2 62 CARNEGIE INSTITUTION 



moment that had been written on the origin of the solar system. 

 This had not advanced far before the conviction arose that the prep- 

 aration of an analytical review of the whole literature of the subject 

 would save other investigators the very considerable labor of repeat- 

 ing the task undertaken by Dr. Moulton and would in other respects 

 be a valuable contribution to investigation. In pursuance of this 

 the literature, which is quite voluminous, has all been read with 

 extensive annotations, and the preparation of the review is now in 

 progress and will be submitted as soon as finished. Subsidiary to 

 this, Dr. Moulton has aided in the informal discussion of other sub- 

 jects under investigation. 



As the origin and distribution of the earth's internal heat is fun- 

 damental to many of the most important problems of geology, a 

 large part of our joint studies has been given to the continuation of 

 previous studies bearing on this subject ; but, as all fundamental 

 questions react the one upon the other, we have endeavored by the 

 scheme of collaboration adopted to advance coordinately several 

 lines that seemed most promising of mutual helpfulness. 



An analysis of the work heretofore done on the origin and distri- 

 bution of internal heat and of its sequences reveals the fact that 

 inquiry has largely been guided by the older and the least probable 

 of the three hypotheses of the origin and initial distribution of heat 

 that are now recognized. Under the long dominant view that the 

 earth descended from a gaseous spheroid throngh the molten state 

 to its present condition, there naturally arose the conception that 

 during the liquid state convections stirred the molten mass from 

 center to circumference and measurably equalized the temperature, 

 so that the whole was cooled down equably until it approached the 

 temperature of solidification and became too viscous for further 

 effective convection. As the effects of internal pressure on the tem- 

 perature of solidification were unknown in the earlier days, and 

 largely remain so still, a tmiform internal temperature, not far from 

 the melting temperature at the surface, was postulated. The deduc- 

 tions of lyord Kelvin, which have exercised great influence on geolog- 

 ical opinion for the past half century, are based on the assumption of 

 a uniform initial temperature of 7,000° F. throughout the interior, 

 and similar assumptions of practical uniformity, with unimportant 

 numerical variations, have been made by other able investigators. 

 Computations on this basis, with reasonable assumptions relative to 

 the subsidiary factors, lead to the conclusion that effective cooling 

 could scarcely exceed a depth of 200 miles in a period of 100,000,000 



