shows a point beneath it.
In one or two parts of the gable are square
pieces of wood cut out. These are a quar-
ter of an inch thick, and one inch square
on the side. They are shown at D and F ;
are made so as to fit loosely into a hole
cut partly into the gable to receive them, and have a wire
running across each, so placed, that putting in the pieces in
one way, the wires shall with c E form a continuous and

308 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

uninterrupted line ; and when put crosswise, there shall be
a want of contiguity at that place, as shown at D.

Pass a shock from A to E, while the ball remains on and
the wire is continuous, and it will make a loud report with-
out disturbing either piece of wood.

Pass a shock, or rather endeavor to do so, with the upper
ball taken off, so that the point is displayed. The fluid will
pass and discharge the jar, but not in the manner of the
shock, and no report will be heard.

Now place either of the pieces of wood crosswise, and
restore the ball to the top. The shock will pass and throw
out the piece of wood that was placed crosswise, but not
disturb the other piece.

Let the piece of wood be placed crosswise, as in the last
experiment, but remove the ball. Upon discharging the
Leyden jar, a real shock will pass, and the wood will be
displaced, although a point terminates the apparatus.

Price, $1.75 and $2.50.

Fig.358. Electrical Pyramid.— (Fig. 368.)— This is

an apparatus of the same nature as the last,
and is to be used in the same manner. A is a
four-sided pyramidal piece of wood, or more
usually consists of four pieces fitting on to
each other. A line runs down the whole in
front, and is, moreover, continued down the
base, B ; continuity being occasioned by a
small square, as in the thunder house. This
is marked D in the cut, and is seen with its
wire placed sideways. Upon this movable
square, and upon the back of the base, the
upper portion is supported by three balls.
When a shock is sent from E to F, the square
D is thrown out, and the upper part of the
pyramid falls. Price, $2.00 and $3.00.

Lightning Conductors. — The identity of the electric fluid
with lightning was one of the first established facts rela-
tive to atmospheric electricity, and as it was the first in
time, so it is also in importance to us, teaching not merely
the origin and properties of that mighty power of nature,
but also how to escape from its direful effects. The very
appearance of lightning would induce us to attribute it to

ELECTRICAL APPARATUS. 309

electricity, nor is this supposition in any way weakened by
our experimental researches. If we compare the properties
of electricity with those of lightning, we shall find them
closely analogous, or rather identical. To Franklin, whose
active mind was constantly directed to practical application
of the facts disclosed by science, we are indebted for the
suggestion of a method of partially defending buildings from
the dreaded effects of lightning. His method was, to erect
by the side of the building to be protected, a continuous
metallic rod, in perfect communication with the earth ; and
experience has fully demonstrated the value of this pre-
caution.

The conductor should penetrate the ground sufficiently
deep to be in close contact with a stratum of moist soil, and
be carried above the highest point of the building. Great
care should be taken that every part of the rod be perfectly
continuous, and that its substance be sufficient to prevent
any chance of its being melted ; perfect security on this
head is arrived at by having a rod three quarters of an inch
thick. It has been proved, that conductors erected with
these precautions will protect a circular space of a radius
double the height above the highest point of the building to
which they are attached.

The little arrangement Fig. 359

(Fig. 369) amusingly illus-
trates the use of a continu-
ous conductor. A board,
about three quarters of an
inch thick, and shaped like
the gable end of a house, is
fixed perpendicularly upon
another board, upon which
a glass pillar also is fixed in
a hole about eight inches dis-
tant from the gable-shaped
board. A small hole, about
a quarter of an inch deep,
and nearly an inch wide, is
cut in the gable-shaped board, and this is filled with a square
piece of wood of nearly the same dimensions. It should be
nearly of the same dimensions, because it must go so easily
into the hole, that it may drop off by the least shaking of
the instrument. A brass wire is fastened diagonally to this

310 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

square piece of wood, and another of the same dimensions,
terminated by a brass ball, is fastened on the gable-shaped
board, both above and below the hole. From the upper
extremity of the glass pillar a crooked wire proceeds, termi-
nated also by a brass ball, and sufficiently long to reach
immediately over the ball or the wire of the board. The
glass pillar is loosely fixed in the bottom board, so that it
may move easily round the axis. It is evident that, with
this arrangement, a shock from a Leyden jar may easily be
sent over the square hole by connecting the exterior coating
with the wire in the gable-shaped board below it, and the
interior with the wire on the glass pillar which comes within
the striking distance of the wire in the gable-shaped board
below it.

Suppose now the square piece of wood to be placed in the
hole in such a manner that the wire attached to it diagonally
shall be in contact with the wires above and below it, a shock
may evidently be transmitted without any disturbance taking
place ; but if it be put into the hole in an opposite direction,
so that the shock from the jar shall be obliged to pass over
it altogether in the form of a spark in its passage from wire
to wire, the concussion it will occasion will throw the square
piece of wood to a considerable distance from the apparatus.
The square piece of wood may here be supposed to repre-
sent a window, and the wire a continuous or broken con-
ductor passing by the side of it, and the violent effects pro-
duced by the minute quantity of electricity accumulated in
a Leyden jar may be considered as an humble imitation of the
effects of a stroke of lightning. When the passage is unin-
terrupted, the electricity passes quietly down, but when im-
peded it produces the most violent effects.

Price, $4.00.

Platina Point for a Lightning Conductor. — The light-
ning conductor is an apparatus to preserve ships and build-
ings from the effects of lightning. It consists of a pointed
rod of iron or copper, half or three-quarters of an inch in
diameter, pointed at top, and projecting two, three, or more
feet above the chimney, or other highest part of the build-
ing, the lower end being inserted four or five feet in the
ground. Its action is as follows: — Should lightning ap-
proach the building, it would most likely be drawn away
silently by the pointed wire ; or, if it should strike the

ELECTRICAL APPARATUS.

311

building, the conductor would convey it to the earth Fis- 37°-
without its doing- any injury.

The most usual way that lightning rods terminate
is by merely pointing the rods, sometimes gilding
them ; the action of the weather on these in a short
time destroys the point, and the utility of the rod is
in part, or wholly destroyed. To remedy this defect,
a copper cone about six inches long, terminated in a
platina point (Fig. 370), about one inch in length, is
fastened to the top of the rod ; this metal will undergo
no change by the action of air and water, and will not
even tarnish, however long exposed to the action of
the weather, and is always used where rods are put
up in the best manner.

Price, each, $4.00 ; small, $3.00.

Powder House. — An
electrical apparatus, to
show, in an amusing man-
ner, the firing of gunpow-
der by electricity, and
thereby proving the effect
of lightning upon buildings
in setting them on fire.

Fig. 371 represents a
perspective view, the side
next the eye being omitted
that the inside may be
more conveniently seen.

The front is fitted up like the thunder house and used in
the same manner. The house itself is made of seven pieces
of mahogany, joined together by hinges, so as to be capable
of falling flat on the table ; a small projecting ridge along
the top of the roof holding it up until the powder is fired.
A is a ball of brass with wire reaching partly down the
house, and across it, inside to the brass top of the table c.
This has the gunpowder placed upon it. Immediately
above the powder is a second ball, which leads by a wire to
the outside of the house at the opposite end, passing
through the wood at the end of the house. Then follows
the wetted thread, E, and afterwards the chain, B. Passing
an electrical shock from A to B, the powder will be fired
and the house thrown down.

312 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

To insure success in this experiment, it is necessary to
pass the charge from the jar, through a few inches of water,
disconnecting the metallic wire or chain, dipping it in the
water, or pass it through a few inches of wet linen thread
connected with the wires or chain through which the dis-
charge passes. Price, $6.00.

Cylinder Electrical Machine, with detached Conductor. —
(Figure 372.) — A is a glass cylinder, having at each end of
it a cap of wood or brass, and supported by a stand, with
two uprights. The end of one cap is turned with a pivot,
which fits into a hole near the top of one of the uprights.
The other cap is turned with a similar pivot, and has beyond
this a flange and a square gudgeon upon which a handle
fits. This end of the cylinder is supported in a similar man-
ner to the other end, but instead of a hole merely being
bored in the upright leg, a portion is cut away, that the
cylinder may be the more easily taken out, and put up again
in its place ; it may be secured, when there, by a pin run
through the upright just above the axis of the cap. Be-
hind the cylinder is a cushion, which extends in length to
within an inch of either end of the cylinder ; it is from one
to two inches in width, according to the size of the cylinder.
On the lower part of the cushion is glued a flap of leather,
the rough side outwards ; and on the edge of the leather
the silk flap which passes over the cylinder when in action.
The cushion is supported sometimes by a thick rod of glass
with a wooden spring at the top of it, as in the figure ; at
other times a springy piece of wood alone is used. It is
fastened at the top to the cushion by a hand-screw, which
passes through the support, and is fixed by a thread in the
back of the cushion itself. The lower end of the support for
the cushion is made so as to slide backwards and forwards,
either on the top, or, still better, underneath the stand, and
is held in its position by a thumb-screw.

B represents the prime conductor, formed either of wood
covered neatly with tin foil, or of metal. It has round and
smooth ends, at one of them a ball and wire for the suspend-
ing of various apparatus, at the other a projecting wire fur-
nished with a row of points to collect the fluid when disturbed
by the cylinder. It is necessarily supported upon a glass
pillar, sometimes attached at the lower end to the same
stand as the rest of the machine, in which case the conductor

ELECTRICAL APPARATUS.

313

runs parallel to the cylinder, and has the points in the side
instead of the end. At other times it is fixed to a separate
foot, as is to be seen in the figure below.

Fig. 372.

To Work the Machine. — Warm the whole well before the
fire, and cleanse it from all damp and dust. Take off the
cushion, scrape away all dirt, spread evenly upon it some
fresh amalgam, put it back in its proper place, and fasten
to the screw which connects it with its upright a brass
chain, the other end of which reaches to the table or floor,
or the walls of the apartment. Upon now turning the
handle, streams of fluid will be seen to issue from the cushion,
27

314 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

and passing under the silk, to fly off at its edges. To collect
the fluid, place the conductor with its points about a quarter
of an inch from the edge of the silk, which will so readily
attract the fluid from the cylinder, that sparks proportionate
to the extent of the glass surface rubbed may be taken from
it ; being very careful, however, that the glass stand of the
conductor be perfectly dry. The pressure of the cushion
against the cylinder is to be regulated by the screw on the
stand at bottom.

If the machine be small, it will require warming ; the
power of a machine is generally increased by rubbing the
cylinder for a minute or two with a slightly greased rag, or
by putting one hand upon the cushion.

The rationale of the action going on, is this : — The fluid
passes from the earth through means of the floor, Avails, &c.,
to the chain suspended from the cushion ; here friction, winch
is the cause of the disturbance, takes place. The disturbed
fluid passes to the glass cylinder, and is confined from escape
by the silk flap ; that ceasing, the fluid would fly to any-
thing around, particularly to a pointed body, or a lighted
candle ; but this is prevented by the superior attraction for
it from the nearer end of the prime conductor put to receive
it. Thus it will be at once seen that- an electrical machine
resembles a pump ; the earth may be likened to a well of
water ; the chain to the lower pipe of a pump ; the cushion
is the sucker ; the silk the nozzle ; and the prime conductor
is like a pail to hold the fluid. Price, 5-inch, $10.00.

" 6-irich, $12.00.
" 8-inch, $16.00.

ELECTRICAL APPARATUS. 315

MEDICAL ELECTRICITY.

IT is true, that like every other simple medicine which
has proved beneficial to mankind, electricity met with much
opposition from the interested views of some and the igno-
rance of others, lias been treated with contempt, and injured
by misplaced caution. We shall recommend to those who
thus oppose it, not to condemn a subject of which they are
ignorant, but to hear the cause before they pass sentence ;
to take some pains to understand the nature of electricity ;
to learn to make the electrical machine act well, and then
apply it for a few weeks to some of those disorders in which
it has been administered with the greatest success ; and
there is no doubt but they would soon be convinced, that it
deserves a distinguished rank in medicine, which is the off-
spring of philosophy.

The science of medicine and its practitioners have been
reproached with the instability and fluctuations of practice ;
and on this ground it has been predicted, that, however great
the benefits which may be derived from electricity, it would
still only last for the day, and then be consigned to oblivion
We must confess that we cannot be of this opinion, noi
easily led to think a set of men, whose judgment has been
matured by learning and experience, will ever neglect an
agent which probably forms a most important part of our
constitution. Electricity is an active principle, which is
neither generated nor destroyed ; which is everywhere, and
always present, though latent and unobserved; and is in
motion night and day to -maintain an equilibrium that 19
constantly varying.

As the science of medicine knows of no specific, so we
are not to suppose that electricity will triumph over everj
disorder to which it is applied. Its success will be more o;
less extensive, according to the disposition of the subject,
and the talents of those who direct it ; it cannot, therefore,
appear surprising, that many disorders have been refractory
to its powers, and others have only yielded in a small

316 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

degree, or that the progress of the cure has often been
stopped by the impatience or prejudice of the diseased ;
but at the same time, it must be acknowledged, that even
in its infancy, when it had to combat against fear, prejudice,
and interest, its success was truly great ; we have surely
then the highest reason to expect a considerable increase of
success, now that it is cultivated and promoted by profes-
sional men of the first merit.

Electricity should always be administered gently at first,
and its power only increased when the gentle application
is found ineffectual, except in cases of paralysis, or when
used to remove obstructions, its full power may be at once
administered ; but even here the shock of a quart Leyden
jar will be sufficient ; the frequency of the "shocks," and not
the strength of them being most to be relied upon. Also,
we would remark, that no danger can arise from the admi-
nistration of electricity ; and let it not be thought that the
remedy is worse than the disease, as those who subject
themselves to the powerful shocks given by the electrical
apparatus of our various institutions are apt to believe. On
the contrary, it may be administered to sleeping children
without waking them ; and even when awake, its application
may be made a source of gratification rather than of appre-
hension. To administer electricity properly requires con-
siderable skill and tact in the operator, and as this is seldom
found so surely as among medical men, and as they neither
like the trouble of operating, nor are taught anything of the
curative effects of the fluid during their medical studies,
they who are best able to administer it with effect are re-
gardless of it altogether.

Electricity, according to the mode of its administration, is
either sedative, stimulant, or deobstruent ; hence the pro-
priety of its application to diseases of quite contrary cha-
racter. We have applied it to palsies, rheumatisms, inflam-
mations, contractions of the muscles, amaurosis, chilblains,
tumors, sprains, and other diseases and accidents. The
methods of electrifying are five ; first, simple electrization,
or merely subjecting the person to the action of electricity,
by placing him on a glass-legged stool, and connecting him
with the electrical machine when in use, as represented in
the cut. Second, drawing the fluid from the particular part
of his body which may be affected ; this is either done hold-
ing towards him a wooden point, when a cooling and refresh-

ELECTRICAL APPARATUS. S« /

ing breeze is perceptible, or by placing your hand upon his
clothing, when if any woollen or silk interpose between your
hand and his body he will feel a peculiar pricking sensation,
occasioned by innumerable sparks issuing from the part
beneath the hand, and which will soon occasion a great
degree of warmth in that part. Or a third method is to
draw the fluid from him by means of sparks, taken by the
knuckle, or else by a wire with a metallic ball at the end
of it. If the operator hold this tight he will not feel the
sparks himself. A stronger way of drawing off electricity
is by means of what are called vibrations, and a still stronger,
sparks. For these two last the patient either stands, or sits
on an ordinary chair, and not on the glass stool before
mentioned.

The following apparatus is all that is essentially necessary,
though many other articles have been described and recom-
mended. The first essential is a glass-legged stool (Fig.
373) ; if required for cheapness it may be a piece of board,
made smooth, and with round edges, supported upon four
wine bottles, pegs being driven into the under-side of the
board to fit the necks of the bottles ; solid glass are, however,
infinitely better. In using the stool, a large sheet of brown
paper or pasteboard, or, still better, a piece of oil-cloth,
larger than the stool itself, is to be placed beneath it on the
floor, to prevent the filaments of the carpet, or the dust of
the floor, from drawing away any of the fluid accumulated.

Fig. 373.

The next requisite is a flexible tube, or connector, as a
chain ; the stool should be connected to the machine by a
chain which is sewed up in silk, and afterwards varnished or
covered with India rabber ; thus there will be no loss of
fluid. But for numerous purposes the instrument called a
flexible tube is much better.
27*

318 BENJ. PIKE'S, JR. DESCRIPTIVE CATALOGUE.

A wooden or me-
tal point is sometimes
used ; by this a gen-
tle stream of electri-
city, called the elec-
trical aura, or breeze,
is given to or taken
from a patient, ac-
cording as the point
is held in the hand
of the operator, the
patient being on the
electrical stool, or at-
tached to the glass-
handled flexible tube, the patient being on the ground, or
rather not insulated. These simple instruments, with the
exception of a brass ball at the end of it, are all that
are necessary for the administration of the electric fluid,
except when shocks are to be given. In this case a Leyden
jar is indispensable. -Any Leyden jar may be used, but
the one shown and described beneath, is most convenient
for medical purposes.

