206 Drs. Christison atid Turner on Oil and Coal Gas. 



the contrary the temperature is too high, the combustion is 

 indeed complete and without smoke, but there is a partial de- 

 struction of light. (This last point is the most delicate in the art 

 of lighting, since the phaenomenon is not directly perceptible 

 by our senses.) In each case, a variable proportion of oil is ex- 

 pended in pure loss. Accordingly, I believe I do not exaggerate 

 in stating, that Argand lamps which give the maximum of light 

 due to the weight of oil they consume, are not less rare than 

 capital prizes in the lottery. 



Lighting with gas, on the contrary, is a process compara- 

 tively very simple, which dispenses with all cai'e and attention; 

 for the gas which freely escapes under a regular pressure 

 through the orifices of a burner well executed and judiciously 

 proportioned in its dimensions, cannot fail to give an invariable 

 maximum of light. 



It is by these considerations only that I have been able to 

 account to myself for a fact which appears very extraordinary 

 at first sight; namely, that 100 pounds of raw oil converted 

 into gas in a large apparatus, such as are constructed by 

 Messrs. Taylor and Martineau of London for the lighting 

 of towns, produce a quantity of light which cannot be pro- 

 duced by Argand lamps without burning at least 1 30 pounds, 

 sometimes 150 pounds of purified oil ; and it happened to my 

 friend the learned Professor M. Clement Desormes and myseltj 

 to make experiments in London on a quite new Paris Argand 

 lamp, which consumed in the proportion of 318 pounds of oil 

 for 100 pounds which its light only represented, in compa- 

 rison with oil gas. 

 September, 1825. 



XXIX. On the Compai-ative Advantages of Oil and Coal Gas. 

 By Robert Christison, M.D. F.R.S.E., Professor of 

 MedicalJurisprudencc ; and Edw. Turner, M.D. F.R.S.E. 

 Lecturer on Chemistry, Edinburgh.* 

 '"I ""HE paper (read before the Royal Society of Edinburgh, 

 ^ April 18, and May 2, 1825) from which the following 

 extract is given, contains full details of a series of experiments 

 undertaken at Edinburgh, as subordinate, in the first instance, 

 to an inquiry regarding the illuminating power of oil and coal 

 gases, at a time when, from the projected establishment of an 

 oil gas company, the question of the illuminating power of the 

 gases excited an extraordinary interest in that city ; and the 

 subject being taken up under the powerful influence of private 

 interest, a variety of statements were published by several sci- 

 entific gentlemen as the result of their experiments, which, in- 



* From the Edinburgh Philosophical Journal, vol. xiii. p. 34. 



stead 



