201 



As a consequence of the retardations in tlie structural change 

 (changements d'état) of the metal, a different value of the total heat 

 is found on cooling from that on heating. 



If a certain piece of metal is cooled or heated repeatedly, differ- 

 ent values for the total heat are found. If we start from a lower 

 temperature and -return to it after having overpassed the break 

 in the curve of total heat, a closed and not a single curve is obtained. 



4. This result is in complete harmony with the dilatometric and 

 electromotive force measurements carried out l)y myself in collabor- 

 ation with messrs. Helderman and Moesveld, on .copper, cadmium, 

 zinc and bismuth, measurements which led to the conclusion men- 

 tioned above. 



5. Le Verrier's paper contains some interesting data which we 

 shall now consider in connection with our dilatometric and electro- 

 motive force measurements. 



The curve representing the variation of the total heat of copper 

 as a function of the temperature, consists of four parts. At 350° an 

 absorptioji of 2 Cal. occurs; at 550° an absorption of 2 Cal. ; while 

 at 750°, 3.5 Cal. are absorbed. 



Thus, while our dilatometric measurements proved that there exist 

 more than two modifications of cop[)er, the same fact was noted a 

 long time before by Le Verrier. using a different method. 



The measurements of Le Vekrier which are summarized in table I, 

 have, however, been quite overlooked hitherto. 



It may be pointed out here that the transition temperatures which 

 can be deduced from Le Verrier's determinations will genei-ally be 

 too high. This is a consequence of the retardation of the molecular 

 changes, which were also observed by him. Fresh experiments with 

 the pure modifications of the difïerent metals will throw light upon 

 this point. 



6. BVom the determinations of Le Verriek there follows also, that 

 there exists a transition point for lead which has so far been unknown. 

 Experiments in this direction are in progress in my laboratory. 



7. The same may be said with regard to silver. 



8. Aluminium shows, according to Le Verrier, an absorption of 

 10 Cal. at 535°. It may be pointed out that Dittenberger (Phys. 

 Techn. Reichsanstalt at Charlottenburg — Berlin) proved ten years 



