30 James Geikie — On Changes of Climate. 



2nd. The beds of Till point to intense arctic conditions having 

 prevailed at the time of their formation. 



ord. The deposits of silt, clay, sand, and gravel, with land-plants 

 and mammalian remains, and in some places with marine shells, all 

 of which beds are intercalated in the Till, clearly show that the 

 intense arctic cold which covered the country with an ice-sheet was 

 interrupted, not once but several times, by long continuous ages of 

 milder conditions. Some of these periods may have been warmer 

 than others, just as some of the glacial periods may have been 

 colder than others. 



4th. So far as direct evidence goes, we cannot say that any one of 

 those inter-Glacial periods was characterized by a warmer climate 

 than is now enjoyed in the forest regions of high latitudes in 

 America. 



5th. Considering the sorely denuded appearance of the inter- Glacial 

 deposits, and keeping in mind the nature of the conditions under 

 which they have been preserved, it would be rash to conclude that 

 they contain a complete record of the changes which ensued during 

 inter- Glacial times, or that we are entitled to argue from the few 

 fossils yielded by them that the climates of the inter-Glacial periods 

 were never positively warm. 



6th. A mild or temperate period followed upon the final dis- 

 appearance of the great ice-sheets. There is no reason to suppose 

 that this change of climate was caused by the sinking down of the 

 land and the incoming of the sea. The probabilities are that the 

 glaciers had retired a long way from the sea before subsidence 

 commenced, and had left the ground covered here and there with 

 heaps of loose terminal moraine rubbish. 



7th. During the process of subsidence tliat ensued the Kame- 

 series of sand and gravel was formed. Little or no floating-ice 

 existed in our seas at this time. 



8th. When the subsidence had become considerable the glaciers 

 again entered the sea, and bergs and coast-ice scattered stones and 

 blocks across the sea-bottom. These blocks and stones strew the 

 tops and slopes of the Kames and occur in the shelly clays. 



9th. The clays with arctic shells belong to the period of re- 

 elevation. 



10th. The subsequent changes indicate a gradual amelioration 

 of climate down to the present. 



Such are the general results which appear to be fairly deducible 

 from what is known of the Scottish Drift. It is so easy to coi-relate 

 the various Glacial deposits in Scotland, and to read off the suc- 

 cession of events, that it becomes interesting to inquire to what 

 extent the sequence obtained in other northern regions harmonizes 

 with the conclusions stated above. For if it be found that not only 

 in Northern Europe and North America, but in Switzerland also, the 

 order of succession of the drift dejoosits tallies precisely, this will 

 doubtless serve as a guide towards unravelling the more complicated 

 drifts of the low grounds of England. My limits, however, will not 

 allow me to do more than bring together into as short a space as I 