Medical Jar. — (Fig. 374.) — The medical jar here repre-
sented, A c, is a bottle of about a quart in capacity, re-
presented in the cut as hanging from the projecting knob of
the prime conductor of a machine, and having other appa-
ratus attached to it. It is like an ordinary Leyden jar,
covered and lined to a certain height with tin foil. A
wooden cap is fitted to it with- a hole just admitting a glass
tube. The tube reaches below to within two inches of the
bottom, and projects upwards above the cap about three
inches. If is also lined and covered with tin-foil, so placed
that rather more than an inch of the glass is left uncovered
at the lower end, and about two inches at the upper end.
The tube is cemented to the top of the bottle, and a smaller
cap cemented on the top of the glass tube ; but before this
last is cemented on, three holes are drilled in it ; one for a
hook wherewith to suspend the phial from the conductor,
the two others are to be left open ; one of them to admit a
wire to touch the inner coating of the tube, the other a
second wire, sufficiently long to reach to the coating of the
phial — these are shown in the cut at A and B. A wire is

ELECTRICAL APPARATUS. 319

Fig. 374.

C- 8

also t\\ isted round the outer coating of the inner tube, which
projects outwards sufficiently to touch the inner coating of
the phial. On the outer coating of the phial is fastened a
hook, marked c, for the convenience of attaching a chain.
E F G H (Fig. 3*74) is a medical electrometer; its use is to
regulate the strength of the shock, for this depends upon the
intensity with which the phial is charged, no less than the
size of the phial itself. H, is a socket, and a wire attached
to it laterally. Into this socket is cemented a bent glass
tube, G ; at the opposite end of this is a second socket of
metal, also cemented to the glass. A hole is made through
this socket to admit the wire, which holds the brass balls E
and E. This wire is capable of sliding backwards and for-
wards, parallel with the horizontal part of the glass tube.
D, is supposed to be the prime conductor. When in use, to
the outer ball, F, of the electrometer, and also to the hook,
c, of the bottle, are attached chains, leading to a pair of glass-
handled directors ; the upper part of which is seen in Fig.
374, and a pair of directors complete in the Fig. 375.
We will now show the use of this apparatus. The direct-

320

BKNJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

ors are for two purposes ; first, that by means of their balls
they shall be able to direct the fluid, or shock, to any par-
ticular part only, and confine it thereto, as in the following
cut (Fig. 376) ; the shock may be given from the knee to
the foot without its affecting the rest of the body.

Fig. 375. Fig. 376.

The use of the glass handles is to prevent the operator
from participating in the shock he intends for his patient.
The operator, of course, holds the glass handles, while the
balls are made to touch the extreme points of that line
through which the shock is to pass. One director is usually
straight, and the other bent. We will now suppose that
the ball, E, of the electrometer has been placed so as to
touch the conductor, the whole apparatus being dry, and in
good working order ; and indeed that the whole is as repre-
sented in the cut ; the knobs of the directors touching, and
the wires, A and B, being in their place. Turn the machine
and the bottle will not charge, because the outside is in close
contact with the inside, there being no interruption in the
circuit anywhere. Now remove the ball, E, a short space
from D ; upon turning the machine a second time, the bottle
will become charged, because its inside is not connected by
conducting substances with its outside. A vacancy occurs
between D and E, and exactly in proportion to the size of
that vacancy will be the strength of the shock which passes
through the chains, or the balls of the directors ; and as
those balls are applied to different parts of the body, so of
course will be the strength of the shock which will be felt.
The above supposes that both wires are in the bottle ; now
if we draw out the longer wire, the only one left will be that

ELECTRICAL APPARATUS. 321

which touches the inner coating of the tube, and this tube
being so small, the shocks which will pass will be less
energetic than those given by the larger bottle, and will
altogether have a different character. They are, indeed,
intermediate in effect, between sparks and shocks, and are
called vibrations.

Fig. 377.

Fig. 377, as above, shows the usual method of adminis-
tering a shock through a number of persons at once, sup-
posing we have not the apparatus above described, and that
we desire only amusement. The phial on the table is
charged ; a chain connects its outside to the first person, he
by joining hands to the second, and so on to the end ; the
last person touching the knob of the phial with a wire and
ball. If the persons shocked turn their backs to the phial,
the shock will reach them more unexpectedly

Hydro- Electrical Machine. — The production of electricity
by the passage of steam through a small jet, was unknown
till 1840. Professor Faraday concludes that it is the effect
of the friction of globules of water against the sides of the
opening, urged forward by the rapid passage of the steam ;
the effect of this is to render the steam or water positive,
and the pipes from which it issues negative.

In the following cut (Fig. 378, next page), A, A, A, A, A, A,
are six green glass supports, three feet long ; B is a cylindri-
cal tubular boiler of rolled iron-plate, f inch thick ; its extreme

322

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

- 37a length is seven feet six

inches, one foot of which
is occupied by the smoke
chamber, making the ac-
tual length of the boiler
six and a half feet ; ils
diameter three and a
half feet. The furnace,
D, and ash-hole, c, are
contained within the
boiler ; and are furnish-
ed with a metal screen
to be applied for the
purpose of excluding
the light during the pro-
gress of one class of
experiments; F is the
water gauge ; E, the

feed-valve ; j J, are two tubes leading from the valves, K K,
to the two tubes, H ; A and i, are forty-six bent iron tubes,
terminating in jets, either half or the whole of which may
be opened by means of the lever, G G ; L, is a valve for
liberating steam during the existence of the maximum pres-
sure ; M, is the safety valve ; N, is a cap covering a jet, that
is employed for illustrating a certain mechanical action of a
jet of steam ; o, is the first portion of the funnel ; P, the
second portion, which slides into itself by a telescope joint,
so that the boiler may be insulated when the experiments
commence. The boiler is cased in wood.

379. The next figure (379),

T-~ which may be called the
prime conductor, but which
is not used for the purpose,
is a zinc case, furnished with
four rows of points. It is
placed in front of the jets,
in order to collect the elec-
tricity from the ejected va-
por ; and thus prevent its
returning to restore the equilibrium of the boiler. The
maximum pressure at the commencement of the experiments
is 80 Ibs. ; which gradually gets reduced to 40, or lower.

ELECTRICAL APPARATUS. 323

The portion of the apparatus, which is peculiarly connected
with the generation of the electricity, is a series of bent tubes
with their attached jets. Each jet consists of a brass socket,
containing a cylindrical piece of partridge wood, with a cir-
c*ular hole or passage through it, | of an inch in diameter,
into which the steam is admitted through an aperture. The
peculiar shape of this aperture appears to derive its efficacy
from the tendency it gives the steam to spread out in the
form of a cup, on entering the wooden pipe, and by that
means to bring it and the particles of water, of which it is
the carrier, into very forcible collision with the rubbing sur-
face of the wood.

The electricity produced by this engine is not so remarka-
ble for its high intensity, as for its enormous quantity. In
no case, antecedent to this, has the electricity of tension taken
so rapid a stride towards assimilating with galvanic electri-
city. Mr. Faraday's experiments on the identity of the
electricities had shown how small was the quantity obtained
from the best machines ; and had given good reason to
expect that chemical effects would be exalted when the
quantity could be increased. And such is the case here ; a
very remarkable experiment in illustration of this is, that
not only is gunpowder ignited by the passage of the spark,
but even paper and wood shavings will be inflamed when
placed in the course of the spark passing between two points
— such an effect was never before produced with common
electricity. In like manner, chemical decompositions are
effected much more readily by means of the hydro-electric,
than by that from the common machine.

GALVANIC INSTRUMENTS

Fig. 380.

Simple Galvanic Series. — This series, sometimes called
Couronne De Tasse, is a simple galvanic battery, and con-
sists of a number of glasses, jelly pots, or similar vessels, in
each of which are placed two pieces of metals, of dissimilar
electric properties ; for example, zinc and copper ; the zinc
of one vessel being connected with the copper of the other.
The outer cups, or vessels, having a wire only to its extreme
plate of metal ; the wire, therefore, of one extremity being
joined to the wire of the other extremity, completes the elec-
tric circuit, and causes the fluid to circulate around the whole
series. Price, in porcelain jars, 25 cts. each series.

Fig. 331. Faraday s Apparatus for showing the Phenomena

^ of an Electric Current independent of the Contact of

\ dissimilar Metals. — (Fig. 381.) — It consists of a
P3-N glass or porcelain trough for the dilute acid, a bent
clean zinc plate, and a platinum plate furnished with
a curved wire. If a small piece of filtering paper,
moistened with iodide of potassium, be placed on
the zinc, and the end of the wire be pressed against
it when the plates are immersed in the trough, the
iodine is thrown down on the filtering paper by
voltaic action. Price, $2.

GALVANIC INSTRUMENTS.

325

Zinc and Copper Plates, with Glass
Handles.— (Fig. 382.)— Pair of cir-
cular zinc and copper plates, with
glass insulating handles, for showing, ___

by the aid of a very delicate condens- ^^^^""|
ing electroscope, electricity developed
by two dissimilar metals that have
been in contact and are separated.
Price, $2.00.

- 332.

*

Cruikshank's Trough Fis. 3S3.

Battery (Figs. 383 and
384) consists of plates
of zinc and copper, unit-
ed by their flat surfaces
by soldering, and ce-
mented into grooves in
the sides of a trough of
baked wood, so as to leave sufficient intervals to hold small
quantities of fluid, usually about half an inch wide ; they
must of course be arranged so that all the zinc surfaces shall
be on one side, and all the copper surfaces on the other.
The battery is charged by filling the cells with a saline solu-
tion, or with dilute acid, and the galvanic circuit completed
by bringing the two wires proceeding from the ends of the
battery in contact with one another. One of the figures
represents a trough having three rows of plates connected
together by wires. Troughs of this construction are ex-
Fig. 384

ceedingly liable to get out of order, from the action of the
liquid on the wood, which it tends to warp. The plates
require to be fixed into the grooves by cement, in order to
render them water tight ; but this cement is apt to crack
from the warping of the wood and other causes, and the
28

326

BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

liquid insinuating itself into the fissures impairs the power
of the instrument by destroying the insulation of the cells.
They are superseded by more modern instruments.

Price of a set of 20 plates, $12.00.

Fis 333. The Galvanic Bat-

tery—old form. — (Fig.
385.)— This instru-
ment consists of a
trough, which has
usually been made
of earthenwaie, with
partitions of the same
material, but may be
made of baked maho-
gany with partitions
of glass ; each trough
usually has eight or
twelve cells. The
zinc and copper plates
are connected together in pairs, by a slip of metal passing
from the one and soldered to the other ; each pair being so
placed as to inclose a partition between them, and each cell
containing a plate of zinc, connected with the copper plate
of the succeeding cell, and a copper plate joined with the
zinc plate in the preceding cell. The plates are connected
together by a bar of baked wood, so as to allow of their
being let down into the cells, or lifted out together. This
battery was formerly much used, but the more recent im-
provements have entirely superseded it on account of their
superiority. Price, $10.00.

Hare's Deflagralor. — (Fig. 386, next page.) — The arrange-
ment shown in the figure, is that of Dr. Hare, of Philadel-
phia. A galvanic series, A, A, fixed in a trough,~is combined
with another trough, B, B, destitute of plates, and of a
capacity sufficient to hold all the acid necessary for an
ample charge. The trough containing the series is joined
to the other lengthwise, edge to edge ; so that when the
sides of the one are vertical, those of the other must be
horizontal. The advantage of this is, that by a partial
revolution of the two troughs, thus united, upon pivots that

GALVANIC INSTRUMENTS.
Fig. 336.

327

support them at the ends, any fluid which may be in one
trough must flow into the other, and, reversing the move-
ment, must flow back again. The galvanic series being
placed in one of the troughs, and the acid in the other, by a
movement such as has been described, the plates may all be
instantaneously subjected to the acid or removed from it ;
the pivots are made of iron, coated with brass or copper, as

OiJS BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

less liable to oxydizement. A metallic communication is
made between the coating of the pivots and the galvanic
series within. In order to produce a connexion between
one recipient of this description, and another, it is only
necessary to allow a pivot of each trough to revolve on one
of the two ends of a strap of sheet copper. To connect
with the termination of the series or poles, the conductors,
one end of each is soldered to a piece of sheet copper,
which are placed under the pivots, to be connected with the
termination of the series ; to the conductors are usually at-
tached small hand-vices for conveniently introducing wires,
charcoal points, etc. ; the plates are usually about seven
inches long, and four wide. A battery of 300 pairs may
be contained in two troughs of six feet each in length, which
is capable of producing brilliant experiments. The liquid
employed in the cells is a mixture of sulphuric or muriatic
acid, with water in the proportion of one part of the former
to fifteen or twenty of the latter.

In the figure two troughs are connected in one frame, and
both moved by levers terminating in one handle at the end
of the frame. This instrument is also superseded by the
more modern instruments. Price, 100 pairs, $80.00.

Dr. Hare's Calorimotor — (Fig. 38*7, next page) — in which
a great quantity of heat accompanied by little electrical
tension is produced, consists of such an arrangement of the
elements as to form in fact but one, or at most, two pairs of
separate plates ; for all the zinc plates in one half of the
apparatus being connected together, constitute but one plate,
while all the copper ones being united afford another. The
plates are, however, arranged in an alternating series, so
as to present their surfaces to each other without occupying
much space.

The accompanying figures represent the arrangement of
r&rts in the calorimotor. A and a are the cubical boxes
containing the one acidulated and the other pure water;
b b b b is the wooden frame containing the zinc and copper
plates alternating with each other, and from £ and |- an inch
apart ; T T t t, are masses of tin cast over the protruding
edges of the sheets which are to communicate with each
other. The smaller figure, representing a horizontal section
through the plates, shows the manner in which the junction

G A L V A N I C I N ST HU M E NTS .

Fig. 337.

329

PC c

between the several sheets and the tin masses is effected.
Between the letters z z , the zinc only is in contact with the
masses. Between c c the copper alone touches the tin. At
the back of the frame, ten sheets of copper between c c, and
ten sheets of zinc between z z, are made to communicate by
a common mass of tin, extending the whole length of the
frame between T T ; but in front, as shown in the larger
figure, there is an interstice between the mass of tin connect-
ing the ten copper sheets, and that connecting the ten zinc
sheets. The screw forceps, ff, may be seen on each side
of this interstice, holding the wire which is to undergo igni-
tion. A wooden partition, p p, separates the two sets of
plates of which the apparatus is seen to be composed. ^The
swivel at S permits the frame to be swung round after
being taken out of the acid in A, and to be lowered into the
pure water in a ; this is for the purpose of washing off, after
an experiment, the acid which might otherwise too rapidly
corrode the plates.

Dr. Hare, the inventor, regards this as furnishing an ex-
treme case of great heating power with low electric intensity,
and also as showing that the quantity of heat evolved in
28*

330

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

single large pairs is greater, but its intensity less than that
given out by an equal quantity of metallic surface arranged
in several successive pairs. Price, $25 to $40.

Wollastorfs Battery. Tig. 3^3.

—(Figs. 388 & 389.)—
A great improvement
in the construction of
galvanic batteries was
made by Dr. Wollaston
in 1815. This improve-
ment consists in extend-
ing the copperplate so
as to oppose it to every
surface of the zinc, as
represented in the cuts.
A is the rod of wood to
which the plates are screwed in the usual manner ; B, B,
the zinc plates connected as usual with the copper plates,
c, c, which are doubled over the zinc plates, and opposed
to them on both sides, any contact with the surfaces being
prevented by pieces of cork or wood placed between.

Fig. 339.

This construction of the galvanic battery is no more used,
by reason of the superiority of the new instruments.

Price, 50 pairs, $50.00.

GALVANIC INSTRUMENTS.

Fig. 390.

331

Mmmm\

Van Melseus Battery. — (Fig. 390, as above.) — This cut
represents a useful arrangement of copper and zinc plates
for a galvanic battery ; the copper soldered to the zinc in
each pair envelopes the zinc of the following pair, so as to be
exposed to the two surfaces of this plate, but without being
in contact with it. It differs from Wollaston's battery in
having the metallic plates much nearer to each other ; they
are only about one-twelfth of an inch apart, and are main-
tained thus by small pieces of cork interposed between the
plates of zinc and those of copper ; while the plates of cop-
per of the consecutive elements are separated by squares of
glass of the same size as the plates ; all the squares are
placed in a wooden frame (represented in the cut), whk-,h is
well varnished, in which they are easily retained, without it
being necessary to attach them by screws to a bar of wood,
as in the case of Wollaston's. Price, 25 pairs, $20.00.

