E, B. Bailey — Drakes Island, Plymouth. 263 



Volcanic ltocks. I have not found any evidence in Drake's Island 

 bearing upon this point, and have therefore contented myself with 

 a description of the rocks as they lie. If Mr. Ussher is correct, 

 then the superpositions referred to presently are merely the result 

 of inversion. All the rocks of the district, except the massive 

 limestones, show a strong cleavage, so that there is no difficulty in 

 admitting that such an inversion may exist. 



My notes on Drake's Island were written down in the hope that 

 they might be of value to those who make a study of the geology of 

 the neighbouring mainland. During the winter 1915-16 1 had 

 several opportunities of going round the shores at low-water, so that 

 it has been easy to clear up certain points, which have hitherto 

 remained in doubt. 



O TOO 200 300 400 5QO 600 YARDS 

 I 1 I I I I ! 



Map of Drake's Island, Plymouth. 



Publication of a map of Drake's Island was forbidden so long as 

 hostilities continued, and the resultant delay makes it possible to 

 refer here to an important paper which has appeared in the interval. 

 Mr. E,. H. Worth, 1 a son of the late E,. JS". Worth, has given an 

 account of the igneous rocks of Plymouth. It is true that our 

 districts scarcely come in contact, since, while the War put one of 

 us temporarily on to Drake's Island, it kept the other off; at the 

 same time our subjects do seem to overlap, and it is only fair to 

 state that Mr. Worth is of opinion that the so-called lavas of 

 Plymouth are all intrusive, and that their associated fragmental 

 rocks are intrusion-breccias. Experience of Drake's Island and 

 a study of Mr. Worth's descriptions and figures do not tend to 

 confirm this intrusion hypothesis. At the same time one cannot but 

 welcome the additional data supplied in many particulars ; and 

 certain of his results will be made use of in their appropriate 

 connection in the sequel. 



A representative suite of specimens collected from Drake's 

 Island is now in the possession of the Geological Survey (E 11402— 

 11414). The lava D of the sketch-map is uniformly fine-grained, 



1 "The Dunstones of Plymouth and the Compton-Efford Grit " : Report 

 and Transactions of the Devonshire Association for the Advancement of 

 Science, Literature, and Art, vol. xlviii, p. 217, 1916. 



