Magnetic Observatory, Hobart Town. 265 
I propose to lay before the Society the various methods 
of observation which have been pursued, and the results 
which have been obtained, and although the details must 
necessarily partake of a technical character, I trust the 
object in view will be deemed of general interest. 
The method of determining the difference of longitude 
between any two given points on the earth’s surface has 
always been considered to be one of the most difficult 
problems in practical astronomy, and has long engaged 
the attention of the most eminent astronomers and mathe- 
maticians. Where the distance between any two given 
points is not very great, their difference of meridian may 
be determined with considerable accuracy by means of chro- 
nometers conveyed from one place to another; and I have 
availed myself of the well-ascertained position of the 
Observatory at Paramatta, in New South Wales, by Sir 
Thomas Brisbane, for determining the longitude of the 
Hobart Town Observatory by this method. 
The other modes of observation of celestial phenomena, 
to which recourse must be had for the solution of the 
problem, are— 
Ist. Meridional Transits of the Moon, compared with 
certain Stars previously agreed on, and called 
“ Moon Culminating Stars.” 
2nd. Eclipses of the Sun. 
3rd. Eclipses of the Moon. 
Ath. Eclipses of the Satellites of Jupiter. 
5th. Occultations of the Fixed Stars by the Moon. 
6th. Lunar Distances. 
Of these six methods I have employed four, vz., the Ist, 
2nd, 4th, and 6th; but Eclipses of the Sun are of so rare 
occurrence, -and so limited in extent, that, during the last 
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