Galvanic Battery, to galvanize the plate, if it is too imperfect to be
used without, previous cleaning it, as directed in the last chapter.
Rottenstone,
Tripoli, which is too often dispensed with.
Rouge, or lampblack--the first being most preferable. The English
operators mix the two together.
Prepared cotton Wool, or Canton flannel. If the first is used, it
should be excluded from the dust, as it is not so easily cleansed as
the latter.
The plate is secured, with its silver side upward, to the block, by the
means described on page 58--having previously turned the edges backward
all around. The amount of cleaning a plate requires, depends upon the
state it is in. We will suppose one in the worst condition; dirty,
scratched, and full of mercury spots, all of which imperfections are
more or less to be encountered. The mercury spots are to be removed by
burning the plate. To do this hold the plate over the flame of a
spirit lamp, more particularly under the mercury spots, until they,
assume a dull appearance, when the lamp is to be removed, and the plate
allowed to cool, after which it is attached to the block.
Place the block upon the swivle, and hold it firmly with the left hand;
take a small knot or pellet of cotton, or, if you like it better, a
small piece of canton flannel--wet it with a little diluted nitric
acid; then sift some finely prepared rottenstone--Davie's,* if you can
get it--upon it, and rub it over the plate with a continual circular
motion, till all traces of the dirt and scratches are removed; then
wipe off the rottenstone with a clean piece of cotton, adopting, as
before, a slight circular motion, at the same time wiping the edges of
the plate. Even the back should not be neglected, but throughly
cleansed from any dirt or greasy film it may have received from
handling.
* Sold by E. Anthony.
When this is thoroughly accomplished, mix a portion of your tripoli
with the dilute nitric acid, to the consistence of thick cream. Then
take a pellet of cotton and well polish the plate with this mixture, in
the same manner as with the rottenstone. Continue the process till, on
removing the tripoli with a clean pellet, the plate exhibits a clear,
smooth, bright surface, free from all spots, or scratches. Any remains
of the acid on the plate may be entirely removed By sifting on it a
little Drying powder, and then wiping it carefully off with a fine
camels hair brush, or duster. The finishing polish is now to be given.
For this purpose the rouge--or a mixture of rouge and lamp-black, in
the proportion of one part of the former to seven of the latter--is
used. It should be kept either in a muslin bag, or wide mouth bottle,
over which a piece of muslin is tied--in fact, both the rottenstone and
tripoli should be preserved from the dust in the same manner. With a
little of this powder spread over the buff--described on page 53--the
plate recieves its final polish; the circular motion is changed for a
straight one across the plate, which, if intended for a portrait,
should be buffed the narrow way; but if, for a landscape or view of a
house, the length way of the plate.
The operation of cleaning the plate at first appears difficult and
tedious, and many have been deterred from attempting this interesting
art on that account; but, in reality, it is more simple in practice
than in description, and with a little patience and observation, all
difficulties are easily overcome. Great care must be taken to keep the
buff free from all extraneous matter, and perfectly dry, and when not
in use it should be wrapped up in tissue paper, or placed in a tight
box.
The plate should be buffed immediately before the sensitive coating is
given; particles of dust are thus effectually removed; the temperature
of the plate is also increased by the friction, and the required tint
more readily obtained.
SECOND OPERATION.--Applying the sensative coating.--The apparatus and
chemicals required, are an
Iodine box--see fig. 14 page 53.
Bromine box--similar to the iodine box but a trifle deeper.
Dry Iodine.
Bromine, or a compound of Bromine and Chloride of Iodine, or other
sensitive mixture.
Most of our best operators use the compound Bromine and Chloride of
Iodine. In the early days of the Daguerreotype, Iodine alone was used
in preparing the plate, and although it still plays a very important
part, other preparations, called accelerating liquids, quickstuff, &c.,
are used, and the discovery of which has alone ensured the application
of the Daguerreotype successfully to portrait taking--for when first
introduced among us it took from five to ten minutes to produce a
tolerable good view, while now but the fraction of a minute is required
to obtain an accurate likeness.
To iodize the plate perfectly it must be placed over the iodine vapor
immediately after buffing. Scatter from a sixteenth to the eighth of
an ounce of dry iodine over the bottom of your coating box, and
slightly cover it with cotton wool. The plate is then dropped into the
frame b, fig. 12, with its silvered surface downward, and thrust under
the lid h. The bright surface of the plate is soon coated with a film
of iodine of a fine yellow color; it is then removed and placed over
the accelerating solution. It is not absolutely necessary to perform
this operation in the dark, although a bright light should be avoided.
