Correspondence — Mr. J. Hopkinson. 47 



sharp, well-defined lines. From the identity of the age of these Coal-seams with the 

 Permian conglomerate of Alberbury, only fifteen miles distant, he questioned the 

 probability of that conglomerate being of glacial origin, since two climates so 

 dissimilar as a glacial one and that in which a Carboniferous flora flourished could 

 not exist together within so limited an area. In conclusion, Mr. Davies pointed out 

 the necessity for alterations of the boundaries of the Permian and the Coal-measures 

 in any future geological maps of the district. 



2. " Note on a Well- Section at Finchley." By Caleb Evans, F.G.S. The author 

 described ttie various strata traversed by a well recently sunk by the East Barnet Gas 

 and "Water Company at the north end of Finchley. The strata are as follows : 

 glacial clays, gravels, and sands, 55 feet ; London clay (with basement bed containing 

 Gyprina, Fanopcea, etc.), 171 feet; Lower Tertiaries (mottled clay, pebble beds, and 

 sand), 58 feet; chalk with flints, about 216 feet. At this depth a good supply of 

 water has been obtained. 



ooiai^EisiPOisrnDiEi^roEi. 



THE GEOLOGICAL SURVEY IN THE SOUTH OF SCOTLAND. 



SiK, — In reply to Mr. Jack's letter in the December number of 

 the Geological Magazine, I beg to refer him to Mr. Lapworth's 

 commimication in the same number, from which it will be seen that 

 an opinion, practically identical with the one I expressed in the 

 previous number, has for some time been held by Mr. Lapworth, 

 who has thoroughly and completely worked out the inter-relations 

 of the Moffat shales, and from whom I received the first hint that 

 these shales were capable of division, by their fossils, into distinct 

 zones, easily recognizable in localities far apart. 



Pending the issue of the Geological Survey Memoir on the whole 

 Silurian region of the South of Scotland, in which, I infer, from Mr. 

 Jack's letter, the fossiliferous rocks will be distinguished bed by 

 "bed, and all the fossils assigned to their proper zones, I adhere to 

 the conclusion at which I arrived about two years ago, after ex- 

 amining a series of fossils collected by the Geological Survey of 

 Scotland in the Leadhills district, and which is expressed in the 

 Annals of Natural History for May, 1871, viz, that these fossils 

 " parallel the rocks of this locality [Leadhills] with those of Moffat, 

 Dumfriesshire, or with the Llandeilo flags of Wales. 



Mr. Lapworth may perhaps be right in referring some of the 

 higher zones of this Graptolite-bearing shale (which have only come 

 under my observation in the Moffat district) to a higher horizon than 

 the Llandeilo, for they are characterized by the presence of several 

 species which occur in the overlying Gala group, in its representa- 

 tive, the " Graptolitic-mudstone " of Westmoreland, and in Barrande's 

 etage E. in Bohemia, while they have not yet been found in the 

 Llandeilo rocks in Wales. Whether, however, a series, away from 

 the Welsh area, should be referred to the summit of the Llandeilo 

 or to the base of the Bala group, is a matter, at present, of no great 

 moment. I refer to it here to show that, in describing my new 

 species of Graptolites as " Graptolites of the Moffat Group," I was 

 not unaware that a division of the beds in which they occur might 

 be possible after a careful survey of the whole region ; but, while 

 fully acknowledging the admirable manner in which Mr. Jack has 

 mapped and described those portions of the Silurian region of the 

 South of Scotland which he has himself examined, I cannot concur 



