170 ANNUAL OF SCIENTIFIC DISCOVERY. 



ir.g powers, in the same manner as Mr. Thomson has shown that the con- 

 duction of electricity by the same metal is effected by a similar amount of 

 impurities. 



Alloying a metal with a non-metallic substance, also exerts an influence, as 

 is shown in the case of the combination of iron with carbon, thus : 



Forged iron, 436 



Steel, 397 



Cast iron, 359 



Similar results were obtained by combining small proportions of arsenic 

 with copper. 



The authors, with a view of ascertaining whether alloys are simple mix- 

 tures of metals, or definite compounds, made a large number of alloys of 

 various metals, using equivalent proportions, and determined their conduct- 

 ing powers. The general result obtained is, that alloys may be classed under 

 the three following heads : 



1st. Alloys which conduct heat in ratio with the relative equivalents of the 

 metals composing them. 



2nd. Alloys in which there is an excess of equivalents of the worse con- 

 ducting metal over the number of equivalents of the better conductor, such 

 as alloys composed of ICu and 2Sn; iCu and 3Sn; iCu and 4Sn, etc., and 

 which present the curious and unexpected result that the}' conduct heat as if 

 the}' did not contain a particle of the better conductor; the conducting power 

 of such alloys being the same as if the square bar which was used in the 

 experiments were entirely composed of the worse conducting metal. 



3rd. Alloys composed of the same metals as the last class, but in 

 a 2 + c 2 > 3&2; and the memoir contains a figure showing the form of the 

 surface for the case in question. The equation of the surface is obtained by 

 the elimination of X, Y, Z, between the above-mentioned equations and the 



X2 Y2 Z 2 

 equation + - - -\ = 1, as already remarked. This is reduced to the 



CP 0- C* 



determination of the discriminant of a quartic function, and the equation of 

 the surface is thus obtained under the form I 3 27 J 2 = 0, where I and J are 

 given functions of the coordinates. 



The apparatus used by Messrs. Calvert and Johnson appears to have been 

 in every way calculated to give reliable results. They provided a deal box 

 (105 millims. in width, 105 millims. in length, and 220 millims. in height), 

 with a cover, and painted white internally and externally. Inside this box 

 are two vulcanized India-rubber square vessels, the sides of which are 15 

 millims. thick. The larger vessel measures internally 52 millims. on the 

 side, and 125 millims. deep, and is capable of containing 336 cub. cent, of 

 water. The smaller vessel is 27 millims. on the side, and 125 millims. deep, 

 and has a capacity of 90 cub. cent. These vessels are painted white, and 

 surrounded with wadding; and, still further, to prevent any radiation of 

 heat, a deal board is placed between the two vessels. So little heat is radiated 

 from the larger vessel when it contains 200 cub. cent, of water at 90 to the 

 smaller vessel containing 50 cub. cent, at 16, that in a quarter of an hour, 

 the time required for their experiments, the water in the vessel did not rise 

 one-tenth of a degree centigrade. Therefore, all sensible radiation and con- 

 duction was avoided, and the rise of temperature in this vessel during the 

 experiment must have been entirely due to the heat conducted by the square 



