THE MECHANICAL EQUIVALENT OF HEAT. 



objects and spaces which forbid all thought of experiment, 

 while at the same time the motions of the innumerable heavr 

 enly bodies are of so complicated a kind, that astronomical 

 science, in its stately unfolding, is rightly considered the high- 

 est triumph whereof human intellect here below is able to 

 boast. 



In accordance with the natural rule that, both in particu- 

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

 easiest and then to advance step by step to what is more diffi- 

 cult, it might well be supposed that astronomy must have ar- 

 rived at a flourishing 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 astronomy, and in no other branch, that the ear- 

 liest 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 as- 

 tronomy, 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 va- 

 rious 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 

 standard for the computation of time, made it necessary to 

 institute observations such that their results required to be 

 expressed by definite numbers. There was a felt necessity of 

 determining the time in which the sun accomplishes his cir- 

 cuit through the heavens, as well as the time in which the 

 moon goes through her phases, and other similar questions. 



