460 PHILOSOPHICAL TRANSACTIONS. [aNNO 1778. 



experiments were repeated again; the copper ball being put nearest to the glass 

 instead of the forked part, and the forked part in the place of the copper ball. 

 This set of experiments being completed, they made others, where the ball only 

 was opposed ; and after them, where the point only was opposed to the copper 

 ball. 



Having gone through all these experiments, they then repeated the experiment 

 with the chain, after Mr. Henly's manner. The chain employed on this 

 occasion was of iron, and very rusty, no other being then at hand. To avoid 

 every objection, it was resolved on, that all the experiments they had made at 

 Dr. Higgins's should be repeated, but with the two chains instead of the forked 

 apparatus. On the 23d of June they went through the whole of the experi- 

 ments thus circumstanced. The chains employed were brass, and a glass stand 

 supported the ball and point. The cylinder measured about 13 inches in 

 diameter: this glass, with the assistance of Dr. Higgins's amalgama, acted 

 powerfully. All these experiments show that the point was struck at a greater 

 distance than the ball. 



XLV. Observations on the Solar Eclipse which happened June 24, 1778. By 



Mr. W. Wales, F. R. S., and Master of the Mathematical School in Christ's 



Hospital, p. 1013. 



The following observations of the solar eclipse, which happened on the 24th 

 instant, were made at the Royal Mathematical School in Christ's Hospital, 

 where the latitude is 51° 30' 55* n. and the longitude not quite half a second in 

 time west of the cupola of St. Paul's. The time was taken by a most excellent 

 watch made by Mr. Larcum Kendall, which goes while it is winding up, and 

 has a provision for counteracting the effects of heat and cold. It was regulated 

 by double altitudes of the sun's lower limb, taken from a basin of quicksilver 

 with a Hadley's quadrant of Mr. Ramsden's making; and the quicksilver was 

 shaded from the wind by a roof, formed by 2 glasses whose planes had been 

 ground perfectly parallel by the same ingenious artist, so that the time may be 

 depended on within a second, or 2 seconds at the most. 



The telescope, which is of the Gregorian form, was made by the late 

 Mr. Short; the focal length of the great speculum being 18 inches, and the 

 aperture 4-j- inches. He used a magnifying power of about 75 times for the 

 beginning and end, and of about 50 or 55 times with the micrometer, in mea- 

 suring the sun's diameter, and the distances between the 2 cusps of the 

 luminaries. The micrometer, which is an exceeding good one, was made also 

 by Mr. Short. The divided glass is not achromatic, but only a single lens, 

 whose focal length is about 28 feet 5i inches; but as he had not an opportunity 

 of examining this point himself by adjusting the telescope to parallel rays 



