Proceedings of tJie Ohio State Acadojix of Science 31 



when he wrote: "I think I speak the growing conviction of 

 active workers in the American field, that even the ingenious 

 theory of CroU becomes increasingly unsatisfactory as the 

 phenomena are developed into fuller appreciation. I think I may 

 say this without prejudice, as one who, at a certain stage of study, 

 Avas greatly drawn towards that fascinating hypothesis." 



Within the last fifteen years a new hypothesis has been j^ro- 

 posed by ChamLerlin. This was first fully presented in 1899 in a 

 paper entitled "An Attempt to Frame a \\'orking Hypothesis of 

 the Cause of Glacial Periods on the Atmospheric Basis." This 

 "atmospheric hypothesis" of Chamberlin's is not simpler than 

 Croll's, but explanations of geological phenomena are not com- 

 monly simple. Indeed there is a certain parallelism between the 

 sticcessive steps of this theory and the sticcession of cause 

 and efifect in Darwin's famotis illustration of the way in 

 which "animals and plants, remote in the scale of nature, 

 are bound together bv a web of complex relations." You 

 will remember that with the increase of cats there went 

 a decrease of field mice ; this meant an increase of humble- 

 bees (the field-mouse's victim), and a corresponding increase of 

 clover, which is cross pollenized bv the bees. Therefore, the 

 more cats the more clover. Htixley, I believe, extended the 

 series by one term and showerl that maiden ladies, through their 

 fondness for cats, belonged in the chain. Even more complex is 

 the atmospheric hypothesis. Primarily it explains glacial climate 

 by the loss of CO^ from the atmosphere. Air containing CO., 

 has greater power of absorbing heat, the waves received from 

 the sun and especially the waves of greater length radiated from 

 the earth. Less heat is thus lost to space and the temperature 

 of the air is higher. With loss of CO., there is a smaller amount 

 of heat retained and a lowering of atmospheric temperature. This 

 in turn decreases the amount of water vapor in the air, which, 

 after CO. is the atmospheric constituent with the greatest heat- 

 absorbing power. 



The hypothesis assigns the loss of CO. to land elevation. 

 This is followed by increased weatheringr, both because of the in- 

 creased land area exposed to weathering, and because of the 