Not so the next part of the process, viz; giving the plate its extreme
sensitiveness, or coating with the accelerating liquids. In this great
caution should be used to prevent the slightest ray of light impringing
directly on the plate, and in examining the color reflected light
should always be used. A convenient method of examining the plate, is
to make a small hole in the partition of the closet in which you coat,
and cover it with a piece of tissue paper; by quickly turning the plate
so that the paper is reflected upon it the color is very distinctly
shown. Most of our operators are not so particular in this respect as
they should be.
ACCELERATING LIQUID.--Of these there are several kinds, which differ
both in composition and action--some acting very quickly, others giving
a finer tone to the picture although they are not so expeditious in
there operations; or in other words, not so sensitive to the action of
light. These are adopted by Daguerreotypists according to their tastes
and prejudices. They are all applied in the same way as the coating of
iodine. The following are the best.
Bromine water--This solution is much used in France, and, I shall
therefore give its preparation, and the method of using it, in the
words of M. Figeau. "Put into a bottle of pure water, a large excess
of bromine; shake the mixture well, and before using it, let all the
bromine be taken up. An ascertained quantity of this saturated water
is then diluted in a given quantity of distilled water, which gives a
solution of bromine that is always identical." M. Figeau recommends one
part of the saturated solution to thirty parts its bulk of water; but
M. Lesebour finds it more manageable if diluted with forty times. In
case pure distilled, or rain water cannot be procured, a few drops of
nitric acid--say six to the quart--should be added to the common water.
Put into the bromine box a given quantity of this solution, sufficient
to well cover the bottom; the plate, having been iodized to a deep
yellow, is placed over it; the time the plate should be exposed must be
ascertained by making a few trials; it averages from twelve to forty
seconds. When once ascertained, it is the same for any number of
plates, as the solution, which of course would become weaker and
weaker, is changed after every operation, the same quantity being
always put into the pot.
Chloride of Iodine.--This is prepared by introducing chlorine gass into
a glass vessel containing iodine; the iodine is liquified, and the
above named compound is the result. Operators need not, however, be at
the trouble and expense of preparing it, as it can be obtained
perfectly pure of Mr. Anthony, 205 Broadway, N. Y., as also all of the
chemicals herein enumerated. The compound is diluted with distilled
water, and the plate submitted to its action till it is of a rose
color. Chloride of iodine alone, is seldom if ever used now by
American operators, as it does not sufficiently come up to their
locomotive principle of progression. The next is also eschewed by the
majority, although many of our best artists use no other, on account of
the very fine tone it gives to pictures.
Bromide of Iodine.--This is a compound of bromine and chloride of
iodine. In mixing it, much depends upon the strength of the
ingredients; an equal portion of each being generally used. Perhaps
the best method of preparing it, is to make a solution in alcohol of
half an ounce of chloride of iodine, and add the bromine drop by drop,
until the mixture becomes of a dark red color; then dilute with
distilled water, till it assumes a bright yellow. Put about half an
ounce of this compound into the pot, and coat over it to a violet
color, change the solution when it becomes too weak to produce the
desired effect.
Another.--Mix half an ounce of bromine with one ounce of chloride of
iodine, add two quarts pure distilled water, shake it well and let it
stand for twelve hours then add twenty-five drops of muriatic acid, and
let it stand another twelve hours, occasionally shaking it up well.
Dilute six parts of this solution in sixteen of water. Coat over dry
iodine to a deep yellow, then over the sensitive to a deep rose
color--approaching purple--then back, over dry iodine from four to
eight seconds.
Roach's Tripple Compound.--This is one of the very best sensitive
solutions, and is very popular among Daguerreotypists. To use this,
take one part in weight, say one drachm, of the compound and dilute it
with twelve of water; coat over dry iodine to yellow, then over the
compound to a rosy red. The effect in the camera is quick, and
produces a picture of a fine white tone.
Gurney's Sensitive.--This is another preparation of bromine, and gives
a fine tone. To two parts of water add one of the sensitive, and put
just sufficient in the box to cover the bottom, or enable you to coat
in from eight to ten seconds. Coat over dry iodine to a dark yellow,
and over the quick till you see a good change, then back over the dry
iodine from two to three seconds.
