330 



THE ( n IL ENGINEER AND ARCHITECTS JOURNAL. 



[.Skptkmbkr, 



siiniod 810 sjiMins, or 0.12 of a pound per lionr — which mimber multi- 

 plied by the price per pound, gives the product O.Orf. us the relative 

 cost of'lOO of this light. 



5. A liot-uil hi nip charged with Price and Co.'s cocoa-nut oil (oleine), 

 of specific gravity 0.92.5, at 4s. Gd. per gallon, or 5|rf. per lib., had to 

 be placed 9 feet from the screen, and consumed 103 grains per hour. 

 Had its light been 100 instead of 81 (9'), the consunijjtion would have 

 been 1277 grains, or 0.182 of a pound per liour ; whicli number multi- 

 plied by its price per povmd, the product 1.031rf. will represent the 

 cost of 100 of this illumination. 



0. In comparing the common French annular lamp in general use, 

 witli the mechanical lamp, it was found to give about one-half the 

 light, and to consume two-thirds of the oil of the mechanical lamp. 



7. Wax candles from some of the most eminent wax-chandlers of 

 of the metropolis were next subjected to experiment; and it is very 

 remarkable that, whether they were threes, fours, or sixes in the 

 pound, each allbrded very nearly the same quantity of light, for each 

 required to be placetl at a distance of 3 feet from the screen to afford 

 a shadow of the same tint as that dro|)|ied from the mechanical lamp, 

 estimated at 100. The consumption of a genuine wax candle, in still 

 air, is, \ipnn an average of many experiments, 12.5 grains per hour, but 

 •as it affords only 1-1 1th of the light of the mechanical lamp, 11 times 

 ]2r):=1375 grains, or 0.10ri4 of a pound is the quantity that would 

 need to be consumed to produce a light equal to that of the said lamp. 

 If we multiply that number by the price of the candles per lib.=30f/. 

 the product^5.S92f/. is the cost of 100 of illumination by wax. A 

 wax candle, three in the pound (short), is 1 inch in diameter, 12 inches 

 in length, and contains 27 or 28 threads, each about l-90th of an inch 

 in diameter. But the quality of the wick depends upon the capillarity 

 of the cotton fibrils, which is said to be greatest in the Turkey cotton, 

 and hence the wicks for the best wax candles are always made witli 

 cotton yarn imported from the Levant. A wax candle, three in the 

 pound (long), is g of an inch in diameter, 15 inches long, and has 2G 

 threads in its wick. A wax candle, six to the pound, is 9 inches long, 

 4-5ths of an inch in diameter, and has 22 threads in its wick. The 

 light of this caudle may be reckoned to be at most, about 1-llth less 

 than that of the threes in the ]K)und. A well-made short three burns 

 with surprising regularity in si ill air, being at the rate of an inch in an 

 liour an<l a liaff, so that the whole candle will last IS hours. A long 

 three will last as long, and a six about 9^ hours. Specific gravity of 

 wax=0.960. 



8. .Spermaceti candle, three in the poiuid, is 9-lOths of an inch in 

 diameter, 15 inches long, and hasaplaiteil wick, instead of the parallel 

 threads of a wax candle. The same candles, four in the pound, are 

 8- 10th of an inch in diameter, and 13i inches long. Each gives very 

 nearly the same quantity of light as the corresponding wax candles : 

 viz., 1-llth of the light of the above-mentioned mechanical lamp, 

 and consumes 142 grains per hour. Multiplying this number by 

 1 1, the product, 1562 grains ;= 0.223 of a pound, would be the con- 

 s\nnption of spermaceti requisite to give 100 of illumination. Multi- 

 ])lying the last nimiber by 24(/., the price of the candles per pound, the 

 product 5.352rf. is the relative cost of 100 of this illumination. 



9. S/iciric Acid candles, commonly called German wax, consume 

 1G8.5 grains, or 0.024 of a pound, per hour, when emitting the same 

 light as the standard wax candle. Multiplying the latter number bv 

 11, and by Itirf. (the price of the caudles per lib.), the product 4.224rf. 

 will represent the relative cost of 100 of this illumination. 



10. Tallow candles; moulds, short threes, 1 inch in diameter, and 

 12A in length; ditto, long threes, 9-lOths of an inch in diameter, and 

 15 in length ; ditto, long fours, 8-lOths of an inch in diameter, and 135 

 in length. Each of these candles bums with a most uncertain light, 

 which varies from l-12th to l-llith of the light of the mechanical 

 lamp — the average may be taken at l-14th. The threes consume 

 each 144 grains, or 0.2 of a pound, per hour; whicli number, multi- 

 plied by 14, and by 9rf. (the price per pound,) gives the product 2.52rf. 

 for the relative cost of 100 of this illumination. 



11. i-'a/wiu's spreading wick candles. Distance from the screen 3 

 feet 4 inches, with a shadow eipial to the standard. Consumption of 

 tallow per ho\u- 232.5 grains, or 0.U332 (jf a pound. The square of 3 

 feet 4 inches = 11.9 is the relative illumination of this candle — 

 11.9 : 0.3332 : : 100 : 0.28; and U.28 X lOrf. = 2.8 the relative cost 

 of this ilhmiination. 



12. Cocoa-nut stearine candles consumed each IGS grains per hour, 

 and emitted a light equal to l-16th of the standard flame. Multiply- 

 ing IGs by Hi, the product 3088 grains, or 0.44 1 of a lib., is the quan- 

 tity which would be consumed per hour to afford a light equal to 100. 

