OF CRANES. 93 



not only so, but even stops it at any time, if required. LECT. 

 By this means, heavy goods may be either raised or let ^x-v-^. 

 down at pleasure, without any danger of hurting the 

 men who work the engine. 



When part of the goods are craned up, and the rope 

 is to be let down for more, the catch R is first disen- 

 gaged from the ratchet-wheel Q, by pulling the cord t ; 

 then the handle q is turned half round backward, which, 

 by the crank n n in the piece o, pulls down the frame 

 h between the guides m and m (in which it slides in a 

 groove) and so disengages the trundle B from the wheel 

 C : and then, the heavy hook /3 at the end of the rope H 

 descends by its own weight, and turns back the great 

 wheel .Fwith its trundle E, and the wheel C; and this 

 last wheel acts like a fly against the wheel F and hook 

 /3 ; and so hinders it from going down too quick ; whilst 

 the weight X keeps up the gripe U from rubbing 

 against the wheel Y, by means of a cord going from the 

 weight, over the pulley w to the hook W in the gripe ; 

 so that the gripe never touches the wheel, unless it be 

 pulled down by the handle V. 



When the crane is to be set at work again, for draw- 

 ing up another burden, the handle g is turned half round 

 forwards ; which by the crank n n, raises up the frame 

 h, and causes the trundle B to lay hold of the wheel C; 

 and then, by turning the winch A, the burden of goods 

 K is drawn up as before. 



The crank n n turns pretty stiff in the mortise near 

 o, and stops against the farther end of it when it has 

 got just a little beyond the perpendicular ; so that it 

 can never come back of itself: and therefore, the 

 trundle B can never come away from the wheel C, until 

 the handle q be turned half round, backwards. 



The great rope runs upon rollers in the lever L M, 

 which keeps it from bending between the axle at G and 

 the pulley I. This lever turns upon the axis N by means 



