266 Mr. Daniell 07i a New Regisler-Pt/rometer 



which it is not probable, from the preceding observations, 

 that there is any error of material importance. 



Table XVII. 



Linear Dilatations of Solids by Heat. 



Dimensions which a bar takes whose length at 62° is 1-000000. 



The regularity of these several expansions is very striking. 

 As long as the metal retains the solid form, the dilatation 

 proceeds according to a fixed law, without any sudden starts 

 or changes; till assuming the form of a liquid it doubtless is 

 subject to a different mode of action. 



I shall conclude these observations with the results of some 

 experiments which I made to determine, if possible, the cause 

 of the singular change of texture in platinum, when intensely 

 heated in the black-lead registers, which I described in my 

 former paper*. Upon showing the bar so changed to those 

 who were best acquainted with the working of this metal, they 

 universally ascribed it to the action of sulphur: but nobody 

 could explain to me why this action should require such a very 

 intense heat; as up to the temperature of melting cast-iron, 

 to which it had several times been exposed, no change took 

 place; but the bar remained perfectly soft and malleable. 



In De Ferussac's Bulletin for November 1830, there is an 

 abstract of my paper on the Pyrometer, which the Editor 

 concludes with the observation, that " unfortunately I inclosed 

 in the crucible which contained the register and the bar of 

 platinum some pieces of iron, without being aware of the fact, 

 which is known to all the workmen who manufacture pla- 



• See Phil. Mag. and Annals, vol. x. pp. 354, 355.— Edit. 



