Some remarkable Boulders in the Isle of Man. 217 



On the Source of some remarkable Boulders in the 

 Isle of Man. By Percy F. Kendall, F.G.S. Com- 

 municated by Thomas Kay. 



{Received March 26th, 18 gi.) 



The determination of the source whence the erratic 

 blocks of any given area have been derived has always 

 appeared to me to be the first, and at all times the most 

 important, part of the work of a student of Glacial 

 Geology. In comparison with it such details as the 

 character, and, especially, the colour of the deposits, must 

 be assigned an altogether subordinate importance. The 

 erratics of Lancashire and Cheshire have long been well- 

 known, so far as regards their general grouping ; and the 

 labours of such investigators as Mr. DeRance, Mr. Mackintosh, 

 and Mr. Mellard Reade, have made geologists familiar with 

 the fact that, in the area in question, the far-travelled 

 erratics, with some half-dozen of individual exceptions, are 

 traceable to a source within the area draining into the 

 Northern and North-eastern portion of the Irish Sea. The 

 exceptions to this rule are, certain Ophicalcites which have 

 been met with on the Ship Canal near Barton, and two 

 specimens of a coarse Ophitic Dolerite — one found near 

 Congleton, and recorded by Messrs. Coutts-Antrobus and 

 Hatch,* and the other found by myself on the Ship Canal, at 

 Bob's Bridge, near Moore. The flints, which are to be found 

 in almost every section in the Lancashire lowlands, are — 

 so far as I can ascertain — invariably beach- or river-worn 

 pebbles, and, therefore, not of any value as indications of 

 the direction of transport. 



* Brit. Assoc. Report, 1890. 

 N 



