1872.] OLDHAM AND MALLEI CACHAR BAKTHQUAKE. 255 



Wealden formations, — limestones, remains of land-surfaces and " dirt- 

 beds," and thick intercalated marine beds being abundant iri the 

 former and comparatively absent in the latter, and there being an 

 equally marked difference in the organic contents of the two forma- 

 tions. He considered the Purbeck formation to have been deposited 

 in a lagoon subject to occasional invasions of the sea, while the 

 Wealden was in fact a large delta. Though both were of fresh- 

 water origin, they were deposited under totally different conditions, 

 the Purbeck formation representing a deposit of a lacustrine nature 

 in tranquil water, and the Wealden a deposit in an estuary. 



Prof. Morris, alluding to the pseudomorphs of salt mentioned by 

 the author, stated that they had been somewhat compressed, and 

 thus modified in form. They had also been found in other beds in 

 the Wealden. He commented on the extension of the Wealden strata 

 even to the south of Moscow. In the Oxford and Buckinghamshire 

 area there was evidence of great denudation of the Purbeck and 

 Wealden beds prior to the deposit of the Neocomian ; so that great 

 changes would seem to have taken place, giving rise to a great 

 amount of denudation towards the close of the Wealden period. 



Mr. Meyer agreed with Mr. Godwin -Austen and other speakers 

 as to there having been a certain amount of denudation of the 

 Tipper Wealden beds prior to the deposit of others upon them ; but 

 this he regarded as merely local. It was the absence of shingle, 

 rather than of gravel, to which he had alluded in his paper. He 

 thought that there was a distinction to be traced between the Neo- 

 comian of the north of England, and that of the south, and that the 

 middle beds of one were equivalent to the lower beds of the other. 



April ] 0, 1872. 

 The following communication was read : — 



Notice of some of the Secondary Effects of the Earthquake of 

 10th January, 1869, in Cachar. Communicated by Dr. Oldham, 

 F.E.S., F.G.S., Calcutta. With Bemarl^s by Robert Mallet, Esq., 

 C.E., E.E.S., F.G.S. 



The following communication has been delayed in being brought 

 before the Geological Society in the expectation of receiving further 

 facts from Dr. Oldham, or that he would publish a substantive 

 account of his own results after his examination of the earthquake- 

 region. 



The latest communications received, however,by the writer from Dr. 

 Oldham render it doubtful whether he will be able, consistently with 

 the pressure of his official duties, to pursue the subject further ; and 

 as the facts which he has collected and well explained, of the produc- 

 tion of enormous earth-fissures as effects of this earthquake, are of 

 great importance, the writer has deemed it best to place them on 



