Skptbmbkr 1-2, 1902.] 



SCIENCE. 



411 



was the central attracting- body and every 

 planet and each satellite was obedient to 

 this all-controlling force. 



Thus, while the correct seqiienee is, 

 logically, the deduction of Kepler's Laws 

 from the Laws of Gravitation, the fact is 

 that the relation was discovered by scientific 

 use of the imagination and the confirmation 

 by deduction from an assumed accuracy of 

 those primary laAvs followed. 



Newton's estimate of his work, as that 

 of 'a child plajdng on the seashore' while 

 'the immense ocean of truth extended it- 

 self unexplored' before him, in the light 

 of these considerations seems less remark- 

 able. Newton did indeed play on the 

 shore of the great ocean of truth, and 

 mused and speculated as he played ; but he 

 also did what the greatest of the ancient 

 philosophers declined to do — he speculated 

 with the aid of all his reasoning power, and 

 then submitted his deductions to the touch- 

 stone of direct test by experiment and by 

 comparison with the facts revealed by re- 

 search. 



Again and later: Lagrange and Laplace 

 discovered and enunciated the two ' Laws 

 of Stability,' the 'Magna Charta of the 

 planetary systems ' ; but the discovery was 

 brought about by a scientific use of the 

 speculative faculty, and the laws were con- 

 firmed by reference to the whole system of 

 gravitational mechanics founded by Galileo 

 and Newton, proved by experiment and 

 confirmed by long years of accurate obser- 

 vation. Laplace 's ' Nebular Hypothesis ' 

 was a 'sublime speculation.' Its accept- 

 ance or rejection is made by every man 

 of science, subject to its confirmation or 

 disproof by direct appeal to fact. 



Scientific prophecy, illustrated by the 

 magnificent work of Adams and Leverrier 

 in their computation of the elements of the 

 orbit of Neptune, from the known meas- 

 ures of variation of other planets in their 

 orbits produced by disturbances set up by 



the unknown planet, is the loftiest of all 

 forms of product of the mind of man. 

 Prediction was a common fact in science at 

 an early date ; but it never before had been 

 the fact that a great mathematical astrono- 

 mer, in his study, with tabulated figures of 

 irregular motions of heavenly bodies before 

 him, had even attempted to compute the 

 position of that disturber of the harmony 

 of the spheres and to say to the observer 

 at the telescope : ' Direct your glass at the 

 infinitesimal point in all the sky indicated 

 by these computed measures and you shall 

 see a new world.' It was thus, however, 

 that Neptune was found. 



V. 



The methods of conduct of experimental 

 research are in general simple and have one 

 common system. The preliminary survey 

 having been made, the work of earlier in- 

 vestigations having been collated and ar- 

 ranged with reference to the purpose in 

 view, and the plan of the work having been 

 in a general way settled, the first step is to 

 determine what apparatus is needed in the 

 prosecution of that plan and what is avail- 

 able. The plan and the aim of the research 

 give the necessary basis of judgment re- 

 garding needed apparatus, and it may often 

 happen that it is all obtainable without 

 difficulty or delay. It oftener occurs, how- 

 ever, that old apparatus must be modified 

 to meet the precise requirements of the 

 work in hand, and that, in many cases, en- 

 tirely new must be devised. Sometimes an 

 important, or at least quite novel and in- 

 genious, instrument or machine must be 

 invented to meet a special need. The plan 

 itself has given opportunity for the exer- 

 cise of both invention and imagination ; the 

 selection, the construction and the assign- 

 ment to specific work of the apparatus will 

 be found to demand in most cases even 

 more of both these attributes of genius. 



The apparatus having been thus selected. 



