4th, and lastly, the Degree of Temperature of the detached or Air-Thermometer.
This Employment is to be carefully attended to; during the Time, that similar Observations, by preconcerted Agreement, are making, with three other similar Instruments, on the Top of the Mountain, or any elevated Station in the Atmosphere, by Means of the Balloon; and to be written with a red Lead Pencil, in a Patent Asses Skin Pocket Book.
The Instruments to be compared on Return from the Mountain, or upper Station.
Each single Observation, made with one Set of Instruments below, is to be compared with each single corresponding Observation, made with the other Set above.
And two Observations are said to correspond, when both are made nearly at the same Time, the one below, and the other above.
351. Take Shuckburgh’s first Example, (Ph. Tr. for 1777, 2d Part, Page 577.) viz.
“Let the Point at which the Quicksilver stands in the Barometer, on the Ground, be 29 Inches 4 tenths: the attached Thermometer 50 Degrees of Temperature, and the Air Thermometer, or general Temperature of the Air 45°: at the same Time, that at the Top of the Mountain, or other elevated Station in the Atmosphere, the Barometer stands at 25 Inches 19 Tenths, the attached Thermometer at 46°, and the Air Thermometer at 39° and 1⁄2: required the upper Height in English Feet.”
Rules for the Work: and Practice of the first Example.
352. The Work is divided into three Stages.
The End proposed in this first Stage is to bring the colder Barometer, to the same Expansion or Temperature with the other.