181 



LIGHTS, ARTIFICIAL. 



LIGHTS, ARTIFICIAL. 



granted or acquired in property by any. On the other hand, as he 

 who acquires the fee .simple of land has a right extending ab inferis 

 ad mperos, from the earth's centre to the heights of heaven, he may 

 prima facie build as high as he will, and dig as low as he chooses at 

 the very verge of his domains. The user of the surface of his land 

 therefore cannot lawfully be in any other without his consent. But 

 if such a user exist, and is of long standing, it is for the interest of 

 society that individuals who have gradually formed their habits and 

 arrangements, and may have incurred expense, and founded contracts 

 with others in accordance with this privilege of user, should not after- 

 wards be capriciously disturbed therein. 



It is obvious, that a neighbour's window existing in a wall built to 

 the verge of the adjoining domain, presupposes an access of light to it 

 over the other's land, which he may refuse his consent to, and obstruct 

 by buildings on his own soil. If he do not expressly dissent, and if he 

 do not expressly grant the user for a limited time, and still the user 

 goes on, which is the more common case, the question is whether ever 

 there shall be a time when such user cannot be obstructed. To say 

 that that which began in no right shall by mere length of time become 

 a well established right recognisable in law, is too plainly untenable in 

 point of reasoning to be asserted. Yet the convenience of society 

 required provision to be made for such a result. The judges then, at 

 common law, perceiving this necessity existing not without moral 

 rectitude to justify it, surmounted the difficulty by a fiction ; they 

 instructed the jury that from length of uninterrupted user they might 

 presume it to have originated in an unqualified grant of the proprietor 

 and find then- verdict in his favour who claimed the continued access 

 of light. 



The length of time necessary to justify such a presumption, through 

 uniformity of decision, until it had become a received rule, came to 

 be twenty years. The neighbour's window after so long a time becomes 

 an ancient light. Precision was afterwards given to the practice of 

 the courts under this rule by an Act of Parliament, the 2 & 3 Wm. 4, 

 c. 71, aec. 3 et seq., enacting that after 20 years' uninterrupted enjoy- 

 ment, the user becomes an indefeasible right, and nothing shall be 

 deemed an interruption to defeat such acquisition of right, unless it 

 has been submitted to or acquiesced in after notice of the act, and of 

 the person authorising it, has reached the person who claims the right. 



The right to the free enjoyment of light belongs in the Roman law 

 to the class of Servitutes (easements), among which were the Serritus 

 nun tollendi, ne liiminibiu officiatur, ne prospectui officiatur (' Dig.' 

 8, tit. 2, . 11, 12, 15-17). The general rule is thus expressed by 

 Ulpian : " He who shall attempt to obstruct his neighbour's lights, or 

 to do anything else to damage them, must know that he ought to 

 maintain the form and condition of the ancient edifices. If you and 

 your neighbour cannot agree about the height to which buildings may 

 be raised which you have begun to erect, you will have the privilege 

 of having an arbiter." 



The stopping of a prospect is not a nuisance by the law of England, 

 but by the Roman law there was a remedy even in that case, ne prus- 

 pectui officiatur. 



LIGHTS, ARTIFICIAL. Most kinds of artificial light, for domestic 

 and manufacturing purposes, are produced by the combustion of coal, 

 solid tallow, liquid oil, or some sort of spirit. One special kind, due 

 to the action of an electric current on charcoal, is described under 

 ELECTRIC LIGHT ; another, produced by the action of oxyhydrogen gas 

 on lime, is treated under DRUMMOND LIGHT ; a third, of which the 

 peculiarities are due rather to the apparatus than to the combustible 

 substances, noticed under LAMP, SAFKTY ; while gas-lights are fully 

 treated in the articles GAS, MANUFACTURE or ; and GAS-LIGHTINO. 



Candles. These, in the different varieties of dip tallow, moulded 

 tallow, wax, palm oil, composite, stearine, &c., are described in their 

 nature and production under CANDLE MANUFACTURE. We may here 

 simply notice the Suho lamp, patented a few years ago, for burning 

 solid tallow or some other kind of fat. The tallow is brought to the 

 form of a long cylinder like a candle without a wick, and is placed 

 in the vertical stem of the lamp ; there is a spiral spring beneath it, 

 which presses it up close to a conical cap or cover at the top. A fixed 

 tube passes up through the centre of the cylinder of tallow, from 

 top to bottom ; and in this tube is placed a cotton wick dipped in wax, 

 the height of which above the top of the tallow can be regulated by a 

 rack, pinion, and nut. The tallow or fat is made into a hollow cylinder 

 in order to leave room for the central tube containing the wick. When 

 the lamp is to be extinguished, the wick is drawn down below the top 

 of the tube, and again raised before the tallow becomes cold. 



One of the projects of this class consists in placing any kind of 

 wax or tallow or fat in a receptacle, having either hot water or hot 

 metal beneath it, so as to keep it in a melted state, fitted to be used 

 in, the same manner as oil ; but any method of keeping the water or 

 the metal hot would seem likely to be a far greater inconvenience than 

 any supposed good arising from the use of a solid food for the lamp. 

