340 LIFT FOR CANALS. 



Machinery for blocks suspended from G He inactive in the cavity M N: the 



raising and contrary is the case when the trough is sunk. 



lowering boats _.. . - , , ,, . , , . 



upon canals Figure 2, is a section of the paddles, &c. of the upper level. 



without the y{ ay fti } the two perpendicular posts, containing the grooves, in 



of water as by w k* cn tne paddles CD slide. E F, small wheels at the 



Iwdtfc extremities of the posts 5 these, by rolling against other surfaces, 



contribute to regulate the ascending and descending motion of 



the trough. This is more distinctly seen in Figure 3, which is 



a profile of this part. 



G G, is the bottom of the canal, which projects a little beyond 

 its paddle, in order to fill up the space between the bottoms of 

 the two paddles, through which the water would otherwise 

 escape. The side spaces are filled up by square pieces of wood, 

 slide against strips of thick felt 3 thus rendering the whole com- 

 pletely water-tight. H, the small valve, by withdrawing 

 which the space between the paddles is filled with water. 



Figure 4. A plan of the situations of the paddles in the 

 grooves j which is sufficiently explained by comparative re- 

 ference to the other plates. 



Plate X. gives an elevation of the back of the machine, shew- 

 ing the eight wheels B 1, H 2, &c. the chains and rods D E F, 

 and the poise weights FG. Here also the external building is 

 removed, the centre wall alone remaining, in the interstices of 

 which the wheels revolve. 



The wheels No. 2 and 7, are toothed through twelve feet of 

 their circumference, and by means of these teeth, they are 

 acted upon by the wheel-work, which this plate also exhibits, 

 //are the two winches by which the pinions and wheels K K, 

 L L y M M, N N, O, are turned, and sufficient power is 

 thus acquired to move the wheels H H 5 this is effected by the 

 teeth of the pinions O 0> meeting those of H 2 and H J j these 

 two being connected by the common axis P P, their motions 

 necessarily correspond. On the sides of the weights F G, are 

 small projections, which slide into grooves, constructed in the 

 upright posts Q R. By means of these grooves, and the 

 regulating wheels E F, in figures 2 and 3, Plate II. the perpen- 

 dicular motion is rendered so perfectly true, that it was judged 

 unnecessary to give the wheels H H, any hollow j the chains 

 consequently move on flat surfaces, depending only on the 

 mathematical truth of the work. 



Tht 



