378 Review of Mr. Blake's Article on the flow of Elastic Fluids. 
The preceding notices embrace but a small number of the 
rarer minerals and undescribed localities in western North 
Carolina. On a future occasion the subject may be resumed, 
and additional facts and observations presented sufficiently in- 
oo it is hoped, to claim the attention of the scienti 
reader. 
Arr, XLIIL—Review of Mr. Blake’s Article on the Flow of 
Elastic Fluids ;* by Jount E. Henpricxs. 
Arter making some introductory remarks, the writer says: 
“Tf the velocity with which a fluid flows through an orifice be 
represented by V, the density under which it passes the orifice by 
D, and the area of the orifice by S, then the product VDS is the 
measure of the quantity of the fluid discharged in a given ume. 
It is an established law in the dynamics of fluids, that the veloc- 
ity of the flow is directly as the square root of the pressure, a0 
inversely as the square root of the density. If then the efficient 
pressure which produces the flow be represented by P, the ge 
law expressed by symbols will be 
VDS a DSvP : 5 (a) 
WD 
In order to prove that this formula does not properly represent 
the relation which the author intended it to represent, 1 will en- 
deavor to show that the formula (a) is only applicable to cases 
where P is a momentary force, and does not apply in the investl- 
gation attempted by Mr. Blake; and that, therefore, his determr 
nations are not to be relied upon as necessarily true. 
If a momentary force P impinge upon a body 4, it will give ' 
that body a velocity V and momentum m. And because oy 
effect is proportionate to its cause, we shall have maP. i 
Also, because the momentum of a body is that body multiph 
by its velocity, we = bv. (c) 
by substituting for m in (b) its value as found in (c) we 
have bY oP, or Va> (4) 
_ And if 6 represent a column of elastic fluid whose poe nen 
Section is 8; density D, and velocity V, the expression (d) 
i a P /P a when 
comes V a. B60 a2 . And w 
ST Spa’ Whence V it 17 iene : 
* Art, No, 12, Vol. 5, (second series) of the Am, Jour. of Science and Arts 