The Cylindrical Pot Battery.— (Fig. 391, next page.)—
The cylindrical pot battery consists of a double cylinder of
copper, with a bottom of the same metal, and a movable
cylinder of zinc, between the copper cylinders; the zinc
cylinder is supported by three branches. The branches are
covered with wood to insulate them from the copper, and
are formed in the shape of rollers, with grooves entering

332 BEXJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig 391- the edge of the outer cop-

per cylinder ; there is a
cap with a binding screw
on the copper, and also on
the zinc, which form the
poles, that at the zinc be-
ing negative, and the one
at the copper being posi-
tive. The liquid employed
is a solution of blue vitriol,
(sulphate of copper) in
water, about two ounces
lo a quart of water. The
liquid requires to be re-
newed when the acid is
entirely taken up by the
zinc, which will be known
by there being no deposit

on the zinc, after being immersed for some time. The zinc
cylinder should be left in the solution only while in use, as
it soon becomes coated with a deposit, which, after used for
an hour or two, should be scraped oif with an old knife, as
a clean surface of zinc is requisite to the proper action of
the battery. The solution may remain in the copper vessel
any length of time, us it does not act on it. There is no
unpleasant smell from the use of this battery, and the acid
will not injure if spilt on furniture or clothing.

A battery five and a half inches high, and five inches
diameter, is of sufficient power for most experiments in
electro-magnetism, for which this battery is best adapted ;
where more power is required two or more may be united
and used together. Price, - $2.50.

" smaller sizes, $1.75 and $1.50.

Fig. 392.

DanieWs Single Cell Sustaining Battery. —
(Fig. 329.) — This instrument consists of a cylinder
of copper, with a bottom of the same metal, con-
taining a cup formed of unglazed porcelain, which
has a solid rod or cylinder of well amalgamated
zinc, supported in its centre. The cylinder is fur-
nished with a perforated shelf, upon which a
supply of crystals of sulphate of copper are
placed ; so that the battery being once charged,

GALVANIC INSTRUMENTS.

333

will maintain an equal action for many hours. To the
rod, or cylinder of zinc, and also to the copper cylinder,
are attached brass cups with binding screws, forming the
poles of the battery. The zinc is negative, and the copper
positive. The exterior copper vessel is usually about six
inches high, and four wide ; the porous tubes are filled with
dilute sulphuric acid (about one part of acid to one of water) ;
and the copper cylinders are tilled with a strong solution of
sulphate of copper, also acidulated by sulphuric acid ; so
that the acid in the generating cell is separated from the
solution of sulphate of copper, but the porosity of the tubes
allows of their becoming so far imbued with the acid liquid
as to admit of the passage of electricity. Price, $1.75.

Porous Cells for Galvanic Batteries. — The most important
modification of the galvanic battery, is that of the introduc-
tion of porous cells, forming what is termed a constant
battery. In all the other arrangements the electrical power
is liable to fluctuation, and for many investigations are incon-
venient and even useless ; by the introduction of these cells
those inconveniences are to a great extent obviated, and al-
though it is more complicated, its con- Figs. 393,
stant and regular action, when it is pro- ^JH^ 331,
perly constructed, amply repays the
additional trouble and expense.

They consist of cells, or cups, of un-
glazed porcelain (Figs. 393, 394, 395),
of such sizes as may suit the battery for

393.

Fig. 396.

which they are intended ; and though they separate the
acid in the outer cell from the inner part, the porosity of
the porcelain allows sufficient to penetrate through to pro-
duce a considerable galvanic action.

Price, small size, lOcts. each.
" large " 12icts. "
" for DanielFs battery,

25 cts. each.

DanielVs Six-cell Sustain-
ing Battery.— (Fig 396.)—
The annexed cut represents
a set of six of the above
batteries. The copper cy-
linder is connected in this

334

BENJ. PIKK S, JR., DESCRIPTIVE CATALOGUE.

arrangement by wires with the zinc cylinder of the next
series, and so in succession, through the arrangement, the
unconnected zinc forming the negative pole, and the uncon-
nected copper the positive pole. Price, $12.00.

Fig. 397

DanielVs Ten-celled Sustaining Battery. — (Fig. 397.) —
The above cut represents a set of ten large batteries united ;
the construction the same as the preceding. The cells of
this sustaining battery must be plentifully supplied with
sulphuric acid, without which the power is but feeble.
Mr. Daniell recommends a mixture of eight parts of water
and one of sulphuric acid which has been saturated with
sulphate of copper for the copper cell, the internal tube
being filled with the same acid solution without the copper.
The porous cells should be well soaked in dilute sulphuric
acid for an hour or two before being used ; and after being
removed from the battery, they should be repeatedly rinsed,
or allowed to soak for some time in warm water, to dissolve
out all the metallic salt from their pores. If this be not at-
tended to, they will be soon destroyed. Price, $25.

Sustaining Battery for Plating, &c. — (Fig. 398, next
page.) — This represents a convenient battery for sustaining
magnetic instruments in action for a long time ; also for
plating with gold, silver, &c. Any number may be used

GALVANIC APPARATUS.
Fig. 398.

335

as may best answer the purpose ; three or four combined is
the usual number. They consist of cups of copper, four
inches wide and four and a half inches deep, having a lip at
the side connected with the inside of the cup by a number
of holes. To the rim of each cup there is attached a brass
cup with a binding screw. In the interior there is a zinc
cylinder, one in each set having a binding screw, and the
others, stout copper wires for connecting with the copper
cups of the next series ; between the zinc and copper cylin-
ders there is a cup of porous earthenware, entirely separat-
ing the two metals. To use, fill to within half an inch of
the top the outer space, with a saturated solution of blue
vitriol (which may be about one ounce to each cup), and put
some pieces of blue vitriol in the lip to keep the solution
saturated, and in the interior of the porous cup, put a table
spoon full of common salt, or Glauber's salt, and nearly fill
with Avater ; connect the zinc of the one with the copper of
the next throughout the series, the disconnected copper and
zinc being the poles of the battery. This battery will main-
tain nearly a constant action for a week (if properly supplied
with blue vitriol, and a little salt stirred in the interior once
a day), without disconnecting the series ; though when con-
venient, it is preferable to clean the zinc cylinders oftener.
In many cases a much weaker solution of blue vitriol may
be used than that described. Price, of a set of 3, $5.25.

" 4, $7.00.

Grove's batteries, of three different sizes of four cells
each, are conveniently arranged for gilding.

Price, small size, $4.50.
" second " $5.50.
" large " $6.50.

336 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Smee's battery, also used for plating ; particularly for
Daguerreotype plates. Price, $2.25.

ELECTRO PLATING AND GILDING.

Preparation of the Solution of Silver. — Take one pint of
pure rain -or distilled water ; add to it one and a half ounces
of the cyanuret of potassium ; shake them together occasion-
ally, until the latter is entirely dissolved ; and allow the liquid
to become clear. Then add a quarter of an ounce of oxide of
silver, which will very speedily dissolve ; the dissolution
may be hastened by heat, and, after a short time, a clear
transparent solution will be obtained.

Preparation of the Gold Solution. — Warm a pint of pure
rain or distilled water, and dissolve in it one and a half
ounces of cyanuret of potassium as before ; then add a
quarter of an ounce of oxide of gold. The solution will at
first be yellowish, but will soon subside to colorless trans-
parency.

The solution is made in a glass or earthen vessel, the
article to be plated attached to the wire connected with the
zinc pole of the battery, immersing the other wire from the
copper pole of the battery, which should be tipped with
gold or platina, a little way in the solution.

An improved way for plating, and preferable in use, is to
prepare, as above, the solution, by dissolving one and a
half ounces of cyanuret of potassium in a pint of rain water,
and attach a thin plate of silver to a wire connected with
the copper pole of the battery, and immerse it in the solu-
tion ; now dip the wire from the zinc side of the battery in
the solution, but not in contact with the silver plate, and a
rapid decomposition of the metal will take place, and a
saturated solution will be obtained, which may be known by
the deposition of silver on the wire from the zinc side of the
battery. Attach the articles to be plated, as before, to the
wire from the zinc pole, allowing the silver plate to remain
in the solution to supply the silver released from the solu-
tion and deposited on the article plated. Articles not
exposed to wear may be coated in a few minutes ; spoons,
watch-cases, and articles exposed, will require from four to
six hours, the thickness of the deposit depending on the
length of time immersed. Should bubbles of gas appear

GALVANIC INSTRUMENTS.

337

about the zinc pole, or articles attached to it, less of the
surface of the silver plate is to be immersed in the solution,
or the article to be plated will be discolored. A solution
of gold may be made in the same manner by using a plate
of gold, etc.

Smee's Battery.— (Fig. 399.)— A piece Fig. 399.
of platinized silver has a bar of wood fixed
on the top to prevent contact with the
zinc, and is furnished with a binding
screw. A stout plate of well amalga-
mated zinc, of the width of the silver, is
placed on each side of the wood, and both
are held in their place by a binding screw
sufficiently wide to embrace the zincs and
the wood. This arrangement is immersed
in a jar or glass, containing dilute sul-
phuric acid, in the proportion of one of
acid to seven of water, and not the slight-
est effect is produced till a communication
is made between the metals, when it in-
stantly hisses and bubbles, and an active galvanic battery is
obtained. This battery is simple in its construction, ma-
nageable in its application, and neat in its appearance ; and
although it has not the constancy of Daniell, or the wonder-
ful activity of Grove, it may be kept in active operation for
several days. Price, small size, 82.25.

" larger " $5.00.

Grove's Battery, as arranged ly Benj. Pike, Jr. — The most
powerful galvanic battery that has yet been brought before
the public, is that of Professor Grove, who was led to the
discovery of a galvanic combination much more powerful
than any previously known.* The elements used, are a

* The manufacturer had occasion to use one of these batteries at a
public lecture, by Dr. Lardner, at the Tabernacle in New York,
before a large audience, The battery consisted of eighteen series,
contained in a small case that could be conveniently lifted about by
one person. The effect of the battery when the charcoal points
were used was most brilliant, illuminating the whole building ; and
when steel watch springs and iron turnings were burned, the most
brilliant scintillations were produced. Also exhibited one in Niblo's
Garden, at the Fair of the American Institute, in Oct., 1845, before
a number of distinguished scientific gentlemen; the battery pro-
29

338 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

strip of platinum immersed in strong nitric acid, and sepa-
rated by a porous cylinder, or cell, from well amalgamated
zinc cylinders immersed in dilute sulphuric acid ; the zinc
of the one cell being attached to the platina of the succeed-
ing cell.

Description of Grove's Galvanic Battery. — (Fig. 400, next
page.) — This consists of slips of platina, placed in porous por-
celain cups, the cups surrounded with thick zinc cylinders,
placed in a glass, or glazed porcelain vessels. The platina in
each cup is attached to the zinc cylinder in the next, except
at the extremities or poles, the platina being the one pole,
and the zinc the other ; to each of which, supports are at-
tached with brass cups, having binding screws, to receive
conducting wires for experimenting with.

The power of this instrument is about twenty times as
great as the common zinc and copper arrangement ; its price
not one quarter in proportion to its effect ; and a powerful in-
ducing the most brilliant light with the charcoal points, insupporta-
ble to the naked eye, burning the metals and decomposing water
with rapidity. A silver medal was aivarded for the battery. Also
constructed one of about one hundred series for Prof. Ellet, of the
University of S. C., who sent the following letter: —

SOUTH CAROLINA COLLEGE, June 10th, 1845.

DEAK SIR, — In reply to your request for information as to the
working of the " Grove's Galvanic Battery " you constructed for me
last summer, it. gives me great pleasure to assure you, that it has
more than equalled the high expectations I entertained.

With the whole arrangement connected in series, the effect in the
deflagration of metals, charcoal, &c., was surprisingly brilliant, as
you may judge from the fact, that the light was so intense as to pro-
duce an inflammation of the eyes, which confined me to my room
for several days, and required active medical treatment.

I would suggest to you as the result of much experience with the
instrument, that so extended an arrangement as mine is neither
necessary nor desirable for the greater number of purposes for which
a galvanic battery is required. A series of from fifteen to twenty
pairs of plates is as much as can be used to advantage for chemical
decomposition, which it effects far more vigorously than any of the
old arrangements of much greater extent : while it is at the same
time quite sufficient for producing brilliant deflagrations. One or
two pairs are enough for nearly all the experiments in Electro-Mag-
netism, including that of working Prof. Morse's telegraph.

Apart from the neatness and compactness which form so important
a feature in Grove's instrument, I have no hesitation in saying, that
I believe the experimenter will find it the most economical form of
the galvanic battery he can employ.

1 am, dear Sir, very respectfully yours,

To BENJ. PIKE, JR. WILLIAM H. E.LLET.

GALVANIC INSTRUMENTS.

339

strument is contained in a case
two feet long, one foot wide,
and six inches in depth.

Mode of using. — The plates
being properly arranged in
the cells, the external glass
vessels are to be nearly filled
with sulphuric acid, previ-
ously diluted with from 12
to 15 times its bulk of wa-
ter, and the interior porcelain
cups with strong and pure
nitric acid. The wires are
to be secured in the brass
cups with screws at the poles
of the battery, and when
steel shavings, fine wires,
watch springs, etc., attached
to one of them, are brought
in contact with the other,
combustion, with brilliant
scintillations, will be exhibit-
ed. Gold, silver, or copper
leaves, interposed between
their extremities, will burn
with bright and varied colors.
Water, with a little sulphuric
acid or common salt added
to it, may be rapidly decom-
posed by employing the
wires tipped with platina,
and the gases collected in
the glass globe furnished
with the instrument.

Charcoal points at-
tached to the wires can
be burned with a bril-
liant light. The coal
should be of hard
wood, and recently
burned. After using,
the whole should be
taken out of the case,

Fig. 400.

Fig. 401.

340

BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

the different parts well washed in water, and replaced. Care
should be taken to keep the platina slips from injury, they
being thin, and the metal valuable. They are packed in
black walnut boxes with cover, and handles at the ends.
Price, of a series of 4, small size, $4.50 ; large size, $6.50.

" 6, " $6.00; " $9.50.

" 12, " $10.00 and $12.00.

" 12, large size, $16.00 and $18.00.

" 18, " $24.00 and $27.00.

Fig 402.

Fig. 403.

Fig. 404.

Apparatus for the Decomposition of Water. — (Fig. 402,
as above.) — This consists of a globe of glass with a neck, to
which is fitted a cork having a small aperture at the side
for the escape of water ; through the cork is passed two
long wires, to the ends of which are soldered platina wires,
or a strip of platina plate projecting within the globe for an
inch or two, and separated a short distance from each
other. If the globe be filled with water, and the wires
connected with a powerful galvanic battery, the water will
be decomposed, and resolved into its elements, hydrogen
and oxygen gases. Pure water has but little conducting
power; the addition of a little sulphuric acid, or common
salt, will greatly increase the evolution of the gas.

Price, $0.75.

Apparatus for collecting the Gases Separately. — (Figs. 403
and 404.) — This consists of a glass vessel having a foot in
the form of a bowl, or large goblet, holding about a quart,

GALVANIC INSTRUMENTS.

341

having two holes in the bottom, through which are inserted
two screw cups for receiving wires from the galvanic bat-
tery, and which terminate on the inside of the glass vessel
in platina wires, or strips of platina plate ; over these are
suspended by a frame resting on the rim of the glass vessel,
two small receivers, for collecting the separate gases. The
tube collecting the hydrogen will be found to contain double
the volume of that collecting the oxygen ; the hydrogen
and oxygen gases being in water exactly as two to one in
their proportions.

Price, $4.00 ; larger size, $5.00.

Tubes for the Decomposition of Fig.405.

Water by the Galvanic Battery. —
(Fig. 405.) — This apparatus consists
of a glass tube, c, bent in the form
of a V, to each end of which a cork,
D D, is fitted, air tight, through
which cups with binding screws are
fixed, and on the interior are solder-
ed slips of platina ; in the bend of
the tube is a small hole for the es-
cape of water. To use, the instru-
ment is filled with water — usually containing a little salt —
and the poles of a powerful galvanic battery applied to the
cups. The decomposition of the water will rapidly take
place ; the hydrogen occupying the one tube, and the oxygen
the other.

The instrument is represented in the cut on a mahogany
base, having a wire support.

Price, with stand, $2.00 ; without stand, $1.50.

Decomposition Tubes. — (Fig. 406.) — This fig. 406.
apparatus, used to show the decomposition of
a neutral salt by galvanism, consists of a glass
tube in the form of a letter V, having corks
fitted to each end, with small binding screws to
receive wires from the battery, and wires or
slips of platina descending into the tubes ; the
whole is mounted on a stand. The solution of
a neutral salt, colored by litmus, is poured into the tube ; a
galvanic current being made to pass from wire to wire
through the liquid, decomposes it, drawing the alkali to one
pole, and the acid to the other, as is made visible by the
29*

342 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

changes of color produced in the different ends of the solu-
tion ; it being reddened on one side, and rendered green at
the other. Price, with binding screws, $1.75.

