C 168 3 
of either kind ; and this is (till more likely to happen in 
the obfervations of Venus, which will be chiefly in the 
day light ; 1 beg leave to offer (what to me is) a new 
method of obiervation out of the meridian ; and 
which, though I efteem it not equal to micrometer 
obfervations of either kind, I apprehend will fall fo 
little fhort thereof, and prove lo much fuperior to 
any other method now in practice in thefe cafes, 
that I hope I fhall on this occaflon be excufed, in 
giving a particular defeription thereof: but, as it is a 
general method of obferving out of the meridian, I 
ihall referve it by way of appendix. 
In the next obfervation of Mars, it has been dated, 
that, in the meridian obfervations alone, the menflrual 
parallax, according to the (mailed eflimation, maybe 
expedited to amount to 31" in longitude; which; 
turned into right afeenfion, will make about 2" of 
time : now, if it may be allowed, that a well-prac- 
tifed obferver can take the time of a tranfit to ~ part 
of a fecond, over a Angle wire, if he has three 
wires, or more, as ufual, the mean of the three fhould 
be within ~ r part of a fecond ; or within part of 
the whole quantity in queftion : it is however a mat- 
ter of chance, whether the mean of three may or 
may not be within 4. part of the whole ; and as equal 
errors may be committed in the obfervations of 
the tranlitsof the flars, wherewith the right afeenflons 
of the planets in queftion are compared ; which it is 
an equal chance, whether they tend to corredf or 
increafe the errors committed in the former ; yet if, 
as has already been propofed, the obfervations are con- 
tinued for two or three months, inflead of one ; and 
obfervations, taken the day preceding and fubfequent 
to 
