266 Geographical Position of the 
ten years, only four solar eclipses have been visible in Van 
Diemen’s Island, two of which were obtained and carefully 
observed. They are, however, tolerably certain in their 
deductions, when observed under favourable circumstances. 
Eclipses of the Moon afford but unsatisfactory results, 
on account of the indistinctness of the border of the earth's 
shadow ; and there are so many practical difficulties in the 
way of obtaining the occultations of the fixed stars by the 
Moon, arising from the long and tedious calculations re- 
quisite to ascertain whether a certain star will be occulted 
or not, that neither has been employed. 
In the observations of the “ Moon Culminating Stars,” 
an excellent Transit instrument, by Troughton and Simms, 
of 30 inches focal length and 8 inches aperture, was em- 
ployed, fixed upon a solid pedestal of stone, well imbedded. 
The stand of the instrument, which supports the Y’s, is of 
cast iron, and is in itself so weighty, that great steadiness 
was obtained, and the adjustments for azimuth and inclination 
required to be rarely made. Whenever the Moon's transit 
was obtained, observations for the deviation were made 
with pairs of high and low stars, taken principally from the 
Ast. Soc. Catalogue. The error in collimation was inap- 
preciable, and four stars were always observed with the Moon, 
when practicable; and the indications of the riding level 
(which is graduated to 1-’0) were read in every case with 
the observations, when the altitude was low enough for the 
level to be placed on the pivots of the axis, without dis- 
turbing the position of the telescope. 
The observations of the eclipses of Jupiter's Satellites and 
the Sun were made with a telescope by Jones, having a 
focal length of 43 inches and an aperture of 2°75 in. The 
eye-piece employed with the Sun was a direct one—with 
Jupiter’s Satellites an inverted one—of much greater power 
