S'O PROCEEDINGS OF THE AXX ARBOR MEETING 



at various times, as in the case of supposed continental masses lilie Gondwana- 

 laud, Atlantis, and the intercontinental land-bridges of biogeographers. con- 

 sideration quantitatively of total land and sea areas is important. Unless 

 wholly unwarranted assumptions as to change in the volume of the seas are 

 made, the depth of oceanic depressions must, in a measure, be related to total 

 marine area. Some published paleogeographic maps indicate world seas so 

 reduced that if the waters were actually restricted to areas designated, the 

 containing depressions would have to be excessively deep. 



Presented in abstract from notes. 



Discussion 



Prof. C. Schuciiert: I am pleased to see Professor Moore trying to get at 

 the quantitative vulues of the marine transgressions. It is a most difficult 

 problem, and all the more so w^hen a good geologist makes of the entire Pacific 

 basin a continent in order to explain more easily the existence of his circum- 

 ferential geosynclines. That the present continents were larger in geologic 

 time than they are now most geologists admit, but how far they extended be- 

 yond the present shorelines is a vexed question. Since the ocean l)ottoms 

 move as \vell as the continents, great areas of the latter have been fractured 

 into the oceanic deeps, and active volcanoes and thermal springs are con- 

 stantly increasing the volume of water, while great quantities of it are being 

 taken up by the lithosphere. These factors make the problem of quantitative 

 oceanic oscillations almost unsolvable. Nevertheless, the problem must be 

 kept in mind, and, as well, that of the theoretic placement of continents where 

 now are oceanic deeps. 



Further remarks were made by Mr. Higgins, with reply by the author. 



KEWEEXAW GEOTHERMAL GBADIEXT8 AXD THE ICE AGE 

 BY ALFRED C. LAXE 



{ Abstract) 



The rate of increase of temperature in the deep copper mines averages about 

 1 degree Fahrenheit in 105 feet, but is greater in depth, about 1 degree Fahren- 

 heit in 90 feet. While the mean air temperature in Calumet is 39.4 degrees, 

 the mean ground temperature is over 43 degrees, owing to the blanketing effect 

 of snow. The change in gradient is due to a rise in surface temperature from 

 freezing (32 degrees) to 43 degrees about 11.000 years ago. 



The deeper gradient is only what might be expected with rocks of this dif- 

 fusivity, low in pyrite, with no signs of recent exothermal reactions, low in 

 radioactivity. 



Exhaustion of heat from below in early times and an exceptionally thick 

 crust, as indicated by isostatic observations, are also to be taken into account. 



Presented in abstract from notes. 



Brief remarks were made by Messrs. Daly and Van Xostrand, with 

 reply l)y the author. 



