496 Dr. J. R. Mayer on the Mechanical Equivalent of Heat. 



while at the same time the motions of the innumerable heavenly 

 bodies are of so complicated a kind, that astronomical science, 

 in its'stately unfolding, is rightly considered the highest triumph 

 whereof human intellect here below is able to boast. 



In accordance with the natural rule that, both in particulars 

 and in general, man has to begin with that which is easiest and 

 then to advance step by step to what is more difficult, it might 

 well be supposed that astronomy must have arrived at a flourish- 

 ing state of development later than any other branch of human 

 knowledge. But it is well known that in reality the direct 

 opposite was the case, inasmuch as it was precisely in astro- 

 nomy, and in no other branch, that the earliest peoples attained 

 to really sound knowledge. It may, indeed, be asserted that the 

 science of the heavenly bodies had in antiquity reached as high 

 a degree of perfection as the complete want of all the auxiliary 

 sciences rendered possible. 



This early occurrence of a vigorous development of astronomy, 

 which, indeed, was a necessary forerunner of the other sciences, 

 since it alone furnished the necessary data for the measurement 

 of time, is observable among the most various races of mankind : 

 the reason of it, moreover, lies in the nature of things, and in the 

 constitution of the human mind. It furnishes a remarkable 

 proof that a right method is the most important condition for 

 the successful prosecution of scientific inquiry. 



The explanation of this phenomenon lies in the fact that the 

 need which was felt at a very early period, of a common stand- 

 ard for the computation of time, made it necessary to institute ob- 

 servations such that their results required to be expressed by defi- 

 nite numbers. There was a felt necessity of determining the time 

 in which the sun accomplishes his circuit through the heavens, 

 as well as the time in which the moon goes through her phases, 

 and other similar questions. In order to meet this necessity, 

 there was no temptation to take up the Book of Nature, after 

 the manner of expositors and critics, merely to cover it with 

 glosses : 



" Mit eitler Rede wird hier nichts geschafft." 



It was numbers that were sought, and numbers that were found. 

 The overpowering force of circumstances constrained the spirit 

 of inquiry into the right path, and therein led it at once from 

 success to success. 



Now that after long-continued, accurate, and fortunate obser- 

 vations the needful knowledge of the courses and distances of 

 the nearest heavenly bodies, as well as of the figure and size of 

 the earth, has been acquired, we are in a position to treat the 

 question, What is the numerical influence exerted by increased 

 distance from the earth upon the known laws of falling bodies ? 



