Ancient Moraines in Argi/leshire. 199 



of the same description with that by which the movement of gla- 

 ciers over rocks in situ is established. In August 1850, when 

 Mons. Charles Martin and myself were in the west of Scot- 

 land, we visited Mr Smith of Jordanhill, then residing at He- 

 lensburgh ; and that gentleman kindly showed us how and 

 whence he had obtained many of the arctic shells, which have 

 furnished, in his hands, so important a link in the chain of evi- 

 dence proving the existence of a glacial climate in Scotland at 

 the period of the boulder clay. He pointed out to us at the 

 same time, on the beach at Row, a number of blocks embedded 

 in the clay, with their upper surfaces striated ; and called at- 

 tention to the fact, that though these blocks were scattered 

 irregularly over a considerable area, the striae on all of them 

 were parallel, or pointed in one direction, that is, N.N.W. 

 and S.S.E. From this he inferred that they had been striated 

 in the exact position which they now occupy, and have re- 

 mained unmoved since the ice passed over them. In my 

 " Geology of Fife and the Lothians," published in 1839, 1 ex- 

 pressed a similar opinion (page 213) as to the striated blocks 

 embedded in the boulder clay near Edinburgh. The evidence, 

 however, was not unequivocal, and I was led to doubt its sound- 

 ness on reading Agassiz's Etudes sur les Glaciers, published 

 in 1840, and felt then inclined to believe that the strise were 

 better accounted for by assuming that the blocks had been em- 

 bedded in the bottom of a glacier ; that during the downward 

 motion of the icy mass, they had been striated themselves 

 while cutting striae on the rock below (a reciprocal action 

 easily understood) ; and that they had been afterwards mingled 

 with the boulder clay, when that deposit was formed (as then 

 supposed) out of the wrecks of the moraines, by the fusion of 

 the ice, or an irruption of the ocean. A month or two after- 

 wards, I had an opportunity of testing Mr Smith's conclusions 

 in the neighbouring locality of Gareloch, where rocks striated 

 in situ are so abundant, and I found them fully confirmed. 

 There were striated blocks there lying loose on the surface, 

 from which nothing could be inferred ; but every striated block 

 embedded in the clay on the beach was striated in one invaria- 

 ble direction, which was precisely that of the valley, namely, 

 N.N.W. and S.S.E. They were not numerous (I counted 



