Uri 



ONDULATOUY FORCES. LIGHT. 



[OIL- LAMPS. 



a rectitlur of London, who used it in his manufactory a* 

 an illuminating agent. The oil U procured at the i-n-l of 

 the process for rectifying spirit In its raw and impure 

 condition it U usually called faints. It has the odour of 

 bad whisky, and contains alcohol, and various fatty 

 acids. By washing with water, then distilling with 

 carbonate of potash, and, finally, with chloride of cal- 

 cium, it is obtained in a tolerably pure condition. Five 

 hundred gallons of corn-spirit yield about one gallon of 

 oil. In it pure state, the oil has a peculiar ethereal 

 odour, which, when inhaled, is rather unpleasant and 

 irritating to the throat. Ite specific gravity varies from 

 823 to 840; it boils at 368, and emits a combustible 

 vapour. The oil is not soluble in water, but it mixes 

 with alcohol and wood-spirit in all proportion*. It burns 

 in an ordinary open lamp, with & clear and smokeless 

 name the light of which is tolerably intense. A lamp 

 that consumed the oil at the rate of 278 grains per hour, 

 gave a light that was about half as good again as that of 

 a standard sperm candle. At present the oil is in 

 demand for the manufacture of artificial essences, and 

 consequently it U too expensive for combustion in lamps. 



LAMPS. 



History and General Principles of the Subject. It has 

 been already stated that the employment of lamps can be 

 dated back to a very early period ; indeed, it is generally 

 thought that they were invented by the Egyptians, who 

 not only used them for common illuminating purposes, 

 but also placed them in the tombs of the dead as 

 emblems of mortality. The ancient Greeks were likewise 

 accustomed to the use of lamps, which we have every 

 reason to believe were fed with a vegetable oil. Hero- 

 dotus alludes to this fact ; and it is further evidenced in 

 many devices that we find sculptured in some of the 

 most ancient Greek vases; but it was centuries after 

 that before the Romans began to employ lamps, and then 

 they were only used iu the houses of the rich, or upon 

 occasions of special festivity. That most of the classical 

 nations have been accustomed to place lamps in the 

 sepulchres of the dead is an instructive fact ; for, 

 although various motives have been assigned for the 

 custom, there can be no doubt that it was intimately 

 connected with their belief in the existence of a soul, and 

 that it was meant to typify the departure of the spirit 

 or vital fire from its frail tenement of clay. This is 

 clearly set forth in many of the beautiful devices which 

 adorn the funereal lamps of the early Greeks, where the 

 immortality of the soul, and its departure fr6m the body, 

 is represented by the escape of a butterfly from an 

 apparently dead chrysalis. The testimony of Pliny, St. 

 Augustine, and others, has induced a belief, that in many 

 cases the sepulchral lamps were constructed so as to burn 

 for ever ; and some remarkable instances have been cited 

 in which the lamps were said to have been found burning 

 centuries after the tomb had been closed up ; bvit none 

 of these are sufficiently well authenticated, notwith- 

 standing that Liceto and other authors have taken great 

 pains to establish their truthfulness. 



It is very probable that the earliest lamps were not 

 made of any set form, but that the fat or oil was placed 

 in any convenient vessel, and burned by moans of a bundle 

 of rushes or dried moss. As civilisation advanced, and 

 the necessity for artificial light increased, attention would 

 naturally be directed to the form ben suited to the wants 

 if the people : and it is very likely that at first the lamp 

 was nothing more than a circular vessel or saucer con- 

 taining the combustible material. Lamps of this de- 

 scription are still employed on the continent for purposes 

 of general illumination. It is thougnt by some persons 

 that the lamps of the virgins alluded to in the Gospel of 

 St. Matthew (chap, xxv.) were merely rods of porcelain 

 or iron covered with cloth, and steeped in oil or fat, and 

 that the same kind of lamp or torch was usud by the 

 soldiers of Gideon ; but wo have no positive testimony in 

 support of such an opinion, although there is plenty of 

 evidence to show that lamps trimmed with oil were in use 

 long before that time. 



The next improvement in the form and construction of 

 the lamp is to be seen 

 in the ancient lamps of 

 Herculaneum and Pom- 

 peii. Examples of tncse 

 are to be found at the 

 Louvre, the British Mu- 

 seum, tin? Vatican, and, 

 indeed, in almost every 

 considerable museum in 

 Europe ; but the finest 

 specimens belonged to 

 the king of Naples, who 

 had a collection of such 

 things at Portici ; in 

 fact, in that museum there is a large collection of lamps 

 taken from the buried cities of Pompeii and Hcrcula- 

 iii-uiu. Besides which, Liceto, Bartoli, and Passcri 

 have published de- Fig. 17. 



scriptions and draw- 

 ings of many hun- 

 dreds of such lamps 

 that were in the 

 museums of Italy 

 during the 16th cen- 

 tury. The common 

 form of all of them 

 is that of an clou- 

 gated vessel, like a 

 boat, having the wick at one end (Figs. 86, 87, and 88) ; 

 at other times it was a simple disc, with a hole for the 

 wick on one or both sides, and an aperture in the 

 centre for supplying the oil i -. K s. 



(Fig. 89). Lamps of the former 

 description are still used by the 

 poor of the Orkney and Shut- 

 hind Isles. 



The material of which the 

 Greek and Roman lamps were 

 composed, was chiefly terra- 

 cotta, though some of the better sort wore made of 

 bronze, and even of silver and gold. A few ancient 

 lamps of iron have also been discovered, but they are 

 comparatively rare, perhaps Fig. 88. 



because of the perishable na- 

 ture of the metal. In the 

 museum at Portici there are 

 several iron lamps, together 

 with one of glass, all of which 

 were taken from the ruins of 

 Herculaneum. 



Much ingenuity was exhibit- 

 ed by the Greeks and Romans 

 in the construction and orna- 

 mentation of the supports (the 

 Xvcvovcoi, lampadaria or cande- 

 labra) which held the lamps. 

 At first these were composed 

 of cane ; and the Greeks, in nil 

 their designs, never lost sight 

 of this fact; consequently we 

 find a variety of vegetable forms blended with the stiff 

 reed, giving it lightness and elegance ; the twining ivy 

 and the graceful acanthus were frequently associated in 

 this manner. With the Romans, however, the usual 

 support was a tripod resting on lions' feet. 



At a very early period it must have been observed, 

 that when an attempt was made to enlarge the wick 

 beyond a certain point, the flame became dull and smoky. 

 To remedy this, it was customary to split the wick up 

 into a number of small flames, each of which would 

 allow the atmosphere to play freely around it, and thus 

 to keep up a tolerably good combustion. There i 

 loulit that this device was well known to the ancients 

 88), though it is generally considered, that Dr. 

 Franklin was the first to snow, that the same quantity of 

 cotton divided into two wicks, gives a bettor light than 

 when it is used as one ; but the dillirult y which presents 

 itself in the employment of such a contrivance, is that 



