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Full text of "How to work with the spectroscope : a manual of practical manipulation with spectroscopes of all kinds,"

/fom, Syrwns 



azine 



THE RAINBAND IN SPECTROSCOPE 
OF MODERATE -DISPERSION. 



A aB C D 



E b F 



I 




IUA, 





HOW TO WORK WITH THE 

SPECTROSCOPE. 

A MANUAL 



OF 

PRACTICAL MANIPULATION WITH SPECTROSCOPES 
OF ALL KINDS, 

INCLUDING 

DIRECT- VISION SPECTROSCOPES 

RAIN-BAND SPECTROSCOPES 

CHEMICAL SPECTROSCOPES 

SOLAR SPECTROSCOPES 

STAR SPECTROSCOPES 

AUTOMATIC SPECTROSCOPES 

MICRO SPECTROSCOPES 

SCREEN SPECTROSCOPES 

BESSEMER SPECTROSCOPES 

And Accessory Apparatus. 
WITH ABOVE THIRTY ENGRAVINGS AND DIAGRAMS. 

BY 

JOHN BROWNING, V R .AS V F.R. M.S., M.R.I., &c. 



JOHN BROWNING, 

63, STRAND, LONDON, W.C, 



PRICE ONE SHILLING AND SIXPENCE. 




Entered at Stationers' Hall. All Rights Reserved. 




LONDON : 
W. J. JOHXbON, PBDJTEB 121, FLEET STEEXl 



INDEX. 



PAGE 

How to Work with a Spectroscope 7 

The Miniature Spectroscope 7 

The Rain -band Spectroscope 8 

How to Use a Direct- Vision Spectroscope 12 

Browning's New Miniature Spectroscope, with Micrometer 12 

The Student's Spectroscope ... ... .. ... ... 1 3 

The Model Spectroscope H 

How to Use the Student's, the Model, and the Chemical Spectroscope 14 

How to Obtain the Bright Lines in the Spectrum given by any Substance ... 14 

To Take the Refractive Index or Dispersive Power 17 

Browning's Universal Automatic Spectroscope 18 

How to Use an Automatic Spectroscope 21 

Browning's Automatic Solar Spectroscope 22 

How to Use a Solar Spectroscope 2 3 

The Star Spectroscope 2 4 

The Amateur's Star Spectroscope 24 

How to Use a Star Spectroscope 25 

McClean's New Star Spectroscope 26 

How to Use McClean's Star Spectroscope 27 

How to Use McClean's Universal Spectroscope 28 

The Induction Coil 29 

Browning's Spark Condenser 3 

How to Use Browning's Spark Condenser ... ... ... ... 3 1 

How to Obtain the Spectra of the Metals 3 2 

How to Use Becquerel's Apparatus 3 2 

Lockyer's Revolving Spark Apparatus 33 

Bessemer Spectroscopes 33 

How to Use a Bessemer Spectroscope 35 

The Small Automatic Electric Lamp , 3 6 



237495 



INDEX (continued). 

PAGE 

How to Use the Small Automatic Lamp 37 

Browning's Large Electric Lamps or Regulators 38 

How to Use Browning's Large Automatic Lamp .. ... ... 39 

Instructions for Charging the Battery 39 

Sets of Apparatus for Producing the Electric Light 4 

Spectrum Apparatus for Screen Experiments ... 40 

Screen Spectrum Apparatus ... ... 41 

How to Show Spectra on a Screen - 43 

Spectrum Apparatus for the Microscope 45 

How to Use the Micro-Spectroscope 46 

Objects for the Micro- Spectroscope ... ... ... ... ... 49 

How to Make a Map of a Spectrum with a Student's Spectroscope 50 

How to Map a Spectrum with Beckley's Spectrosraph 50 

How to Map a Spectrum with Colonel Campbell's Spectrograph 51 

How to Map a Spectrum with the Automatic Spectroscope 51 

How to Map a Spectrum of Absorption Bands with a Micro-Spectroscope ... 51 

Works on Spectrum Analysis 55 

List of Prices of Spectroscopes 56 



PREFACE. 



FOR many years I have had almost daily to reply to inquiries 
respecting the best method of manipulating with various kinds 
of Spectroscopes. 

It had been suggested to me long since, by our highest 
authority on the subject, that I should write a small work 
giving the required information. For reasons which will be 
understood by my friends, I had a great objection to issue 
such a work, and trusted it would be done by some of the 
leading scientific men who have worked in this direction. But 
recently the inquiries for information have been more and more 
numerous, and I am compelled, both to save my own time 
and to assist my numerous correspondents, to attempt to supply 
what appears to be an evident want. 

Mr. Proctor's admirable little Manual on the Work of the 
Spectroscope will be found invaluable by those who do not wish 
to incur the expense of Roscoe's or Schellen's works on Spectrum 
Analysis. But Mr. Proctor states that it did not enter into his 
plans to give detailed instructions for the use of the various 
kinds of Spectroscopic Apparatus. 

I have, therefore, endeavoured to supply such information 
in the following Pamphlet. The fact that a List of Prices is 
appended of the various Instruments which are described, will 
not, I hope, be considered to detract from its value. My exten- 
sive correspondence leads me to conclude that such information 
is exceedingly welcome to all those who think of making any 
experiments for themselves. Once provided with Apparatus, 
the experimentalist should obtain a copy of Mr. Proctor's book 
before alluded to, or of Roscoe's or Schellen's larger works on 



the subject. Mr. Lockyer's small work on the Spectroscope 
contains detailed information on the method of working with 
the Induction Coil, and observing solar prominences. 

JOHN BROWNING. 



PREFACE TO THE SECOND EDITION. 

THIS little book has been out of print several months. I 
intended to re-write it and make many additions to the con- 
tents, but as I cannot find time to do this, and as I have 
applications daily for the work, I have only added the par- 
ticulars as to the Rain-band Spectroscope and Mr. Rand 
Capron's diagram of Rain-band Spectra, which I have had 
printed in colours. In this condition I trust it may be useful. 

December, 1882. JOHN BROWNING. 



SPECTROSCOPES AND SPECTRUM APPARATUS. 



HOW TO WORK WITH A SPECTROSCOPE. 

First see that the edges of the slit are free from dust* Direct 
the slit of the instrument towards the sun, the sky, or some 
bright light. If there are any horizontal lines visible that is, 
lines running parallel with the spectrum they are almost sure 
to be produced by dust. To remove this dust, open the slit as 
widely as possible, and wipe the edges of the slit with a small 
wedge of dry wood. Then close the slit completely ; re-open it, 
and the lines will probably have disappeared ; if not, repeat the 
operation. Note that a camel-hair pencil, a leather, cloth, or 
paper will be sure to make the slit worse. 

Place the slit as close to the source of light as you can 
without injuring it. 

THE MINIATURE SPECTROSCOPE. 




This instrument will show many of Fraunhofer's lines, the 
bright lines of the metals and gases, and the absorption bands 
in coloured gases, crystals, or liquids. 

The Miniature Spectroscope consists of a compound direct- 
vision prism, which is placed in a sliding drawer. At the end 
of this drawer there is a lens ; in the best instruments this is an 
achromatic combination. At the opposite end to the eye-piece 
there is a slit, which, in the instruments of a superior class, is 
adjustable by a screw motion. The two jaws move equably 
from the centre, on rotating the milled ring between the thumb 
and finger. The jaws of this slit will require to be almost 
closed to view the Fraunhofer lines, but may with advantage be 
opened wider when viewing the lines of chemical spectra, or 
absorption bands in coloured liquids. 



8 
HOW TO USE THE RAIN-BAND SPECTROSCOPE. 




rig. 2. 

For several years past the prediction of the weather 
received constantly increasing attention. This makes the in- 
troduction of any new method of forecasting the weather of 
great importance. To nearly every person in the community 
a means of telling in the morning whether the day will be fine- 
or wet is of considerable value. To farmers and many others 
whose work goes on exclusively in the open air the power of pre- 
dicting this is of still greater consequence. The barometer will 
frequently rise for hours, and yet rain come on and continue 
falling. As a means of predicting coming rain, no instrument 
has been introduced which equals the Rain-band Spectroscope. 

To use the Rain-band Spectroscope, close the jaws of the 
slit as closely as possible without making them touch. This is 
done by turning the second milled ring on the smaller end of 
the Spectroscope. If shut too closely that is, the jaws are 
made to touch strong black lines will appear parallel to the 
spectrum. Should this be the case, the milled ring must be 
turned very slightly in the opposite direction until the horizontal 
lines disappear. 

The rain-bands are like the Fraunhofer's lines, at right 
angles to the spectrum ; but instead of being sharply defined, 
they are simply shaded bands, which become darker as rain 
becomes imminent. When they are very prominent, they are 
more conspicuous than any of the Fraunhofer lines. 

The diagram by Mr. Rand Capron shows the rain-bands in 
the spectrum of six different degrees of intensity. In looking 
for the rain-bands, direct the instrument towards a bright part of 
the sky, at about an angle of 20 (twenty degrees) above the 
horizon. Mr. Rand Capron, F.R.A.S., in his well-known 
pamphlet, " A Plea for the Rain-band," gives the following 
instructions for observing wirh the Spectroscope : 

" For ordinary meteorological purposes, and to observe the 
general character of the band near D, a pocket or miniature 
instrument is quite sufficient indeed, best adapted. This may be 
obtained from any scientific optician, and will cost, according 
to construction, from one to three guineas. The more expensive 



ones have an adjustable slit and achromatic lenses ; but these 
are not necessities, and the cheaper form is nearly as useful. 

" Having obtained the Spectroscope, close the slit and adjust 
the focus till the lines in the spectrum are sharp and clear. 
This should be done on a bright part of the sky. Then point 
the instrument to the quarter of the heavens which it is desired 
to examine, and note results as to, especially, lines D and their 
neighbourhood. 

" I generally observe thus at 9 a.m. daily from my laboratory 
window (looking towards the south), but if time and opportunity 
allow three observations, at 9 a.m., I p.m., and 5 p.m. would be 
better, varying the parts of the sky tested ; and I examine with 
the Spectroscope elevated about 13 degrees. Professor Smyth 
recommends to point as low as you can to the horizon, provided 
you get transmitted light, and to observe when the sun is 
neither high nor low. I find in practice 9 a.m. (the same hour 
when my other instruments are observed) a good time to make 
the observation when only a single one is taken daily, and also 
that if I get too low on the horizon I am apt to have always a 
' rain-band/ or rather a false band due to earth moisture. In 
observing you will soon remark changes in the characters of 
some of the spectrum lines as compared with these when seen 
on a blue sky with an elevated Spectroscope, and, moreover, 
bands of varying intensity are found added to the low spectrum 
not seen in the higher one. The lines and bands that change 
their character, or are variable in their appearing, are telluric ; 
either rain-bands or lines, called by Professor Smyth ' a function 
of moisture and temperature/ or low sun-bands and lines, 
distinguished by him as ' a function of dry air and low 
sun/ The true solar lines remain unchanged. Professor 
Smyth, in the Edinburgh volume before referred to, fully 
describes both in type and by illustrative drawings all these 
bands and lines, and their changes, and points out that there 
are several smaller rain-bands besides that near D. In practice 
it will, however, be found sufficient for meteorological observa- 
tions generally to examine the principal one on the red, or, if 
you have the spectrum as I do (with the red end of the spectrum 
to my left hand), left side of D. An examination of the other 
lines, though desirable for special purposes, will only tend to 
confuse the general observer. Professor Smyth recommends, 
and has used, a dry air band on the right-hand side of D as a 
standard of comparison with the rain-band ; but I have not 
often myself made use of it, judging independently by the 
rain-band itself. 



10 

" In enumeration of the darkness of the band, for the purpose 
of record, I use from No. I to 5 as under : 



I means faint. 



4 means moderate to strong. 

5 strong. 



2 faint to moderate. 

3 moderate. 

I to 10 is the enumeration recommended and employed by 
Professor Smyth. I found, however, the dividing into so many 
degrees was difficult, especially when the intensity is slightly 
changing by passing clouds. Simultaneous observations should, 
of course, be made and recorded of barometer, wet and dry 
bulbs, and wind (force and direction) ; and the circumstances 
of sun, sky, and cloud at the time should be shortly noted. 

" Ozone test papers may also be usefully referred to, as cold 
winds alike affect them and rain-band readings. The n lines 
arc generally more or less involved in the rain-band shadi 

" To enable the observer to judge of the general appear 
and intensity of the larger rain-band near D, I have given - 
frontispiece) some drawings of spectra as seen in a Spectroscope 
of small dispersion, of which the following is a description : 

" (i) Spectrum as seen upon a pure high sky, showing principal 
solar and telluric lines in their proper positions, and with their 
designations, but not showing the finer lines between, nor any 
bands. 

" (2) Spectrum observed January I7th, 1881, 8 a.m. Morning 
dull ; red sunrise ; low sun-bands and lines (note especially band 
to right of D) strong. No rain-band. 

" (3) Spectrum observed 24th August, 1881, 8 a.m., showing 
moderate low sun-bands and lines, and a faint rain-band, with 
rain-lines showing through. 

"(4) Spectrum seen November i6th, 1880, i p.m. Rain and 
wind, but clearing in some parts of the sky. Low sun-bands 
and lines weak. Rain-band moderate. 

" (5) Spectrum seen December gth, 1880, 8 a.m. Sun shining 
through watery clouds ; low sun-lines strong. Rain-band strong. 

"(6) Spectrum seen July 6th, 1881. Rain-band everywhere, 
and exceptionally strong, stretching nearly half way between c 
and D. Whole spectrum darkened and obscured. 

"The above-described drawings do not give, except in a 
rough way, the details of the lines and bands other than the 
rain-band, which is situate to the left of the double line D, and 
has its place marked by R. 

NOTE. Observe only the dark band marked Rain-band in the coloured frontispiece. This can 
always be found by holding a lighted lucifer match in front of the Spectroscope, when a bright yellow 
line will be seen just where the Rain-band should be looked for. J. B. 



II 

"Spectra 2, 3, 4, and 5 are meant for observing by, as repre- 
senting 2, none ; 3, faint ; 4, moderate ; and 5, strong. Rain- 
band faint to moderate, and moderate to strong (the intermediate 
intensities), can be estimated, and in practice the eye and 
judgment will soon be found to accommodate themselves to the 
graduations i to 5."* 

A valued correspondent in the North-west of Scotland 
writes to me : 

4< I am feeling more and more confidence from day to day 
in the Rain-band Spectroscope. The Aneroid Barometer has 
been falling for days ; the sky has been dull and gloomy, looking 
exactly like wet ; but there has been no rain-band and no rain. 
When I left home this afternoon, at 4 p.m., the rain-band was 
just appearing, nebulous and hazy, and I expect there will be 
rain to-night." 

My correspondent wrote me by the next post that rain fell 
smartly within a few hours. 

Mr. F. W. Cory, F.M.S., ot Buckhurst Hill, Essex, who has 
made rain-band observations for three months, writes as follows 
to Knowledge : 

" i. Adjust the focus and slit of the Spectroscope so that the 
lines in the spectrum maybe of the clearest definition, and whilst 
taking an observation, shade the eyes with the hands, in order 
that all extraneous light may be excluded as much as possible. 

" 2. Observe in a general way from ten to twenty degrees 
above the horizon, and towards the quarter from which the wind 
is blowing ; but if the latter be not practicable, point the instru- 
ment in a northerly, in preference to a southerly, direction. 

" 3. If 80 per cent, of the dark band be shown at the zenith, 
heavy rain will certainly occur before long, 

" 4. During wet weather, the amount of rain-band may be 
low ; this for the most part denotes fine weather to follow. 

"5. If the instrument be directed towards the point from 
which the wind is blowing, and should the clouds be passing in 
one and the same direction, and 20 per cent., or less, of the 
rain-band be shown, no rain will follow for at least six hours, in 
spite of any threatening appearance of the sky. 

" 6. With a knowledge of the course and peculiar charac- 
teristic of storms, which is not difficult to acquire (vide ' Aids to 
the Study and Forecast of Weather,' by W. Clement Sey, 
M.A.), it is possible to foretell rain by the help of the Spectro- 
scope with surprising accuracy. 

