in the Air upon the Temperature of the Ground. 26? 



Thus if the quantity of carbonic acid increases in geometric 

 progression, the augmentation of the temperature will increase 

 nearly in arithmetic progression. This rule — which naturally 

 holds good only in the part investigated — will be useful for the 

 following summary estimations. 



5. Geological Consequences. 



I should certainly not have undertaken these tedious calcu- 

 lations if an extraordinary interest had not been connected 

 with them. In the Physical Society of Stockholm there have 

 been occasionally very lively discussions on the probable 

 causes of the Ice Age ; and these discussions have, in my 

 opinion, led to the conclusion that there exists as yet no satisfac- 

 tory hypothesis that could explain how the climatic conditions 

 for an ice age could be realized in so short a time as that which 

 has elapsed from the days of the glacial epoch. The common 

 view hitherto has been that the earth has cooled in the lapse of 

 time; and if one did not know that the reverse has been the 

 case, one would certainly assert that this cooling must go on 

 continuously. Conversations with my friend and colleague 

 Professor Hogbom, together with the discussions above 

 referred to, led me to make a preliminary estimate of the 

 probable effect of a variation of the atmospheric carbonic 

 acid on the temperature of the earth. As this estimation led 

 to the belief that one might in this way probably find an 

 explanation for temperature variations of 5°-10° C, I worked 

 out the calculation more in detail, and lay it now before the 

 public and the critics. 



From geological researches the fact is well established 

 that in Tertiary times there existed a vegetation and an 

 animal life in the temperate and arctic zones that must have 

 been conditioned by a much higher temperature than the 

 present in the same regions *. The temperature in the arctic 

 zones appears to have exceeded the present temperature 

 by about 8 or 9 degrees. To this genial time the ice age 

 succeeded, and this was one or more times interrupted by 

 interglacial periods with a climate of about the same character 

 as the present, sometimes even milder. When the ice age 

 had its greatest extent, the countries that now enjoy the 

 highest civilization were covered with ice. This was the 

 case with Ireland, Britain (except a small part in the south), 

 Holland, Denmark, Sweden and Norway, Russia (to Kiev, 



* For details cf. Neumayr, Erdgeschiohte, Bd. 2, Leipzig, 1887 ; and 

 Geikie, ' The Great Ice-Age,' 3rd ed. London, 1894 ; Nathorst, Jordens 

 historia, p. 989, Stockholm, 1894. 



