Moving Force. 237 
I.found no constant ratio to subsist between 
the diameter of the contracted: vein and that ' 
of. the orifice ;. and observing. considerable 
opacity. in the jet at, the, contracted vein, I 
~ 
concluded it to be divided ‘into.a number of — 
different. filaments, and I gave up all hopes of 
ascertaining the) actual-area of the section of 
the stream at that place by measuring its 
diameter... After repeated trials I found that 
when the water issued through a contracted 
hole, of the shape represented at G, the jet 
was quite transparent, and the ‘reaction 
(taking the mean of 12 experiments with 4 
different orifices) was less than the weight of a 
column of water of twice the height of the head 
and diameter of the smallest part of the hole, 
in the ratio of .865 to 1. The least reaction 
was as .85 to 1, and the greatest as .88 to 1. 
By measuring the quantity of water delivered 
in a given time, I found the velocity of the 
jet, at the smallest part of the orifice, to be less 
than that which a body would acquire in 
falling freely from B to C,in the ratio of 
94 to1. The highest ratio was as .95 to 1, 
and the lowest .89 to 1.* 
* Although these experiments were made since this 
paper was read before the Socicty, I have taken the liberty 
to insert the results, because they afford a good illustration 
of the principle which I have endeavoured to support. 