Bromide of Lime, or Dry Sensitive.--This is a compound but recently
introduced, and is becoming somewhat of it favorite, owing principally
to the slight trouble it gives in its preparation, and the tone it
imparts to the picture. To prepare it, fill your jar about half or
quarter full of dry slacked lime, then drop into it bromine, till it
becomes a bright orange red. The plate is generally coated over this
compound, after the iodine coating to yellow, to a violet, or plum
color; but it will work well under any circumstances, the color being
of little consequence, if coated from thirty to ninety seconds,
according to its strength.
Mead's Accelerator.--I merely mention this as being in the market, not
knowing any thing in regard to its merits. The directions given for
its use are as follows: Mix one-third of a bottle with a wine glass
full of water, coat the plate over dry iodine to a dark gold color,
then over the accelerator to a violet, then back over dry iodine, or
chloride of iodine, from three to five seconds.
Chloride of Bromine.--M. Bissou, a French experimentalist, has found
that bromine associated with chlorine, prepared in a similar manner to
chloride of iodine, already described, a solution of bromine being
substituted for the iodine, is a very sensitive solution; by means of
it daguerreotype proofs are obtained in half a second, and, thus very
fugitive subjects are represented, making it the very best compound for
taking children. So quick is its operation, that even persons or
animals may be taken in the act of walking.
Hungarian Liquid.--This, I believe, has never been used here, or
imported into this country, and the composition of it is not generally
known, even in Europe, where it has taken precedence of all others. It
acts quickly and with considerable certainty. It is used by diluting
it with from ten to fifteen times its bulk of water, putting a
sufficient quantity into the jar to cover the bottom. The plate being
previously iodized to a light yellow, is submitted to this mixture till
it assumes a light rose tint.
Bromine and Fluoric Acid, in combination, are used by some Daguerrean
artists as a sensitive, but any of the above compounds are better;
besides this, the fluoric acid is a dangerous poison, and the quick
made from it will not repay the risk to the health in using it.
As I have before said, great caution should be observed in examining
the color of the plate, even by the feeble light allowed, which, when
attained, must be immediately placed in the holder belonging to the
camera and covered with the dark slide. You then pass to the
THIRD OPERATION.--Submitting the Plate to the action of Light in the
Camera.--Experience alone must guide the operator as to the time the
plate should be exposed to the influence of the light; this being
dependent on a variety of circumstances, as clearness of the
atmosphere--and here, a reference to the hygrometer will be of
advantage--time of day, object to be taken, and the degree of
sensitiveness imparted to the plate by the quickstuff. As I have
before said, the artist should be careful to see that the interior of
the camera is clean and free from dust, as the small particles flying
about, or set in motion by the sliding of the holder into the box,
attach themselves to the plate, and cause the little black spots, by
which an otherwise good picture is frequently spoiled. Care should
also be taken in withdrawing the dark slide, in front of the plate,
from the holder, as the same effect may be produced by a too hasty
movement. The lens is the last thing to be uncovered, by withdrawing
the cap c. fig. 5., which should not be done until you have placed the
sitter in the most desirable position. When, according to the judgment
and experience of the operator, the plate has remained long enough to
receive a good impression, the cap is replaced over the lens, and the
dark slide over the plate, which is then removed from the camera.
Daguerreotypists generally mark time by their watches, arriving at the
nearest possible period for producing a good picture by making several
trials. As a ready method of marking short intervals of time is,
however, a very important consideration, and as any instrument which
will enable an artist to arrive at the exact period, must be an
improvement, and worthy of universal adoption, I will here describe one
invented by Mr. Constable of England, which he calls a
Sand Clock, or Time Keeper.--"It consists of a glass tube, about twelve
inches long, by one in diameter, half filled with fine sand, similar to
that used for the ordinary minute glasses, and, like them, it has a
diaphram, with a small hole in the centre through which the sand runs.
The tube is attached to a board which revolves on a centre pin; on the
side is a graduated scale, divided into half seconds; the tube is also
provided with a moveable index. This instrument is attached, in a
conspicuous place, to the wall. The glass tube being revolved on its
centre, the index is set to the number of half seconds required, and
the sand running down, the required time is marked without the
possibility of error. In practice it will be found to be a far more
convenient instrument for the purpose than either a clock or a seconds
watch, and is applicable both for the camera and mercury box."
