Reviews — Wynne's Geology of Bombay. 165 



We have now discharged a very disagreeable duty, in pointing out 

 what seem to us grave errors in this work, and have left but little 

 room for further remarks. We may notice, however, that the account 

 of the Physical Geography of the county is fairly executed, and we 

 are not without hope that the book may be useful to the beginner, by 

 pointing out what he is to expect to meet with in the district de- 

 scribed, and Avhat spots are best worth a visit. More than this he 

 must not look for, but must take the field, and touch, taste and 

 handle for himself if he wants thoroughly to be master of his 

 subject. 



n. — On the Geology of the Island of Bombay. 

 By A. B. Wynne, F.G.S., etc., Geological Survey of India. 



THIS paper forms a part of the fifth volume of the Memoirs of the 

 Geological Survey of India, a series of publications containing 

 many valuable and interesting papers on those portions of India 

 which have been investigated during the progress of the Geological 

 Survey, under the able direction of Professor Oldham. The island of 

 Bombay has been carefully surveyed by Mr. Wynne, who, after 

 alluding to the researches of previous observers, to whom he does 

 full justice, has now given a detailed description of the arrangement 

 of the rocks of Bombay Island. He shows that the geological 

 structure of the island is closely allied to that of the neighbouring 

 coast, and other portions of Western India, although it presents 

 local differences. The physical features of the island are intimately 

 connected with its geology, as modified by denudation ; the form of 

 the ground, and elongate shape of the -island, depend on two main 

 ridges or chains of hills consisting of igneous (trappean) rocks, sepa- 

 rated by alluvium and other superficial deposits, which foiin a central 

 plain. The longer and more gentle slopes of the ridges are to the 

 west, and the steeper sides to the east, coinciding in a general way 

 with the planes of stratification, which have a more or less westerly ■ 

 dip. The whole island presents an ascending series of stratified 

 trappean and aqueous rocks, commencing with the black basaltic 

 rock of Seoree on the east, succeeded by the traps and shales of the 

 eastern hills, which are overlain again by the shaly beds seen on 

 both sides of the flats, and terminated by the basaltic beds of 

 Malabar ridge and Warlee. The rocks present many varieties, some 

 resembling Greenstone Melaphyre, Felstone, others different forms 

 of trap, both silicious, compact, white, and amygdaloidal, volcanic 

 breccia, and also various kinds of ferruginous and flaky ash, and the 

 intertrappean shales, sandstones, and flags, derived apparently from 

 the mechanical disintegration of trappean rocks. 



The shale series contains remains of reptiles, amphibians, insects, 

 mollusca, with leaves, stems, and seeds of plants, suggesting their 

 freshwater origin, but these deposits have been traced only a short 

 way beyond Bombay Island, from which Mr. Wynne infers that 

 trappean flows approaching from opposite sides left shallow basins, 

 which became repositories of mud and sand, the results of the 

 disintegration of trap, washed down by rain during long intervals, 



