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to the total cost per unit will give some idea of the effect the number of lamp hours has upon this item.

Rate per unit due to interest, &c. -The low rate per unit in No. 1 (steam plant) is owing to the greater number of hours the installation is run. For instance, if the gas engine plant No. 2 was run for the same number of lamp hours, the cost would be reduced from 2.8d. to about 95d., or a total cost per unit of 1-8d. as against 14d. for steam (exclusive of boiler).

Total average cost.-In comparing the total cost per unit as herein given with the cost of energy from supply companywhich varies from 41d. to 8d. per unit-it must not be forgotten that to these latter amounts there must be added an additional sum for interest and depreciation upon the wiring and lamps, also renewals and transformer and meter rent, &c., which has been included in these costs of 1·4d., 33d. and 3.9d. respectively.

The interest &c. rate is made up of 5 per cent. interest (3 or 4 per cent. might be fairer) on first cost. ; 5 per cent. depreciation, cost of attendance, house rent, repair and renewals of lamps, &c., for portions under test.

DYNAMOS

No. 1 Plant.-24-unit four-pole compound-wound ‘Tyne' dynamo, belt-driven, by Messrs. Ernest Scott and Mountain, Limited; constructed to supply current for 400 16-candle-power incandescent lamps.

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No. 2 Plant.-24-unit two-pole compound-wound Tyne' dynamo, belt-driven; constructed to supply current for 400 16-candle-power incandescent lamps and set of accumulators for 100 16-candle-power lamps.

No. 3 Plant.-18-unit two-pole compound-wound 'Tyne' dynamo, belt-driven; constructed to supply current for 300 16-candle-power incandescent lamps.

No. 4 Plant.-16-kilowatt compound-wound dynamo, beltdriven; by Messrs. Lawrence Scott and Co. Output-152 ampères, 105 volts.

In the driving of dynamos a grave error is often made in the length of belt drive; people used to steam engine practice look to long drives as the correct thing-with the result that an excessive oscillation and wave motion is given to the belt, which seriously affects the running of the dynamo and the steadiness of the light.

The centres of engine and dynamo should not exceed 18 feet or be less than 12 feet.

INDEX

ABSORPTION, dynamometers to measure
the useful or brake horse-power of
engines, 170-172

Account, heat, amount of heat given to
a gas engine, 226-239

Acting, single, gas engine, 3-5

twin, gas engine, 5-6
tandem, gas engine, 6
Action in Otto engine, 3-6

in Dowson gas generator, 198-201
in Mansfield oil gas plant, 202

in Mansfield sawdust gas apparatus,
205

in Thwaite gas plant, 209-214
Actual horse power, 7

Air pump, Premier gas engine, 56-59
Diagram, 59

Air valves, 117-120

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