JRevieivs — Geological Society of Glasgoic. 567 



have been forced to bulge ujDwards by the intense vis a tergo ; and 

 such, upward movement of the ice, being again and again repeated, 

 imprisoned boulders and debris would be compelled just as often to 

 rise to higher and higher levels." 



In the note by Mr. D. Eobertson, " On the Precipitation of Clay 

 in Fresh and Salt Water," it is shown there is a great difference 

 between the two — fresh- water holding the clay in suspension for a 

 considerable time ; while water only slightly brackish has the power 

 of precipitating it much more rapidly. " Keeping in view the large 

 quantities of earthy matter annually carried down by rivers, a large 

 proportion of which is precipitated as soon as it comes in contact with 

 the water of the sea, we can easily understand how the courses of 

 rivers, within the influence of the tide, diverge into various branches 

 by the precipitated mud silting up the river-bed at one place, and 

 the obstructed water forming a new channel at another; and hence 

 throwing a new light on the formation of deltas at the mouths of 

 rivers." The paper, " On the Geology of the North-Eastern District 

 of Yorkshire," by Mr. T. M. Barr, is not, as the author justly states, 

 anything like a systematic or exhaustive study of its geology, and is 

 therefore only a general account of this valuable iron-ore bearing 

 district. The "top seam," alluded to at page 298, does not belong 

 to the top of the Upper Lias series, but belongs to the " Dogger " or 

 Inferior Oolite, which is situated between the Uj)per Lias and the 

 Great Sandrock above. This seam has been worked at Grosmont, 

 and formerly in Glazedale. But it is in Eosedale, in the very 

 centre of the great moorland district, that the Dogger and its as- 

 sociated beds have yielded the greatest results to mining enterprise. 

 The celebrated Eosedale magnetic ore occurs as an enormous boss or 

 local swelling in the Sandrock below the Dogger, about 600 yards 

 long, by 160 feet wide, and 80 feet high. There is nothing like 

 it in all this district, and it may fairly be described as the richest ore 

 in North Yorkshii'e, a perfect nugget of iron-stone on a bare hill- 

 side, 700 feet above the sea.^ 



Of the district papers, Messrs. Eobertson and Crosskey continue 

 their descriptions of the Post-Tertiary beds of the West of Scotland, 

 which, when completed, will be of great value, for Mr. Eobertson's 

 intimate acquaintance with the estuarine and marine fauna of the 

 Clyde, and his extensive collections (personally acquired) of recent 

 British species, and those from the Post-Tertiary deposits, not only 

 around the Clyde, but from Sweden, Norway, etc., will enable the 

 authors to infer more clearly the conditions under which these strata 

 were deposited. 



Mr. J. Young contributes three papers : 1. "On the Probable Source 

 of Certain Boulders in the Till of the Glasgow District," in which the 

 origin of the Limestone blocks is chiefly treated. We trust this 

 author will fully describe the fine section recently exposed at the 

 extensive excavations for the Stobcross Docks, with its numerous 

 and varied boulders, which could only have been brought together 

 here from a wide extent of country lying in several different directions. 



1 The Yorkshire OoHtes. By,W. H. Huddlestone, F.G.S. Proc. Geol. Asso., 

 1874, vol. iii. p. 305. 



