* 
696 Chronicles of Science. [ Oct., 
spheric lines in the spectra of the planets, and the absence of them in 
that of the moon. This observation appears to show that the so-called 
atmospheric lines are not, after all, due to the absorbing action of. the 
earth’s atmosphere, or they would be present in the lunar spectrum. 
It is well known to all who have devoted attention to photographie 
chemistry that iodide of silver occurs in two modifications, one being 
sensitive, whilst the other is insensitive to the action of light. 
M. Kaiser, of Leipzig, has discovered that the insensitive modification 
may be transformed into the sensitive iodide by being submitted to 
the vapour of benzol. He says that the benzol vapour acts by deve- 
loping ozone in the air, and he has found that an atmosphere ozonized 
by electricity has precisely the same action. M. Kaiser’s experiments 
with benzol vapour seem to confirm a suspicion entertained by many 
photographers, that the wet collodion-plate is more sensitive than any 
other from its containing a small quantity of ozonized ether on its 
surface, and not because its pores are more open in the wet state than 
when dry. 
Speaking of photography, we transfer the following extract from a 
note just received from Dr, H. Draper, of New York. He says, “I 
have succeeded in taking a photograph of the Moon 50 inches in 
diameter, a size hitherto unapproached, and, in fact, as large as present 
processes will permit. It required six weeks of steady work, but fully 
repays me in the imposing effect gained.” 
The subject of light in relation to chemistry will probably attract 
much more attention in future than it has hitherte done. Chemists 
have, however, somewhat neglected the absorption spectra given by 
metallic and organic solutions in their hunt after fixed lines. At 
one of the recent meetings of the Chemical Society,* Professor 
G. G. Stokes, Sec. R.S., favoured the members with a discourse on the 
detection and discrimination of organic bodies by means of their 
optical properties. The properties most available for the chemist 
were colour-production by absorption, fluorescence, and reflection, 
and in a limited number of instances the phenomena of circular 
polarization. The professor exhibited a very simple arrangement of 
apparatus for the purpose of observing the effects of absorption. It 
consists of a small glass prism, having a refracting angle of 60° mounted 
vertically at one end of a long wooden tube, the other end of which is 
closed, with the exception of a narrow slit regulated by a screw; and 
against the outside of this aperture, and in front of the lamp, a test- 
tube containing the solution to be examined can be supported by 
means of elastic bands. When a dilute solution of permanganate of 
potash is viewed through the prism, the spectrum appears furrowed 
out with five dark bands of absorption at regular intervals between the 
fixed lines D and F, and many other coloured liquids, organic and 
inorganic, exhibit characteristic absorption-bands, by means of which 
they are capable of identification. In proof of the value of this test 
to the detection of organic colouring-matters, Professor Stokes stated. 
that Dr. Stenhouse had supplied him with a mixed colouring-matter, 
in which three of the ntadder principles were contained—viz. alizarin, 
* «Chemical News, vol. x. p. 288. 
