1833.] Expansion of Metals. 139 
nute accuracy as before. We prepared in the mint two laminated 
straps; one of pure gold*, 10 feet two inches long, 22 inches broad, 
and about 4 inch thick, weighing about 320 lbs: the other of stand- 
ard silver (; copper alloy), of the same dimensions or a little thicker. 
The two ends were cut away, and marked with fine dots as nearly as 
possible at the distance of 10 feet apart. As the run of the micrometer 
was only one half of the expected expansion of the metals now to be 
tried, the precaution was taken of inserting second dots about ;,th of 
an inch within the first, the distance between the two dots being care- 
fully measured under the microscope. I have said that the inner steam 
cylinder was of copper; all that was necessary therefore to enable us 
to measure the expansion of this metal along with the rest, was to fix 
two small tongues to the two extremities of the tube, projecting under 
the focus of the microscopes, and bearing the marks for measurement. 
For consistency I will insert the new series of experiments with the 
same detail as, before, to enable other experimenters to judge of the 
measure of confidence due to our simple but somewhat tedious inves- 
tigation. 
Highth Series of Experiments on Expansion. 
Thermometers. Readings of the micrometer. 
Day. i Mails (Ie ra Gold. Silver. Copper. 
South. | North. | pipe. f (add 2525.) | (add 2277.)| (add 2297.) 
Se wed) Ug stmaht | oe ele ad) cape) pak wor af ino 
Nov. | 76,0! 76,6| 76,4 
Noon | 211,7 | 212,2 | 213,2 r 
211,9 | 212,2 | 213,2 | +--+ 1290 —758,5 $358 —140 
to | 211,8 | 212,1 | 213,8 
211,9 | 212,2 | 214,3 + 1275 
5 p. M.| 211,8 | 212,1 | 213,0 —776 +360 —129 
211,8 | 212,0 | 211,2 + 1269 | 
PEO 2het | 21207 
aia | 2120 | a1t'o | ¢ + 1279 | —768 | 4362,| —129 i 
IstDec] 72,9} 71,6] 71,4 : 7 
za.m.i 72,41 71,6} 71.6 | ¢_ 1023 —960 —937 | —1058 | 
= an wees bss 
Ascendingrange, 135,6] dilatation, 2182 2649 3543 3133 
Descending do. 139,9° ditto. 2301 2718 3574 2222 
Ninth Series. ; 
Dec. 1.| 76,0 | 75,6 | 76,5 
Noon | 76.2] 76,0| 76,5 | \_ ee Te} 979 
211,6 | 212,2 | 213,4 | ++ 1266 —798 +358 —157 
to 211,8 | 212,1 | 214,4 | ++ 1267 —7/99 +365 —141 
4 p.M.| 211,9 | 212,1 | 212,2| -+ 1254 —805 +364 —197 |t 
Ascending range,136,0/ dilatation, 2229 2637 3503 : 3098 
* Of the old gold mohur standard, or 1 car. 34 gr. Br., which, as far as such expe- 
riments go, may be deemed pure. 
+ Before this experiment, the hole had been pierced through the copper cylinder, 
