CXXXVI. . §. H. BARRACLOUGH, 
As the steam enters the cylinder and strikes against the walls 
which have been chilled by contact with the previous exams 
steam, a portion of it, often reaching 30 or 40 and sometimes 50% 
is condensed and deposited probably in the form of a aan dew, 
this condensation goes on to a greater or less extent during the 
whole period of admission, after the point of cut-off ae been 
passed there is a co-existing condensation and re-evaporation going 
on, the former predominating as a rule only during the very early 
stages of the expansion and the latter towards the end ohiehe 
stroke. After the opening of the exhaust a sudden and possibly 
total re-evaporation takes place. During the final compression 
stage of the cycle preceding the admission of the steam, there may 
also be a twofold action, compressing the steam would tend to dry 
it and raise its temperature, but at the same time owing to a 
cylinder walls being at a lower temperature than the steam, sit 
would flow from the steam to the metal with a corresponding 
condensation of the steam. The best method of illustrating ee 
loss by cylinder condensation is probably the now usual one 
comparing the expansion line of an indicator card with the corres- 
ponding saturation curve, and so from the magnitudes of the 
volumes as indicated by the curves at any given pressure, deducing 
the “quality curve” of the steam . 
All the variable conditions of working will affect the amount 
of the loss by condensation, and a rough estimate may be formed 
of the effect which a change in one or more of these conditions 
will produce in any particular case. The conditions which are — 
usually assumed to be most potent in affecting the amount of the 
loss by cylinder condensation are— 
(2) Revolutions per unit time. 
(6) Steam pressures, and corresponding temperature ranges 
(c) Ratio of expansion, 
(2) Proportions and size of cylinder. 
(¢) Condition of the surface exposed to the incoming steam. 
(/) Clearance volume, csr at 
— g) Thermodynamic condensation, and indirect effect of same — 
