( 159 ) 



The latter is represented scliemaiically by fig. 1 on PL I and 

 hardly requires fuitlier explanation. The compressed hydrogen goes 

 successively tlirongh the regenerator coils D^, D^, D^, D.^, C, B, A. 

 B is immersed partially in a bath of liquid air which, being admitted 

 through P, evaporates at a very low pressure; D^, D^, 6' and A 

 are surrounded by hydrogen expanding at the cock M, and D^ and D^ 

 by the \'apours from the airbath in F. As, however, we can dispose 

 of more liquid air than we want for a suiHicient cooling of the admitted 

 hydrogen, and the \acuum j)ump (comp. Comm. N". 83, March '03) 

 has a greater capacity than is required to draw off the evaporating 

 air^) at reduced pressure, even when we sacrifice the regenerator 

 working of the spirals D^, D^, D^ and D^, wq have for simplicity 

 not yet added the double forecooling regenerator jD, by means 

 of which a large quantity of liquid air will be economized, and hence 

 the apparatus consists only of one forecooling regenerator C, the 

 refrigerator F with cooling spiral B and the principal regenerator 

 A in the vacuum glass E with a collecting vessel L, placed in 

 the case V, which forms one complete whole with the case U. 



b. The principal regenerator, PI. I fig. 2, consists of 4 windings 

 of copper tubing, 2.4 m.m. in internal diameter and 3.8 m.m. in external 

 diameter, wound close to each other and then pushed together, indicated 

 by A^, A^, A^ and A^, (number of layers 81 ; length of each tube 

 20 j\I.). As in the ethylene regenerator (Comm. N". 14, Dec. '94, and 

 description of Mathias ^), fig. IF) and in the methyl chloride regenerator 

 (Comm. N°. 87, ^larch '04, PL I) the windings are w^ound from the 

 centre of the cylinder to the circumference and again from the circum- 

 ference to the centre round the cock-carrying tube j\J^, and are enve- 

 loped together in fiannel and fit the vacuum glass F^ (the inner 

 and outer walls are marked with F^^ and F^J. Thence the liquid 

 hydrogen flows at F^^ into the collecting vessel Lq. At M^^ the 

 four coils are united to one channel which (comp. cock T in fig. 3 

 of Mathias' description I.e.) is shut by the pivot point J/jj moved 

 by the handle j\l^^. The packing 31^ hermetically closes the tube 

 M^ at the top, where it is not exposed to cooling (comp. Mathias' 

 description I.e.). The hydrogen escapes at the side exactly as at 

 the ethylene cock L, fig. 2 in Mathias' description I.e., through 6 

 openings 31^^ and is prevented from rising or circulating by the 

 screens M^^ and J/^g. 



c. The new-silver refrigerator case F^ is suspended in the new- 



1) When using oxygen we might avail ourselves of cooling clown to a lower 

 temperature, which then must be carried out in two steps (comp. § 46). 

 -) Le laboratoire cryogène de Leyde, Rev. Gen. d. Sc. Avril 1896. 



