Experimental science. Elementary, practical and experimental physics (1890)
Hopkins, George M. (George Milton), 1842-1902 · New York, Munn & co. · leaf 194
If,for example, this tone corresponds to middle c, it is knownthat 261 puffs of air are made in the tube, and that sincethere are ten blades to the fans, the number of revolutionsof the fan shaft must be 261-{-10=26-1 per second, or 1,566revolutions per minute. In Fig. 173 is illustrated a siren… … Centrifugal Siren. through an opening in the top of the casing. The blades ofthe fan are arranged radially upon opposite sides of the disk,and the fan is encircled by a perforated rim, which fits thecircular casing and acts as a valve in cf)ntrolling the escapeof air. The perforations of the rim…
Physics · Lantern projection · Electric apparatus and appliances
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