GAS-LIGHTING 



103 



and so forth; but the recent remarkable pi 



in gas-lighting has been duo to the study of the 



mi.t ual act ion> of Ma >, and to the use of hot air 



ami sometimes hot gas. For example, we have 

 concentric Ai^'i'l flames (Sugg) ; porcelain cylin- 

 der! in i IK- axis of an Argaml flame to keep the 

 flame from flickering, to keep up the heat of the 

 M a me, and also themselves to radiate light when in- 

 candescent ; burners in which gas from a circular 

 slit plays on the under surface of a porcelain globe; 

 and especially regenerative burners of various 

 models, generally with inverted flames, in which 

 the heated products <>f combustion are made to heat 

 the incoming air. (ilolnjs and shades cut off a good 

 deal of light ; a clear glass globe cuts off from 9 to 

 1-J per cent. ; ground ^lass about 40; opal globes 

 about oO. (! lobes should never have a lower 

 a pert nre narrower than 4 or 5 inches ; the ordinary 

 narrow aperture makes a strong draught of air, 

 which materially weakens the brightness of the 

 (lame, and unsteadies it. For use with incandescent 

 mantles globes are now made with surfaces mathe- 

 matically facetted ( ' holophanes') or channelled 

 ('ditfusers') which distribute the incident light 

 and spread out the light so as to make it appar- 

 ently fill the globe. 



Sometimes gas is burned with air in a small 

 Bunsen burner, and over the flame is fitted a basket 

 of platinum wire (Lewis), or a small mantle con- 

 sisting of thoria along with a little ceria( Auer von 

 Welsbach), which emits a brilliant white light on 

 incandescence ; or the ordinary flame of gas may be 

 rendered more luminous by passing the gas over 

 melted naphthaline, which it takesup ( Albo-carbon ). 

 In Denayrouze's modification of the Bunsen burner, 

 the gas and air are effectively mixed by means of a 

 little fan-wheel driven by a minute electromotor; 

 the flame is altered in character and becomes in- 

 tensely hot; if a Welsbach mantle be used with 

 such a burner, the lighting effect goes up as high as 

 270 candles with a consumpt of 9 cubic feet of 

 London gas per hour. In Bandsept's Bunsen burner, 

 the gas and air are similarly mixed by means of a 

 baffler immediately under the flame ; the result is 



about f the light given by a Denayrouze. 

 For neating purposes, coal-gas mixed with air 

 produces a smokeless flame and a higher tempera- 

 t lire than it does when burned in luminous flames ; 

 and so for direct heating the Bunsen Burner (q.v.) 

 principle is suitable. In one modification of the 

 Bandsept Bunsen burner the air is driven through 

 an inverted injector under high pressure, dragging 



Sas with it, and being mixed therewith ; and the 

 ame is produced under the surface of any liquid 

 which it may be desired to heat up. Thus about 

 90 per cent, of the heat evolved is utilised directly. 

 Gas produces the same quantity of heat, provided 

 that it is completely burned, in whatever way it 

 is burned. Convenience, cleanliness, may often 

 determine the use of Bunsen flames ; but where 

 radiation is expected to come into play the lumin- 

 ous flame is more effective as for cooking (see 

 W AKMING). Coal-gas for cooking is economical, as 

 it can be turned off when not wanted, and turned 

 on at once ; and it is smokeless if properly burned. 

 Of course it ought not to be left unprovided with a 

 chimney. For ventilation, a well-arranged system 

 of lamps, especially of the regenerative type, will 

 provide motive power for carrying away their own 

 products of combustion and for renewing the air of 

 the room. Gas is largely used for gas-engines 

 {q.v. ), which in 1896 were being made up to 1000 

 horse-power. 



The price of light obtained from coal-gas may be 

 Ascertained by finding the cost of a candle-hour 

 the light of one standard sperm candle for one hour 

 in each case. The table combines the data of 

 Stevenson Macadam, Letheby, Thompson, Poris, 



and others, and given the price per candle-hour, 



in thousandths of a penny : 

 K'lltilmrxh K". - candle-power, In 5-fe*t burner 

 . ) ; linhtiiiK effect -24 candle* ; pric of ga 



88. jMir thniiiiuiiil <:ublc feet 7'6 



Do. in a 4-feet burner (No. 4); lighting effect 



17-8 candle* 8D 



Do. 8-feet burner 

 Do. 2 

 Do. 1 

 Do. 



