. Report of Private Expedition to Philippeville, Algeria, to View the Total Eclipse of the Sun, August 30, 1905 . (b) Thermometric observations: (1) The air temperature, read froma standard mercury thermometer (°F.), in the shade, about 4 feet from theground. The readings are reliable to 0°-l C. (2) A standard ^black bulb in vamio solar radiation thermometer,wishielded, and therefore showing, in addition to the solar, the radiationfrom the sky, and surrounding objects. This was fastened to the telescopestand in a fixed position, so that the sunshine fell on the bulb uninter-ruptedly from sunri
. Report of Private Expedition to Philippeville, Algeria, to View the Total Eclipse of the Sun, August 30, 1905 . (b) Thermometric observations: (1) The air temperature, read froma standard mercury thermometer (°F.), in the shade, about 4 feet from theground. The readings are reliable to 0°-l C. (2) A standard ^black bulb in vamio solar radiation thermometer,wishielded, and therefore showing, in addition to the solar, the radiationfrom the sky, and surrounding objects. This was fastened to the telescopestand in a fixed position, so that the sunshine fell on the bulb uninter-ruptedly from sunrise to sunset. The readings are accurate to 0°1 C. In the curves on Plate 5, no allowance has been made for this lag ofthe instrument in giving its indication, but on the mfaraie radiation timecurve, fig. 5, such an allowance has been made, based on the results ofa direct comparison of the instruments indications with those of a thermo- -^ -*•- Actual recbding- of aolar radiation thermometer, unscreened. --<^ o- The above reddings diminished btj the corresponding fall of air (shade) fcemperaCure. 98-a. tJO 55 jo 3 t 40** I 35 30 3Q 40 11 10 20 30 40 S? Charles mean b1me» z*e Fm 5. V UJj. ■ ■ 306 Dr. Porter and Mr. Coif ox. Expedition to [Nov. 27, pile, during an artificial heat eclipse, made roughly to imitate the indications during the first and last part of the covering and uncoveringof the suns disc seem to have heen approximately 8 minutes late. (c) Measurement of the relative humidity of the air. The dry and wetbulb method was followed with the usual precautions. The apparatuswas placed about 4 feet above the ground, the thermometers shielded from allbut light airs, and kept always in the shade. In every case the relativehumidity has been derived from the readings by means of the formula— Relative humidity = ^ -^^T^.b -T^.b,) ^ ^^go, where = Tension of aqueous vapour at wet bulb temperature,and , = jj )? dry „ whi
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