Correspondence — Prof. T. G. Bonne//. 573 



Cirencester and Andoversford, are described in detail by Prof. 

 Allen Harker and Mr. S. S. Buckraan. 



Prof. Harker's contribution is " On the Sections in the Forest 

 Marble, and Great Oolite Formations, exposed by the new railway 

 from Cirencester to Chedworth." The diagram he gives is un- 

 fortunately very much cramped, but it serves as an index to the 

 localities mentioned. Mr. Buckman gives an account of " The Sections 

 exposed between Andoversford and Chedworth : a comparison with 

 similar strata upon the Banbury line." These sections are mainly 

 in the Inferior Oolite, whose many local subdivisions are duly noted. 

 There is also a short paper, accompanied by a plate, by Mr. E. 

 Wethered, " On the Occurrence of Fossil Forms of the Genus Chara 

 in the Middle Purbeck Strata of Lulworth, Dorset." 



GOBEESPOlTDElsrGE- 



ME. SOMERVAIL'S CONTRIBUTIONS TO THE PETROLOGY OF 

 THE LIZARD. 



Sir, — During the last three years the Geological Magazine has 

 been augmented by four communications from Mr. Somervail on 

 the Petrology of the Lizard. These I have refrained from noticing 

 (beyond making in one case a brief protest), because I wished to 

 re-examine the whole district before writing anything more on the 

 subject. Last summer I had the advantage of spending some time 

 at the Lizard in company with General McMahon and the Rev. E. 

 Hill, and we hope to bring the results of our examination before 

 the Geological Society during the present session. 



To point out the errors in observation and inaccuracies of induction 

 in Mr. Somervail's papers would occupy far too much space in the 

 Magazine and weary the patience of your readers. I must content 

 myself with a general expression of opinion as to the dominant idea 

 in each communication. First, "On a Remarkable Dyke in the 

 Serpentine of the Lizard." l This is a group of separate dykes, 

 diorite and granite, the latter containing some fragments of an 

 older rock, and associated with a cpjartz-felspar vein ; it is no part 

 of the " granulitic group," as I have defined it, and gives no support 

 to Mr. Somervail's notion of rocks of different composition segre- 

 gating from one magma. 



(2). " On a Breccia and an Altered Schist at Housel Cove, Lizard." 2 

 Here the ordinary hornblende schist has been cut by a dyke, and a 

 fault running nearly along one surface of junction has brecciated the 

 latter. Perhaps this dyke differs a little in composition from the 

 types which are common at the Lizard, and there is a good example 

 of fault breccia. As usual both rocks are rotten, but the section 

 leads to no particular conclusions. 



(3). "On the Greenstone and Associated Rocks of the Manacle 

 Point." 3 This section is a difficult one, and there are points which 



1 Geol. Mag. 1888, Dec. III. Vol. V. p. 553. 



2 Geol. Mag. 1889, Dec. III. Vol. VI. p. 114. 



3 Geol. Mag. 1889, Dec. III. Vol. VI. p. 425. 



