^ 



Corjlrucllon of the Hecvens. 'i\^ 



after Vv'e fhall find reafoii, from experience and obiervatlon, to-. 

 believe that there are parts of our fyflem where the flars are 

 not fcattered in the manner here fupportd, we ought then to 

 make proper exceptions. 



But to return : if fome other high gage be fele6l"ed from the 

 table, luch as 472 or 344, the length of the vifual ray will be 

 found 461 and 415. iind although, in confequence of what 

 has been faid, a certain degree of doubt may be left about the 

 arrangement and fcattering of the ftars, yet when I recollecSl:, 

 that in thofe parts of the milky v/ay where thefe high gages 

 were taken, the fiars were neither fo fmall, nor fo crowded, 

 as they muft have been on a luppofition of a m.uch far- 

 ther continuance of them, when certainly a milky or ne- 

 bulous appearance mAifl: have come on, I need not fear to have 

 over-rated the extent of my vifual ray. And indeed every 

 thing that can be faid to fhorten it will only contracl the lim/its 

 of our nebula, as it has in moft places been of fufficient length 

 to go far beyond the bounds of it. Thus, in the lides of the- 

 flratum oppof te to our fituation in it, where the gages often 

 run below 5, our nebula cannot extend to 100 times the dif- 

 tance of Sirius ; and the fime telefcope, which could Ihew 58 8 

 flars in a field of view of 15 minutes, mufi: certainly have pre- 

 fen ted me alfo with the ftars in thefe fit nations as w~ell as the 

 former, had they been there. If we (hould anlwer this by ob- 

 lerving that they might be at too great a diftance to be per- 

 ceived, it will be allowing that there mufl: at leaf! be a vacancy 

 amounting to the length of a vifual ray not (hort of 400 times 

 the diftance of Sirius ; and this is amply fufficient to make our 

 nebula a detached one. It is true, that it would not be con- 

 fiftent confidently to affirm that we were on an ifland unlefs 

 we had adually found ourfelves every where bounded by the 



oceaiij 



