A snort time ago we gave some acount of the position of electric lighting. The day has passed when the electric -light cun be treated as a novelty, and one might as well expatiate on the wonders of the telegraph as on the surprising qualities of the most modern system of illumination, but the practical employment of the electric light for public places has hardly yet passed the experimental stage, while the question of its employment for private houses is still matter for investigation in the aciontific luburatory. Tt has now been proved beyond all possibility of dispute that open spaces and largo buildings can be lighted well and economically by means of the electric lit, bat the best system of lighting an undecided question. are differences between various systems which appeal to the eye of the public there are others which can be compre. hended only by those who have made scientific study of the subject. Just 8 every one.cau-recoguisa.a-diatinotion i between paddle-wheels and n propeller, but few unconnected with steamers know that the introduction of the compound engine almost revolutiouised steam navigation and rendered voyages easy which not long ago were looked upon as impracticable, so in electric lighting variations in the form and character of the lamps ure evident to all, while the peculiarities of the machinery by which the power is produced and of the means by which it is conveyed to the lamps are subjects whioh often fail to attract notice and the importance of which is not always recognised. It is true that the purchaser of anything, whether that thing be a certain amount of light or-a certain quantity of cloth, has little to do with the way in which the article which be purchases is produced, but in the case of the electric light almost every one is interested in the question of its applicability to domestic purposes, and is anxious to know how far, if at all, difficulties of this branch of the question lave been solved.
The last mail brings us intelligence of the fact that the principal streets in the city of London were lighted by the electric light on the 31st March, and notwithstanding the ominous date of the newspapers which record the fact, there is every reason to believe that the statement is correct. Some months ago three independent Companies undertook to light up three districts, the aggregate length of the streets to be dealt with being nearly three miles. Two of the Companies have commenced operations. Wo hear that Messrs. Siemens, who light up the London Bridge district, have adopted two descriptions of Inmps. One of these is used for the large open spaces, and the other for the streets. The Lump used for the open spaces is hung from a bracket on a post 80 fect high and there are reflectors placed above which render available a great portion of the light which would otherwise be wasted. In the district there are six of these lights, each of which is worked by 2 separate dynamo-electric machine. The smaller lamps used for the streets are placed about 20 fect high and have opal globes. There are twenty-eight of these Inmps, obtaining their electricity from two alternating carrot machines, each of which supplies the current for fourteen Inmps; ench of these machines is driven by a ten horse-power steam. engine and a similar engine is used to drive three of the dynamo-electric machines for the large lights, while two similar engines are kept in reserve in case of accident. As an experiment in street illumination this trial is most interesting, and as it is to Inst for a long time will give trastwortby results, but when it is remembered that for the purpose of lighting less than mile of streets, six steam engines, eight machines and eight sets of conductors are required; when it is remembered, that is to say, that so far from produc-ion of manufacture of light ely corresponds with the subdivisions of its employment, it will be seen how little ranson we have to lope for any modification of such a system being made applicable to household purposes, und how much more probable it is that that problem must be solved by going back to the first principles of electric lighting and taking an entirely fresh departure. The Blackfriars Bridge district is lighted by the Brush system. The length of streets is about a mile, and there are thirty-two lights. The lamps are placed about 16 feet above the ground, and some have opal globes while some have clear glass globes. The whole of those Inmps are lighted by one pair of conductors and the electricity is to be derived from one machine. At present two machines are used, bat they work together as one, This at first sight seems more to resemble what is wanted for domestic uso, but as a matter of fact this is hardly the case, It is true that by this system some of the lights can he shat off and the power intended for these lights can be distributed among the others, or all the power of the machine can be concentrated in one light, but this is not what is wanted for household use, It is difficult for. any one not acquainted with details to say when a difficulty. lies at the root of a system and when it lies on the surface. The difficulties in this case are many, but perhaps the clearest way of explaining the matter is to say that the great obstacle to: the general use of the light in the same way as gas is the extremely close dependence of, each light upon the condition of each of the other lights in the circuit and upon their number. Where the number is moderate and where, moreover, the lamps themselves are under the control of the parties who supply the light, such a difficulty is easily surmounted but not so where the light us to be carried into innumerable private houses, However successfal this attempt at street lighting may be, we venture to predict that it can have no very material effect on gas shares, and that the doom of gas as a domestic light has yet to be pronounced in the: pages of our scientific journals, and even. when the ples have been discovered on ie lighting by electricity can be accomplished, there may be years of grace for gas during the time the practical details are being worked out.
Text read from the printed page and cleaned; old type leaves the occasional error.