480 Correspondence — Mr. A. Somermil and Mr. T. M. Reade. 



not only strongly intrusive, forcing itself through and among the 

 schists, but one of the sections exhibits in the clearest possible way 

 the former involving great masses of the latter rock. Besides 

 bursting through the hornblende slates, the serpentine actually 

 infuses itself into their composition at and near the junctions, so as 

 to form a kind of transition between the two rocks of opposite origin, 

 which Mr. Collins has very evidently mistaken for serpentine in 

 a less altered form, thus seeming to favour his mistaken conclusion 

 of the serpentine being only an altered hornblende slate. 



Not only do I consider the views held by Prof. Bonney on this 

 point as strictly correct and in perfect accordance with those of the 

 late Sir H. T. De La Beche, but I would have thought it almost 

 impossible for any observer to misinterpret the sections in a locality 

 where the evidence is so clear and decisive. 



ToKauAY, August 23, 1884. Alex. SoMERVAlL. 



THE ISLAND OF SOUTH GEORGIA. 



Sir, — Mr. Fisher's reasoning upon this island in connection with 

 the supposed permanence of oceanic areas appears to me to lead to 

 precisely the opposite conclusion to that at which he has arrived. 

 The island of South Georgia, as I have before pointed out, is 

 separated from the continent of South America by 1200 miles of 

 ocean — at least all maps represent it so. 



If, as Mr. Fisher infers, it had a former land connection with 

 South America, I think most people would see in that fact a tolerably 

 convincing proof of the loant of permanence in oceanic areas. 



Park Corner, Blundellsands, T. MifiLLARD Eeade. 



Sept. 2nd, 1884. 



nvnisc:E]ijij.A_ziTEOTJS. 

 Borough of Nottingham. Annual Eeport of the Medical 

 Officer of Health for 1882. By Dr. E. Seaton. (8vo. 

 Nottingham, 1883). — This Eeport contains a Geological Map of the 

 Borough, on a scale of 3^ inches to a mile, which is founded on the 

 Map of the Geological Survey, but " re-surveyed and amended in 

 detail " by Mr. J, Shipman, whose work has been approved by Mr. 

 W. T. Aveline. The construction and publication of such a map is 

 a good practical illustration of the want that is felt of geological 

 maps of larger scale than an inch to the mile, that latter scale being 

 too small for most practical purposes ; and it is to be hoped that 

 the ofScers of the Geological Survey will be instructed to carry out 

 the new work that they may have to do on maps of large scale, and 

 thus make their work in the Southern and Midland Counties of far 

 greater value than now. Certainly such mapping should not be 

 left to private or corporate enterprise. There is one defect in the 

 map now noticed, namely, that Drift is not shown on it, except for 

 the gravel that is included with the alluvium, and for some strips 

 apparently marked by fine dotting and by lettering. For sanitary 

 purposes these irregular cappings of gravel, clay, etc., are amongst 

 the most important matters. 