 In another contrivance, however, where the substance employed is 

 either lard or tallow, there is a piece of metal which descends from the 

 flame into the vessel containing the lard ; and this metal, becoming 

 heated by the flame, communicates this heat to the lard, and thus 

 keeps it in a melted state. The inconvenience of such arrangements 

 arises from the circumstance that the hot water or a heated piece of 

 must bo put into the lamp before lighting it, iu order to melt 



the tallow. When this preliminary step is taken, the tallow is kept in 

 a melted state by various means. One ingenious mode consists in 

 having an air-tube within the wick, to carry air up to the flame, and 

 two projections from this tube penetrating into the flame itself ; so 

 that the metal- of which the tube is made, becoming heated at the 

 xipper end, speedily communicates heat to the contents of the lamp 

 below. 



Bude Light. As something intermediate between gas-light and oil- 

 light, we may notice the Bude light, devised and named by Mr. Golds- 

 worthy Gurney. Originally the light was obtained from an oil-lamp, 

 the flame from which was acted on by a current of oxygen gas : sub- 

 sequently oil-gas was substituted for the liquid oil ; but afterwards the 

 gas which is made for lighting the streets of towns was employed to 

 produce the flame, the brilliancy being increased by a current of atmo- 

 spherical air ingeniously introduced. The apparatus being suspended 

 from the ceiling, the gas, either as it comes from the street or purified 

 by chemical processes, passes up a number of short tubes into con- 

 centric annular receivers, the upper surfaces of which are pierced on 

 the whole of their circumference with small holes. On issuing from 

 the perforations the gas is ignited, and thus there are formed as 

 many cylinders of flame as there are rings ; while between and abound 

 the several cylinders the atmospheric air rises from below to support 

 the combustion. A hollow frustum of a cone, of glass, open at 

 both extremities and having its larger end downwards, surrounds 

 the tubes above mentioned ; its lower part resting on the base of the 

 framework within which they are suspended, and its upper part 

 approaching very near the bottom of the flame, so that the atmospheric 

 air in rising is confined between the upper or smaller end of the cone 

 and the flame. The distances between the cone and the rings, and 

 between the rings themselves, are regulated by experiment so that the 

 quantity of air may suffice to bring the temperature of the gas to 

 exactly the degree necessary for causing a separation of the charcoal 

 from the flame, as nearly as possible at the moment that the latter 

 issues from the perforations. The flame from each interior ring serves 

 to augment the heat of that which is on the exterior of it, by which 

 means an increased intensity of light in each is produced ; and almost 

 the whole of the light that emanates from) the interior rings passes 

 through the flame on its exterior, into the apartment. A cylindrical 

 glass chimney rests at its lower extremity on the margin of a circular 

 aperture in the middle of a circular disk of iron, from 1 8 inches to 

 2 feet in diameter, the under surface of which serves as a reflector : 

 this disk, and with it the chimney, is capable of being raised or lowered, 

 by means of adjusting screws, till it conceals the upper extremities of 

 the flame ; and thus the latter presents the appearance of a brilliant 

 zone of white light, which is from 3 inches to 6' inches high, according 

 to the pressure of the gas. An apparatus of this kind supersedes the 

 employment of many separate lamps ; and, being placed at a consider- 

 able height from the floor, it is possible to apply above the glass 

 chimney a pipe which, while it conveys the impure products of 

 combustion through the ceiling, may serve to ventilate the building or 

 apartment. This is found to be a cheap mode of producing a bright 

 light ; but as a similar effect may be produced by other means, the 

 distinctive name of Bude light is not now much employed. 



Oil Lamps. The general character of oil lamps is described under 

 AROAND LAMP. We shall advert here to a few special matters. 



One of the difficulties which have lessened the usefulness of common 

 oil-lamps is the tendency of the oil to thicken in cold weather ; while 

 another lies in the imperfection of the means for keeping the wick well 

 moistened with oil up to the verge of the flame. Both of these matters 

 have engaged attention within the, last few years. The mechanical 

 or Carcel lamp, so generally used by the opulent families in Paris, 

 has an apparatus by which the oil is raised through tubes by clock- 

 work, so as continually to overflow at the bottom of the burning wick ; 

 thus keeping it thoroughly soaked, while the excess of the oil drops 

 back into the cistern below. Less mechanical and more effective is the 

 Moderator lamp, a later invention than the Carcel. The Meteor lamp, 

 having some of the properties of the Carcel, is intended to burn rape- 

 oil. The internal arrangements of this lamp are curious and com- 

 plicated. The lower part of the pedestal consists of a reservoir for 

 containing the oil ; and in this reservoir is a kind of piston or plunger, 

 worked up and down by a nut and screw from the outside; the 

 rising of this piston occasions the pressure or tightening of a coiled 

 spring, and this pressure causes the oil to be forced up a central tube 

 towards the flame. 



One of the modes adopted for maintaining the oil in a liquid state, 

 is by the use of a lamp constructed by Mr. Parker, in which the oil is 

 used in a hot state. At a small distance around the tube which con- 

 tains the wick is another tube ; and the space between the two tubes, 

 of capacity sufficient to hold a pint, constitutes the reservoir for the 

 oil. The oil is thus so near the flame, that it speedily becomes warm, 

 by which its facility of burning is much increased. A slide valve is 

 opened to allow the oil to descend from the reservoir to the wick. 

 The intensity of the flame is modified by raising or lowering a bell- 

 mouthed glass chimney by means of rackwork mechanism. In a series 

 of experiments on the illuminating powers of different kinds of lamps 

 and candles, Dr. Ure found that the hot-oil lamp, with a given quantity 

 of oil, gave a brighter light than any other form of lamp ; or, the light 

 being equal in intensity, the hot-oil lamp was the most economical. 



