2i2 Yorkshire Boulder Committee: Fifteenth Year's Work. 



of a fuller examination will be presented in the next report of 

 the Committee. Meantime it may be remarked that the striking- 

 disproportion which must exist between the boulders of the 

 Cheviot granite and those of the porphyrites will perhaps find 

 an explanation in the conditions which prevailed in the Cheviots 

 themselves during- the time when the distribution of the erratics 

 was in progress. 



Mr. Stather's numerous records of greywackes of a similar 

 type in various parts of Yorkshire and on the lower slopes of the 

 Cheviots sug-g-ests the probability of their derivation from the 

 basin of the Tweed. Two very remarkable discoveries are 

 reported by Mr. Fearnside. The gravels of the Yorkshire 

 Calder have long- been noted for remarkable uniformity in the 

 character of the included stones ; besides local rocks there had 

 been found nothing but well-defined types of Lake District 

 rocks, andesites, agglomerates, and the granitic rocks of the 

 Buttermere and Eskdale types, all such as might have come by 

 way of Lancashire from the western side of the Lake District, 

 and perhaps one or two examples of the Galloway granites. 

 Mr. Fearnside now adds the Norwegian rhomb-porphyry, 

 brockram, brown flints, and Shap granite — discordant elements 

 difficult to reconcile with the very consistent series previously 

 known. Mr. H. H. Corbett, of Doncaster, points out a singular 

 fact : the three boulders of Shap granite found respectively at 

 Royston, Adwick, and Balby have a vein of felspar running 

 through each of them. 



Mr. Corbett has sent the Committee two Ordnance Maps of 

 the district around Doncaster, upon which the distribution is 

 shown of — 



1. Boulder Clay. 



2. Peat and Warp. 



3. Gravels comprising principally Triassic pebbles. 



4. Gravels comprising principally Coal Measure pebbles. 



5. Gravels comprising both Triassic and Coal Measure 



pebbles. 



These maps appear to show that while Coal Measure rocks are 

 found to the east of the Coal Measures of Yorkshire, the 

 Triassic pebbles are found to the west of the Triassic area in 

 the district. In part of the area mapped the two are mixed. 



Mr. Corbett writes : — Nearly all these gravels are strongly 

 current-bedded, the dip being always towards the south-east. 

 This is the case even with gravels on the south-east side of the 



Naturalist, 



