106 i^KUuSUIS S LECTURES. 



follower G takes hold of the ropes a, a, which raise the 

 end of the lever L, and cause its end N to descend and 

 press down the forcing bar 5 upon the little lever 2, which 

 by pulling down the bait Y, unlocks the drum C from 

 the great wheel B ; and then, the follower, being at liberty, 

 comes down by its own weight to the ram ; and the low- 

 er ends of the tongs slip over the staple R, and the 

 weight of their heads causes them to fall o utward, and 

 shuts upon it. Then the weight 4 pushes up the bolt 

 Finto the drum, which locks it to the great wheel, and 

 so the ram is drawn up as before. 



As the follower comes down, it causes the drum to 

 turn backward, and unwinds the rope from it, whilst 

 the horses, great wheel, trundle, and fly, go on with an 

 uninterupted motion : and as the drum is turning back- 

 ward, the counterpoise W is drawn up, and its rope T 

 wound upon the spiral fusy D. 



There are several holes in the under side of the drum, 

 and the bolt Y always takes the first one that it finds 

 when the drum stops by the falling of the follower upon 

 the ram ; until which stoppage, the bolt has not time to 

 slip into any of the holes. 



This engine was placed upon a barge on the water, 

 and so was easily conveyed to any place desired. I 

 never had the good fortune to see it, but drew this 

 figure from a model which I made from a print of it ; 

 being not quite satisfied with the view which the print 

 gives. I have been told that the ram was a ton weight, 

 and that the guides b b, between which it was drawn up 

 and let fall down, were 30 feet high. I suppose the 

 great wheel might have had 100 cogs, and the trundle 

 ten staves or rounds ; so that the fly would make ten 

 revolutions for one of the great wheel. 4 * 



Note 42. Engines of this description, although much simplified. 

 are now very generally employed ; not merely in the construction of 

 bridges and other branches of hydraulic architecture, but also in the 

 manufacture of buttons, and other purposes connected with the arts. 



