In the year 1835, Mr. Gurney proposed a lamp of great power in which the flame of oil or wax was sustained by streams of oxygen gas, a method said to be more economical than the combustion of oil in atmospheric air. The Trinity House entertained the proposal, and instituted a number of experiments. In applying this light to reflectors it is intended to use three small flames, each about three-eighths of an inch in diameter, productive, it is said, of an effect equal to that of ten Argand lamps. But for lenses the burner has seventeen films of flame, and is said to possess six times the power of the Fresnel lamp.
In the year 1840, Captain Basil Hall instituted a series of experiments to ascertain whether the well-known superior brilliancy of a revolving light could not be obtained for a fixed or continuous light, that is, for one equally visible in all directions at the same moment. His idea was, that by giving a certain velocity of revolution to a series of lenses round a fixed light, as in Fresnel's arrangement, a continuity of illuminative power, equal almost in brilliancy to that of a slowly revolving light, might be produced. The apparatus was arranged so as to cause a series of eight lenses one foot in diameter and three feet focal distance to revolve with any velocity up to sixty revolutions per minute round a central lamp. The light from this lamp being concentrated by refraction through the eight lenses into eight pencils, having a divergence of about eight degrees each, illuminated when at rest not quite fifty degrees of the horizon; but when this system of lenses was put into rapid motion, every degree of the three hundred and sixty degrees of the horizon became illuminated, so that to spectators placed all round the horizon the light would appear continuous and equally brilliant in every direction. The only question would be, whether or not this continuous light is essentially less intense than the light seen through the lenses at intervals when in slow motion; and this is a point which further inquiry must decide.
One of the causes which has tended to improve the brilliancy of lighthouses, has produced inconveniences, which long existed without remedy. During the combustion of a pound of oil, the union of its hydrogen with the oxygen of the air produces more than a pound of water in the state of vapour. When a cold wind is blowing upon the lantern of the lighthouse from without, this vapour is condensed into water upon the inner surface of the glass, and in very severe weather forms a crust of ice, in some cases, as much as four inches thick in the course of one night. This not only very much dims the brilliancy of the light to the sailor, but also entails a great amount of labour on the light-keepers, and injury to the lantern. The combustion of the oil also produces a large quantity of carbonic acid gas, which is of a very deleterious nature, and in many cases rendered the light-keepers' rooms almost uninhabitable. Under these circumstances, the Trinity House made application to Dr. Faraday to investigate the subject, with a view to the discovery of some remedy. With his usual skill and sagacity, Dr. Faraday instituted a number of inquiries and experiments, and visited some of the principal lighthouses. The result was the contrivance of a complete method of ventilating lighthouses. On the dioptric system, the remedy was simple: it was merely to erect a tall chimney over the central lamp, and lead it out at the roof; by which means, the draught of the lamp was improved, and all the products of combustion carried off. On the catoptric system, with revolving lights, each lamp was furnished with a chimney, which passed out at its upper extremity, through a small hole in the reflector into a fixed central hollow shaft, which served the purpose of a ventilating chimney to all the lamps. These plans are said to have been eminently successful in removing the inconveniences, which rendered the light less efficient, and the lighthouse an unwholesome and even dangerouse place of abode.