xliv GENERAL SUMMARY OF SCIENTIFIC AND 



remains to be noticed Dr. Sprengel's paper upon "a new 

 class of explosives, which are non -explosive during manu- 

 iiicture, storage, and transport." Dr. Sprengel finds it pos- 

 sible to devise many explosive mixtures of substances, whicii, 

 apart from each other, are non -explosive, and which need 

 not be mixed until the combination is to be used. For in- 

 stance, mixtures of many organic compounds, notably some 

 hydrocarbons, with nitric acid, both ingredients being non- 

 explosive, will explode with great violence when ignited by 

 a detonating cap. The mixture of nitro-benzol with the acid 

 seems to be about thirty-eight per cent, more violent as an 

 explosive agent than nitro-glycerine ; both of the original 

 substances being quite harmless. Picric acid mixed with 

 nitric acid is also a terribly violent detonator. In this mixt- 

 ure the heat given out is something immense. In one in- 

 stance a metallic cartridge was charged with it, and fired 

 from a rifle. On extracting the cartridge-case the upper 

 half of it was found to have been melted ; while grains of 

 sand, which had been added to the explosive mixture, and 

 some of which remained in the cartridge, were " fused to- 

 gether as if struck by lightning." Obviously this principle 

 of mixing non-explosive agents to form explosives is capable 

 of great extension. At present there are some trifling prac- 

 tical disadvantages in the way of using such mixtures. 

 Soon, doubtless, these disadvantages will be overcome, and 

 the art of blasting: will be revolutionized. 



GEOLOGY AND MINERALOGY. 



In American (rco^o^?/, important results have been obtained 

 in the West. In the survey of the Territories under Dr. Hay- 

 den in 1872, the geology of the Snake River division was 

 confided to Professor Bradley, who has within the last few 

 months given us a summary of the work done. It had for 

 many years been known that strata characterized by organic 

 remains of the Potsdam period were not wanting in the 

 Rocky Mountains, and the observations of Professor Bradley 

 now make known the existence in the Wahsatch Mountains 

 of a large development of the Lower and Middle Cambrian 

 rocks of Sedofwick, the Primal and Auroral of Roo-ers. Tlie 

 ancient gneisses of the Wahsatch, with high westerly dips, 

 are overlaid by a great mass of paleozoic strata, dipping east- 



