SCIENTIFIC SUMMARY. 
315 
and crystallizing in regular octahedrons ; the other containing 10 equiva- 
lents, and forming oblique rhombic prisms. The octahedral crystals are 
commonly considered stable only at relatively high temperatures. He, 
however, finds that both the prismatic and the octahedral form can be pro- 
duced at low temperatures. The temperature of 56°, which has been in- 
dicated as the inferior limit for the production of prismatic borax, is in 
reality only a temperature near the higher limit at which the production of 
prismatic borax has been observed, since this salt loses a part of its water at 
this temperature. 
The Amount of Carbonic Acid Gas in the Atmosphere.— It seems that a 
series of determinations have been recently made by M. Truchot, who has 
published the results in papers in the i( Comptes Bendus ” (lxxvii. p. 675), 
and the u Bull. Soc. Chimique.” His metnod of analysis consisted in 
passing a known volume of air through a graduated solution of barium 
hydrate, allowing the barium carbonate to deposit, and retitring the solu- 
tion. He finds : 1st, that at Clermont-Ferrand, where the experiments 
were made, the proportion of carbonic gas is a little greater during the night 
than in the daytime — a fact confirmatory of the observations of Saussure 
and Boussingault. 2nd, that the proportion is not sensibly greater in the 
city than in the open country. 3rd, that in the vicinity of green-leaved 
plants the quantity of carbonic gas varies notabty, according as the green 
parts are exposed to full sunlight, to diffused light, or are in the shade,* the 
amounts being 3*54, 4*15 and 6*49 parts in 10,000 of air. 4th, that the 
general mean is 0*814 milligram of carbonic gas to the litre of air, or 4*09 
parts in 10,000 ; a number very near that usually received. 5th, that the 
proportion of carbonic gas diminishes with the altitude, thus : 
Station. 
Altitude. 
Wt. C0 2 
to the litre. 
Vols. of C0 3 
in 10,000 of air. 
Clermont-Ferrand . , 
. . 395 m 
0*623 m & 
3*13 
Puy-de-Dome . . . 
. 1446 
0*405 
2*03 
Pic-de-Sancy . . . 
. 1881 
0*342 
1*72 
How to Detect False Colouring Matter in Wine . — M. De Cherville gives 
the following test. He says : — “ Pour into a glass a small quantity of the 
wine under examination, and dissolve in it a morsel of potassa. If there is 
no deposit, and if the wine takes a greenish tint, it has not been artificially 
coloured. If a violet deposit has been formed, the wine has been coloured 
with elderberries or mulberries. If the deposit is red, beet-root or peach- 
wood has been used ; and if violet-red, logwood. If the sediment is violet- 
blue, privet berries have been employed, and if a bright violet, litmus.” 
The Dangerous Nature of certain Coloured Tapers . — At a recent meeting 
of the Chemical Section of the “ Glasgow Philosophical Society,” an im- 
portant paper on this subject was read by Mr. James McFarland, Assistant 
to the Professor of Chemistry, St. Andrew’s. In this the author 
detailed a series of experiments which he had prosecuted for the pur- 
pose of determining the nature of the colouring matter in the green and 
red wax tapers. He distinctly ascertained that the former owed their 
colour to the presence of Scheele’s green (arsenite of copper). Their 
average weight was 2 grams, and the average time occupied in burning was 
seventeen minutes. Guided by the colour and by the alliaceous odour 
