301 



" Since it appeared probable that the extraordinary difference in the 

 conductivity of the several specimens was due rather to non-metallic 

 impurities than to metallic admixtures, careful experiments were 

 made in every case for the detection of sulphur. In none of the 

 specimens was it possible to discover the slightest trace of sulphur. 

 Qualitative experiments having established on the other hand the 

 presence of oxygen, probably in the form of suboxide of copper in 

 every one of the specimens, an attempt was made to ascertain the 

 quantities by determining the loss which the wire after rolling suffered 

 when heated in an atmosphere of hydrogen, and by simultaneously 

 estimating the quantity of water formed. 



" In this experiment, the details of which are given in its Appendix, 

 the following numbers were obtained : 



Conductivity 42 71'3 | 847 [86-4 I 102 



Percentage of Oxygen 0-087 0-119 | 0-172 | 0-159 | 0-193 



" Unfortunately the same reliance cannot be placed upon these 

 numbers as upon the preceding ones, since the method employed 

 involves many sources of error, and want of material precluded the 

 possibility of repeating the experiments. 



" From the preceding analysis, it is obvious that the amount of 

 impurities in the several specimens examined is small, varying as 

 it does between O'lO and 1'24 per cent. The number of foreign 



* I have since found 10" 9 X 131f as the factor to reduce from this to absolute 

 measure. Thus the conductivities of the five specimens are respectively 55*2, 

 95-3, 111-4, 113-6, 134-1, in terms of one one thousand millionth of the British 

 absolute unit. W. T. 



Y2 



