--------+------+--------+--------+---------+---------+-------+------ | | | | | | | 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