382 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 8, 



The author also mentions, as an indication of the mode iu which 

 these islands are formed, the furrowed appearance which some of 

 them present. Of Atapu, or Duke- of- York Island (Union group), 

 the shore, and of Peru (Gilbert group) the whole island, appear 

 to be formed by a series of mound-like ridges, that nearest the sea 

 forming the beach. They vary in width from 20 to 50 feet ; and 

 the furrows separating them are 4 to 6 feet deep. They consist of 

 fine coral debris ; and, from information which he received, the 

 author considers that each mound is the product of a single gale, 

 although it may be added to during subsequent rough weather. 



The author also notices a freshwater lagoon, about three miles in 

 diameter, on Quiros, or Gente-Hermosa Island, and states that the 

 water was only very slightly brackish. There is no communication 

 between the lagoon and the sea, although there are signs that the 

 connexion must have been closed at a comparatively recent date. 

 The water in the lagoon does not appear to be affected by the rise 

 and fall of the tides ; and the author thinks that its surface is above 

 the sea-level. He indicates the difficulty of accounting for the 

 presence of this body of fresh water in so small an island, and 

 inclines to adopt for this and the neighbouring island of Lakena, 

 which also possesses a freshwater lagoon, the hypothesis that they 

 have originated from the craters of extinct volcanoes. 



DlSCTTSSIOl^. 



Mr. Thorp was acquainted with the atolls around the coast of 

 Ceylon, and thought that the local traditions, untrustworthy as such 

 sources usually were, might afford some evidence as to the date of 

 their origin. The tradition in Ceylon was that the Maldive and 

 Laccadive Islands had within the memory of man been connected 

 with Ceylon. If they were so, the evidence was in favour of the a 

 being one of subsidence. 



Mr. D. Forbes, when in 1859 he spent some months in the Pacific, 

 had been requested by Mr. Darwin to examine into the evidence as to 

 the origin of these atolls by elevation, and had found that the asserted 

 cases of the existence of masses of coral at a considerable elevation 

 above the sea merely arose from blocks having been transported inland 

 by the natives. Though, however, there was no evidence of eleva- 

 tion, it was still possible that such had in certain cases taken place, 

 as there were still active volcanoes in this region. The freshwater 

 lakes he attributed to the drainage of the islands. 



2. On the Glacial Phenomena of the Yorkshire Uplands. 

 By J. R. Dakyns, Esq. 



(Commnnicated by Prof. Eamsay, F.E.S., RG.S,, &e.) 



The Carboniferous hiUs that form the central axis and backbone of 

 Northern England sink beneath the Triassic plain near the town of 

 Derby, Between Derby in the south and Wensleydale in the north. 



