270 R. Chambers, Esq., on Glacial Phenomena 



heard, in the subjacent moraine matter. Besides these for- 

 mations, there is the still more superficial one of erratic 

 blocks, which, affiliated to Sweden and Finland, extend south- 

 ward into Denmark, Germany, and Russia, at least as far as 

 the 50th parallel. These rocks are less worn than those of 

 the lowest deposit, and yet are carried much farther. It is 

 likewise of importance to observe, that they have been car- 

 ried over the intervening line of the Valdai Hills, which 

 rise from 800 to 1100 feet above the sea. 



The superficial deposits of Northern America bear a gene- 

 ral resemblance, in their important features, to those of 

 Northern Europe. 



In our island, the superficial deposits constitute a series, 

 of which no fewer than six, if not seven, members have been 

 described by some observers, though it is seldom that so 

 many are present at one place. 



One noted deposit very generally found resting on the rocks 

 in Scotland, is the Boulder Clay (No. 1.) It consists of a 

 remarkably compact menstruum of clay, blue, black, or of 

 some lighter colour, totally impervious to water, and only 

 assailable by the pickaxe ; which breaks with irregular frac- 

 ture ; has no trace of lamination ; and through which are in- 

 terspersed blocks of all sizes, which have travelled from places 

 within forty or fifty miles, usually rounded, often worn into 

 a sort of sole on one side, presenting striae or scratches. 

 This deposit is found, in Mid-Lothian, nearly 1000 feet 

 above the sea, and, in some places, is stated to be not less 

 than 160 feet deep ; shewing an amount and extent of 

 operation for the abrading agent in which it took its rise, 

 perfectly enormous. A railway cutting made in this deposit 

 on Middleton Muir, in a situation not less than 700 feet above 

 the sea, was about fifty feet thick. 



In the valleys of the Forth and Clyde, where the boulder 

 clay is very largely developed, the included blocks are all 

 from the westward, the direction of the agent which has pro- 

 duced the furrowing and striation of the district. At several 

 places, strata cropping out westward under the clay, have been 

 found bending off back to the east, with the clay insinuated 

 in the gap, clearly proving at once an east-going force, and a 

 partially liquid state of the clay at the time of its deposition. 



