Manchester Memoirs, Vol. li. (1906), No. 3. 13 



of electricity," i.e., of motion, and combinations of " atoms 

 of electricity " with matter. For such writers, Bacon, 

 Locke, Davy, Faraday, Joule and Mayer might never 

 have lived, and the " Correlation of Physical Forces " 

 might never have been written. 



Addendum. 



The series H2n possesses some features of local 

 geological interest from the fact that, in the north-western 

 parts of the adjoining county of Derbyshire, the mineral 

 masses consist chiefly, and contain the chemical combina- 

 tions of magnesium, calcium, zinc, strontium, cadmium, 

 barium, and lead, all of which, except magnesium and 

 strontium, are mining products of the district. These 

 include fluor-spar (calcium fluoride), lime (calcium oxide), 

 gypsum, (calcium sulphate), blende (zinc sulphide), cala- 

 mine (zinc silicate), cadmium sulphide, baryta (barium 

 oxide), barytes (barium sulphate), and galena (lead 

 sulphide). Lead mines have been worked from the time 

 of the Roman occupation, in close association with the 

 other combinations of the series fL?n. The hot spring 

 of Buxton has been shown by Mr. Strutt to give off 

 radium emanation, and may presumably yield helium, 

 as was recently found in the similar hot spring at Bath 

 by Lord Rayleigh. 



The occurrence of nearly all the members of the 

 same series of elements within so limited an area, clearly 

 indicates them as evolutionary products of the typical 

 member, helium, at the head of the series PLm 



