[ io 3 ] 



In the focus of the eye-glafs pafrail \ to one another* 

 and to the plane of the quadrant. If they were put 

 at fuch a diftance as to divide the diameter of the 

 field of view into three equal par-is, it might be as 

 convenient as any other interval. In this manner 

 wires were placed in the telefcope by Mr. Hadley, 

 as appears by his account of the inftrument in 

 Philof. Tranf. N° 420. Thefe wires are to be ad- 

 jutted parallel to the plane of the quadrant, by turn- 

 ing the eye-tube round about which contains the 

 wires, till they appear parallel to the plane of the 

 quadrant. The axis of the telefcope, by which rs 

 meant the line joining the centre of the object-glafs 

 and the middle point betweep the two wires, is to be 

 adjufted parallel to the plane of the quadrant by 

 either of the two following methods. 



.ill: method. When the diftance of the Moon 

 from the Sun is greater than 90 degrees, by giving a 

 fweep with the quadrant and moving the index, bring 

 the neareft limbs to touch one another at the wire. 

 nearer! the plane of the quadrant. Then, the index 

 remaining unmoved, make the like obfervation at: 

 the wire fartheft from the plane of the quadrant j.- 

 and note whether the neareft limbs are in contact as 

 they were at the other wire :. if they are, the axis ojf 

 the telefcope is parallel. to the plane of the quadrant: 

 but if they are not, it is inclined to the tame, and 

 mult be corrected as follows. If the neareft limbs, 

 of the Sun and Moon feem to- lap over one another 

 at the wire fartheft from the. plane of the quadrant,., 

 the object end of the telefcope is inclined from the/ 

 pUne cf the quadrant, and muft be altered by the. * 

 adjuftir.ent.made for that purpofe 1. but, if the neareft. 



limbs. 



