... the dew point by Daniell's dew point hygrometer and Regnault's condensing hygrometer, and by the use of the dry and wet bulb thermometers, as ordinarily used, and their use when under the influence of the aspirator, causing considerable volumes of air to pass over both their bulbs, at different elevations, as high as possible, but particularly up to heights where man may be resident, or where troops may be located, as in the high table-lands and plains of India; with the view of ascertaining what confidence ... — Up in the Clouds - Balloon Voyages • R.M. Ballantyne
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