172 ASTRONOMICAL HISTORY. 



CHAP. VII. 



The following are Questions relating to the Substance of 

 the Heavenly Bodies ; viz. What Species of Substance is 

 that of the Heavenly Bodies generally, compared to Sub 

 lunary Bodies ; the Substance of the interstellar Ether 

 compared to the Body of a Star; the Substance of the 

 Stars themselves compared to one another, and compared 

 to our Fire, and in its proper Essence ; and what Species 

 of Substance is that of the Galaxy, and of the opake 

 Macula visible in the Antarctic Hemisphere ? Then the 

 First Query is set forth, Whether there is a diversity of 

 Substance between Bodies celestial and sublunary, and in 

 what it consists ? 



HAVING finished our inquiries respecting the system, we 

 must now proceed to those which regard the substance, of 

 the heavenly bodies ; for it is the substance of the heavenly 

 bodies, and the courses of their motion, that philosophy 

 chiefly seeks to know. Astronomy investigates their real 

 motion itself and its properties both astronomy and phi 

 losophy their influence and effect. 



Care ought to be taken, however, accurately to distin 

 guish between astronomy and philosophy : astronomy pre 

 ferring those hypotheses which are most convenient for 

 shortening the method of calculation ; but philosophy 

 those which most approximate to the truth of nature : 

 further, that, on the one hand, the hypotheses of astro 

 nomy do not in any way prejudge truth; and on the other, 

 the positions of philosophy be such as are perfectly tenable 

 upon the phenomena of astronomy. Whereas, on the con 

 trary, the fact now is, that the figments of astronomy have 

 insinuated themselves into philosophy, and perverted it; 

 and the theories of philosophers about the heavenly bodies 

 are reconcileable only to themselves, and in a great measure 

 abandon astronomy, contemplating in general the system 

 of the heavens, but by no means accommodating them 

 selves to particular phenomena and their causes. Thus 

 while either science, such as we now have them, is a thing- 

 superficial and perfunctory, the foot must be planted more 

 vigorously by far on this foundation that these two 

 sciences, which, by reason of the contracted speculations 

 of men, and the practice of academic teachers, have been 



