Il6 THE SCIENTIFIC PAPERS OF 



midway between two carrying wheels over which the cable passed. 

 This construction, however, he thought was not so free in its action 

 as the arrangement shown in Fig. 5, which he had adopted and 

 had found completely successful, having the weighted pulley E 

 carried at the extremity of a lever F, so that it rested freely upon 

 the cable G ; the lever was loaded either by a weight H, or by 

 springs, the latter being preferable on account of their greater 

 steadiness of action. A scale attached to the lever showed at all 

 times the amount of strain upon the cable. 



In place of loading the friction brakes of the paying-out drum 

 by means of dead weights, as had previously been done, with the 

 addition on the Great Eastern of water cylinders to prevent undue 

 oscillation of. the weights, as described in the paper, he had adopted 

 a plan of loading the brakes which he thought had an advantage 

 in delicacy and certainty of action, by the use of a hydraulic 

 cylinder K, Figs. 5 and 6, loaded by a constant pressure of water 

 upon the piston, according to a suggestion originally made by 

 Professor Rankine and embodied in the design of the machinery 

 on the Dix Dfrerribre, The supply of water to the cylinder K was 

 maintained by the pump L, Fig. 5, driven constantly by a strap 

 from the shaft of the paying-out drum B ; and the water being 

 delivered along the pipe M communicated by the four-way cock I 

 with the top of the brake cylinder K, and passed up the rising 

 pipe N to the regulating valve J in the tank P, shown to a larger 

 scale in Fig. 7. The cylindrical casing of the valve J had four 

 V-shaped orifices, through which the water entering from the 

 pipe N escaped continuously into the external tank P, the rate of 

 escape being regulated by the position of the plunger J forming a 

 piston valve, which was loaded by a spring-balance Q, like an 

 ordinary safety valve. By this means a constant pressure was 

 maintained upon the top of the piston in the brake cylinder K, 

 and the load upon the brake R in paying out was thus readily 

 adjusted by screwing the spring-balance Q to the desired pressure ; 

 while at the same time the load upon the brake could never exceed 

 the maximum to which the spring-balance was adjusted. The 

 bottom of the brake cylinder K communicated by the four-way 

 cock I, and the exhaust pipe S with the tank P, but outside the 

 regulating valve J, so that the loading pressure was not conveyed 

 to the underside of the piston in the brake cylinder ; and in order 



