The formulÆ employed are— | d | | (1) tan φ = | ----- | | r | | | 2592000 × D × n | | (2) V = | ----------------- | | φ | | | φ = | angle of deflection. | | d = | corrected displacement (linear). | | r = | radius of measurement. | | D = | twice the distance between the mirrors. | | n = | number of revolutions per second. | | α = | inclination of plane of rotation | | d = | deflection as read from micrometer. | | B = | number of beats per second between electric Vt fork and standard Vt3 | | Cor = | correction for temperature of standard Vt3. | | V = | velocity of light. | | T = | value of one turn of screw. (Table, page 126.) | Substituting for d, its value or d×T×sec α (log sec α = .00008), and for D its value 3972.46, and reducing to kilometers, the formulÆ become— | | dT | | (3) tan φ = | c | ----; | log c = .51607 | | | r | | | n | | (4) V = c ---; | log c = .49670 | | φ | | | D and r are expressed in feet and d in millimeters. | | Vt3 fork makes 256.070 vibrations per second at 65° Fahr. | | D = | 3972.46 feet. | | tan α = | tangent of angle of inclination of plane of rotation = 0.02 in all but the last twelve observations, in which it was 0.015. | | log c = | .51607 (.51603 in last twelve observations.). | | log c = | .49670. | The electric fork makes ½(256.070 + B + cor.) vibrations per second, and n is a multiple, submultiple, or simple ratio of this.
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