* Mr. Rand Capron's Pamphlet, " A Plea for the Rain-band," will be sent to any address for 
four stamps. 



12 



" Observers will not be disappointed if the above suggestions 
are carefully attended to. The principal difficulty lies in de- 
termining the percentage of rain-band ; but this is to be overcome 
by practice and experience, and they will find that after a time 
the indications of the Spectroscope can be read at a glance of 
a few seconds in duration." 

HOW TO USE A DIRECT-VISION SPECTROSCOPE. 




From their simplicity of construction, these instruments arc 
the easiest to use, and are therefore the best adapted for be- 
ginners. In using them, it is only necessary to direct the slit 
to the source of light, which should not be a bright coal-gas or 
lamp flame, as they will not give any lines. A tallow candle, 
with a long snuff, will give the yellow or orange sodium line. 
Coal-gas, burnt in a Bunsen's burner, will give carbon lines. 
A small quantity of a salt of an alkali or alkaline earth fused 
on a wire and held in the flame of the Bunsen's burner, will give 
bright lines. (See " How to Obtain the Bright Lines given by 
any Substance.") Having by either of these methods obtained 
some bright lines, focus them carefully by moving the sliding 
drawer-tube of the telescope, and then close the jaws of the slit 
until the lines appear fine without becoming indistinct. 

Any form of stand, with a ring, tube, or a clip to hold the 
body of the Spectroscope, provided with horizontal, or, better 
still, with horizontal and vertical motions, greatly facilitates the 
use of the instrument. 

These instructions will apply to the Miniature Spectroscope. 

BROWNING'S NEW MINIATURE SPECTROSCOI'K. 
WITH MICROMETER. 





Fig- 3- 

This portable and complete instrument may be used for 
showing any of the leading experiments in spectrum analysis ; 
the Fraunhofer lines ; the lines in the spectra of the metals, and 



13 

the alkaline earths and alkalies ; the spectra of gases ; and 
absorption bands. 

Applied to a telescope, it may be used for viewing the lines 
of the solar prominences. It can also be used as a Micro- 
Spectroscope. The position of the bands in any spectrum may 
be seen at a glance, as a photographed Micrometer scale is 
reflected, by means of a magnifying prism, into the field of 
view, so that it appears parallel with the spectrum. Each 
tenth line on the scale has a figure above it. This instrument 
is very convenient for taking the position of a line rapidly. 

. THE STUDENT'S SPECTROSCOPE. 

This instrument has a prism of extremely dense glass of 
superior workmanship. The circle is divided, and reads with a 
vernier, thus dispensing with an illuminated scale ; this arrange- 
ment possesses the very great advantage of giving angular 
measures in place of a perfectly arbitrary scale. 

The slit is also furnished with a reflecting prism, by means 
of which two spectra can be shown in the field of view at the 
same time. 

The instrument is so arranged that, with a slight alteration 
of the adjustments, it can be used for taking the refractive and 
dispersive powers of solids or liquids. For information on this 
point see separate heading. 

A photographed Micrometer can be applied to this instru- 
ment. 




Fig- 5- 

The instructions for using the Spectroscopes with two to five 
prisms, which follow, will also apply to this instrument. 



THE MODEL SPECTROSCOPE. 




This instrument has two dense glass prisms, two eye-pieces, 
rack motion to telescope, and tangent screw motion to vernier. 
It will widely separate the D lines. 

A photographed Micrometer can be applied to this instru- 
ment. 

HOW TO USE THE STUDENT'S, THE MODEL, OR 
THE CHEMICAL SPECTROSCOPE. 

Screw the telescope carrying the knife edges at the small 
end into the upright ring fixed on to the divided circle, and the 
other telescope into the ring attached to the movable index. 
Now place any common bright light exactly in front of the 
knife edges, and while looking through the telescope on the 
movable index (having first unscrewed the clamping screw 
under the circle), turn the telescope with the index round the 
circle until a bright and continuous spectrum is visible. 

HOW TO OBTAIN THE BRIGHT LINES IN THE 
SPECTRUM GIVEN BY ANY SUBSTANCE. 

Remove the bright flame from the front of the knife edges 
and substitute in its place the flame of a common spirit-lamp, 
or, still better, a gas jet known as a Bunsen's Burner. In the 
Burner shown in the engraving, there is a ring at the bottom of 



the tube, with four apertures ; by turning these, so that the 
holes are closed, the Burner gives a white light, well adapted 
for adjusting the instrument, and showing a continuous bright 
spectrum in the field of view. When this has been done, 
turning the ring so as to make the apertures correspond, will 
admit a quantity of air, and give a dull bluish, very hot flame, 
well adapted for spectrum analysis. Having obtained this hot 
flame, take a piece of platinum wire, about the substance of a 
fine sewing needle ; bend the end into a small loop about the 
eighth of an inch in diameter; fuse a small bead of the substance 
or salt to be experimented on into the loop of the platinum wire, 
and attaching it to any sort of light stand or support (as Fig. 28), 
bring the bead into the front edge of the flame, a little below 
the level of the knife edges. If the flame be opposite the knife 




; 



Fig. 28. 

Improved Spectroscope Lamp, containing Burner and Clip, on a Single Stand. 

edges on looking through the eye-piece of the telescope, the 
fixed lines due to the substance will be plainly visible. When 
minute quantities have to be examined, the substance should be 
dissolved, and a drop of the solution, instead of a solid bead, be 
used on the platinum wire. The chlorides of the alkaline earths 
are the best adapted for giving the spectra as chloride of cal- 
cium, chloride of barium, &c. ; but carbonate of soda and ferro- 
cyanide of potassium give better results than the chlorides of 
these alkalies. 

Whatever salts are used, they must be///r<?, as the salts of 
commerce contain many impurities, and the spectra of these 
impurities are sufficiently bright to mask the spectra of the 
substance themselves. 



i6 

Where coal-gas is not obtainable, a small flame of hydrogen 
may be used. This should be made in an apparatus in which 
it is generated only while it is being consumed. The flame of 
a spirit-lamp may be used, but the results are unsatisfactory. 
The oxy-hydrogen blowpipe is the best of all the sources of 
heat known for this purpose ; but when the bright lines of the 
metals are required, the Induction Coil must be used as described 
under a separate heading. 

When it is desired to show the spectrum of a salt for any 
length of time, small pieces of pumice-stone may be soaked in 
a saturated solution of the salt, and then attached to a. fine 
platinum wire, and held in the flame as described for a bead. 

A frequent source of failure is using a platinum wire too 
thick for the purpose. The wire should be only just thick 
enough to support the substance without a tendency to vibra- 
tion. 

The delicacy of this method of analysis is very great. Swan 
found in 1857 (Ed. Phill. Trans., vol. xxi., p. 411) that the lines 
of sodium are visible when a quantity of solution is employed 
which does not contain more than Tryooooo of a grain of 
sodium. 

To view Fraunhofer's lines in the solar spectrum, it is only 
necessary to turn the knife edges towards a white cloud, and 
make the slit formed by the knife edges very narrow by turning 
the screw at the side of them. In every instance the focus of 
the telescope must be adjusted in the ordinary way, by sliding 
the draw-tube until it suits the observer's sight, and distinct 
vision is obtained. 

It should be noted that lines at various parts of the spectrum 
require a different adjustment in focussing the telescope. 




The small prism, turning on a joint in front of the knife 
edges, is for the purpose of showing two spectra in the field of 
view at the same time. To do this, it must be brought close to 
the front of the knife edges. Then one flame must be placed in 
the position in which the flame of the candle is shown in the 



small diagram figure, and the other directly in front of the slit. 
On looking through the telescope as before described, the 
spectra due to the two substances will be seen one above the 
other. A known substance should be burnt in the flame, to 
give one of these spectra, and a material suspected of containing 
the substance in the other, to see if the lines in the two spectra 
coincide. This is termed working by comparison, and is the 
best method of employing the instrument for analytical purposes. 
When the slit is turned towards a bright cloud, and a light is 
used in the position of the candle flame, the spectrum of any 
substance may be seen, compared with the solar spectrum. In 
this manner Kirchoff determined in the solar spectrum the 
presence of the lines of the greater number of the elements 
which are believed to exist in the sun. The absorption bands 
in spectra may be most conveniently examined, and accurately 
investigated, by means of the SORBY-BROWNING Micro-Spec- 
troscope. 

TO TAKE THE REFRACTIVE INDEX OR DIS- 
PERSIVE POWER OF ANY SUBSTANCE OR 
LIQUID WITH A SPECTROSCOPE. 

A Model or Student's Spectroscope with one or two prisms 
should be used for this purpose. First remove the prism or 
prisms from the Spectroscope ; bring the telescope in a direct 
line with the collimator ; place a positive eye-piece in the 
Spectroscope,, having cross-wires in the field of view ; make 
these cross-wires bisect the slit. The substance of which the 
refractive index is to be determined should be cut into the form 
of a prism of 60. Having noted the reading of the telescope 
on the arc of the Spectroscope, which for this purpose should be 
divided to degrees and minutes, place the prism and the sub- 
stance on the plate of the Spectroscope, at the minimum angle 
of deviation that is, at the angle at which the ray from the 
collimator is deflected the least. If the solar spectrum be now 
observed through the telescope and prism, the position of the 
principal Fraunhofer lines may be read off on the divided arc 
by bringing them successively to coincide with the cross-wires 
in the eye-piece. The method of calculating the index of 
refraction and the dispersive power from these observations, 
will be found very clearly stated in Ganot's " Physics." 

When a liquid has to be employed instead of a solid, a 
hollow prism must be used for containing it. This prism should 
have glass sides, which can be easily removed for the purpose 



i8 



of cleansing them after each experiment. When in use, 
prism and the sides are placed together in a metal frame 
screw in one side of this frame secures them in position, 
confines the liquid. 

Glass prisms can be made so accurately that the sides, wl 
placed against the prism, will be kept in position by atn 
spheric pressure ; but they are seldom employed on account 
their great cost. 

BROWNING'S UNIVERSAL AUTOMATIC 
SPECTROSCOPE. 




In this instrument the prisms are automatically adjusted 
the minimum angle of deviation for the particular ray un< 
examination ; the position of the lines in the spectra 
changed by means of a screw ; the revolution of this scr 
adjusts the prisms automatically for the ray under measu 
ment. The instrument has six prisms, and by means 
the reversion of the ray a dispersive power of twelve pris 
is obtained. By changing the position of one of the prisms, a 
dispersive power, from two to twelve prisms, can be used 



leasure, without deranging any of the adjustments of the 
[strument. This Spectroscope is therefore applicable to every 
ass of spectrum work either in the laboratory or observatory. 




iagram showing the Automatic Action by which the Prisms are automatically adjusted 
to the minimum angle of deviation for the particular Ray under examination. 

In an ordinary Spectroscope the prisms are usually adjusted 
the minimum angle of deviation for the most luminous rays 
the spectrum by preference, I adjust them myself for the 
y E in the solar spectrum. This being done, the prisms are 
rewed, or otherwise firmly clamped, to the main plate of the 
>ectroscope. Thus adjusted, they are liable to two sources of 
ror, one of which places the observer at a serious disadvantage, 
rst, only the particular ray for which the prisms have been 
justed is seen under the most favourable circumstances, for 
ly this ray passes, as all should do, through the train of 
isms parallel to the base of each prism. Of more importance 
an this, however, is the fact that the last prism of the train 
ing fixed while the telescope through which the spectrum is 
iwed is movable around an arc, it is only when the central 
rtion of the spectrum is being examined that the whole field 
the object-glass is filled. 
Bunsen and Kirchoff, when making their celebrated map 



2O 

of the rolar spectrum, adjusted the prisms they used (four 
number) for each of the principal Fraunhofer lines ; but t 
trouble of doing this is so great that few observers have ev 
seen the extreme portions of the solar spectrum under favoi 
able circumstances. 

The diagram (Fig. 8) shows the method in which the chan 
in the adjustment of the prisms to the minimum angle of devi 
tion for each particular ray can be made automatically. In tl 
diagram there are six prisms. All these prisms, with t 
exception of the first, are unattached to the plate on which th 
stand. The first prism is attached by one corner to the pic 
by a pivot on which it turns. The triangular plates on whi 
the prisms rest are hinged together at the angles correspond!: 
to those at the basis of the prisms. To each of these bases 
attached a bar, perpendicular to the base of the prism. As 
these bars are slotted and run on a common centre, the prisi 
are brought into a circle. This central pivot is attached to 
dovetailed slide about two inches in length, placed on the unc 
side of the main plate of the Spectroscope, which is slotted 
allow it to pass through. On moving the central pivot, t 
whole of the prisms are moved, each to a different amount 
proportion to its distance in the train from the first or fix 
prism, on which the light from the slit falls after passing throu 
the collimator, C. Thus, supposing the first prism of the tn 
of C, represented in the diagram, to be stationary, and t 
second prism to have been moved through i by this arran^ 
ment, then the third prism will have been moved throu 
2, the fourth through 3, the fifth through 4, and the six 
through 5. 

A screw gives motion to a lever which is attached to the 1; 
prism of the train. By turning this screw until any particu 
portion of the spectrum appears in the field of view, the ra 
which issue from the centre of the last prism are made to f 
perpendicularly upon the centre of the object-glass of the te 
scope, T, and thus the ray of light under examination trav 
parallel to the bases of the several prisms, and ultimately alo 
the optical axis of the telescope itself, and thereby the wh< 
field of the object-glass is filled with light 

Thus the apparatus is so arranged that, on turning the scr 
so as to make a line in the spectrum coincide with the cross-wi: 
in the eye-piece of the telescope, the lever L, attached to t 
prisms, sets the whole of the prisms in motion, and adju 
them to the minimum angle of deviation for that portion of t 
spectrum. 



21 

Fig. 8* 



RED 



VIOLET 




VICLJTT 



Fig. 8**. 

Diagrams 8* and 8** represent the appearances presented 
ooking through the telescope from which the glasses have been 
emoved. In diagram 8* it will be seen that the whole circle of 
Jie object-glass is filled with light, as I have just described is 
Jie case with the new arrangement ; while diagram 8** shows 
:he effect of moving the telescope through the angle in front of 
:he fixed prism. 

Here, in the red and violet, wliere tJie light in tlie spectrum is 
faintest, only about one quarter of the field of view is illu- 
minated. 



HOW TO USE AN AUTOMATIC SPECTROSCOPE. 

Although this Spectroscope is the most powerful, and in 
appearance the most complex made, it is very easy to use. 

To vary the dispersive power of the instrument, let us suppose 
that the movable right-angled reflecting prism, which reverses 
the ray, is at the end of the train that is, the farthest from the 
collimator. Remove any prism of the battery from its place in 
the train by sliding it with its holder out of the groove. Take 
out the reflecting prism in the same way, and slide it into the 
groove previously occupied by the reflecting prism. In this 
way the dispersive power of one prism, or of the whole train of 
prisms, may be employed at pleasure. 

The subsequent manipulation will be the same as described 
under the heading, " How to Use a Chemical Spectroscope," with 
the exception of mapping the spectra. The method of doing 
this I have described under the heading, " How to Map a 
Spectrum with the Automatic Spectroscope." 



22 



BROWNING'S AUTOMATIC SOLAR SPECTROSCOP 




Dr. Henry Draper's important discovery of the presence 
oxygen in the sun, described in Nature, No. 409, August 3 
1877, will direct renewed attention to the solar spectrum. 

The Automatic Solar Spectroscope, figured above, will sho 
the solar spectrum with exquisite definition, and if attached i 




Fig. 10. 



23 

the eye-piece of a telescope of three inches or more in diameter, 
it will show the forms of the solar prominences. 

As this Spectroscope can be used with any dispersive power 
from two to ten prisms, it can be arranged for observing the 
spectra of the stars and nebulae. Without a telescope it can be 
employed for any kind of work in spectrum analysis. 

