70 WRITINGS OP JAMES SMITHSON. 



Hartz to consist of sulphur, copper, and iron, I had recourse 

 to the yellow sulphuret of copper and iron. To produce 

 the required portion of metallic copper, I calcined some 

 small fragments of this yellow ore at the tip of the exterior 

 flame. Finding that I had exceeded the proper point, and 

 rendered them too infusible, I added a little of the raw ore ; 

 and after encountering a few difficulties succeeded in pro- 

 ducing a little mass of slag, whose internal cavities pre- 

 sented me, on breaking it, with the fibres of copper which 

 were the object of my toil. 



A repetition of these experiments in a furnace, on a larger 

 scale, would undoubtedl}'^ have yet more successful results. 



It deserves to be noticed that the curved form which these 

 fibres of copper generally have is entirely favourable to the 

 foregoing theory of their formation, and equally contrary to 

 the supposition of their being produced by crystallization. 



The power to which has been ascribed the phenomenon 

 which forms the subject of these pages has hitherto been 

 overlooked. It has not been considered what the eftects 

 might be of the contraction of a melted mass at the moment 

 of its congelation. It is, however, a means of effects which 

 may have acted on many occasions in the earth. Two mat- 

 ters of unequal fusibility, and of no attraction to each other, 

 are not unlikely to have occurred blended in a state of fusion ; 

 and then the most fusible to have become pressed out from 

 between the particles of the other when it solidified. If 

 some evolved vapour had opened cavities in the mass, or 

 rents had formed in it, the fluid matter will have escaped 

 from the pressure into these voids, as has happened with 

 the copper. If these receptacles for it have been wanting,, 

 it must have flowed to the external surfaces, and may have 

 formed a crust there. The matter which lines or fills the 

 cavities of some lavas has, perhaps, been so introduced into 

 them. 



A knowledge of the productions of art, and of its opera- 

 tions, is indispensable to the geologist. Bold is the man 

 who undertakes to assign eftects to agents with which he 



