1833.] Expansion of Metals. 133 
arc is this case, is less than a hundred thousandth of an inch, and is, 
therefore, inappreciable ; nor is it attempted to explain in what way 
the effect observed should be one hundred times greater than could have 
been expected. Captain Kater, it is true, immediately devised a reme- 
dy for this anomaly, by seeking the neutral axis of the bar, and im- 
printing the dots upon ledges formed at the two extremities in this 
plane. The Indian standard bar was formed on this principle, the parts 
bearing the dots being two-fifths in vertical height of the remainder of 
the bar (figs. 1, 2.) : but upon a length of 10 feet, we may conceive that 
a trivial error in the assumed position of this neutral axis may be suf- 
ficient to account for the slight anomaly in the readings alluded to. It 
will be evident that on the slightest slackening in the supply of steam, 
the upper part of the bar would become cooler than the lower, for the 
same reason as given above, and a contrary flexure would thus take place 
to a similar amount. By taking therefore the mean reading of each 
series of experiments, we need not fear any influential error from this 
source, which I have the rather pointed out on account of its apparent 
confirmation of Captain Kater’s curious discovery. 
We will now proceed to the experiments, placing them in a tabular 
form according to their dates, and correcting the thermometers, &c. 
to a common standard. 
First Series, 20th November, Standard Iron Bar A. 
Thermometers. Micrometer 
temperature, 
Sz gare eee ; 
bs s Inserted in the | Hour of | Re@dings- 
2 S In the Bar. Obseryva- | Observations. 
5 &| steam- |———— tion. Divisi 
221 pipe. North South ivislons. 
io) end. end. 
Oo Oo 
1 75,3 77,22) Noon —1067 The indications of the 
2 152, 152,0 — 82 |micrometers and ther- 
3 170,8 164,7 -+ 113 |mometers were read off 
4 178,6 169,7 to + 211 {simultaneously at equal 
5 184,4 185,4 + 314 {intervals of time, to as- 
6 190,2 194,0 + 493 |certain theratio of calo- 
7 212,0 212,0 | 4 P.M. +1157 |rific accession, but the 
8 212, | broken +1151 Jopening of a leak pre- 
9} 210,6 212,0 : +1140. |vented the completion of 
10 210,2 212,6 +1133 | the series. 
11 213,3 212,8 : +1152 Observers, Major Ever- 
12 201,2 +1033 est and Captain Wil- 
13 188,9 -+ 806 cox. 
Difference of 136,0 = 2213 
