558 PHILOSOPHICAL TRANSACTIONS. [aNNO 1732. 



be made of brass by Mr. Sisson, for taking the distance of any kind of objects. 

 It is supported by a single stem screwed to it on the under side, the lower 

 end of which n)ay rest on the ground, to ease the observer of the weio-ht of 

 the instrument. This stem is also made to lengthen or shorten, by which 

 means the instrument is brought to the proper height for any observer's eye, 

 either standing or sitting. Instead of a ball and socket, it has two circular 

 arches fixed on its back, by which it is readily set to any position which the 

 situation of the objects may require. 



The commissioners of the Admiralty having been pleased to order the 

 Chatham-Yacht for the triiil of the instrument, and to give directions to Mr. 

 James Young, master attendant at Chatham, a gentleman well skilled in navi- 

 gation, to be present at the trial, Mr. Fl's two brothers and himself went on 

 board accordingly Aug. 30; being favoured with the company also of Sir Rob. 

 Pye, Bart, and Rob. Ord, Esq. Members of this Society. They met Mr. 

 Young at Sheerness the next day, who accompanied them down about 3 leagues 

 below the Nore, near the Spile-Sand, and was on board on Friday, Sept. 1, 

 when they lay by there, and the several altitudes of the sun were taken as it 

 approached the meridian from about 10 o'clock till noon. 



The Obseivatio7is were as follow: — Aug. 30, near midnight, Mr. Bradley ob- 

 served the distance of Lucida Lyrae from Cor Aquilas by the brass instrument 



off Gravesend in still water 34° 13' 30'' 



The same repeated was 34 13 15 



The error of the instrument in that place is 23" to be subtracted. 



The distance of those stars, according to Mr. Flamsteed, is 34 II 50 



Which by the refraction is reduced to 34 II 10 



Aug. 31, about lO*" SO"", Mr. Bradley observed the distance of Capella from 

 the North Pointer in the Great Bear's back, by the same instrument, while we 

 lay at anchor in the mouth of the Medway near Sheerness, the wind blowing 



hard at north east 49° 14' O' + 



Or 49 15 O 

 Mr. Bradley and myself making a small difference in numbering the angle 

 marked by the index. 



The error of the division of the instrument there is 30" to be added. 

 The distance of those stars, according to Mr. Flamsteed, is . . 49° 16' O" 



By the refraction reduced to 49 14 20 



Clouds coming up prevented the repeating this observation, nor had we any 

 opportunity of making any others of this kind. 



The following altitudes of the sun were observed by Mr. Bradley, lying at 

 anchor in the mouth of the Medway. Aug. 31, afternoon, the wind at north- 



