192 SEE— TEMPERATURE, SECULAR COOLING [April 20 



In 1827 Fourier submitted to the Academy of Sciences an addi- 

 tional memoir on the " Temperatures of the Terrestrial Globe and 

 of the Planetary Spaces " (cf. " Oeuvres de Fourier," Tome 11. , p. 

 97). He justly remarks that the question of terrestrial temperature 

 is one of the most important and one of the most difficult in the 

 whole range of natural philosophy. This view is still held by 

 physicists to-day, and therefore any inquiry which will materially 

 advance our knowledge of the subject may be welcome to the inves- 

 tigator of the physical problems of our globe. Some of the results 

 here obtained are only approximate ; yet they appear to fix fairly 

 accurate limits to the effects which may be ascribed to the movement 

 of heat within the earth, and accordingly may not be wholly without 

 interest to those who are occupied with this difficult subject. 



The theory that our earth is undergoing secular cooling, and 

 therefore contracting, is widely spread in the literature of contem- 

 porary science; in fact it is made the basis of nearly all current 

 speculations in geology, geophysics, seismology and the related 

 branches of natural philosophy. A theory so widely spread in mod- 

 ern thought and so long current would naturally have great pre- 

 sumptive evidence of truth, and therefore should not be lightly set 

 aside. Yet it often happens that later researches supply criteria 

 which were not available to the earlier investigators ; and subsequent 

 workers are required to take account of these advances. This 

 appears to be the situation at the present time in respect to the doc- 

 trine of the secular cooling and contraction of the earth, which is 

 currently adopted in so many of the physical sciences. 



If it may be shown, when we determine the density, pressure 

 and most probable distribution of temperature within the earth, that 

 no circulation of convection currents has taken place since the globe 

 attained approximately its present dimensions, that the effect of 

 secular cooling is therefore sensible only in the crust, and that no 

 deep-seated contraction has occurred since the earliest geological 

 time, we shall be obliged to conclude that other causes should be 

 found which are adequate to account for the phenomena heretofore 

 explained by the effects of secular cooling. In particular it becom.es 

 advisable to subject the doctrine of contraction to a most searching 

 examination and crucial test, in order to ascertain what justification 



