| colder Barometer | 29.985 |
| Expansion with .5 above 1°, on 29 | .001 |
| ——— | |
| 29.986 |
Secondly, with .5 Tenths above 1°, on .985 Tenths above 29 Inches. To obtain which, (having already found the Height from Expansion with .5 above 1°, on 29 Inches, to be .001;) since the Expansion on .985 Tenths above 29 Inches, is somewhere above 29, yet below 30 Inches; find the Expansion with .5 above 1°, on 30 Inches, thus:
| first, with 1°, | on 30 = .003 |
| 2d. with 0°.1 above 1°, | on 30 = .0003 |
| 3d. with 0°.5 above 1°, | on 30 = .0015 |
Subtract the Expansion with .5 Tenths above 1°, on 29 Inches, from the Expansion with .5 Tenths above 1°, on 30 Inches:
| viz. on 30 = | .0015 |
| on 29 = | .001 |
| —— | |
| The Answer is | .0005, |
the Height from Expansion, with .5 Tenths above 1°, on 1 Inch above 29, i. e. on the 30th Inch: Then, if 1 Inch above 29 gives .0005;
| .1 gives | .00005: |
| and | 985 |
| ——— | |
| multiplied | 00025 |
| as whole | 00040 |
| Numbers, | 00045 |
| ———— | |
| give | .0004|925 |
| add the former Number | 29.986 |
| and, for the three remaining Decimals, may be substituted 1 Decimal in the fourth Place | 1 |
| ——— | |
| colder Barometer of equal Heat with the warmer | 29.9865 |
420. When the Quicksilver in each Barometer indicates the same Number of Inches, differing but one or two Tenths at the most; (which will frequently be the Case, in levelling flat Countries, or measuring small Heights;—instead of the usual Method, (to find the Height of each Barometer separately, with the Standard-Heat, by the 2d Column of the 2d Table, as in Section 411;)—it will be more convenient,
1st. To subtract the lower Barometer from the upper. Then,
2dly. By the 3d Column of the same Table, find the difference, (viz. of one or two Tenths at the most) below the Inches and nearest Tenth of the lower Barometer.