SOMl COX 1 1 MI-OH.Ih-y .lin.lXClS l.\ /7/t s/( s / (.J.! 



set up a (Ictiniliiin by wliicli i'\»-r\ rk-iiK-nl can bv c<)nti(k'iill\- assi>;iK-(l 

 to OIK- i-las-s or to thr otliir. lii tact tht-a- is a tciuleiicy lo l)CKiii,lA 

 ilrtiiiiiijj metallic conduction, and then dftinc nictals as the clcnunts 

 which display it! The ditVlcult\-, as usual, is to make the detmition 

 sharp eiioui;h to decide a lew intermediate or transitional cases. 

 .\n>-one exeii >lii;hll\ ac(|uainted with chemistiy or physics would 

 instaiitK' recoi;ni/e .is mel.ds the elements in the first column of 

 the Peri«Klic Table, ami those at the bottom of the table in all the 

 columns; and as non-metals, with the same ease, the elements in the 

 topmost row of the table and down the right-hand side. The first 

 element of evcr>- column after the first two is non-metallic, and the 

 non-metallic character advances farther and farther down the 

 columns as one procei-ds across the Tabic finm left to right. One 

 might say that the elements which are not metals occupy the north- 

 east sector of the Table, and the debatable ones cross in a diagonal 

 band from northwest to southeast. The elements which are gases 

 imtler the usual circumstances of temperature and pressure are 

 extreme instances of non-metals; but some ol liie deliniteK- non- 

 metallic elements, and all of the deb.itable ones, <ire soliil nr li(|uiil 

 uiuler the usual conditions. 



Wry little could he said about the elenunts wliicli under ordinary 

 conditions arc gases, for very little is known ai)out the manner in 

 which they conduct electricity when liciuetied or frozen. ProbabK 

 the reason is that the experiniental conditions wouki be unusualU 

 ditticult, and the substances probably very bad conductors; it is not 

 e.is>- to imagine solid hydrogen moulded into a cylinder, drawn into 

 a wire, clamped or sealed between electrodes, f)r filled into a sheath 

 less cf)nductive than the hydrogen itself. The difficulties ma\- not 

 be insuperable; but they have not been generally oxercome. 



.As for the solid elements which are dehnitely not metals, or which 

 l)elong to the debatable group, there i> an abundance of data in 

 print, and yet not nearly so much as we need. In general their re- 

 sistances arc tremendously greater than the resistances of metals; 

 "tremendously" for once is not an extra\agant word, for the con- 

 ductivities of the elements are spread over a sweeping range of orders 

 of magnitufle which few if any other ([ualities of theirs can rival. 

 Ihe ma.ss of the heaviest knovyn atom differs from the mass of the 

 lightest only by a factor of '240; the densities of the solidified elements, 

 their compressibilities, their other mechanical and thermal proper- 

 ties range over not more than one f>r two, at the niost three orders of 

 magnitude; even the energy re(|uired to extract the innermost electron 

 of an atom rises by a factor of onl\- 10' in passing Inmi tin- tir-^t to 



