By a series of observations on the apparent dilatation of mercury in glass vessels, compared with the results in the above tables, they deduce the absolute dilatation of glass for each degree of the thermometer, and the temperature that would be indicated by supposing the uniform expansion of a glass rod adopted as the measure of temperature as under:
TABLE III.
| Temperature by an air Thermom. | Mean apparent dilatation of mercury in glass. | Absolute dilatation of glass in volume. | Temperature by a Thermometer made of glass. | ||||
|---|---|---|---|---|---|---|---|
| Fahr. | Cent. | Fahr. | Cent. | Fahr. | Cent. | Fahr. | Cent. |
| 212° | 100° | ¹/₁₁₆₆₄ | ¹/₆₄₃₀ | ¹/₆₉₆₆₀ | ¹/₃₈₇₀₀ | 212 | 100 |
| 392 | 200 | ¹/₁₁₄₃₀ | ¹/₆₃₇₈ | ¹/₆₅₃₄₀ | ¹/₃₆₃₀₀ | 415.8 | 213.2 |
| 572 | 300 | ¹/₁₁₃₇₂ | ¹/₆₃₁₈ | ¹/₅₉₂₂₀ | ¹/₃₂₀₀₀ | 667.2 | 352.9 |
The absolute dilatations of iron, copper, and platina were investigated with great address, from 0° to 100° and from 0° to 300° centigrade; and were found as per Table below, for each degree of the centigrade thermometer.
TABLE IV.
- (A) = Temp. by the air Therm.
- (B) = Mean dilatation of iron, in volume.
- (C) = Temp. by iron rod Therm.
- (D) = Mean dilatation of copper in volume.
- (E) = Temp. by copper rod Therm.
- (F) = Mean dilatation of platina in volume.
- (G) = Temp. by platina rod Therm.
| (A) | (B) | (C) | (D) | (E) | (F) | (G) |
|---|---|---|---|---|---|---|
| Cent. | ||||||
| 100° | ¹/₂₈₂₀₀ | 100° | ¹/₁₉₄₀₀ | 100° | ¹/₃₇₇₀₀ | 100° |
| 300 | ¹/₂₂₇₀₀ | 372.6 | ¹/₁₇₇₀₀ | 328.8 | ¹/₃₆₃₀₀ | 311.6 |
Connected with this subject was another important enquiry, whether the capacities of bodies for heat remain constant at different temperatures, or whether they diminish or increase as the temperature advances. In other words, does a body that requires a certain quantity of heat to raise it from 0° to 100° centigrade, require the same quantity to raise it from 100° to 200°, and from 200 to 300°, &c.; or does it require less or more as we ascend? This enquiry involves that of the measure of temperature. They adopt the uniform expansion of air, or the air thermometer, as the proper measure, and find the capacity of iron,
| From 0° | to 100° = .1098 |
| 0 | to 200 = .1150 |
| 0 | to 300 = .1218 |
| 0 | to 350 = .1255 |
the capacity of an equal weight of water being 1.