1867.] Mining. 271 



and at the bottom of the shaft the hanger-on is provided with a 

 pair of electrical tappers, coloured respectively white and red. 

 The white tapper being touched, the bell is rung in the engine- 

 house, and the words " Go on " appear on the dial ; on touching 

 the red tapper, the bell is struck as before, and then the word 

 " Stop," in white letters on a red ground — as indicative of danger 

 — appears. 



The salt-mines of the Nevada Territory are the most con- 

 siderable in the United States. A single bed of rock-salt occupies 

 a superficial space of 52,000 acres, and produces annually two 

 million bushels of a mineral which gives 95 per cent, of pure 

 salt. If the ground is pierced to the depth of from 250 feet to 

 300 feet saline water rises so rapidly and with such force that all 

 the workings are interrupted. 



Coal is stated to have been discovered in India, at Nursingpore, 

 in the immediate neighbourhood of the Great Indian Peninsular 

 Eailway. This discovery, if the quality of coal is good, is of 

 great importance. 



In a communication " On Gun Cotton and its Use in Blasting," 

 made by Messrs. T. Prentice and Co., to a contemporary journal* 

 they state : — " We have lately prepared a very condensed charge, 

 one inch of which will be found equal to six ounces of powder. Of 

 our lj-inch diameter, five inches in length are equivalent to one 

 pound of powder, and can be supplied at 4J^. By the use of 

 this in hard granite rock, a large saving in boring is effected : the 

 charges slip readily into the hole, leave no residue on the side, and 

 only require the fuse to be connected with the uppermost piece. 

 The total absence of smoke, comparative freedom from danger, 

 portability and convenience of form, combined with saving in labour 

 and material, are advantages which are bringing Gun Cotton 

 largely into use." 



We quote this passage, and can, from our own knowledge, confirm 

 much that is stated. Upon one point we must, however, remark. 

 That there is a total absence of visible smoke is admitted on all hands ; 

 but in the combustion of Gun Cotton, gases are formed, which, float- 

 ing in the atmosphere of a close end in a mine, may exert a most 

 injurious effect on the miner, should he incautiously resume his 

 work too speedily after the blasting of a hole. 



Mineralogy. 



In the February number of the ' Philosophical Magazine,' Mr. 



David Forbes, F.K.S., continues his " Kesearches on the Mineralogy 



of South America." The present paper contains a sketch of the 



" General Mineralogy of Chili," the author having spent four years 



* ' Mining Journal.' 



