Major-General Roy’s Account of the Meafurement of a Bafe on Hounfiow-Heatfu 
Table of the Expanfions of Metals, deduced from experiments made with the Microfcopic Pyrometer in April 1785^ 
■— — 
Revolutions and 
Defcription of the Metal Rods put to experiment. 
parts of the 
micrometer for 
the expanfion 
Aftual expanfion in parts of an 
inch by i8o Q , the revolutions 
being divided by 42.06. 
By 
i° of Fahrenheit the expanfion is 
Bales of 
27400 feet of tliefe metals 
would expand. 
on five feet. 
By 1 8o° 
By i°. 
On 5 feet. 
On 1 foot. 
On 100 ft. 
On r foot. 
10 feet. 
100 feet. 
400 feet. 
600 feet. 
1 000 ft. 
By i°. 
I By io°. 
By 20 0 . 
By 3c 0 . 
Suppofed to be Hamburgh plate brafs ; length 1 
42.187 inches, or 3.568 feet; breadth 0.55 j 
inch; thicknefs 0.25 inch; and weight 1 lb. { 
io-|oz. Its expanfion was meafured by 25.47 c 
Rev.Pts. 
Parts. 
In. 
In. 
In. 
In. 
In. 
In, 
In. 
In. 
in. 
In. 
In. 
In. 
In. 
Standard brafs < 
fcale. 
35* 6 9 
rn 83 
I 9 *To 3 - 
0 «III 3?3 
0.0222646 
2.22646 
0.0001237 
0.001237 
0.01237 
0.04948 
0.07422 
0.1237 
3 ° 3 8 93 8 
33 * 8 93 8 
67.7876 
101.6814 
■ 
Englifh plate 1 
brafs, in form < 
of a rod. 
revolutions of the micrometer; wherefore that 
on five feet would have been meafured by - 
Length five feet; breadth 0.9 inch; thick-' 
nefs 0.15 inch; and weight 2 ibs. 5I oz. 
Difficult from its thinnefs to be kept free from 
. 3 6 - 4 ! 
2 0 . iLL 
0.113568 
0.0227136 
2.27136 
0.0001262 
0.001262 
0.01262 
0.05048 
0.07572 
0.1262 
3.45788 
34-5788 
69.157 6 
J 03 . 73 6 4 
.warping, - d 
Englifh plate 
brafs, in form < 
of a trough. 
j 
' Length five feet; breadth 1.4 inch ; depth 1 
inch ; weight 8 lbs, 3 oz. Perfectly flrongand > 
-flraig.ht, - - J 
36.45 
20. LA 
0.113693 
0.0227386 
2.27386 
0.0001263 
0.001263 
0.01263 
0.05052 
0.07578 
0.1263 
3.46062 
34.6062 
69.2124 
103.8168 
Length five feet ; breadth 0.5 inch ; thicknefs-. 
Steel rod. i 
0.3 inch ; weight 2 lbs. 7I oz. Made from the i 
- very fame bar with the chain, J 
22.02 
1 2-iVe 
0.068684 
°* 01 37368 
1.37368 
0.0000763 
0.000763 
0.00763 
0.03052 
0.04578 
0.0763 
2.09062 
20.9062 
41.8124 
62.718b 
Caft iron < 
prifm. 
Length five feet; each of its fides i| inch ; 
and weight 11 lbs. 9 oz Cut from the fame > 
21-34 
T T 86 
I I .JSS 
0.066563 
0.0133126 
1.33126 
0.0000740 
0.000740 
0.00740 
0.02960 
0.04440 
0.0740 
2.02760 
20.2760 
40.552c 
60.8280 
L rod with the ftandard prifms of the pyrometer, J 
j 
i 
r Length five feet ; LAtbs inch diameter ; 
Glafs tube. < 
! weight 1 lb. igf oz. Drawn from the fame 1 
1 4-93 
Q 29 
0*046569 
0.0093138 
o- 93 T 3 8 
0.0000517 
0.000517 
0.00517 
0.02068 
0,03102 
0.0517 
1.41658 
14.1658 
28.4316 
42.4974 
1- pot of metal with the meafuring rods, - J 
f Length 40.44 inches, or 3.37 feet ; mean dia- 
meter fix-tenths of an inch ; and weight 1 lb. 1 
Solid glafs rod. 
1 2 oz. It had been applied for feveral years to a 1 
clock. Its expanfion was meafured by io.j. 6 j 
15-54 
Q 63 
O’ToS 
0.048472 
0.0096944 
0.96944 
0.0000539 
0.000539 
0.00539 
0.02156 
0.03234 
0.0539 
1.47686 
1 4.7686 
29.5372 
44 - 3 ° 5 8 I 
revolutions of the micrometer ; wherefore that | 
on five feet would have been meafured by - J 
j 
