646 PHILOSOPHICAL TRANSACTIONS. [aNNO 1/23. 



with the aurora borealis, rose out of a seeming black cloud, though it was really 

 no cloud, as the stars shone plainly through it, and the moon shone bright. 

 The motions of the streams of light were very surprising, and extending to 

 the zenith. 



March 27, 17 IQ, it vvas observed with various oblique radiations, as repre- 

 sented fig. 13. 



Jan. 3 J, 1720, from 7 till 10, it was very high, and extended over half the 

 heavens from east to west, and giving light enough to read by. 



Jan. 6, 1721, between 7 and 8 o'clock, it was observed with pyramidal cor- 

 ruscations issuing on all hands from the zenith, as from a centre, and almost 

 resembling an umbrella. 



An Account of a Catadioptric, or Reflecting Telescope, made by John Hadley* 

 Esq. F.R.S. With the Description of a Machine contrived by him for the 

 applying it to me. N'^ 376, p. 303. 



The instrument consists of a metalline speculum, about 6 inches in diameter. 

 The radius of the sphere, on which its concave surface was ground, is JO feet 

 5-J- inches, and consequently its focal length is 62-|- inches The back has a 

 hollow screw made at its centre to receive the end of a handle, which is screwed 

 on, whenever the metal is to be moved, to avoid sullying its polished surface 

 by handling. 



This object metal A, fig. 1, pi. VJ , is placed in one end of an octangular 

 tube, BB, about 6 feet long, and something wider than what is sufficient to 

 receive the metal, died black on the inside. About 6 or 7 inches in length of 

 the three uppermost sides of the tube c, toward that end at which the metal is 

 placed, are separated from the rest, and open with two hinges, to make room 

 for the metal to be put in and taken out. The end of the tube is closed by 

 an octangular piece of board d, which has an opening d, about ^ of an inch 

 broad, from the top down to a little below the centre, to give room for the 

 beforementioned handle, when the object metal is lifted into or out of the tube; 



* We have been able to find but very few biographical memorandums of this very respectable 

 member of the Royal Society. On May 27, i731, we find him offering to the Society an instru- 

 ment he had invented for discovering the longitude. And again, in Sept. 1732, we find a memo- 

 randum, that by the assistance of Dr. Halley's exact calculation of the moon's motion, he had eft'ec- 

 tually discovered the longitude. His communications to the Royal Society are contained in the 

 volumes of the Philos. Trans, from vol. 32 to 39, inclusively. He has been chiefly celebrated by 

 the invention of his reflecting instrument for taking angles, called the Hadley's quadrant, offered to 

 the Royal Society in 1731, by which his name is rendered immortal. Mr. Hadley died Feb. 

 15, 1744. 