By means of the reversion of the ray this Spectroscope gives 
a dispersive power equal to ten prisms, and this dispersive power 
may be changed at pleasure by the observer. The instrument 
is very light, and can be adapted to a telescope as small as 
three inches in aperture. It is provided with a movement 
of rotation for searching for solar prominences. 

The Solar Automatic Spectroscope (Fig. 10) is well adapted 
for use with any telescope, either a reflector or refractor, from 
six to twelve inches in aperture ; and it can be used on a table 
stand, as shown in the engraving, for viewing the spectra of 
metals, salts, or gases. 

HOW TO USE A SOLAR SPECTROSCOPE. 

This instrument must be used with an astronomical telescope. 
No eye-pieces must be used with the telescope. The first point 
to attend to in using a Solar Spectroscope is to place the slit or 
knife edges of the instrument exactly in the focus of the object- 
jlass or speculum of the telescope. 

This must be done by projecting the image of the sun on a 
:ard without any eye-piece in the telescope. Note the distance 
Tom the end of the telescope, not the end of the sliding drawer, 
it which a sharp image is produced. Then attach the Spectro- 
scope to the telescope, and move the sliding drawer until the slit 
s at the required distance from the end of the telescope. The 
3est Solar Spectroscopes are so contrived that the face of the 
jlit can be seen when they are in the telescope. In this case a 
:ard may be placed on the face of the slit, and the drawer tube 
)f the telescope moved until the sun's image is seen sharply in 
bcus, when the card may be removed. 

Now close the jaws of the slit, and move the telescope, so 
hat the sun's limb or edge of the disc falls across the slit at 
ight angles to the direction of the slit. Turn the Spectroscope 
ound, so that every point of the sun's disc passes over the slit 
vhile looking through the instrument. If at the time of making 
he observation there are any prominences on the sun, a faint red 
ine, and possibly a blue and a green line, will also be visible on 



looking into the Spectroscope. These lines will appear bright 
than the other parts of the solar spectrum. 

Having obtained the red line, bring it to the centre of t' 
field of view, and carefully open the jaws of the slit whi 
looking at the red line. 

If the prominence should be of a well-marked character, i 
form will then be seen. The problem, when using the Spectr 
scope, is to get a small bright image into a very narrow slit, 
consequence of their large aperture and short focal lengt 
the new Silvered Glass Reflecting Telescopes are admirat 
adapted for working with the Spectroscope. 

THE STAR SPECTROSCOPE, 




Fig. 12. 

This Spectroscope, which can be made with 
either one or two prisms, is similar in construc- 
tion to that used by Dr. Huggins in his im- 
portant researches on the spectra of the stars. 

An insulated spark apparatus can be attached 
and the light reflected by a mirror into the prism 
in front of the slit, for obtaining the spectra of 
the metals for comparison, to either of the above 
instruments. 

THE AMATEUR'S STAR SPECTROSCOPE. 

This is a Direct-Vision Spectroscope, and is very easy to i: 
with an equatorial provided with a clock ; but the new Medea: 
Star Spectroscope has the great advantage that it can be us 
on any alt-azimuth stand with the greatest facility. 




Section of Brownings Amateur's Star Spectroscope. 

A is a compound direct-vision prism, consisting of five 
prisms. B is an achromatic lens, which focusses on the slit C, 
by means of a sliding tube, H ; both the prisms and the lens 
are fastened in this tube. K is a small right-angled prism, 
covering half the slit, by the aid of which light may be seen 
reflected through the circular aperture in front of it. In this 
manner a comparison may be made wfth the spectra of metals 
or gases. The reflecting prism, with the ring to which it is 
attached, can be instantly removed, and the whole length of the 
slit used if desired. DD is a ring milled on the edge ; on 
turning this round, both edges of the slit recede from each 
other equally, being acted on by two hollow eccentrics. The 
lines can thus be increased in breadth without their original 
centres being displaced a point of importance. E is a cylin- 
drical lens attached to the tube F, which slides in another tube, 
G. To use the Spectroscope on a telescope, the adapter needs 
only to have a thread which shall enable it to be screwed into 
the draw-tube of the telescope, in the place of the ordinary 
Huyghenian eye-piece. A photographed Micrometer can be 
added to this instrument. 

The draw-tube must then be adjusted so that the slit C 
comes exactly to the focus of the object-glass. When stars, 
&c., are about to be observed, this point should be ascertained 
beforehand, by the aid of an image of the sun, some suitable 
mark to indicate the focus being made on the draw-tube of the 
telescope. When this has been once done, the tube can be set 
by this mark, and the Spectroscope screwed in at any time 
without any trouble in adjustment. 

HOW TO USE A STAR SPECTROSCOPE. 

The Spectroscope should occupy the place of an eye-piece in 
the telescope. 

The knife edges or jaws of the slit should be exactly in the 
focus of the object-glass. 



26 

In this position, if the cylindrical lens is removed, the spec- 
trum of a star will be a mere line of light. 

The cylindrical lens is for the purpose of widening this line 
to such an extent that the lines in the spectrum may readily be 
discerned ; for this purpose the lens must be placed with its axis 
at a right angle to tlie slit, and the best distance from the slit 
will be between three and six inches. 

The nearer it is brought to the slit the broader will be the 
spectrum, but it should not be used too close, on account of the 
diminution of the light. 

When it is desired to obtain the spectra of planets, comets, 
or nebulae, or indeed any heavenly bodies possessing considerable 
diameter in the telescope, the cylindrical lens may advantage- 
ously be dispensed with. 

McCLEAN'S NEW STAR SPECTROSCOPE (PATENT). 




FL'. n. 



Many persons well acquainted with the solar spectrum have 
yet never seen the beautiful and almost infinitely varied spectra 
of the stars. The Star Spectroscopes in general use are ex- 
pensive and difficult to manipulate with. This arises from the 
fact that, in most instruments, the image of a star is required to 






2; 

fall within^the jaws of a narrow slit, not more than T ^ inches 
in width, and an equatorially mounted telescope with clock- 
work is almost indispensable for using them. Star Spectro- 
scopes of simpler construction, both with and without cylin- 
drical lenses, have been made, but their performance has not 
been found satisfactory. In the instrument contrived by Mr. 
McClean, exquisitely fine lines can be seen in the spectra of 
stars without the use of any slit. The slit being dispensed with, 
the instrument can be used on any telescope without a clock, or 
even on any alt-azimuth stand ; instead of a slit, a concave 
cylindrical lens is used, to bring the lines of the spectrum to a 
focus on the retina. 

HOW TO USE McCLEAN'S STAR SPECTROSCOPE. 

To use this Star Spectroscope, it is only necessary to bring 
the star to the centre of the field of view, remove the eye-piece, 
and insert the Spectroscope instead. The Spectroscope is 
mounted in a tube, the same size as Browning's Achromatic 
Eye-pieces ; as these slide into an adapter, the change can be 
effected very quickly, without shaking the instrument. Mr. 
McClean has adapted a revolving nose-piece to his telescope, 
one arm of which carries the eye-piece, and another the Spectro- 
scope ; and, by the aid of this contrivance, the change from one 
to the other can be made instantaneously. It is necessary to 
observe that, this Spectroscope having a negative lens, the lens 
should be inside the solar focus of the object-glass or mirror 
employed ; roughly, the eye-cap of the Spectroscope should be 
placed at the solar focus. If the motion of the telescope is not 
kept up at a proper rate, the light of the spectrum wanes ; but 
being without a slit, the spectrum of a star is never entirely lost, 
and the observer can, by giving a slight motion to the telescope, 
either by screws or any other means of adjustment with which 
the stand may be provided, give the necessary motion to the 
telescope, to keep the spectrum always as bright as possible. 

The Spectroscope is applicable for any telescope of three 
inches and upwards in diameter. 

By throwing the image of an illuminated point into the field 
of view, any spectra can be seen and used for the purpose of 
comparison the required point being illuminated either by a 
Bunsen's burner, in which salts are being ignited, or by an 
induction tube, or the electric spark, taken between electrodes of 
various metals. 



28 



Mr f Browning has the exclusive right of making the 
Spectroscope. 

An adjustable slit and convex lens can be used as an 
addition to McClean's Star Spectroscope, for showing the 
Fraunhofer lines in the solar spectrum, the bright lines of the 
metals, alkalies, gases, &c. 



HOW TO USE McCLEAN'S UNIVERSAL 
SPECTROSCOPE. 




Fig. II*. 



Fig. ii**. 



The diagram (Fig. 1 1*) is a section of McClean's Star Spec- 
troscope as it is used in an astronomical telescope for viewing 
the spectra of the stars. 

When it is desired to use the instrument for chemical pur- 
poses, or for showing the Fraunhofer lines, it must be used 
without a telescope. Take out the small concave cylindrical 
lens C, which is fitted tightly into the end of the short tube A, 
containing the prism (Fig. 11*). 

Insert the small convex lens, which will be found in the 
case, in its place. 

Remove the adapter B, in which the small tube containing 
prisms has been used with the telescope. 

Now place the tube A, containing the prisms and convex 
lens, in the tube carrying the slit, and proceed to use it as in the 
instructions for using a Direct-Vision Spectroscope. 

The Spectroscope, as now arranged, is shown in the diagram 
(Fig. ii**). Note that the lines on the tube containing the 
prisms and the tube carrying the slit must be made to coincide 
while focussing the lines in the spectrum. 

The small milled head D in this diagram serves to regulate 
the width of the slit. 

The second arrangement of the Spectroscope (Fig. n**) may 
be used for viewing the chemical spectra, the spectra of the 
metals, the spectra of gases in induction tubes, or absorption 
bands in liquids. 



2 9 

Screwed .into an astronomical telescope by the coarse screw 
known as the astronomical thread, B (Fig. n**), it will show the 
bright lines of the gaseous nebulae, the spectra of the planets, 
or the bright lines of the solar prominences. 



THE INDUCTION COIL, 

For working Induction Tubes, giving the Spectra of the Gases, or for obtaining the 
Spectra of the Metals by the aid of the Electric Spark. 




Fig. 14. 



REQUIRED FOR WORKING INDUCTION TUBES. 

Either an Induction Coil, to give a ^-in. spark in dry air, 
which should be used with I quart-size Bunsen's cell ; 

An Induction Coil, to give a i-in. spark in dry air, with 2 
quart-size Bunsen's cells ; or- 

An Induction Coil, to give a ij-in. spark in dry air, with 
3 quart-size Bunsen's cells. 

REQUIRED FOR OBTAINING THE SPECTRA OF THE METALS. 

Either an Induction Coil, to give a 2^-in. spark in dry air, 
with I quart-size Bunsen's cell ; 

An Induction Coil, to give a 3-|-in. spark in dry air, with 3 
quart-size Bunsen's cells ; 



An Induction Coil, to give a 4^-in. spark in dry air, with 5 
quart-size Bunsen's cells ; or 

An Induction Coil, to give a 6-in. spark in dry air, with 6 
quart-size Bunsen's cells. 

Where the trouble of charging Bunsen's cells is objected to, 
or it is desirable to avoid the nitrous fumes they give off, 
bichromate batteries can be employed. These batteries are 
very cleanly, but not nearly so powerful as the Grove's or 
Bunsen's batteries, so that the Coils will not work with their 
full power when they are used. 

A bichromate battery can be arranged so that, by using a 
winch, the elements may be removed from the exciting solution 
at pleasure. These batteries may be used many times without 
re-charging. One of these batteries is shown in the engraving 
facing page 31. 

BROWNING'S SPARK CONDENSER. 




This contrivance is designed to replace the Leyden Jars which 
are generally used with Induction Coils to increase the tempera- 
ture of the spark when it is required for spectrum analysis. 
The apparatus consists of an arrangement of ebonite plates 
coated with tinfoil, and enclosed in a mahogany case. Any 
amount of surface may be used at pleasure by rotating the circle 
on the top of the case. Unlike the Leyden Jar, the action of 



. 

the apparatus is not affected by damp. A very convenient 
arrangement for holding the metals of which the spectra are 
required, screws on to the lid of the case, and when not in use 
packs inside the lid. 

Becquerel's apparatus for obtaining continuous spectra from 
solutions of salts of the metals is attached when required. It is 
shown on the left of the upright rod in Fig. 15. 

HOW TO USE BROWNING'S SPARK CONDENSER. 



BATTERY 




SPARK CONDENSER 



Fig. 150. 

Connect the wires from the battery with the two clamp 
screws at one end of the Induction Coil. Then carry a fine 
wire from each of the terminals of the coil (the points from 
which the sparks are given), one to each clamp screw at the 
opposite ends of the Spark Condenser. If the commutator of 
the coil be now turned on, the spark will pass between any 
pieces of metal placed in the two pairs of tweezers on the 
insulated ebonite support of the Spark Condenser. This spark 
will be very different from that of the Induction Coil being 
shorter, thicker, and much more brilliant. A spark given 
through the Condenser, from T ^ to of an inch long, is best 
adapted to give the spectra of the metals in the Spectroscope. 

The diagram (Fig. 15*2) will perhaps show more clearly 



than any description how the connections between the battery, 
spark condenser, and coil are to be arranged. When a Leyden 
Jar is used, the connections are arranged in a similar manner, 
but the two wires from the coil must be connected with the 
inside and outside coating of the Leyden Jar. 

HOW TO OBTAIN THE SPECTRA OF THE METALS. 

For the purpose of obtaining the spectra of the metals, use 
an Induction Coil. The coil should give sparks at least two 
inches long in dry air. Unless you have a Spark Condenser, 
a Leyden Jar should be introduced in the circuit, as shown in 
the engraving facing page 31, for the purpose of increasing the 
temperature of the spark. Two small pieces of the metal of 
which the spectrum is required should be placed in forceps 
attached to the terminals of the Induction Coil. These pieces 
of metal should be brought within one-eighth of an inch of 
each other. The spark should pass in a vertical line parallel to 
and in front of the slit. 

The Leyden Jar must be connected with the Induction Coil 
in the following manner : Attach a wire to the metal rod which 
supports one pair of forceps on the terminal of the coil, and 
carry this to the outside covering of the Leyden Jar. A second 
wire should be attached in a similar manner to the other pair 
of forceps, and connected with the inside covering of the Leyden 
Jar. This suffices to bring the Jar into the circuit. When the 
spark from the metal is obtained the further manipulation will 
be the same as described, with a bead of salt on a platinum wire, 
under the heading of the " Chemical Spectroscope." 

HOW TO USE BECQUEREL'S APPARATUS. 

This Apparatus is shown attached to the Spark Condenser 
(Fig. 15), on the left of the upright rod. Make a concentrated 
solution of a salt of the metal. Pour this solution into the glass 
tube until it covers the platinum wire in the bottom part of the 
tube by about one-eighth of an inch. Then, by turning the 
screw with an ebonite head, bring down the upper platinum wire 
until it is about one-eighth of an inch above the surface of the 
solution. Having done this, attach one wire from the Induction 
Coil to the upper platinum wire, and the other to the lower 
platinum wire. On turning the commutator of the Induction 
Coil, the spark will pass through the liquid, and on bringing the 
slit of the Spectroscope close to the side of the tube, the 
spectrum of the metal which is in solution may be obtained for 
a considerable time. 



33 
LOCKYER'S REVOLVING SPARK APPARATUS. 




This is a contrivance for the purpose of holding a number of 
pieces of different metals or metallic salts in small carbon 
crucibles. The metals are held in small pairs of tweezers, each 
pair being insulated. They are provided with independent ad- 
justments. There is a vertical adjustment by means of a rack 
and horizontal movement given by an endless screw. The 
spark only passes through the tweezers in front of the Spec- 
troscope, By means of these adjustments, the various metals 
can be brought in front of the slit of the Spectroscope, and their 
spectra obtained with the greatest ease, rapidity, and certainty. 



BESSEMER SPECTROSCOPES. 

Either of the Direct-Vision Spectroscopes, enumerated on 
pages 12 and 13, is well adapted for viewing the Bessemer flame, 
and great numbers are in constant use for this purpose in all parts 
of Europe, the highest power being best adapted for the purpose; 



34 

but the writer has devised a special instrument (the Direct- 
Vision Bessemer Spectroscope, with ten prisms), of very great 
dispersive power, having an eye-piece of large field, which shows 
the whole of the spectrum, giving admirable definition in all 
parts of the field. 

