148 
REPORT- 1847. 
Barker's mill, but has by most persons been passed over a* a mere plaj- 
thing, useless for practical purposes; it involves however principles of 
action, which, if well and scientifically carried out, will lead to mostiin- 
portant results. 
Dr. Barker’s mill consists of an upright pipe or tube, with a funnel-sbpel 
open top, but closed at the lower end; and from the lower end project tw# 
horizontal pipes or arms, also closed at the outer ends and placed opposiw 
to each other, at right angles with the vertical tube, so as to form actoa- 
Near to tlie end of cadi horizontal pipe, and on one side of it, is a rnuaii 
hole, the two holes being ojijxjsitc to each other. The upright pi[>® ** 
mounted upon au axis or spindle, and it is keiit full of water Howing iow 
the top. ‘ 
The w'ater issuing from iJie holes on opposite sides of the horizontal ariw 
causes the machine to revolve rapidly on its axis, with a velocity neatly 
equal to that ol’ the elfluent water, and with a force proportionate to the 
hydrostatic pressure given by the vertical column, and to the area of tin' 
apertures; for there is no solid surface at the hole on which the 
pressure can be exerted, while it acts with its full force on the opposite*”** 
ol the arm. (See the figure.) 
I his unbalanced pressure, according to Dr. Robison, is equal to the weijjt 
ot a column, having the orifice for its base, and twice the deptii 
surface of the water in the trunk for its height. 
Tins measure of the height may seem odd, because if the ori6ce«t^ 
d ut, the pressure on it is the weight of a column reaching from the suf 
f " issues with nearly the velocity acquired Jj 
m ^ quantity of motion produced is that of* 
Uiis length moving with this velocity. This is actually 
an pn..!Y P‘‘es8ure of the fluid, and must therefore be accompanied V 
an equal reaction. 
tbp constructed exactly os before described,moves r 
th! hnJln ri ^ descends in the vertical trunk, and then moving 
the horizontal arms partakes of iJie circular motion. 
arrn. hv*;?"'-"*'* exerted against the ends o 
arms by tl.e intervention of the fluid. ^ 
acro8s^he1rm Pressure, increasing for every « 
particle^ n/r tl*e proportion of its distance from tbe axis; and ■ 
pressed, with the accumulated centrifugal forces, of all the set 
