| 2,600 lb. Ind. nut and slack coal, at $1·30 per ton | $1·69 |
| Engineer, one night, at $50·00 per month | 1·67 |
| Superintendent or electrician, one night, at $50·00 per month | 1·67 |
| Trimmer, one day, at $40·00 per month | 1·33 |
| 48 pairs of carbons, at $18·50 per month | 89 |
| Waste, &c., at $20·00 per year | 05 |
| Water rent, at $40·00 per year | 11 |
| Half-pint cylinder oil, at 60c. per gallon | 04 |
| One pint engine and dynamo oil, at 50c. per gallon | 06 |
| One day repairs on machine and lamps, including globes, at $120·00 per year | 33 |
| One day taxes on 50-light plant, assessed at $5,000, at 2¼ per cent. | 31 |
| One day interest on 50-light plant ($10,000), at 6 per cent. | 1·67 |
| Making a total of | $9·82 |
| 10½ d. or 20·45 cents. per lamp. £15 10 s. per annum. | |
If, in addition to the 50 street lights, 33 other arc lights are maintained, the total cost is reduced for a six hours’ run to $13·25, or £2 15s. 2d. for the 83 lights, 8d. or 15·96 cents per lamp, £12 3s. 4d. per annum.
[Table V]. has been calculated by M. Decker, of Nuremburg, and gives the comparative cost of working 150 lamps by electricity and by gas. The gas price (1) is that paid in Paris, namely, 6s. 9d. per 1000 cubic feet; column (2) is the price usually taken commercially, which includes the fixed charges. The price of electricity is given: 1st, when a steam-engine is available; 2nd, when it is necessary to lay down a special engine; 3rd, when a gas-engine is used the gas is charged at a trifle over the price in column (1).
Table V.
Total Cost per Hour and per Lamp.
- Legend for Table V.
- A = Number of hours’ work per year.
- B = Number of hours’ work per day.
- C = Steam-engine (existing).
- D = Hydraulic Motor.
- E = Steam-engine to be erected.
- F = Gas engine
- G = (1) Gas at 6s. 9d. per 1,000 ft.
- H = (2) Gas at 8s. 9d. per 1,000 ft.
| A | B | C | D | E | F | G | H |
|---|---|---|---|---|---|---|---|
| Pence. | Pence. | Pence. | Pence. | Pence. | Pence. | ||
| 500 | 1·38 | 0·485 | 1·055 | 1·216 | 0·418 | 0·552 | |
| 800 | 2·19 | 0·371 | 0·780 | 1·007 | 0·399 | 0·513 | |
| 1,200 | 3·29 | 0·314 | 0·608 | 0·865 | 0·380 | 0·352 | |
| 3,600 | 9·87 | 0·219 | 0·152 | 0·352 | 0·485 | 0·361 | 0·465 |
| Arc Lamps. | |||||||
| 500 | 1·38 | 5·235 | 4·246 | 10·459 | 11·485 | ||
| 800 | 2·19 | 3·971 | 3·089 | 7·552 | 9·272 | ||
| 1,200 | 3·29 | 3·087 | 2·441 | 6·004 | 7·581 | ||
| 3,600 | 9·87 | 2·185 | 1·510 | 3·591 | 5·586 | ||
Underground or Overhead Wires.
Apart from the unsightly appearance of overhead wires, there are many reasons why any extended system of supply of electricity should be carried out by underground cables. It is true that there have been no accidents in this country due to electric light wires falling, owing to the care bestowed on their insulation and erection; on account of the heat generated by the passage of the current through the leads no snow can accumulate on them, and therefore they are not subjected to the extra weight which destroyed so many of the telegraph and telephone wires in the last snow storm. Overhead electric light wires are exclusively used by the largest electric-supply company in London, and it is probable that, without further legislation takes place, other companies will shirk the expense of an underground system; and even a more dangerous method of running cables than that which has been condemned in the principal cities of the United States will become not the exception but the rule. In the city of New York the process of conversion of the present overhead to an underground system is a fact about to be accomplished to a very great extent at least, in the near future. Since July, 1887, the Western Union Telegraph Company have occupied the conduits, which have been constructed and laid with some 500 miles of wire; also the Metropolitan Telephone and Telegraph Company have 1000 miles of wire in the subways; and the Edison Illuminating Company, whose conductors were laid in the trench at the time of construction, has more than 1000 miles of underground cable. The plan adopted is to build conduits of section, as in [Fig. 30], which shows the subway in course of construction, with man-hole opening and exposed ends of conduits. The single tube at top is for distribution between man-holes, and some wires are shown entering the vault on the right from the service box in the foreground. The conduits are of various types; creosoted wooden tubes are placed in creosoted wooden casings; wrought-iron pipes are sometimes laid in asphaltic concrete with creosoted wooden box; another arrangement is to be of composition blocks on concrete, and cover them with brick—or wrought-iron pipe is lined with cement, and laid in hydraulic cement concrete and cased with creosoted plank. About 85 per cent. of all the conduits have been constructed on this plan, the interior diameter of the pipes being 2½ inches.