56 FE. W. Blake, Jr.—Articulate Vibrations. 
tuning fork (Ut 83—512 v. s.) provided with a pointed wire. = 
every case more than 200 vibrations were counted and m 
ured, and careful comparisons made between the earlier id 
later ones, so as to be certain of the uniformity of the motion. 
From the description it will be evident, that when the car- 
riage atone isin motion a straight line will be photographed upon 
the plate. On speaking into the mouth-piece the disc is set in 
vibration, each movement causing change of angular position 
of the mirror, the reflected light moves through twice this 
angle, and the resulting photograph gives us the combination 
of its motion with that of the carriage.* 
The general character of the curves obtained is shown in the 
accompanying figures, which are about one-half (0°56) the actual 
size of the originals. The reduction was accomplished by pho- 
tography on the wood itself, so that the skill of the engraver 
was employed simply to follow the lines, which he has done 
with prot fidelity. 
he velocity of the carriage for the vowel-sounds was 214, 
for Beats University, 40, and for How do you do, 14 inches per 
secon 
In the mathematical discussion of these curves the 7 
are measured by the known velocity of the carriage, and se 
to determine the pitch, the ordinates represent the amplitude of 
vibration of the center of the disc, magnified 200 times in the 
photographs. The “peer of scale makes the magnifying in 
the wood-cuts only 112 tim 
The ordinates are not strictly straight lines, but parts of the 
vertex of a parabola, and closely approximate to circular ares 
whose radius is the cay banal of thelensemployed.t In the 
figures given, the centers of curvature of these arcs is at the 
right hand. 
With an ordinary tone of voice an amplitude of near ge 
inch is obtained, implying a movement of the center o 
dise of “005 inches as determined by actual measurement. 
By varying the atealorating weight and its fall, any ma 
able. velocity may be given to the pemaess Each syllable 
requires for its arti about one of asecond, hence 
run from right to left The negative (examined from the 
}It can easily be shown that at the reflected beam describes the envelope of 
cone, Boon eae an angle of 90°, and whose axis is inclined 45 Be ag to 
reflect the beam almost directly Wor on an path: asa having the sensitized plate 
move up and down in a vertical plane. 