The instrument below (Fig. 16) is a still more powerful 
instrument. The telescope has a motion between pivots, near 
the top of the case. There are cross-wires in the field of view 
to assist the observer in concentrating his own attention, or 




Fig. 16. 

directing that of others, to any particular line in the spectrum. 
This instrument is so contrived that the back of the observer is 



35 

turned tcTthe brilliant flame, which renders vision much easier. 
A condensing lens, shown in the engraving, which works on a 
rod in front of the slit, can be fixed so as to produce an image 
of the flame on the slit ; by moving the instrument about on the 
hinged joint and swivel, the spectrum of any portion of the 
flame can be examined at pleasure. With this arrangement the 
Spectroscope can be used without disadvantage at any distance 
from the flame. The slit is protected from the action of dust 
by means of a glass cover; and when the instrument is not in 
use it can be unscrewed and enclosed in the box. 

HOW TO USE A BESSEMER SPECTROSCOPE. 

In the Bessemer process several tons of iron are placed in a 
large vessel, and when in a state of fusion, air is driven through 
it from apertures in the bottom of the vessel. After about 
twenty minutes the iron is converted into steel. During the 
process a flame of almost overpowering brilliancy issues from 
the mouth of the vessel. The conversion is almost instant- 
aneous, and is known by a change in the colour of the flame 
and a reduction of its brilliancy. It requires, however, consider- 
able practice to tell by naked eye observations when the process 
should be stopped ; and intently watching the great glare is most 
trying to the sight. By the aid of the Spectroscope the com- 
pletion of the process may be determined without any experience 
with the utmost ease and certainty. 

The spectrum of the Bessemer flame is full of bright lines, a 
number of green lines being the most brilliant. At the instant 
of complete conversion these bright green lines suddenly dis- 
appear. At this moment the blowing should be stopped. Either 
of the Direct-Vision Spectroscopes described in this pamphlet 
may be used for the Bessemer process, but those specially made 
for the purpose, and termed Bessemer Spectroscopes, will give 
the most certain results. The engraving (Fig. 16) shows the 
instrument devised by the writer for Sir John Brown's Steel 
Works, Sheffield. When using this instrument the observer's 
back is turned to the bright Bessemer flame. The whole instru- 
ment, except the telescope, is enclosed at all times in its maho- 
gany case, and the slit is protected also from the dust caused by 
the blowing process by a disc of glass. 

There is a pointer in the field of view of the eye-piece ; this 
may be set to any particular line in the spectrum, and the work- 
man may be instructed to stop the process when this disappears. 

For full information respecting the spectra given by the 
Bessemer process, see Roscoe's " Spectrum Analysis." 



THE SMALL AUTOMATIC ELECTRIC LAMP. 





Fig. 17. 



Fig. 18. 



In the engraving (Fig. 17) the carbon points are carried by 
the holders, A B, which are provided with rings like a porte- 
crayon, to clamp the points when in position. C D is a soft 
iron feeder ; the end, C, of this feeder is so arranged that a very 
slight pressure on the feeder clamps the rod B, and prevents it 
from descending. E is a rod of soft iron, in the form of a horse- 
shoe ; when the electricity passes through the wire wound upon 
this horse-shoe, the iron becomes a magnet, and attracts the 
feeder. F and G are clamping screws, to clamp the sliding rods 
in any required position. H is a silvered parabolic reflector, for 
throwing the light of the Lamp to a great distance. 

The small Automatic Electric Lamp (Fig. 18) is of similar 
construction, and can be set in action in the same manner ; but 
it has an additional movement for regulating the height of the 
carbon poles when burning. This action is influenced by the 
small milled head on the right-hand pillar, near the base of the 
stand. Should the poles burn unequally, a few revolutions of 



37 

this screw will keep them burning always at the same height. 
This motion is also especially useful when the Lamp is used for 
showing spectra in screen experiments. In spectrum analysis it 
should be used in the following manner : The small milled head 
resting on the top of the arm at right angles to the upright 
pillar should be turned round, until a spring falls into the oval 
opening ; it then catches the vertical rod and holds the upper 
carbon fast. A hollow having been made in the lower carbon, 
and the metal of which the spectrum is desired having been placed 
in the small crucible thus formed, the lower carbon is raised by 
the action of the small screw before referred to, on the right- 
hand pillar ; when it has been brought into contact with the 
upper rod, it is carefully separated until the best result is 
obtained on the screen. More detailed information on this 
subject will be found under the heading, "How to Show Spectra 
on a Screen." 

The sharpness of the spectrum will be influenced by the width 
of the slit on the nozzle of the Lantern. The closer the slit the 
purer will be the colours of the spectrum and the better the 
definition of the bright lines or absorption bands when liquids 
are used. Of course the limit is quickly reached at which the 
slit must be left, or otherwise the results would become unsatis- 
factory from want of sufficient light. 



HOW TO USE THE SMALL AUTOMATIC LAMP. 

Release the clamps, F G ; place two pieces of fine hard carbon 
in the holders ; the carbons should be well pointed ; wipe the 
rod, B, with a leather, so that it may slide freely ; then adjust 
the large central rod so that the extreme point of the upper 
carbon exactly rests upon the lower carbon. Attach the wire 
from the last plate of zinc in the battery to the lower carbon 
holder, and the wire from the plate of platinum at the opposite 
end of the battery to the upper carbon holder. If the light 
should not burn steadily, alter the position of the magnet by 
means of a small set screw between the ends ; this screw is not 
shown in the drawing. The magnet must not be put close to 
the feeder ; the best distance to place the magnet from the 
feeder is generally about half an inch, but this will vary with the 
power of the battery employed. 

The Lamp is regulated by means of a small screw, shown in 
the diagram at C (Fig. 17). This must be done while the bat- 
tery is attached to the Lamp. By a few trials, turning this screw 



38 

backwards and forwards, it will be found that the light of the 
Lamp will become continuous, and it may be left even half an 
hour at a time, giving a steady light without any attention. 
Twenty quart cells are quite sufficient to work the Lamp well ; if 
more are used it becomes too hot. When correctly adjusted 
there should be no perceptible motion of the feeder. 

BROWNING'S LARGE ELECTRIC LAMPS OR 
REGULATORS. 




In these Regulators both carbons are moved by the electricity 
of the battery employed (without the aid of clockwork) ; the 
light remains uniform in height and more steady in action than 
any of the expensive Regulators previously introduced. 

The medium-size Automatic Regulator (Fig. 19). This Lamp 
works well with from 20 to 30 pint Grove's cells, or the same 
number of quart Bunsen's. 

The large-size Automatic Regulator. From 25 to 50 quart 
Grove's cells, or the same number of two-quart Bunsen's, 
should be used with this Lamp. 



39 



HOW 'TO USE BROWNING'S LARGE AUTOMATIC 

LAMP. 

As the Electric Lamp is an essential part of Screen Spectrum 
Apparatus, it is desirable that a brief description of the method 
of working with the instrument should be given here. 

Inside the mahogany case of the Electric Lamp there is a 
small brass vertical cylinder. 

Take care that the piston works freely inside the cylinder, 
and that the cylinder is full of glycerine. 

The object of this arrangement is to prevent the Lamp acting 
with violent jerks. 

Also that the long vertical rod with the milled head at the 
top moves freely in the tube, and that the iron rods attached to 
the armature run freely to and fro in the helices of covered 
copper wire. - 

When the ends of the carbon rods recede too far from each 
other, an unsteady light is the result. This can be remedied by 
moving the small horizontal lever in the' front of the large brass 
plate towards the right. By acting on a strong steel spring, this 
brings the points of the carbons nearer together. 

If the carbon rods do not burn away equally, the light will 
not be opposite the centre of the parabolic reflector, or lens used 
for projecting it to a distance. A milled head on the right 
hand of the base of the Lamp acts on rackwork, which will 
regulate the height of the lower carbon rod. The upper rod 
will accommodate itself to the lower rod. 

Owing to inequalities in the carbon, the electric light some- 
times appears at the side or the back of the carbons. To set 
this right, move the upper rod by the ebonite head. When a 
parabolic reflector is used, the light should be brightest on the 
side towards the upright rod, but it should be brightest 
on the opposite side to the rod when a lens is used, or when 
the Lamp is placed in a lantern. 

Before making contact with the battery by means of the turning 
lever of bright copper at the back of the Lamp, press the iron 
armature firmly forward, so that the iron rods are completely in 
the hollow coils or helices of covered copper wire. 

INSTRUCTIONS FOR CHARGING THE BATTERY. 
Fill the porous cells with nitric acid that is, commercial 
aquafortis and insert the platinum foil or carbon plate. In a 
strong stoneware vessel, mix one part of oil of vitriol that is, 
commercial sulphuric acid with seven parts of water. Fill the 
outer cells with this mixture, having first introduced the zinc 



40 

plates and porous cells. After the porous cells have been 
placed in the centre of the zinc plates, connect the platinum or 
carbon plate in each cell with the zinc plate in the next cell by 
means of the brass clamps ; attach one of the clamps with the 
finger-screw at top to the unconnected platinum or carbon plate 
at one end of the battery, and the other clamp of the same kind 
to the unconnected zinc plate at the opposite end of the battery ; 
then connect these ends with the copper wires as before directed. 
The battery will not attain its full power in less than half an 
hour after charging. When the battery is done with, the porous 
cells, zinc, and platinum or carbon plates should be well washed 
in water. The porous cells should be allowed to remain in fresh 
water for several hours. 

Occasionally, when the zinc plates are taken out of the acid, 
a little mercury should be well rubbed over them, by means of a 
piece of rag tied round a small stick. This should be done 
before they are washed in water. 

SETS OF APPARATUS FOR PRODUCING THE 
ELECTRIC LIGHT, 

No. I. Small-size Electric Lamp with Reflector ; 20 quart 
Bunsen's Cells ; two Varnished Oak Trays, to hold 10 cells 
each ; Carbon Rods. 

No. 2. Medium-size Automatic Electric Lamp ; 30 quart 
Bunsen's Cells ; three Varnished Oak Trays ; Carbon Rods. 

No. 3. Large Automatic Electric Lamp ; 50 quart 
Bunsen's Cells ; five Varnished Oak Trays ; Carbon Rods. 

SPECTRUM APPARATUS, FOR SCREEN 
EXPERIMENTS. 




Fig. 20. 



41 

The engraving (Fig. 20) represents a new and complete set 
of apparatus, at a very low price, for projecting the spectra of 
metals, or the absorption bands of liquids, on a screen. The 
apparatus comprises an Automatic Electric Lamp and Lantern, 
with slit, a 20-quart Bunsen's cell, battery, and trays, mounted 
focussing lens, bisulphide of carbon prism and stand, platform 
for the whole, and packing case. 

An inner case, which fits into the body of the Lantern, con- 
tains the Electric Lamp (Fig. 18) in packings, a set of chemicals 
which give the most brilliant spectra, and a supply of carbon 
rods and carbon crucibles. 

A nozzle with lenses and 3j-inch condensers can be adapted 
to this Lantern, for showing diagrams or views on screen. 

SCREEN SPECTRUM APPARATUS. 




Fig. 21. 

Fig. 21 represents a new metal body Electric Lantern for 
Spectroscopists, with an Electric Regulator specially adapted to 
the same. There are two nozzles, one for showing diagrams, 



42 

and the other for exhibiting spectra on a screen ; this apparatus 
is efficient in action, and yet economical in price. 

The medium-size Automatic Electric Lamp, which is adapted 
to this Lantern, is of the best construction, and works well with 
from 20 to 30 pint Grove's cells, or the same number of quart 
Bunsen's. 

SCREEN SPECTRUM APPARATUS. 




Improved Lantern, the body of brass, bronzed, with two 
nozzles, especially arranged for exhibiting spectra or diagrams 
on the same screen without shifting the Lantern or re- arranging 
the apparatus, with 3j-inch condensers (Fig, 22) ; a larger size 
Lantern is made with 4j-inch condensers. 

A very complete set of Screen Spectrum Apparatus should 
consist of an Improved Electric Lantern, with 4j-inch con- 






43 



densers (Fig. 22) , the body of brass, bronzed, with two fixed nozzles 
specially arranged for exhibiting spectra or diagrams on the 
same screen, without shifting the Lantern or re-arranging any part 
of the apparatus; large-size Electric Regulator for the above, to 
work with from 25 to 50 Grove's or Bunsen's cells ; two extra-size 
Bisulphide of Carbon Prisms ; Prism Stand and Cover, adjust- 
able for height with clamp motions ; large Condensing Lens 
on Brass Stand, adjustable for height ; Revolving Diaphragms 
RotatingCarbon Holder; Mahogany Case containing set of Metal ; 
and Salts for burning in the Electric Arc, with carbon crucibles, 
pliers, and 6 feet of carbon rods, &c., for the large Regulator ; 
Battery of 40 quart Bunsen's cells, in four varnished oak trays ; 
set of Metals and Salts for burning in the Electric Arc, and 
showing their spectra ; carbon crucibles, pliers, and carbon rods, 
in case. 

HOW TO SHOW SPECTRA ON A SCREEN. 

The apparatus for screen experiments consists of an Electric 
Lamp, a Lantern with a slit fixed vertically in place of condensers, 
a large convex lens mounted on a stand, and either one or two 
bottle prisms filled with bisulphide of carbon. This apparatus 
is arranged in the order shown in Fig. 20. The substance of 
which it is desired to obtain the spectrum should be placed in 
a hollow cup, bored out of the lower carbon rod in the Electric 
Lamp or Regulator. The upper rod should be brought into 
contact with the substance, and then carefully withdrawn until a 
steady spectrum, consisting principally of bright lines, is seen ; 
the wider the two carbon rods are separated, so long as sufficient 
light is left, the better will be the result, as in this manner the 
brilliant continuous spectrum of the carbon rods, which masks 
the character of the bright lines, is got rid of. It must be clearly 
understood that although for all ordinary purposes it is essential 
that the Electric Lamp should be automatic, yet, for obtaining 
the spectra of any substance, the Lamp imist be fixed for a certain 
length of time, for so long as the poles are allowed to approximate 
to each other, as tliey ^woitld do by the automatic arrangement, so 
long we shall obtain only the continuous spectrum of the poles, as 
has been before described. 

The Lamp being arranged within the Lantern, as shown in 
Fig. 22, the slit on the nozzle of the Lamp must be placed in a 
vertical direction ; the fixed lens, adjusted so that the height of 
the centre of the lens corresponds with the centre of the slit, must 
then be drawn backwards and forwards along the stand on which 



44 

the apparatus is fitted, until a sharp image of the slit is produced 
on a piece of paper, at a distance of from 10 to 20 feet, according 
to the size of the room in which the experiments are to be 
conducted ; the distance, however, should be no greater than will 
produce a spectrum sufficiently large to be seen by the audience. 
Having obtained the bright image of the slit in the manner just 
described, either one or two bottle prisms must be brought in 
front of the lens, just beyond the place at which the rays from 
the fixed lens cross, after coming nearly to a point. The prism 
must then be turned round slowly ; as it is turning, a spectrum 
will be seen to travel along the face of the screen, placed at an 
angle of nearly 90? to the apparatus, and at about the same 
distance from the apparatus at which the bright image of the 
slit was formed. With the small apparatus only one bisulphide 
of carbon prism can be used ; but with the large Electric Lamp 
(Fig. 19) and the Lantern (Fig. 22), the light is sufficiently 
strong to allow of the use of two prisms, and these will give a 
much longer spectrum. The small carbon crucibles made for the 
purpose are more efficient than an ordinary carbon rod for 
obtaining the spectra, as they will hold more of the material to 
be operated on. 

Where time is an object, as in a lecture, a number of these 
crucibles, fitted in a series of tubes on a revolving holder on the 
centre round which these revolve, must be placed eccentrically, 
and the crucibles already charged with the various substances 
can be brought successively to coincide with the upper pole, and 
operated on at pleasure. It is difficult to obtain the spectrum 
of iron in this manner ; a better result can be secured by fixing 
in the upper carbon holder a piece of iron, and allowing this to 
come into contact with the carbon rod, taking care that they do 
not fuse together. 

