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SCIENCE 



[N. S. Vol. XXVIII. No. 716 



tlie sun and the temperature of space) ; so 

 long as this can not be done, ' most modern 

 theories ' of geological climate must certainly 

 be regarded as ' upset,' for these theories are 

 hosed upon an adopted value for the tempera- 

 ture of space which is (according to my 

 [Schaeberle's] demonstration) too great iy 

 nearly three hundred degrees of the centi- 

 grade scale at the earth's distance from the 

 sun, etc." (italics original). 



Statements as sweeping as these in the 

 columns of Science, as pointed out by Lane 

 in answer to an earlier communication, ap- 

 pear to call for some comment for the bene- 

 fit of those of your readers who are neither 

 geologists nor astronomers. In answer it 

 may be stated that an inspection of recent 

 geological literature in the special mediums 

 of geological publication shows that all 

 articles dealing with actual details of 

 geological climates are based not upon con- 

 siderations of the temperature of space, but 

 upon detailed studies of the geological record. 

 It is the effort of modem theory upon an- 

 cient climates to meet this evidence and the 

 lines of theory are determined by the definite- 

 ness and complexity of the facts to be ex- 

 plained rather than by any assumption in re- 

 gard to the temperature of space. 



A generation ago, when but little was defi- 

 nitely known in regard to geologic climates, 

 theoretical calculations as to what condi- 

 tions could, should, or would have prevailed 

 at the base of the atmosphere, would have 

 had some weight. At present a study of the 

 stratigraphie record to find what actually 

 were the conditions is much more definite 

 and profitable. The results of such study 

 have been to show an oscillation of wide- 

 spread climatic conditions from glacial to 

 torrid and from humid to semi-arid, or arid, 

 reaching back to the very beginning of the 

 sedimentary rocks; extreme oscillations of 

 shorter period being superimposed upon 

 others of more general character and ffion- 

 long in their duration. At times climates 

 appear to have been widely uniform, a fea- 

 ture whose explanation has been sought in 

 hypotheses of changes in character of lands, 



m ocean currents, m atmospheric composi- 

 tion, or in solar diameter. But at other 

 times, as in the Permian, climates seem to 

 have been distinctly local, though the geo- 

 logic, or time, contrasts in climates have 

 been in general more striking than the geo- 

 graphic, or space, variations. Perhaps the 

 heaviest blow which has been struck recently 

 at the older hypothesis of a simple climatic 

 evolution from a primitive, uniform, torrid 

 condition is found in the work of Coleman, 

 who has presented the evidence of a glacial 

 period practically at the beginning of the 

 sedimentary record in North America. The 

 advance of knowledge in regard to geological 

 climates, as in so many other fields, has been 

 away from simplicity toward complexity. 



In view of these conclusions by weU-quali- 

 fied geologists Hansen's hypothesis of an earth 

 self -heated and protected by a cloud envelope 

 until the Tertiary, which Schaeberle consid- 

 ers that he has demonstrated as a true theory, 

 and which has recently been picturesquely 

 written up by Percival Lowell for the Cen- 

 tury magazine as the assured dictum of geol- 

 ogy, must be regarded as in no measure ade- 

 quate to explain the facts. If that hypothesis 

 is not to be relegated to the scientific scrap 

 heap it must either be very greatly modified 

 or its supporters must break down the con- 

 clusions in regard to geologic climates which 

 have made it unavailable as an explanation. 

 Until this is done it must be regarded as an 

 unsupported speculation. 



It would also add definiteness to that hy- 

 pothesis if its advocates would make it quanti- 

 tative by stating the amount of thermal 

 energy now actually delivered by the earth's 

 interior to its surface in unit time, basing 

 this calculation upon the thermal conductiv- 

 ity of rock and the temperature gradient. 

 For applying the hypothesis to past times the 

 favorable sub-hypothesis should be postulated 

 of assuming that the earth is simply a cool- 

 ing body unwarmed by radio-active or other 

 internal activities, since this permits a more 

 rapid delivery of heat in the past. For the 

 purposes of such a calculation also, the sur- 

 face may be assumed to have remained of 



