290 ON THE TRANSMUTATION OF ROCKS, &c., 



the centre of the mass, whilst the outside had entirely been 

 changed into hydrafced ore. 



I am now able to exhibit an equally interesting proof of similar 

 transmutation. This specimen was brought down with many 

 others from the Harding River, De Witt's Land, and sent to me 

 by the Hon. F. P. Barlee, Colonial Secretary of Western Australia. 

 This example is doubly striking from the fact that the iron retains 

 its crystalline form. The gangue of this mineral is an altered rock 

 associated with trap. M. Yirlet says, that at whatever period 

 the Jurassic rock of the Cevennes was intruded into by the pyrites, 

 the change spoken of still goes on, and he believes it to be 

 electro-chemical. 



With respect to minerals in general, it may be remarked, that 

 they may be deposited at a temperature much lower than is 

 necessary to fuse them. 



Below, or not higher than 104 F., products characteristic of 

 metalliferous veins may be formed. 



On the authority of M. Julier, it is stated by Daubree, that an 

 old brass cock of ancient Roman origin was found at the baths of 

 Plombieres, under a mass of masonry, and that it was covered with 

 crystals of sulphuret of copper absolutely identical with Cornish 

 sulphuret in aspect, form and properties. The water there also 

 deposits quartz crystals, holding alkaline silicate in solution. 



From Somma (Vesuvius), limestone has been ejected un- 

 touched, and granite also in Auvergne. The former was covered 

 by minerals such as occur in the open air. Therefore, similar 

 phenomena take place far below, as well as near or at the earth's 

 surface. 



The temperature of springs seldom goes beyond 212 F., 

 and under three-fourths of the earth's surface, springs have 

 to support an ocean of 200 atmospheres ; rocks, therefore, 

 may be altered at great depths by pressure, and by imbibition of 

 gases bringing up from greater depths minerals and metallic 

 emanations which, when a fissure has been formed, may rush to 

 the surface, producing mineral veins in convenient places. 



Thus, Daubree considers the gold and tin deposits of Saxony, 

 Bohemia and Brazil have been formed ; but if so, why not those 

 of California and Australia ? 



