242 The Scottish Naturalist. 



and the Cheshire plain, &c, and they have been followed 

 south-east as far as the neighbourhood of Cardington near 

 Church Stretton, Burton, Wolverhampton, Stafford, Hare Castle, 

 Macclesfield, and Manchester. This great stream of boulders, 

 therefore, spreads out to south-east, south, and south-west : the 

 erratics, to quote Mr Mackintosh, " have radiated from an area 

 much smaller than their terminal breadth." The same is the 

 case, I may remark in passing, with erratics in the boulder-clays 

 of Scotland, Scandinavia, North Germany, &c, as also with 

 those in the drift-deposits of the great Rhone glacier and other 

 ancient glaciers both on the north and south side of the Alps. 

 Now the course followed by the Criffel erratics is crossed at an 

 acute angle by that pursued by many boulders of Eskdale 

 granite, and various felspathic rocks derived from the Cumber- 

 land mountains. For example, Cumberland erratics of the kinds 

 mentioned occur near St Asaph, and Moel-y-Tryfane, and in 

 Anglesey, and they have been followed over a wide district in 

 Cheshire, &c, extending as far south as Church Stretton and 

 Wolverhampton, and as far east as Rochdale. More than this, 

 we find that numerous erratics of felstone, derived from the 

 mountain of Great Arenig in North Wales, have gone to north- 

 east as far as Halkin Mountain in Flintshire, Eryrys near 

 Llanarmon, and Chirk, from which last-named place they have 

 been traced in a south-easterly direction to Birmingham, Broms- 

 grove, &c. A glance at a map of England will show that this 

 south-easterly drift of erratics crosses at an acute angle the paths 

 followed by the Criffel granite boulders and the erratics derived 

 from Cumberland, so that we have now several " intercrossings " 

 to account for. How can this be done by the land-ice theory ? 

 The explanation seems to me obvious, for the phenomena 

 are, after all, less striking than similar appearances which have 

 been observed in Scotland, especially by my colleagues, Messrs 

 Peach and Home, in Caithness and the Orkney and Shetland 

 Islands ; and they are certainly less intricate than the facts re- 

 corded by MM. Falsan and Chantre concerning the intercross- 

 ing, interosculation, and direct opposition of erratic paths in 

 Savoy and Dauphine. We have only to reflect that the great 

 mer de glace — to which, as I believe, all the English phenomena 

 are due — did not come into existence and attain its maximum 

 dimensions in the twinkling of an eye, nor could it afterwards 

 have disappeared in the same sudden manner. On the contrary ? 

 a period of local glaciation must have preceded the appearance 



