MICHIGAN ACADEMY OF SCIEN'CE. 99 



So fundamental a theory as that of Laplace to explain the origin of 

 the univeivse, a theory which has been standard doctrine for more than 

 a century and is only now being replaced as a result of rigidly applied 

 tests, appears never to have been very seriously considered by its author, 

 but was thrown off as a brief appendix or postscript to a general work 

 on astronomy. It has the curious title "Note VII and Last" and Laplace 

 says of it tliat the hy]iothesis must be received "with the distrust with 

 which everything should be regarded that is not the result of observation 

 or calculation. " Moreover, so far as known. Laplf^ee never subjected 

 tiie theory to the test of well-known mathematical principles which were 

 involved, although this was his usual habit. The success and general 

 acceptance of the theory seem to have been due to the altogether remark- 

 able prestige of its author as the greatest mathematician since Newton, 

 and as the author of the "M^canique Celeste," a work which has never 

 been rivaled in its field, and of which it has been said that any one of 

 its twenty-four parts would have made the reputation of a man of science. 



Though primarily' a theory of the origin of the universe and thus in 

 tlie realm of astronomy, Laplace's nebular hypothesis left its impress 

 upon geology and particularly upon geophysics, in that it gave continued 

 standing and scientific respectability to the notion that the earth has a 

 liquid interior. It would be somewhat difficult to trace the origin of 

 this belief, whicli naturally grew up from the observations of volcanic 

 eruptions — no uncommon event in the Grecian Archipelago and in Italy, 

 the regions where science had its beginnings. After the studies of com- 

 bustion had exploded the notion of "internal fires," the theory took the 

 form which it has retained to our day little affected at first by the 

 jiroofs of earth rigidity which were brought forward by Kelvin. With 

 little doubt the associated idea of a congealed crust floating upon a 

 licjuid interior is based upon the analogy with the winter cover of ice 

 which forms over our lakes and rivers. This analogy supplies, there- 

 fore, a striking instance of the influence of climate in giving complexion 

 to a fundamental theory, and the fact that rock, unlike water, is heavier 

 in the solid than in the liquid state, is a very recent discovery. Save 

 for its intimate relation to Laplace's theory, the conception of the liquid 

 core to the earth must have long since been relegated to tlie limbo of 

 exploded doctrines^, to the great benefit of more than one of the physical 

 sciences. 



It would be easy to show that well-known scientific theories have 

 embodied fatal defects, in that assumptions of vital importance have 

 been introduced quite unconsciously by their authors. I have believed, 

 and have elsewhere attempted to show, that the Pratt-Hayford theory 

 of isostatic compensation, which assumes for every mountain a necessary 

 defect of mass directly below, and for the column below every depression 



