Serghis Morgidis 



147 



Figs. I and 2. The "pinch-cock" consists of a movable frame 

 ^i fj 9> ^h supported by two uprights, c and d, and two brass bars, 

 a and b. The ft^rmer is permanently fixed to the parallel rods, g and 

 h, by means of pins. The latter, b, can be shifted freely over the 

 rods, g and hj and is attached to j, which can be moved either way 

 in a horizontal plane by means of the set screws k and /. A rubber 

 tube, held in position by two supports, n and Oj as can be seen in 

 Fig. 2, passes between the bars a and bj the inner faces of which 



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are rounded off so as not to injure the rubber tube. The lumen of 

 the tube may be left entirely open, or it may be entirely closed, by 

 varying the distance between the bars, a and b, with the set screws. 

 In this way a permanent flow of gas at any desired rate can be 

 secured. A further increase in the rate of delivery, or a complete 

 shutting off of the current, is effected by shifting the frame, 

 ^, f, 9, h^ to the right or left. These movements are controlled by 

 oppositely-placed powerful electromagnets. When the opening be- 

 tween the horizontal bars, a and b, has been once adjusted, it re- 

 mains unchanged because on the one hand the set screws hold bar 

 b securely fixed, while bar a, which is attached to the frame, is 

 maintained in a fixed position by the catch in. By lifting that catch. 



