CHAPTER LXXII.
Section 365. HAVING therefore understood the Foundation, Construction, and Use of the first Table; in the present Case, having also added the decimal Parts of an Inch just found, for the Expansion,—to the Inches and Tenths, expressing the colder Barometer; which will then have the same Expansion, or Temperature with the warmer, thus;
| Inches. | |
|---|---|
25.19 | colder Barometer: |
.0101 | Expansion on the same, in Parts of an Inch with 4° of Temperature, (rejecting all but the first Decimal as too minute,) |
———— | |
25.2|001 | added; this Sum will express the Point at which the Quicksilver in the colder Barometer woud stand, when equally expanded, i. e. in the same Temperature, with the warmer. |
366. 6th Step. Place both Barometers, now of equal Temperature with the warmer, together, first, the upper Barometer; and under it the lower, thus:
Inches 25. 2 Tenths.
29. 4
END OF THE FIRST STAGE.
367. The Ends proposed in the second Stage of the Work, (the colder Barometer being now brought to the same Expansion or Temperature with the warmer,) are two: First, to find, (by the Application of the second Table) the Heights, in Feet and Tenths, in the Atmosphere, corresponding to the Points at which the Quicksilver stands in both Barometers, which have now the same Temperature, viz. that of the warmer equal to 50°: on a Supposition that they were both exposed to the Temperature of 31°.24, on Farenheit’s Scale, which is about the Standard or freezing Point, for which sole Purpose the 2d Table is calculated.
N. B. The Second Stage includes two Steps only, viz. the 7th and 8th.
368. 7th Step. The Barometers being placed in one View, as before directed, thus:
Upper Barometer, Inches 25 .2 Tenths.
Lower Barometer, Inches 29 .4; find, with the Temperature of 31°.24, the corresponding Heights in the Atmosphere.
This is to be done by referring to the 2d Table, for the Application of which there are separate Instructions: See the Explanation of the second Table.[120]