a. 
Date) oN 
Sete 
Gray’s Manual of Botany. 377 
In the view of the subject we have taken, it will cease to be a 
matter of surprise that the velocity of sound should be found to 
be greater than that assigned by Newton’s theory; as also, that 
the experimental velocities should be found to differ greatly 
among themselves, however carefully the experiments may have 
been tried. 
When the velocity of a pulse is given, we may find its inten- 
sity by the formula, A = 7 -H. We may find the maximum 
density, the natural density being 1, by the formula, max. dens. 
2 
= 3977' We may find the space occupied by a particle at the maxi- 
mum density, its natural extent being 1, by the formula, extent at 
max. dens. = “3° 
When the velocity is 1142 feet per second, if we put the sub- 
tangent H = 27818 feet, we have 
_ Intensity of the pulse, hk = 12937 feet. 
laximum density, 1-465. 
Extent of particle, 0-682. 
If we take for the given velocity, that which a body would ac- 
qure by falling through the subtangent, or that with which air 
would rush into a vacuum, we shall find A = H, and the parti- 
cles will be compressed into half their natural size, and the den- 
Sity will be double the natural density. 
A condensing force equivalent to the pressure of a column 
12937 feet high, and which compresses the particles into about 
tos Of their natural size, is a pulse “exceedingly intense” as com- 
pared with that which Newton supposes; but if our solution of 
the problem is correct, it is physically impossible that a pulse of 
less intensity should propagate itself in our atmosphere with a ve- 
locity of 1142 feet in a second. 
a nL 4 
Arr. XLITL—Review of a Manual of the Botany of the North- 
ern United Siates, by Asa Gray, M.D., Fisher Professor of 
Natural History in Harvard University.* 
Tue Opportunities for the study of botany are so gredt in this 
land of Virgin forests, and wide uncultivated fields, that it has be- 
rome with us a favorite amusement as well as source of know- 
* For the full title, see page 207 of this volume. 
