Different Kinds of Coal for the purpose of Illuminntion. 41 



trials, amounting to upwards of 20, may be taken as 15, that 

 is, very nearly double of that with the English cannel coal ; 

 and 3'46 as great as that with the English caking coal ; thus 

 making the illuminating power, English caking 1, English 

 cannel 1-85, Scottish cannel 3"46. The English cannel being 

 1, the Scottish cannel is 2, or very nearly so. 



The trials with the same gases shew the durability to vary 

 from 56' to 94'. with the two exceptions above mentioned, it 

 was not below 70', — the average of the trials was 80' ; making 

 the durability as 1-58 to the Newcastle, and 1'48, or 1-45 to 

 the average of the English cannel as 1. Now, taking both 

 into account, the value of the Scottish parrot-coal gas, bulk 

 for bulk, for affording light in these trials, is as 5'46 to New- 

 castle, as 1 and 2-68 to English parrot, as 1. 



Since these experiments were made public, I have been en- 

 gaged in a very extensive series of trials with parrot coals 

 procured from Fifeshire, the Lothiaus, and the Western dis- 

 tricts of Scotland, so as to ascertain the value of the gases 

 which they afford. The gases were manufactured with the 

 experimental apparatus, and under a variety of circum- 

 stances, so as not only to secure accuracy, but also to ob- 

 serve how far the manufacture, &c. is affected by a difference 

 in the mode of conducting it. It is not my intention to al- 

 lude to these farther than to state, that, taking the average 

 of the trials, amounting to upwards of 40, I found the chlo- 

 rine test, and the durability to be very nearly the same as 

 those given above. 



Witli regard to the gas with which the towns in Scotland 

 are supplied, I have already said, that in manufacturing it, a 

 mixture of different kinds of coal is employed, according to 

 the situation of the town, and the supply that can be ob- 

 tained. At Edinburgh, the coal is chiefly from the Lothians 

 and from Fifeshire. At Glasgow, it is got from Lesmahago, 

 Kelvinside, Wilsontown, &c. At Greenock, Monkland and 

 Skaterig coals are employed. In the towns in the north of 

 Scotland they are obtained chiefly from Lesmahagow and 

 Fifeshire. 



The price of coals varies according to the kind of coal. At 

 Edinburgh and in the west, it is from about 20s. to 23s. per 



