. Compendium of meteorology. Meteorology. EXPERIMENTAL CLOUD FORMATION 1257 against any great rise of temperature at the top of the chamber. In a series of experiments carried out by Chandra [4] at the Imperial College of Science and Technology, South Kensington, London, a chamber so constructed was used, and the top of the chamber was supported on a series of brass cylinders, sets of such cylinders being made of lengths from 2 to 16 mm. The sides of the chamber were filled in by layers of felt, sufficient to prevent a rapid leakage of air into or out of the chamber. In Chandra's experiments t
. Compendium of meteorology. Meteorology. EXPERIMENTAL CLOUD FORMATION 1257 against any great rise of temperature at the top of the chamber. In a series of experiments carried out by Chandra [4] at the Imperial College of Science and Technology, South Kensington, London, a chamber so constructed was used, and the top of the chamber was supported on a series of brass cylinders, sets of such cylinders being made of lengths from 2 to 16 mm. The sides of the chamber were filled in by layers of felt, sufficient to prevent a rapid leakage of air into or out of the chamber. In Chandra's experiments the temperature of the air was measured by means of platinum resistance thermometers, fixed as near as possible to the top and bottom plates respectively, while a third was fixed halfway between the plates. Observations of the tem- perature distribution within the chamber could thus be made at any time. The motion within the chamber was made visible by means of cigarette smoke, which was injected by means of a two-way pump. The motion could be watched and photographed through the top plate. As might be inferred from Rayleigh's formula, no motion was observed until the excess of temperature at the base over that at the top exceeded a finite limit. Thus, mth a chamber of depth 10 mm, the critical temperature difference was Observations were made with depths from 2 to 16 mm. Figure 3 shows the structure found in a chamber of depth 8 mm, with a temperature difference of 28C. 0 1 E 3 4 5 CM . SCALE,,. : Fig. 3.—Convection pattern in a chamber of depth 8 mm; temperature difference between top and bottom of chamber, 28C. between top and bottom of the chamber. This shows a series of polygonal cells, in each of which the motion was do'ft'nward at the centre, upward at the outer margin, and inward at the top. In addition, there are some long rolls which fill the chamber when the smoke is first injected, and which gradually break up into separate polygonal cells. This feature was
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