112 
POPULAR SCIENCE REVIEW. 
being deyeloped the solution becomes turbid, and emits an odour resembling 
that of powdered digitalis or the tincture, and a broA^m substance, AA'hich 
seems to be a compound of digitaline, is deposited. This variety of digitaline 
turns broAvu when exposed to the fumes of hydrochloric acid, but shows no 
green colour. When Auewed under the microscope AAuth a high poAA'er, it is 
seen to consist of small semi-transparent fragments, AA'hich occasionally pre- 
sent sharp edges, but have nothing approaching to a definite crystallhie 
arrangement. 
The French digitaluie, on the other hand, though exceedingly soluble in 
alcohol, is but sparingly so in water, a litre of which dissolves only 0'50 of a 
gramme. The colour A’^aries from a yelloAvish-Avhite to a bright yellow. This 
form of the alkaloid is slightly soluble hi sulphuric ether, sulphide of carbon, 
and benzole, and is precipitated from its saturated aqueous solution by taimin. 
When exposed to the A'apour of hydrochloric acid, it becomes first yelloAA', 
then broAvn, and finally green ; thus shoAving a very dififerent reaction from 
the soluble form. This difference in colour suffices at once to distinguish the 
tAvo varieties, and it is even thought sufficient to demonstrate the presence of 
the French species. — Vide Chemical News, August 27. 
Comparison between the Effects of Gun-cotton and Gunpowder. — It is quite 
true, as Mr. Scott Eussell remarked, in his recent lectures at the Royal Insti- 
tution, that there is considerable difficulty in comparing the properties of the 
tAvo latter compounds. The cotton he considers to be sixfold stronger than 
the powder. Thus, if we take four oimces of gun-cotton, and if Ave bore a 
hole 3 feet deep and inches wide into hard rock or slate in a quarry, and 
place this quantity of cotton in it, and close the aperture in the usual manner ; 
and if, in the next place, we fill a similar hole Avith 24 ounces of best gun- 
powder, and then explode both compounds, the 4 ounces of gun-cotton Avill 
do more work in splitting the rock than the 24 ounces of gunpowder. Gun- 
cotton is more convenient than powder, because it has not that power of 
heating the metal, which causes so much delay and danger in ordinary artillery 
practice. Again, there is no smoke ; whereas, occasionally in artillery practice 
at sea the stratum of smoke is so dense that nothing can be seen from the 
ship. Besides, gun-cotton leaves no dirty deposit, and hence is devoid of that 
nasty quality Avhich powder possesses of fouling the gun. It is not cheaper 
when compared pound for pound with powder ; but such a comparison Avould 
be unfair, as it is by the relative quantities of the tAVO substances required te 
produce a given result that we should estimate their comparative value. Mr. 
Eussell gives the folloAAung very interesting illustration of the operation of 
both these compounds under the same conditions : If a general wants to bloAV 
open the gates of a city, he orders an enterprising party to steal up to the 
gate with a bag containing a hundred pounds of gunpowder, which he nails 
to the gate, and by a proper match-line he fires the gunpowder, and bursts 
open the gate. If he nailed a bag of gun-cotton of equal weight in the same 
place, and fired it, the gun-cotton Avould fail, and the gate would be uninjimed, 
although the hundred pounds of gun-cotton are sixfold more poAverful than 
the gunpowder. Here, then, gunpowder has the advantage, both weight and 
effect considered. But the fault here lies, not in the gvin-cotton but in the 
AA’ay of using it. If, instead of a hundred pounds of gun-cotton in a bag, 
tAventy-fiA’-e pounds had been taken in a proper box made for the purpose, and 
