572 



SCIENCE 



[Vol. LVI, No. 1455 



screen glaeiations frequently occurred non- 

 conformable to solar control; all of which, ex- 

 cept the last, merged into a non-zonal distribu- 

 tion of milder climates; while the last merged 

 into the zonally distributed climates of to-day 

 distinctly under solar control. 



A uniform and steady supply of heat from 

 the earth's interior under the assumed screen 

 of clouds is not held in the theory which Pro- 

 fessor Coleman criticises. On the contrary, it 

 is held that this suj)ply was neither, uniform 

 nor steady, but highly variable in both supply 

 and exliaustion. 



The periods of glaeiation as compiled by 

 Professor Schuchert^ are accepted as marking 

 variation of climate of greater or less extent 

 and severity in various localities and zones 

 throughout known geologic time. None of 

 these can be reconciled with a mild and equable 

 climate controlled by any source or sources of 

 heat and particularly not to a climate con- 

 trolled by solar energy; for no glaeiation has 

 been recorded conformably to solar control. 

 All were non-conformable thereto and contra- 

 dictory thereof, but they can be reconciled with 

 periods during which the available increments 

 of the internal heat were exhausted to such an 

 extent that land masses in various latitudes 

 cooled below 31° P. The glaeiation of tropical 

 latitudes during Permo-Carboniferous time is 

 particularly fatal to any assumption of solar 

 control; for had this, or any other glaeiation, 

 been imposed under solar control it would 

 have commenced in polar latitudes and ad- 

 vanced equatorward, and would have retreated 

 poleward. No glaeiation has been so laid down 

 and none except the Pleistocene has so receded 

 and given place to a disposition of climates 

 distinctly zonal and as distinctly under solar 

 control; and the fluctuating advances and re- 

 treats were at such short intervals that corre- 

 sponding fluctuations in solar energy could not 

 be reasonably assumed. 



The mantle of clouds need be neither sup- 

 posed nor assumed. It recorded its effects in 

 glaeiations and reglaciations in nearly a score 

 of instances, and it recorded its failures in each 

 interglacial epoch and in the present progres- 

 sive deglaciations. By no other known means 



S Smithsonian Inst. Report, 1914, 305-306. 



could solar energy have been intercepted to 

 such an extent as to permit frequent glaeia- 

 tions of portions of the earth in latitudes which 

 could not have been sufficiently chilled without 

 such interception. 



The writer accepts the variability of climates 

 on continental areas from the dawn to the close 

 of geologic time, as presented by Professor 

 Schuchert [Smithsonian Inst. Report, 1914, p. 

 305]. This variability is well estahlished.* 



It is also well established in Permo-Carbon- 

 iferous^ and Pleistocene glaeiations that max- 

 ima were attained along quite well-defined zonal 

 lines. 



Continental temperatures in tropical and in 

 polar regions now vary within the limits of 

 110° F. and —60° F., or a range of 170° F. ; 

 and ocean temperatures range between 85° and 

 31° F. or through 54° F. It is a reasonable 

 inference that during geologic climates con- 

 tinental temperatures had approximately the 

 same extreme range, but the range of ocean 

 temperatures for the greater part of geologic 

 time, as admitted by Professor Schuchert, was 

 between 85° F. and 55° F., or through 30° F. 

 But it manifestly took from Proterozoic until 

 Pliocene for oceans to pass through these ex- 

 tremes and only in the Pleistocene did oceans of 

 polar and middle latitudes reach the present 

 lower limit, with their extreme range of 54° F. 

 The present extreme range of continental tem- 

 peratures between tropical and polar latitudes 

 of 170° F. is the same as the annual range in 

 central Canada and Siberia, and the annual 

 range of ocean temperatures in the same lati- 

 tude is less than one tenth (^o) of this. 



The comparison of the range of ocean tem- 

 peratures prior to the Pliocene of 30° F. with 

 the present range of 54°, and the ease with 

 which continental temperatures can range with- 

 in twelve months through 170° F. supports the 

 writer's views regarding geologic climates. 



The prime and radical difference between 

 the conclusions of Professor Schuchert and 

 those of the writer are, as to the source of con- 

 trol, namely, that until oceans chilled to the 

 temperatures marked in Pleistocene time, a 

 dual source of climatic control prevailed, and 



4 0sboni, "The Age of Mammals," pp. 372-3. 

 B Schuchert, ib., 280-282. 



