140 Intelligence and Miscellaneous Articles. 



is greater, and the more so the smaller the quantity of undissolved 

 salt in the magma. 



The mathematical part of the paper consists of four divisions. 

 In the first, the equations of the theory of diffusion of gases 

 are developed. In the second, they are applied to evaporation. 

 The solution of this problem in the former paper was only an 

 approximate one, yet quite sufficient for calculating the experi- 

 ments. In the present paper the exact solution of the problem 

 is communicated. Their establishment forms a fresh application 

 of the equations which the author has developed in the theory of 

 the formation of ice. In the third section the differential equations 

 of the diffusion of gases are transformed into the equations which 

 serve for calculating the diffusion of liquids. The last section 

 contains the applications of these equations to the calculation of 

 experiments on diffusion. — Wiener Bericlite, Nov. 21, 1889. 



ON THE CHANGES OF TEMPERATURE RESULTING FROM THE 

 TORSION AND DETORSION OF METAL WIRES. BY DR. A. 

 WASSMUTH. 



In the year 1878 Sir W. Thomson (Phil. Mag. vol. v. p. 19) 

 deduced from the mechanical theory of heat the principle that a 

 twisted wire must become cooled when the torsion is suddenly 

 carried further. 



In the above research it is proved for iron, brass, and particularly 

 for steel that the phenomenon in question actually occurs ; and the 

 opposite one on detorsion, that the cooling or heating increases 

 with the angle of rotation, and that the change of temperature 

 observed for a steel wire agrees very well with the calculated one. 



In these experiments thermoelements were soldered to six steel 

 wires connected with each other by pieces of wood, and slightly 

 stretched horizontally, in such a manner that this wire arrangement 

 could both be stretched and twisted. It was possible in this way 

 to compare the very small changes of temperature on torsion and 

 detorsion with the much larger ones due to stretching, and which 

 indeed can be done in two ways. For the cooling 6 which occurs 

 on the torsion of a wire of length Z from the angle iv Q to w x it was 

 calculated 



E 

 in which m was the weight, r the radius, the modulus of 



n A-L + ^O 



torsion, y^ its relative decrease with the absolute temperature t, 



c the specific heat of the wire, and J the mechanical equivalent 

 of heat. There was thus obtained for 0, 



Calculated 195-10- 5 of a degree Centigrade; 



Observed 191-10-5 

 Several further experiments likewise showed agreement with what 

 has been said. — Wiener Berichte, Nov. 7, 1889. 