The most interesting experiment which can be made with 
this apparatus is the reversal of the soda line ; but the experi- 
ment is one which requires a little skill in manipulation, yet it is 
not difficult if the following precautions are attended to : Let the 
Lamp be carefully closed in with a cover of stiff brown paper 
over the apertures left for the purpose of ventilation ; set light to 
a piece of metallic sodium the size of a pea in a small iron 
spoon, by means of a spirit-lamp ; this must be done inside the 
Lantern, the spoon being first made nearly red-hot ; the spoon 
should be attached to a small holder, and left inside the Lamp, 
with the door shut, until the Lamp becomes filled with the 
vapour of the burning sodium. One of the carbon crucibles or 
the lower rod of the Electric Lamp having had a piece of 



45 

sodium placed on it, the upper end of the Electric Lamp can be 
brought into contact with it ; the intense light generated will 
then produce a faint continuous spectrum on the screen, with a 
very bright sodium line predominant ; after a short time, varying 
between a few seconds and two or three minutes, if the Lantern 
has been sufficiently filled with the vapour of the sodium burn- 
ing in the spoon, these bright lines will become dark ones. 
Probably in the course of the experiments they will again be- 
come bright, and the reversal be repeated two or three times. 
The explanation of this experiment is, that the vapour of the 
sodium in the Lantern being cooler than the sodium burning 
between the poles of the Lamp, the bright light of the sodium is 
absorbed by the sodium vapour. 

Salts of silver, zinc, copper, or small pieces of the metals 
themselves, give the most brilliant spectra. 

This apparatus may be used without any modification for 
the purpose of showing the absorption bands in many coloured 
substances or liquids. In operating on liquids, they should be 
placed in a hollow wedge-shape cell ; these should be brought 
in front of the slit, and moved along until such a thickness of 
the liquid comes in front of the slit as will produce sufficiently 
strongly-marked absorption bands in the spectrum. During 
these experiments the Electric Lamp must be kept burning 
continuously by the automatic action as steadily as possible. The 
liquids named in the series of specimens on page 49 all give 
good results. As a few of the most strongly-marked spectra, I 
will mention blood, sumach, permanganate of potash, chloro- 
phyll, and magenta. 



SPECTRUM APPARATUS FOR THE MICROSCOPE. 

The writer has worked in conjunction with H. C. Sorby 
Esq., F.R.S., in his experiments, having for their object the 
improvement of this apparatus, and has just perfected a new 
Micrometric arrangement, which possesses great advantages. 
The Micro-Spectroscope is applied to the eye-piece of a Micro- 
scope instead of an ordinary eye-piece. 

It is applicable to opaque objects as well as transparent 
without preparation, and by its means two spectra may be com- 
pared at the same time with one lamp. It possesses the 
immense advantage over all other contrivances of the kind, that 



4 6 

the spectrum of the smallest object, or a particular portion of 
any object, may be obtained with the greatest certainty and 




Fig. 23. 

facility. This Micro-Spectroscope will indicate plainly the 
minutest quantity of blood, adulterations in wine, mustard, 
peppermint, oil, and many other articles of food, as well as the 
absorption bands in the leaves and juices of plants. 



HOW TO USE THE MICRO-SPECTROSCOPE. 

As will be seen from Fig. 23, the Micro-Spectroscope is a 
very compact piece of apparatus, consisting of several parts. 
The prism is contained in a small tube, A, which can be removed 
at pleasure. Below the prism is an achromatic eye-piece, having 
an adjustable slit between the two lenses ; the upper lens being 
furnished with a screw motion to focus the slit. A side slit, 
capable of adjustment, admits, when required, a second beam of 
light from any object whose spectrum it is desired to compare 
with that of the object placed on the stage of the Microscope. 



47 

This second beam of light strikes against a very small prism 
suitably placed inside the apparatus, and is reflected up through 
the compound prism, forming a spectrum in the same field with 
that obtained from the object on the stage (Fig. 24, page 52). 
A (Fig. 23) is a brass tube carrying the compound direct-vision 
prism, and has a sliding arrangement for roughly focussing. B, 
a milled head, with screw motion to finally adjust the focus of 
the achromatic eye-lens. 

C, milled head, with screw motion to open or shut the slit 
vertically. Another screw, H, at right angles to C, regulates 
the slit horizontally. This screw has a larger head, and when 
once recognized cannot be mistaken for the other. 

D D, an apparatus for holding small tube, that the spectrum 
given by its contents may be compared with that from any other 
object on the stage. 

E, a screw opening and shutting a slit to admit the quantity 
of light required to form the second spectrum. Light entering 
the aperture near E strikes against the right-angled prism which 
we have mentioned as being placed inside the apparatus, and is 
reflected up through the slit belonging to the compound prism. 
If any incandescent object is placed in a suitable position with 
reference to the aperture, its spectrum will be obtained, and will 
be seen on looking through it. 

F shows the position of the field lens of the eye-piece. 

G is a tube made to fit the Microscope to which the 
instrument is applied. To use this instrument, insert G, like an 
eye-piece in the Microscope tube. Screw on to the Microscope the 
object-glass required, and place the object whose spectrum is to be 
viewed on the stage. Illuminate with stage mirror if transparent, 
with mirror and lieberkiihn and dark well if opaque, or by side 
reflector, bull's-eye, &c. Remove A, and open the slit by means 
of the milled head, H, at right angles to D D. When the slit 
is sufficiently open the rest of the apparatus acts like an ordinary 
eye-piece, and any object can be focussed in the usual way. 
Having focussed the object, replace A, and gradually close the 
slit till a good spectrum is obtained. The spectrum will be 
much improved by throwing the object a little out of focus. 

Every part of the spectrum differs slightly from adjacent 
parts in refrangibility, and delicate bands or lines can only be 
brought out by accurately focussing their own parts of the 
spectrum. This can be done by the milled head, B, Dis- 
appointment will occur in any attempt at delicate investigation 
if this direction is not carefully attended to. 



48 

When the spectra of very small objects are to be viewed, 
powers of from |-inch to ^th may be employed. 

Blood, madder, aniline dyes, permanganate of potash 
solution, are convenient substances to begin experiments with. 
Solutions that are too strong are apt to give dark clouds instead 
of delicate absorption bands. 

Small cells or tubes should be used to hold fluids for 
examination. 

Objects, such as crystals, should invariably have a small card- 
board diaphragm, diameter, placed beneath them ; the spec- 
trum is then much better defined. With a slide containing a 
mass of small crystals, the object need merely be thrown a little 
out of focus. When observing the spectra of liquids in experi- 
ment cells, or through small test-tubes, always slip over the 
tube containing the i^ or 2-inch objective a cap with a hole 
i-i6th of an inch diameter. Slide the tube just sufficiently to 
bring the small hole a little within the focus of the objective. 
By this arrangement all extraneous light is prevented from 
passing up the body of the Microscope, except what passes 
through the object. Unless this precaution be attended to, a 
false result is sometimes obtained. 

Substances which give bands or lines in the red, are best 
seen by gaslight, while those which give bands in the blue are 
brought out far better by daylight. Such a specimen as oxalate 
of chromium and soda is almost opaque by daylight, showing 
no bands, though, when examined by a lamp, the spectrum 
exhibits three beautifully fine lines in the red, two of which are 
exceedingly delicate. Again, uranic acetate can only be seen 
to advantage by strong daylight, since the band in the violet 
would be invisible by lamp-light. 

A number of dyes are beautifully shown by being dissolved in 
gelatine. A plate containing one dozen small strips of gelatine 
about -inch wide and J-inch long, is exceedingly convenient 
for the purpose of showing the spectra of these dyes. When 
the slit of the Spectroscope is placed across the junction of two 
of the plates, any two spectra can be seen at the same time in 
the field of view, and thus comparisons may be made between 
them. If two such plates be superimposed, a great number of 
spectra, in which the absorption bands of two substances appear 
at the same time, are shown. These plates are much more easy 
to manipulate with than tubes. 

For information as to mapping spectra with the Micro- 
Spectroscope, see the instructions under a separate heading. 



49 



OBJECTS FOR THE MICRO-SPECTROSCOPE, 



Liquids in Glass Tubes Hermetically Sealed, as used by 
H. C. SORBY, Esq., P.R.S. 

CLASS I. 

Specimens for Illustrating the Application of the ' Micro- Spectroscope to Chemistry. 



Cruentine Neutral. 
Didymium. 
Aniline Product. 
Hasmatin Deox. 
Uranium Garb. 
Purpurine. 



PERMANENT SPECIMENS. 

7. Chromic Oxal. 

8. Cruentine Acid. 

9. Hypericine. 

10. Uranium Sulph. 

11. Cobalt Chloride. 

12. Cobalt Cyanide. 

In Morocco Case. 



CLASS II. 

STANDARD BLOWPIPE BEADS. 

For Spectrum Tests of Metallic Oxides. 

Cobalt (blue). 6. Tungsten. 

Erbium. 7. Didymium. 

Uranium. 8. Chromium. 

Molybdenum. 9. Copper (red). 

Uranium Borate. 10. Uranite (Mineral). 

The Spectra are best seen with Lamplight. 



CLASS III. 

Dyes. 

Consisting of a plate containing a set of twelve substances in gelatine in a most 
compact form, and so arranged that two spectra can be seen simultaneously by 
placing the plate in front of the slit of the Spectroscope, giving in all eighteen different 
comparisons. Also, by superposing two such plates at right angles, thirty-six com- 
partments are visible which show the phenomena of mixed spectra. 

This arrangement is exceedingly useful for showing absorption spectra at a lecture, 
since six spectra can be thrown on to the screen at once. 

The Plates are fitted in Morocco Cases. 



50 

HOW TO MAKE A MAP OF A SPECTRUM WITH 
A STUDENT'S SPECTROSCOPE. 

Place the eye-piece with cross-wires in the telescope, with the 
cross in the direction of an X Then move the telescope so that 
the point where the wires bisect comes successively in contact 
with the various lines, noting the readings of the vernier on the 
arc. From these readings, by the help of any mechanical scale 
of equal parts, a map may be easily constructed, 




Fig. 26. 

HOW TO MAP A SPECTRUM WITH BECKLEY'S 
SPECTROGRAPH. 

Place a sheet of paper on the metal cylinder of the Spectro- 
graph. Note the position of any line in a spectrum, and set the 
divided edge of the Spectrograph to the corresponding division 
on the vernier. Draw a line on the paper along the steel 
straight-edge. Now take the reading of another line, and 
proceed in a similar manner until the map is completed. 




Fig. 27. 



Si 

HOW TO MAP A SPECTRUM WITH COLONEL 
CAMPBELL'S SPECTROGRAPH. 

Place a strip of smoked glass in the frame attached to the 
side of the Micrometer (Fig. 27). Place the tube of the Micro- 
meter in the eye-draw of the telescope of a Spectroscope. 
Bring the cross-wires of the Micrometer on to one of the lines 
in the spectrum by turning the Micrometer screw. Now draw 
a line on the smoked glass with the small ruling machine on 
the left hand in the engraving. Repeat this operation for as 
many lines as it is desired to map, always turning the screiv in 
one direction. The smoked glass may be varnished and used as 
a negative to print copies from by photography, on glass or 
paper, at pleasure. 

HOW TO MAP A SPECTRUM WITH THE 
AUTOMATIC SPECTROSCOPE. 

Place the Filar Micrometer in the telescope. Bring some 
easily recognized line to correspond with the fixed wire of the 
Micrometer ; then, by moving the Micrometer-head, make the 
movable wire coincide with another line in the spectrum. Read 
the indication on the Micrometer-head, and note it. The small 
wheel at the side of the Micrometer-head shows whole revolu- 
tions of the screw, the long divisions on the Micrometer-head 
tenths, and the short divisions hundredths of a revolution. Then 
take a scale of equal parts, and represent each division on the 
Micrometer-head by one division on the scale. 

It is obvious that the map of a spectrum may be made of 
any size by varying the scale from which the divisions are taken. 

HOW TO MAP A SPECTRUM OF ABSORPTION 
BANDS WITH A MICRO-SPECTROSCOPE. 

Fig. 24 represents the upper part of the Micro-Spectroscope- 
Attached to the side is a small tube, A A. At the outer part^of 
this tube is a glass plate, blackened, with a fine clear white 
pointer in the centre of the tube. The lens, C, which is focussed 
by moving the small studs at M, produces an image of the 
bright pointer in the field of view by reflection from the surface 
of the prism nearest the eye. On turning the Micrometer screw, 
M, the slide which holds the glass plate is made to travel in 
grooves, and the fine pointer is made to traverse the whole 
length of the spectrum. 

It might at first sight appear as if any ordinary spider's web 



52 

or parallel wire Micrometer might be used instead of this con- 
trivance ; but on closer attention it will be seen that as the 
spectrum will not permit of magnification by the use of lenses, 
the line of such an ordinary Micrometer could not be brought to 
focus and rendered visible. The bright pointer of the new 
arrangement possesses this great advantage that it does not 
illuminate the whole field of view. 

If a dark wire were used and illuminated, the bright diffused 
light would almost obscure the faint light of the spectra, and 
entirely prevent the possibility of seeing, let alone measuring, 
the position of lines or bands in the most refrangible part of the 
spectrum. 




Fig. 24. 

To produce good effects with this apparatus, the upper 
surface of the compound prism, P, must make an angle of 
exactly 45 with the sides of the tube. Under these circum- 
stances, the limits of correction for the path of the rays in their 
passage through the dispersing prisms are very restricted, and 
must be strictly observed. The usual method of correcting by 



53 

the outer surface is inadmissible. For the sake of simplicity, 
some of the work of the lower part of the Micro-Spectroscope is 
omitted in the engraving. As to the method of using this 
contrivance : with the apparatus just described, measure the 
position of the principal Fraunhofer lines in the solar spectrum. 
Let this be done carefully, in bright daylight. A little time 
given to this measurement will not be thrown away, as it will 
not require to be done again. Note down the numbers corre- 
sponding to the position of the lines, and draw a spectrum from 
a scale of equal parts. About three inches will be found long 
enough for this spectrum ; but it may be made as much longer 
as is thought desirable, as the measurements will not depend 
in any way on the distance of these lines apart, but only on the 
micrometric numbers attached to them. Let this scale be done 
on cardboard, and preserved for reference. Now measure the 
position of the dark bands in any absorption spectra, taking 
care for this purpose to use lamplight, as daylight will give, of 
course, the Fraunhofer lines, which will tend to confuse your 
spectrum. If the few lines occurring in most absorption spectra 
be now drawn to the same scale as the solar spectrum, on placing 
the scales side by side, a glance will show the exact position of 
the bands in the spectrum relatively to the Fraunhofer lines, 
which thus treated form a natural and unchangeable scale (see 
diagram, Fig. 24*). But for purposes of comparison it will be 
found sufficient to compare the two lists of numbers representing 
the micrometric measures, simply exchanging copies of the scale 
of Fraunhofer lines, or the numbers representing them will enable 
observers at a distance from each other to compare their results, 
or even to work simultaneously on the same subject. 




Fig.-24*. 

It is a great advantage of this contrivance that it does not 
monopolize one of the two spectra, as is the case with the use of 
the quartz scale ; for in describing two spectra only slightly 



54 

differing from each other, it may be used at once to determine 
the difference between them. Many substances give two 
different spectra when examined by transmitted or reflected 
light, though there is generally a close resemblance between 
them. 

