280 
POPULAR SCIENCE REVIEW. 
change in the diagram, and that there are pneumatic actions 
revealed by this instrument which are imperceptible to ordinary 
observation. 
Before referring to the peculiarities of the diagrams, it may 
be desirable to say a few words on the quantities of air used in 
articulation. 
On reference to medical authorities/ it appears that the aver- 
age quantity of air expelled in one respiration is estimated at 
40 cubic inches, and that the total air-space of the lungs is 
estimated to average 110 cubic inches. 
I have ascertained by experiment that a balloon made of gold- 
beater’s skin, whose cubic content when full was 523 cubic 
inches, was filled with twelve ordinary respirations, or at the 
rate of about 44 cubic inches for each respiration. 
Also that by filling and emptying the lungs as completely as 
practicable, the 523 cubic inches could be filled with six respi- 
rations, or about 88 cubic inches for each respiration. 
I also made the following experiment to ascertain the average 
quantity of air used in pronouncing syllables. 
Using the same balloon and speaking into an elastic tube 
communicating with it, I read from a book until the balloon 
was filled, taking care to close the elastic tube when it was 
necessary to take breath. 
The results were as follows : — 
Time required. 
No. of syllables. 
Cubic inches® 
84 seconds 
353 
523 
84 
353 
523 
From another part of the book 90 
u 
364 
523 
„ ^5 
}) 
364 
523 
Mean .. . 86 
>) 
*359 
*523 
Showing an average of about 1^ cubic inch of air for each 
syllable, and rather more than four syllables per second, in- 
cluding stops. 
Without stops, from five to six syllables can be pronounced 
in a second. 
The lungs appear to be capable of exerting considerable 
pressure in the expulsion of air ; but distinct articulation 
