Geological Soeiety of London. 331 



lar's Island, in the rapids of the river Trent (flowing into the 

 head of Lake Ontario), has been removed within the last eighteen 

 months. Patrick's Island, a mile lower down, is also rapidly dis- 

 appearing. Salmon Island, in Bay of Quinte, between Amherst 

 Island and the mainland, which had an area of about an acre fifty 

 years ago, has disappeared, leaving a shoal, with about 4 feet of water 

 over it ; and three neighbouring islets, known as the Brothers, are 

 in course of removal. The removal of these islands is due to the 

 action of drift-ice. The author also referred to the formation of 

 ground-ice in the Canadian rivers. 



Discussion. — Prof. Ramsay mentioned that Sir "William Logan had informed him 

 that shore-ice in Canada, charged with boulders, had been known to produce grooves 

 on the face of cliffs as well marked as those of glacial times. He had also mentioned 

 the case of a boulder transported by ice which was of such a size as to have occasioned 

 the wreck of a vessel which had struck upon it. 



II.— May 22, 1872.— Prof. Morris, V.P., in the Chair.— The 

 following communications were read : — 1. A communication from 

 the Kt. Hon. Earl Granville, inclosing a report from H. M. Minister 

 at Eome relating to the recent Eruption of Vesuvius. 



2. " On the Phosphatie Nodules of the Cretaceous Eock of Cam- 

 bridgeshire." By the Eev. 0. Fisher, M.A., F.G.S. 



This paper contained an attempt to explain the origin of the 

 phosphatie nodules which lie in a thin bed at the base of the Chalk 

 in Cambridgeshire, and are largely extracted by washing the 

 stratum for the purpose of making superphosphate of lime. Two 

 hundred and seventy tons per acre, at the rate of fifty shillings a 

 ton, represents the valuable yield of the deposit, which is followed 

 to the depth of about 18 feet. The nodules and other fossils of the 

 bed are chiefly derivative, forming a concentrated accumulation 

 from a deposit belonging to the Lower Cretaceous period. Some of 

 the fossils are, however, believed to be indigenous to the deposit. 

 Plicatulm are attached to all the derivative fossils and nodules, and 

 the sharp broken surfaces of the latter, with Flicatulce on them, 

 show that they were mineralized before they were deposited in their 

 present gisement. The green grains of chlorite have been drifted 

 into patches. Certain calcareous organisms are preserved, but many 

 genera of mollusks only occur as casts in phosphate of lime. The 

 phosphatie matter has been determined in its deposition by animal 

 substances. There are two chief varieties of the " ordinary " no- 

 dules. The first are amorphous, or else finger-shaped; the second 

 formed like a long cake rolled partially or wholly upon a stick. The 

 surface of these two kinds of nodules is coriaceous and wrinkled, 

 and they usually show marks of attachment to some foreign body. 

 Certain species, clearly zoophytes, are converted into phosphatie 

 nodules, and, when sections are made of these, they are found to 

 show under the microscope structures and spicula allied to those of 

 Alcyonaria. Slices of the common nodules show similar spicula, and 

 occasionally reticular structure. When casts in plaster are made 

 from Alcyonium digitatum, and coloured to resemble the nodules, 

 the similarity in general form and structure of surface is very 

 striking. The phosphate was probably segregated by the animal 



