244 PROCEEDINGS OF THE AMEIilCAN ACADEMY. 



any but very special needs. Nevertheless, at least one such combina- 

 tion is said to have been successfully used for a certain purpose. The 

 writer has made repeated efforts to obtain a suitable instrument from 

 the Weston Company, and from some others, without success. 



Rogers Laboratort of Physics, 



Massachusetts Institute of Technology, 



Boston, September, 1895. 



NOTE. 



A portable form of D'Arsonval galvanometer, combined with a rhodo- 

 platinum thermo-couple and graduated in degrees up to 1500° C, is now 

 announced by Keiser and Schmidt of Berlin.* Its gi-aduatiou is based 

 upon the investigations of Holborn and Wien at the Reichsanstalt. 



The author desires, also, to call attention to the convenience of 

 maintaining a constant calibration curve for the Lc Chatelier pyrom- 

 eter by the insertion of an adjustable resistance in the circuit. By 

 this means the unavoidable slight changes of resistance of the circuit, 

 of sensitiveness of the galvanometer, and even of electro-motive force 

 of the couple, can be readily offset. Tlie procedure would, of course, 

 be to adjust the resistance until the sulphur or the copper reading was 

 the same as in the original calibration. S. W. H. 



* Zeitschrift f iir Instrumentenkunde, XV. 285 (August, 1895). 



