Intelligence and Miscellaneous Articles. 



79 



conductivities, viz. the British- Association unit, or ohm, and the 

 Siemens unit. 



Pure silver, annealed 



Copper, annealed 



Silver 075, annealed 



Pure gold, annealed 



Aluminium, annealed 



Magnesium, cold-beaten ....... 



Pure zinc, annealed at 350°... 

 Pure cadmium, cold-beaten ... 



Brass, annealed* 



Steel, annealed 



Pure tin 



Aluminium bronze, annealedf 



Iron, annealed 



Palladium, annealed 



Platinum, annealed 



Thallium 



Pure lead 



German silver, annealed J 



Pure mercury 



Resistance of 1 metre 

 by I square millim. 



Ohm. 



00154 

 00171 

 00193 

 0217 

 00309 

 00423 

 00565 

 0-0685 

 00691 

 01099 

 01161 

 01189 

 01216 

 01384 

 01575 

 0-1831 

 1985 

 0-2854 

 0-9564 



Siemens 

 unit. 



Conductivities, 



referred to 



silver. 



00161 

 00179 

 0-0201 

 00227 

 00324 

 0-0443 

 00591 

 00716 

 00723 

 01149 

 61214 

 01243 

 01272 

 01447 

 01647 

 01914 

 0-2075 

 02775 

 1 0000 



100 

 90 

 80 

 71 

 49-7 

 36-4 

 275 

 22-5 

 22 3 

 140 

 13-3 

 130 

 12-7 

 111 

 9-77 

 8-41 

 7 76 

 5-80 

 1-61 



From the third column, which gives the specific conductivities of 

 these metals referred to that of silver, it is seen that the results 

 ohtained by the author differ but little from those which have been 

 given by other experimenters. 



The diminution undergone by the electric conductivity of the 

 metals with rise of temperature was the essential aim of M. Benoit's 

 researches. This influence of temperature, already remarked by 

 Davy, was studied by Ed. Becquerel, who measured it up to 100°, 

 by Matthiessen, who followed it as far as 200°, and by other phy- 

 sicists. M. Benoit has set himself the task of studying this 

 variation of conductivity within the most extended limits of tempe- 

 rature. The conducting wire on which he operated was wrapped 

 spirally round a cylindrical support of pipeclay, enclosed in a muffle 

 which was immersed in a bath of a volatile liquid heated by aid of 

 a Perrot furnace. The liquid was water, mercury, sulphur, or cad- 

 mium, by means of which constant temperatures were obtained of 

 100°, 360°, 440°, and 860°. Moreover a great number of experi- 

 ments were made above 360° by aid of a mercury bath, the tempe- 

 rature of which was regulated. These measurements were corrected 

 for the dilatation. 



Plates annexed to the memoir give the graphic representation of 

 the results obtained. They show that the increase of the resistance 

 follows a regular course which continues, probably, for all the 

 metals, as for tin, lead, and zinc, as far as their melting-point §. 



* From the wiredrawers : copper 64*2, zinc 33*1, lead 04, tin 04. 



t Copper 90, aluminium 10 



Copper 50, nickel 25, zinc 25. 



§ Fusion is in general accompanied, as we know from the researches of 



