MR DAVID MILNE PIOME ON THE BOULDER-CLAY OF EUROPE. 661 



Arguing from this test, the late Dr Fleming showed very clearly that in the 

 neighbourhood of Edinburgh, the boulder-clay " had been in motion from west 

 to east."* 



These views are important, as proving also that geologists agree in holding 

 that whatever may be the case with regard to the erratic blocks in the boulder- 

 clay, the boulder-clay itself has been derived chiefly from the rocks over or near 

 which it lies, and (to use Mr Geikie's expression) " consists of the comminuted 

 debris of" these rocks. 



(2.) Another well-established indication of the direction in which the boulder- 

 clay has moved, is afforded by the striations and groovings of the rocks covered 

 by the deposit. Mr Jameson, after stating various facts bearing on this point, 

 says, " all this shows that the boulder earth, with its embedded fragments, was 

 pushed along by the same agent that scored the rocky bed on which it lies."t 

 So also Mr Gteikie, after mentioning other examples, says — " Here it will be seen 

 that the direction of transport of the boulder-clay exactly coincides with the 

 trend of the groovings and striations on the rocks below," \ 



(3.) Farther evidence bearing on the same point is afforded by the nature of 

 the boulders or erratics embedded in the boulder-clay ; for when an examination 

 of the rocks composing them has led to a discovery of the locality from which 

 they have apparently been transported, the direction in. most cases coincides 

 with that of the striations on the rocks, and with the direction of the movement 

 of the boulder-clay as indicated by its colour. Accordingly, Agassiz does not 

 hesitate to admit, that the striae on the rocks are due to the same cause which 

 transported the blocks. § 



This remark applies not merely to blocks in the boulder-clay, but to erratic or 

 transported blocks in other positions, whether on rocky knolls or on beds of gravel. 

 Whenever the quarter from which they have come has been clearly ascertained, it 

 is found that the direction of their transport agrees with that of striae on rocks 

 in the neighbourhood. 



There is another circumstance, not undeserving of consideration, long familiar 

 to geologists, viz., that when erratics are of such a shape that their length greatly 

 exceeds their width, their longer axis generally lies in the direction of their 

 transport. 



I believe, therefore, in common with other geologists, that the movement of 

 the boulder-clay, whenever that has been ascertained, the transport of boulders, 

 and the striations, groovings, and smoothings of the rocks, are due to one and the 

 same agent; and hence the phenomena to which reference has just been made, 



* Lithology of Edinburgh. 



f Lond. Geolog. Journal for 1866, p. 167. 



% Glacial Drift, p. 45. 



§ Edin. Phil. Journ. for 1842, vol. xxxiii. p. 223. 



