Mr. Smith on the Stream Works of Pcntowan. 407 



Depth from 

 surface 

 Feet Inche* 

 Stratum 4. Sea mud, with large oyster shells and cockles .... 4 39 



5. Vegetable substances, with flat compressed leaves, and a 



few rotten shells 6* 4o\ 



6. Vegetable substances, without ihells; containing rushes, 



fallen trees, flat compressed leaves, roots covered with 

 moss and compressed to an oval form, wings of coleop- 

 terous insects 1 46| 



The trees in 2, 5, and 6, are so numerous, that the miners 

 collect from them great stacks of fire-wood. 



7. At the top are found moss, sticks, hazle nuts. Beneath 



are small stones of killas, growan, and other pebbles, 

 which are known by the miners to have belonged to the 

 neighbouring hills, so far distant as Hensbarrow . . 3 49{ 



8. Rough tin ground, containing the lighter and poorer stones 2 51-f 



9. Rough tin ground, containing rich tin stones, some of great 



size and weight. Mixed with these are rounded pebbles 

 of quartz, and other stones, and a yellow ferruginous 



clay 3 54{ 



10. Solid killas rock, on which all the preceding alluvia were 

 deposited. The level of this does not differ much from 

 that of low water mark. 



In addition to these observations I have not many remarks to 

 offer. The lower work is much richer in metallic produce than 

 the upper, owing probably to the valley being narrower at the 

 former place, which confined the mineral matter within a smaller 

 space, and prevented it from being dispersed in the plain. The 

 stones at the upper work were much the largest, as might be 

 expected from its greater proximity to the hills. Among the tin- 

 stones of both works are found such as agree with the ores of 

 particular lodes, that traverse the several hills all the way up to 

 Hensbarrow hill, and the old miners had themselves made these 

 distinctions, and rendered them perfectly clear to me. Thus, I 

 think, I may venture to say, that the tin stones have been washed 

 down from the neighbouring hills into the Pentowan valley. 



3 f 2 



