600 PHILOSOPHICAL TRANSACTIONS. [aNNO 1795. 



the circular arches, a kind of temporary props, that could be easily removed, 

 one at a time, and were narrow enough to pass through the hoops while they 

 advanced; and as soon as a ring was in its proper place, no further support be- 

 came necessary. In this manner we secured the cylindrical form of the tube; 

 and as soon as this was accomplished, we had every thing removed from within 

 and without, and began to give the tube' 3 or 4 good coats of paint, inside as 

 well as outside; in order to secure it against the damp air, to which it was soon 

 to be exposed. 



As the tube was now much lighter than it would be hereafter, we transported 

 it into my garden in the following manner. Many short poles, about 3 feet long 

 each, were joined two and two by a piece of coarse cloth, such as is used for 

 sacks, about 7 feet long each. This, being fastened in the middle, left at each 

 end part of the pole to serve as a handle for a person to hold by. The cloth of 

 one of these being put under the tube, there was left one of the poles at each 

 side, and 4 men taking hold of the ends of the poles, might conveniently assist 

 in carrying the tube. When six sets of these were put under the tube, it 

 was with great facility lifted up by 24 men, who carried it through an opening 

 made at one end of the barn. The inclosure of part of my garden having 

 also been taken down, with some trees that were in our way, it was safely 

 landed on the grass-plot; where a proper apparatus of circular blocks was put 

 under to receive it. While it remained in this state, we prepared every thing for 

 its reception, and afterwards moved it into its place, and supported it in an 

 horizontal situation. 



Passing over a number of contrivances for raising and supporting the tube, 

 fixing the mirror in its place, moving the tube in different directions, and 

 various other contrivances, Dr. H. adds, by the assistance of these 2 motions, 

 the telescope may be set to any altitude, up to the very zenith ; and in order to 

 have the direction of it at command, a foot quadrant of Mr. Bird's is fixed at 

 the west side of the tube, near the end of it, inclosed in an iron case ; on the 

 top of which is also planted a finder, or night-glass, about 21 inches long, with 

 cross wires in the focus. The divisions of the quadrant are indicated by a spirit- 

 level, instead of a plumb-line. The axle, which turns the first pinion of the 

 mechanism for moving the point of support, carries a pallet. This gives motion 

 to a small wheel with studs, contained in a machine fixed to the frame of the 

 great wheel-work, and inclosed in a little box. The wheel with the studs 

 carries a perpetual screw, which moves a central wheel, on the axis of 

 which is fixed an index-hand, that passes over a gradulated plate of 140 divisions. 

 Each of these divisions answers to 4 turns of the handle; and they are large 

 enough that a 4th part of one of them may be distinguished. In this manner 

 the hand will point out how many turns of the handle have been made to move 

 the telescope from its most backward point of support to the most forward. 



