DESCRIPTION OF PLATES. xix 



hoops A, B is of brass, the inside of steel : the weights C, D are screwed backwards 

 and forwards, in order to obtain the requisite degree of compensation. The weights 

 E, F are employed to regulate the mean rate of the watch, and G, H, and I, for 

 adjusting it to all positions with respect to the horizon. P. 154. 



Fig. 212. The compound plate A B rests on two supports, which are adjusted to 

 a proper distance by turning the double screw C, the flexure of the plate by heat 

 raising the bar D, which supports the pendulum, while its effective length is deter- 

 mined by a fixed clip, which is seen below the plate. P. 154. 



PLATE XVII. 



Fig. 213. A jack for raising weights by the alternate motions of a lever, the 

 clicks on each side being detained in the teeth of the ratchets by the assistance of the 

 springs in which they terminate, and which are connected together. P. 157. 



Fig. 214. The mode of supporting a tackle for raising stones in building; the 

 summit of the triangle, which is composed of three poles, being raised or lowered by 

 means of a rope and pullies. P. 159. 



Fig. 215. A method of raising weights obliquely, by means of a rope passing over 

 a pulley, which is drawn along horizontally. P. 159. 



Fig. 216. A B, a section of an inclined plane, belonging to the Duke of Bridg- 

 water's canal ; the boats are drawn into the locks at A, which are then filled with 

 water ; C is the plan of the windlass, by which the descending and ascending boats 

 are connected together, and which is turned by a winch ; D and E are the locks. 

 P. 159. 



Fig. 217. A crane, with an oblique walking wheel, for oxen or horses. The 

 wheel is taken from a mill of Leupold. P. 161. 



Fig. 218. A crane with a wheel and break like Mr. White's. The man walks at 

 any required distance from the axis of motion, and pushes forwards the lever A, which 

 moves the bar B C, connected to the same axis, and removes the break C D from the 

 circumference of the wheel. P. 161. 



Fig. 219. A lewis, for raising stones. P. 161. 



Fig. 220. When the centre of gravity A is twice as far from one of the porters B, 

 as from the other C, the first bears one third of the weight, the other two thirds. 

 P. 162. 



Fig. 221. When the centre of gravity A is above the line joining the points of 

 support B, C, the load is divided in the ratio of the segments CD, B D, terminated 

 by the vertical line A D ; but it may be supported by two equal forces in the direc- 

 tions BE, C F, found by making G H equal to B G, and joining C H ; the angle 

 G B E being equal to G H F ; the forces and the weight may then be represented by 

 the lines C I, I K, and C K. P. 162. 



Fig. 222. A roller with two wheels fixed on its ends, by means of which the slab 

 resting on it may be moved to a considerable distance without leaving the roller 

 behind. P. 164. 



Fig. 223. Mr. Garnet's rollers for diminishing friction : their axes being loosely 

 connected by a ring, in order to keep them in their places. P. 164. 



c2 



