September 1, 1922] 



SCIENCE 



255 



after practically twenty years of investigation, 

 reading, and correspondence the present work 

 can be considered as a summation of results. 

 It is divided into three parts, the first of which 

 sets forth the scope of the problem, while the 

 second part deals with the application of the 

 principles set forth to the facts of paleontology 

 and geology, and the third to a recapitulation 

 of conclusions and their general application. 



Dr. Manson of course recognizes that on ac- 

 count of the low conductivity of the earth's 

 crust it has been held by physicists and mathe- 

 maticians that this source was inadequate as a 

 factor of importance, but after reviewing the 

 data on which this assumption is based he 

 "feels obliged to reject 'the conclusions as 'in- 

 competent, irrelevant, and immaterial'." He 

 holds that "both earth heat and solar radia- 

 tion prevailed as active factors in temperature 

 control during all of the eras of geologic his- 

 tory and until the modern era of solar con- 

 trol; that the former was available as ocean 

 stored heat, but the supply was held in the 

 forming crust by reason of its low conductivity 

 and was slowly made available by denudation 

 and the exposures of radio-active materials, 

 etc., or by periodic changes in the topographic 

 form of the earth's surface which made in- 

 crements of the interior sources of energy 

 available." 



This earth heat warmed the early oceans, 

 the first effect being to increase evaporation 

 and cloud formation. This ocean stored heat 

 w^s conserved by the moist air and clouds and 

 in part restored by the effects of solar radia- 

 tion. This continued until the exhaustion of 

 earth heat was registered by the cold oceans 

 of Pleistocene time. 



The causes for the initiation of glaciation 

 as well as the alternation of glaciation and de- 

 glaciation or inter-glacial periods have given 

 rise to almost endless speculation. Many stu- 

 dents have stated frankly that they can see 

 no possible or reasonable explanation of, for 

 instance, the Permo-Carboniferous glaciation 

 that occurred in or adjacent to the tropics, 

 under direct solar control, and under this as- 

 sumption this is about the only conclusion 

 that oan be reached. But Dr. Manson offers 

 an explanation that is not only logical but 



seemingly possible not to say probable. He 

 says: "The two conditions essential for glacia- 

 tion are: (1) Cold Continental Areas — cold 

 from more rapid chilling when remote from 

 ocean influences, from elevation, from exposure 

 to cold anti-cyclonic winds, and, upon the final 

 loss of efficient earth heat; (2) Warm 

 Oceans, to supply water vapor in sufficient 

 amounts to deeply glaciate and to maintain 

 continuous cloudiness to intercept solar 

 energy." 



"Land areas chilled prior to the oceans and 

 were therefore exposed to glaciation. Tur- 

 thermore in cooling oceans each of these im- 

 pairments occurred at a critical temperature; 

 first that degree which could just maintain 

 cloud density in zones of minimum cloudiness; 

 and lastly, that degree which could just main- 

 tain cloudiness in zones of maximum cloud 

 density. Moreover, if, during the existence of 

 either glaciation, the oceans should fluctuate 

 in temperature to points somewhat above or 

 somewhat below these critical temperatures, 

 corresponding variations in the generation of 

 water vapor would necessarily follow, imposing 

 variations in the integrity of the cloud sphere 

 in each latitude. Each fall below this critical 

 temperature would impair the cloud sphere, 

 and each rise above this temperature would 

 restore it, thus alternately exposing the sur- 

 face to solar energy and shutting off the same 

 until the oceans again chilled below the criti- 

 cal temperature." 



This in brief outline is Manson's explana- 

 tion of the phenomena of glaciation and de- 

 glaciation. The theme is of course fully elabo- 

 rated in the paper, and whatever its fate may 

 be it is something that will have to be reckoned 

 with by all future students. All will admit 

 that any explanation that is put forward to 

 account for glaciation or deglaeiation must 

 apply equally to these phenomena wherever 

 they occur, and while many theories have been 

 proposed that may seem to cover particular 

 cases they fall short of accounting for all. Dr. 

 Manson's explanation applies as well to the 

 Huronian and Permo-Car'boniferous as to the 

 Pleistocene glaciation. It is a notable contribu- 

 tion. 



F. H. Knowlton 



