for elevating and depressing Water. 325 



that the curve may be so constructed as to counteract the 

 inclination of the load on the plane under any irregular ope- 

 ration : aud, beiiip- so constructed, the load will in all cases be 

 nearly as easily moved as if always running on a level surface. 

 I am, sir, 

 Your most obedient humble servant, 



Woburn, April 23, 1S05. ROBERT SALMON. 



Charles Taylor, Esq. 



In fig. 3. (Plate VIII.) C is supposed to represent a canal 

 lock of the common construction, whose lower gates i, i, 

 open towards or into ihe lock, and its upper gates k, k, 

 open towards the upper or higher level of the canal ; D is a 

 hollow caisson., or water-tight chest, which is fitted to a 

 walled chamber or side-lock, so as to move freely up and 

 down therein ; i is an opening;, which forms a connection 

 between the lock and the caisson-chamber, and which can 

 be clostd by a shuttle fitted thereto, when required. Four 

 standards e,e,e,e, are firmly fixed on the ground and walls 

 of the lock and chamber; and four posts c, c, c, c, are fixed 

 in the four corners of the caisson ; on each alternate pair of 

 these standards and posts the fram.es a and b rest, as on so 

 many fulcrums, or moveable joints ; the frame b (fig. 1 

 and 2.) has two straight parallel bars of thin iron fixed 

 thereto, and standing up above the same; the frame a has 

 two similar bars affixed to it, except that the top edges of 

 these are hollowed into a curve, as shown in the figures. 

 B A is a carriage loaded with two heavy leaden weights, and 

 resting on four low brass wheels, having grooves in then- 

 circumferences, like sash-pulleys, to receive the iron bars 

 upon the frame's b and a, so that the carriage can be drawn 

 along upon them ; the distance of the axles of their wheels 

 is such, that when the wheels at B rest on the frame over 

 two of the posts c, c, the w heels at A shall at the same time 

 rest over the other two posls e, c, as shown in fig. 1 ; and 

 when the wheels at B rest over two of the standards c,c } the 

 wheels at A shall at the same lime rest over the other two 

 Standards v,c, in fig. 2. In order to work the model, the 

 Y 3 carriage 



