70 Proceedings of Philosophical Societies. [July, 



A paper was read from A. S. Lillingston, Esq. on granite veins 

 and whin dykes, in which he explains these appearances on the 

 supposition that the beds containing the veins were deposited 

 upon the mass of which the vein is a portion, while that mass 

 was in a fluid state ; and that the deposited beds were the first 

 to become hard, in consequence of which they contracted, thus 

 occasioning fissures which were subsequently filled by the sub- 

 jacent fluid mass. 



The author also supposes the red marl stratum to have been 

 produced from the destruction of beds of whin stone, fragments 

 of which abound in it, as may be observed in Devonshire, North- 

 umberland, and other places. 



A letter was read, from the Rev. W. Gilpin, on certain fossil 

 bones found near Margate. These bones, in the state of frag- 

 ments, occur in the hard, white, calcareous clay which overlies 

 the extremity of the chalk cliff extending along the coast to the 

 westward of Margate. The bones lie at least 10 or 12 feet 

 below the surface, and are surrounded by a dark, friable sub- 

 stance, similar to decayed animal matter. 



April 17. — A second paper was read, from George Cumber- 

 land, Esq. on some new encrinital and pentacrinital bodies 

 found in the nighbourhood of Bristol. It affords much interest- 

 ing and curious information concerning the class of bodies of 

 which it treats, but which cannot conveniently be detached 

 from the illustrative series of drawings by which it is accom- 

 panied. 



May 1. — A paper was read, from George Cumberland, Esq. 

 consisting of a descriptive catalogue of specimens of the Bristol 

 limestone beds, from their transition from the sandstone to their 

 termination, at a place called Cook's Folly, nearly the whole of 

 which Mr. Cumberland has measured. The series consists of 

 above 300 beds, from one inch to 30 feet in thickness. 



A paper was read, from Francis Lunn, Esq. on the strata of 

 the northern division of Cambridgeshire. 



Mr. Lunn observes that the ferruginous sand is the lowest 

 stratum found in Cambridgeshire ; on this rests the blue marl, 

 having in many places the line of their junction very well defined : 

 the sand contiguous to the clay is generally cemented by a large 

 portion of oxide of iron into a hard, rocky substance. The sand 

 contains fossil wood ; the clay contains carbonate and sulphate 

 of barytes. The temperature of the water in all the wells sunk 

 through the clay, is about 47° Fahrenheit, and is nearly invari- 

 able throughout the year. 



May 15. — The following notices were communicated by 

 M. Leman, M.G.S. through Mr. Heuland, For. Sec. 



On Mica. — M. Biot has lately divided this mineral into two 

 species. When submitted to the action of polarized light, the 

 coloured rings which are produced are traversed in the first 

 species by two axes in the form of a black cross ; and in the 

 second species by a second axis or black band, passing through 



