480 W. L. Stevens—Oryan-Pipe Sonometer. 
(d, d’) but makes it easy to mark off the division lines at their 
proper places. A longitudinal line divides its surface into two 
equal parts; that on the side toward the operator is marked off 
so as to give cord- mi gr for the natural scale, by changing the 
fractions 3, 4, 3, et , into decimals. e results are indicated, 
correct to three clave on the millimeter scale. ree octaves. 
in succession are thus marked off; the lines for the first octave 
ec TEMPESED 
LY NATURAL 
natural scale. These are marked off for two octaves, the lines 
extending half way to the edge. The other side of the central 
strip (¢ é , fig. 2) is marked off to give cord-lengths for the suc- 
cessive semitone intervals of the scale of equal temperament. 
These are easily calculated with the aid of a table of logarithms ; 
for since the twelve intervals of this scale are equal, the succes- 
sive vibration-numbers form a geometric series, in which the 
common ratio is 
r= 8/2 = 105946. 
The ee of this is the ratio for cord-lengths, and is 
ry’ = -94388. 
