K. MECHANICS AND ENGINEERING. 415 



stitute for the old-fashioned black gunpowder in its military 

 and naval service. 4 B, July 15, 1869, p. 651. 



DUALIX AXD DYNAMITE. 



In the course of a careful investigation on the part of a 

 committee of engineers in regard to the comparative merits 

 of dualin and dynamite (the two more recent Wasting pow- 

 ders), it is stated that the former has advantages over ordi- 

 nary gunpowder in cases where the blasting is to be done in 

 soft stone or coal ; but where the labor of boring is difficult, 

 or where the gaining of time is of much importance, and 

 where the blasting is carried on in very hard and solid rock, 

 such as in most forms of tunneling, it is said that dynamite 

 is to be preferred. Our readers probably will remember that 

 dualin consists principally of nitrate of ammonia and very 

 fine sawdust, which has been acted upon by nitro-sulphuric 

 acid, and is said not to be decomposed by accidental contact 

 with acids, and not to lose any of its properties in cold or 

 heat. Its explosion does not produce any noxious gases, and 

 it will burn in the open air without exploding. Dynamite, 

 on the other hand, consists essentially of infusorial earth, pre- 

 pared in a particular way with nitro-glycerine. 5 C, xxiv., 187. 



DYXAMITE AXD GUX-COTTOX. 



A recent comparison between the two best known and 

 most readily used explosives, dynamite and compressed gun- 

 cotton, gives the palm decidedly to the latter as much the 

 safest and more manageable. It is stated that while a bullet 

 fired at a box of dynamite exploded it at once, the gun-cotton 

 was simply inflamed and burned in a steady manner ; and 

 that, while it is dangerous to apply a flame to dynamite, gun- 

 cotton simply burns, occupying some time in doing so. It is 

 well known that, to secure the highest explosive effect of 

 gun-cotton, it is necessary to set it off by means of a percus- 

 sion fuse or percussion cap, and that no other treatment will 

 do more than to cause it to burn harmlessly. 12 A, Decem- 

 ber 29,1870,169. 



DYNAMITE IX AETESIAX-WELL BOKIXG. 



Dynamite, so extensively used for blasting in mines, tun- 

 nels, etc., has lately been applied in Denmark to a new pur- 



