342 



Mr. J. T. Bottomley. 



[May 7, 



Specifying 

 number. 



Diameter 

 in decimals 



of a 

 centimetre. 



Cross 

 section. 



Resistance, 

 legal ohms 

 per metre. 



Resistance 

 between oppo- 

 site faces of 

 a centimetre 

 cube, legal 

 ohms. 



16 



•1610 



•0204300 



•181 



36 -98 x 10-6 



17 



"1430 



OIoO^UU 



*202 



32 "36 



18 



•1230 



. ai i ciA nr\ 

 Uliy4)UU 



*288 



34 "38 



19 



•1110 



'0096770 



'353 



34 "16 



20 



•0865 



•0058/bO 



odd 



32*61 



A 



•0595 



•0027810 



1-250 



34-76x10-6 





•0495 



•0019240 



1-707 



32-85 



28 



•0402 



•0012690 



2-605 



33 -06 



29 



•0340 



•0009070 



3-412 



30-94 



32 



•0290 



•0006605 



4-371 



28-87 



36 



•0220 



•0003801 



8-219 



31-24 



galvanometer. The ratio of the differences of potential is the same as 

 the ratio of the resistances of the two wires. This method of com- 

 paring the resistance of an nnknown wire with that of a known wire 

 gives admirable results, and I have recently made great use of it. 



In the following table is shown the ratio of the resistances of a 

 specimen of platinoid wire at different temperatures to its resistauce 

 at zero. The wire was the same as that specified as No. 20 in the table 

 of resistances. The length of the wire experimented on was about 

 four-fifths of a metre. The only trouble in the experiment was the 

 keeping the oil-bath, which was filled with linseed oil, thoroughly 

 stirred, and of uniform temperature throughout. 



Resistance. The Res. at 0° C. 

 Temperature. being = 1. 



0° 10 



10 1-0024 



20 T0044 



30 1-0075 



40 1-0066 



50 1-0097 



60 1-0126 



70 1-0134 



80 1-0166 



90 1-0188 



100 1-0209 



This gives for the average percentage variation of resistance per 

 1° C, between the temperatures 0° C. and 100° C, the number 