11-8 candles 9*0 



10-4 



3U .. 14-0 



0-86 .. .... 21-0 



N-.. :t) 

 No. 2) 

 (No. 1 

 (No. I) 



Do. with a Welsbach incandescent mantle, in a 

 Si-feet burner ( 1-inch premium ) ; average effect, 



4$ candles; mantle 15d., lasting 1000 hourn 8-126 



Gas at say 2u. 9d. for Id-candle gas; burned In 



Argands 7*7 



Do. in Siemens' precision Argand burner 6*8. 



Do. ii Inverted Hiemenn, Buschke and Wenhain... 2 < 6-6*8 



Do. burned in Welabach mantle an above 2-99 



Do. M ii with Bandsept burner 2-04 



Do. ii H with Denayrouze burner, 



9 cubic feet, 270 candle-power 1'52 



Spertn oil, at 2s. per gallon, in Argands 8-7-27'S 



ii ii in common lamps 50 O 



Paraffin, at 8d. per gallon, in modern lamps 5-3-8-9 



Tallow candles, at 6d. per Ib 110 



Composite candles, at 8d. n 160 



Paraffin caudles, at 5d n 02-5 



Wax candles, at 2. 404 



Electricity in arc lamps, 875 candle-power, consuming 



600 watts per hour, at 5d. per 1000 watts 2-06 



Electricity in glow lamps, 16 candle-power each, 

 consuming 56 watts per hour, at 5d. per 1000 watts ; 



lamp Is., lasting 1000 hours 17-85 



The price of gas, like the quality, will vary from 

 place to place, owing to differences in the price of 

 coal, the cost of the works, and so forth. In 

 the London Gas-light and Coke Company's accounts 

 we find the gross cost of manufacture of each 1000 

 cubic feet of gas sold is23'418 pence ; the residuals 

 coke, breeze, tar, and ammoniacal liquor return 

 9'036d. : so the net current cost at the works is 

 14'382d. for each 1000 cubic feet sold; the cost of 

 distribution is 3'571d. ; public lighting involves an 

 outlay of 0'437d. ; rates and taxes come to 2'696d. ; 

 management to 0'894d. ; various charges (bad 

 debts, annuities, legal expenses, &c. ) come to 

 0'546d. altogether 22 '526d. : which meter and stove 

 rents, &c., bring down to 22*144d. The average 

 price of the gas sold is 33 -703d. ; the difference, 

 ll-f>61d. per thousand on a sale of 9,453,889,000 

 cubic feet in six months, corresponds to a gro^s 

 profit of just over 8J per cent, per annum on the 

 paid-up capital of 11,198,000. The capital value 

 of the worts of this company in January 1896 was 

 11,792,851, 9s. lid.; that of the South Metro- 

 politan Company was 3,405,715, 4s. ; and that of 

 the Commercial Company, 877,951, 10s. 9d. 



The risks of gas-lighting are twofold explosion 

 and poisoning. Explosion cannot occur until there 

 is about 6'6 per cent, of gas in the air, but it is 

 dangerous to ' look for a leak with a light.' As to 

 poisoning, the gas must escape into a room without 

 being noticed until there is alwut one-half per 

 cent, of carbonic oxide i.e. from 4 to 12 per 

 cent, of coal-gas in the air of the room, before 

 danger to life becomes imminent ; and this per- 

 centage is rarely attained by ordinary escapes into 

 rooms of fair size. Fatal accidents have generally 

 happened from escapes into small rooms, and also 

 from the travelling of gas from broken mains 

 through earth into an earth-floored house, which 

 may draw the earth-gases through it in a deo- 

 dorised condition. A gas-escape is most likely to 

 be serious in its consequences when it takes 

 place into the upper part of a room ; the per- 

 centage near the ceiling may then come to be 

 much greater than it is at first lower down (see 

 POISONS ). 



From 1639 on wards the attention of scientific men 

 had repeatedly been turned to 'burning springs' or 

 streams of ' inflammable air ' issuing from wells and 

 mines in the coal districts of England, and com- 

 munications on the subject were addressed to the 

 Royal Society of London. Some time before 1691 



