yune i6, 1881] 



NATURE 



155 



ness, serves the useful purpose of completing the combustion of 

 the gas, and thus diminishes the liability to blackening of the 

 ceiling. 



This arrangement for transferring the heat from the tip of the 

 flame to the air supporting its combustion is applicable also to 

 an open bat«\ving burner ; but I have not yet had time to ascer- 

 tain accurately the amount of increase of luminosity that may be 

 realised with tliis class of burner. 



I may here mention that another solution of the problem of 

 heating the incoming air by the waste heat of the products of 

 combustion has lately been brought under public notice by my 

 brother, Frederick Siemens, which differs essentially from the 

 plan I have suggested, inasmuch as he draws the flame down- 

 wards through heating apparatus, and thence into a chimney. 

 Experiments made officially and with great care have proved 

 that by these methods the luminous effect of gas can be practi- 

 cally doubled. In practice both these methods of intensifying 

 a gas-flame will probably find independent application accord- 

 ing to circumstances, the cause of increased luminous effect 

 being in both cases the same. 



From a purely theoretical point of view it can be shown that 

 of the caloric energy developed in the combustion of gas, a 

 proportion probably not exceeding i per cent, is really utilised 

 in the production of luminous rays, and that even in the electric 

 light nine tenths of the energy set up in the arc is dispersed in 

 the form of heat, and one-tenth only is utilised in the form of 

 luminous rays. It would lead us too far here to go into the 

 particulars of these calculations, but it is important to call atten- 

 tion to them, in order to show the large margin for practical 

 improvements still before us. 



By the combined employment of the process of separation of 

 the illuminating from the heating gas with the arrangement for 

 intensifying the luminosity of the gas-flame, the total luminous 

 effect produced by a given consumption of coal gas may be 

 nearly tripled, thus showing that the deleterious effects now 

 appertaining to gas illumination are not inseparably connected 

 with its use. 



My principal object in preparing this communication has been 

 to call your attentii^n generally to tlie important question of an 

 improved gas illuminatiin, and more particularly to the subject 

 of a separate supply for heatiag gas, which, if carried into effect, 

 would lead, I am convinced, to beneficial results, the importance 

 of which, both to gas companies and to the public, it would be 

 difiicult to over-estimate. 



Appendi.x 



Paris, June A,, 1S81 



Dear Sir, — I send you herewith the result of my experi- 

 ments, together with tables and curves ; the very ingenious pro- 

 posal that you have made would permit juch a division of the 

 total produclion of gas, that two-thirds could be employed for 

 lighting and one-tliird for heating purposes, resulting in splendid 

 illumination and much more rational heating. 



I am, dear sir, &c. , 



Dr. C. William Siemens A. Ellissen 



Experiments on the Variation of Production of Gas, and of its 



Illuminating Po-wer at different Periods of the Distillation 



Tables I. and II. contain the results of experiments made in a 

 bench of seven retorts of the type of the Compagnie Parisienne, 

 each retort being charged respectively with 100, no, and 120 

 kilogrammes (220, 242, 264 pounds). 



Table I. corres, ouds to a di-stillation of 4 hours. 



Table II. corresponds to a distillation of 4h. 48m. 



The period of distillation has been divided into intervals of 

 filteen minutes, and the results recorded on each horizontal line 

 refer to the gas produced during the quarter ending the time 

 mentioned on each liue. 



In each of the two tables the case of a charge of no kilos. 

 (242 lbs.) haibeen chosen as the standard, and the results have 

 been graphically represented by means of two curves, one in 

 red for the gas produced, and the other in blue for the illumin- 

 ating power. 



The line of abscissa: being divided into equal parts, each 

 representing fifteen minutes, each ordinate of the red cur\'e 

 gives the gas produced during the preceding quarter of an hour, 

 and the con-espondinj ordinate of the blue curve indicates the 

 illuminating power of this same gas. 



The production of the ga> been further divided into two por- 

 tions, the one destined for illumination, and the other for heating 

 and motive power. 



Per ton, 

 cubic feet. 

 6502-32 



The gas produced during the first quarter of an hour is gene- 

 rally of low illuminating power, and varies besides with the 

 hygrometric condition of the coal ; it has, in the following calcu- 

 lation, been accordingly classed with the heating gas, and the 

 gas produced during the interval from oh. 15m. to 2h. 15m. of 

 the v\ orking has alone been reserved for illuminating purposes. 

 Distillation in four hours. Charge of no kilos. (242 lbs.) 



I. Gas produced per 100 kilos, of coal distilled — 



Cubic 



1. From oh. 15m. to 2h. 15m. ... 18-062 



2. From oh. om. to oh. 15m., and 



from 2h. 15m. to 4h. om. ... 11-30S ... 407088 



Total 29-370 ... 10573-20 



II. Gas produced per too cubic metres obtained — 



Cubic 

 metres. 



1. From oh. 15m. to 2h. I Sm. ... 6r502 



2. From oh. om, to oh, 15m., and 



from 2h. 15m. to 4h. om. ... 38-498 



Total loo'ooo 



III. Mean illuminating power of the produced gas — 



Litres. 



In English 

 standard 

 candles. 

 16-16 



11-05 



1. From oh. 15m. to 2h. 15m. ... 87-7 



2. From oh. om. to oh. 15m., and 



from 2h. 15m. t0 4h. om. ... 128-2 

 Mean of the total mixed gas .as per 



calculation I03'3 



Illuminating power of mixed gas as 



per direct trial '05'7 



Distillation in 4 hours 48 minutes. Charge of no kilos. (242 Its.) 



I, Gas produced per 100 kilos, of co.al distilled — 



Cubic 

 metres. 



1. From oh. 15m. to 2h. 15m. ... 20-3S8 



2. From oh. om. to oh. 15m., and 



froai 2h. 15m. to 4h. 48m. ... 9-741 



Total 30-129 ... 10846-44 



II. Gas produced per 100 cubic metres obtained — 



Cubic 



1. From oh. 15m. to 2h. 15m. ... 67-673 



2. From oh. om. to oh. 15m., and 



from 2h. 15m. to 4h. 48m. ... 32-327 



«3'So 



Per ton, 

 cubic feet. 



7339'68 

 3506-76 



III. Mean illnmin.ating power of the produced gas — 



Litres. 



1. From oh. iSm. to 2h. 15m. ... ion 



2. From oh. om. to oh. 15m., and 



from 2h. 15m. to 4h. 48m. ... 132-4 

 Mean of the total mixed gas 11 1-2 



In English 



standard 

 candles. 

 14-02 



10-07 

 12-77 



It is not proposed to stop at the results obtained by distillation 

 in 4h. 4Sm., that is five charges per twenty-four hours ; expe- 

 rience has proved that the best conditions of working are found 

 in the use of active charges rapidly distilled by raising the 

 temperature of the furnaces. 



From these experiments it results that it would be poisible to 

 divide the products of distillation of coal into illuminating gas, 

 and gas for heating purposes and motive power. 



Thus in place of producing, as is generally done, by means of 

 a distillation of four hours and no kilos. (242 lbs.) per retort, 

 a mean result per :oo kilos of coal distilled, of 30 cubic metres 

 of normal gas, which corresponds to an expenditure of 105 litres, 

 to produce the light of a Carcel burner consuming 42 grammes 

 of oil per hour, there may be produced : — 



1. Ab^ut 1S-5 cubic metres of illuminating gas of an illnmi- 

 native power of 87 litres ; and 



2. AbDut 1 1 -5 cubic metres of heating and motive-power gas 

 of an illuminxtive pjwer of 128 litres ; or per 100 cubic metres 



