This is to be hung in the Shade at the Distance of a Yard (or two) from the other:—to shew the _general_ Temperature of the Air at the same Time and Place: and may be called the _Air Thermometer_. A proper Person, on the Ground, having a good Watch, with Pen Ink and Paper at Hand, is to attend the Instruments _below_ every ten Minutes, (or at any other _preconcerted_ Intervals of Time,) putting down, 1st. The Time of each Observation. 2d. The Point at which the Quicksilver stands in the Barometer. 3d. The Degree of Temperature of the _attached_ Thermometer. 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. [Sidenote: 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 ½: required the upper Height in English Feet.” [Sidenote: 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_. 353. 1st. Step. First, write down the Observation made on the Ground, or at the Bottom of the Mountain, thus: +Below.+ Barometer, 29 Inches 4 Tenths. attached Thermometer, 50 Degrees. Air Thermometer, 45°. 354. 2d. Step. Secondly, write down the Observation made at the Top of the Mountain, or upper Station in the Atmosphere, thus: +Above.+ Barometer, 25 Inches, .19 Tenths. attached Thermometer, 46°. Air Thermometer, 29½.