148 Automatic Control of the Flow of Gas 



the entire frame shifts to the left, owing to the elasticity of the 

 Springs that extend between a and d] and a decompression of the 

 lumen of the tube is thus effected. By puUing the frame from the 

 opposite side, a and h are brought temporarily close together, com- 

 pressing the lumen of the tube. This compression lasts only so long, 

 however, as the pull is exerted upon the frame at / ; f or, as soon as 

 the pull is released, the frame strikes back to its former position by 

 the action of the Springs, until it is checked by the catch m. 



It is clear, from this description, that a current of gas under a 

 pressure of, say, 2 to 4 Ib. may be made to flow at a minimum rate, 

 regulating this with the set screws; and, if necessary, the flow may 

 be temporarily increased to its maximum capacity or temporarily 

 cut off. It is also clear, of course, that if the set screws are adjusted 

 so as to close off the lumen of the tube only two possibilities will be 

 open; namely, the maximum delivery of gas, alternating with com- 

 plete cessation of the flow. According to the special requirements 

 of the case, either the three-phase or the two-phase regulation may 

 be employed. 



The electromagnets which control the movements of the frame, 

 •^y f> 9> ^} are mounted, together with the " pinch-cock," on a brass 

 plate, as may be seen from Fig. i and 2. The construction of these 

 electromagnets is somewhat peculiar and is calculated to obtain a 

 maximum efficiency. The magnet consists of an L-shaped iron base, 

 p, to which a Y^ inch plate, r, also of iron, is pivoted so that it de- 

 scribes an are in moving from the vertical to the horizontal position. 

 A stout iron axis tapering at one end is firmly fixed to the vertical 

 part of the base, and on this axis is set a spool bearing numerous 

 windings of fine wire. The free tapering end of the axis fits into 

 a pit of similar shape drilled into the movable iron plate. When an 

 electric current is sent through the spool, the plate is very powerfully 

 attracted to the axis and, owing to the fact that the pointed end 

 protrudes into the plate, a strong pull is exerted from the start. The 

 position of the movable plates from the frame, e, f, g, h, the ampli- 

 tude of the pull, as well as the return to the original position when 

 the electric current is discontinued, are secured by means of screws 

 and Springs, as is shown in Fig. i and 2. Fach of the iron plates, 

 r, bears upon its free surface a yoke-like structure, s, by means of 



