456 Proceedings of Philosophical Societies. [June, 



of this latter rock. The most important of these beds are the 

 lias and the chalk. 



The lias here, as in England, consists of beds of slate clay, 

 alternating with thin beds of bluish, argillaceous limestone. Its 

 characteristic fossils are ammonites, gryphites, and the columnar 

 joints of the pentacrinus. In many places it may be clearly be 

 observed emerging from below the green sand, and rests on red 

 marl containing gypsum. At the peninsula of Portrush it comes 

 in contact with tabular and prismatic greenstone, being covered 

 by, and appearing to alternate with, this rock. Under these 

 circumstances it assumes the appearance of a very compact and 

 highly indurated, flinty slate, retaining, however, numerous 

 impressions of ammonites, which sufficiently identify it with the 

 slate clay of the lias, altered by the action of the greenstone. 



The beds of oolite and calcareous standstone, &c. which in 

 England intervene between the lias and the green sandstone, have 

 not been observed in this district ; the latter rock, therefore, 

 rests immediately on the lias. It is not materially different from 

 the green sandstone of the English series. 



The chalk of this district, although perfectly identified, geo- 

 logically speaking, with the chalk of England, by its relative 

 situation in the series, and by the organic remains which it 

 encloses, differs, in the following particulars, from the usual 

 appearance of this substance. It is harder, and its texture is 

 more compact. It is covered, and often intersected by basalt ; 

 in the latter case, and near the plane of contact, the chalk is 

 converted into a dark-brown, crystalline limestone, which, as it 

 recedes from the basalt, becomes more fine grained, then of a 

 sandy aspect, afterwards porcellanous, and at the distance of 

 eight or ten feet from the basalt is not to be distinguished from 

 ordinary chalk. The flints in the altered chalk usually assume a 

 grey, yellowish colour, and the chalk itself, when exposed to 

 heat, is highly phosphorescent. 



{To be continued.) 



Article XVII. 



Proceedings of Philosophical Societies. 



ROYAL SOCIETY. 



April 23. — Dr. Wollaston communicated a paper by Dr. An- 

 drew Ure, entitled, New Experimental Researches on some of 

 the leading Doctrines of Caloric, particularly on the Relation 

 between the Elasticity, Temperature, and latent Heat of different 

 Vapours, on thermometrical Admeasurement, and on Capacity. 



April 30. — The reading of Dr. Ure's paper was finished. It 



