CANDLES.] 



UNDULATORY FORCES. LIGHT. 



93 



are placed one on each side of the paper, the disc will 

 disappear entirely ; for then the light of one side neu- 

 tralises that of the other, and there is no disposition to 

 produce either effect. Upon this is founded the principle 

 of Bimseu's photometer. The instrument consists of a 

 graduated rod about five feet in length, having a support 

 at each end. The prepared paper is held by a frame 

 which slides upon the rod between the lights. This 

 frame is usually enclosed in a darkened chamber, so as 

 to exclude all li^ht but that emanating from the object 

 to be tested. The frame containing the paper is slid to 

 one side or the other until the disc entirely disappears, 

 and thus we read off the relative values of two tights. 

 In making experiments on coal gas, it is usual to burn it 

 at the rate of five cubic feet an hour, from an Argand 

 humor having fifteen holes and a seven-inch chimney. 

 The candle, which is used as a standard for comparison, 

 is generally of sperm, and the rate of consumption i.-. 

 fixed at 120 grains per hour. When it happens that the 

 consumption is greater than this, it may be reduced to 

 the normal standard by a very simple calculation : thus 

 suppose that, on experiment, it was found that the light 

 of the gas was equal to 11 candles of 140 grains' con- 

 gumption ; then, as 120 grains is to 140, so are 11 candles 

 to the standard value namely, 12 '8 cam!! 



In tliis way the following results have been obtained ; 

 and, in order that an estimate might be made of the 

 relative values of different illuminating agents in respect 

 of tlioir consumption and heating power, other results 

 have been appended : 



The amount of heat, in these cases, has been deter- 

 mined by burning the lamp, or candle, under a vessel 

 containing a given quantity of water, or in a space 

 surrounded by a certain amount of that liquid, at a 

 known temperature : from which it will be evident that, 

 for the same amount of light, cannel gas produces the 

 least heat ; then follows sperm oil in an Argand or 

 carcel-lamp ; then common coal gas ; then wax, sperm, 

 and other candles ; and, finally, oil in a common lamp, 

 and tallow candles both of which produce an enormous 

 amount of heat in proportion to the light evolved. 



CANDLES. 



Af afrnal.i employed in Candle^making. It has been 

 already remarked that candles are among the most an- 

 cient of illuminating agents, and it cannot be doubted 

 that originally they were manufactured in a very rude 

 war, by simply smearing a porous combustible solid 

 with animal fat ; but, at the present time, a number of 

 fatti H are employed in their manufacture, ami 



pains taken to have them as pure as pos 

 ^ "' ' le, tallow and its derivatives stearine 



"d K; and margaric acid: palm nil 



and its c.- . palmitin and palmitic acid ; . 



nut oil, eoeinin and cocinic acid; spermaceti, wax, 



'I'm, A-c. All these require to be purified b. 

 tln-y ran IK; converted into candles ; and hence the 

 necessity for describing them in detail. 



The i' <ittt> are of three kinds; namely, the 



"farushf.' 1 ""'), which grows abundantly 



in n. ; and of cotton, which is either rolled 



I into ^trands. Tlio first is used for 

 the common rushlight, t!m seroml for ordinary dip' 

 for wax-ligliti, and the tliird for spermaceti, stearic 



stearine, and other candles which do not require snuff- 

 ing. In many cases it is necessary to prepare the wicks 

 with a salt of ammonia, as the phosphate, borate, or 

 sulphate, in order to keep them from clogging, and to 

 give them a sufficient degree of rigidity to enable them 

 to stand firmly up when they are burning. This was an 

 improvement introduced in 183C, by M. De Milly, of 

 Paris. Dr. Ure says that the best wicks are still im- 

 ported from Turkey, and they are composed of skeins of 

 unbleached cotton. The wick of wax mortars and night- 

 lights are made of flax, as cotton is not able to resist the 

 long-continued action of the high temperature of the 

 flame. 



Varieties of Candlfs, and thdr Manufacture. Two 

 sorts of candles are commonly met with in commerce 

 namely, dip* and moulds. The former are made by re- 

 peatedly dipping the wicks into melted fat, allowing a 

 sufficient time between each of the dippings for the tallow 

 or fat to cool. Usually the wicks are cut into proper 

 lengths by a machine, according to the sort of candle to 

 be made, and then suspended from a rod or frame, called 

 a port ; by this means the workman is enabled to dip a 

 number of candles at the same time. In large establish- 

 ments the ports or frames are attached to a revolving 

 beam, so that, without much exertion, the workman can 

 successively dip one port after another, and thus make 

 from seven to eight thousand candles in a day. The 

 tallow is kept in the dipping-vessel, at a temperature just 

 over the point of solidification. 



Mould candles are made in a tubular mould, which is 

 either of pewter or glass. The mould consists of t\v> 

 namely, the cylinder and the cap. The former is 

 of the full length of the candle, and is highly polished in 

 the interior, so as to allow the candle to slip easily out 

 of it. The latter is a small cup, having a hole in tl.o 

 centre for the passage of the wick ; it is fixed on to the 

 bottom of the cylinder, and serves to give the taper-form 

 to the top of the candle. Sometimes there is a third 

 piece, called the foot, which is a sort of funnel, that is 

 screwed on to the opposite end of the cylinder, and .v 

 for the guidance of the melted fat into the mould. Eight 

 or ten of these cylinders are usually fitted into one frame, 

 which has the upper part formed into a trough for the 

 reception of the melted tallow. The wicks are drawn 

 into the cylinders by a hooked wire, and kept in their 

 places by a wedge, which fixes them in the cap of the 

 mould ; the other end being held by a rod which passes 

 across the frame. When all is ready, the liquid fat is 

 run into the trough, and thence into the moulds, until 

 each cylinder is full. After it has thoroughly cooled 

 surplus fat is scraped out of the trough, and, the wedges 

 being removed from the hole in the cap, each caudle is 

 drawn out of its mould by means of a hooked \viro, which 

 catches hold of the loose end of the wick. The candles 

 are then cut of one uniform length, and trimmed up f. .r 

 the market. 



The cheaper sort of mould candles are those manufac- 

 tured by Price and Company, ami are made by machinery , 

 eighteen candles being moulded at one time. The wicks 

 are made in lengths of sixty yards ; eighteen of these 

 wicks are wound off upon eighteen separate rollers, and 

 a roller is placed over each mould. The wicks having 

 been passed through the cylinder, are seized at the lower 

 end by a set of eighteen forceps, which draws them tight, 

 and fixes them in their places. The moulds, which dur- 

 ing the operation have remained in a horizontal position, 

 are now turned in a vertical direction, the small eml 

 downwards, and are passed upon a railway to the person 

 "ho fills them. In their course they have traversed a 

 hot closet, and have thus acquired a proper temperature 

 for receiving the tallow. When full, they are pushed on 

 to other railways, and allowed to cool. This being ac- 

 complished, they are brought back in succession, by 

 means of turn-tables, to their former places. The frame 

 is then placed in a horizontal position ; and eighteen 

 ITS or pistons press forward the loose caps of the 

 moulds, and thus push out the caudles, and deliver the 

 wicks for another operation. 



lf'.e and Paraffint candles are usually moulded by 