" without " $1.25.

Fig. 407.

The Powder Cup. — (Fig. 407, as above.) — This consists
of a glass having a neck through which the ends of two
wires, insulated from each other, are passed, and are con-
nected together within the cup by a fine platina wire. On
connecting the long ends of the wires with the poles of a
galvanic battery, the passage of the current heats the fine
platina wire to redness, and explodes any powder placed in
the cup. A piece of sulphur or phosphorus may also be
easily burned therein. Price, 80.50.

Fis-408- The Galvanic Gas Pistol—

(Fig. 408.) — This instrument
is constructed on the same
principle as the last described,
but arranged in the form of a
pistol, the wires being fastened through a brass plug which
screws into the barrel. To use, the pistol is filled with
from one third to one half of hydrogen gas, the other part
being atmospheric air, and corked ; connect one of the wires
with one of the poles of a galvanic battery, and on bringing
the other wire in contact with the other pole of the battery
the wire will be heated to redness, and the gas exploded.

Price, $3.00.

SUPPLEMENT

Fig. 783.

Pike's Improved Theodolite. — (Fig. 783.) — This instru-
ment is particularly well adapted to the purposes of
instruction, as well as for practical use. All its parts are
made large and substantial, for the measuring of horizon-
tal and vertical angles ; and for levelling it is very much

344

approved ; by the addition of a pair of small sights it is
sometimes used as a surveyor's compass. For this instru-
ment the author received, a few years since, from the
American Institute, a silver medal ; and another was
awarded the last year, by the New York State Agricul-
tural Society, at its annual fair held in the city of New
York.

The horizontal plate is nine and a half inches diameter,
graduated into degrees and half degrees, numbered from
0 to 360. The vernier plate is eight inches diameter; at
one portion it is shampered off to an edge, containing a
vernier divided from the middle both ways into thirty
parts, numbered 0, 10, 20, 30, subdividing the graduations
on the lower plate to single minutes. These two plates
are connected together by a conical axis ground in each
other, having an even and steady motion when turned.
The compass-box is nearly seven inches diameter, within
which there is a graduated circle divided into 360 degrees,
and subdivided to half degrees, numbered from the north
and south points each way, from 0 to 90. On the face
of the compass are engraved the principal points of the
compass. In the centre of the box is fixed a steel pin,
on which is poised a delicate magnetic needle, having a
jewelled centre. At the side of the compass-box there is
a small milled head-screw, by turning which a lever is
raised, and the needle lifted from its support ; by this the
fineness of the point is preserved when not required for
use. Under the lower limb is a socket fitting the conical
pin on the upper part of the parallel plates, accurately
ground together, and having a true and steady motion
when turned thereon. The parallel plates are held to-
gether by a ball and socket, and are set firm and parallel
to each other by four milled-head screws; these turn in
sockets fixed to the upper plate, while their heads press
against the lower plate, and being set in pairs opposite
each other they act in contrary directions and by this
means set up level for observation. Beneath the parallel
plates are securely jointed three mahogany legs about
four and a half feet long, square at the joint but round
below ; these when spread support the instrument at a
proper height for use. The lower limb can be fixed in
any position by tightening a clamp-screw, which causes a
collar to embrace the socket, and prevents its moving, but

SURVEYING INSTRUMENTS. 345

may be moved in any small quantity, by means of a slow
motion or tangent-screw, when required to be set in any
more exact position than the hand alone could set them.
In the same manner the upper or vernier plate may be
clamped to the lower, and a slow motion given by the
tangent-screw. On the vernier plate are two spirit-
levels, about three inches long, placed at right angles to
each other, and having adjusting screws. A frame rises
on each side of the compass-box, firmly fixed on the ver-
nier plate, which supports the pivots of the axle of the
vertical arc, or semicircle, on which the telescope is
placed ; one end of the axis has a clamp and a tangent-
screw, by which a slow motion is obtained. The divis-
ions on the arc are into thirty minutes, and reading by
the vernier plate to single minutes. The level is sup-
ported under and parallel to the telescope attached to it,
by screws having at one end lateral motion, and at the
other parallel motions, by which the level may be prop-
erly adjusted to the optical axis of the telescope. The
telescope has two collars of bell-metal, truly cylindrical,
on which it rests in its supports, and is confined in its
place by the clips, which may be opened by removing the
pins, for the purpose of reversing the telescope, or giving
it a motion on its axis for adjustment. The eye-piece is
of the best quality, having four lenses. The object is
seen upright, and not reversed as in many instruments,
and has a slide by which it can be drawn out for adjust-
ment to the eye of the observer ; also four screws for ad-
justing the axis of the eye-piece, to coincide with the
axis of the object-glass. In the focus of the eye-piece is
placed two spider lines, the one horizontal, and the other
vertical, fixed in a frame adjustible by four screws. The
object-glass is of the best achromatic kind, attached to a
moveable tube that may be thrust out, by turning a milled
head, to which a tooth and pinion movement is connected ;
by this the object-glass may be adjusted to its focus, and
show the objects in view distinctly. A brass plummet
and line are usually had with the instrument, which is
suspended from a hook under its centre, by which it can
be placed exactly over the station whence the observa-
tions are to be taken. The instrument is securely packed
hi a mahogany case. Price $130.00.

346 BEXJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

With sights to the compass-box, plumb-bob, and mag-
nifying glass for reading the divisions more closely.

Price $135.00.

Also an instrument of the same construction, having the
same size telescope and level, but with plate 7 inches
diameter, vernier plate 6 inches, compass-box 4 inches,
vertical arch, 6^ inches. Price $125.00.

The same instruments, with the tangent-screw and rack-
work motions omitted. Price $100.00.

Fig. 784.

Transit Theodolite. — (Fig. 784.) — This instrument is
constructed, in most of its parts, as the last described;
the telescope and level are of the same size, and having
the glasses of the best quality ; the tripod-stand, parallel
plates, sockets, clamps, and tangent-screws, are the same ;

SURVEYING INSTRUMENTS. 347

the horizontal limb is 7 inches in diameter, having on the
vernier plate two levels, and a 4-inch compass. The teles-
cope is fixed in the centre of the axis, and may be reversed
by turning one end over. A complete vertical circle, grad-
uated to half degrees, is on the axis of the telescope out-
side of its supports, with the vernier fixed to its branches,
and reading to single minutes. The vernier on the horizon-
tal plate is also divided to single minutes. The construc-
tion of the compass is the same as the last described. The
instrument is packed in a substantial mahogany box.

Price $125.00.

Price, without vertical circle, $120.00.

" " " and level, $115.00.

" " " " " and tangents, $100.00.

Improved Transit Theodolite. — (Fig. 785.) — This in-
strument consists of two circular plates, the upper or ver-
nier plate A turning freely upon the lower, and both have
a horizontal motion by means of the vertical axis C. This
axis consists of two parts, external and internal, the for-
mer secured to the graduated limb, the latter to the ver-
nier plate. Their form is conical, nicely fitted and ground
into each other, and having an even and steady motion
when turned. The external centre also fits into the ball
at E, and the parts are held together at the lower end of
the internal axis. The diameter of the upper plate is
greater than the lower one, having also a rim covering
the outer edge of the lower plate. Near the edge of the
lower plate on its upper surface is the graduated circle,
numbered from 0 to 360 degrees, and subdivided to half
degrees ; and on the same plane, and in close contact are
the two verniers, attached to the upper plate. These
verniers are placed on opposite sides, or 180 degrees
apart. They are divided from the centre each way into
thirty parts, numbered 0, 10, 20, 30 ; these thirty parts
correspond in extent to twenty-nine parts on the gradu-
ated circle, and consequently subdivide the same into sin-
gle minutes. The verniers and a portion of the graduated
circle are visible through openings in the upper plate,
covered by a light brass frame, and a closely-fitting glass,
in form corresponding to the arc of the circle. The par-
ticular use of this arrangement of the graduated circle
and verniers is that they may be protected from injury

348 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 785.

A, horizontal plates ; B, compass-box ; C, Vertical axis ; D, D,
verniers ; E, ball and Socket ; F, upper parallel plate ; G, lower par-
allel plate ; H, staff-head ; I, mahogany tripod legs ; K, supports for
axis of telescope ; M, telescope ; N, cross-hair with screw adjustment ;
O, screw adjustments for eye-piece ; P, milled-head turning pinion for
adjusting focus of object-glass ; Q, tangent-screw for vertical motion of
telescope. K, tangent-screw for horizontal motion of telescope ; S,
tangent-screw for moving vertical axis ; T, T, spirit-levels ; U, milled-
head screw for compass-stop.

SURVEYING INSTRUMENTS. 349

by dust, or other exposures, that other forms of construc-
tion are liable to in this arrangement — the lower plate
moving within the upper one, and only seen through the
openings and glasses; they are completely protected.
The glass covering the verniers is the finest plate-glass,
and is no obstruction in accurately reading the divisions.
The graduated circle and verniers are silvered. The
compass-box is 5J inches in diameter. Within the com-
pass-box, a graduated circle, divided into 360 degrees,
and subdivided to half degrees, and numbered from north
and south points each way from 0 to 90. On the face of
the compass are engraved the principal points of the com-
pass ; in the centre of the box is screwed a steel pin, on
Avhich is poised a delicate magnetic needle having a
jewelled centre ; at the side of the compass U, there is a
small milled-head screw, by turning which, a lever is
raised and the needle lifted from its support ; by this the
fineness of the point is preserved when not required for
use. The parallel plates, Y and G, are held together by
a ball and socket, at D, and are set firm and parallel by four
milled-head screws. These turn in sockets fixed to the
upper plate, while their bases press against the upper
side of the lower plate, and being set in pairs opposite to
each other, they act in contrary directions. The instru-
ment by this means is set up level for observation. Be-
neath the parallel plates is a screw adapted to the staff-
head, H, which is connected with brass-work, securely
jointed to three mahogany legs, about four and a half
feet long, square at the joint but round below ; these when
spread support the instrument at a proper height for use.
In the cut only the upper portion of these legs are repre-
sented. The lower plate or limb can be fixed in any
position by tightening a clamp-screw, which causes a col-
lar to embrace the socket and prevent its moving ; but it
may be moved in any small quantity by means of a slow
motion or tangent-screw, S, when required to be set in
any more exact position than the hand alone could set
them. In the same manner the upper or vernier plate
may be clamped to the lower, and a slow mytion given
by the tangent-screw, R. On one side of the vernier
plate is a spirit-level, and at right angles on the supports
of the telescope is another ; these levels have at their
ends adjusting screws by which they may be accurately

30

350 BEXJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

fixed. The telescope is fixed to a horizontal axis ; it has
a free vertical movement, and may be reversed by turn-
ing over. There is a clamp-screw near the axis for fix-
ing it, and a tangent-screw, Q, for slow motion. The
focus of the cross hairs is adjusted by sliding in or out the
eye-piece. The object-glass is brought to a proper focus
by turning the milled head, P. The central adjustment
of the cross hairs is made by four screws, N, at opposite
points in the body of the telescope, and the eye-piece
fixed central by the four screws, O. These instruments
when delivered are all accurately adjusted, but should
they at any time be deranged, directions for their adjust-
ment equally applicable to these instruments may be
found under the article Theodolite (Fig. 99), in this work,
page 85.

When required, a vertical circle is fixed to the axis, as
in the preceding instrument, and also a level attached to
the tube of the telescope ; the former would cost about
ten dollars additional, and the latter five dollars. In
the construction of the transit instrument these are not
usually wanted. These instruments are finished bright,
or polished brass, and dark or bronzed, the latter being
preferred by some on account of its being more agreeable
to the eye in a bright sun. A brass plumb-bob accom-
panies the instrument which is packed in a mahogany
case. Price $150.

Chamberlain's Patent Draughting Board (Fig. 786),
For engineers, surveyors, designers, builders, &c., &c.

Description of Chamberlain's Patent Draughting-Board.
—(Fig. 786).— No. 1. Moulding, A, B, C, D ; scales, c,f,
g, h; draught sheet space, a, b, c,d; ketch-heads, i, i, i, i;
equator, E, F ; meridian, G, H ; design, J, J ; title, A ;
copyright, B ; device, D ; points of compass, C. — No. 2.
Ketch-shanks, i, i, i, i, i, i, i ; ketch-bars, o, o, o, o ; legs,
/, Z, Z, I ; spring bale, n, n, n, n, n, n ; brackets, k, k ;
connections, m, m, m, m; panel, «, b, c, d. — No. 3. T
rule ; tongue, T, T ; right-angled back, U, U ; multan-
gular baclv V, V ; adjusting screw, S ; size of board,
23 by 29 inches. The moulding guards the surface and
guides the T rule. The scales of degrees and inches are
extensive and minutely divided. They are numbered
each way from the centres, E, F, G, H, and the subdivis-

SURVEYING INSTRUMENTS.

351

F:g ?efi.— No. 1. Front View of the Board.

J)

Fig. 786.— No. 2. Back View of the Board.

PATENTED, DEC,|849.

Fig. 786.— No. 3. Outline of T Rule

V

U

S52

PIKE'S, JR., DESCRIPTIVE CATALCGLTE.

ions have a clear and open appearance. The design, J, J,
is permanent on the board, showing its method of nse.
A sheet of drawing-paper is inserted by pressure at '«, '??,
alternate, in a few moments. The board is a combination
of several valuable instruments,
united to qualities decidedly its
own ; therefore the operator in
its use will set aside the use of
single instruments, and act at
once on general principles. The
best materials are thoroughly
combined in its construction,
and the board makes a handsome
appearance.

Price of draughting-board and
T rule, $10.

The Compound Microscope is
employed where the investiga-
tion of minute objects are re-
quired, and an observer wishes
sufficient magnifying power to
reveal them in their perfect de-
velopment. It consists of three
parts, the optical part containing
the object-glass and eye-piece,
the stage for holding the object
to be viewed, and a mirror or con-
densing lens for illuminating the
object. However various the
mechanical arrangement, these
parts are found in all, and the
principle of their management
the same.

The Compound Microscope
(Fig. 787) consists of a stout
brass tube mounted on a brass
foot or base ; a portion of the
tube is cut away for the stage
on which the object to be view-
ed is placed; below there is a
circular opening in the tube for
the light to fall on the mirror,

MICROSCOPIC INSTRUMENTS. 353

Avhich is placed within the tube and is moveable by a milled
head on the outside ; the upper portion of the tube supports
the optical part which is made to fit within a short tube, in
which it may be easily moved with nicety and steadiness,
for bringing the object into the focus of the glasses. This
instrument, though of low price, is constructed as the best,
having three lenses in the compound body, the eye-glass
being the one nearest the eye, the object-glass the nearest
the object viewed, and a larger lens than either of these
intermediate between them, called the field or amplifying
glass. In the lower-priced instruments but one object-
glass accompany them, having a power of about forty
diameters, or 1,600 times; those with two object-glasses
magnify nearly twice as much, and with three, about 100
diameters, or 10,000 times. The size of this instrument
is one third larger than the cut. A test-object, several
glasses for laying objects on, and a pair of tweezers,
accompany the instrument ; the whole packed in a neat
mahogany box. Price, ordinary quality, $'3.00.

" best quality, $3.50.

Larger size, one half larger than cut, with one addition-
al object-glass. Price $5.00.

Largest size, twice the size of the cut, 11 inches long,
body tube 2 inches diameter, with three object-glasses,
condensing lens for illuminating opaque objects, and addi-
tional test-object and glasses. Price $9.00.

Achromatic Microscopes. — " The rapid advances which
have been made in modern times toward a correct knowl-
edge of the intimate structure of animate and inanimate
bodies, by the employment of the microscope, have given
to this instrument an importance second only to that of
the telescope. By its agency alone, have crude notions
and theories been swept away, and science in civilized
countries made to stand on a firmer basis. In this land
of machinery and manufactures, artists have not been
found wanting to devote their time and talents to the con-
version to what might once have been an amusing instru-
ment or a toy, into one of the most powerful auxiliaries
that can be employed in scientific research. In propor-
tion to its use, such has been the demand for improvement
in its construction, that both amateur and optician have
labored together to bring it to its present state of perfec-
tion." 30*

354 BENJ. PIKE'*, JR., DESCRIPTIVE CATALOGUE.

Microscopic investigation being now considered indis-
pensable in the various scientific researches in anatomy
and physiology, important improvements have been effect-
ed in the optical and mechanical construction of these in-
struments, especially in the adaptation of achromatic
object-glasses, by the aid of which alone, delicate struc-
tures can be satisfactorily developed ; but which have
hitherto been excluded from general use from their very
expensive character. Achromatic microscopes can now
be supplied with excellent lenses, and all the most ap-
proved mechanical arrangements, at a very moderate
cost. The author having devoted considerable attention
to this branch of his trade, can furnish instruments, the
optical and mechanical structure of which will bear com-
parison with the most reputed manufacture.

