The utility of lamps in domestic life, is universally acknowledged ; we shall, therefore, proceed to stats such patents as have been granted for the inventions or improvements relative to this branch of manufacture, without discussing those theories in which ingenious men have occasionally indulged. • The first we shall notice is, that of M. Argand, who obtained a patent in 1784 : his privilege being now expired, and his invention generally adopted, we shall briefly observe, that the superiority of his lamp depends on the admission of a larger volume of air to the flame, than is practicable on the common plan. This object is effected by employing a circular wick, so that a strong current of air rushes into the cylinder round which the wick is placed, and thus, together with the atmosphere, excites the flame to such a degree, that the smoke is entirely consumed. The light and heat are by this method remarkably increased, while the ex-pence of the oil is considerably reduced : because those particles, which, in the usual lamps, are di sipated in smoke, will, by M. Ar-gand's invention,be converted into a brilliant flame.
A patent was granted in 1787 to Mr. Miles, for his new method of making lamps of different forms, so as to emit an undiminished light. however it may be agitated; and which may also be fixed in halls, shops, etc-As its specification is too complex to be understood by those who are unacquainted with the manufacture, inquisitive readers will consult the 3d vol. of the Repertory of Arts and Manufactures.
Another patent was obtained in the same year, by Mr. Peter KeiR, for a contrivance of raising the supply of oil in lamps. The whole effect is produced by the application of another fluid, the specific gravity of which is greater than that of oil 3 and which communicates with the latter, by means of certain receivers, tubes, or conductors. These are so arranged, that the heavier liquid may press a column of oil upwards to any requisite height, for the purpose of supplying the lamp.
Farther, by prolonging the conductor of the heavier fluid beneath the lower surface of the column of oil, the weight of the former will hydrostatically act upon such surface, and raise the column. Thus, the lamp will not only be furnished with the purest particles of oil from the upper part,- but the flame will also be considerably elevated above the body of the vessel ; and, being supplied from a contracted surface of oil, it will consequently afford a more diffused light, with a considerable diminution of shade. For a more minute account of this ingenious contrivance, we refer the inquisitive reader to the 8th vol. of the work before quoted.
The last patent we shall notice, was granted in 1800 to Messrs. White and Smethurst, for their improved lamp-burner.- The whole is modestly called an improvement on the burner of the common Ar-gandlamp ; and the object of which is, to afford a more free and plentiful supply of oil to the ignited part of the wick; so that it will burn better, require less frequent snuffing, and answer we'll, even with oil of an inferior quality. These advantages are obtained simply, by leaving a larger than the usual space between the two tubes, within which the wick is placed. Yet it is necessary to contract such space towards the top, in order that the burnt crust or cinder may be more conveniently removed; an object which may be effected by applying a ring or piece of metal, conically or otherwise formed, so as to reduce the space in the upper part of the lamp to the usual dimensions.
The advantages of Messrs. White and Smethukst's improvement, are : 1. That the inconvenience hitherto complained of, respecting the mode of cleaning and dressing the lamps, is thus removed ; as, upon their plan, the capillary tubes of the cotton wick are prevented from being at any time obstructed by the viscid nature of the oil, while its ascent is promoted by such capillary attraction. 2. The quantity of oil consumed by these improved lamps is, by the patentees, stated to be less, in the proportion of at least four to five. 3. One of the most important advantages thence derived, is, that of the wick being rendered fit to burn common whale, or seal-oils, which are sold at about half the price of the best spermaceti oil, the only inflammable fluid hitherto used in Argand's lamps; while the former produce an equal degree of light.
We have already pointed out (in vol. i. p. 432, article Candle) the superior utility of lamps, especially for sedentary and studious persons; but as the light emitted by them is frequently too vivid for weak, or irritable eyes, we would recommend the use of a small screen, which should be proportionate to the disk of the flame, and be placed, at one side of the light, in order to shade it from the reader's eye , without excluding its effect from others, or darkening the room. Such a contrivance is equally simple and useful: it may consist either of paper, or taffcty, slightly gummed; and, being easily tolded and carried in the pocket, is far superior to the common screens.
We cannot conclude this article, without pointing out another circumstance in which lamps are superior to candles, namely, their cheapness. From experiments made some years since, with the express view of ascertaining the ex-pence of burning chamber-oil, it appears that a common taper-lamp, with eight cotton threads in the wick, consumed in one hour 325/1000 parts, or about one-third of an ounce of spermaceti oil, which at that time cost 2s. 6d. per gallon; so that the cxpence of burning for 12 hours, amounted to 4.57 farthings, or about 1 1/8 of. a penny. The light emitted by such lamp, was as clear and bright as that yielded by candles, which run from eight to ten in the pound.—Subsequent trials were made with M. Argand's lamp; the result of which was, that the latter will continue to burn three hours for the value of one penny. And though a candle, when newly snuffed, may appear to be preferable, yet the lamp is ultimately superior, both for steadiness and durability of light. Nay, one good lamp proved equal in its effect to half a dozen tallow candles, consisting of six in the pound, the expence of which was eight-pence, while that of the lamp amounted only to tivo-pence halfpenny, in the space of seven hours.