which will happen on Septcmher 7, 1S20. 



93 



The whole duration of t!ic eclipse will, at all these places, be 

 rather more than two hours and three quarters. But the dura- 

 tion of the annulas will not, in any place, exceed six minutes: 

 :and, in some places (at the confines of the umbra) it will be mo- 

 mentary. The nearer the spectator happens to be to the centre 

 of the path of the moon's umbra, the longer will the annular ap- 

 pearance continue. 



Having thus given a general outline of this eclipse, I shall pro- 

 ceed to state the principal ph;enomena which have been observed 

 in former eclipses of this kind*, whereby the reader may be aware 

 of the principal observations to whicii it will be proper for him 

 to attend, and make his preparations accordingly. Many of 

 these phaenomena have given rise to much discu.ssioii, and are far 

 from being accurately determined, or reduced to general princi- 

 ples. There is also a degree of doubt respecting the existence 

 of some of them. Those persons therefore who are furnished 

 with convenient instruments, and have a favourable opportunity, 

 should carefully attend to, and note down, not merely the phases 

 of the eclip.sc but such other appearances as may present them- 



* Those ol 1 T'-'tl iiii<l 1 748. There aic biil lew ol)scrv,ilious of the eclipse 



>.clvcs. 



