352 Mr. W. A. Price on the Electrical Resistance of 



total volume, but to the co-volume as calculated by myself? 

 This result alone is enough to show the advantage which my 

 views possess over those of Richards. The co-volume is, in 

 fact, that part of the total volume which changes with tempe- 

 rature, while the true volume can only be altered by pressure. 



Further, I would refier to all the other consequences which 

 are rendered possible by the separate calculation of the co- 

 voiume, such as the calculation of the intrinsic pressure (this 

 is proportional to Richards' "energy- quotient "), and the 

 relation of the co-volume to the most varied properties. Had 

 Richards separated the notions of co-volume and true volume, 

 many of his investigations — especially that in Zeitschr. Physik. 

 Chem. xlix. pp. 16 et seq. — would have taken a much simpler 

 form. 



Not only, however, the notion of co-volume, but also the 

 consideration of the mutual relationship between external 

 and internal volume must I defend against the views of 

 Mr. Richards. Now I am not only in agreement with 

 Mr. Richards, but may even claim priority regarding the 

 view that not only the envelope but also the core of the atom 

 is compressible ; but the two ideas must be maintained 

 separate — this is confirmed by the theories of van der Waals, 

 and of Clausius, Mossotti, Exner, as well as by my verification 

 of both theories. 



Finally, I have already pointed out the agreement of my 

 volume-theory with FresneFs theory of a bound and free 

 aether; and it also appears to me that the various aether 

 theories, such as those of Lord Kelvin, are in agreement with 

 my views, but not with those of Mr. Richards. 



Charlottenburg, Technische Hochschule. 



XLL The Electrical Resistance of a Conductor the Measure of 

 the Current passing. By W. A. Price, Fellow Rhys. Soc* 



1. i^HANGE in the length of a platinum wire is a con- 

 vey venient measure of the current, but the ordinary 

 hot-wire instrument is net sufficiently precise for some 

 purposes. The experiments in this paper were made by 

 Mr. G. H. Wright, in Crompton & Oo.'s works at Chelmsford, 

 to ascertain whether the resistance of a conductor would be a 

 better measure of the current than its length where consi- 

 derable accuracy is required, the practical object in view 

 being the calibration of alternating-current instruments. It 

 was hoped to retain the advantage possessed by the dynamo- 

 meter of calibration by direct currents, and thus of direct 

 * Communicated by the Physical Society : read May 12, 1905. 



