Page:Transactions of the Provincial Medical and Surgical Association, volume 4.djvu/250

Preliminary observations made with the same barometer, at both stations, May 30th, 1834.—First series.




Library House or Lower station.	Baro.	Attach. Therm.	Detach. Therm.	Hyg.	Time. (p. m.)	Wind	Weather.
Setting out	29.705	65.0	61.0	55.0	5 30	Light E.	Very fine, some detached clouds moving from N. W.
Return	29.700	63.0	57.0	52.0	7 20	Ditto
Mean	29.7025	64.0	59.0	53.5	6 25
Summit of the beacon	28.700	53.0	53.0	48.0	6 45	Very high E.	Less cloud, otherwise as above

8. As this correct specific gravity is to 1.00000 (the standard) so is the approximate height (3) to the correct height.^[1]

Details of the above formula, taking the second series of observations as data.

1. Mean of barometer at lower station.	29.543	Barometer at the upper station	28.550
2. Subtract for the expansion of mercury at 65°.	—.083	Subtract for expansion of mercury at 58°	.057
	———		———
	29.460		28.493

			Logarithm.
3.	29.460	⁠	4692.321	— Difference,	144.945	fathoms.
	28.493	⁠	4547.3826		6
		⁠			————
Approximate height in feet					869.670

4.	Lower station, temperature of the air	65.0	Dew-point	58.5
	Upper ditto, ditto	58.0	Ditto	52.0
		——
	Mean	61.5

	Expansion of air for temperature	61° (per table)	.06041
5.	Ditto for vapour	58° (ditto)	.01633
	Ditto ditto	52° (ditto)	.01336
	Mean		.01484
			——
	Total expansion		.07525

6.	Then, 1.07525 : 1.00000 : : 1.0000		.93002
7.	Increase of density of air for vapour at	58°—.01051
	Ditto	52°—.00864
	Mean		.00958
			———
	Correct specific gravity of the air		.93960
8.	And, .93960 : 1.0000 : : 1.00000 : 925.5 the height in feet.

1. The tables referred to above, will be found in Daniell's Meteorological Essays, second edition, viz.: that for the expansion of mercury, and the mean dilatation of glass, p. 372; table of expansion of air for temperature and vapour, p. 177; table of increase of density of air for vapour, p. 177.