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XXIV. Further Experiments with a new Register-Pyrometer for Measuring the 
Expansion of Solids. By J. Frederick Daniell, Esq. F.R.S. Professor of 
Chemistry in King's College , London. 
Read June 16, 1831. 
In my former communication on a new Register-Pyrometer, which has been 
honoured with a place in the Philosophical Transactions for 1830, 1 stated that 
I hoped, at some future period, to be able to lay before the Society the results 
of some experiments upon the dilatation of metals to their melting points ; and 
I now purpose to redeem this pledge. 
My previous observations upon the subject of expansion, were directed 
chiefly to the object of establishing what degree of confidence might be re- 
posed in the instrument as a measure of temperature ; and I was able, I trust, 
to exhibit such an accordance between the measures which it had afforded and 
those of the best experimenters, long previously obtained with various metals 
to the boiling point of water, as fully to establish its sufficient accuracy. The 
comparison however which I most relied upon, was with the experiments of 
MM. Dulong and Petit, upon the expansion of platinum and iron to the high 
temperature of 572° Fahr. ; and as this is a point of fundamental importance, 
I shall still further strengthen it by a comparison with the results obtained by 
the same distinguished philosophers with copper, the only other solid metal 
to which they extended their inquiries. 
Previously to this, I trust it may not be thought tedious, if I briefly relate 
the results of some trials for obtaining registers of uniform composition, which 
might preclude the necessity of determining the rate of expansion in each indi- 
vidual instance. 
Exp. 23. For this I had recourse to Wedgwood’s ware, of which I obtained 
some bars carefully constructed and highly baked for the purpose. The 
expansion of these I found precisely equal to that of platinum ; so that when 
