ON THE DEVELOPMENT OF LIGHT FROM COAL-GAS. 241 



The green gland in Palinmnis is very large, and I have been subjectino- 

 it to examination as to its form and structure, as well as placed the 

 seci'etion contained in the sac connected with it in the hands of an 

 expert chemist, but the results have not sufficiently progressed to enable 

 me to embody them in this report. 



Report on the best means for the Development of Light from Coal- 

 Gas of different qualities, by a Committee consisting of Dr. 

 William Wallace (Secretary), Professor Dittmar, and Mr. John 

 Pattinsox, F.G.S., F.I.G. Drawn up by Mr. Pattinson. 



Part II. 



The first part of this Report, which was presented at the meeting of the 

 Bi'itish Association in 1878, had reference chiefly to the use of cannel gas 

 such as supplied in most of the towns of Scotland, and which has an 

 illuminating power equal to 26 candles when burned in a union-jet 

 burner at the rate of 5 cubic feet per hour and under a pressure of 0'5 

 inch. It also pointed out the best means known of burning this quality 

 of gas, and gave the results of photometric testing of several kinds of 

 burners under varying conditions of pressure. 



It is the object of this second part of the Report to give similar infor- 

 mation regarding the burning of what is known as common gas, or gas 

 made from the common bituminous coal of the Newcastle and other coal- 

 fields, or from this class of coal mixed with a small quantity of cannel 

 coal, and having an illuminating power equal to 16 standard sperm 

 candles when consumed at the rate of 5 cubic feet per hour in Sugg's 

 No. 1 London Argand Burner — the standard burner adopted in London by 

 the London Gas Referees, and prescribed in nearly all I'ecent Acts of Par- 

 liament of gas companies. This quality of gas, or gas varying from 14 

 to 16 candles illuminating power, is chiefly used in London and in most 

 towns in England and Ireland. 



The principal condition to be observed, in order to develop the maxi- 

 mum amount of light from coal gas, is to supply the flame in a suitable 

 manner with just a sufficient amount of air to effect the complete combus- 

 tion of the gas. If coal gas is lighted as it issues under a low jjressure 

 from the end of a gas pipe from which the burner has been removed, it 

 burns with a long, irregulai'-shaped flame, giving off much smoke, and 

 yielding a dull yellowish light of very little intensity. The gas has to 

 ascend to a considerable height before it meets with sufficient air to con- 

 sume it comjjletely, and the upward currents created by the heat waft the 

 languid flame about in all directions and cause it to give off smoky par- 

 ticles. On the other hand, if the gas is forced under considerable pressure 

 through a very small orifice or very narrow slit, it burns with a thin bluish 

 flame, without visible smoke, and yielding very little light. The small, 

 rapid stream of gas, by virtue of the force with which it issues, becomes 

 mixed at once with such an excessive amount of air that the carbonaceous 

 constituents of the gas, instead of being partially separated and made in- 

 candescent, are converted at once into carbonic acid in a flame havino- 

 little or no luminosity, just as when gas is burned in a Bunsen burner. 

 These illustrate two cases in which air is supplied to the flame in an un- 

 1880. K 



