( 168 ) 



cock M must be tightened a little more in order to keep the pressure 

 within the same limits. 



When liquid hydrogen collects in L rime is seen on the tube 

 jV,„„ PL I, fig. 2 near the cock N. 



b. The gaseous hydrogen escapes along Klid (PI. II) to © and 

 to one or to both gasholders. When liquid hydrogen separates, the 

 compressor © receives, besides the hydrogen escaping from the 

 liquefactor, a quantity of hydrogen from the gasholders along Kpa 

 and Kijb. New pure hydrogen is then admitted from ^ha, PI. II, 

 along Kg. 



c. The float (Xjoo P^- I) does not begin to indicate until a fairly 

 large quantity of liquid hydrogen is collected. 



^ 6. The sip/wnmg of liquid hydrogen and the demonstration of 

 liquid and solid hydrogen. 



a. When the float L^^^, PI. I, shows that the glass is filled to the 

 top (this usually happens an hour after the liquefactor is set working) 

 the hydrogen is siphoned into the vacuum glasses Hydr a, Hydr b 

 etc., PI. II, which are connected behind each other so that the cold 

 hydrogen vapour, which is led through them, cools them successively 

 before they are filled. When one is full the next is moved one 

 place further. 



They are fitted with caps of the same description as the bottles 

 for siphoning liquid air, figs. 1 and 2 in the text of § 4. PI. Ill 

 represents on a larger scale 2 bottles coupled behind each other and 

 a third which has been filled, all as on PI. II, in side- and top-elevation. 

 The evaporated hydrogen escapes along d\ and d'\ and further along 

 Ko (see PI. II) to the gasholder. The letters of the figures have the 

 same meaning as in fig. 2 ; for the explanation I refer to the de- 

 scription of that figure in § 4. 



The conduction of heat in the thin new-silver is so little that 

 the new-silver tubes can be soldered in the caps h^ and that they 

 are sufficiently protected by a double wall /i^ of new-silver with 

 a layer of capoc between, which is again thickly enveloped in 

 wool. 



It has occurred that the India rubber ring k' has burst through 

 the great fall of temperature, but in general the use of India rubber 

 has afforded no difficulties, and hence the somewhat less simple 

 construction, which would lie to hand, and through which we avoid 

 cooling of the India rubber at the place where it must fit, has not 

 yet been made. 



b. If we desire to see the jet of liquid hj' drogen flowing from 



