206 On the Propagation of Sound. 
blished law of pendulous bodies, we find the time in whichi it 
will make one vibration 91-766 seconds. But as the pendulum 
performs its going and return in the same time that an undula- 
tion moves forward over a space which ees e the velocity 
of sound in a second; therefore 91°766 x 2= 183-532 seconds ; 
and the space passed over in this time is the LO: rence of a 
circle whose radius is 27541 feet. 
Therefore a a a = 942-9 feet, the velocity of 
185°532 
sound in a second, according to Sir I. Newton’s method of cal- 
culation. 
To account then for the wide difference that exists between 
the numbers as deduced from this theory, and actual experiments ; 
Newton makes surmises very much beneath his usual penetra- 
tion: he first supposes the crassitude of the solid particles of the 
air, and the intervals between those particles, to be in proportion 
to their diameters as 1 to 8 or 9, and from this source he aug- 
ments the velocity 109 feet. Still the velocity is deficient ; and 
to account for it, he next takes in the vapours floating in the 
atmosphere, as being of a different tone from the air, and con- 
jectures their proportion to be to that of the air as 21 to 20; 
and these vapours are calculated to accelerate the progress of 
sound in that ratio; thus increasing the velocity to 1142 ina 
second, or until the velocity from theory agrees with that ob- 
tained from experiment. That these conjectures are not even 
plausible, the most ardent admirers of Newton must admit. In 
the first place, the proportions of the diameters of the particles 
of air to the intervals between them are merely imaginary, and 
the quantity of vapours calculated as existing im the atmo- 
sphere is absolutely erroneous. If Newton failed ultimately, in 
this problem, to anticipate the law of nature, the superstructure 
is raised upon an unerring base that can never fail. He had done 
pe for glory; and the specks upon his fame are, like those 
upon the luminary of day, invisible to the unassisted eye. But 
while we admire the greatness of the man, let us not tamely follow 
his splendid path; the perfection of philosophy requires the un- 
biassed assistance of the highest fights of human itellect, con- 
ducted by reason, and completed by experiment and reflection. 
The theory of La Place, though highly ingenious, is nevertheless 
very improbable. That a momentary evolution of caloric should 
take place during every vibration in the aérial medium, we can- 
not imagine. But allow! ing it really to be the case, though the 
evolution of caloric might be separated with such rapidity as to 
escape our means to detect it from a single tremor of the air; 
yet I sav that a sonorous body, kept in‘a continual state of vi- 
bration, must finally render the separation of caloric evident to 
the 
