336 
MR. H. J. CHANEY’S RE-DETERMINATION OF 
form of either one of the gravimeters would be greater than the probable error of 
experiments on the dilatation of a body of the simple form of a rod or bar. 
The gravimeter C. for instance, is made of a gun-metal alloy, the coefficient of linear 
expansion of which alloy was found by Sheepshanks in 1848 to be O’OOOOCffil? for 
1° Fahr. Tt was subsequently found by Clarke (1860) to be 0'00000986 ; Fizeau, 
also, has shown that Sheepshanks’ coefficient was too low, owing possibly to the form 
of the mercurial thermometer adopted in 1848. For the gravimeter C, Clarke’s 
coefficient of linear expansion has been therefore taken. For the gravimeter S the 
coefficient of linear expansion for 1° Fahr., 0’0000104, has been taken; and for Q the 
cubic expansion 0 00001924 for 1° Fahr. 
Thermometers. 
Six standard mercurial thermometers were used— 
Centigrade 
.4,517 
? ? 
.4,518 
? ? 
.4,575 
Fahrenheit 
. 430 
5 5 
.12,765 
?5 
. 20,065 
The errors of these thermometers were originally determined in relation to the 
hydrogen thermometer at the Bureau International des Poids et Mesures, Paris, and 
were re-determined after the experiments. Thermometers 4517 and 4518 were made 
of a hard glass (including 71‘5 silica, 14"5 lime, 11‘2 soda, 1*3 alumina, 07 sulphuric 
acid, and 0'3 potash), and were highly sensitive. 
Thermometer No. 4517.—Divided into 0 0, 1 C, from 4 0- 3 to + 103 o- 4. Distance from 
middle of reservoir to 0° C. is 53 mm. Total length of thermometer is 
702 mm. Length of a degree is 5'290 mm. 
Correction for Calibration. 
Divisions. 
Corrections. 
Divisions. 
Corrections. 
O 
O 
O 
o 
0 
o-oooo 
50 
+ 0T668 
+ 2 
0-0068 
60 
+ 0-1599 
8 
0-0393 
62 
+ 0-1520 
16 
+ 0-0651 
70 
+ 0-1163 
18 
+ 0-0639 
80 
- 0-0082 
20 
+ 0-0635 
90 
- 0-0257 
30 
40 
+ 0-1039 
+ 0-1246 
100 
± o-oooo 
Divisions equidistant. Probable error of correction ffi 0 o, 0010 C. 