 And 0.441 multi])lied by lOrf., the price per lib., gives the ])roduct 

 4.4 Irf. as the cost of 100 of this ilhuuiuation per hour. 



13. A Gas Argand London Lamp, of 12 holes in a circle of 'i of an 

 inch in diameter, with a Hame 3 inches long, aHbrded a light = 7Si 



compared to the mechanical lamp; and estimating the liglit of the 

 said mechanical lamp as before, at 100, that of the hot-oil lamp is 120, 

 and that of the aliove gas flame 78.57, or in round numbers 80, and the 

 cominun Fniicli lump m gtiiiral use 50. 



Collecting the preceding results, we shall have the following tabular 

 view of the cost per hour of an illumination equal to that of the me- 

 chanical lamp, reckoned 100, or that of 1 1 wax candles, three to the 

 j)Ound. 



TABLE OF COST PER HOUR OF OXE HUNDRED OF ILLU.MINATION. 



Pence. 



1. Parker's Hot-Oil Lamp, with southern whale oil .... 0.4875 



2. Mechanical or Cared Lamji, with sperm oil 1.2804 



3. Parker's Hot-Oil Lairip, with siierm oil 0.!I02 



4. Ditto ditto common olive oil O.ilOO 



5. Ditjo ditto cocoa-nut oleine or oil .. 1.031 



6. French Lamp iu general use, with sperm oil 1.7072 



7. Wax Candles 5.892 



8. Spermaceti Cindles 5.352 



9. German Wax (Stearic Acid) ditto 4.224 



10. Palmer's Spreading Wick Candles 2.800 



11. Tallow (Mould) Candles 2.520 



12. Cocoa-nut Stcariiie, of Price & Co 4.41 



Since the hot-oil lamp cijfurch siij^cient liglit for reading, writing, 



sewing, Sfc, irilh one-Jiflh vj its maxtmnm fame, it mill burn at that rate 

 for 10 hours at the cost nf about One Penni/, and is, hence, well entitled to 

 its inventor's designation, " The Economic." 



Sir D. BreW'Ster, in his examination lately before the Committee of 

 the House of Commons on lighting the House, stated, that the French 

 light-house lamp of Fresnel emitted a light equal to that of 40 Argand 

 flames : whereas, according to other accounts, it gave much less light. 

 With the view of settling this point, before being examined by the 

 said Committee, I repaired to the Trinity-house, and tried one of the 

 two original Fresnel lamps, wdiich had been deposited there by that 

 eminent French engineer himself. This lamp consists of four con- 

 centric circular wicks, placed in one horizontal plane ; the innermost 

 wick being I of an inch in diameter, and the outermost 3i inches. 

 Being carefully trimmed, supplied w ith the best sperm oil, surmounted 

 with its great glass chimney, burning with its maximum flame, and 

 placed at a distance of 13 feet 3 inches from the screen, it let fall a 

 shadow of the same tint as that let fall by the flame of my mechanical 

 lamp, placed at a distance of 4 feet inches from the screen. The 

 scpiares of these two numbers are very nearly as 8J to 1 (175.5625 to 

 20.25); showing that the Fresnel lamp gives less than 9 times the 

 light of my mechanical lamp, and about 9.6 times the light of one of 

 the Trinity-house Argand lamps. The Fresnel lam]) is exceedingly 

 troublesome to manage, from the great intensity of its heat, and the 

 frequent fractures of its chimneys — two liaiing been broken in the 

 course of my experiments ;\t the Trinity-house. 



Mr. Goldsworthy Gurncy, the ingenious inventor of the new light- 

 house lanq), in which a stream ot oxygen gtis is sent up through a 

 small tube within the burning circular wick of a small Argand lamp, 

 having politely sent two of his lamps to my house, along with a bag of 

 oxvgen gas, I made the following experiments, to ascertain their 

 illuminating powers, compared to those of tire mechanical lamp and 

 wax candles. 



His larger lamp has a wick J of an inch in diameter, but emits an 

 oxygen flame of only i of an inch. The flame is so much whiter than 

 that of the best lamp or candle, that it becomes difiicult to determine, 

 with ultimate precision, the comparative depths of the shadows let 

 fall by them. The mean of several trials showed that the above Bude- 

 light (as Mr. Gurney calls it, from thi> name of his residence in Corn- 

 wall,) lias an illuminating power of from 28 to 30 wax candles. His 

 smaller lamp has a flame i of an inch in diameter, and a wick 4 of an 

 inch. Its light is equal to that of from 18 to 20 wax candles. He 

 propose to mount GO such lights, distributed into 8 compartments, in 

 the ceiling, for lighting the House of Commons, the light being re- 

 flected downwards by concave mirrors. 



The Committee of the House of Commons, on lighting it, having 

 asked me what was tlie relative vitiation of air by the breathing of 

 men, and the burning of CLUidles, I gave the following answer : — 



Wax contains 81.75 paits of carbon in 100, which generate by com- 

 bustion 300 parts of carbonic acid gas. Now, since 125 grains of wax 

 constitute the average consumption of a candle per hour, these will 

 generate 375 grains of carbonic acid; equivalent in volume to 800 

 cubic inches of gas. According to the most exact experiments on 

 respiration, a man of ordinary size discharges from his lungs 1G32 

 cubic inches of carbonic acid gas per hour, which is very nearly the 

 double of the quantity jjroduced from the wax camlle. Hence tiie 

 combustion of two such candles vitiates the air much the same as the 

 breathing of one man. A tallow candle, 3 or 4 in the pound, generates 



