184 THE GENESIS OF SCIENCE. 



used to distinguish the heavenly bodies that arc of like na 

 ture with the sun from those which are not. It w r as thus 

 when, as recently, an electro-telegraphic instrument was in 

 vented for the more accurate registration of meridional 

 transits. It was thus when the difference in the rates of a 

 clock at the equatdr, and nearer the poles, gave data for 

 calculating the oblateness of the earth, and accounting for 

 the precession of the equinoxes. It was thus but it is 

 needless to continue. 



Here, within our own limited knowledge of its history, we 

 have named ten additional cases in which the single science 

 of astronomy has owed its advance to sciences coming after 

 it in M. Comte s series. ISTot only its secondary steps, but 

 its greatest revolutions have been thus determined. Kep 

 ler could not have discovered his celebrated laws had it not 

 been for Tycho Brahe s accurate observations ; and it was 

 only after some progress in physical and chemical science 

 that the improved instruments with which those observa 

 tions were made, became possible. The heliocentric theory 

 of the solar system had to wait until the invention of the 

 telescope before it could be finally established. Nay, even 

 the grand discovery of all the law of gravitation depend 

 ed for its proof upon an operation of physical science, the 

 measurement of a degree on the Earth s surface. So complete 

 ly indeed did it thus depend, that Newton had actually 

 abandoned his hypothesis because the length of a degree, 

 as then stated, brought out wrong results ; and it was only 

 after Picart s more exact measurement was published, that 

 he returned to his calculations and proved his great gener 

 alization. Now this constant intercommunion, which, for 

 brevity s sake, we have illustrated in the case of one science 

 only, has been taking place with all the sciences. Through 

 out the whole course of their evolution there has been a 

 continuous consensus of the sciences a consensus exhibit 

 ing a general correspondence with the consensus of facul 



