68 Imperial Institute of Fi mice. 



stronger condensation effected, than there would he ac- 

 cording to the proiwrtioual densities, of the two fluids, a 

 condensation according to which we can account for lhi» 

 heat. 



But M. Tliillaye has found, that when the alcohol is 

 weak, so far from the mixiure condensing, it is rarefied, 

 and nevertheless the heat is manifested in the usual man- 

 ner. He has constructed tables of his experiments, from 

 which we see that alcohol at 0*9544 of density begins to 

 exhibit rarefaction. Tlie maximum of the effect is shown 

 when the alcohol is at 0*9fi68, and when wc mix it with 

 one and a half its weight of water, and the elevation of 

 temperature is still two degrees. 



The contrary case, that of condensation of heat, produces 

 detonating substances, the best known of which is gun- 

 powder. One of the most dreadful is that kind of powder 

 in which we substitute instead of the nitre the oxygenated 

 muriate of potash ; but it is also one of the most dan- 

 gerous, for it detonates on simple percussion, and even by 

 friction. It has nevertheless been considered as calculated 

 for the priming of fire-arms^ because, as it needs no spark 

 of fire, it never fails. 



Messrs, Bottee and Gengembre have contrived a powder, 

 which preserves the properly of detonating bv a shock, 

 without being liable to fhe danger of a spontaneous ex- 

 plosion. It is composed of 44 parts in the 100 of hyper- 

 oxygenated muriate, 21 of common nitre, or nitrat of 

 potash, 18 of sulphur, and seven of po'.vder of lycopodium. 

 It requires the shock of the hardest bodies, and, what is 

 more singular, the part only which sustains the blow de- 

 tonates : the adjoining" parts are only inflamed by com- 

 munication, but they produce no explosion, so that this 

 powder is absolutely harmless. It is important therefore, 

 since it renders easy the use of a process which it has of 

 itself. 



The inquiries of chemists to discover substitutes for co- 

 lonial produce cotjtinue to h'- carried on with great zeal. 



Our associate M. Deyeux has published a string of in- 

 structions on the culture of beet root, with a view to render 

 it more productive of saccharine matter. M. Zanette has 

 presented some experiments on the saccharine quality of 

 the juice of maize. M. Dei-longchamps, a physician of 

 Paris, has 'made some experiments on the effects of the 

 juice of garden poppy compared with the opium of ^he 

 East. He has found then) similar, so far as regards the 

 ^uice obtained by the incision of the capsules, but twice as 



weak 