Ross Confound Achromatic Microscope, No. 1. — This
instrument (Fig. 788) consists of a brass pillar, about five
inches long, screwed into a tripod base ; the upper part
of the pillar is a moveable joint, having attached an arm
supporting the compound body of the instrument, and a
square brass bar upon which slides the stage, which is
moveable by a milled head and rack and pinion motion.
The stage is a large flat plate with a central opening, and
provided with spring clips and other apparatus for hold-
ing the objects. Near the lower end of the brass bar is
the concave mirror, moveable in various ways, for reflect-
ing the light through the centre of the stage upon the
object thereon placed. On the under side of the stage is
the diaphragm, used for cutting off extraneous light when
viewing minute transparent objects ; it consists of a plate
of brass perforated with several holes of different sizes ;
this revolves on a pivot so as to bring each hole in suc-
cession under the object-glass. This microscope has a
well-constructed set of eye-glasses, and three achromatic
lenses, which may be used together, in pairs or singly, as
different degrees of magnifying power are required.
By means of the joint the instrument may be turned in a
horizontal position, enabling the observer to use the in-
strument in some examinations with more ease than when
in the vertical position. The instrument when set up is
about ten inches high ; is supplied with a dissecting-knife,
point, forceps, several test-objects, and slips of glass on
which to place objects. The parts may be unscrewed,

MICROSCOPIC INSTRUMENTS.

355

and are compactly filled in a neat mahogany case ; size,
eight inches long by six inches wide, and three inches
deep. Price $22.50.

BEXJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Rons Compound Achromatic Microscope, No. 2. — This
instrument (Fig-. 789) consists cf A, compound body; B,
mirror; C, stage for holding- object to be examined; D,
pinion with milled head to adjust the object-glasses to
their focus ; E, round brass column supporting- stage and
mirror; F, pillar, with cradle-joint; G, tripod stand; H,
condenser; I, steel forceps; K, extra eye-piece; L,
object-glass with low power; M, dissecting-knife ; N,
dissecting-point ; O, brass forceps ; P, slider, containing
test-object; Q, slips of glass; 11, fluid box. This instru-
ment, though one of moderate cost, is both in respect to
its achromatic lenses and its mounting, of the finest work-
manship ; its construction is convenient and elegant. By
means of the cradle-joint the instrument may be used in
a horizontal, inclined, or vertical position, and for general
purposes has no superior at its price.

Description. — To a heavy tripod base is screwed a brass
pillar with a cradle-joint at the top; from the moveable
part of the joint an arm or cross-piece extends, carrying
a circular column, to which is attached the stage, or part
on which objects are placed for examination, Avhich is a
large flat plate, having a central opening, over which the
sliders containing objects for examination are placed ;
small spring clips moveable up and down in sockets in
the stage may be pressed over the slider to secure it from
falling, when the instrument is used in an inclined or
horizontal position ; beneath the stage-plate is the dia-
phragm, which is a plate of brass perforated with four or
more holes of different sizes ; this revolves on a pivot so
as to bring each hole in succession under the object-glass,
and is used in modifying the light in examining minute
transparent objects. There is a hole in the stage-plate
for receiving the spring forceps, and a socket for the con-
denser. The mirror consists of a circular brass frame, in
which are set two silvered glasses, one concave and the
other plane, and two inches in diameter ; the former re-
flects the light in converging, and the latter in parallel
rays; for facility of adjustment the frame carrying the
glasses is made to turn in every direction, by means of
joints, and adapted to a tube fitting the brass column,
which may be slid either up or down by pressing two
small handles projecting from the sides ; by this move-
ment, the rays reflected from the concave mirror may be

Mir jinsconc. i .\STRTIMK.\TS.

Fig. 783.

357

358 BB;NJ. PIKK'S, JR., DESCRIPTIVE CATALOGUE.

brought to a focus or not, as required upon any given
object on the stage. The compound body is a tube of brass
about seven inches long, and one and a quarter inches
diameter. It contains the eye-piece at the upper end, and
the object-glasses at the other, screwed to an arm having
a square bar which is fitted to move by tooth and pinion
motion within the round brass column ; to its upper end
the eye-pieces are adapted, to its lower the object-glasses.
As the latter are of different magnifying powers, and also
the objects to be examined rarely of the same thickness,
it is required that there should be a focal adjustment;
this is effected by a tooth and pinion arrangement in con-
nection with the square bar sliding within the round col-
umn E, and motion given by turning the milled head, D,
by which the whole tube carrying the eye-piece and
object-glasses is made to approach or recede from the
object. The eye-piece consists of two plano-convex
lenses ; the smaller one is called the eye-glass, and the
larger the field-glass ; they are set in brass cells, and
mounted in a tube whose length is about equal to half of
the sum of their focus. Between the lenses is placed a
stop, or diaphragm, for diminishing the spherical abberra-
tion. The inside of these tubes, and also of all other
parts through which the light passes, is blackened, so
that no other rays than those from the mirror should in-
terfere with the illumination. The achromatic object-
glasses are three in number, and screw together, being
so arranged that one, two, or three may be used according
to the magnifying power required. There is also a double
convex lens in a cell, useful where a low power is required.
The condenser, H, or illuminating lens for opaque objects,
is a plano-convex lens of short focus set in a brass frame,
and supported by one of its arms in a socket attached to
the stage-plate ; the arms are jointed, and the lens may
be set in any position required to receive the light and
condense it on the object to be examined. The steel for-
ceps, I, for holding small objects, are formed at the end of
a small wire, and made to slide in a small tube having a pin
projecting to fix it in a hole in the stage ; the forceps are
opened by pressing small studs between the thumb and
finger. The dissecting-knife, M, and point, N, are con-
venient for separating parts of objects, and the brass for-
ceps, 0, for taking up small objects. The fluid-box, R,

MICROSCOPIC I:\STRIMK.\TS. 359

is of brass, with a glass bottom, and used for containing
any liquid to be examined. Several test-objects, P, and
glass sliders are sent with the microscope. This instru-
ment in the vertical position is from fourteen to fifteen
inches high ; but the parts are made to separate in an
easy manner by screws, and every part neatly and
securely packed in a mahogany box with lock and key,
the blocks supporting the parts being lined Avith velvet,
and the box, inside and outside, well polished ; size of
box, ten inches long by eight wide, and three and a half
deep. Price $40.00.

Ross Compound Achromatic Microscope, No. 3. — This
is the same instrument as the preceding one, but having
several additions, as follows : One extra set of three
achromatic object-glasses of higher power; one extra
eye-piece of high power; and a stage with additional
plate, having a slow motion for extreme fine adjustment.
iFor the usual purposes of a compound achromatic micro-
scope, the magnifying power of the instrument (fig. 789)
is sufficient, and, unless the operator is skilled in the
operation of the instrument, the power is about as high as
can be used to advantage ; but there are those that prefer,
and others that require, a set of object-glasses of higher
power, in addition to the set usually supplied ; and to
give efficiency to the increased power a finer adjustment
than the rack and pinion motion is required ; and for this
purpose the stage is formed of two plates/ the upper one
being moveable by a fine screw arrangement, which is
attached to the under side of the lower plate ; by turning
a milled-head the two plates are separated, the upper one
moving sufficiently slow for a very nice adjustment ; with
these differences the instrument is the same as fig. 789.

Price $55.00.

Nachet's Achromatic Microscope. — This instrument
(fig. 790) is constructed with a circular foot or base,
about four inches in diameter, loaded with lead ; upon
this is fitted a stout brass tube, with an oblong opening
in the front for the light to fall on the mirror, about three
inches high ; on the tube the stage-plate rests, haying a
circular opening in the centre, and over which the object
to be magnified is placed.

360 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 790

MICROSCOPIC INSTRUMENTS. 361

A, compound body ; B, milled-head for fine adjustment;
C, three achromatic object-glasses; D, moveable stage ; E,
milled-head screws for moving stage ; F, mirror for illu-
minating the object ; G, milled-head for moving mirror ;
H, frame for holding polarizing apparatus ; I, lever for
moving frame of polarizing apparatus ; K, condenser for
illuminating opaque objects; L, test-object; M. microm-
eter ; N, achromatic object-glass of low power ; O, three
achromatic lenses medium power ; P, three achromatic
lenses high power; R, dissecting-point ; S, dissecting-
knife ; T, forceps.

The mirror, F, consists of a frame of brass, in which
are set two silvered glasses, one concave and the other
plane ; the former reflects the light in converging, and
the latter in parallel rays. For proper adjustment the
frame and glasses are made to turn on joints, so that the
rays reflected may be made to fall upon any given object
on the stage. The tube may be turned around on the
foot, and the stage on the tube, so that not only can the
light falling on the mirror be put in any situation, but the
stage, and with it the object, can be revolved, and rays,
however oblique, may be thrown on all sides of any
object. Beneath the stage-plate, and within the tube, is
a frame, H, with a circular opening in the centre for re-
ceiving various appendages to the instrument, as the dia-
phragm, and polarizing apparatus ; this frame is jointed
so that it may be raised and depressed by the lever, I.
To the stage-plate is fixed the support for the compound
body, A, which is a brass tube about seven inches long,
and containing the object-glass at the lower end, and the
eye-piece at the upper end. To the stage-plate are fixed
two brass springs, about two inches long, moveable from
the stage by pins fitting sockets in the stage-plate, by
which any slider placed beneath, and the springs pressed
thereon, may be confined ; and when required to turn the
microscope in a horizontal position, they are not dis-
placed. There are three eye-pieces belonging to these
instruments, of different powers; each one consists of two
plano-convex lenses placed at a distance from each other,
equal to half the sum of their focal lengths ; the plane
surfaces of the lenses are towards the eye, and the nearest
the eye is called the eye-glass, while that more distant is
called the field-glass. A stop or diaphragm is placed

31

362 i:Ei\j. PIKE'S, JK., DESCRIPTIVE CATALOGUE.

half Avay between the two lenses, for the purpose of
diminishing the spherical abberration. Each of these
eye-pieces fit within the upper end of the compound
body, and may be used as occasion requires. To the low-
er end of the compound body, which is somewhat conical,
are fitted, by fine screws, the object-glasses. With this
instrument there are usually three sets, having magnify-
ing powers of 100, 300, and 500 diameters, the first being
a combination of two achromatic lenses, and the two
others combinations of three achromatic lenses; these
can be used either singly or in combination, the latter
having the best effect. The coarse adjustment of the
object-glasses is made by sliding the compound body, A,
up or down, in a nicely-fitting tube fixed to its support,
while the fine adjustment is effected by the screw at the
milled-head, B, by which the support and the compound
body also are raised or depressed; the compound body
can not only be moved up and down in the tube, but
taken away for changing the powers or cleaning the
lenses. The condenser, K, or illuminating lens, for
opaque objects, is a plano-convex lens of short focus, set
in a brass frame, and supported by arms with moveable
joints to a brass foot ; by this arrangement the lens may
be set in any position required to receive the light, and
condense it on the object to be examined. There are
three diaphragms with this instrument ; they are black-
ened brass cells of about half an inch in diameter, one
having an aperture of a quarter of an inch, the others an
eighth and sixteenth ; they fit in the frame, H, from the
upper side of the stage-plate; their use is to modify the
rays reflected from the mirror, when required for the
object under examination, and to limit the pencil of
light allowed to fall thereon. The fluid cell is an oblong
brass frame, about an inch and a half long, and a quarter
of an inch deep, having a glass bottom cemented within ;
it is used for holding various fluids in their examination.
With the addition of a few test-objects, P, diseecting-
knife, II, point, S, and forceps, T, we have described
the usual parts and accompaniments of a good achromatic
microscope, in which great steadiness, accuracy of adjust-
ment, portability, and other valuable requisites, have been
successfully carried out.

There remain several important appendages which

MICROSCOPIC INSTRUMENTS. 363

accompany more expensive instruments, which we pro-
ceed to describe.

A Moveabh Stage, D, composed of a si id ing-plate,
which is made to move over another plate by means of
two screws placed diagonally, a curved spring keeping
the plate in contact with the screws. By this contrivance
an object, when laid on the stage, is capable of being
moved in any horizontal direction, so that every part of
it can be successively brought into view ; the lower plate
has three pieces of brass projecting from its circumference,
to fit over the edge of the stage-plate.

The Stage Micrometer, M, for measuring the size of
small objects, consists of a glass about a quarter of an
inch in diameter, set in a brass frame about two and a
half inches long, and one third wide. On the surface of
the glass is ruled with the point of a fine diamond, a scale
occupying one twenty-fifth part of an inch, within which
are accurately divided one hundred equal parts; each
division is therefore one twenty -five hundredth of an inch
apart. These minute divisions are clearly discerned, and
have each a visible length, even under the low powers
of the microscope ; and by laying a small object, as a
fibre of silk, or a hair, across this scale, its dimensions
can be accurately determined, as the object and the lines
on the glass can be seen at one and the same time ; if the
breadth of the object occupies twenty-five divisions of the
scale, its breadth is one hundredth of an inch ; if it covers
ten only, its breadth is one two-hundred-and -fiftieth of an
inch.

The Camera Lmida is a valuable addition to a micro-
scope ; it consists of a four-sided prism of glass, set in a
brass frame or case, and by means of a short tube, or
spring clip, applied to the tube of either of the eye-
pieces, so that the prism may be directly in front of the
eye-glass. To use conveniently, the microscope should
be laid in a horizontal position, and supported at a proper
distance from the table for convenient use, say from one
to two feet, and a sheet of white paper laid on the table
beneath the prism ; if now the light be reflected through
the compound body, an eye placed over the small hole in
the frame of the prism, with the sight directed toward the
paper, will see the image of any object on the stage, if in
the foous, on the sheet of white paper. Should the whole

3G4 DENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

of the field of view be not well illuminated, the prism
may be adjusted by turning on its pivots, or a slight move-
ment round the eye-piece, the observer will now bring
his eye so near the edge of the prism, that he may be able
to see at one and the same time, the image of the object,
and the point of a pencil. When he has accomplished
this, the pencil may be moved along the outline of the
image so as to trace it on the paper ; however easy this
may appear in description, it will be found somewhat
difficult in practice, and the observer should not be foiled
in his first attempts, but persevere until he accomplishes
his purposes; he may find that he can see the pencil-point,
and all at once it disappears ; this happens from the move-
ment of the axis of the eye. The pencil should be kept
on the paper, and the eye moved about until the pencil is
seen again, when the eye is to be kept steadily fixed in
the same position, until the entire outline is traced. The
operation may be conducted by lamplight, or the diffused
light of day. If, after the drawing is made, the object on
the stage be removed, and the micrometer fixed thereon
in its place, and an image of its magnified divisions drawn,
which being compared with that made of the magnified
object, the dimensions of the latter are readily ascertained.
The size of the picture drawn on the paper, will like all
others made by the camera, depend on the relative dis-
tance between the object and the paper.

Polarizing Apparatus. — For the purposes of polarizing
light, various substances have been employed ; sometimes
a crystalline mineral, called tourmaline, in the form of a
thin plate, confined between-two thin glasses, and set in a
brass cell ; but the most useful for the microscope is a
crystal of Iceland spar, called Nicol's prism, consisting of
a romb of the spar divided into two equal portions, in a
plane passing through the acute lateral angles, and nearly
touching the obtuse solid angles, the cut surfaces havingbeen
carefully polished, are then cemented together with Canada
balsam, so as to form a romb of nearly the same shape as
it was before cutting, and capable of transmitting a single
image only. As adapted to the microscope, one of these
prisms is fitted in a brass cell by means of a piece of cork,
so constructed that it may be placed in the circular open-
ing in the frame, H, beneath the stage-plate, and is moved
up and down by the lever, I ; this lower prism is called

MICROSCOPIC INSTRUMENTS. 365

the polarizer. Another prism is adapted to the compound
body, called the analyzer, of the same construction as the
lower one; the conical end to which the object-glasses
are usually screwed, is taken away, and another similar
piece, having the same screw for the object-glasses, but
having a tube entering the compound body in which is
contained the prism ; on passing rays from the mirror
through the instrument, as arranged with these prisms,
and revolving either of the prisms, by turning the stage
or the compound body ; it will be found that there are
two positions in each revolution in which no light will
pass through the prisms, but be completely darkened ; if
now a plate of sellenite, or other refracting crystal, be
placed on the stage, and be brought into the focus of the
object-glass, and the light be brought to pass through the
prisms, the sellenite will produce a color according to its
thickness ; if one of the prisms be now revolved slowly,
we shall find more and more light will be transmitted,
but the intensity of the color will be diminished ; and
when a quarter of a revolution has been accomplished,
the brilliancy of the color will reappear, but Avhat was
originally red will become green, and the green will be-
come red at a second quarter revolution ; if the sellenite
be removed and some very thin crystals of sulphate of
copper, tartaric acid, or many other crystalline substances
be substituted for it, a most gorgeous set of colors will be
seen ; and as the prism is being revolved, the same alter-
nations of color will take place as in the sellenite ; every
color and every tint of each primary color may be pro-
duced by variations of the doubly refracting substances,
and the thickness of the same through which the polar-
ized light passes. The uses of polarized light in micro-
scopic examinations, to their full extent, have not yet
been fully developed ; but they are many, and objects
that are far too delicate to exhibit any structure under
ordinary illumination, will often be well seen under polar-
ized light. All structures belonging either to the animal,
vegetable, or mineral kingdom, in which the power of un-
equal or double refraction is suspected to be present, are
those that should especially be investigated by polarized
light.