Dr. MacMunn, in his work, The Spectroscope in Medicine, has 
thus described a Photographed Scale Micrometer which I first 
applied to the Microscope at his suggestion : 

" Mapping by means of Photographed Scale. Mr. Browning 
has fixed to the side of the prism tube of my Micro-Spectroscope 
a tube in the position of A (Fig. n), which contains a photo- 
graphed scale illuminated by a small mirror, and which is 
capable of being focussed by a small lens in the position of C, so 
that, on looking into the instrument, one can see the spectrum 
beautifully and accurately divided into 100 equal parts, since the 
image of the scale is reflected to the eye from the surface of the 
uppermost prism. By means of this scale readings can be made 
at once ; the only precaution necessary is to see that D, or 
the sodium line if D cannot be got, always stands at the same 
number on the scale. To map absorption spectra measured on 
this scale is exceedingly simple ; all we have to do is to lay 
down a line as many millimetres long as there are divisions 
in the scale, and mark the position of the bands on this line. 
Of course, as in the case of the bright point Micrometer, a map 
of the solar spectrum has to be first made. Another great 
advantage of this scale, besides the rapidity with which 
measurements can be made with it, is this, that it enables us to 
record certain data from which maps can at any future time 
be constructed. Thus we can record a spectrum somewhat in 
this manner : 

Extent 10 to 70 

First band ... 15 to 18 ... (A) 
Second band ... 25 to 30 ... (B) 

Any one who has worked with the Spectroscope can appreciate 
the convenience of this method." 



55 



WORKS ON SPECTRUM ANALYSIS, 



THE SPECTROSCOPE AND ITS WORK. By RICHARD A. PROCTOR, Author of 
" Saturn and its System," " The Sun," " The Moon," &c. With Coloured Diagram 
of the Spectra, and many Illustrations. Fcap. 8vo., limp cloth, is. (A popular, though 
by no means superficial, account of the Spectroscope and its marvellous work. For 
general readers, and as a text book.) 

SPECTRUM ANALYSIS in its Application to Terrestrial Substances and the Physical 
Constitution of the Heavenly Bodies, familiarly explained by Dr. H. SCHELLEN, 
Director der Realschule I. O. Cologne. Translated from Second German Edition by 
JANE and CAROLINE LASSELL. Edited, with Notes, by WILLIAM HUGGINS, 
LL.D., D.C.L., F.R.S. In i vol., 8vo., with 13 Plates (6 Coloured), including 
Angstrom's and Kirchoff's Maps and 223 Woodcuts. Price 283. cloth. 

PROFESSOR ROSCOE'S LECTURES ON SPECTRUM ANALYSIS (Third Edition), 
largely illustrated. Six Lectures on Spectrum Analysis and its Applications, 
delivered before the Society of Apothecaries. Price ^i is. 

THE SPECTROSCOPE AND ITS APPLICATIONS. By J. NORMAN LOCKYER, 
F.R.S. 3s. 6d. 



A Coloured Chart of the Spectra of the Alkaline Earths, 36 by 30 inches o 7 o 

A Coloured Chart of the Spectra of the Metals ... ... ... ... 070 

A Coloured Chart of the Spectra of the Stars and Nebulae... ... ... 070 

Any of the above, mounted on cloth and roller, and varnished o 10 6 



56 

NOTE. The Numbers in this List of Prices correspond with the 
Numbers appended to the Engravings of the Instruments in the body 
of the Book. 



JANUARY, 1883- 



The following Prices are Nett for Cash ; Half-price allowed for returned 
Packages, if Carriage Paid. 



ORDERS SHOULD BE ACCOMPANIED BY A REMITTANCE, 



DIRECT- VISION SPECTROSCOPES. 
THE MINIATURE SPECTROSCOPE. 

This Instrument will show many of the Fraunhofer lines, the bright lines of the 
metals and gases, and the absorption bands in coloured gases, crystals, or liquids. 

Miniature Spectroscope, with plain slit ^120 

Miniature Spectroscope, with adjustable slit (Fig. I ) ... i 13 o 

Miniature Spectroscope, in Brass Case, with glass at each end, for use in 

the Bessemer process I 16 6 

Morocco Case, extra 020 

Miniature Spectroscope and adjustable slit, with Achromatic Lenses, in 

Morecco Case ... ... ... ... ... 260 

Rain-band Spectroscope as recommended by Mr. Rand Capron, in 

Morocco Case (Fig. 2) 2 10 o 

Rain-band Spectroscope, with fixed slit, without glass caps or case ... I 10 o 

Browning's new Miniature Spectroscope, with Micrometer, price, complete 

in Case (Fig. 3) 3 10 o 

This portable and complete Instrument maybe used for showing any of the leading 
experiments in Spectrum Analysis ; the Fraunhofer Lines ; the Lines in the Spectra 
of the Metals, and the Alkaline Earths and Alkalies ; the Spectra of Gases ; and 
Absorption Bands. 

Applied to a Telescope, it may be used for viewing the Lines of tne Solar 
Prominences. It can also be used as a Micro-Spectroscope. The position of the 
Bands in any Spectrum may be measured with the attached Micrometer. 

Clip Stand for Miniature Spectroscope ... ... o 9 6 

New Pocket Direct-Vision Spectroscope, in Morocco Case (Fig. 4) ... 4 10 o 

New Form Direct-Vision Spectroscope, with five prisms, fitted in 

Mahogany Case ... 5 15 o 

This Spectroscope is a most powerful and portable Direct-Vision Instrument, easily 
separating the D lines in the Solar Spectrum. 

Extra power for the above ... ... ... ... o 12 6 

Large size, higher dispersive power, and extra power eye-piece, complete 

in Mahogany Case... ... ... ... ... ... 6 18 o 



57 

Portable Tripod Clip Stand for the above 1 15 o 

Direct-Vision Solar Spectroscope, for use with a Telescope for viewing the 

bright lines or the forms of the Solar Prominences ... 8 IO o 

CHEMICAL SPECTROSCOPES. 

The Student's Spectroscope, in Stained Cabinet (Fig. 5) ;6 10 o 

This Instrument has a prism of extremely dense glass of superior workmanship. 

The circle is divided, and reads with a vernier, thus dispensing with the inconvenience 

of an illuminated scale ; this arrangement possesses the very great advantage of giving 

angular measures in place of a perfectly arbitrary scale. 

The slit is also furnished with a reflecting prism, by means of which two spectra 

can be shown in the field of view at the same time. 

The Instrument is so arranged that, with a slight alteration of the adjustments, 

it can be used for taking the refractive and dispersive powers of solids or liquids. 

The Model Spectroscope (Fig. 6), with two prisms, in Polished Mahogany 

Cabinet 15 o o 

This Instrument has two dense glass prisms, two eye-pieces, rack motion to Tele- 
scope, and tangent screw motion to vernier. It will widely separate the D lines. 

Photographed Micrometer to either the one or two prism Spectroscope ... .1 15 o 

The Model Spectroscope, with four prisms, in superior Cabinet, with 

fittings and two eye-pieces 27 10 o 

This Instrument is guaranteed to show the Nickel line between the D lines in the 
solar spectrum. 
Browning's Automatic Action, extra ... ... 6 10 o 

LARGE TABLE SPECTROSCOPES. 

The Large Model Spectroscope, for the use of Physicists, made on the 

plan of the Gassiot Spectroscope, in Polished Mahogany Cabinet ... ^"38 10 o 
This Instrument has four very large dense glass prisms and Telescope with object- 
glasses i in. diameter, and 18 in. focal length, furnished with three eye-pieces. It 
will show two or three lines between the D lines in the solar spectrum. Any smaller 
number of the prisms can be used when desired. 

Dividing ditto on Silver, extra... ... ... . . ... 2 o o 

Browning's Automatic Action to the above 12 10 o 

The above Instrument, the circle divided on Silver to 10 seconds, with 
five prisms, four eye-pieces, and parallel wire Micrometer, for 
measuring the position of lines to TO&OO f an i ncn J the whole in 
Mahogany Case ... ... ... ... 55 10 o 

Browning's Automatic Action to the above ... 15 o o 

BROWNING'S UNIVERSAL AUTOMATIC SPECTROSCOPE. 

In this Instrument the prisms are automatically adjusted to the minimum angle 
of deviation for the particular ray under examination ; the position of the lines in the 
spectrum is measured by means of a Micrometer ; the revolution of this Micrometer 
screw adjusts the prisms automatically for the ray under measurement. The Instru- 
ment has six prisms, and by means of the reversion of the ray a dispersive power of 
12 prisms is obtained. By changing the position of one of the prisms, any dispersive 
power from 2 to 12 prisms can be used at pleasure, without deranging any of the adjust- 
ments of the Instrument. The Instrument is therefore applicable to every class of 
spectrum work either in the Laboratory or Observatory. 

Price of the Universal Automatic Spectroscope, with six prisms, best Filar 
Micrometer and Battery of 9 Eye-pieces, in Mahogany Cabinet com- 
plete (Fig. 7) ^65 o o 



58 

The same Instrument with light framework adapted for application to an 

Astronomical Telescope ... 70 o o 

Adapter, with movement of rotation, for attaching the Automatic Spec- 
troscope to a Telescope 6 10 o 

Adapter, with two slides, and mechanical motions, to enable the observer 
to set the Spectroscope at any degree of eccentricity to the Solar disc, 
so as to sweep either round the Sun's limb to search for prominences, 
or in the neighbourhood of the Chromosphere ... 15 o o 

Browning's Universal Automatic Spectroscope, 6 prisms, with the ray 
inverted, giving a dispersive power of 12 prisms, with the prisms and 
object-glasses of the Telescopes i in. diameter, and Telescopes 18 
in. focal length, Filar Micrometer, and 9 eye-pieces, &c., &c. ... 150 o o 



BROWNING'S AUTOMATIC SOLAR SPECTROSCOPE. 

Dr. Henry Draper's important discovery of the presence of oxygen in the Sun, 
described in Nature^ No. 409, August 30, 1877, will direct renewed attention to the 
Solar Spectrum. 

The Automatic Solar Spectroscope (Fig. 9) will show the Solar Spectrum with 
exquisite definition, and if attached to the eye-piece of a Telescope of 3 inches or more 
in diameter, it will show the form of the Solar Prominences. 

As this Spectroscope can be used with any dispersive power from 2 to 10 prisms, 
it can be arranged for observing the Spectra of the Stars and Nebulae. Without a 
Telescope it can be employed for any kind of work in Spectrum Analysis. 

By means of the reversion of the ray this Spectroscope gives a dispersive power 
equal to 10 prisms, and this dispersive power may be changed at pleasure by the 
observer. This Instrument is very light, and can be adapted to a Telescope as small 
as 3 inches in aperture. It is provided with a movement of rotation for searching for 
Solar Prominences. 

Complete in Case, with Eye-pieces ... 28 o o 

Rack Adjustment to the rotaiy motion, extra 2 10 o 

By means of the reversion of the ray this Spectroscope gives a dispersive power 
equal to 10 prisms, and this dispersive power may be changed at pleasure by the 
observer. It is well adapted for use with any Telescope, either a Reflector or Refractor, 
from 6 inches to 12 inches in aperture (Fig 10). 

Price complete, with Set of four Eye-pieces ,42 10 o 

Table Stand for using the Automatic Spectroscope above described, 
without an Astronomical Telescope for viewing the Spectra of 
Metals, Salts, or Gases I 15 o 

STAR SPECTROSCOPES. 
McCLEAN'S NEW STAR SPECTROSCOPE (PATENT). 

The Star Spectroscopes in general use are expensive and difficult to manipulate 
with. This arises from the fact that, in most instruments, the image of a star is 
required to fall within the jaws of a narrow slit, not more than ^^ inches in width, 
and an equatorially mounted telescope with clockwork is almost indispensable for using 
them. Star Spectroscopes of simpler construction, both with and without cylindrical 
lenses, have been made, but their performance has not been found satisfactory. In 
the Instrument contrived by Mr. McClean (Fig. n), exquisitely fine lines can be seen 
in the spectra of stars without the use of any slit. 



59 

Price of the Spectroscope, in Morocco Case 2 10 o 

Adjustable Slit and Convex Lens, to be used as an addition to McClean's 
Star Spectroscope, for showing the Fraunhofer lines in the Solar 
Spectrum, the bright lines of the metals, alkalies, gases, c., extra ... o 18 6 

McClean's Spectroscope, for showing both astronomical and chemical 

spectra, in Case complete... ... ... 3 7 6 

Rotating Telescope Nozzle, as used by Mr. McClean to carry the New 
Star Spectroscope, and an astronomical eye-piece, or two eye-pieces 

of different powers .. .~ I 15 O 

This contrivance gieatly facilitates the use of McClean's Star Spectroscope, the 

Spectroscope being carried by one arm, and an eye-piece for observing by the other. 

Any star seen in the eye-piece can in an instant be examined with the Spectroscope ; 

or a low power may be used in one arm for finding an object, and a high power for 

observing it, to be changed rapidly without unscrewing. 



STAR SPECTROSCOPES. 

Star Spectroscope, with i prism, packed in Polished Mahogany Case ... j8 8 o 

Star Spectroscope, with 2 prisms, reflecting prism, to show two spectra 
at once, and Micrometer Measuring Apparatus for Mapping Spectra, 
packed in polished Mahogany Case (Fig. 12) ... ... 14 o o 

Insulated Spark Apparatus attached to mirror, for obtaining the spectra 
of the metals for comparison, adapted to either of the above Instru- 
ments ... ... ... ... i i o 

Star Spectroscope of the best construction, with adjustable reflecting prism 
and mirror, with finest object-glass, Micrometric Apparatus for Measur- 
ing the Lines of the Spectrum to TO&OO of an inch, extra eye-piece, 
and ivory tube to reader of vernier, as made for Dr. W. Huggins, 
F. R.S., packed in polished Mahogany Case, with Insulated Spark 
Apparatus complete (Fig. 12) ... ... ... ... 21 o o 

The Amateur's Star Spectroscope, in Mahogany Case (Fig. 13) ... ... 400 

Browning's Bright Line Micrometer, for measuring the position of bright 

lines in the spectra, adapted to the above ... ... ... ... 2 5 o 



INDUCTION COILS, 

For working Induction Titles or obtaining the Spectra of the Metals bv the aid of the 

Electric Spark. 

Mr. JOHN BROWNING begs to inform scientific gentlemen that the adoption of an 
improved method of winding Induction Coils has enabled him to increase their 
efficiency and reduce their cost. Every Coil is guaranteed to give the length of spark 
named. 

FOR WORKING INDUCTION TUBES. 

Induction Coil, to give a |-in. spark in dry air, with i quart-size Bunsen's 

Cell (Fig. 14) 3 5 o 

Induction Coil, to give a i-in. spark in dry air, with I quart-size Bunsen's 

Cell 5 10 o 

Induction Coil, to give a li-in. spark in dry air, with 2 quart-size Bunsen's 

Cells 6 15 o 



6o 

FOR SPECTRUM ANALYSIS. 

Induction Coil, to give a 2^-in. spark in dry air, with 3 quart-size Bunsen's 

Cells ;io o o 

Induction Coil, to give a 3^-in. spark in dry air, with 3 quart-size Bunsen's 

Cells 12 is o 



Induction Coil, to give a 4^-in. spark in dry air, with 5 quart-size Bunsen's 

Cells 1600 

Induction Coil, to give a 6-in. spark in dry air, with 6 quart-size Bunsen's 

Cells ... .. 22 o o 

Where the trouble of charging Bunsen's Cells is objected to, or it is desirable to 
avoid the nitrous fumes they give off, Bichromate Batteries can be supplied. These 
Batteries are very cleanly, but not nearly so powerful as the Grove's or Bunsen's 
Batteries, so that the Coils will not work with their full power when they are used. 

Bichromate Battery, with 4 Cells, arranged so that, by using a winch, the elements 
may be removed from the exciting solution at pleasure. These Batteries may be used 
many times without re-charging. 

Bichromate Battery, 4 large Cells, lifting elements ^4 10 o 

Bichromate Battery, 6 large Cejls, lifting elements 6 10 o 

BROWNING'S SPARK CONDENSER. 

This contrivance is designed to replace the Leyden Jars which are generally used 
with Induction Coils to increase the temperature of the spark when it is required for 
spectrum analysis. The apparatus consists of an arrangement of ebonite plates coated 
with tinfoil, and enclosed in a mahogany case. Any amount of surface may be used 
at pleasure by rotating the circle on the top of the case. Unlike the Leyden Jar, 
the action of the apparatus is not affected by damp. A very convenient arrangement 
for holding the metals of which the spectra are required, screws on to the lid of the 
case, and when not in use packs inside the lid (Fig. 15). 

