LONGITUDE OF THE SYDNEY ODSERVATORY. 65 
thought it would be desirable to investigate the problem and lay 
the results before our Socie ety. If the To ngitude of any point in 
the Colony could only be accurately determined in this way, that 
of any other point could readily be determined by exch: angen a 
time signals with the electric telegraph. I thought at firs 
include the observations ns ee eclipses in my" inv peli 
but as these phenomena cannot be observed with the same 
deere as an feckulte tion «% conxidwrsl it ailvisable to reject 
em. Iam not aware if any occultations have been _systemati- 
a observed at host During the period 1863-1877, however, 
hay ded i observing one hundred and aay tne of 
ndsor. By f 
stars so observed have not yet been catalogued with sufficient 
accuracy, and have been observed only at the dark limb during 
the first semi-lunation. I have selected twelve stars for the 
a ore of the longitude of my observ niet we ed previously 
to se for which I am’ enabled t the Greenwich 
hecotinnee the moon’s tabular aya They have all been 
observed at the dark limb during the first semi-lunation. Their 
cliff bourn ) 
considered fixed with almost absolute accuracy. For the compu- 
tations I have adopted—33°36' 28°9" as the astronomical latitude of 
my observatory. This value rests upon ninety-three prime vertical 
observations with a transit instrument of 2:1 inches aperture an 
20 inches focal length, of stars culminating within 39’ of the zenith, 
whose positions have been determined in the Southern Obser- 
vatories of Sydney, Melbourne, and Williamstown. Fifty-nine 
plete observation. Re} eting only one observation for discordance, 
I obtained the following results or each class of observations :— 
Mean of 59 observations on a centre wire—33°36’ 288” 
side wire ...—33°36’ 29:2” 
The mean result, as "before "salad: Mery ak —33°36’ 28:9” 
With the exception of the discordant observation before m 
tioned to have been rejected, the extremes of the individual 
results oe arse 20°9,”—33°36' 37-7”. It will therefore be seen 
that any further c orrection to the latitude must be very small, 
and not likely > emonat ls = affect the apy longitude. 
Adopting now Bessel’s of the squares of earth’s 
2 
semni-axes, oF ee 9933254, : got 83°25’ 53:0” and sdeee 
aa latitude and the log. earth-radius corre 
tony ik dn 
sponding 
tory. With these constants, corrections of the moon’s 
Hae gamete éncluded from observations at ese h, and an 
ig 
e 
