--------------+--------------------+----------+----------+----------
| | Pressure | Pressure | Pressure
| | | |
/ | Experiment \ | / | 61.00 | 49.00
1½ in. < | > | 71.00 < | |
\ | Theory / | \ | 61.48 | 50.10
| | | |
| | | |
/ | Experiment \ | / | 55.00 | 45.00
1 in. < | > | 63.00 < | |
\ | Theory / | \ | 54.00 | 45.00
| | | |
--------------+--------------------+----------+----------+----------
In each case the unit of pressure is ¼ oz.

In the first trial there was a distance of 1½ in. between the jet and point
of its contact with the plate, while in the second trial this space was
diminished to ½ in. It will be noticed that as this distance increases we
have augmented pressures, and these are not due, as might be supposed, to
increase of head, which is practically nothing, but they are due to the
recoil of a portion of the stream, which occurs increasingly as it becomes
more and more broken up. These alterations in pressure can only be
eliminated when care is taken to measure that only due to impact, without
at the same time adding the effect of an imperfect reaction. Any stream
that can run off at all points from a smooth surface gives the minimum of
pressure thereon, for then the least resistance is offered to the
destruction of the vertical element of its velocity, but this freedom
becomes lost when a stream is diverted into a confined channel. As pressure
is an indication and measure of lost velocity, we may then reasonably look
for greater pressure on the scale when a stream is confined after impact