1 8 8 2 .] Mineralogy. 757 



mines of pyrites have lately been devoted to the manufacture of 

 sulphuric acid. These are the Capelton mines of Canada and 

 the Milan mines of New Hampshire. After the ore has been 

 burned to drive off the sulphur, the cinders are returned to be 

 treated for copper, the pyrites being cupreous. It is said that a 

 pyrites ore, in order to be useful for the manufacture of sulphuric 

 acid, must have a high percentage of sulphur, be near a market, 

 be of medium coarseness, and not be too soft; it must not fuse 

 easily, must contain no arsenic or antimony, must not decrepitate 

 when heated, and must burn readily and down to a low percentage 

 of sulphur: otherwise it will not pay. 



_ A dimorphous form of Tin.— Small crystals of tin are some- 

 times found in the slag from the smelting furnaces of tin works. 

 As shown by Trechmann, in slag from Penzance, and by 

 Foullon in slag from Mariaschein, the tin crystals may be of two 

 kinds, either the ordinary tetragonal form, such as are deposited 

 by galvanic action, or, more generally, an orthorhombic form, not 

 previously observed. 



The general appearance of the latter is that of a loose, irregular 

 mass of thin plates of different sizes, sometimes a quarter of an 

 inch square, which have a bright metallic luster and a grayish 

 color. These plates are built up of a number of sub-crystals, 

 which, having well defined edges, were capable of goniometrical 

 measurement. They were found to have the axial ratio : 

 a:b: c = 0.387 : 1 : 1.035. 



Blasting with Lime.— A new and ingenious method of blast- 

 ing has lately been tried at a coal mine in Derbyshire, which, dis- 

 pensing with the use of gunpowder, depends upon the action of 

 water upon. caustic lime. Cylindrical blocks of caustic lime, 2)A 

 inches in diameter by 4^ in length, are prepared by the com- 

 pression of burnt lime under a hydraulic press. The blocks, each 

 of which has a longitudinal groove '-J inch in diameter, are taken 

 in air-tight boxes to the mine and placed in holes forae three feet 

 deep, which have been bored in the coal. By means of an iron 

 Pipe which fits into the grooves in the blocks, water is now intro- 

 duced to the bottom of each hole. 



In the course of a few moments a sound like that of steam 

 escaping under high pressure, is heard, which is immediately fol- 

 lowed by the breaking down of the coal. There is no sudden 

 explosion or danger from fire. 



This method is of course inapplicable for the blasting of hard 

 and compact rocks. 



The formation of Sulphur in the Soil of Paris. — In the 

 course of an excavation for a sewer in the streets of Paris, the 

 workmen encountered a mass of rubbish consisting of animal and 

 vegetable refuse mixed with bones and with plaster. The bones 

 were filled with crystalline acicular gypsum, and the plaster was 