If the artist finds it desirable or necessary to take the object to be
copied in its right position, that is reverse the image on the
spectrum, he can do so by attaching a mirror (which may be had of Mr.
Anthony, or Mr. Roach) to the camera tube, at an angle of forty-five
degrees.
If, after taking the plate from the camera, it be examined, no picture
will yet be visible, but this is brought about by the
FOURTH PROCESS.--Bringing out the Picture, or rendering it Visible.--We
now come to the use of the mercury bath, Fig. 11. To the bath a
thermometer is attached, to indicate the proper degree of beat
required, which should never be raised above 170 deg. Fahrenheit. The
plate maybe put into one of the frames (see Fig. 11,) over the mercury,
face downwards, and examined from time to time, by simply raising it
with the fingers, or a pair of plyers. This operation, as well as the
others, should take place in the dark closet.
[Illustration: Fig. 26 (hipho_26.gif)]
[Updater's note: hipho_26.gif and hipho27.gif are both captioned Figure
27.]
Sometimes, to prevent the necessity of raising the plate, an additional
cover or top is made use of. It consists of a box fitted closely to
the inner rim of the bath, and having an inclined top (a, Fig. 27.) The
top is cut through and fitted with frames for each size of plate, like
those already described, and in the back is a piece of glass (b,)
through which to view the progress of mercurialization, and an
additional piece (c,) on one side, colored yellow, to admit the light.
The outline only of the top is here given, in order to show every
portion of it at one view.
The picture, being fully developed, is now taken out and examined; it
must not, however, be exposed to too strong a light. If any glaring
defects be perceived, it is better not to proceed with it, but place it
on one side to be re-polished; if, on the contrary, it appears perfect,
you may advance to the
FIFTH OPERATION.--Fixing the Image so that the light can no longer act
upon it.--The following articles are required for this purpose:
Two or three porcelain or glass dishes, in form, something like fig. 24.
A plate support, fig. 25. Few, I believe, now make use of this,
although it is a very convenient article.
Hyposulphite of Soda,
A pair of Plyers.
In Europe, they also use a drying apparatus, Fig. 27, but this, like
the plate support, is a matter of little consequence, and may be
dispensed with. I will, however, describe it, for the benefit of those
who may wish to use it.
[Illustration: Fig. 27 (hipho_27.gif)]
[Updater's note: hipho_26.gif and hipho27.gif are both captioned Figure
27.]
A vessel made of copper or brass, tinned inside, and large enough to
take in the largest plate, but not more than half an inch wide, is the
most convenient. It must be kept perfectly clean. Hot distilled water
is poured into it, and the temperature kept up by a spirit lamp.
Hyposulphite of Soda.--Having made a solution of hyposulphite of soda,
and well filtered it--the strength is immaterial; about half an ounce
of the salt to a pint of distilled water is sufficient--pour it into
one of the porcelain dishes, put into another plain, and into a third
distilled water. Immerse the plate with its face downwards into the
hyposulphite, and the whole of the sensitive is removed, and the light
has no farther action upon it; it is then to be removed from the
hyposulphite and plunged into the plain water, or placed upon the
support, fig. 25, and the water poured over it. It is then washed in a
similar manner with the distilled water and well examined, to see that
not the slightest particle of dust rests on the surface. The next step
is to dry it.
This may be readily accomplished by holding the plate with your plyers,
and pouring distilled water over it--if it is hot, so much the better.
Apply the spirit lamp to the back, at the corner held by the plyers, at
the same time facilitating the operation with the breath; pass the lamp
gradually downwards, finishing at the extreme corner. The last drop
may now be removed by a little bibulous paper. A single drop, even, of
distilled water allowed to dry on any part of the surface, is certain
to leave a stain which no after process can remove.
To illustrate the necessity for having perfectly clean water, and free
from all foreign matter--only to be avoided by using that which is
distilled--in these processes, I will relate a little anecdote.
An operator in this city (New York) frequently made complaint to me,
that his plates were occasionally very bad; coming out all over in
little black and white spots and spoiling many very good pictures,
regretting at the same time that perfect plates were not made, for he
had lost many customers in consequence of these defects. These
complaints being somewhat periodical, I suggested that the fault might
be in the hyposulphite, or chloride of gold solutions, or particles of
dust floating about in the room, and not in the plate.
