228 Dr Fyfe on the Comparative Value of different kinds of 



tity of gas given off by the coals, then the comparative value 

 of these coals for the manufacture of gas will be as follows : — 



Knightswood, . . . 1.00 



Skaterigg, . . . 1.12 



Marquis of Lothian, B, . 1.81 



Marquis of Lothian, A, . 2.15 



Lesmahago, F., . . 2.20 



Torryburn, . . . 2.22 



Monkland, , . . 2.85 



Wemyss, . . . 3.41 



Arniston, . . . 3.43 



Lesmahago, D., . . 3.58 



In the above calculations, the value of the coke, and of the 

 ammoniacal liquor and tar, is not taken into consideration. 



II. On the Effect of the Transit of Gas in the Pipes, from the Manu- 

 factory to the place where it is to he consumed. 



It is well known, that, with the view of purifying coal-gas, 

 it is made to travel through the condenser, where it deposits 

 its tar, volatile oil, and ammonia. In most cases, the condenser 

 is merely a system of tubes or boxes, the length and cubic 

 area of which vary according to the extent of the manufactory. 

 It may naturally be supposed that after leaving the gasometer, 

 the gas, during its passage in the street pipes, will be still 

 further affected ; and hence has arisen the idea, that the gas 

 at a distance from the manufactory, is of inferior illuminating 

 power to that consumed near it. A different opinion has, 

 however, been maintained by others ; indeed, many suppose, 

 that the lighter particles are conveyed to the greater distance, 

 and as these are conceived to be the purest and most highly 

 illuminating, hence, it is imagined, that the gas delivered at 

 a distance from the works, is of superior illuminating power to 

 that consumed in their immediate neighbourhood. 



Several opportunities have been afforded me for making 

 trials on this important point ; I say important, because it is 

 a question, the settlement of which may materially influence 

 Gas Companies in the choice of a situation for their works, be- 

 sides influencing consumers, with regard to the company from 

 which they will take their gas. 



