lo Description of Mr. South's 
thought however, that the micrometer under consideration, 
was the first that had a position circle large enough to show 
distinctly minutes of a degree, by help of its verniers. This 
equatorial was designed to suit its first situation, viz. on 
the top of a house, where, to the north, higher buildings 
prevented any distant objects from being seen, and to the 
south, a smoky town presented almost as great an obstruc- 
tion. The instrument being elevated 50 feet above solid 
ground, it became absolutely necessary that a permanent 
mark should from time to time be consulted. This advan- 
tage only presented itself to the westward, where, at a pro- 
per distance, the ground was not much below the level of the 
instrument ; and to suit it to these circumstances, the decli- 
nation axis was converted into a telescope. The effect pro- 
duced by this, is similar to that of the Y level of the civil 
engineers, but with this difference : it is here required that 
each end of the axis should alternately be presented to the 
object, and that in reversed positions the telescope should 
have equal power. For these purposes, both ends have 
crossed wires, adjustable so as to be placed in the centres of 
their respective pivots. Exterior to the wires are placed ob- 
ject glasses of equal focal lengths, and an eye-glass, remov- 
able from one end to the other, completes the apparatus. 
The whole instrument having been adjusted astronomically, 
it was easy to build up a mark to the level of the axis, and 
also at right angles to the meridian, which afterwards be- 
came a substitute for a meridian mark, and also afforded an 
excellent mean for adjusting the reading microscopes of the 
hour circle. 
The instrument bears no maker's name. The whole 
