VOL. XXXVII.] I'HiroSOPHICAL TRANSACTIONS. 531 



The Observations Mr. Robie made on the Solar Eclipse, Nov. 27, 1722, 

 ivere as folloiv : 



•jb 27^" 0' He saw the sun rise eclipsed about 4 digits on his upper part. 

 Then we could observe no more till 



8 30 O The sun began to appear, and about 6 digits were eclipsed. 



9 25 45 End of the eclipse. 



Description of a new Quadrant for taking Altitudes luithout a Horizon, either 

 at Sea or Land. Invented bij Mr. John Elton. N° 423, p. 273. 



This instrument, fig. 1, pi. 14, contains 4 principal parts; viz. a frame, an 

 index, a label, and a shield; and these consist of several parts. 



The frame, abcdef, has two parts; one a graduated arch de of 30°; each 

 degree being subdivided into 6 equal parts ; the other a chord bc of an arch of 

 6o°, divided into 2 equal parts (at the extremities and in the middle of which 

 are holes or stops for the label) together making 90° or a quadrant. 



The index gh turns on the centre of the frame the whole compass of the 

 arch, and has 3 parts; viz. a nonius plate, n, and eye- vane, v, and a tubet. 

 The nonius plate moves with the index, and subdivides each of the small divi- 

 sions of the arch into 10 equal parts or minutes. The eye- vane is to look 

 through in forward observations. The tube is to show when the index is 

 horizontal. 



The label ik moves on the centre of the frame the whole compass of the 

 chord of the arch of 6o°, having 3 fixed stations on it, at 30", Qo°, and 90°, 

 and contains two principal parts; viz. a lens 1, and a lantern whose stool is o. 

 The lens is to form the sun's image on the shield. The lantern is necessary 

 in nocturnal observations. 



The shield, or ray-plate dfg, is fixed in the centre of the frame, and has 

 three parts ; viz. an azimuth tube, z, a horizontal tube, h, and an axis, x, or 

 in backward observations a ray-plate. The hole in the shield is to receive 

 the sun's image. The azimuth tube is to direct the plane of the instrument 

 perpendicular. The horizontal tube is to show when the label is level. The 

 axis is to cut the object in forward observations. 



A Rule for either backivard or forward Observations. — If the altitude do 

 not exceed 30°, the label must be placed at the station on the radius or longest 

 limb of the quadrant ; if the altitude be between 30" and 60°, at the middle 

 station; and if the altitude exceed 60", at the uppermost station. 



To take the Suns Altitude by a backward Observation. — This is done with- 

 out using the sight-vane or horizontal tube on the shield. Hold the quadrant 

 3 Y 2 



