one of the utter unreliability of such rules for general
application. It is, for instance, well known that many machines, when
under test, have demonstrated that the total increase in the water rate
is very far from constant. A machine tested, for example, gave
approximately the following results, the object of the test being to
discover the total increase in the water rate per inch decrease in
vacuum:

From 27 inches to 26 inches, 4.5 per cent.

From 26.2 inches to 24.5 inches, 2.5 per cent.

This illustrates to what an extent the ratio of increase can vary, and
it must be borne in mind that it is very probable that the variation is
different in different types and sizes of machines.

There can exist, therefore, no empirical rules of a reliable nature upon
which the tester can base his deductions. The only way calculated to
give satisfaction is to conduct a series of preliminary tests upon the
turbine undergoing observation, and from these to deduce all information
of the nature required, which can be permanently recorded in a set of
curves for reference during the final official tests.

In conclusion, it must be admitted that many published tests outlining
the performances of certain makes of turbine are unreliable. To
determine honestly the capabilities of any machine in the direction of
steam economy is an operation requiring time, and unbiased and accurate
supervision. By means of such assets as "floating quantities," short
tests during exceptionally favorable conditions, and disregard of the
vital necessity of running a test under the proper specified conditions,
it is comparatively easy to obtain results apparently highly
satisfactory, but which under other conditions might be just the
reverse. These considerations are, however, unworthy of the tester
proper.

VII. AUXILIARIES FOR STEAM TURBINES[6]

[6] Contributed to _Power_ by Thomas Franklin.

The Jet Condenser

The jet condenser illustrated in Fig. 72 is singularly well adapted for
the turbine installation. As the type has not been so widely adopted as
the more common forms of jet condenser and the surface types, it may
prove of interest to describe briefly its general construction and a few
of its special features in relation to tests.

[Illustration: FIG. 72]

Referring to the figure, C is the main condenser body. Exhaust steam
enters at the left-hand side through the pipe E, condensing water
issuing through the pipe D at the opposite