Hardman — On Analysis of Coals and Iron-stones. 535 



English coal in point of purity and heating power. They are all 

 highly bituminons, and yield such a quantity of gaseous matter that 

 any of them, except the Derry coal, might be used with great advan- 

 tage in Ireland for gas manufacture, with profit, both to the colliery 

 owner and to the gas company : a point which ought to be thought 

 of if, as I hope, these coals some day come to be properly and exten- 

 sively mined. 



The heating power is extremely high; 10 to 11 lbs. of water eva- 

 porated is considered very good work for 1 lb. of coal ; nearly all these 

 give over 12, the best of them very nearly 13 lbs. The heating power 

 was determined directly by Thompson's very elegant and simple appa- 

 ratus. This is both more exact than the methods of calculation from 

 the ultimate composition, or by actual experiments with a furnace 

 and boiler, and infinitely more convenient than the latter process. 



The analyses show that several of these coals contain an excessive 

 amount of water, e. g., the Creenagh, Annagher, and Bottom Lurgaboy 

 coals. This, however, is, I think, entirely due to the state of the pits ; 

 the specimens from the two former seams being obtained from pits lite- 

 rally swimming in water, which were either surrounded with old work- 

 ings, or only on the very outcrop of the coal. It is not unlikely that 

 under more favourable conditions this item would be much diminished ; 

 and it must be remembered also, that none of the pits at present 

 being worked on the coals enumerated herein are sunk on the best 

 portions of the seams, or under anything like favourable arrangements. 



One thing worth noticing in these coals is the complete proportion 

 between their specific gravity and the amount of ash they contain. 

 It has been a subject of no little discussion as to whether there is any 

 relation between the amount of ash and the specific gravity, and I 

 find it stated in Kuapp's Technicology '^' that no direct connection can 

 be deduced. However, Professor Johnson, a well-known American 

 geologist and chemist, is referred to as believing " such to be the case 

 with coal from the same coal-field, and considers the specific gravity 

 to be an index of the purity of the coal. In analysing anthracites 

 from Beaver Creek, Luzerne County (Pennsylvania), he found in four 

 varieties the following relative quantity of ash : — 



fBEAVER Cheek, Penktstlvania. 





Specific Gravity. 



Ash per cent. 



1 



2 

 3 



4 



1-560 

 1-594 

 1-613 

 1-630 



1-28 

 4-00 

 5-01 

 5-063 



* Knapp's Chemical Technicology. Drs. Eonald's and Eichardson, vol. 1, 

 pt. 1, p. 47-8 (1855). 



t It must be remembered that tlic specific gravity of anthracite is always 

 higher than that of bituminous coal. 



