ON THE ERRATIC BLOCKS OF ENGLAND, WALES, AND IRELAND 267 



Tiventieth Report of the Committee, consisting of Professor J. 

 Pkestwich, Dr. H. W. Crosskey, Professors W. Boyd Dawkins, 

 T. McK. Hughes, and T. Gr. Eonney and Messrs. C. E. De 

 Eance, p. F. Kendall, W. Pengelly, J. Plant, and K. H. 

 Tiddeman, appointed for the purpose of recording the Position^ 

 Height above the Sea, Lithological Characters, Size, and Origin 

 of the Erratic Blocks of England, Wales, and Ireland, reporting 

 other mailers of interest connected ^vith the same, and taking 

 measures for their preservation. {Draion up by Dr. Crosskey, 

 Secretary.) 



The researches of this Committee have been carried on during the past 

 year with the assistance of the Yorkshire Boulder Committee — the 

 Glaciahsts' Association (formerly the N.W. of England Boulder Com- 

 mittee, and whose contributions are marked*) — and several independent 

 observers. 



In previous reports the facts obtained by an exhaustive survey of the 

 erratics of the Midland Counties have been classified, and a series of 

 valuable results has thus been established. 



It has not as yet been possible to extend the same kind of treatment 

 to other districts on account of the constant accumulation of new 

 material, such as that of which the report of this year contains fresh 

 instalments. 



The facts discovered are, however, rapidly showing that they are 

 capable of orderly arrangement, and it cannot be doubted that the dis- 

 tribution and gi'ouping of the erratic blocks of Great Britain will thr-ow 

 light on some of the most intricate questions of Glacial Geology. 



The following reports have been received : — 



The Yorkshire Boulder Committee, 



Chairman : Professor L. C. Miall, F.B.8., F.G.S., F.L.S., Yorkshii-e 



College, Leeds. 



The Yorkshire Boulder Committee have comparatively few eri'atic 

 blocks to report this year, nearly all the known examples having been 

 previously recorded. This being the case, they have been at liberty to 

 make important advances in their methods of research and to devise new 

 modes of operation. 



During the year their attention has been mainly given to maturing a 

 scheme for the careful and exact exploration of special glacial districts 

 not hitherto adequately investigated. They began with the valley of the 

 River Calder, including its tributaries, from its source to its junction 

 with the River Aire, near to Castleford, This valley has been subdivided 

 into geographical areas, each of which is now placed under the supervision 

 of a sub-committee. The results of this exploration they hope to embody 

 in their next annual report. They intend also to present a similar 

 report on the Sedbergh, Garsdale, and Dentdale district, now being 

 investigated after the same fashion. 



During the past year a sub-committee has been engaged upon the 

 preparation of a new and enlarged glacial map of Yorkshii'e on a scale of 



