paper read at the Society of Arts, we have at last over-refined, and a fearful shipwreck has already been the result. The _Dunbar_, after making a prosperous voyage to our antipodes, was wrecked at the Sydney headland, within sight of her port. This dangerous cliff was surmounted by a reflector light which sent a thin disc of rays, under which the ship passed in a fog. Had a few divergent rays been allowed to light the danger at her feet, she would have escaped her fate. Another great and increasing difficulty arising from the limited capabilities of the present burners, is the fact that steamers are beginning to show lights as powerful as those exhibited in lighthouses of the inferior order and in the light ships. Hence a confusion is growing up between the fixed and the moving lights, which threatens to produce most disastrous consequences. As recently as February last, the _Leander_, an American barque, proceeding down St. George's Channel, saw a light which she mistook for that on the Tuskar Rock, and, when too late, discovered that it belonged to the screw steamer _North America_, which was coming right ahead. A fearful collision was the consequence, and the unfortunate ship with nearly all her crew was sent to the bottom. It has been found absolutely necessary to change the light in the Nore light-ship from a fixed to a revolving one, to distinguish it from the numerous powerful lights carried by steamers at anchor or when passing along the Thames. Various attempts have been made to increase the illuminating power of the burners. In 1832 Lieutenant Drummond proposed the use of the oxy-hydrous light, and as far as the intensity of light was concerned the new agent was perfectly successful, the Drummond light at seventy miles' distance appearing nearer to the spectator than the ordinary reflector light at twelve miles. But it was found impossible to maintain a steady light by this system, and it was therefore abandoned. Since then Professor Holmes has been making experiments with the magnetic electric light. The apparatus is said to consist of a series of very powerful magnets, around the poles of which the helices are made to revolve by means of a steam-engine. A powerful magnetic current is thus produced, which passing through carbon pencils shows a splendid light. The great difficulty of this and of other similar propositions to obtain the light by passing the current through two points, is to so regulate them that they shall always remain at the same distance apart, for any variation would immediately affect the intensity of the light. This desideratum has not yet been accomplished, neither do we think it possible of accomplishment. Professor Way has, however, we imagine, solved the problem by substituting a running stream of mercury in place of these points.