166 THE CANADIAN NATURALIST. [Vol. VU, 



water-coursesf, some portion of its course much lower than the 

 point of its entry into the cavern, we have all the main conditions 

 necessary for a geyser. Suppose that all these caverns and pas- 

 sages arc full of water, the rocks of the cavern heated, and with, 

 perhaps, the addition of superheated steam from lower crevices. 

 The pressure of steam accumulating in the top of the cavern will 

 resist the further supply of cool water from the supply channel, 

 and perhaps force it back to a point where the hydrostatic pres- 

 sure of the column balances the pressure of the steam, which 

 meanwhile accumulates sufficiently to force out the water in a jet 

 into the external air. While the water in the cavern is above 

 the orifice of exit, the jet will consist only of water, but when the 

 cavern is emptied to the level of the outlet pipe, the steam will 

 escape and relieve the pressure. Then the cool water of the 

 supply channel, rushing in without resistance, cools the cavern 

 and fills it, preparatory to a new eruption, when the water is 

 again heated to boiling point. Diagrams of the natural geyser 

 and of an artificial one, constructed to illustrate it, were exhibited 

 and explained. 



THE CHEMICAL COMPOSITION OF A COPPER MATTE. 

 By Prof. T. Sterry Hunt, 



The name of matte or regulus is given to a product obtained 

 in smelting partly roasted sulphuretted copper ores, and consist- 

 ing in great part of sulphur and copper. It is the result of a 

 process of concentration. A specimen of this, holding 45 per 

 cent, of copper, beside iron and sulphur, was found to give up 

 the greater part of its iron to dilute acids, with the escape of 

 free hydrogen and sulphuretted hydrogen gases. It precipitated 

 metallic copper and metallic lead abundantly from their solution, 

 and contained apparently the greater part of its iron in a metallic 

 state. When oxidised by nitric acid or bromine, it left a residue 

 of more than ten per cent, of grains of pure magnetic oxide of 

 iron, and the dissolved portion contained about thirteen equiva- 

 lents each of copper and sulphur, beside eight of iron and a little 

 zinc. It was, as might be expected, strongly magnetic. 



The author insisted upon the apparent anomaly exhibited in 

 the association in a furnace product of a stable oxide of iron in 

 presence of a sulphuret, the affinities being curiously balanced in 



