354 R. S. Woodward — Mathematical Theories of the Earth. 



a single suggestion, which will perhaps help us to orient our- 

 selves aright in our various fields of research. If the curve of 

 scientific progress in any domain of thought could be drawn, 

 there is every reason to believe that it would exhibit consider- 

 able irregularities. There would be marked maxima and 

 minima in its general tendency toward the limit of perfect 

 knowledge ; and it seems not improbable that the curve would 

 show throughout some portions of its length a more or less 

 definitely periodic succession of maxima and minima. Races 

 and communities as well as individuals, the armies in pursuit 

 of truth as well as those in pursuit of plunder, have their 

 periods of culminating activity and their periods of placid 

 repose. It is a curious fact that the history of the mathemat- 

 ical theories of the earth presents some such periodicity. We 

 have the marked maximum of the epoch of Newton near the 

 end of the 17th century, with the equally marked maximum 

 of the epoch of Laplace near the end of the 18th century; 

 and, judging from the recent revival of geodesy and astronomy 

 in Europe, and from the well nigh general activity in mathe- 

 matical and geological research, we may hope if not expect 

 that the end of the present century will signalize a similar 

 epoch of productive activity. The minima periods which 

 followed the epochs of Newton and Laplace are less definitely 

 marked but not less noteworthy and instructive. They were 

 not the jjeriods of placid repose ; to find such one must go 

 back into the night of the middle ages ; but they were periods 

 of greatly diminished energy, periods during which those who 

 kept alive the spirit of investigation were almost as conspicu- 

 ous for their isolation as for their distinguished abilities. Many 

 causes, of course, contributed to produce these minima periods, 

 and it would be an interesting study in philosophic history to 

 trace out the tendency and effect of each cause. It is desired 

 here, however, to call attention to only one cause which 

 contributed to the somewhat general apathy of the periods 

 mentioned, and which always threatens to dampen the ardor 

 of research immediately after the attainment of any marked 

 success or advance. I refer to the impression of contentment 

 with and acquiescence in the results of science, which seems 

 to find easy access to trained as well as untrained minds before 

 an investigation is half completed or even fairly begun. That 

 some such tacit persuasion of the completeness of the knowl- 

 edge of the earth has at times pervaded scientific thought, 

 there can be no doubt. This was notably the case during the 

 period which followed the remarkable epoch of Laplace. The 

 profound impression of the sufficiency of the brilliant discov- 

 eries and advances of that epoch is aptly described by Carlyle 

 in the half humorous, half sarcastic language of Sartor Re- 



