100 Memoir relative to the Annular Eclipse of the Sun, 



inometer however fell only 2y degrees : and the Ahh6 NoUct 

 found that his huniing-glass was then as powerful as before the 

 eclipse began. M. De L'isle, likewise, who observed this eclipse 

 at the Luxembourg, remarks that the thermometer did not indi- 

 cate any increase of cold caused by the eclipse, although he and 

 many other persons experienced it soon after the middle of the 

 eclipse *. 



In the eclipse of 173/ Maclaurin observed that a burning- 

 glass which kindled tinder and l)urnt cloth towards the end of 

 the eclipse, had no effect during the existence of the annulus, nor 

 for some time before and after it. He likewise remarked that 

 " during the appearance of the annulus, the direct light of the 

 sun was still very considerable: and that although some places, 

 that were shaded from his light, appeared gloomy, yet that the 

 day light was not greatly obscured." He adds that many per- 

 sons, about the middle of the annular appearance, although not 

 short-sighted, were unable to discover the moon ^upon the sun 

 when they looked without a smoked or coloured glass f. Never- 

 theless Venus and some other stars were visible at the same time: 

 and Venus continued visible even after the annulus was dissolved. 

 Venus was also seen in the eclipse of 1748, but it does not ap- 

 pear that any other star was then visible. 



If the diminution of light should be considerable (which there 

 is not much reason however to suspect J), Mercury, Venus, and 

 Mars, together with some of the principal fixed stars may be vi- 

 sible to the naked eye. Mercury, if visible, will be seen about 

 18° to westward of the sun, nearly in conjunction with Regulvs: 



• In the total eclipse of 1 724 the thermometer had fallen only two degrees 

 at the time of the middle of the eclipse. This is the more remarkable as 

 the eclipse took place late in the afternoon of the 22d of May, at which time 

 we might presume that the atmosphere would be gradually becoming more 

 cool. The total darkness took place at &\ 48'. F.M. 



f M. Le Monnier mentions the same thing of himself in the eclipse of 

 1748. _ ° ^ 



X In the annular eclipse of 1 764 an ignorant country clergyman alarmed 

 the people of France by announcing that there would be total darkness du- 

 ring the existence of the annulus : and the Royal Academy of Sciences at 

 Paris thought proper to give this report a formal contradiction. It is well 

 known howevcn- that the smallest ray of light from the sun would prevent 

 such a phaenomencn ; as I have shown more at length in my paper " On 

 the solar eclipse which is said to have been predicted by Thales," inserted 

 in the Phil. Trans, for 181 1, part ii. page 220. 



I shall here take the opportunity of correcting a typographical error in 

 that paper ; where, in page 240, line 22, " three degrees " should be " three 

 minutes." Since the publication of that paper, I find that the Bureau des 

 Longitudes \\\ France have printed a Supplement to M. Burgh's Lunar Tables, 

 wherein the mean epoch and mean motion of the Supplement of the Node 

 are considerably altered ; so as to bring the latitude of the moon within the 

 limits which I there suggested. 



Venus 



J 



