230 Comparative Value of different kinds of Parrot Coal, ^c. 



SIX miles. By the chlorine the indication was 13.25. The 

 specific gravity was 6.53, and the flame by the Aldcock burner, 

 at one inch pressure, was four inches. In this trial the differ- 

 ence is very trifling ; and as the gas on which I operated at the 

 works was that made from Saturday evening to Monday 

 morning, on which day the experiments were conducted, there 

 is every reason for believing, that that tried at the works and 

 at the distant point was the same. 



Trials on the Edinburgh Gas. — 15th Nov. 1842. This gas, 

 tried at my laboratory in Surgeon Square, a distance of nearly 

 a mile from the manufactory, indicated, by the chlorine test, 

 13.7. On the 9th Dec, it was 13 ; on the 19th, it was 13.66, 

 giving an average of 13.45 ; on the 20th Dec, the gas was 

 tried at the works, and on an average was found to be 13.16 ; 

 on the evening of the same day, the gas at George Square, a 

 distance of upwards of a mile, was 14 ; on Friday, the 23d 

 Dec, at the works, it was 14; at George Square, on the 

 evening, it was 14. The average of all the trials at the 

 works was 13.5 ; at a distance, it was 14. I have again, 

 more lately, tried this gas at a greater distance. On the 

 20th Dec. 1843, the gas at the works indicated 13 ; at the 

 distance of upwards of three miles on the Glasgow road, the 

 indication was 12.5. 



In the above experiments, the illuminating power of the gas 

 is, in some cases, the same at the works and at a distance ; in 

 three, it is rather lower, and in one it is rather higher, at the 

 distant point. Taking the average of all the trials, the re- 

 sults are — 



Average, 13.59 13.35 



The difference, as shewn by the above table, is so very 

 trifling, as to be altogether unworthy of notice ; consequently 

 proving that the distance to which the gas is conveyed, after 