Microscope, having 3-inch foot or base, 3-inch stage-
plate, compound body 8 inches long, fine adjustment

31*

3GG BEXJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

attached to an extra stage-plate, one set of three achro-
matic object-glasses, condenser with arms to support from
stage-plate, fluid-cell, dissecting instruments, pair of for-
ceps, and three test-objects. Price $25.00.

Microscope, same as above, but having 3^ inch base,
3 inch stage-plate, and one extra eye-piece of greater
power. Price $35.00.

Microscope, same as last, with the addition of the move-
able stage, D. Price $45.00.

Microscope, with 3j-inch base, 2f-inch stage-plate, 8-
inch compound body, 3 eye-pieces of different powers, 2
sets of achromatic object-glasses, condenser with arms to
support from stage-plate, fluid-cell, dissecting instruments,
forceps, 3 test-objects, moveable frame below stage-plate,
camera lucida, and polarizing apparatus. Price $75.00.

Microscope, with 4-inch base, 3-inch stage-plate, 8-inch
compound body, 3 eye-pieces, 3 sets of object-glasses, con-
denser on brass foot, fluid-cell, dissecting instruments,
forceps, 6 test-objects, micrometer, moveable frame, H,
below stage-plate, and moveable stage-plates, D.

Price $85.00.

Microscope, same as last, with the addition of the cam-
era lucida, and polarizing apparatus ; this instrument in-
cludes all the parts and appendages described, fig. 790.

Price $105.00.

Microscope, same as the preceding, but extra large
size, 5-inch base, 4-inch stage-plate ; extra part with
prism to incline eye-piece, and one additional set of three
achromatic object-glasses. Price $135.00.

Microscopes of Ross's, and-Smith and Beck's, more ex-
pensive constructions, from $150.00 to $200.00.

The Equatorial Telescope. — The equatorial instrument
is intended to answer a number of useful purposes in prac-
tical astronomy. Besides answering the general purposes
of a quadrant, a transit instrument, a theodolite, and an
azimuth instrument, it is almost the only instrument
adapted for following the stars and planets in their ap-
parent diurnal motions. Many of these instruments are
somewhat complicated, and very expensive. The author
to supply the wants of his many patrons, has constructed
the following instruments, which may be purchased at a
moderate cost. They may be made use of in any steady

ASTROXOMICAL INSTRUMENTS. 367

Fig. 791.

368 BF.XJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

room or place, and are well adapted for general observa-
tions, and performing most of the useful problems in as-
tronomical science.

The basis of all equatorial instruments is a revolving
axis placed parallel to the axis of the earth, by which an
attached telescope is made to follow a star, or other celes-
tial bodies, in the arc of its diurnal revolution, without
the trouble of repeated adjustments for changes of eleva-
tion, which quadrants and circles with vertical and hor-
izontal axes require. Such an instrument is not only
convenient for many useful and interesting purposes in
celestial observations, but is essentially requisite in cer-
tain cases, particularly in examining and measuring the
relative positions of two contiguous bodies, or in deter-
mining the diameters of the planets when the spider's
line micrometer is used. The great cost of these instru-
ments has hitherto prevented their coming into very gen-
eral use, though it is one of the most pleasing and useful
instruments connected with astronomical science.

The principal parts of the equatorial instrument (fig.
791) are : The lower or horizontal plates, the semicircle
of altitude, the equatorial plates, and the semicircle of
declination on which the telescope is mounted. The
lower horizontal plate is nine inches in diameter, and
fastened to the round head of the mahogany stand ; it is
divided into 360 degrees, which are subdivided into half
degrees or 30 minutes, and numbered from 0 every 10
degrees, the upper horizontal plate is fitted to the lower
by a conical axis, passing through the lower plate and
having a large winged-screw nut on the inner side of the
stand, by which it may be firmly held in any position it
may be set. On the top of the upper horizontal plate
are two levels at right angles to each other, having ad-
justments at their ends, by which they may be accurate-
ly set, and by means of the three screws on which the
instrument is supported, the horizontal plates may be
accurately leveled. The semicircle of altitude is seven
and a half inches in diameter, is attached to a horizontal
axis, and supported by two standards fastened to the up-
per horizontal plate ; it is divided into two quadrants of
90 degrees each, subdivided into half degrees, and num-
bered from 0 to 90 each way, a vernier reading to single
minutes, and a tangent-screw, by which the vertical arc

ASTRONOMICAL I \STRU.M KXTS. 3G9

is moved up or down ; the centre part of the axis of this
arc is enlarged, and has an opening for receiving the
axis of the equatorial circles, to which they are firmly
secured. The equatorial circles are eight inches in di-
ameter, and consist of two brass plates with shampered
edges, the upper or vernier-plate turning freely on the
lower or graduated circle, having a horizontal motion by
means of a vertical axis ; this axis consists of two parts,
external and internal, the former secured to the graduated
hour-circle, and the latter to the vernier-plate. Their
form is conical, nicely fitted and ground into each other,
having an easy and steady motion when turned. The
equatorial hour-circle is divided into 720 parts, and num-
bered into degrees and half degrees, from 0 to 360 ; also
into twice twelve hours, with the subdivisions reading to
two minutes ; these are subdivided by the vernier into
single minutes for the half degrees, and into four seconds
for the hour circle. In the upper edge of the vernier-
plate is cut, in its entire circumference, a thread, into
which works an endless screw, by which a slow and
steady motion may be given to the upper plate for any
number of revolutions.

The semicircle of declination, 7J inches in diameter, is
attached to an axis, and by two standards supported and
fixed on the upper equatorial plate; it is divided into
two quadrants of 90 degrees each, subdivided to thirty
minutes, and having a nonius by which it may be read to
single minutes ; it has also a slow-motion endless screw,
by which it may be elevated or depressed ; on the upper
edge of this semicircle there is screwed a broad plate,
about twelve inches long, to Avhich the telescope is at-
tached, by means of two milled-head screws; the body
of the telescope is about four feet long, and the terrestrial
or long eye-piece about one foot long; the diameter of
the object-glass is three inches ; the power of the terres-
trial eye-piece is 50 times ; two celestial eye-pieces also
accompany the instrument, having powers of 120, and 180
to 200 times. Extra eye-pieces of intermediate powers
of 80 and 150 times may be had at an additional cost.
The adjustment of the eye-pieces to the focus of the
object-glass, is made first by sliding into a closely fitting
tube, as near as convenient for distinct observation ; and
then for fine adjustment, the eye-piece is moved in or out

370 BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE.

by a, tooth-and-pinion arrangement, moved by turning a
milled-head at the side of the main tube. Two brass
cells, with screws fitting the ends of the celestial eye-
pieces, .containing dark glasses for solar observations, are
sent with the instrument.

The stand on which the telescope with its equatorial
parts are mounted, is of mahogany, well polished, and is
formed of three stout legs, about four and a half feet high,
cut out at the upper portions to form two branches, which
are jointed to the circular top, and also to the triangular
arms from the centre-piece, and secured firmly together
by brass bolts with winged-screw nuts that can be tight-
ened as required. At the bottom of each leg there is a
brass socket, with a large milled screw — by the adjust-
ment of these screws the instrument is levelled. On the
centre-piece which braces the three legs firm, there is an
accurate compass, 4 inches in diameter, divided into 360
degrees, and numbered from north and south points to 90
degrees each way, having the usual points of the com-
pass engraved on its face ; the compass is fastened by a
bolt passing through the wood, with screw beneath, and
can be removed, if occasion requires it, for other uses.

Price $300.00.
Additional eye-pieces, each $5.00.

Equatorial Telescope. — (Fig. 792.) — This instrument
differs from the previously-described one in having the
telescope at the side of the equatorial plates, supported
at one end by a long axis fixed across the equatorial
plates, and at the other end of the axis an entire circle in
place of the semicircle of declination ; by this arrange-
ment the telescope can be revolved freely and observa-
tions made in the highest altitudes, which the construction
of the previously-described instrument does not admit of.
The axis is fixed across the centre of the equatorial
plates, and supported by two standards ; to one of these
standards is screwed a frame, one end carrying the ver-
nier, and the other the clamp and screw for tightening
the circle, and the tangent-screw for slow motion ; at this
end of the axle there is a counterpoise-weight for balan-
cing the telescope. The divisions on the vertical circle
are degrees and half degrees, numbered each way from 0
to 180, and the vernier subdividing the divisions on the

ASTRONOMICAL INSTRUMENTS.

Fig. 792.

371

IJ72 BKNJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

circle into single minutes. With these differences the
instrument is the same as the previously-described one.

Price $350.00.

Fig. 793.

\B.PIKE.JX!

2&4 BROAD WAY.

\NEW-YORKl

WTicatstone's Stcrescope. — (Fig. 793.) — The sterescope
is an instrument by which two perspective diagrams,
being right and left eye-views of the same solid, are seen
at one view as solid as the object itself, or small drawings
having a little difference in their perspective, are made
to represent the complete effect of reality. This instru-
ment is considered as one of the most curious and beauti-
ful in the entire range of experimental optics.

The body of the instrument is usually of mahogany or
rosewood, but the commoner ones are of tin, ja panned.
At the bottom there is an aperture for sliding in the views,
and at the front a door for admitting and regulating the
quantity of light. The eye-tubes are of brass, about the
form of those used in double opera-glasses, having pris-
matic convex lenses so arranged that they refract or
throw the images out of the direct line to the centre be-
tween the eyes, and each image being in this way re-
moved in a direction toward each other, so as to combine

OPTICAL INSTRUMENTS. 373

in one, and produce the effect of solidity. Tlie diagrams
are usually on cardboard, and about three inches wide, by
six or seven inches long ; twelve to twenty -five accom-
pany each instrument. The best effect is produced by
viewing- daguerreotypes; these are either on metal or
glass. For using those on glass, the bottom of the box is
cut out and sometimes supplied with a ground glass, the
pictures being viewed by the light through the glass with
the door shut.

Price, according to quality, $3.50, $5.00, $6.00, and
$7.00.

A plain article in tin frame, with 12 diagrams, $2.00,
$2.50, and $3.00.

Daguerreotype views on metal, each $2.00.
glass, each $2.00.

Claude Lorraine Mirror. — " I don't know whether it
was the invention of the famous Italian artist, who was in
landscape paintings what Landseer is in the representa-
tion of animals ; or whether the mirror was so called be-
cause, like Claude Lorraine, it is said to improve upon
nature ; but, at all events, it is a great curiosity. Its con-
struction is the same with the ordinary looking-glass,
except that jet is used in place of quicksilver, and it is
intended to reflect only the inanimate world. The
Claude Lorraine mirror derives its value from the princi-
ple that all objects are more beautiful in miniature, which
renders their defects less apparent ; for the unsightly
strikes the eye with immediate pain, while that which is
perfect grows upon us more gradually. With this mirror,
you frame for yourself, as it were, little landscapes at
every turn, in which the sky is softer, the grass richer,
and the foliage more graceful, than anything you can see
without it."

These mirrors are mounted in neat embossed morocco
cases. 4 by 5| inches, price $2.50.

5 by 6 inches, price $4.50.

6 by 7 inches, price $6.00.

The Dioptric Lantern. — (Fig. 794.) — The Improved
Prismatic Dioptric Dissolving Apparatus, invented by
the Rev.»St. Vincent Beechey, possesses, within less com-
pass than a single lantern of the ordinary description, all

32

374 LENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 794.

the powers of two lanterns, with only one small lamp of
intense brightness, free from the objectionable smell and
great heat of ordinary lamps, whereby a disc of twenty
feet for each tube may be obtained ; each disc is capable
of being darkened to any required extent, without the
least shadow on any particular portion of the picture ;
and, from the superiority in the optical arrangements of
the apparatus, each picture is perfectly flat and well de-
fined to the extreme edge. As the two discs may be
thrown either together on one circle, or two united at
various distances in length upon the screen, the number
of effects which may be produced may be easily imagined ;
they present a succession of dissolving views, so accurate-
ly and gradually dissolving, that the most experienced
eye can not perceive the process going on. The porta-
bility of the apparatus is also of importance; the whole
can be packed, viz., the lantern, gas-bag, retort, purifier,

DISSOLVING VIEW INSTRUMENTS. 375

&c., with several dozen slides, in a case, two feet long,
twenty inches wide, and fifteen deep — a decided advan-
tage over every other description of dissolving-view ap-
paratus.

The lamp is upon the ordinary fountain-lamp princi-
ple, with a circular wick like an argand burner, with a
small lime-hall suspended in the apex of the flame. In
the exact centre of the wick, and precisely level with the
top of it when raised, is a small tube for supplying oxygen
gas; at the bottom of this tube is a cup to receive any
overflow of oil, and underneath which is an elbow, ter-
minating with a union, where a flexible tube is united,
the other end being attached to a gas-bag filled with gas.
In trimming the lamp, care should be taken to cut the
cotton to a uniform height, to see that the edges form a
regular circle round the inner tube, without any portion
of the wick coming in contact with the oxygen tube ; and
the under part of the lime-ball should be suspended half
an inch from, and exactly over, the centre of the oxygen
tube. The wick of the lamp should not be raised too
high, but just to produce as much smoke as will be entire-
ly absorbed by the gas. Apply a pressure of about twen-
ty pounds on the bag, and sufficient gas only turned on
by the small stop-cock to produce perfect brightness.
This should be particularly attended to ; if too much gas
is turned on, the lime-ball is cooled, and gas wasted. The
advantages of this mode of illumination, and its applica-
bility to dissolving views, are : first, its intense brightness,
being of sufficient illuminating power, with condensers of
only three and three quarters inches diameter, to throw a
sharp and well-defined disc of twenty feet diameter; sec-
ondly, its maintaining a uniform brightness for two or
three hours consecutively, and, in this respect, superior
to the oxy-hydrogen light ; thirdly, the simplicity of ar-
rangement, and facility of management; fourthly, the
economy, the consumption of gas being very little more
than one cubic foot, and one ounce and a half of oil, per
hour.

Directions for Use. — The lantern should be placed from
twelve to fifteen feet from the screen, by which a disc of
these dimensions will be obtained ; and as the distance is
increased between the lantern and the screen, so in the
game ratio will the size of the disc be increased ; but if

376 BE.XJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

this extends beyond twenty feet, it will be necessary to
change one of the object-lenses in each tube for those of
longer foci; this is easily effected, by drawing out the
tube containing the lenses, removing the one loose in the
cell, and substituting one of longer focus. Perfect coin-
cidence of discs is obtained, laterally, by moving the
prism on its hinged joint, and perpendicularly, by mov-
ing round the tube containing the shutter. The lenses
and prisms should be examined, to see that they are clean
and free from dust, and carefully placed in their right
position. A very little experience will enable those using
the instrument to manage the levers and prisms, and, with
facility, to produce all the effects desired. When practi-
cable, an opaque screen should be used, by having the
lantern in front. The best material for a transparent
screen is made from the widest cambric muslin, tightly
stretched on a frame, and, previous to being used, washed
over by a brush with water, to increase its transparency.
To Make the Oxygen Gas. — The process is so easy and
safe, as to render the use of the prismatic lantern in this
respect more convenient than that of the oxy-hydrogen,
where large quantities of both oxygen and hydrogen have
to be made ; and where the gases are united, considerable
danger is incurred. Oxygen gas is not combustible, and
can not, therefore, be attended with danger; it has no
smell, and is the vital principle of the atmosphere. To
make it, it is only necessary — first, to see that the retort
is clean, or, at least, free from coal, oil, or any combusti-
ble substance (after making the gas, a residuum is formed
at bottom of retort, this should always be removed previ-
ous to making fresh gas) ; secondly, put into the retort
(if the gas-bag is empty) eleven ounces of chlorate of po-
tass, and two ounces of black oxide of manganese, in pow-
der, well mixed together ; lute round the cover with putty
or clay ; screw it down tightly, and put it on a common
fire ; and connect the purifier (which should be half filled
with water) with the retort, as shown in wood-cut. If the
fire be tolerably bright, bubbles will soon rise through
the water in the purifier ; when they come fast and regu-
larly, without intermission, allowing all atmospheric air
to be expelled, connect the purifier with the gas-bag by
the flexible tube, and in about ten minutes you will have
three feet of the purest oxygen gas ; when the bubbles

DISSOLVING VIEW INSTRUMENTS.

