42 RAMBLES AND REVERIES. 



had recourse to, and these, no doubt, accompanied 

 the intrusion of the granite and the metals into the 

 rocks through which they poured when in a state 

 of fusion. Mr. J. H. Collins, who has paid great 

 attention to this subject, is of opinion that the 

 decomposition of the felspar and the consequent 

 formation of the Kaolin arose from the long con- 

 tinued action of water or steam containing hydro- 

 fluoric acid. Traces of fluor are met with in the 

 granite at many places, and frequently the Kaolin 

 is in proximity with metalliferous veins, while in 

 many cases the clay deposits run along for miles in 

 the direction of tin veins, although they may be 

 only a few feet in breadth. 



The outside surface-workings are very interesting. 

 Generally the clay has to be raised from a lower 

 level than the neighbouring ground. To effect this 

 a shaft is sunk, and from the bottom of this a level 

 is cut out underneath the clay that is to be worked. 

 An artificial arrangement of water channels leads 

 to the wearing down of the clay, which then hangs 

 suspended in the water, and this is pumped up from 

 the pit to the surface, usually to a somewhat higher 

 level than the ground, so as to allow of subsequent 

 operations and washings to be carried on by the 

 down-flowing of the water under the action of 

 gravity. In the wider channel the sand is de- 

 posited ; in the next, the finer mica is obtained, 

 which is not quite without value. The stream, 

 thus gradually purified, passes on to the first pits, 

 in which the clay settles to the bottom, and the 

 water runs off to be used over and over again. In 



