( 629 ) 



slant temperature, laid down in the previous communication have all 

 been applied in this arrangement, a vigorous stirring with the ring 

 shaped valved-stirrer, tlie adjustment at the desired temperature to the 

 indication of a sensitive indicator by regulating the pressure at which 

 the liquid boils while reading a differential oil-manometer made for 

 the purpose, and histl}' tiie determination of the temperature of obser- 

 vation as corresponding with the mean obtained graphically of the 

 readings of the thermometer (as in § 5). 



Plate V shows in detail the differences in the construction between 

 this form and the former plates I and II (and also Plate I Comm. 51), 

 the parts unaltered remaining are indicated by the same letters as 

 before, and the modified parts by letters with accents, while entirely 

 different parts have new letters. 



The height of the vacuumglass B\, is so chosen that the liquefied 

 gas cannot be blown out; and the glass itself has been silvered, 

 leaving open two opposing windows V\. Through these the pheno- 

 mena in the experimental tube may be watched, and from the position 

 of an aluminium wire fastened to a cork float the depth of liquefied 

 gas may be derived. If the insulating power of the vacuumglass is 

 not perfect, condensation of moisture on its outer wall may be avoided 

 by placing it into a beaker filled with alcohol, which if necessary 

 is renewed when cooled. Thus the same principle is followed which 

 was employed when necessary in the case of the cryostat (Comm. 51) 

 when the windows had to be kept clear and where hot dry air was 

 drawn through the outer spaces of the observing glasses ( F,, see 

 PI. I of this Comm. and for the details pi. I Comm. 51). 



The vacuum glass and the auxiliary apparatus are supported by a 

 copper cover N\^, with its rim tinned to protect it from the action 

 of the india-rubber ring N\, and which, like the cryostat of§l,has 

 been coated with polished nickel-paper. To this cover are fastened the 

 exit tube of the gas T^^ and the safety tube Y,^, the connection 

 X\ with the oil manometer (for details see plate I) and a copper 

 tube N\^, into which tlie India rubber stopper is placed holding the 

 apparatus to be immersed in the bath (in our case the piezometer 

 for the critical phenomena /C and the correction thermometer ?oi 

 with its leads ?„„ (comp. § 1) while the thermo-element may be 

 considered as forming an inherent part of the cryostat). There is 

 also a tube through which the capillary a^ admitting the liquefied 

 gas is led and where it is supported by a piece of cork a\^. It is 

 closed by means of an india-rubber tube a\, drawn over the tube 

 and a thin cap soldered on to a^. 



Between the cover and the rim of the vacuum glass a wooden 



