846 



SCIENCE 



[N. S. Vol. XV. No. 387. 



that of deduction. Time is wanting for an 

 examination of the details of this ambitious 

 scheme, noz- is it necessary to say that in 

 its main purpose it proved a lamentable 

 failure. Nevertheless the Cartesian phi- 

 losophy enjoyed great popularity on the 

 continent of Europe for many years, where 

 it blocked the way to the acceptance of the 

 true doctrine of gravity as developed by 

 Newton. It is a disputed point whether 

 this system was more of a help or a hin- 

 drance in furthering the cause of truth. 



It seems a little strange perhaps that a 

 mind so acute as that of Descartes, whose 

 possessor made such important contribu- 

 tions to pure mathematics, should not have 

 perceived, as did his contemporary. Bacon, 

 that the truths of nature can only be 

 learned by the study of nature, by a 

 patient and careful attention to details, dis- 

 carding at once the notion that our feeble 

 powers can by any possibility attain to a 

 comprehension of the entire scheme of the 

 universe. 



As an illustration of the process by 

 which the sciences having to do with the 

 material things of nature are developed let 

 me invite your attention to that one with 

 which I am more familiar than with any 

 other, astronomy. 



There is no people or tribe so rude or so 

 2ow in the scale of intelligence as not to be 

 familiar with some of the fundamental 

 truths of astronomy. In fact we may al- 

 most say that the lower animals possess 

 some astronomical knowledge. But a 

 familiarity with the diurnal and annual 

 motions of the sun, the changes of the moon, 

 and even the ability to recognize at sight 

 every star visible to the eye, to assign its 

 proper place in the constellation to which it 

 belongs and to tell at what season of the 

 year it is visible, all this comes far short of 

 constituting a science of astronomy. These 

 phenomena and many others had occupied 

 the attention of the Chaldeans and Egyp- 



tians for hundreds of years, but these peo- 

 ple never had anything which could prop- 

 erly be called a science of astronomy. 

 Nevei-theless the records of eclipses and 

 other phenomena preserved by these stu- 

 dents of the heavens were of very great ser- 

 vice to the true founder of the science, 

 Hipparchus, about 150 B.C. The first step 

 toward the founding of any science is the 

 same in character. A working hypothesis 

 must be devised which will connect together 

 in the best manner possible the detached 

 facts of observation. It is here that a 

 judicious use of the scientific imagination 

 is called for. 



If the choice of a hypothesis is a happy 

 one it may prove to be the first approxima- 

 tion to the true law of which we are in 

 search. It is to be adhered to so long as 

 we can represent by it in a satisfactory 

 manner all of the facts of observation, and 

 the moment when it is found to conflict 

 with observation it must be modified or 

 abandoned. The investigator who sets him- 

 self to work looking for facts to sustain a 

 favorite theory is pretty likely to succeed 

 to his own satisfaction, but he is not the 

 man who contributes greatly towards in- 

 creasing the world's store of scientific 

 knowledge. 



But to return to Hipparchus. His sys- 

 tem is well known. The earth was the cen- 

 ter of the universe; the mechanism of the 

 celestial motions was a combination of cir- 

 cles; by properly proportioning the parts 

 of the machine the celestial motions could 

 be represented with as high a degree of 

 accui-acy as they could be observed with 

 the primitive instruments of those days. 

 Eclipses and other celestial phenomena 

 could be predicted, axid the thoroughness 

 with which the work was done is attested 

 by the fact that this system answered all 

 requirements for a period of more than 

 1,500 years. Yet we know that what we 

 may call the two fundamental hypotheses 



