188 THE BEST ARRANGEMENT FOR COMBINED 
stracted from the steam toreplace that lost in the low pressure cylinder during 
the exhaust stroke. The thermal lines cross each other twiceevery revolution. 
The turbine engine escapes this loss because the steam is continually 
moving in one direction on its way to the condenser, and the cylinder, or 
casing, and the rotor maintain a temperature that corresponds with that of 
the steam at any point on its way to the condenser. Mechanically, however, 
the turbine is defective, as a certain amount of clearance must be allowed 
between the tips of the rotor blades and the casing and also between the 
tips of the guide blades and the rotor. As these blades, at the high pressure 
end, are very short and the clearance has to be as great there as elsewhere, 
the free passage for steam at the high pressure end of the engine is quite 
considerable, especially in the marine type where the rotors are of greater 
diameter and the area of clearance correspondingly greater. Where the 
blade is only about one inch in length and with, say .o5 inch or .o6 inch 
clearance, we have over ten per cent of clear space for the steam to pass 
without doing work. At the low pressure end, however, where the blades 
may be ten inches long, the same clearance would only be one per cent. The 
escaping steam at the high pressure end is of course forced to do some work 
as its volume expands and the length of blade increases. 
I have just been trying to compare the data on a set of indicator cards 
from a triple expansion marine engine, the aggregate horse-power being 
5,600 divided as follows: high pressure cylinder 1,886 horse-power, inter- 
mediate pressure cylinder 1,874 horse-power, and low pressure 1,840 horse- 
power—these are sufficiently close to say that the power is divided equally 
among the three cylinders—with data from a marine turbine set consisting 
of a central high pressure and two wing low pressure turbines giving 5,500 
shaft horse-power, also practically divided evenly between the three shafts. 
No superheating in either case. 
In the reciprocating engine, the first stage or one-third of the total 
horse-power, is obtained by a drop in the pressure from 180 pounds absolute 
to 70 pounds absolute, being a drop of 110 pounds, corresponding to a drop 
in temperature from 372.9 to 302.9 or 70 degrees. 
In the turbine engine, the first stage or one-third of the total horse- 
power is obtained by a drop in the pressure from 175 pounds absolute to 35 
pounds absolute, being a drop of 140 pounds, corresponding to a drop in 
temperature from 370.8 to 259.3 or 111.5 degrees. 
In the reciprocating engine, the second stage or one-third of the total 
horse-power is obtained by a drop in the pressure of 70 pounds absolute to 
25 pounds absolute, being a drop of 45 pounds corresponding to a drop in 
temperature from 302.9 to 240.1 or 62.8 degrees. 
In the reciprocating engine the third or last stage is obtained by a drop 
in the pressure from 25 pounds absolute to 2 pounds absolute, being a drop 
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