312 



A. W. Witkowski on the 



ploration of the region of liquefaction ; 1 intend to go through 

 it on another occasion, when investigating the properties of 

 simple gases. 



In concluding I wish to express my thanks to Dr. J. Za- 

 krzewski, to whom I owe many valuable suggestions, and who 

 undertook a great part of the very considerable labour which 

 was necessary to obtain the results given in the present paper. 



Cracow, Physical Laboratory of the 



Yagellonian University. «== 



May 1891. 



[To he continued.] 



Fig. 4. 



Appendix. 

 Electric Thermometer for Low Temperatures*. 



Variation of the electric resistance of wires depending on 

 variation of temperature has been often 

 employed to construct thermometric appa- 

 ratus. Fig. 4 shows (nearly true size) a 

 disposition of electric thermometer which 

 the author has found very useful in low- 

 temperature work, on account of its sensi- 

 bility and quickness. A short cylinder r 

 of thin sheet-copper is soldered at one end 

 of a narrow brass tube c through which 

 passes a rather thick silk-covered copper 

 wire d cemented with a mixture of resin 

 and india-rubber. The outer end of the 

 brass tube ought to be carefully covered 

 with this mastic in order to prevent con- 

 densation of moisture on the thermometric 

 wire. The copper wire and the brass tube 

 are furnished with binding-screws a, b to 

 introduce the current. On the outer side 

 of the cylinder r there are wound 2 or 3 

 metres of a very fine silk-covered platinum 

 wire (diameter about T ^ millim.) ; one of 

 its ends is soldered to the cylinder r, the 

 other to the end of the copper wire d. 

 To protect the coiled wire, another sheet- 

 copper cylinder r' of somewhat greater 

 diameter is pushed over it. Both cylinders 

 r and r' are joined by a small quantity of 

 solder applied round the circumference of 

 their bases. 



* Bulletin internat. de VAwd.de Sc.de Cracovie, May 1891, 



