2-44 Barns and Iddings — Electric conductivity observed 



megohms, the abscissae temperatures in °C. The curves 

 (which, as shown, contain all our observations) are numbered 

 (1), (2), (3), as in Table I, relatively to the magmas. Between 

 1000° and 1500° the points lie so near the axis, that a discrimi- 



Legends. 



Fig. 1. Chart showing the relation of the specific electrolytic resistance 

 (megohms, cc) to Temperature (°C), in case of 



(1) An acid magma, 



(2) An intermediate magma, 



(3) A basic magma. 



(4) Zinc sulphate, concentrated aqueous solution. Resistance relative. 

 Fig. 2. Crucible and appurtenances with the furnace withdrawn: 



aaq, rock magma in platinum crucible ; 

 p, tubular platinum electrode ; 

 i, insulator (fire clay) of the thermocouple ; 

 aj3, thermocouple with its junction at o : 

 ee', electrolytic current (intermittent). 



nation is no longer possible. This can be done, however, by 

 expressing the variations of conductivity with temperature for 

 the interval. It is here omitted because it leads to no novel- 

 ties. The corresponding curve for a concentrated solution of 



