1869.] EDWARDS — CHEMICAL EXPLOSIVES. 57 



towards the solution of the problem of the rationale of the 

 geographical distribution of plants and animals, but it might 

 also throw some light on that vexed question the origin of species. 

 These arctic or sub-arctic molluscs are not only in many cases of 

 high antiquity, but from their wide spread distribution we get an 

 opportunity of studying the modifications of species caused by 

 altered physical conditions. 



ON CHEMICAL EXPLOSIVES. 



GUNPOWDER — GUN-COTTON — NITRO-GLYCERINE — DYNAMITE. 

 By J. B. Edwards, Ph. D., F. C S. 



The rapid advance of gun-cotton and its congeners as formidable 

 rivals to gunpowder, is a remarkable example of the industrial 

 intelligence and enterprise of modern Europe. Gunpowder has 

 long occupied a remarkable position as a projectile. The mechan- 

 ical genius of the most advanced nationality, has been invoked 

 for improvements in armaments and defences ; but the chemical 

 condition of this explosive projectile has remained the same during 

 the past century. It would be rash to say that the days of gun- 

 powder are over, as our past experience has shown that new 

 inventions bring new appliances into action, and that in the spread 

 of civilization over the globe, all are required. Hence it is 

 probable that as much gunpowder will be consumed hereafter, as 

 before the invention of gun-cotton, but the latter wi'l, undoubt- 

 edly, be in large demand for mining industries, as well as for 

 some forms of ordinance. On the comparative mechanical value 

 of gun-cotton and gunpowder, Mr. Scott Russell has brought some 

 valuable data before the members of the Royal Institution, and 

 thus compares them : " Gun cotton, as prepared by the Austrian 

 process, is uniform in quality and permanent in action ; it 

 possesses the greatest cleanliness in use, not fouling the gun as 

 gunpowder does, and hence possesses great advantages for use with 

 breech-loading arms." 



Exploding in the open air it acts differently from gunpowder ; 

 if the latter is exploded in one pan of a pair of scales, the arm of 

 the balance is violently depressed ; an equal weight of gun cotton, 

 on the contrary, can be ignited without moving the pan. In the 



