459 
Mr. Fallows’s catalogue of southern stars. 
nience for the necessary adjustments, and for illuminating 
the wires in the eye-piece. The focal length of the object- 
glass is about 19 % inches; its diameter 1,62 inches. The 
frame work is made of cast-iron ; the lower part of which is 
securely fastened to a block of stone, and this again strongly 
cemented to a firm brick pillar. The only defect which has 
yet been noticed in the frame is its liability to be affected 
by the variation of temperature. We obviate this in some 
measure, by constantly* levelling the axis of the telescope 
whenever an opportunity presents itself during a nights’ 
observations. 
The method of placing a transit in the plane of the meri- 
dian by a star near the Pole, so successfully employed in the 
northern, fails in the southern hemisphere, at least in small 
instruments; as I am not aware of any star within 12 degrees 
of the South Pole that can be classed higher than the fifth 
magnitude, and which of course can be very seldom observed 
at its superior and inferior culmination. I therefore deemed 
it advisable to take the transits of as many high and low 
Greenwich stars as possible, by which means, as is well 
known, the azimuthal error of the instruments may be easily 
ascertained, and the error of the clock to much nicety. Lest 
any change might take place in the position of the transit be- 
tween two successive nights’ observation (though correctly 
verified by a distant mark during the day), I determined the 
* It is worth while to remark, that the lamp for illuminating the wires ought to 
be lighted some time before the axis is levelled, and the instrument prepared for 
work, as the heat of the lamp communicating with the metallic frame will derange 
the level, and consequently render the observations of no use. This remark ap- 
plies only to portable transit instruments. 
