SCIENTIFIC SUMMAEY. 
105 
sulphate, carbonate, bicarbonate of potash, nitrate of lime, carbonate of soda, 
chlorides of potassium, and of sodium. 
The Chlorophyll Spectrum . — This spectrum, says M. Chautard (in the 
11 Comptes Rendus,” Sept. 8th), is characterised by a number of bands, one 
of which has the special properties of sensibility, sureness (in its division 
by alkalies, a character not found in the lines of any other organic liquid), 
and generality. Chlorophyll in plants exists in three different states, dis- 
tinguishable through the spectrum — in leaves newly formed, in adult, and 
in dead leaves. In the first case, chlorhydric acid produces accidental tern- 
porary bands. In the second it produces quite another system of bands, 
which the author calls accidental permanent. In the third (and alcoholic 
solution), the accidental permanent bands appear immediately, without the 
intervention of hydrochloric acid. Chlorophyll is much less alterable than 
is generally supposed. It resists the action of iodine, acids, alkalies, diges- 
tive work ; at least retaining characters by which it may be detected in 
mixtures the most complex and varied, and after lapse of considerable time. 
How to Compare Different Samples of Gunpowder . — A very good paper on 
this important practical question appears in the 11 Moniteur Scientifique ” 
for September, by M. de Tromenic, who describes his plan thus : — The 
apparatus proposed is a cylindrical vessel of cast steel of the capacity of 
half a litre. The sides are 3 to 4 centimes in thickness. The cylinder is 
closed with a screw stopper pierced by a central channel, provided with a 
tap and two lateral orifices, into which are cemented two wires from an 
electric apparatus to ignite the charge. It would be useful to fix a thermo- 
electric element in one of the sides of the cylinder to indicate the tem- 
perature of the gases in periods following the explosion. The cylinder is 
placed in a sheet-iron receiver full of water, which serves as a calorimeter, 
and which is again enclosed in a trough full of cotton, to avoid loss of heat. 
The cylinder is fixed immovably by a pressure-screw resting upon the 
stopper. A thermometer measures the temperature to about j^th a 
degree. The water is provided with an agitator. 
Sugar from Beet-root , and the XJse of Horsky's Diffusion Apparatus . — 
In one of the numbers of 11 Les Mondes ” for September is an account of 
this method. It says that this apparatus does away with the rasping pro- 
cess in the manufacture of beet-root sugar, dispenses with three-fourths of 
the manual labour, and extracts the saccharine matter completely. The 
yield of sugar obtained by the use of this arrangement has this season 
amounted to 8*5 per cent., an amount greatly superior to that obtained in 
neighbouring establishments where other processes for extraction are in use. 
The Stroboscopic Determination of the Pitch of Tones . — A very interesting 
paper on this curious subject is that by Herr Mach, which was read some 
time ago before the Academy of Sciences at Vienna, and has recently found 
its way in abstract into one of our English scientific magazines. Jn Herr 
Mach’s apparatus there is a cylinder which makes three revolutions in a 
second, and is divided into five octaves. At one end of it begins 10 bands, 
which, however, become more numerous and dense towards the other end, 
being there 320. To the axis of a syren is fixed a disc having equidistant 
radial slits of the same number as the holes in the syren-disc. The surface 
of the rotating cylinder is looked at through this slitted disc, while the syren 
