[ 53S J 
rec5^:ions, which were previoufly communicated to the 
obfervers. 
A fmall addition w'ill be neceflary to be made to 
the apparatus of the objedt-glafs micrometer, to enable 
it to anfwer thefe purpofes, viz. a cell, containing 
two wires interfedling each other at right angles, 
placed in the focus of the eye-glafs of the telelcope, 
and moveable round about, by the turning of a but- 
ton. Let E N W S, Tab. XVI. P ig. i. reprefent the 
field-bar of the telefcopc, EW and NS two wires inter- 
feiling each other at right angles at C, and moveable 
about the lame as a center, in manner above-mention- 
ed. Suppofe it be required to meafure the difference 
of right afcenfion and declination of two Ears, whole 
diffc rence of declination docs not exceed the extent cf 
the fcale of the micrometer, and the diftance of the 
meridians palling through the Ears does not exceed 
C W, the femidiameter of the field of the telefcope. 
Turn the wires E W, NS about, rill one of the Ears 
(the weEernmoE Ear will generally be beE for this 
purpofe) runs exacEly along the wire E VV, by the 
diurnal motion. Then feparate the two fegments of 
the divided obje6t-glafs to a convenient didance, and 
turn the micrometer round about, by means of the 
proper handle, till the two images of the fame Ear, 
formed by the two fegments of the objcft-glafs, pafs 
the horary wire N S at tlie fame inEanr. LaElv, 
partly by feparating the glaEes, and partly by touch- 
ing the rack-work fer'ews of the Eand of the telefcope, 
caufe the fouthernmoE image of the northernmoE 
Ear, and the northernmoE image of the fouthernmoE 
Ear, to appear both upon and run along the wire 
E W, as A,, B. The numbers Handing upon the Icalc 
^ of 
