182 Miscellanies. 
first tracing is avoided. But there is no necessity for using paper, as 
the impression may at once be communicated to the stone, which ea- 
sily receives the phosphate, and which may therefore be prepared in 
the same way as the papers, and the impression also taken in the usual 
manner, after which it is traced over with the transfer ink. By this 
process not only is a great deal of labor saved, but the representation 
must be much more exact than when traced ; for though by the latter 
the outline is correct, yet much is left to be afterwards filled in by the 
eye, whereas, by the photographic process, every, even the most mi- 
nute filament, is distinctly and accurately laid down on the stone.” 
Method of taking Impressions in which the lights and shades are not 
reversed. 
By the different methods now described for getting photographic 
impressions, the lights and shades are always reversed, because, as it 
is by the action of the light that the compound of silver is darkened, 
wherever it is prevented from penetrating, the paper retains ils ori- 
ginal color. Though the impressions thus procured are accurate as t0 
outlines, yet in many cases the representation is far from being pleas- 
ing; it is therefore a great desideratum to have a method of getting 
impressions in which there is no reverse; in fact, to give a true repre 
sentation of the object, and in this I have succeeded by the use of the 
iodide of potassium. I have already stated, that when the darkened 
phosphate is exposed to the iodide, it is instantly converted to yellow, 
provided the solution is of sufficient strength ; if weak, the action goes 
on slowly. In some impressions which I had attempted to preserve 
in this way, 1 observed that when exposed to light they began to fade, 
which induced me to try the effect of light on darkened paper, soaked 
in solution of iodide, of such strength that it just failed to attack it 
instantly. In my first attempt I succeeded in bleaching the pape 
but in my next I failed. On considering the circumstances under 
which these trials were made, I found that the only difference between 
them was, that in the first the paper was moist, in the last it was ary: 
Accordingly, on repeating the experiment with the paper moist, I 
again succeeded in getting a delineation of the object placed on the pa 
per, as distinct and altogether as brilliant as those obtained by the 
other process, 
Pee 
* For this method of applying the photographic process I am indebted to nt 
Nichol, lithographer, by whom lithographic impressions, thus taken, were exhibited 
to the Society of Arts. As a proof of the value of this process, I may also mentions 
that on the evening of the 17th of April, when I exhibited a photographic 
of dried ferns, it was, by Mr. Forrester, lithographed, and impressions taseh 
: it would have 
te deline® 
it, in the course of two hours; had this been done in the usual way, 
required many hours of labor, and after all not have given such accurate | 
tions. P 5 le 
