1 8 Cht the Hypothesis of Gaseous Itepulsion. 



own projier motion to the star again, which will cause the in- 

 dices to pass over an arc equal to twice the zenith distance. 

 Again turn the instrument haU' round in azimuth, and with the 

 telescope fixed in the last position, by the general motion again 

 bisect the star, and again by its proper motion make the level 

 horizontal: now turn halt round in azimuth, correct the po- 

 sition of the level as before, and in order to come at another 

 double zenith distance, carry round the telescope to the star 

 again. This process having been continued until enough has 

 been done, the total arc passed over by tlie indices, divided by 

 double the number of complete operations, gives the zenith 

 distance of the star. There is indeed another way of observing 

 by repetition with this instrument. For die same effect will 

 be produced, if, instead of turning half round in azimuth, the 

 circle be turned to the other side of the pillar, on the motion of 

 the cross axis. But, in this case, there must either be a stop 

 to prop the circle on the other side when its plane is vertical, 

 or else the level must be a hanginff one, which will oive the 

 circle Its vertical position whether it is above or below the axis. 

 It would be altogether unnecessary to describe the process of 

 repetition in this case; for, except in what has just been 

 stated, it differs not from the former one. A nominal difference 

 indeed takes jjlace ; for the former method })roceeded by stops 

 of double zenith distance, and this proceeds by stops of double 

 altitude. 



[To be continued.] 



B, 



III. On the Hypothesis of Gasemis Repulsion. By 

 John Herapath, Esq. 



( Cranford, London, July 4, 182"3. 



►UT whether," says Sir Isaac Newton, after having investi- 

 gated the laws of a supposed repulsion between the particles 

 of aeriform bodies, "elastic fluids do really consist of particles 

 mutually flying one another, is a physical question. I have 

 mathematically demonstrated the property of fluids having 

 such particles, that hrnce philosophers may take occasion to dis- 

 cuss that question." — Principia, Book ii. Prop. 23. Scholium. 



Notwithstanding this unquahfied declaration of Newton 

 himself to the contrary, some jjhilosophers strangely asseit, 

 that he has demonstrated the existence of a repulsive "property 

 in the particles of gaseous bodies. Convinced of the justness 

 of most of his observations, from the failure of my attempts in 

 a different course in the early part of my pursuits; and satis- 

 fied that it is to a steady prosecution of his ideas unmixed 

 with those of others, that I owe whatever success I may have 

 met with, few individuals would be less disposed than 1 should 



to 



