4 
Description of Mr. South's 
are cited in the following pages by the names of the five-feet 
and the seven-feet equatorials ; and a brief account of them, 
especially of the former, will neither be uninteresting to the 
practical astronomer, nor irrelevant to the objects of this 
communication. 
Five-feet Equatorial. 
The greatest part of this instrument, with regard to bulk, 
is constructed of tinned iron plate. Its characteristic qualities 
are great lightness, extreme steadiness, promptness in an- 
swering to its adjustments, and capability of retaining them. 
The instrument, as represented in fig. 1 , Plate I, is drawn 
on a scale of one-twelfth of the real dimensions. The view 
is taken at right angles to the plane of the declination circle. 
The polar axis is about ten feet and a half long. The 
lower end is a pivot attached to a cone, which, reckoning 
upwards, is about one-fourth of the whole length, the sides of 
this cone making with each other an angle of about fifty de- 
grees. The higher side of the cone, for about a foot of its 
length, is cut in a sloping direction, as seen in the figure, for 
the purpose of more conveniently observing in the vicinity of 
the pole. From the upper end of the cone, the polar axis 
branches into two parts, between which is room for the de- 
clination circle and the head of the observer: these two 
branches are again united at the top by an open frame of 
bell-metal, represented in fig. 2, to which the upper pivot 
is attached ; which frame, as well as the iron work which 
supports it, is so contrived, as to present the least possible 
surface to obstruct the telescope. For the same reason, the 
pivot at the top of the axis is made as small as possible, while 
that at the lower end is considerably larger. Both ends of 