377

conse, or when the bag is full, lurn the stop-cock, to pre-
vent gas escaping, unscrew the tube from the purifier,
and take the retort off the fire. When required for use,
attach the tube from the gas-bag to the lamp, having
previously removed any moisture that may have collected
in the aperture of the stop-cock in the process of making
the gas, which is easily clone by passing a narrow strip
of linen, or piece of string, through the orifice.

Price, with apparatus for producing the gas, $135.00.

Also, the same lantern with a solar lamp in place of the
oxygen lamp and gas apparatus, by which a brilliant disc
of eight or ten feet may be made much superior to the
ordinary form of dissolving lanterns. Price $120.00.

Fig. 795.

The Trinoptric Lantern.— (Fig. 795.) — This differs

from the Dioptric Lantern by having in addition to the

two tubes with lenses and prisms placed at the sides, one

without a prism placed directly in front of the lantern,

32*

378 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

combining tlie powers of three lanterns in one, with
only one lamp. With the oxygen lamp a disk of twenty
feet may be obtained for each tube, and each disc capable
of being- darkened to any required extent, without the
least shadow on any particular portion of the picture.
The three discs, by means of prisms, may be thrown,
either altogether on one circle, or united, at various dis-
tances in length, on the screen, to form one panoramic
picture. All the various effects that can be produced by
the employment of two or three distinct lanterns, of the
usual form, each requiring a light, are obtained far more
effectively, and with much more facility, by the trinoptric
lantern, which, exclusive of always securing uniform illu-
mination, from the superiority in the optical arrangement
of the apparatus, each picture is perfectly flat, and well
defined to the extreme edge. The lamp is on the foun-
tain principle, with a small circular wick ; a small tube
passes through the centre of the wick, for the purpose of
supplying a stream of oxygen gas, by which an intense
light is produced, nearly equal in illuminating power to
the oxy-hydrogen.

Price, with condensing lenses 3j inches diameter, with
gas-bag and apparatus complete for producing the gas,

$150,00.

Also, the same apparatus with a solar lamp in place of
the oxygen lamp and gas apparatus, by which a disc of
eight or ten feet, or more, may be obtained, much superior
to the usual dissolving lanterns. Price $135.00.

The Prismatic Binoptric Lantern, for Oxy-Hi/drogcn
or Lime-Light. — (Fig. 796.) — The prismatic binoptric
lantern is adapted for the oxy-hydrogen, or lime-light,
condensing lenses 3-| inches diameter, and is the most
complete and effective instrument yet manufactured, capa-
ble of giving one or two brilliant discs to any extent re-
quired, with dissolving effects the most perfect produced
by one lantern and one jet : thus combining excellence in
optical and mechanical arrangements. Apparatus, con-
sisting of the most improved oxy-hydrogen jet and lime-
holder, with clockwork motion, two large gas-bags, with
stop-cocks, flexible tubes, pressure-boards, hydrogen gen-
erator and purifier, iron retort for oxygen, &c.

Price $265.00.

DISSOLVING VIEW INSTRUMENTS.
Fig. 796.

379

With oxy-hydrogen microscope, having three powers,
and several sliders with objects attached, as shown at A,
(fig. 796), additional. Price $110.00.

With polariscope, and apparatus additional, $110.00.

Telegraph Model— (Fig. 797.) — This model represents
the essential parts of Professor Morse's telegraph, con-
sisting of an electro-magnet with the poles upward, hav-
ing the ends of the wires surrounding the magnet connect-
ed to two brass cups with binding screws, which are
fastened to the base on which the instrument is mounted.
A brass roller, or spool, on which the narrow riband of
paper is Avound, and which may be drawn off as required,
passing through an opening or guide in the brass pillar
supporting the lever ; to the end of the lever, and just
over the poles of the electro-magnet, is an armature, or
bar of soft iron, not in contact, but a small distance above

380 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Fig. 797.

the poles of the electro-magnet, and which may by a
slight pressure, or attraction, be put in contact. On the
under side of the the armature is a steel-point. The
electro-magnet, near its poles, supports a brass frame,
having an aperture for the paper freely to pass through,
and so adjusted that when the armature is drawn down,
the paper is indented by the point on the under side. On
connecting the wires from a galvanic battery with the
cups at the side of the instrument, the electro-magnet is
powerfully charged, and the armature drawn down, as
often as connection is made, and broken, by the wire in
the hand of the operator. This wire may be of great
length, communicating as they do, in some cases, between
distant cities. The armature with the pen-point being
brought down, indenting the -paper, which at the same
time is being drawn through the aperture in the frame
between the poles of the electro-magnet. We can con-
nect and disconnect the wires of the battery as often and
as fast as we please, consequently can magnetize the mag-
net, and draw down the armature and point as quick and
as often as we please. If constantly magnetized, the
mark would be a long line ; if momentary, a dot ; a little
longer time, a short line ; so that we may have dots,
spaces and dots, in any number, and lines and spaces of
any length, or any combination of any or all of these
marks, from which an alphabet has been formed, that
may be read with facility by one familiar with its charac-
ters; these different combinations of dots, and of short

NT, \KT1C I] \STI5OlEVrS. 381

and long* lines, with short and long spaces forming the
letters, between which a short space is used, a longer
space between words, and still longer between sentences.

Price $7.50.

Fig. 798.

Magnetic Beam Engine. — (Fig. 798.) — In this simple
arrangement of the beam-engine, there is an electro-mag-
net with its poles upward, securely bolted to a mahogany
base, the magnet being wound with a double coil of in-
sulated copper wire, the ends passing through the base to
the under side, one of them being soldered to one of the
screw cups for connection with the battery. Over the
poles of the electro-magnet is an armature, of soft iron,
which is attached to one end of a walking-beam, support-
ed on a stout vertical brass column, branched at the upper
part for the reception of the beam. At the other end of
the beam, is attached, by a moveable joint, a connecting-
rod, working the crank of a fly-wheel, which is supported
on two brass pillars ; on the axis of the fly-wheel, there is
a silver break-piece, by which the battery current may
be interrupted, and renewed, alternately, by means of a
spring alternately in contact, as the axis moves round,
one end of the spring having contact with the break,
when the armature is to be brought down, but otherwise
free ; the other end of the spring passes through the ma-
hogany base, and is soldered to one of the wires from the
electro-magnet, the break on the axis having contact by

382 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

means of a wire beneath the base, with a screw-cup for
connection with the battery current. The cylindrical pot
battery (Fig. 391) is of sufficient power to work this en-
gine with ease and rapidity, drawing the armature down
to the poles of the magnet with considerable power, being
attracted till it touches them, when the connection is in-
terrupted by the break-piece and spring ; but the momen-
tum of the fly-wheel carries the crank round, and the
armature is raised to be again attracted by renewal of
the contact — the arrangement of the break-piece being
such that the current is interrupted while the armature is
receding, but passes while the armature is drawn down,
producing a continued and rapid motion of the beam and
fly-wheel. Size, 10 inches long, by 8 inches high.

Price $9.00.

• 793- Axial Wheel Engine.— (Fig.

799.) — In this engine two hel-
ices of insulated copper- wire,
at a convenient, distance apart,
are clamped and fastened by
screws to the sides of two
brass pillars, which are fixed
in a neat turned wooden base.
At the top of these pillars
there is an axis, with crank
and fly-wheel, the crank work-
ing a rod, and supporting with-
in the upper part of the hel-
ices a bent rod of soft iron, an
armature of the same shape
and size, entering within the
helices at the lower end, is
fastened to the base of the
instrument. One end of the
wire forming the helices is connected with one of the
screw-cups, on the base of the instrument, for receiving the
battery-current, the other end, of the wire of the helix, be-
ing in connection with a break-piece on the axle of the
fly-wheel, and having a spring acting against it, so that
the battery-current is alternately made and broken by the
spring being in contact, or not ; this spring is connected
by a wire, beneath the base, to the other cup, for the

ASTROXOM I C A L I XSTR UM ENTS.

383

battery-current. The power of a moderate sized pot-
battery, fig. 391, is sufficient for working this engine, the
current of which circulating in these helices, induces mag-
netism in the bent bars, and powerfully attracting them
within the helices ; when, by the revolution of the axle,
the spring is separated from the break-piece, and the cur-
rent stopped, the momentum of the fly-wheel bringing up
the crank, and bent iron rod, again to be attracted and
brought up — thus producing a rapid and uniform motion.

Price $10.00.

Fig. 799*.

J^&*

Improved Magnetic Electric Machine for Medical Application. — (Fig.
799|.) — A, horse-shoe magnet; B, wire coil; C, armature; D, dri-
ving-wheel ; E, pulley-wheel ; G, handle ; H, regulator ; I, conduct-
ors. The electrical current is obtained by turning the handle, which
by means of cog-wheels and a pulley, revolves an armature with a
coil of insulated copper wire on each pole, against a permanent mag-
net. No liquids or acids are required. Whatever part of the body is
affected, to which electricity is to be applied, the conductors may be
moved about each side of the part affected, to distribute the electricity ;
and if covered with a sponge or flannel, and wet, the effect is more
agreeable, and the power increased. They are used in the treatment
of paralysis, rheumatism, nervous, and many other diseases, with
great success. Price $10 00.

384 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Youth's Chemical Cabinet (fig. 800), containing upward
of 62 chemical preparations, tests, and useful apparatus,
without any acid or deleterious or dangerous article.

Fig. 800.

12 SQUARE BOTTLES.

No. 1. Phosphorized Oil.

2. Nitrate of Copper.

3. Solution of Acetate of Co-

balt.

4. Solution of Nitrate of Sil-

ver.
5. Tincture of Galls.

No. 6. Phosphuret of Lime.

7. Sub-carbonate of Potash.

8. Prussiate of Potash.

9. Bichromate of Potash.

10. Sulphate of Iron.

1 1 . Tincture of Litmus.

12. Caustic Potash.

No. 1 . Sulphate of Soda.

2. Stem-bridge Clay.

3. Alum.

No. 1. Steel Filings.

2. Litharge.

3. Gum Arabic.

4. Nitrate of Strontian.

5. Tartaric Acid.

6. Fluate of Lime.

7. Chlorate of Potash.

8. Red Lead.

9. Carbonate of Magnesia.

10. Lycopodium.

11. Powdered Charcoal.

12. Sulphuret of Antimony.

6 LARGE BOXES.

No. 4. Nitrate of Potash.

5. Acetate of Lead.

6. Sulphur.
24 SMALL BOXES.

No. 13. Muriate of Ammonia.

14. Nitrate of Barytes.

15. Bcnzoic Acid.

16. Oxide of Manganese.

17. Oxalate of Ammonia.

18. Logwood.

19. Camphor.

20. Borax.

21. Nitrate of Mercury.

22. Isinglass.

23. Sulphate of Copper.

24. Resin.

APPARATUS, &c.

Earthenware Mortar
and Pestle.
Glass Spirit-Lamp and
Cover.
Metallic Capsule.
Glass Stirring-Rod.
Precipitating Glass.

Turmeric Paper.
Litmus Paper.
Filtering Paper.
Funnel.
Tripod Stand.
Two Crucibles.
Tin-Foil.

Glass Tubing.
Lamp Cotton.
Metallic Zinc.
Sheet Ditto.
Bullets.
French Chalk.
Test-Tube.

WORKING MODEL OF STEAM-ENtilNR.

385

In cardboard case, price $2.50 ; cedar case, $3.50 ;
mahogany case, French polished, with lock and key,
$5.00. Larger cases of chemicals and apparatus at
$10, $15, $20, and $28.

Fig. 801.

fcV- ig>

Working Model of Bt cam-Engine. — (Fig. 801.) — The
above represents a neat and compact model of this in-
teresting machine, sometimes called the "king of ma-
chines," and as an example of a self-regulator is unsur-
passed by any other forms of machinery. The boiler for
the generation of steam is of strong copper or brass, and
is heated by the flame of a spirit-lamp, having a number
of wicks. On the top of the boiler is placed the safety-
valve, with its lever and weight; this valve opens upward,
so that should the elastic force of the steam become too
great, the valve opens and the steam escapes. At one
end of the boiler is a water-cock, and at the other end,
and near the top, a cock and the steam-pipe. This
stearn-pipe connects with the cylinder of the engine, for-
cing a steam-tight piston backward and forward by an
arrangement of sliding valves, so adjusted as alternately
to admit the steam above and below the piston, and also
alternately to let it escape in the air. The working
beam is supported at its fulcrum by a neat and substan-

386 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

rial framework of polished brass, and connects at one end
to the piston-rod, working through a steam-tight stuffing-
box, and attached by an arrangement giving parallel mo-
tion, or so as to move the rod in a right line, although the
end of the working beam moves in the arc of a circle.
To the other end is attached, by a moveable joint, the
connecting-rod, working the crank and fly-wheel, the
revolutions of which give uniformity to the motion of the
engine. On the main shaft, or axis of the fly-wheel,
there is an eccentric-wheel or pulley clasping around it,
the end of a rod which at the other end connects with an
arrangement of levers for moving"the sliding valves. As
the eccentric moves round, it draws the rod backward
and forward, and moving the valves at the proper time,
distributes the steam in the cylinder, thus giving motion
to the whole. The engine is made of brass, well and
neatly finished, and with the boiler, is mounted on a me-
tallic base, handsomely japanned to represent brick-work.
The engine is put in operation by pouring a half pint of
water into the boiler, by the opening at the safety-valve,
and applying the heat of the alcohol lamp, which, without
soiling the brass-work, will cause the engine to work with
great rapidity. Size, 22 inches long, 13 inches high.

Price -$30.00.
Larger size, $50.00.

Common School Apparatus, consisting of Juvenile In-
structor, Numeral Frame, Geometrical Forms, Arithmeti-
cal Solids, Geological Cabinet, Globe, Tellurion, Orrery,
Thermometer, &c., with directions for using each article.

The above have been greatly improved in style, dura-
bility, &c., with many important additions. Out of the
many school-superintendents who have recommended the
above instruments, are a few whose names are subscribed
to the following certificate, who are well known in the
state of New York as competent judges : —

" This is to certify, that after a careful examination of the Scientific
School Apparatus, we can not refrain from expressing our decided
opinion, that its general introduction into our schools is of importance,
and would cheerfully recommend it to the community. The different
departments being well adapted to most of the branches pursued in
our common schools, Avill greatly facilitate the teachers, as well as the
pupils, in the pursuit of those branches it is so eminently calculated
to illustrate."

CO.M.MOX SCHOOL APPARATUS.

387

School-Superintendents ofYates Co.

\i-tr York.
C. S. HOVT, Potter.
R. I. ADAMS, Middlesex.
H. W. LOOMIS, Jerusalem.
C. W. TAYLOR, Benton.
JAMES LAWRENCE, Milo.
School-Superintendents of Chemung
Con

School- Superintendents of Steuben
Counti/, New York.

JOEL FENNO, Tyrone.
E. VANKEUREN, Urbana.
E. S. CHURCH, Bath.
A. B. CASE, Howard.
H. DEPIEW, Thurston.
DAVID 0. MASTER, Hornby.
GEORGE BIDDELL, Canistco.
CYRUS KELLOGG, Painted Post.
LEWIS A. Kxox, Wayne.

School-Superintendents of Onondaga

County, New York.
A. H. WELLS, Pompey.
H. W. NOTES, Otisco.
JABEZ WILDER, Marcellus.
WARREN GOODELL, Lafayette.

nit i/, New York.
JOHN BOSWETII, Chemung.
HIRAM B. NEWCOMB, Starkey.
W. WOODWARD, Big Flats.
B. W. GOLDSMITH, Southport.
School-Superintendents of Madison

County, New York.
A. B. CANFILLD, Cazcnovia.
L. D. DANA, Sullivan.
CHENEY- MORSE, Eaton.

An exhibition of the above-mentioned apparatus, by its
own recommendation, will have more impression upon en-
lightened minds, than the above certificate which is here
presented, for the purpose of securing their attention.
Visible motions of revolving* planets in miniature, will
convince the skeptic that the astronomical department
alone is worth the attention of all. The Tellurion makes
easy and comprehensive to juveniles, the philosophy and
cause of day and night, and their variation in length ;
the changes of the seasons ; phenomena of the moon : its
changing, quartering, fulling, ascending and descending,
passing its nodes, and its different positions at each
change ; the eclipses of the sun and moon ; variation of
the tides; signs of the zodiac, &c. The Orrery repre-
sents the eight primary planets, with their nineteen sat-
ellites or moons, performing their journeys around their
primaries in their flight around the sun. All of which
should be illustrated in every school. They are arranged
in a suitable case, and offered for $16 per set.

