142 Further Experiments, &c. (Marcu, 
The general results may now lL classed under their respective heads 
as follows : 
Range of Reading of Deduced dilatation 
temperature. micrometer. for 180 degrees. 
Duplicate Iron 10 feet Bar. 135,6 2182 1,001191 
139,9 2301 1,001217 
136,0 2229 1,001213 
133,6 2207 1,001223 
133,7 2183 1,001208 
133,6 2114 1,001171? 
Mean, rejecting the last, .... .... 1,001210 
135,6 2649 1,001446 
Pure Gold, rolled hard,, 18 9 2718 1,001438 
136,0 2637 1,001435 
133,6 2592 1,001439 
annealed,..... 133,7 2593 1,001435 
133,6 2566 -1,001421 ? 
Mean, rejecting the last, eae 1,001438 
Standard Silver, ;'5 alloy, mete 9 3543 auc 
u 
rolled hard, 136,0 3503 1,001906 
133,6 3423 1,001896 
annealed, 133,7 3423 1,001895 
133,6 3375 1,001869 ? 
Mean, rejecting the last, .... s+. 1,001904 
3133 1,001697 
Copper annealed, but parti- | 141 5 ses 1,001685 
ally hammered in making< 135,8 peed 1,001688 
cane 132,8 3022 1,001684 
Q ecceeeccesceecsececs 1 133, 7 3071 1,001702 
L133, 5 3048 1,001690 
Mean of the whole, ...... Siete 1,001691 
It must be remarked with regard to this series, that, besides other 
sources, of error, the dots, marked with a needle-point by an unskilful 
hand, were rather difficult to bisect; and further, the continual shift- 
ing of the apparatus, to bring each bar successively under the focus 
of the microscopes, was more than sufficient to account for irregulari- 
ties greater than are observable in the present results. 
In comparing the list with the former one, one is struck with the 
close agreement between two metals of very different fusibility, namely, 
standard silver, and brass ; a circumstance which permits the application 
of silver divided circles to astronomical instruments of the latter metal. 
Platina is by no means so well adapted for such a purpose. The opera- 
tion of annealing does not seem to have the slightest effect upon the rate 
of expansion, a fact well worthy of consideration, as it would be at all 
times difficult to say what allowance should be made on such account, 
where the degree of hardness of a metal might be uncertain. 
The latest determinations of the dilatations of metals (which have 
reached me since the above experiments were finished), are those of 
Mr. Daniell; but the apparatus used by him, (a plumbago tube of six 
inches in length, holding a rod of the metal to be operated on,) how- 
ever well adapted for approximate measurement of intense heats, is 
obviously not worthy of trust for minute measures at low temperatures, — 
