PROFESSOR LUDWIG MOSER ON INVISIBLE LIGHT. 461 
allowed for the action to take place, then the plate exhibits the 
picture, for on those parts most exposed to the influence of the 
body the iodide of silver is blackened, although all that could 
possibly be called hight by the retina has been carefully excluded. 
I have often made this experiment myself. 
We must not, in the present state of the subject, examine the 
influence of pressure or contact on the surfaces of bodies, because 
the effects which are always obtained must be referred to the light 
evolved from all bodies. However, I do not entertain any doubt 
as to the influence exerted by pressure, for I think I have suffi- 
ciently proved that nothing more takes place on the retina during 
vision than is the case with all other bodies when these surfaces 
are affected by rays of light, and then, vice versd, it is allowable 
to draw conclusions concerning the phanomena observed on 
other bodies from those seen on the retina. As in the case of 
this latter body pressure so decidedly produces the same effects 
as light, it is probable that the same takes place with other 
bodies, although the real proof of it has not yet been given. But 
it is just the same with electricity ; that power produces in the 
eye effects similar to those of light, and one might from this 
conclude that the same would hold good for other substances, 
if the fact had not already been directly proved by Riess’s beau- 
tiful experiments. 
ARTICLE XVII. 
Some Remarks on Invisible Light. By Professor Lupwic 
Moser of Kénigsberg. 
[From Poggendorff’s Annalen, vol. lvi, p. 569, No. $*.] 
AS the subject of invisible light seems to have excited con- 
siderable interest, I will communicate the following experiments 
which I have made upon it :— 
1. Besides those bodies mentioned in my paper on Vision, I 
haye also obtained pictures from gold, copper, German silver, 
zinc, white transparent glass, bismuth, antimony, tin, lead, metal 
for mirrors, wood, mother-of-pearl, black pasteboard, black lea- 
ther, black velvet, and lamp-black. I covered an iron body of 
convenient form with a thick layer of this last body, and placed 
it at some distance from a plate of silver; on the plate being 
{* This paper is dated Konigsberg, July 1842.—Ep. ] 
