156 PHILOSOPHICAL TKANSACTIONS. [anNO 1715. 



Nor has this advertisement failed of the desired effect ; for the heavens having 

 proved generally favourable, we have received from so many places so good ac- 

 counts, that they fully answer all our expectations, and are sufficient to establish 

 several of the elements of the calculus of eclipses, so as for the future we may 

 more securely rely on our predictions : though it must be granted, that in this 

 our astronomy has lost no credit. 



The day of the eclipse approaching, I received the orders of the Society to 

 provide for the observation to be made at their house in Crane-Court, and 

 accordingly I procured a quadrant of near 30 inches radius, exceedingly well 

 fixed with telescopic sights, and moved with screws so as to follow the sun with 

 great nicety ; as also a very good pendulum clock well adjusted to the mean 

 time, and several telescopes to accommodate the more observers. 



In order to examine both clock and quadrant, on the !20th of April, I ob- 

 served the distance of the sun's upper limb from the zenith 36° l6', and the 

 next day 35° 58'; by which it appeared that the distances from the zenith taken 

 by this quadrant ought to be increased by about one minute : and that allow- 

 ance being made, by several observations taken before and after noon on the 

 said 21st day, the clock was found to answer the apparent time or hour of the 

 sun with sufficient exactness, as not going above 10'' too fast. The next day, 

 April 22, just before the eclipse began, we took three distances of the sun from 

 the zenith, viz. at 7^ 42"" 52^ A. M. the correct distance of the sun's centre 

 from the vertex was 62° l' 40'' ; at 7^ 45"" 48' it was 6l° 34' 40" ; and again at 

 7^ 48'" 55* it was 6l° 6' 40": which with the given declination of the sun and 

 latitude of the place, show the true times respectively to have been 7^ 42"" 38% 

 and 7*^ 45"" 35' and 7^ 48"^ 39^ all concurring that the clock was only 14 

 seconds too fast, and had gained scarcely any thing sensible in a day's time: so 

 that it might be entirely depended on during the continuance of the eclipse. 



Having computed that the eclipse would begin at 8*^ 7"^^ I attended soon after 

 6 with a very good 6-foot telescope, without stirring my eye from that part of 

 the sun where the eclipse was to begin : and at 8^ 6'" 20' by the clock, I began 

 to perceive a small depression made in the sun's western limb, which immedi- 

 ately became more conspicuous ; so that I concluded the just beginning not to 

 have been above 5 seconds sooner; that is, exactly at 8*^ 6™ correct time. 



From this time the eclipse advanced, and by g o'clock it was about 10 digits, 

 when the face and colour of the sky began to change from perfect serene azure 

 blue, to a more dusky livid colour, having an eye of purple intermixed, and 

 grew darker and darker till the total immersion of the sun, which happened at 

 gh gm J 7s \jy |_}je clock, or 9'' 9™ 3' true time. This moment was determinable 

 with great nicety, the sun's light being extinguished at once; and yet that of 