Geological Specimens. — No. 1. Quartz. 2. Quartz. 3. Burrstone.
4. Felspar. 5. Miea. 6. Granite. 7. Granite. 8. Gneiss. 9. Mica
Slate. 10. Hornblend. 11. Sienite. 12. Basalt. 13. Lime. 14.
Lime. 15. Serpentine. 16. Talc. 17. Soapstone. 18. Gypsum. 19.
Sandstone. 20. Puddingstone. 21. Coal. 22. Coal. 23. Organic
Remains. 24. Coral. 25. Lava, 26. Calcareous Spar. 27. Fluor
Spar. 28. Iron Pyrites. 29. Spe. Oxide of Iron. 30. Bro. Oxide
of Iron. 31. Galena. 32. Copper Pyrites. — 33. Ponderous Spar.

34. Magnetic Iron. The last two Numbers are substituted when

the whole 32 can not be furnished. In a wooden tray, price $2.00.

38S BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE.

Tables arranged for Baume's Hydrometer t for Syrups,
Sfc., at GO degrees of heat, showing the Specific Gravity,
and the Quantity of Sugar in Pounds and Ounces in
the Wine Gallon of the Syrup.

Degrees
of the

Specific
Gravity.

Quantity of Sugar
per Wine Gallon.
Ibs. 07.

Degrees
ofthe
Instrument

Specific

Gravity.

Quantity ofSufjar
per Wine Gallon.

11)9. OZ.

0

1.000

Water.

25

1.210

4 11

1

1.007

0 21

26

1.221

4 15

2

1.014

0 5

27

1.231

5 2

3

1.022

0 71

28

1.242

5 6

4

1.029

0 10

29

1.252

5 10

5

1.036

0 121

30

1.262

5 14

6

1.044

0 15

31

1.275

6 3

7

1.052

1 2

32

1.286

6 7

8

1.060

1 5

33

1.298

6 12

9

1.067

1 8

34

1.309

7 0

10

1.075

1 101

35

1.321

Saturated Syrup.

11

1.083

1 13

36

1.334

12

1.091

2 0

37

1.346

13

1.100

2 3

38

1.359

14

1.108

2 6

39

1.372

1/5

1.116

2 9

40

1.384

16

1.125

2 12

41

1.398

17

1.134

2 15

42

1.412

18

1.142

3 2

43

1.426

19

1.152

3 5

44

1.440

20

1.161

3 9

45

1.454

21

1.171

3 12

46

1.470

22

1.180

4 0

47

1.486

23

1.190

4 4

• 48

1.501

24

1.199

4 7

49

1.516

25

1.210

4 11

50

1.532

Baume's Hydrometer, or Sacrometer for Syrups, is equally adapted
for acids, leys, and other liquids heavier than water. This instrument
is of all others the one in greatest use ; the scale or numbers on the
stem however are arbitrary, and formed, as most others, after the
ideas of their projectors, and having no particular reference by which
they may be understood. The above table is designed to supply this
deficiency, and fix the value of the numbers in the scale, Thus at
13° the specific gravity is 1.100 or one tenth heavier than water, and
the solution contains 2 pounds 3 ounces of solid matter in the gallon.

Price, in glass, 75 cts. ; extra large, $1 50 ; brass, $4; silver, $6.

Price of Trallis's Hydrometer for Spirits, 10 to 14 inches, $1 ; 14
to 17 inches, $2 50 ; the same with thermometer, $3 50. (See p. 389.)

HYDROMETER TABLES.

389

Table corresponding u-ith Trollies Hydrometer for Spirits,
by Volumes, from 0 to 100. Opposite cadi Volume of
Pure Alcohol is affixed its Specific Gravity, and its Com-
mercial Strength, over and under Proof.

fc
I

|

o
i

1

^.

0)

5

11
I

Hydrometer Degree
in Volumes of
Alcohol.

ftp

i

o

|

to

Percentage Over-
Proof.

1
f

Specific Gravity.

Percentage Under
Proof.

1 Hydrometer Degree
in Volumes o?
Alcohol.

1 Specific Gravity.

! Percentage Under
Proof.

100

.7940

JOO

75

.8765

50

50

9335 0

25

.9700

50

99

.7988

98

74

.8791

48

49

.9354 2

24

.9710

52

98

.80:i4

96

73

.8817

46

48

.9373 4

23

.9720

54

97

.8077

94

72

.8842

44

47

.9391 6

22

.9731

56

96

.8118

92

71

.8867

42

46

.9409 8

21

.9741

58

93

.8157

90

70

.8892

40

45

9427

10

20

.9751

60

94

.8194

88

69

.8917

38

44

.9444

12

19

.9761

62

93

.8230

86

68

.8941

36

43

.9461

14

18

.9771

64

92

.8SJ65

84

67

.8965

34

42

.9478

16

17

.9781

66

91

8299

82

66

.8989

32

41

.9494

18

16

.9791

68

90

.8:i32

80

65

.9013

30

40

.9510

20

15

.9802

70

89

.8365

78

64

.9036

28

39

.9526

22

14

.9812

72

88

.8397

76

63

.9059

26

38

.9541

24

13

.9823

74

87

.8428

74

62

.9082

24

37

.9556

26

12

.9834

76

86

.8458

72

61

.9104

22

36

.9570

28

11

.9845

78

85

.8488

70

60

.9126

20

35

.9583

30

10

.9857

80

84

.8518

68

59

.9148

18

34

.9596

32

9

.9869

82

83

8547

66

58

.9170

16

33

.9609

34

8

.9881

84

82

.8575

64

57

.9192

14

32

.9622

36

7

.9893

86

81

.8603

62

56

.9213

12

31

.9634

38

6

.9906

88

80

8631

60

55

9-J34

10

30

.9646

40

5

.9919

90

79

.8658

58

54

.9258

8

29

.9657

42

4

.9933

92

78

.8685

56

53

.9275

6

28

.9668

44

3

.9947

94

77

.8712

54

52

.9295

«j 4

27

.9679

46

2

.9961

96

76

8739

52

51

.9315

§ 2

26

.9689

48

1

.9976

98

75

.8765

50

50

.9335

£ o

25

.9700

50

0

1.0000

water.

Pure alcohol has a specific gravity of .7940, at 60° heat, and is 100
per cent, over-proof.

75 volumes of pure alcohol, and 25 volumes of water, have a speci-
fic gravity of .8765, or 50 per cent, over-proof.

50 volumes of pure alcohol, and 50 volumes of water, have a speci-
fic gravity of .9335, or proof spirits.

25 volumes of pure alcohol in 75 volumes of water, have a specific
gravity of .9700, or 50 per cent, under proof.

Pure water has a gravity of 1.0000.

At 60 degrees of the thermometer, the ahove tables are perfectly
correct ; but when the temperature is below 60°, an addition must be
made of one volume for every five degrees of the thermometer ; and
when above 603, a like quantity must be deducted, or 2 per cent,
on the commercial strength for every 5 degrees of heat — adding when
below, and deducting when above 60°.

* For the preparation of these tables, the author is indebted to Mr. Robert Ben-
nett, of Cincinnati, Ohio

33*

INDEX TO VOLUME I.

Adhesion plates, 141
Air pumps, 188
Air pump receivers, 200
Air shower, 211
Altitude and azimuth inst. 130
Angle meter, 96

Apparatus for extending the sur-
face, 300
Apple cutter, 202
Architect's scale, 34
Archimedes' screw, 240
Armillaiy sphere, 107
Artificial horizon, 99
Astronomical instruments, 101
Astronomical telescope, 118
Atwood's apparatus, 173
Aurora flask, 291
Aurora tube, 290
Azimuth compass, 54

Balance beam and cork ball, 213

Balance electrometer, 262

Barker's mill, 240

Battery for plating, 334

Beam compasses, 26

Bell in vacuo, 214

Biot's movable hemispheres, 298

Bisecting compasses, 24

Bladder and weights, 208

Bladder glass, 202

Bohnenberger's machine, 142

Bolt head experiment, 203

Bottle electroscope, 305

Bow compasses, 20

Bow compass, universal, 22

Bow pen, 20

Bow pencil, 20

Burnt air, 219

Bursting squares, 220

Capillary attraction, 143
Capstan, 160

Centres for draughtsmen, 26
Centrifugal hoops, 117
Centrifugal pump, 241
Centrolinead, 43
Chime of bells, 273
Chryophorus in vacuo, 218
Circular protractor, 43
Circumferentor, 60
Collision balls, 143
Compasses, 15

Composition of forces, 144 — 158
Condensing apparatus, 198 — 199
Cone and inclined plane, 160
Couronne de Jasse, 324
Crushed bottle, 220
Curves, 40

Cuthbertson's electrometer, 267
Cylinder electrical machines, 252
Cylindrical pot battery, 331

Dancing images, 274

Dancing pith balls, 276

Daniell's battery, 332

Decomposition of water, 340

Dial with cannon, 136

Dipping needle, 97

Directors, 320

Discharger, 261

Diverging threads, 277

Dotting pen, 18

Double-barrel air-pumps, 192 —

194

Double-bodied vessel, 232
Double jar, 301
Drawing compasses, 15
Drawing pen, 16
Drawing squares. 40
Dry pile, 306

Eclipse instrument, 115
Electrical air thermometer, 304
Electrical aura or breeze, 218

392

INDEX TO VOLUME I.

Electrical battery, 269
Electrical bells, 273
Electrical belted bottle, 294
Electrical cannon, 295
Electrical cross, 289
Electrical doubler, 264
Electrical fire-house, 294
Electrical flyers, 280—281
Electrical inclined plane, 282
Electrical induction, 300
Electrical machines, 246
Electrical mortar, 296
Electrical orrery, 282
Electrical pail, 285
Electrical pendulum, 279
Electrical pistol, 296
Electrical plates, 274
Electro plating and gilding, 336
Electrical pyramid, 308
Electrical rope dancer, 284
Electrical saw mill, 287
Electrical see-saw, 278
Electrical spark passed through

' gasses, 304

Electrical spider and jar, 279
Electrical sportsman, 283
Egg stand, 293
Electrical swan, 284
Electrical swing, 278
Electrical vane, 288
Electrical wheel, 207
Electrical wind-mill, 289
Electrophcrus, 258
Endless screw, 159
Engineer's Level, 90
Ether fired by the electrical

spark, 297
Eudiometer, 303
Expanding threads, 277
Expansion fountain, 206

Farraday's bent electrical con-
ductor, 299

Flask for weighing air, 212
Flint and steel in vacuo, 218
Float wheel, 215
Forcing pump, 234
Fountain by elasticity, 221
Fountain in vacuo, 205
Freezing apparatus, 217
French table air pump. 191
Frye's lactometer, 227

fJallows' connector, 201

Galvanic instruments, 324

Gauge, 40

Galvanic battery, old form, 320

Galvanic gas pistol, 342

Globes, 101

Globe quadrant, 106

Gold leaf electrometer, 263

Goniometer, 98

Graphometer, 64

Grove's battery, 337

Guinea and feather apparatus,
207

Gunpowder fired by the electri-
cal spark, 296

Gunpowder fired iti vacuo, 219

Hair compasses. 16
Hand glass, 201
Hare's calori motor, 328
Hare's deflagrator 326
Head of hair, 277
Hourglass, 140

Hydraulic instruments, 224 — 235
Hydro-electrical machine, 321
Hydrometer, 224
Hydrometer with weights, 226
Hydrostatic bellows, 238
Hydrostatic equilibrium, 236
Hydrostatic figures, 230
Hydrostatic instrum's, 224—235
Hydrostatic paradox, 237
Hydrostatic paradox, with pis-
ton, 243
Hydrostatic press, 242

Ignition of charcoal ia chlorine,

298

Impenetrability, 142
Improved lever air-pump, 188
Inclined plane, 148 — 156
Inertia apparatus, 141
Insulated stand, 302
Insulating stool, 260—317

Jar, with discharging electrome-
ter, 308

Land Chain, 49
Level and Plumb, 89
Level for slopes, 96
Levelling staves, 95
Levelling staves, portable, 96
Lever condenser, 200
Levers, 147—154

INDEX TO VOLUME I,

393

Lever and stand for weighing a

column of air, 204
Leyden jar, 260
Lifting pump, 233
Lightning conductors, 308 — 310
Luminous crescent, 292
Luminous discharger, 291
Luminous word, 292
Lungs glass, 206

Magdeburg hemispheres, 203
Magic picture, 271
Mariner's compass, 52
Mathematical instruments, 11
Measuring wheel, 49
Mechanical powers, 145 — 150,

151

Medical electricity, 315
Medical electrical machine, 312
Medical electrometer, 267
Medical jar, 266—318
Mercury shower, 211
Motion, mechanics, &c., 142
Movable coatings, 270

Needle holder, 20
Needle point instrum., 22
Nicholson's balance, 227

Oleometer, 229

Pantagraph, 46

Parallel rule, 36

Perambulator, 49

Phosphorus cup, 286

Pillar compasses, 27

Pins for drawing, 26

Pith ball electrometer, 261

Plain compasses, 15

Plane scale, 28

Plane table, 58

Planetarium, 110

Planetarium improved, 113

Plate electrical machines, 246

Platina point, 310

Plumb and spirit level, 59

Plumb bob, 50

Pocket compasses, 50

Pocket compass, gilt, 52

Pocket sextant, 74

Pocket spirit level, 88

Porous cells, 333

Powder cup, 342

Powder house, 311

Pressure gauge, 222
Pressure glass, 203
Prismatic compass, 56
Proportional compass, 22
Protractor, 28
Pulleys, 146—152

Quadrant, 65

Quadrant electrometer, 262

Radiating feathers, 278
Rain electroscope, 305
Reflecting circle, 75
Reflecting goniometer, 98
Relative weight of fluids, 230
Revolving glass globe, 290
Revolving horsemen, 281
Ring dial, 137
Road pen, 18
Rocking horse, 145
Rolling glass balls, 285
Rotating bell glass, 288

Scales and weights, 224

Screw, 150—157

Screw press, 159

Sector, 32

Series of insulated jars, 302

Set of spirals, 292

Sextant, 69

Single barrel air-pump, 195-197

Sliding rod receiver, 213

Smee's battery, 337

Sphere and point, 298

Spiral and Flyer, 290

Spirit level, 88

Spotted jar, 293

Spouting fluids, 239

Spouting tube, 204

Spiral tube, 291

Spring steel bow dividers, 22

Stand for the fusion of wire, 297

Sulphur cone, 272

Sun dial, 135

Surveyors' compass, 60

Surveyors' compass, small, 63

Survey ors' cross, 60

Surveyors' instruments, 49

Surveying, level, common, 90

Syphon, 231

Tantalus cup, 232
Tape measure, 50
Tellurium, 114

394

INDEX TO VOLUME I.

Theodolite, 80
Theodolite, four sighted, 64
Three globe fountain, 206
Thunder house, 307
Tide dial, 116
Time glass, 140
Torricellian experiment, 215
Torsion balance, 306
Transferrer, 220
Transit instrument, 125
Triangular compass, 24
Trough batteiy, 325
Troughton's level, 93
T square, 38
Tube compass. 26

Universal discharger, 265

Universal joint dial, 139
Upward pressure apparatus, 208
Urinary cabinet, 229
Urinometer, 229

Vacuum gauge, 223

Van Melsen's battery, 331

Volta's condenser, 264

Water Hammer, 221
Water pump in vacuo, 217
Wedge, 148—157
Weight lifter, 208
Wheel and axle, 149
Whirling table, 160—172
Wirtemburg syphon, 232
Woluston's battery, 230

INDEX TO SUPPLEMENT.

Baumc's Sacarometer, 388
Binoptric Magic Lantern, 378
Claude Lorraine Mirror, 373
Common School Apparatus, 386
Camera Lucida, 363
Chemical Cabinet, 384
Dioptric Magic Lantern, 373
Drawing Board, 357
Equatorial Telescope, 366 — 370
Magneto-Electric Machine, 383
Magnetic Beam Engine, 381
Magnetic Axial Engine, 382

Microscope, Compound, 352
Microscope, Achromatic, Ross, 354
Microscope, Nachet's, 359
Microscope, Micrometer for, 363
Microscope, Polarizing Appa., 364
Steam Engine, 385
Stercscope, 372
Telegraph Model, 379
Theodolite, Pike's Improved, 343
Transit Theodolite, 346 — 348
Trallis's Hydrometer, 389

14 DAY USE

RETURN TO DESK FROM WHICH BORROWED

LOAN DEPT.

This book is due on the last date stamped below, or

on the date to which renewed.
Renewed books are subject to immediate recall.

RENEWALS ONLY -

Tel. No.

' ;—

SEP 1 ? 1968

LD 2lA-45m-9,'67
(H5067slO)476B

General Library

University of California

Berkeley

rp

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UNIVERSITY OF CALIFORNIA LIBRARY

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