different Kinds of Coal for the purpose of Illumination. 43 



their gases, is as 2-23 for the one quantity, and 25 for the 

 other ; taking the average, we state the vahie of English 

 cannel coal as 2-35, or say 2i to Newcastle caking coal 

 as 1. 



Scottish Parrot. — While the English cannel coals may be 

 considered as of the same value at different places, it is not 

 so with the Scottish pai-rot. I have said that it varies very 

 much in different districts ; and hence, though the value of 

 the gases with which the different towns are supplied is very 

 nearly the same in all, owing to mixtures of coals of superior 

 and inferior quality being used, yet the value of the different 

 coals varies considerably, owing to the quality and quantity 

 of gas which they afford varying. 



I have taken the average value of the Scottish parrot-coal 

 gas as 5, compared to that from the English caking coal as 

 1. The quantity of gas from the latter being 8000, and that 

 from the former 9500, then the value of the coals for the 

 amount of light afforded by the combustion of their gases, is 

 as 6*1 to 1. 



The above must be considered as the value of the Scottish 

 parrot coals on an average, or as used in their mixed state, 

 as is generally done by gas companies. It may be interest- 

 ing to state the value of some of the coals themselves. The 

 poorest Scottish parrot I have yet examined, yielded only 

 9000 feet of gas, the value of which was 2-2 to that of the 

 English caking-coal gas as 1 ; making, accordingly, the value 

 of the coal for yielding light only 2-5, or very nearly so. 



The value of the gas from Lesmahago coal, which by gas- 

 makers is gent-rally considered the best in the market, I have 

 found to be (y-Q to the English caking-coal gas as 1 ; the quan- 

 tity of gas being 113 to 1 ; accordingly the value of Lesma- 

 hago coal is at least 7 to 1. Since the publication of my 

 paper in 1842, I have had more valuable coals submitted to 

 trial ; but as these are not, so far as I know, in the market at 

 present, tliey must not be taken into account in fixing the 

 average value of Scottish parrot coal. As above stated, we 

 must still consider the value of this coal as about 6, to the 

 Newcastle caking as 1 ; of course its value compared with tlie 

 English cannel, will be 2-6 to 1. 