Becquerel's Apparatus for ebtaining continuous spectra from solutions of salts of 
the metals, is attached when required. 

Price of the Spark Condenser for Coils, giving a 2^-inch spark, with levers 

for changing the number of Plates ... ... ... 2 15 o 

Price of the Spark Condenser for Coils up to 5-inch spark, with levers for 

changing the number of Plates ... ... ... ... 3150 

Price of the Spark Condenser for Coils giving 6-inch to 8-inch spark ... 9 10 o 

Becquerel's Apparatus extra ... ... ... o 15 o 

BESSEMER SPECTROSCOPES. 

Either of the Direct-Vision Spectroscopes, enumerated on pages 12 and 13, are well 
adapted for viewing the Bessemer flame, and great numbers are in constant use for 
this purpose in all parts of Europe, the highest power being best adapted for the pur- 
pose ; but Mr. Browning has devised a special Instrument of very great dispersive 
power, having an eye-piece of large field, which shows the whole of the spectrum, 
giving admirable definition in all parts of the field. 

Direct-Vision Bessemer Spectroscope, with 10 prisms, complete in Maho- 
gany Case 1210 o 

The Bessemer Spectroscope (Fig. 16) is a much more powerful Instrument. The 
Telescope has a motion between pivots, near the top of the case. There are cross- 
wires in the field of view to assist the observer in concentrating his own attention, 
or directing that of others, to any particular line in the spectrum. This Instrument 



6i 

is so contrived that the back of the observer is turned to the brilliant flame, which 
renders vision much easier. A condensing lens, shown in the engraving, which works 
on a rod in front of the slit, can be fixed so as to produce an image of the flame on 
the slit ; by moving the Instrument about on the hinged joint and swivel, the spectrum 
of any portion of the flame can be examined at pleasure. The slit is protected from 
the action of dust by means of a glass cover, and when the Instrument is not in use it 
can be unscrewed and enclosed in the box. 
Price of the Instrument complete, with Stand ,25 o o 

BROWNING'S ELECTRIC REGULATORS. 

Small Electric Regulator, with parabolic reflector (Fig. 17). This Regu- 
lator will give a powerful and steady light, with from 10 to 20 quart- 
size Grove's or Bunsen's Cells. Price ... ... 2 5 

Small Electric Regulator (Fig. 18), without reflector, for use in the Lantern, 
with adjustment for keeping the points of the burning carbons at one 
height, or separating them to any required distance. This adjustment 
is indispensable for projecting the spectra of burning metals on a screen. 
With 20 quart-size Bunsen's Cells, this Regulator will illuminate a 
lo-feet disc. Price 2 15 o 

Parabolic Reflector, if required, extra 066 

In these Regulators, described in p. 38, both carbons are moved by the electricity 

of the battery employed (without the aid of clockwork) ; the light remains uniform in 

height and more steady in action than any of the expensive Regulators previously 

introduced. 

Medium-size Automatic Electric Regulator. This Lamp works well with 
from 20 to 30 pint Grove's Cells, or the same number of quart 
Bunsen's (as Fig. 19). Price & 10 O 

Parabolic Reflector, extra I 15 o 

Large-size Automatic Regulator. From 25 to 50 quart Grove's Cells, 
or the same number of 2-quart Bunsen's, should be used with this 
Lamp (Fig. 19). Price 9 9 o 

Parabolic Reflector 220 

Carbon Rods, for burning in small Lamp per foot o I o 

Ditto ditto per dozen feet o 10 o 

Large Rods, for burning in the large Lamp per foot o I 6 

Ditto ditto per dozen feet o 15 o 

Carbon Cups, for holding metals to obtain their spectra, small, per dozen o 10 6 

Large ditto ditto ditto ditto o 12 o 

GALVANIC BATTERIES. 

Grove's Cells pints (reputed) u/, quarts (reputed) Q 14 o 

Bunsen's Cells ... ... pints 5/6, quarts 6/6, 2 quarts 090 

Varnished Oak Trays for 6 cells 6/, for 10 cells o 10 6 

Bichromate Battery, 4 lifting cells -. large size ,4 10, 6 cells 6 10 o 

Insulated Copper Wire per yard, 2d. to 019 

Porous Cells ... per dozen ... ... ... pints io/, quarts o 14 o 

Stoneware Cells... ,, ... pints I2/, quarts i6/, 2 quarts I o o 

Carbons ,, ... pints I2/, quarts i6/, 2 quarts o 18 o 

Zincs ,, ... pints I2/, quarts i8/, 2 quarts 140 

Bichromate of Potash . ... 



62 

BROWNING'S SPECTRUM APPARATUS, FOR SCREEN 
EXPERIMENTS. 

JOHN BROWNING has great pleasure in introducing to the notice of Lecturers and 
others a New and Complete Set of Apparatus, at a very low price, for projecting the 
spectra of metals, or the absorption bands of liquids, on a screen. The Apparatus 
comprises an Automatic Electric Lamp and Lantern, with slit, a Bunsen's battery 
of 20 quart-size cells, and trays, mounted focussing lens, bisulphide of carbon prism 
and stand, platform for the whole, and packing case ,^ 2 IO 

An inner case can be supplied, which fits into the body of the Lantern, con- 
tains the Electric Lamp (Fig. 18) in packings, a set of chemicals which give the most 
brilliant spectra, and a supply of carbon rods and carbon crucibles ... .4 o o 

Price of the Complete Set of Spectrum Apparatus, packed, 16 IDS. 
Nozzle with lenses and 3^-inch condensers, for showing diagrams or views 

on screen, extra 2 15 o 

Nozzle with 4i-inch condensers, extra 4 10 o 

SCREEN SPECTRUM APPARATUS. 

JOHN BROWNING begs to inform Spectroscopists that he has just introduced a new 
metal body Electric Lantern, with an Electric Regulator specially adapted to the 
same, for showing diagrams, and exhibiting spectra on a screen j thoroughly efficient 
in action, and yet economical in price. 

The Automatic Regulator is of the best construction, exactly similar to his now 
well-known large Regulator, but arranged to burn with a smaller number of cells. 
Price of the Electric Lantern, for medium-size Lamp, with metal body, 
japanned bronze green, with two nozzles, interchangeable one for 
showing diagrams, with 3i-inch condensers, the other for spectrum 
analysis (Fig. 21) 7 IO 

MEDIUM-SIZE AUTOMATIC ELECTRIC LAMP 

FOR THE ABOVE LANTERN. 
This Lamp works well with from 20 to 30 pint Grove's cells, or the same 

number of quart Bunsen's (Fig. 19) ... ... ] 10 o 

LARGE ELECTRIC LANTERNS. 

Improved Lantern, the body of brass, bronzed, with two nozzles, specially 
arranged for exhibiting spectra or diagrams on the same screen with- 
out shifting the Lantern or re-arranging the apparatus^ with 3v,-inch 

condensers (Fig. 22) il IO o 

Ditto, ditto, larger size, and 4^-inch condensers ... 16 10 o 

Large Electric Lamp (Fig. 18) for either of the above Lanterns ... ... 9 9 o 

VERY COMPLETE SET OF 
SCREEN SPECTRUM APPARATUS. 

Improved Electric Lantern, with 4^-inch condensers, the body of brass, bronzed, 
with two nozzles specially arranged for exhibiting spectra or diagrams on the same, 
screen, without shifting the Lantern or re-arranging the apparatus. Large-size 



63 

Electric Regulator for the above, to work with from 25 to 50 Grove's or Bunsen's 
cells. Two extra-size Bisulphide of Carbon Prisms. Prism Stand and Cover, 
adjustable for height with clamp motions. Large Condensing Lens on Brass Stand, 
adjustable for height. Revolving Diaphragm. Rotating Carbon Holder. Maho- 
gany Case containing set of Metals and Salts for burning in the Electric Arc, with 
carbon crucibles, pliers, and 6 feet of carbon rod, &c., for the large Regulator. 
Battery of 40 quart Bunsen's Cells in four varnished Oak Trays. 

Price of the set of Apparatus, complete ^50 o o 

Browning's New Lantern Microscope, adapted to the above, for showing 

Microscopic Objects on a screen ... ... 5 10 o 

Set of Metals and Salts for burning in the Electiic Arc, and showing their 
spectra, with carbon crucibles, pliers, and 5 feet of carbon rod, in 
Mahogany Case ... ... ... ... ... 2 10 o 

SETS OF APPARATUS FOR PRODUCING THE ELECTRIC 

LIGHT. 

No. i. 

Small-size Electric Lamp, with Reflector (Fig. 17) .. ... 2 5 o 

20 quart Bunsen Cells, at 6/6 each ... ... ... ... 6 10 o 

2 Varnished Oak Trays, at 10/6 each ... ... ... I I o 

Carbon Rod per foot I/, per dozen feet o 10 o 

No. 2. 

Medium-size Automatic Electric Lamp, without Reflector (Fig. 19) ... 7 10 o 

Parabolic Reflector, extra 220 

30 quart Bunsen's Cells, at 6/6 each .. 9 15 o 

3 Varnished Oak Trays, at 10/6 each I 11 6 

Carbon Rod ... ... ... per foot 1/6, per dozen feet o 15 o 

No. 3. 

Large Automatic Electric Lamp (Fig. 19) ... ... ... 990 

Parabolic Reflector, extra ... ... ... ... ... ... ... 220 

50 quart Bunsen's Cells, at 6/6 each ... ... ... .. ... ... 16 5 o 

5 Varnished Oak Trays, at 10/6 each ... ... ... 212 6 

Carbon Rod per foot 1/6, per dozen feet o 15 o 

SPECTRUM APPARATUS FOR THE MICROSCOPE. 

Price of the Micro-Spectroscope, complete with Micrometer ... ... 8 5 o 

The Sorby-Browning Micro-Spectroscope, with rack-motion to eye- piece 

(Fig. 24), without Micrometer ... ... ... ... 6 O O 

Browning's Bright-Line Micrometer, for measuring the position of bright 

lines in Spectra, adapted to the above (Fig. 24) 250 



6 4 

Case for Spectroscope, with Racks for Cells and Tubes ^o 15 o 

Sorby's Tubes per dozen 026 

Sorby's Wedge Cells per dozen 060 

Specimens in Sealed Tubes for showing the Bands, each ... o I 6 

For List of Specimens for the Micro- Spectroscope ', see page 49. 
Price of the Specimens Class I., Class II., 10/6 ; Class III., 6/6. 

The Amateur's Micro-Spectroscope, with Achromatic Lens and Reflecting 
Prism, to show Two Spectra at the same time, for the purpose of 
comparison ... ... 2 15 O 

Mahogany Case for the above 050 

TO LECTURERS ON SCIENCE. 

JOHN BROWNING begs to announce that he has prepared, with peculiar care, a 
great number of Diagrams, principally Photographs, to illustrate recent discoveries 
in Spectrum Analysis and other branches of Observational Astronomy. These 
Slides can be had either plain or exquisitely coloured. 

Prices, Plain Q 3 6 

Coloured ... ... ... from 4/6 to o 10 6 

Photographs of Microscope Objects for the Lantern, each 036 

For List of Subject 's, see end of Spectroscope Catalogue. 

DENSE GLASS PRISMS. 

Prisms of extra dense flint, of very superior quality, of 45 or 60 degrees, 

with accurate plane surfaces, f inch ^o 15 

Prisms, i in., 2O/; ij in., 30/5 \\ in., 6o/; T.\ in., go/; 2f in 600 

Prisms, 3 in., ;i5; 4 in. by 3 in 30 o o 

Prisms of the above sizes, of the densest flint made, 25 per cent, extra. 

BISULPHIDE OF CARBON PRISMS. 

Bisulphide of Carbon Prisms, large size o *5 

Bisulphide of Carbon Prisms, extra large size o 18 6 

Bisulphide of Carbon Prisms, with Parallel Glass Sides, Browning's im- 
proved method of Mounting in Metal Frames each 1 15 O 

Prisms of other Angles to order. 

HOLLOW GLASS PRISMS. 

Hollow Glass Prisms, with movable sides in metal frames, for taking the 
refractive index or dispersive power of a liquid, angles of 60, i in; 
faces, to replace the usual dense glass prism on a Spectroscope at 
pleasure each 18 6 

Hollow Glass Prisms, with perfectly plane and parallel sides, without 

metal frames, warranted to give the finest definition from ^3 3/ to 660 



65 
SPECTROGRAPHS. 

Beckley's Spectrograph, for Mapping out Spectra (Fig. 26) 10 o o 

Beckley's Spectrograph, larger... ... 15 o o 

Colonel Campbell's Automatic Micrometric Spectrograph (Fig. 27) ... 16 10 o 



SUNDRY SPECTROSCOPIC APPARATUS. 

Hollow Cells, with one side formed of a Prism, for holding Solutions for 

examining Absorption Bands ... ... ... ... i I o 

Large ditto, for projecting Spectra on Screen ... ... I n 6 

Extra power Eye-pieces ... ... 12/6 to I o o 

Bunsen's Burners ... ... ... ... ... ... ... 3/6 to 050 

Adjusting Clip, on stand, to hold platinum wire ... ... ... 036 

Browning's Improved Spectroscope Lamp, containing burner and clip on 

a single stand, complete (Fig. 28) ... ... ... ... ... o 12 6 

Brass Stand, superior finished ditto ... ... ... ... 1150 

Leyden Jars ... ... . . ... ... ... ... from 3/6 to 2 2 O 

Insulated Spark Apparatus, on brass stand, with 2 Dischargers, for 

obtaining the Spectra of Metals and Gases ... ... ... ... Il86 

Set of 13 chemically pure Metals, in Mahogany Cabinet, for Spectrum 

experiments... ... ... ... ... ... ... ... ... o 18 6 

Vacuum Tubes, prepared for showing the beautiful Spectra of various 
Gases Nitrogen, Hydrogen, Oxygen, Carbonic Acid, Ammonia, 
Sulphuric Acid, Olefiant, Chlorine, Bromine, Iodine, Coal Gas, 
^Ether Vapour, Turpentine Vapour, Petroleum Oil Vapour, and 

Water Vapour each, 5/6, 7/6, and 086 

Set of Salts best adapted for showing Chemical Spectra, stoppered 

bottles, in case 076 

Metallic Thallium and othtr Chemicals to order. 

Platinum Wire, for usr with the Spectroscope per foot o I o 

Plucker's Tube Hohki, lor holding a single Plucker's Tube 150 

Plucker's Tube Holder, for holding 7 tubes 33 

Insulated Spark Apparatus, on brass stand, for obtaining the Spectra of 

Metals 15 

Lockyer's Insulated Spark Apparatus, with vertical and horizontal rack 

motions ... ... ... ... ... ... I 15 

Lockyer's Insulated Spark Apparatus, with 7 Dischargers, for obtaining 

the Spectra of 7 Metals without altering the Apparatus (as Fig. 29)... 4 o o 
Lockyer's Insulated Spark Apparatus, with 14 Dischargers (Fig. 29) ... 6 10 o 
Reflecting Mirror for following the motion of the Su.n, so as to investigate 
or map the Solar Spectrum. This is a rectangular mirror of large 
size, mounted on an axis, and provided with endless screw motions in 
altitude and azimuth, and Hook's joints, with long handles, which 
can be carried to the foot of the Spectroscope when the mirror is placed 

outside of a window. Price ... ... 8 IO O 

E 



66 



The following Prices are Nett for Cash; Half-price allowed for 

returned Packages, if Carriage Paid. 
Orders should be accompanied by a Remittance. 



REDUCED LIST OF PRICES OF MIRRORS, 

Mounted and Unmounted. 



JANUARY, 1883. 



SILVERED GLASS TELESCOPES AND SPECULA. 

SILVERED GLASS SPECULA, UNMOUNTED. 

WITHOUT CELLS. 

The performance of these Specula will be guaranteed ; they will bear a power of 100 to the inch on 
suitable objects, and under favourable conditions of the atmosphere. 



