508 



wise extends far in bolii directions withont miy break and in wliieh 

 the temperature is under complete control from 90' K. to 55° K. by 

 means of liquid oxygen and from 20° K. to 14° K. of liquid 

 hydrogen, — this gap is all the more to be regretted as in the 

 absence of a liquid bath comparisons of auxiliary thermometers with 

 the helium- or iiydrogen-thermometer in this region of temperatures 

 are completely wanting. It would be specially valuable, if this gap 

 could be filled for the lower portions of the temperature-range in 

 question by the addition of a portion above the boiling point of 

 hydrogen joining on to the range of reduced temperatures which is 

 governed by hydrogen between 20' K. and 14° K. As instances of 

 investigations for which this extension would be gr'eatly desired we 

 can name (besides the equations of state of hydrogen and neon) that 

 of paramagnetic susceptibility, that of specific heat, and that of 

 galvanic resistance. 



We have now succeeded in utilizing neon for this purpose. 

 Duiing the experiments which have led to this re-ult some thermal 

 quantities of neon were determined, which will be discussed in the 

 next communication (147(/, these Proceedings) by Dr. Crommei.in and 

 myself. Amongst other data the boiling point of neon was found at 

 about 27*^ K. and the irijtle-point at about 24.5° K. By using neon 

 exactly in the same way as hydrogen, the range of 14° — 20° K. 

 can, therefore, now practically be extended from 14° K. to 27° K. 

 As we have also found, that there is no serious dil'iiculty in con- 

 structing cryostats for pressures some atmospheres above the normal 

 (e. g. with hydrogen it is possible to go from 20° to 25° K.), a 

 pressii re-cry ostat with neon will probably allow us to ascend to 

 a temperature of 34° K., by which it would become possible to 

 study by the eye the critical phenomena of hydrogen in a bath of 

 licpiid tieon. A future communication conjointly with Dr. Crommelin 

 wdl, 1 hope, deal with an investigation of this question. 



Further as regards the region from 34° to 55° K., we may 

 nientioii even now, that one of the next communications will contain 

 a description of an arrangement by wliich I have succeeded by a 

 satisfactory method by means of hydrogen-vapour heated to the 

 desi'^ed temperature in obiaining constant temperatures in this region. 

 In a further communication to be given conjointly with Dr. Crommelin, 

 winch will follow soon afterwards we hope to give an experimental 

 deieruiination of the critical teuq;)erature of neon (compare our 

 Coinm. 147(/ below; made by means of this new arrangement. 

 The same arrangement may also be utilized in the temperature- 

 region from 20° — 34° K. But for most experiments, particularly 



