54 E. W. Blake, Jr—Articulate Vibrations. 
Art. VIL—A method of recording Articulate Vibrations by mean 
Z Photography ; by E. W. Buakg, Jr., Hazard Professor of 
Physics, Brown University. 
E extreme minuteness of the vibrations of the iron disc of 
the Bell telephone withdraws them from all ordinary methods 
of observation and measurement. A pointed wire fastened to 
the center of a ferrotype disc 24 inches in diameter, and mov- 
ing on smoked glass, gave ;'; inches as the extreme ampli- 
tude of vibration under a powerful impulse of the voice, 
while sounds moderated to such a point as to be fairly articu- 
late, were with difficulty Sica by the movement which they 
communica 
Animal membran nes, possessing greater flexibility than the 
metal disc, seemed to promise better results, but the inertia of 
the attached wire, and the resistance offered by the smoked sur- 
face, become o importance, and throw doubt on the accuracy 
of the seni: sich ait Dr. Clarence J. Blake employs the 
human membrana tympani as a logograph,* and has obtained 
very beautiful aed interesting tracings. I find by sapraete, 
of some, which he kindly sent me, that the number of vib 
tions as rpc! atte ae considerably below the baeaay | ree ot 
Ps as 80 per secon 
hae logo a “daseribed by W. H. Barlow, F.R. a in a 
fa beter’ the Royal Society,f serves to record the 
var ae pressures of the expelled air taken as a whole. 
With a single exception the diagrams give no suggestion of the 
musical character of the sounds. The width of the line drawn 
by a camel’s hair brush and the slow movement of the paper 
would mask the minute vibrations even if the apparatus were 
otherwise adapted to showing them 
The opeioscope, invented by Professor A. E. pee con- 
sisting of a tense membrane, to the center of which a small 
mirror is seanel | is well adapted to proving the aes of 
ae sap in human speech, but not to determining 
their 
The dooce at of Mr. Edison records on tin-foil enough 
of the vocal elements to reproduce intelligible articulation. 
The minute indentations are therefore a record of great scientific 
value. In the hands of Mr. Fleeming Jenkin they promise to 
lead to valuable results} in the analysis of vocal sounds. 
Dr. S. Th. Stein§ described in 1876 a method of photograph- 
* Archives of Opthalmology and Otology, vol. v, No. 1, 1876. 
in the Po Science Review, 1874. 
{Nar May 9th, tea Atane on Phonograph by Mr ys J. Ellis. 
Annalen, Bd. clix, 
