lime light, electric light, magnesium, and gas. Sir William Thomson, however, considers that "the lighthouse of the future is to be illuminated by gas, except when the situation is on an isolated rock, or where, for any reason, the price of coal is prohibitory." Professor Tyndall coincides in this opinion, and in a paper by Mr. Wigham, gas engineer, we find that this theory has been put into practice by the Irish Board of Lights at Howth Bailey, in Dublin Bay, where an actual saving has been effected by the substitution of gas for oil. The most beautiful and interesting, perhaps, of all lights, is that discovered by Professor Faraday, the electric light. It is really nothing more than the white heat caused by the meeting of two opposing electrical currents, generated by a powerful machine, and conveyed by two copper wires, each terminating in a carbon point. These points are kept at a certain distance from each other, and when the two opposing currents meet there, the resistance of both causes the carbon to glow and become white hot; the incandescent state of the carbon is the brilliant electric light itself. It was utilized by Mr. Holmes, who invented an apparatus for producing it, which was tried in 1859 at the South Foreland lighthouse; it has, however, only been steadily used for six years, but has proved itself so successful that it merits a somewhat detailed notice. The stream of electricity which supplies the two lighthouses standing one above the other on the chalk cliffs of the South Foreland promontory, is not derived from a pile or a battery, but is ground out of huge magneto-electric machines worked by a twenty horse-power steam engine — the current being conducted by wires from the machine-house to the lighthouses. The light generated by this beautiful contrivance is kept constant by means of a clockwork arrangement which draws the carbon points closer together as they disperse themselves by combustion; it is necessary, however, to change them-altogether every three hours, but as this is accomplished by the keeper in a few seconds, no real inconvenience is experienced. The cost is a more serious consideration, for we are told, while three keepers suffice for an ordinary lighthouse, a staff of eight men is constantly needed to sustain the electric light at the South Foreland.
A large majority of lights on the British coast are fixed, but a considerable number are revolving. Sir William Thomson considers the present system of lighting very far from perfect, and would have all lighthouses so distinguished that they could not possibly be mistaken for ship or shore lights. He recommends the abolition of lights revolving at different intervals, which, he says, are often mistaken on a stormy night, and the adoption of Morse's telegraph signs. Each lighthouse should have its own letter, which it should show incessantly from sunset to sunrise by means of Morse's dots and dashes, this being accomplished by a simple mechanical contrivance which would drop a screen before the gaslight, eclipsing it at intervals, thus by light and darkness showing the letters on Morse's plan; the length between the dots and dashes indicated by intervals of darkness, the dots and dashes themselves, that, is the letters, by short and long flashes; this is called an occulting light. The originator of this idea was Babbage the mathematician, and his paper on the subject maybe found by the curious in the pigeon-holes of Trinity House, though warmly approved of by such high authorities as Professor Tyndall and Sir William Thomson, the latter of whom has invented an eclipsing gaslight to be employed in lighthouses, which was exhibited at a conversazione of telegraph engineers on December 2nd, 1874.
This branch of scientific discovery is, like so many others at the present day, still capable of further development, and the perfection and extension of the labors of our savants will doubtless furnish a theme of interest to the future historian of scientific research, and its practical application to the wants of commercial navigation. A. G.
BOOKWORMS.
In the long and bitter struggle for supremacy which has gone and is still going on between the bookish few and the unread many, we must reckon to the score of the latter two signal advantages, when, in times past, they invented the terms "bookworm" and "blue-stocking." These were immense achievements, such as their opponents could scarcely match, and all the more noticeable because the party from which they have proceeded is, as a rule, the inarticulate one. Such an instance of the force of expression whereby it has once upon a time delivered itself is a measure of the feeling which lies smoul-
