5gl PHILOSOPHICAL TRANSACTIONS. [aNNO 1748. 



about 8 miles nearly n.w. of Edinburgh ; which place was chosen as being, 

 by the computations of this eclipse, at or very near the southern limit of the' 

 annulus. 



In the castle of Aberdour, lat. 36° 4' n. and 25^ of time west of the college of 

 Edinburgh, they set up a clock, July Q ; but the weather being cloudy, and the 

 equal-altitude instrument and transit not being yet arrived, they on the nth 

 made use of an equatorial telescope of Lord Morton's, to find corresponding 

 altitudes of the sun, and at the same time setup a gnomon of 15 feet high. 



The 13th being a clear day, they took equal altitudes with the equatorial tele- 

 scope, and found the clock gained 1 "" 46' in 2 days, and that the sun passed the 

 meridian at 11^ 7*" 6' by the clock. 



July 14th was an exceedingly bad morning, both for wind and rain ; but about 

 8 in the morning, the clouds dispersed, and they had a very clear sun. To 

 observe the eclipse. Lord Morton made use of a reflecting telescope, 12 inches 

 focal length, magnifying about 40 times. Mr. Short made use of a reflecting 

 telescope 4 feet focus, magnifying about 120 times; both belonging to Lord 

 Morton. Mr. le Monnier made use of a refracting telescope, about 9 feet focus, 

 which he brought with him from France, armed with a micrometer, made after 

 the method of Mr. George Graham, by the late Mr. Sisson at London. Mr. 

 le Monnier took his station in the garden, under the window of the room where 

 the clock was placed ; Lord Morton was in the room next that where the clock 

 stood; and Mr. S. was at the window next the clock. 



True Time, 

 gh 47m 5s 'pj^g eclipse not yet begun. Clouds come on. 

 8 51 18 Beginning of the eclipse, found by the following chord. 

 8 52 47 First view of the eclipse, then considerably advanced. 



8 54 35 Measured the chord of the part eclipsed ; which was found equal to 



the field of the great reflector. 



9 58 12 The illuminate part of the sun, measured by the micrometer, and 



found = 7' 37*-i-. ' 



10 37 O Again measured, and found = 7' 37"-^. 



Lord Morton judged the middle of the eclipse, or nearest approach 

 to an annulus, at lO** 17"" 54' apparent time. 



11 44 40 The same phase or chord observed as at the beginning, and mea- 



sured both in the telescope, as at first, and by the micrometer, 

 and found = 8' 25" of a great circle, as verified by a base after 

 the eclipse was over, which gives the end as exact as the be- 

 ginning. 

 11 48 18 End of the eclipse by the preceding chord. 



Mr. le Monnier measured with the micrometer the apparent equatorial dia- 