4ft 



9 

ioi 

u| 

13 





4 


j 
o 


o 


bcus 


6 


'5 






... 14 


IO 


o 


... 


20 










... 30 


o 


o 




40 








... 


... 50 


o 







... 65 


o 







... 100 









or 6 
8 
8 

9 

10 
10 

IO 

15 

PRICES OF 

SILVERED GLASS SPECULA ASTRONOMICAL 
TELESCOPES, ON ALT- AZIMUTH STANDS. 

3^ inch Speculum, 3 ft. focus, mounted in metal, on metal alt-azimuth 
stand, with two eye-pieces, 50 to 150 ... ... 

4i inch Speculum, 5ft. focus, mounted on a stand, which can be changed 
from alt-azimuth to parallactic, so that the stars can be followed 
with one motion, with endless driving screw, and Hook's joint 
and two eye-pieces, IQO to 200 

6J inch Speculum, 6 ft. focus, on alt-azimuth stand, with quick and slow 
fine screw motions, and three eye-pieces, loo to 450 

8^ inch Speculum, 8 ft. focus, mounted as above, with three eye-pieces, 
10010500 

9i inch Speculum, 8 ft. focus, as above, with four eye-pieces, 100 to 600 

io inch Speculum, 9 ft. focus, ditto 



^10 o o 



22 o o 



SILVERED GLASS SPECULA ASTRONOMICAL 
TELESCOPES. 

EQUATORIALLY MOUNTED IN A SUPERIOR MANNER. 

inch Speculum, 5 ft. focus, equatorially mounted (angle for latitude to 
order), with 6 inch hour circle reading to 5 seconds, and declina- 
tion circle reading to I minute, two eye-piece?, 100 and 300 
(Fig- 7) ........................... ^45 o 



6 7 

6J inch Speculum, 6 ft. focus, with 12 inch hour circle reading to 
5 seconds, and declination circle to i minute, three eye-pieces, 
i oo to 450, rotating hour circle ... -., ... ... ... ^85 o o 

8i inch Speculum, 8 ft. focus, mounted as above ... 112 o o 

92 inch Speculum, 8 ft. focus, with four eye-pieces, 100 to 600 ... ... 145 o o 

i o inch Speculum, 9 ft. focus ... ... ... ... ... ... 170 o o 

\2\ inch Speculum, with extra eye-pieces ... ... ... ... ... 225 o o 

13 inch Speculum, with ten eye-pieces, including Achromatics and 

Kellner ... ... ... ... ... ... ... ... ... 335 o o 

15 inch Speculum, 10 ft. focus, with 16 inch hour circle, reading to five 
seconds, and declination circle to one minute, with three Huy- 
ghenian eye-pieces, one Kellner, and six Browning's improved 
Achromatic eye-pieces, powers ranging from 60 to 600 diameters. 
Position Micrometer, with two verniers divided on silver, and 
reading to single minutes, with clock-work driving apparatus 
complete... ... ... ... ... ... ... ... ... 600 o o 

Clockwork Driving Apparatus, to 8i, 9^, or io inches ... ... ... 38 o o 

Ditto ditto 12^ or 13 inches... ... ... ... 48 o o 

SILVERING GLASS SPECULA. 



4i inches ... ... ... ^"o 5 o 



64- 



9i 



O IO O 

O 12 6 

15 o 

1 O O 



13 inches ... ;i 10 o 

15 > 200 

Silvering Plane Mirrors ... 026 
Silvering above 2i inches 

in the minor axis 016 



All Charges incurred for Carriage "will be extra. 

ASTRONOMICAL EYE-PIECE HUYGHENIAN 
CONSTRUCTION. 

Xos. i and 2, magnifying 65 and 85 ... ... ... o 15 o 

,, 3, 4, and 5, ,, 125, 200, and 250 i o o 

,, 6 ,, 400 150 

,, 7 ,, 600 I 10 o 

ACHROMATIC EYE-PIECES. 

These Eye-pieces have a rather limited field, but their performance with reflecting telescopes 
particularly on planets, is very superior to Huyghenian. 



A Magnifying 86 ... i 2 6 E Magnifying 306 
B ,, ' 144 ... i 10 o F 450 
C ,, 208 ... i 15 o j G ,, 600 
D ,, 250 ... i 15 o | H ,, 840 

LARGE FIELD EYE-PIECES. 
Very low power Comet Eye-piece, magnifying 35 .. 


2 
2 
2 


15 



5 

10 

n 


O 
O 
O 

o 
o 


Kellner Eye-piece, with field of 50 minutes, for clusters or nebuloe, 
ma.gnifyin ' 60 .. 


I 


7 


6 


Ditto, with field of 35 minutes, for clusters, nebulae, or the moon, 
magnifying 85 


I 


7 


6 


Day-power Eye-pieces, erect ... ... ... ... ... i o o to 


I 


in 


o 


The power of all the Eye-pieces has been calculated on an object-glass, or mirror 
focus. 


of s 


ix 


feet 






68 

SOLAR EYE-PIECES. 

Single reflecting Prism, mounted, for viewing the sun or moon, with 

two shade heads, in mahogany case ... ... ... ... ... .3 10 o 

Ditto, with two Prisms, arranged for single reflections, for viewing 

the sun only ... ... ... ... ... ... ... ... Soo 

TRANSIT EYE-PIECES. 
Transit Eye-pieces, with fine webs or wires ... ... ... ... ;i 5 

Ditto, with 7 webs and higher powers ... ... 1 10 o to I 15 o 

PARALLEL WIRE MICROMETER. 
Micrometer for measuring to a fraction of a second ... ... 6 to 1 1 1 1 o 

POSITION MICROMETER. 

Parallel Wire Micrometer, with position circle and two vcrnier<, 

reading to single minutes ... ... ... ... /"n o o 

Ditto, superior make, divided on Silver ... ... ... ... .. 13 15 

Ditto, divided on Platinum 17 o o 

Extra Eye-pieces, 15/each. 

Browning's Double-image Micrometer 8 10 o 

BARLOW'S LENS. 

This is an achromatic combination of a negative focus ; on inserting it behind any 
eye-piece (that is, between the eye-piece am' the object-glass) the power of the 
eye-piece is increased from one-third to one-half; at the same time the introduction 
of this Lens, especially when using Huyghenian eye-pieces, greatly improves the 
performance of reflecting telescopes, especially on bright stars. 
Price of the best quality, i 2s. 6d. 

SMOKE-COLOURED GLASS WEDGES, corrected for re- 

fraction for intensifying the marks on the Moon or Planets i 20 

NEUTRAL TINT WEDGES, for observing the Sun 120 

DIVIDED LENS DYNAMETER, for measuring accurately the 

power of Eye-piece?, new movement for separating the Lenses ... 440 

ASTROMETER. 
Knobel's Astrometer, a simple and efficient instrument for determining 

Star Magnitudes 12 10 o 

PERFECT PLANES, UNMOUNTED, 

PERFORMANCE UNDER ANY TOWER GUARANTEED. 

I inch in the minor axis of the Ellipse ... ... L^ c 



I0 



3 5 



6 9 

Prepared Pad for polishing Specula, in bottle, 2s. 6d. 

An Illustrated Catalogue of Spectroscopes sent post free for 7 stamps. 

Microscopes 7 

ASTRONOMICAL WORKS. 

A New Star Atlas for the Observatory 12 Maps with letter-press 

by K. A. PROCTOR, B. A., F.R.A.S /o 15 o 

Descriptive Astronomy, by G. F. CHAMBERS, F.R.A.S. ... ,.. I 8 o 

Celestial Objects, by the Rev. T. W. WEBB, M. A., F.R.A.S. 076 

Elementary Astronomy, by J. N. LOCKYER, F.R.A.S 056 

Saturn and its System, by R. A. PROCTOR, B.A., F.R.A.S. ... ... o 14 o 

Half-Hours with the Stars, by R. A. PROCTOR, B.A., F.R.A.S. ... 050 

Half-hours with the Telescope, by R. A. PROCTOR, B. A., F.R.A.S. ... 026 

Sun Views on the Earth, by R. A. PROCTOR, B.A., F.R.A.S o 5 o 

Other Worlds than Ours, by R. A. PROCTOR, B.A., F.R.A.S., Second 

Edition ... ... ... ... ... ... ... ... ... o 10 6 

Handbook of the Stars, by R.A. PROCTOR, B. A., F.R.A.S 050 

The Sun, by R. A. PROCTOR, B. A., F.R.A.S o 14 o 



oroHiiN" 

B tit ul anir |pbgsicul instrument I 

To Her Majesty's Government; The Royal Society ; The Royal 

Observatories of Greenwich and Edinburgh; and the 

Observatories at Keiu, Cambridge, &*c.>. &*c. 

63, STRAND, LONDON, W.C. 



PRIZE MEDAL, 1862. 



ESTABLISHED 10O YEARS, 



MICROSCOPES, TELESCOPES, SPECTROSCOPES, OPERA GLASSES, SPECTACLES, ETC. 



BROWNING'S ANEROIDS, 



EXACT SIZE. 




"THE ANEROID IS THE BEST 
WEATHER-GLASS MADE." Colonel 
Sir HENRY JAMES'S "Treatise on 
Meteorological Instruments.'' 



Watch-form Aneroid, in Gilt or 

Nickelised Case, 2 10s. 
Best \Vatch-form Aneroids, compen- 
sated for temperature, and constructed 
expressly for measuring heights, with 
scale of altitudes, i$, if, or 2 inches 
diameter, 

4 4s. and 5 5s. 



I>est Aneroid, in Carved Oak Frame, 
with Thermometer, various patterns, 
Chased Dial, 5 inches in diameter, 

From 4 to 4 15s. 



Illustrated Catalogue of 

Meteorological Instruments 

sent Post Free. 



JOHN BROWNING, 

Optical and Physical Instrument 
Mdker 1o //.Y]/! Government) 
the Royal Society, 1hc Royal 
Obserratorics of Greenwich and 
Edinburgh) and the Observa- 
tories of Kcu^ Cambridge, Dur- 
ham, Uirecht, Melbourne, 6-r., 
c>r. 

63, STRAND, LONDON, W,C, 

Established One Hundred 1 'ears. 



THE- NEW SELF-REGISTERING ANEROID, 




This instrument is extremely simple and hardy in construction. It has neither 
spring nor chain, the motive power being obtained from Seven Vacuum Chambers ; 
these are attached by levers to the arm which registers the height of the Barometer on 
the diagram, by means of a pen. The drum revolves once in a week, motion being 
given to it by an eight-day clock movement, which is out of sight inside the drum. 

The diagrams Jrom this instrument are not only interesting, but much more valuable 
than those given by an ordinary Barometer ; for instance, if an observer, after setting 
a Mercurial Barometer at 30 inches, at 8 o'clock in the evening, looks at the Barometer 
at 8 o'clock the following morning, and finds that it registers 29*7, he will conclude 
that the Barometer has fallen] 3.loths., and is probably falling at that time, but the 
Self-Registering Aneroid might show him that the Barometer had fallen 5.ioths in 
the night, and had risen 2. loths since. When a storm of wind or rain is experienced, 
observers who consult the Barometer only at long intervals will at times remark that 
the instrument gave no indication of the storm, yet with the Self- Registering Aneroid 
this would have been found a mistake, for the Barometer had probably fallen and 
risen again in the interval, and it is well known that a rapid rise after a fall indicates 
a stronger gale than the fall itself. 




{Sr.iall portion of a Weekly Diagram.} 

The price of the New Self- Registering Aneroid Barometer, with Fifty-two 
diagram papers, is ... ... ... ... ... ... ... .. 

The above Instrument with glass on three sides of the case, and Ther- 
mometer ... ... ... ... ... 8 o 

Packing Box o I 



10 O 



J O 



I 3XT C3-, 



3XT 10 IFt O "W 

aitb -jphtmcal nsirontcnt 

To Her Majesty's Government ; the Royal Society ; the Royal Observatories of Greenwich 

and Edinburgh ; and the Observatories of Ke^u, Cambridge, drv., &>c. 

63, STRAND, LONDON, W.C. 



72 

BROWNING'S MICROSCOPES, 




The Model Microscope, with Rack and fine Adjustments to body, with 
Axis for inclination, one Eye-piece, Concave Mirror, and i-inch and 
-inch Object-glasses $ IO 



List of Microscopes sent Free. 

Illustrated Catalogue of Microscopes for Seven Stamps. 
JOHN BROWNING, 63, Strand, London, W.C. 

ESTABLISHED ONE HUNDRED YEARS. 



73 



BROWNING'S NEW BINOCULARS, 




The "PANERGETIC" Opera, Field, and Race Glass, 

For general use, brilliant light, extensive field of view, and sharp definition* 
NOTICES OF THE PRESS. 

" Brings out figures with marvellous distinctness, and has a very large field of view, and so many 
advantages over the other Binoculars that we have seen, that we confidently award very high praise 
indeed." Popular Science Review. 

" Exhibits objects with remarkable brightness and sharpness." The Observer. 

"A wide extension of the field of view is attained, while even in misty weather objects are 
exhibited with wonderful clearness." Naval^and Military Gazette. 

" A very extensive field of view is obtained, and objects in the distance arc shown with great 
distinctness." English Churchman. 

Price 4 IOs. 




The "EURYSCOPIC" Opera, 2 2s. 

For Ike Theatre, has the largest field of view, giving delightfully easy vision. 
ILLUSTRATED LIST FREE BY POST. 

ACHROMATIC OPERA GLASS in Case, from 10s. 6d. 
J O H N B R O W N ING, 

Optical and Physical Instrument Maker to H.M. Government, the Royal Society, the 

Royal Observatories of Greenwich and Edinburgh, and the Observatories 

of Kew, Cambridge, Durham, Utrecht, Melbourne, &c. 

G3, STRAND, LONDON, IV. C. 

ESTABLISHED ONE HUNDRED YEARS. 



74 

DRY PLATE PHOTOGRAPHY, 

BROWNING'S TOURIST'S POCKET CAMERA. 




Mahogany Camera, leather bellows body, with three double dark backs 

to take six dry plates 4! by 3^ inches, in case complete ... ... /,'j o o 

Tripod Stand for above o 15 o 

Quarter-plate extra quick Rectilinear Lens, fitted inside the Camera, so as 

to take up no extra space 200 

SET OF APPARATUS. 

Complete set of Photographic Apparatus, consisting of a Mahogany Camera, 
with bellows body, and one dark back, to lake two dry plates 4.} inches by 3^ 
inches, Landscape Lens, Camera Stand, one dozen Chapman's Sensitive Dry Plates, 
Developer, and fixing Solution and Chemicals, three Ebonite Trays, Non-Actinic 
Lantern, and Focussing Cloth, complete, in case, 3 8s. 6d. Full instructions for 
exposing and developing the dry plates are enclosed. 

Sole London Agent for Chapman's Celebrated Dry Plates. 
Descriptive Catalogue sent free. 



Optician to Her Majesty's Government, 
63, STRAND, LONDON, W.C. ESTABLISHED 100 YEARS. 



THE " MANCHESTER" GELATINE PLATES, 

Price from i 5 per Dozen. 



A. Rapid Plates for Studio Work and Instantaneous Effects. 

13. Slow Plates for ordinary out-door or any use requiring very great latitude in 

exposure. 

C. Opal Plates for Positives by Contact Printing or Enlargements, &c. 
D. Gelatine and Albumen : a special Plate for Lantern Transparencies. 

Particulars of sizes, and Prices of all the above Plates, POST FREE. 

J" O 3E3I ZKT 3E3 IFi O ^7V 3XT X jST 3- , 

63, STRAND, LONDON, W.C. 



FOURTEEN DAY USE 

RETURN TO DESK FROM WHICH BORROWED 



This book is due on the last date stamped below, or 

on the date to which renewed. 
Renewed books are subject to immediate recall. 



ras^ 



REC'D LD 



'64-SPM 



2()Mar58MF 



REC'P LD 




RECTO 




LD 21-100m-2,'55 
(B139s22)476 



General Library 

University of California 

Berkeley