J. W. Davis — Erratic Boulders of the Colder Valley. 313 



and agricultural purposes. " Some idea," he says (T. R. G. S. Corn, 

 vol. vii. p. 31), "of the vast quantity of sand thus abstracted (for 

 manure) may be formed by the fact that a very usual clause in farm- 

 ing leases in this neighbourhood is, ' That ten butt loads of sea sand 

 shall be spread on every acre whenever it is broken for tillage.' " 

 This explanation is a very plausible one, and, coupled with the 

 hypothesis before mentioned, would be a powerful adjunct in ac- 

 counting for more rapid recent waste. Great quantities of commi- 

 nuted shell sand are also carted from Bude by the farmers of North- 

 west Devon. 



In conclusion, I have to express my sincere thanks to Mr. W. 

 Whitaker, Dr. C. Le Neve Foster, and to Mr. E. Parfitt, of Exeter, 

 for kindly furnishing me with all the information in their power 

 concerning the literature of the subject; to Mr. Robert Hunt, F.R.S., 

 Keeper of the Mining Records, for placing at my disposal some beauti- 

 fully executed sections of the St. Agnes deposits by Mr. A. C. Davies, 

 some of which I have submitted to the Geological Society in a reduced 

 form ; also to Mr. Horace B. Woodward for the kind interest he took 

 in this paper in its original form, and the information he obtained for 

 me as to the best means of insuring its publication. 



VI. — On the Source of the Erratic Boulders in the Valley 

 of River Calder, Yorkshire. 



By James W. Davis, F.S.A., F.G.S., etc. 



THE reference, in my paper on the Calder Valley, to the extensive 

 deposits of boulders and sand which fill up the lower part of 

 the valley, and form a series of long level surfaces, is necessarily very 

 brief. It may assist a proper understanding of the subject, and the 

 point raised in Mr. Dakyns' letter, if I recapitulate, as briefly as 

 possible, the main facts of the case. The river has its source in two 

 or three small streams which rise in the hills on the Lancashire side 

 of the Pennine Anticlinal. These are joined into one stream, and 

 pass along a narrow but deep valley cut at right angles to the range 

 of elevated gritstone hills which form the boundary between Lanca- 

 shire and Yorkshire. For five or six miles the valley is rarely more 

 than about 200 yards in breadth, and on each side the slopes of the 

 hills are extremely steep, composed of shales, surmounted by a pre- 

 cipitous gritstone escarpment. At Hebden Bridge the Calder 

 is joined by the Hebden, and in its course south-eastwards the 

 valley gradually assumes larger dimensions, and south of Halifax 

 spreads out into extensive level plains, along which the Calder has 

 carved its channel with many devious turnings. On reaching the 

 district from Mirfield to Wakefield these characteristics are still more 

 apparent, its path being amongst the softer beds of the Coal-measures. 

 Below Wakefield to the confluence of the Calder with the Aire at 

 Castleford, the country generally is of a comparatively flat and un- 

 interesting nature. 



The lower reaches of the valley are filled with great quantities of 



