1815.] Geological Society. i4f 



rocky mountains. On the verge of these mountains coal has beeri 

 observed ; but the interior part of the ridge is descril)ed as composed 

 of very hard rock, the stratification of which is nearly vertical. 



A notice, accompanied by a very fine specimen of sulphate of 

 strontian, by G. Cumberland, Esq. was read. 



This specimen, with several smaller ones, was found in digging 

 a vault in a burial-ground in Portland-street, Bristol. It is a nodule 

 of considerable magnitude, pretty compact externally, and loosely 

 filled up with crystals of larger size and more perfect figure than is 

 usual in English specimens. 



June 3, — A letter from Edward Smith, Esq. on the sti'eam works 

 at Pentowan, addressed to Dr. Wollaston, was read. 



From the summit of Hensbarrow Hill to the sea-coast is about 

 seven miles. A small river takes its principal rise in the above- 

 mentioned hill, and after a rapid course, in many parts interrupted 

 by cascades, falls into the sea near St. Austle. On hasty rains the 

 rise of this stream is sudden, and often dangerous, but in dry 

 seasons it is an inconsiderable rivulet. In the valley through which 

 h flows are two stream-works, the upper and the lower. 



The upper has been opened to the depth of 40 feet, and consists 

 of six strata, or more properly alluvial beds. The uppermost, three- 

 feet thick, is the surface soil, with trees growing on it : the second 

 is mud mixed with gravel, about 20 feet thick : the third is three 

 feet thick, and consists of fragments of spar and killas ; the fourth^ 

 five feet thick, consists of gravel and decomposed granite, the 

 same as occurs at Hensbarrow Hill; the fifth bed, five feet thick, is 

 gravel, covering large trunks and branches of oak : the sixth bedj 

 five feet thick, is coarser gravel, intermixed with which are rounded 

 pieces of tin-stone. This bed rests not on the rock, but on a kind 

 of clay : it is, therefore, possible that there may be below other 

 alluvial beds which have not as yet been examined. 



The lower stream-work is about three quarters of a mile below 

 the upper ; and, like the latter, consists of a bed of tin-stone, five 

 feet thick, in small rolled pieces, mixed with other fragments, and 

 covered by about 54 feet of alluvial matter in several beds. Some 

 of these are mere gravel ; others are largely mixed with trees and 

 other vegetable matter, among whicli have been found the horns of 

 an animal of the stag kind; some large bones, supposed by Mr. 

 Smith to be those of hippopotamus, and parts of two human skulls* 

 There are also two beds of blue mud, containing marine shells. 



A paper by Dr. Macculloch, being a supplement to a former 

 toinmunicution of his on quartz rock, was read. 



The object of the author in this paper is to confirm, by additional 

 examples, his former ])osition, that quartz rock is essentially com- 

 posed of fragments and rolled pieces, and that it alternates witli 

 mica-slate and otiier rocks, which have hitherto been considered as 

 a primitive. 



June 17. — The reading of Mr. Wynch's paper on the mineralogy 

 of Northumberland and Durham w;is concluded. 



