60 :><)-TON I;IVKT<>\ MA KINK. 



position, and to, as nearly as possible, keep it there. To 

 raise the right-hand end of the beam the lower end of the 

 specimen must be moved in a downward direction, and this 

 is effected by slightly opening the hydraulic valve which 

 admits the high-pressure water above the piston. The 

 piston is thus moved downwards, it carries with it the 

 lower end of the specimen, and the beam is raised to its 

 normal position. 



During a tensile test, therefore, especially if the material 

 tested be of a ductile nature, the machine has to perform 

 two distinct functions namely, that of applying and 

 measuring the loads, and, at the same time, taking up the 

 stretch ot the specimen in such a way that the end of the 

 specimen at which the load-weighing apparatus is attached 

 does not, to any appreciable extent, alter its position with 

 respect to the body of the machine. 



These two functions ar$ under the control of the 

 operator who is performing the test. He regulates the loads 

 either by means of the hand wheel rotating the 

 screw, or by means of a belt lever which causes the 

 same thing to be done by poAver; and he takes up the 

 stretch or strain by allowing or causing water under 

 pressure to flow into the straining cylinder. 



It will be noticed that on Fig. 21 is a small piece of 

 apparatus to the right of the standard of the machine. 

 This is Mr. Wicksteed's appliance used for the production 

 of autographic diagrams, and will be described later. 



Fig. 22 shows a general perspective view of the same 

 machine as that represented on Fig. 21. 



27. Methods of Applying the Hydraulic Power. In 

 the Buckton-Wicksteed machines now in use, there are, so 

 far as the author is aware, three different ways in which the 

 water under pressure is supplied to the straining cylinder. 

 These are, first, by means of a set of power-driven pumps 

 working with an accumulator; secondly, by means of an 

 intensifier ; and lastly, by what is called a quiet com- 

 pressor. These will be briefly described. 



28. Pumps and Accumulators. In this arrangement 

 water is drawn from a supply tank, and pumped at a high 

 pressure into the ram cylinder of an ordinary hydraulic 

 accumulator, which is so loaded as to maintain the required 

 pressure. From the accumulator the water is delivered to 

 the ram cylinder of the machine, and the supply regulated 

 by means of a valve manipulated by the operator. When 

 a test has been completed, an exhaust valve is opened and 



