1>HYSICAL AND LITERARY. 217 



As It is probable that the height which 

 fome philofophers have afTigned for the 

 ftreamers in the atmofphere, is by feve- 

 fal hundreds of miles too much, it were 

 to be wifhed that people in various lati- 

 tudes would carefully obferve their alti- 

 tude, at different times of the night; 

 that, by comparing fimultaneous obfer- 

 vations, this matter may be determined 

 with more certainty. 



But, becaufe proper inftruments are 

 not always at hand, it will be of ufe to 

 mark the time when any principal range 

 becomes vertical, or the time when the 

 higheft part of the range feems to touch 

 any remarkable ftar. 



These vapours commonly afTemble, 

 at firft, in a broad lucid yellow vein, 

 flowing flowly eaft and weft. By degrees 

 the vapours accumulate and turn bright- 

 er, and, by their mutual colHfions, are 

 at laft kindled and fplit into thoufands of 

 revolving cylindric columns, fhewing a 

 variety of colours, but principally red 

 and green, and the red appears to be un- 

 dermoft. Thus they are fcatrered thro' 

 Vol, I. Ee the 



