194 ESSAYS AND OBSERVATIONS 



bing a great circle of the earth by the di- 

 •urnal motion, that is always bifec1:ed by 

 the boundary of light and darknefs, >{»'hich. 

 is likewife a great circle in confequence of 

 a necefTary truth. The polei would haye 

 their fix months day and fix months. n:t?ht, 

 as now ; with this further fingulai ity^ 

 that, when the axis lay in the plane of cbe 

 eclipiic, the heat mufl have been far more 

 intolerable at the poles than is now known 

 in any part of the ear'-h, or could be koo'.vr^ 

 in any other part of it, during this loiig 

 period ; For the fun n^uft have then con- 

 tinued ten days together within 5° degrees 

 of the zenith of the poles, without any 

 intermiiTion of night, or abatement from 

 a lefTer elevation, at which altitude he ne- 

 ver continues above 40' in the cquinoili- 

 al days at th^ equator ; a peculiarity as 

 fingular as it would have been fatal to the; 

 polar regions. T he prefent obliquity of 

 the ecliptic gives evidently great relief to 

 the equatoreal regions ; as by it th^ fun 

 is carried to both fides of the zenith du- 

 ring the year, and is not permitted to dart 



conftantly 



