92 FERGUSON'S LECTURES. 



The great rope goes between two upright rollers i 

 and k, which turn upon gudgeons in the fixed beams f 

 and g ; and as the gib is turned towards either side, the 

 rope bends upon the roller next that side. Were it not 

 for these rollers, the gib would be quite unmanageable ; 

 for the moment it were turned ever so little towards any 

 side, the weight K would begin to descend, because the 

 rope would be shortened between the pulley / and axis 

 G ,- and so the gib would be pulled violently to that side, 

 and either be broken to pieces, or break every thing that 

 came in its way. These rollers must be placed so, that 

 the sides of them, round which the rope bends, may 

 keep the middle of the bended part directly even with 

 the center of the hole in which the upper gudgeon of 

 the gib turns in the beam f. The truer these rollers are 

 placed, the easier the gib is managed, and the less apt 

 to swing either way by the force of the weight K. 



A ratchet-wheel Q is fixed upon the axis D, near the 

 trundle jE; and into this wheel the catch or click R falls. 

 This hinders the machinery from running back by the 

 weight of the burden K, if the man who raises it should 

 happen to be careless, and so leave off working at the 

 winch A sooner than he ought to do. 



When the burden K is raised to its proper height 

 from the ship, and brought over the quay by turning 

 the gib about, it is let down gently upon the quay, or 

 into a cart standing thereon, in the following manner : 

 A man takes hold of the rope 1 1 (which goes over the 

 pulley v, and is tied to a hook at S in the catch R) and 

 so disengages the catch from the ratchet-wheel Q; and 

 then, the man at the winch A turns it backward, and 

 lets down the weight K. But if the weight pulls too 

 hard against this man, another lays hold of the handle 

 V t and by pulling it downward, draws the gripe U close 

 to the wheel Y, which, by rubbing hard against the 

 gripe, hinders the too quick descent of the weight ; and 



