A REFRACTING TELESCOPE WITH A FLUID CONCAVE LENS. 41 
The front socket is different from the others, as it forms one piece with an 
upright socket which carries a strong oaken stancheon, to the upper part of 
which the machinery described below is attached. This stancheon having to 
support a great part of the weight of the telescope, at least in some positions 
of the latter, is strongly braced back by an oaken beam to the opposite ledge 
of the triangular base. 
The principal upright part of the stand are two oaken bars framed or 
secured together in the middle and on the top, and turning on strong iron bolts 
in two cast-iron ears below ; about which bolts this part, called the swinging 
frame, has a motion. These bars are cased on the outside by grain-cut oaken 
facings, and thus form two grooves in which an interior frame slides freely. This 
frame, on one of its interior sides carries a fixed racket, not seen in the plate, 
its whole length ; and between the two connecting pieces in the centre of the 
swinging frame, is a spring pall which catches each tooth of the racket as 
it passes, being intended to prevent any accident in case of the breaking of 
a rope when the telescope is elevated. 
To the pall is attached a string which descends near the upright stancheon; 
and when it is necessary to let down the telescope, this string is pulled by one 
hand, and the other having hold of the proper apparatus, the descending mo- 
tion takes place in the most gentle and easy manner possible. 
On the upper part of the front upright stancheon are two strong wrought- 
iron checks, terminating about two inches above it, having two circular holes 
f ths of an inch diameter, in which turns, as in two collars, a strong iron screw 
inch in diameter, having two threads to the inch : on this works a strong- 
brass nut with corresponding threads, and to this nut the frame which carries 
the telescope, and is called the bearing frame, is properly united, turning on a 
moveable joint near the screw. The screw is turned by four long cross han- 
dles, seen in the plate, by means of which the azimuth motion of a star or 
planet is followed. The length of the screw is about 1 1 inches and of the nut 
3 inches, leaving a motion of 8 inches, which enables a star to be followed 
for a considerable time without moving the stand : the turning point on which 
this motion of the frame takes place, is exactly in the centre of the upper part 
of the interior or sliding frame, where a pin is fixed, which traverses in a 
parallel groove under the bearing frame ; but to prevent confusion this is not 
shown in the plate. 
MDCCCXXIX. 
G 
