on the
range of temperature in the cylinder, and not upon the density of the
steam or upon the extent of surface, and that its cause was probably
the alternate heating and cooling of a small body of water retained in
the cylinder. The effect of water, intentionally introduced into the
air cushion cylinder, corroborated the author's views, and he showed
how small a quantity of water retained in the cylinder would account
for the effects observed. At lower speeds surface might have more
influence. The favorable economical effect of high rotative speed,
_per se_, was very apparent.

In a trial with a compound engine, with 130 lb. absolute pressure, the
missing quantity at cut-off rose from 11.7 per cent. at 405
revolutions to 29.66 per cent. at 130 revolutions, the consumption of
feed water increasing from 20.35 lb. to 23.67 lb. This saving of 14
per cent. was due solely to increase of speed. Similar trials had been
made with a simple engine. In one simple trial at slow speed the
missing quantity rose to 44.5 per cent. of the whole feed water.

------------------------------+-----+------------+-------------+------+-------------+-------------+------
Intended mean | | | | | | |
admission pressure Lb.| 40 | 90 | 110 | 130 | 150 | 160 | 170
------------------------------+-----+------+-----+------+------+------+------+------+------+------+------
Simple, Compound, or Triple.| S. | S. | C. | S. | C. | C. | C. | T. | C. | T. | T.
Actual mean | | | | | | | | | | |
admission pressure Lb.|40.88| 92.65|87.54|106.3 |109.3 |130.6 |149.9 |151.9 |158.5 |158.1 |172.5
Percentage ratio of actual | | | | | | | | | | |
mean pressure, referred to | | | | | | | | | | |
low pressure piston, to | | | | | | | | | | |
theoretical mean pressure |98.2 |100 |91.3 |100.7 | 94.8 | 94.2 | 94.6 | 84.54| 95.9 | 85.3 | 85.2
Indicated horse power |16.51| 31.61|28.14| 33.5 | 33 | 36.31| 38.59| 35.69| 39.55| 35.56| 38.45
------------------------------+-----+------+-----+------+------+------+------+------+------+------+------
Feed water actually used per | | | | | |