23 



From a view of the table of the possible distances of the 

 earth from the sun, it will appear, that with a given parallax, 

 each difference of an English mile in the semidiameter of the 

 earth, Avill occasion a difference of about 24,000 English 

 miles in the distance, and that the semidiameter remainin"' 

 the same, the difference of a tenth of a second in the hori- 

 zontal parallax, alters the distance of the earth from the sun 

 above one million of miles: hence, we may conclude, the im- 

 mense distance of the fixed stars from our planet, as no one 

 of them has yet been discovered to be affected by any sensi- 

 ble parallax ; notwithstanding, that to enable us to detect any 

 such apparent change of place in a fixed star, as is called a 

 parallax, we can, by the earth's describing in one year an 

 orbit round the sun of nearly 19O millions of miles in diame- 

 ter, in the course of six months, observe a fixed star's dis- 

 tance from the zenith, at a station that is no less than I90 

 millions of miles distant from that at which we observed its 

 zenith distance six months before. But, as no sensible change 

 of a star's zenith distance is observable on this account, it is 

 evident, that the whole diameter of the great orb of the 

 earth's annual motion round the sun, subtends no discernible 

 angle, as seen from the nearest fixed star. If a fixed star had 

 a sensible parallax of even one second, still, the distance 

 of that star from the sun, would be above 400,000 times 

 the distance of the earth from the sun. And, if a fixed star 

 had a sensible diameter of one second, and also a sensible 

 parallax of oae second, then, its actual dimensions would 

 equal the radius of the orb of the sun's distance from the 



earth. 



