Ch errdcal Science. 340 



difference of effect is observed upon the surfaces which have sup- 

 ported the powders, tliat is to say, in the direction downwards ; 

 and this has been admitted as if the difference existed exclusively 

 in that direction, merely because the experiment has not been 

 made with the resisting plane in other positions. It will be 

 found, however, that if a portion of fulminating silver be attached 

 to a metallic or other plate, that when exploded, whatever the 

 position of the plate, the effect upon it will be sensibly equal. 

 All the differences in the phenomena presented by these powders 

 and gunpowder, depending upon the greater rapidity of chemical 

 action in the former than in the latter. 



M. Brianchon's theory of the supposed force of these powders 

 in a direction almost exclusively downwards, is, that being com- 

 pounds, deficient in oxygen, but resolved by heat in the air into 

 compounds containing much oxygen, the vapour of the substance 

 at the moment of explosion seeks in the atmosphere for the oxy- 

 gen it wants, abstracts it as it were by powerful suction, and 

 causes a precipitation of the columns of air on to it. M. Brian- 

 chon seems to think that the columns of air can only move down- 

 wards in this case, and he illustrates his opinion by the old ex- 

 periment of breaking a bladder on the air-pump over a receiver 

 exhausted beneath it. There is no rea'son, however, why the air 

 at the sides or beneath should not also rush towards the point of 

 action, or to express it more generally, why, when either ex- 

 pansion or contraction to any extent takes place in the atmo- 

 sphere from a single point, whether from gunpowder, fulminating 

 power, or what not, the effect should not be alike in every direc- 

 tion, seeing that the air is a fluid so eminently elastic, mobile, 

 and unifomi. 



In consequence of his particular views, and the cheapness of 

 the materials of which common fulminating powder is made, 

 namely sulphur, carbonate of potash, and nitre, M. Brianchon 

 has proposed its use as a mechanical agent, acting from above 

 downwards, for the crushing, burying, or throwing down bodies 

 of large dimensions. He intends proposing its use in war time 

 for the destruction of bridges, and means to request that experi- 

 ments be made on this subject. 



p 22. Moretti's fulminating Acid. — On occasion of the late experi- 

 ments made by MM. Liebeg and Gay-Lussac, on fulminating 

 compounds, 8;C", the Giornale di Fisica has republished the ac- 

 count of an acid also possessing detonating properties, prepared 

 as far back as 1808 by Professor Moretti, from indigo by nitric 

 acid. We make the following brief extracts of the experimental 

 results which it contains : 14 parts of nitric acid of specific gra- 

 vity 1.430 and I part of Guatimala indigo were distilled together ; 

 about a fourth part of the new acid was obtained with a small 



