742 TRUEBLOOD. 



union is thus obtained. This method of attachment is also due to 

 Prof. Davis and is very satisfactory. It was deemed advisable to 

 make the joint steam-tight by the use of bakelite varnish, bakelized 

 under pressure according to standard methods of treating this material. 

 Bakelite varnish has also been depended upon for mechanical union 

 in some plugs, the copper plating being dispensed with; but the 

 results are not so satisfactory as when the plating method is used. 



No internal lagging whatever was used with this type of plug case; 

 but the case was provided with a galvanized sheet iron container (not 

 shown) resembling a small coal scuttle. The plug case being placed 

 inside the container, the space remaining could be filled with poplox, 

 giving an average thickness of insulation of perhaps two inches between 

 the plug case and the oil. The container was equipped with an oil 

 tight top, so that it, with the plug and poplox inside, could be com- 

 pletely immersed in the oil bath. Experiments were conducted, (i) 

 without the container; (ii) with the container, but no poplox, the 

 cover being omitted and the container immersed until its upper edge 

 was flush with the sm^ace of the oil; (iii) with the container filled 

 with poplox, cover omitted, immersion as in (ii); (iv) with the con- 

 tainer filled with poplox, covered and completely immersed. 



c. The U-type of radial flow plug case. 



This name is used merely for convenience. The plug case was 

 simply the axial flow case of Fig. 1, with certain minor changes neces- 

 sary for adaptation to radial flow work. The plug was located in the 

 low side tube, T' of Fig. 1, and was supported by means of a special 

 flange which made possible complete internal lagging, of a thickness 

 roughly | inch at the open end of the plug and rather less than | inch 

 elsewhere. The end-lagging was asbestos wood (a commercial 

 product consisting of asbestos fibres with a binding of portland 

 cement) ; the other lagging, separating the plug from the steel wall of 

 the tube T', was of talc, as in Fig. 1. It may be mentioned that 

 asbestos wood is a much more efficient lagging material than either 

 talc or soapstone. 



The block S of Fig. 1 was replaced by a block having a single large 

 hole at the place at which the heating coil is shown in Fig. 1 and a 

 similar hole at the corresponding place on the low side. The block 

 corresponding to S' had a half-inch channel, with baffling and mixing 

 chambers at each end. 



Only a few runs were made with this type of plug case, which was 



