113 



and to have the form of a bowl, 10 or 12 miles in circumference, into 

 which the sea flows by a narrow opening, capable of admitting a 

 boat. The surface of the island is, in many places, covered with 

 pumice, and at night flames were observed to issue from various 

 crevices in the rocks. With the exception of the island of Amster- 

 dam, about 40 miles to the north of it, St. Paul's is ata great distance 

 from any land. 



In the hole from which the water was taken the thermometer 

 stood at 212°. 



Dr. Bostock then explains the manner in which he conducted the 

 examination, and gives the following as the earthy constituents of 

 100 grains of the water: 



Muriate of soda 2'3 grains. 



Sulphate of soda "053 



Muriate of lime 'S^O 



Muriate of magnesia "059 



Loss -038 



2-790 

 * He afterwards compares these results with those obtained by 

 Dr. Marcet from water procured from the middle of the South At- 

 lantic ; and from the great difference in the saline contents, infers 

 that the water of the island of St. Paul is not merely the water of 

 the neighbouring ocean in a state of dilution, or altered simply by 

 mechanical filtration. 



A paper " On the chalk and flint of Yorkshire, compared with the 

 chalk and flint of the southern counties of England," by James Mit- 

 chell, LL.D., F.G.S., was then read. 



The chalk of Yorkshire, Dr. Mitchell states, is distinguished from 

 that of the southern counties by its great hardness, by its being 

 occasionally of a red colour, by its being more distinctly stratified, 

 and by its containing veins of calcareous spar. He says, that it is 

 also distinguished by the upper part being always destitute of flints, 

 while in the southern counties the absence of flints in the upper 

 part is an exception. 



The flints of Yorkshire are shown to differ from those of the 

 southern counties by their being almost invariably of a tabular form, 

 constituting regular and well-defined continuous layers ; by being 

 tougher, and breaking into short small fragments, unfitted for the 

 manufacture of gun flints ; by the colour being always greyish or 

 whitish throughout the whole thickness ; the crust not being of a 

 different character from the body of the flint. Nodules of iron pyri- 

 tes are stated to be common in the Yorkshire chalk, but in that of 

 the South of England to be confined to the lower chalk without 

 flints. 



In conclusion the author points out the following resemblance 

 between the Yorkshire chalk and that of the N.E. of Ireland, namely, 

 the great hardness of both, and the common occurrence in both of 

 iron pyrites and veins of calcareous spar. 



