278 
POPULAR SCIENCE REVIEW. 
THE LOGOGRAPH, OR WRITING BY THE VOICE. 
By W. H. BAKLOW, F.R.S., V.P. Inst. C.E. 
LL articulated sounds made by the human voice are accom- 
panied by the expulsion of air from the mouth ; and in a 
series of articulated sounds the air is ejected in impulses which 
vary in quantity and pressure, and in the degree of suddenness 
with which they commence and terminate. 
It appeared to me that it would be interesting and probably 
useful, as tending to elucidate the process and effects of articu- 
lation, to construct an instrument which should record these 
pneumatic actions by diagrams, in a manner analogous to that 
in which the indicator-diagram of a steam-engine records the 
action of the engine. 
In considering a suitable form of recording instrument, the 
conditions to be met were : first, that the pressures and quan- 
tities were very variable, some of them being extremely small ; 
and, secondly, that the impulses and changes of pressure follow 
each other occasionally with great rapidity. 
It was therefore necessary that the moving parts should be 
very light, and that the movement and marking should be ac- 
complished with as little friction as possible. 
The instrument I ha,ve constructed consists of a small speak- 
ing-trumpet about 4 inches long, having an ordinary mouth- 
piece connected to a tube J- an inch in diameter, the other 
end of which is widened out so as to form an aperture of 
2J inches diameter. 
This aperture is covered with a membrane of goldbeater’s* 
skin or thin guttapercha. 
