SCIENTIFIC SUMMARY. 
295 
little increased by greatly increasing the heating power of the electric dis- 
charge. If these results are confirmed by other investigators, we shall 
have to be much more careful in employing spectrum observations 
for the purpose of chemical analysis, and to learn what conditions 
modify the appearance of the lines before we can safely use them for that 
purpose. 
MM. Wolf and Diacon, in a paper published in the Revue de Societes 
Savantes, have described a method they employ in spectrum analysis. 
They volatilize the substance to be examined by heat in a current of 
hydrogen, and ignite the escaping jet of hydrogen in contact with a jet of 
pure oxygen, and state that under these conditions many metallic chlorides, 
but especially alkaline metals and their volatile compounds, produce 
perfectly distinct and very lasting spectra. 
Sir David Brewster, in a paper “ On the Action of various coloured 
Bodies on the Spectrum,” in the “ Philosophical Magazine,” Dec. 1862, 
has published his observations on the action of numerous solids, liquids, 
and gases on the solar spectrum. The substances employed include solu- 
tions of alkanet-root, cochineal, chica, cudbear, sulphate of indigo, sul- 
phate of chromium, nitrate of cobalt, litmus, sulphate of copper, sulphate 
of ammonia and chromium, chromate of ammonia, sulphate of cobalt 
mixed with chromate of ammonia, sulphate of potash and nickel, carba- 
zotate of potash, ferriocyanide of potassium, sulphate of potash and 
copper, bivanadiate of ammonia, chloride of iridium and potassium, 
carbazotic acid, ammoniuret of nickel, nitrate of copper, nitrate of nickel, 
ammoniuret of copper, chloride of copper, sulphate and nitrate of iron, 
chromate of potash, oxalate of chromium and potash, aud arsenite of 
copper dissolved in hydrochloric acid. 
In a paper communicated to the British Association, J.H. Gladstone, Esq., 
F.R.S., calls the attention of scientific men to those lines of the solar 
spectrum which are due to the terrestrial atmosphere, and incites observers 
to watch those lines and bands under every possible variation of circum- 
stances, such as at different periods of the day and year, at different 
altitudes, &c. &c. By the aid of a portable spectroscope, he has made 
numerous observations of the kind, and has observed several bands not 
recorded in the map of Sir David Brewster and himself in the “ Philoso- 
phical Transactions,” 1860. 
Dr. A. Weiss has been making spectrum observations in Greece : he 
succeeded in observing, in a surprising manner, a condensation of the lines 
of the red and yellow portions of the spectrum, and considers that, from 
the purity of the sky, Greece (and especially the Ionian Islands) is very 
suitable for spectrum observations. 
M. Brachet has proposed as an improvement, in applying the electric 
light, to inclose the light within a globe of uranium glass, and that again 
within a second glass globe, of such a colour as to correct the greenish tone 
of the resulting light ; and the proposal has been referred to MM. Regnault 
and Babinet for consideration. 
The “motion of camphor towards light” has been the subject of a recent 
investigation by Mr. C. Tomlinson. He shows, by various experiments, 
that the crystalline deposits of camphor in bottles, which occur when that 
