56 Scientific Intelligence. 
quantity theoretically present in the vio analysed. ‘The 
source of this deficiency was eventually trace the action which 
the oxides of nitrogen exerted on the alkali of ae glass, and also 
ou the mercury. For when some of the tubes which had been 
subjected to a temperature not above dull redness were washed 
with a little water, the washings could 258 ways be shown to con- 
tain a nitrate and a soluble salt of mercury; others, the tempera- 
ture of which had been higher, contained nitrates and nitrites, 
but no soluble mercury salt. 
For the purpose of showing more conclusively that the glass 
was thus attacked, and in order also to investigate the extent of 
the action, the following experiment was performed: A tube of 
ard glass, 50 ¢. ¢. capacity, was cleaned until the evaporated 
ue 
filled with red fumes; after which it was heated to dull sage 
for two hours. When cold it was still full of red fumes, and 
when these were withdrawn it was washed as before, ad ‘the 
evaporated washings left a residue of 0°0038 of a grm., consisting 
of nitrates and nitrites. The same experiment was repeated three 
times on the same tube ; the second pote was 0°0044 of a grm., 
and - third 0-0022. Another tube gave 
might be expected, this action is cos more energetic at a 
Zi ar than at a low temperature, and it Lit to be very slight 
until the heat approaches redness. In the analysis of such nitro- 
genous compounds as have the nitrogen in combination with oxy- 
gen, a certain deficiency of nitrogen, varying with the tempera- 
ture anplogit. may therefore be expected.— Chem. News, Nov. 
25, 1881 
Il. GgoLoegy AND MINERALOGY. 
1. On the Periodical Variations of Glaciers.—Mr. F. A. 
Forex, of Morges, has an important memoir on this subject in 
the Geneva Archives des Sciences Physiques et Naturelles, 
July, 1881, based on observations in the Alps. He refers to the 
os elongation of the Grindelwald glacier in iy that of the 
ply of snows, oy a )t ah cae of the ice or ablation “By 
means of h eat. Abundant snows lengthen it; heat thins and 
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glaciers lengthen during cold summers, when the snows are not 
sufficient to account for the change. The true theory was sug- 
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