A few days after he stated, that his plates having served him again in
the same way, he procured a fresh supply of hyposulphite of soda and
chloride of gold, but after applying them the result was no better. He
then, by my advice, thoroughly cleaned his wash dishes, bottles and
water pail, made fresh solutions and had no further trouble, becoming
satisfied that the plates suffered an undue share of censure.
SIXTH PROCESS.--Gilding the Picture.--This is an improvement the honor
of which is due to M. Figeau, and may take place either before the
drying process, or at any subsequent period; but it improves the
picture so materially that it should never be neglected. The articles
necessary for gilding are--
A Pair of Plyers; or a Gilding Stand (see fig. 19) and Chloride of
Gold; or Hyposulphite of Gold.
The latter is imported by Mr. E. Anthony, 205 Broadway, New York, and
is decidedly the best article for the purpose. One bottle simply
dissolved in a quart of water will make a very strong solution, and
gives a richness to the picture impossible to be obtained from the
chloride of gold. The process is precisely similar to that described
below for chloride of gold, taking care to cease the moment the bubbles
are well defined over the surface of the plate. Many Daguerreotypists,
after a superficial trial, discard the hyposulphite of gold as
inferior; but I have no hesitation in asserting that the fault lies
with themselves; for in every case within my knowledge, where its use
has been persisted in until the correct method has been ascertained and
the nature of the gilding has become familiar, it is always preferred.
In illustration of this fact I will relate an anecdote:
A gentleman to whom it had been recommended, purchased a bottle, and
after making one or two trials of it, wrote to his correspondent--"Send
me two bottles of chloride of gold, for I want no more of the
hyposulphite; it is good for nothing." A few weeks after he sent for
three bottles of the condemned article, confessing that he had found
fault unnecessarily; for, that since he had become familiar to its use,
he must acknowledge its superiority, and would use no other gilding.
The Solution of Chloride of Gold is prepared by dissolving in a pint of
distilled water, fifteen grains of chrystalized chloride of gold. This
solution will be of a yellow tint. In another pint of distilled water
dissolve fifty-five grains of hyposulphite of soda; pour gradually, in
very small quantities, the gold into the hyposulphite of soda, stirring
the solution at intervals; when finished the mixture should be nearly
colorless.
Place the plate on its stand, or hold it in the plyers, in a perfectly
horizontal position--silver surface upward--having previously slightly
turned up the edges, so that it may hold the solution. Wet the surface
with alcohol, letting any superfluous quantity drain off. The alcohol
is of no farther use than to facilitate the flowing of the gold mixture
over the surface. Now pour on, carefully, as much of the preparation
of gold as will remain on the plate. The under part of the plate is
then to be heated as uniformly as possible with the spirit lamp; small
bubbles will arise, and the appearance of the portrait or view very
sensibly improved. The process must not be carried too far, but as
soon as the bubbles disappear the lamp should be removed, and the plate
immersed in distilled water, and dried as before directed.
7th. COLORING THE PICTURE.--I very much doubt the propriety of coloring
the daguerreotypes, as I am of opinion, that they are little, if any,
improved by the operation, at least as it is now generally practised.
There are several things requisite in an artist to enable him to color
a head, or even a landscape effectively, and correctly, and I must say
that very few of these are possessed by our operators as a class.
These requirements are, a talent for drawing--taste--due discrimination
of effect--strict observance of the characteristic points in the
features of the subject--quick perception of the beautiful, and a
knowledge of the art of mixing colors, and blending tints.
The method now pursued, I do not hesitate to say, and have no fears of
being contradicted by those capable of critisizing is on the whole
ruinous to any daguerreotype, and to a perfect one absolutely
disgusting. The day may come when accurate coloring may be obtained in
the camera. Until that day, if we cannot lead taste into the right
channel, we will endeavor to give such instructions that
Daguerreotypists may proceed with this part of his work with a better
understanding of the principles involved. For this purpose I have
prepared a short chapter on the art of coloring, which may be found in
the latter part of this volume.
To Preserve Daguerreotypes they must be well sealed and secured in a
case, or frame. These, of course, are selected according to the taste
of the customer, the principal requisite being good glass. Most
Daguerreotypists prefer the white French plate glass--and many think,
very erroneously, that none is good unless it is thick--but the great
desideratum is clearness and freedom from blisters; even glass a little
tinged with green or yellow is to be preferred to the French plate when
cloudy or blistered and there is very little of it comes to this market
that is not so. It is to be hoped that some of our glass factories
will manage to manufacture an article expressly for daguerreotypes; and
I would recommend them to do so, for they would find it quite an item
of profit annually.
