BRIDGMAN. — HIGH PRESSURE EXPERIMENTING. 



643 



is to drill and tap a convenient sized hole at the upper end of the 

 cylinder, say for a 10-32 thread, j of an inch long, and then to screw 

 tightly into the tapped hole a carefully cut screw, across the threads 

 of which (that is, parallel to the axis) a fine scratch has been made. 

 This scratch is the channel by which the transmitting fluid gains 

 access to the interior of the cylinder; its size may be regulated at 

 pleasure by varying the size of the scratch. The screw may be made 

 of soft tool steel, since the pressure it has to withstand is not high, 

 thus permitting the end projecting into the cylinder to be reamed off. 

 The use of a by-pass necessitates the use of an auxiliary pump giving 

 several thousand kilograms. I have found it convenient to use a 

 second pump of the Geneva type,coupled to 

 an intensifier of readily suggested design, 

 stepping up the pressure four times. i: | 



Plugs. 



In adapting pieces of apparatus to new 

 uses it will often be necessary to plug holes 

 previously used for connections. This may 

 be done with a plug packed according to the 

 simple method of rubber washers used for 

 the connecting pipes at low pressures (see 

 Figure 12). If the stem and the head. A, 

 are turned from one piece of Krupp Chrome 

 Nickel steel and hardened, the "pinching- 

 off " effect will seldom be troublesome. One 

 should realize, however, that the " pinching- 

 off" effect is treacherous, and likely to come 

 at the most unexpected times. All parts 

 liable to this effect should either be shielded, 

 or else they should be pointed in such a 

 direction that they can do no damage if 

 projected by an explosion. 



Figure 12. The plug 

 for closing holes against 

 high pressures. The plug 

 A is packed with a rubber 

 washer B, a soft steel 

 washer D cupped and 

 filled with solder at C, 

 and the hardened washer 

 E. The scale of the dia- 

 gram is f actual size. 



Jefferson Physical Laboratory, 

 Harvard University, Cambridge, Mass. 



