The Scoiiish Naturalist. 201 



and large snow-fields existed in our mountain districts, giving rise 

 to local glaciers, some of which were of no mean size, but seem to 

 have come down to the level of the sea at the heads of certain 

 Highland sea-lochs. Now and again one may notice how those 

 latest local glaciers have partially overridden the heaps of debris 

 which had gathered in the valleys after the disappearance of the 

 glaciers of the last cold stage of the true glacial period, while in 

 other cases they have even been deflected by masses of rock 

 which, falling in late glacial and early post-glacial times, had 

 choked up the paths followed by the ice in the earlier periods. 

 The rivers from the higher mountain valleys carried seaward 

 much of the fine " flour of rocks " produced by the grinding of 

 local glaciers ; the Greenland whale frequented our friths, and 

 was harpooned by the rude Neolithic inhabitants, whose canoes 

 have been met with again and again in the estuarine flats and 

 raised beaches of Scotland. 



The later geographical and climatic changes, so far as the 

 geologist can trace them, were simply these : ist, the retreat of 

 the sea to its present level ; and, 2d, a diminished rainfall, the 

 final disappearance of snowfields and glaciers, and a gradual 

 amelioration of climate. That our climate, in times subsequent 

 to the melting of the local glaciers, may have experienced minor 

 fluctuations, is possible enough; and perhaps evidence of these 

 may yet be forthcoming, when the botanical features of the peat- 

 mosses are subjected to a more rigorous scrutiny than they have 

 yet received. Meanwhile, I cannot help thinking that a closer 

 examination of the geographical distribution of our present fauna 

 and flora may yet throw much light upon the problem of post- 

 glacial climate. The admirable researches of Mr Axel Blytt in 

 Norway, and of Dr Buchanan White in this country, have shown 

 how much yet remains to be done in the study of geographical 

 botany and zoology, and what a promising harvest of discovery 

 awaits the labours of the philosophical naturalist in this field of 

 inquiry. 



Such is a very brief and meagre outline of what appear to 

 have been the principal geographical and climatic mutations of 

 post-glacial times. Many interesting points I have been com- 

 pelled to leave untouched ; but I have entered fully into the 

 whole question in a forthcoming work, which treats specially of 

 the physical changes which have taken place in pre-historic ages. 

 Before concluding this short outline sketch, I may refer to the 

 striking support which the evidence lends to Dr Croll's theory. 



