MR DAVID MILNE HOME ON THE BOULDER-CLAY OF EUROPE. 683 



rocks in the Western Hebrides and the north of Ireland, which are certainly more 

 recent than the chalk, and perhaps belong to the glacial period. On the shores 

 of the Baltic, it has been made out that during this period there were great 

 fractures in the earth's crust. 



Whilst there are geological reasons for assuming the existence of high land in 

 the North Atlantic Ocean, now submerged, there are physiological reasons in 

 favour both of high land and of a great Arctic current from the north-west. It 

 was the late Professor Edward Forbes who first drew prominent attention to 

 the light thrown on the past history of the earth, by reference to the migrations 

 of the fauna and flora of a country. His remarks, as applicable to Great 

 Britain, are these—" There could not always have been such a separating abyss 

 between Northern Europe and Boreal America as now divides them. The sea, 

 through a great part, must have been a shallow sea; and somewhere, probably 

 far to the north, there must have been either a connection, or such a proximity, 

 of land as would account for the transmission of a non-migratory terrestrial * 

 and a littoral marine fauna." f 



In another passage he says — " It is strongly impressed on my mind that the 

 close of the glacial period was marked by the gradual submergence of some great 

 northern land, along the coasts of which the littoral mollusks, aided by favouring 

 currents, migrated ; whilst a common flora \ became diffused over its hills and 

 plains. Although I have made icebergs and icefloes the chief agents in the trans- 

 portation of flora southwards, I cannot but think that so complete a transmission 

 of that flora as we find on the Scottish mountains, was aided perhaps mainly by 

 land to the north now submerged." (" Memoirs of the Geological Survey of 

 Great Britain," vol. i.) 



10. In considering the claims of the two theories which have been proposed for 

 explaining the boulder-clay deposit and other drift phenomena, it is proper to 

 keep in view, that whilst there are many of these phenomena which are sus- 

 ceptible of explanation on either theory, there are others again which, whilst 



* Allusion is probably here made to the remains of the woolly-haired elephant, rhinoceros, 

 musk ox, rein-deer, black bear, and polar bear having been found in pleistocene beds in various parts 

 of Great Britain. If, as is believed, these animals belong naturally to North America, how did they 

 reach the small island of Britain ? 



f In a list of sea-shells given by Mr Jameson of Ellon, as found in the boulder-clay and other 

 pleistocene beds of Scotland, amounting altogether to 137, he represents 134 as now living in the 

 Arctic circle, 60 in North-Eastern America, 26 in the North Pacific, and 82 in British seas. The 

 number now living in the Arctic circle, North-Eastern America, and North Pacific, but not in British 

 seas, is 52. 



X Professor E. Forbes mentions, in illustration of this point, the Eriocaulon septan gul are, 

 " known in Europe only in the Hebrides, and at Cormemara, in the west of Ireland. Elsewhere," he 

 says, " it is an inhabitant of Boi'eal America, which is its true native country, and from whence, by 

 means of transport, it has in all probability been introduced naturally into the British Isles." Pro- 

 fessor Balfour has given to me the names of the following additional plants, natives of Labrador 

 and Canada, which are found in Skye and on the west coast of Ireland, but nowhere else in Europe, 

 viz., Neottia gemmipara and Sisyrinchium anceps. 



VOL. XXV. PART II. 8 P 



