C 3 6 5 ] 
fet down by the fides of mod; of the obfervations were 
deduced, ex pr effing the number of minutes whicn 
the ftars pafied north or fouth of the moon s centre. 
They may be depended on to a minute, or two at moil, 
which is fufficientfor the reduction of the obfervations. 
To make the foregoing account of the method of 
obferving the moon’s horary parallaxes more clear, let 
AD BE, Tab. XXI. fig. i. reprefent the cell contain- 
ing the filver wires flretched in the focus of the 
neared eye-glafs of the telefcope, of which A B is 
the directing wire, M N, D E, OP, three wires 
perpendicular to A B reprefenting portions of horary 
circles j and, F G, H I, two other wires parallel to 
the directing wire A B, at the equal diflances, C Q, 
C R, on each fide, equal to io minutes. The femi- 
diameter of the field of the telefcope C A is 1.4 
minutes ; A is the eaftern fide of the field of view, 
B the weftern, D the fouthern, and E the northern 
fide. In order to adjaft the wire AB parallel to the 
equator, fo that M N, D E, O P, may reprefent 
horary circles, the ftar, whofe difference of right 
afcenfion from the moon is to be obferved, is brought 
by means of the fcrews to the interfedtion of the 
wires A B, D E, at the centre of the telefcope C, 
and when the ftar is near palling out of the telefcope 
at B, the cell AD BE is turned round, by means of 
a fcrew, till the Ear is again brought upon, and 
biffedted by the wire A B ; this being done, if the 
fcrew be turned to make the teleicope follow the ftar 
towards the weft, and the ftar be again brought to 
the interfedlion of the wires at C, it will be generally 
found to run exadtly along the wire C B, biffedled 
by it all the way from C to B ; which is then a proof 
that the wire A B is rightly adjufted ; but, if the ftar 
runs 