Before enclosing the picture in the case you should be careful to wipe
the glass perfectly clean, and blow from the picture any particles of
dust which may have fallen upon it. Then take strips of sticking
paper, about half or three quarters of an inch wide, and firmly and
neatly secure it to the glass, having first placed a "mat" between them
to prevent the plate being scratched by the glass.
TO MAKE SEALING PAPER.--Dissolve one ounce of gum arabic, and a quarter
of an ounce of gum tragicanth in a pint of water; then add a
teaspoonful of benzoin. Spread this evenly on one side of good stout
tissue paper; let it dry, and then cut it up in stripes, about half or
three quarters of an inch wide, for use. If it becomes too soft for
summer use, add gum arabic; if too hard and cracking, add benzoin or
gum tragicanth; if it gets too thick, add water.
COLORED DAGUERREOTYPES ON COPPER.--To effect this, take a polished
plate of copper and expose it to the vapor of iodine, or bromine, or
the two substances combined; or either of them in combination with
chlorine. This gives a sensitive coating to the surface of the plate,
which may then be submitted to the action of light in the camera.
After remaining a sufficient time in the camera, the plate is taken out
and exposed to the vapor of sulphuretted hydrogen. This vapor produces
various colors on the plate, according to the intensity with which the
light has acted on the different parts; consequently a colored
photographic picture is obtained. No further process is necessary as
exposure to light does not effect the picture.
By this process we have an advantage over the silvered plate, both in
economy, and in the production of the picture in colors.
INSTANTANEOUS PICTURES BY MEANS OF GALVANISM.--It will be seen by the
following valuable communication that galvanism can be successfully
applied in producing pictures instantly; a process of great importance
in securing the likeness of a child, or in taking views of animated
nature. Colonel Whitney informs me that he once took a view of the
steeple of the St. Louis Court House after sundown by this means, and
also secured the image of a man in the act of stepping into a store,
and before he had time to place his foot, raised for that purpose, on
the door step. Mr. Whitney is well known as the talented editor of the
Sunday Morning news.
New York, January 16, 1849.
Mr. H. H. SNELLING.
Dear Sir,--As you are about publishing a history of the Daguerreotype,
and request a description of my mode of taking pictures instantaneously
by the aid of galvanism, I comply with great pleasure.
In the year 1841, while practicing the art in St. Louis, Mo., I was at
times, during the summer, much troubled with the electric influence of
the atmosphere, especially on the approach of a thunder-storm. At such
times I found the coating of my plates much more sensitive than when
the atmosphere was comparatively free from the electric fluid, and the
effect was so irregular that no calculation could counteract the
difficulty. This satisfied me that electricity was in some measure an
important agent in the chemical process, and it occurred to me that the
element might be turned to advantage. I determined, therefore, to
enter on a series of experiments to test my theory. Finding it
impossible to obtain an electric machine, and unwilling to abandon the
examination, it occurred to me, that the galvanic influence might
answer the same purpose. I therefore proceeded to make a galvanic
battery in the following simple manner. I obtained a piece of zinc
about two inches long, one inch wide, and an eighth of an inch thick.
On this I soldered a narrow strip of copper, about six inches long, the
soldered end laid on one side of the zinc, and extending its whole
length. The battery was completed by placing the zinc in a glass
tumbler, two-thirds full of dilute sulphuric acid, strong enough to
produce a free action of the metals. The upper end of the copper slip
extending above the tumbler was sharpened to a point, and bent a little
over the glass.
The method of using, was thus:--After preparing the plate in the usual
manner and placing it in the camera, in such manner as to expose the
back of the plate to view, the battery was prepared by placing the zinc
in the acid, and as soon as the galvanic fluid began to traverse (as
could be known by the effervescence of the acid, operating on the zinc
and copper) the cap of the camera was removed, and the plate exposed to
the sitter; at the same instant the point of the battery was brought
quickly against the back of the plate, and the cap replaced instantly.
If the plate is exposed more than an instant after the contact the
picture will generally be found solarized. By this process I have
taken pictures of persons in the act of walking, and in taking the
pictures of infants and young children I found it very useful.
Very respectfully yours,
THOMAS R. WHITNEY.