214 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



selves by assiduous exercise and by communicating in part to their 

 descendants the improvements tlius acquired. It is this way of 

 thinking which, after a turn toward Darwinism/ has finally estab- 

 lished itself. NoWj to permit such an evolution of the organic 

 world, from the beginnings to its actual perfection, requires a consid- 

 erable duration of cosmic quiet. Geologic investigations since Lyell 

 have indeed demonstrated that the passage from each geologic forma- 

 tion to that succeeding it is made gradually and without interruption. 

 The inundations and volcanic catastrophes which are produced at all 

 times, far from destroying worlds, have never been more than purely 

 local. Volcanic eruptions are not the index of a fluid and incan- 

 descent nucleus, for the accumulations of liquid lava have little 

 extension, so that even neighboring volcanoes, such as Vulcano and 

 Stromboli, have no relation to each other. One can even affirm that 

 the fluid incandescent nucleus of the earth does not exist. Recent 

 physical observations, especially those relative to the transmission 

 of the transverse seismical waves through the interior of the earth 

 and to the period of migration of the terrestrial axis, admit of the 

 conclusion that the earth in its entire mass is as elastic as a steel of 

 good quality. 



But now we must observe the very disquieting previsions of the 

 exact sciences. These we must notice particularly, for physics and 

 astronomy have exact natural laws, and in this way may be predicted 

 in all probability the most distant consequences, for the laws which 

 are concerned here, that of gravitation and that of the conservation 

 of energy, are among the ones most firmly established. 



The real achievement of Newton was to show that the law of 

 gravitation had a more exact application than the laws of Kepler 

 according to which the planets move along their elliptical orbits.^ In 

 reality the planets do not describe strictly elliptical trajectories. 

 The fomi and the position of these trajectories change constantly, 

 although with extreme slowness. The law of Newton affords an 

 explanation of the greater part of these divergences, if the reciprocal 



1 In this connection we designate as Darwinism only that part of Darwin's teachings 

 which originated with himself ; not the evolution theory, which is due for the most part 

 to Lamarck, but rather the theory of selection, according to which there could not be 

 any evolution of the organic world without the influence of selection in connection with 

 the struggle for existence. 



2 The law of gravitation itself was not originated by Newton, but by Kepler, whose 

 ideas exerted a powerful influence on Hooke, Halley, and Fermat. It was first formu- 

 lated mathematically by Wren, whose physical work was otherwise unimportant. Newton 

 only contributed proof of its correctness. 



Kepler originated the fundamental and extraordinary new conception " Virtutem, quae 

 planetas movet, residere in corpore Solis " ("The power which moves the planets resides 

 in the mass of the sun " — heading of ch. 33 in Kepler's "Astronomia Nova." See " Jo. 

 Kepleri Opera Omnia," Frisch's edition, vol. 3, p. 300). He also originated the idea of 

 the field of gravitation, in which the force diminishes with the distance from the sun, 

 and the idea of universal gravitation. Had Galileo's dynamics controlled Kepler as it did 

 Huyghens, he would not have needed half his genius to have anticipated Newton's con- 

 tributions to the subject. 



