e results of a series of experiments made
by Mr. James B. Francis on a Tremont turbine at Lowell, Mass., it
appears that there should be an efficiency of 72 per cent. if the
blades be equally well shaped in the steam as in the water turbine, and
that the clearances be kept small and the steam dry. Further, as each
turbine discharges without check into the next, the residual energy
after leaving the blades is not lost as it is in the case of the water
turbine, but continues into the next guide blades, and is wholly
utilized there. This gain should be equal to 3 to 5 per cent.

As each turbine of the set is assumed to give 72.5 per cent. efficiency,
the total number may be assumed to give the same result, or, in other
words, over 72 per cent. of the power derived from using the steam in a
perfect engine, without losses due to condensation, clearances,
friction, and such like. A perfect engine working with 90 lb. boiler
pressure, and exhausting into the atmosphere, would consume 20.5 lb. of
steam per hour for each horse power. A motor giving 70 per cent.
efficiency would, therefore, require 29.29 lb. of steam per horse power
per hour. The best results hitherto attained have been 52 lb. of steam
per hour per electrical horse power, as stated above, but it is
anticipated that higher results will be attained shortly. Whether that
be so or not, the motor has many advantages to recommend it, and among
these is the increased life of the lamps due to the uniform rotation of
the dynamo. At the Phoenix Mills, Newcastle, an installation of 159
Edison-Swan lamps has been running, on an average, eleven hours a day
for two years past, yet in that time only 94 lamps have failed, the
remaining 65 being in good condition after 6,500 hours' service. Now,
if the lamps had only lasted 1,000 hours on the average, as is commonly
assumed, the renewals would have amounted to double the year's cost of
fuel, as at present consumed.

The present construction of the motor and dynamo is shown in the
figures.

[Illustration: Fig. 1 though 6]

Fig. 2 shows the arrangement of 90 complete turbines, 45 lying on each
side of the central steam inlet. The guide blades, R, are cut on the
internal periphery of brass rings, which are afterward cut in halves and
held in the top and bottom halves of the cylinder by feathers. The
moving blades, S, are cut on the periphery of brass rings, which are
afterward threaded and feathered on to the steel shaft, and ret