506 Johnston and Adams — Influence of Pressure on the 



the tube against its seat, and when this has once happened, it 

 remains tight indefinitely. Joints such as this have been sub- 

 jected to pressure up to 8,000 atmospheres, with both liquids 

 and gases ; when properly made, they show not the slightest 

 leak whatever. This type of connection possesses the follow- 

 ing distinct advantages over other types which have been used 

 for high pressure work; (1) it may be taken apart and put 

 together again repeatedly without impairing its efficiency ; 



(2) the joint is tight every time and thus there are avoided 

 the troublesome delays so common in high pressure work ;* 



(3) the danger of the whole joint blowing out at high pres- 

 sure — which may easily happen with ordinary butt joints — is 

 practically obviated, because of the smallness of the bearing 

 surface under all conditions. 



The tubing which has been used for all connections is of 

 mild steel, cold-drawn, 12 mm in outside diameter and 2 mm inside 

 diameter. It stands without rupture pressures of at least 8,000 

 atmospheres and can easily be bent or twisted if heated to 

 redness. 



We shall now proceed to describe the disposition of the 

 interior of the bomb, comprising the arrangements for heating, 

 and for measuring the temperature of, the charge of metal ; 

 the details are shown in fig. 3, which is drawn to scale. 



The electric furnace JJ (fig. 3) was made by wrapping a 

 thin sheet of asbestos paper around a copper tube 25 mm in diam- 

 eter, and winding on this " nichrome " wire (B and S No. 16 ; 

 l*3 mm in diameter), so that a coil 10 0ms long with 5 turns per 

 cm. was formed. The whole was inserted in a cylinder of 

 soapstone and the intervening space filled with " magnesite " 

 mixture. Soapstone cylinders, SS, afford heat insulation at the 

 ends of the furnace and also serve to fill up the space. One 

 terminal of the heating coil is " grounded " onto the bomb 

 through the brass ring I; the other end is led through the 

 lower soapstone plug 6\ the steel plug H, and out along a slot 

 cut in the top of the base plate B. The thermocouple wires 

 TT pass out through the top plug G. 



There are several ways in which good electrical connection 

 may be made between the inside and the outside of the bomb. 

 The method adopted in the present instance is as follows : a 

 hole about 12 mm in diameter is bored in the steel part through 

 which the wire is to pass and a cylinder of soapstone is turned 

 to fit this hole. Through the soapstone is drilled a hole of the 

 same diameter as the wire, which is then threaded through this 

 hole. The soapstone cylinder is inserted in the steel, and 



* In this connection we desire to express our indebtedness to Mr. Geo. F. 

 Nelson, to whom is principally due the success of this high-pressure joint, 

 and without whose mechanical skill and ingenuity our work would not have 

 been so far advanced. 



