64 PROPOSED CORRECTION TO THE ASSUMED 
and 10h. 4m. 5005s. E. Combining the observations of the two 
years, he got for the resulting longitude—10h. 4m. 45°39s. E. 
from observations of the first limb, and 10h. 4m. 49°26s. E. from 
observations of the second limb ; or, as the final result, 10h. 4m. 
32s. E. is value differs only 1°58s. from the Rev. W. Scott’s, 
before stated. The discussions by the Rev. W. Scott and Mr. 
Stone, so far as I am aware of, are the only ones that have yet 
appeared.* I believe, however, that the method o moon-culmi- 
nations must yield in point of accuracy to that founded on lunar 
occultations of stars. While the Greenwich corrections to the 
moon’s tabular places in the meridian depend, of course, upon 
observations made by thoroughly practised observers with the 
great transit circle, whose telescope is an instrument of about 8 
inches aperture and nearly 12 feet focal length, and a clock of 
the highest class, the transits at Sydney were observed with a 
telescope of only 3} inches aperture and 62 inches focal length, 
with a clock of not first-rate quality. e determinations of 
right ascension at Sydney cannot, therefore, compare in point of 
accuracy with those made at Greenwich. What we want here, 
therefore, are observations which are more nearly comparable in 
precision with those made at Greenwich, and these, I believe, are 
to be found in observations of lunar occultations of stars. An 
occultation, it is well known, ean be observed within a fraction 
of a second of time, and if the moon’s dise were a ect. cifcle, 
and the tabular elements could only admit of being corrected at 
Greenwich wit e same degree of accuracy, the resulting 
longitude would be correct within a second of time. Professor 
policy of the American Commission for the observation of t 
transit of Venus to depend on occultations, rather than upon 
* The principal portion of the i i iously to 
f ; preceding r was written previously 
the last meeting of the Astronomical Section 3 the Royal Society, henoe there 
is no mention made of the result recently arrived at for longitude by the 
resent Government Astronomer. At that meeti d by him 
on numerous moon-culminations observed by himself in the years 1863 
ibe 1872, 1873, and 1874. He gives for he : oie a ‘le 10h. 4m. 
81s. a (see Herald, May 7th, 1878), which differs only 2°57 
see ge the occultation observations. It must be remembered, however, 
rap w moon-eulminations referred to have been observed by means of 
old transit circle of 33 inches aperture. a 
