35 
of the Motion and Resistance of Fluids. 
spouted out at the holes. In the former cases therefore there 
was no pressure against the sides of the pipes, but in the latter 
case there was. 
In respect to the motion of the fluid through any of the 
pipes, I found no difference whether I stopped the pipe at the 
end of the tube which enters into the vessel, in which case 
the motion began when the tubes were empty, or whether at 
the other end, in which case they were full at the commence- 
ment of the motion. That the fluid should flow into the top 
of the pipe faster than it would through an orifice, may pro- 
bably, in part at least, be owing to the adhesion of the fluid to 
the pipe, and be thus explained. Although the horizontal mo- 
tion of the fluid towards the orifice accelerates the velocity 
after it escapes from the vessel by contracting the stream, yet 
it must diminish the velocity at the orifice ; that is, if the same 
perpendicular motion were to take place without the horizon- 
tal motion, the fluid would flow out faster ; for as any motion 
in a fluid is immediately communicated in every direction, the 
horizontal motion will produce a motion upwards, and in some 
degree obstruct the descent of the fluid. If therefore this ho- 
rizontal motion could be taken away, or any how diminished, 
the fluid would flow out with a greater velocity. Now if a pipe 
be fixed, the fluid at the bottom of the vessel flowing towards 
the orifice will, by its adherence to the vessel, continue to ad- 
here to the sides of the pipe as soon as it arrives there, and 
by this means almost all the horizontal motion will be de- 
stroyed, and converted into a perpendicular motion, for the 
horizontal motion arises principally from the fluid which flows 
from and very near to the bottom, where the whole motion is 
very nearly in that direction. This motion therefore being 
Fs 
