486 PROFESSOR LUDWIG MOSER ON LATENT LIGHT. 
made any experiments on other iodized metals, I cannot at pre- 
sent pursue this subject further, but must return to the latent 
colours of other vapours. 
With regard to those of chlorine, bromine, chloride and bro- 
mide of iodine, they cannot be very if at all different from that 
of the vapours of iodine. These vapours possess the same ge- 
neral properties as iodine ; and if the refrangibility of their latent 
light is different, the variations can only be such as cannot for 
the present be further examined. 
The vapours of water behave precisely like those of iodine 
in all experiments with which I am acquainted; where one is 
capable of destroying an image the other does so likewise; 
where one can produce an image it is also rendered visible by 
the other. Every image which is still in the Daguerrian state 
is destroyed by the vapours of water, and if it be breathed on 
after being removed from the camera obscura, or exposed to the 
vapours of warm water, it is so completely destroyed that va- 
pours of mercury do not render it again visible. If however the 
invisible rays have produced an image on any substance what- 
ever, the vapours of water do not destroy it; on the contrary, 
they make it appear. If it is very faint at first, repeated breath- 
ing on it often renders it more defined. 
Suppose an iodized silver plate which has received an image, 
which however is not yet outwardly visible. If the image was 
produced in the camera obscura, or, speaking generally, by ordi- 
nary light, when exposed to the vapours of iodine, water, or to 
the action of blue glass, it not only does not appear, but is 
“levelled” and destroyed. If, on the contrary, it was formed 
by the invisible rays, it is rendered visible by the vapours of 
iodine or water, and by the blue glass. 
If, from this similarity in the action of the vapours of iodine 
and water and blue and violet glass, any one should be inclined 
to conclude that the vapours of water contain blue or violet light 
in a combined state, which is set free during the act of conden- 
sation, I must remark that the following circumstances are to be 
considered :— 
1. That as yet I have discovered no difference between blue 
and undecomposed (white) light. 
2. That the research has not yet been carried far enough to 
enable us to distinguish between rays of nearly the same refran- 
gibility, as for instance between blue, violet, and dark (not in- 
visible) light. 
