He says
that the waste spaces in his modification were much smaller than in
the Cockerill compressor, while the efficiency of the apparatus was
largely increased. The actual engine duty per horse power and per hour
was raised, as a maximum, to 384 cubic feet of air at atmospheric
pressure, and compressed to 90 lb. per square inch, a marked increase
on the duty of the compressors in use at the St. Fargeau station. The
Cockerill compressors experimented on at the same time showed a
maximum duty of 306 cubic feet of air. A considerable advantage is
claimed in drawing clean and cool air from the outside of the
building, and beyond the main feature of carrying out the compression
in two stages, Mr. Riedler appears to have shown great skill in
introducing several minor alterations and improvements in the plant.
[Illustration: EFFICIENCY CURVES FOR THREE TYPES OF COMPRESSORS. (Fig.
8, 9, 10)]
Figs. 8, 9 and 10 are diagrams showing the comparative efficiency of
the three types of compressors at St. Fargeau--Fig. 10 being a diagram
of the Riedler compressor--and indicate the gain derived from the
intermediate cooling. The loss is shown to be only 12 per cent., as
compared with a loss of 43 per cent. in a large part of the plant, and
of 105 per cent. in the earlier compressors of the St. Gothard type.
The table given herewith contains a summary of trials made by
Professor Gutermuth, and are intended to show the comparative results
of an extended trial with three kinds of compressors at St.
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