SOLUTION OF THE CLIMATE PROBLEM RAMSAY 241 



miothermic or less warm.* This term may also be used to designate 

 the less-warm climate and the corresponding deposits. In most 

 geological systems, however, we do not find any traces of glacial 

 formations, or other phenomena evidencing a cold climate. There 

 is rather every indication of favorable conditions for animals and 

 plants over all the earth. For the corresponding periods and con- 

 ditions, I have proposed the name pliothermic or more warm. We 

 are now living in a miothermic period. It includes not only the 

 Quaternary ice age, but also the interglacial and postglacial ages. 

 For during them all, ice caps and glaciers existed. An ice age 

 signifies aggravated miothermic conditions. 



Wliich periods were miothermic, which pliothermic ? 



Traces of glaciation in the shape of tillite are found in pre- 

 Cambrian formations. We know them, further, from the base of 

 the Paleozoic series, and in the Eodevonian, Permian, perhaps in 

 the oldest Cretaceous, and finally the Quaternary. They are formed 

 in periods immediately after the great orogenic events, when the 

 relief was orocratic. All other periods are pliothermic, and the 

 obvious warmest coincide with the phases of least disturbance of the 

 earth's crust and the greatest general transgressions, when the con- 

 tinents had the most pediocratic relief. Between orogeny and 

 climate, there is an evident connection which I pointed out some 

 years ago (1910). ("Orogenesis und Klima " cited above.) 



Dacque, who has elaborated this theme in still greater detail, has 

 in his instructive treatise on paleogeography ^ illustrated graphically 

 the changes of climate from the Cambrian time to the present day 

 and the intensity of the orogenesy during the same space of time. 

 Those interested will see in the diagrams in the work cited (pp. 

 432 and 449) a striking parallelism between these two curves. 



How may the apparent relation between the formation of moun- 

 tains and the deterioration of climate be interpreted ? 



It is hardly possible to explain it by astronomical theories con- 

 cerning the ice ages, unless, one supposes that the plication of moun- 

 tain chains depends upon those astronomic constellations which have 

 been thought to cause decline of heat on the earth's surface. 



The hypotheses which find the cause of the ice ages in a protracted 

 decrease of radiation from the sun, help us no more, for it is not 

 probable that orogeny on the earth is produced by such a change 

 in the sun. 



It thus remains to look for the answer to the above question in cir- 

 cumstances connected with orogeny which have the effect that the 



* Wilhelm Ramsay, " Orogenesis und Klima " ; Ofversigt of Finska Vetenskaps-Socie- 

 tetens FOrhandlingar, Helsingfors, lii, 1910, Afd. A, No. 11. 



* Edgar Dacqu4, Grundlagen und Methoden der PalSogeographie, Jena, 1916. 



