256 Practical Notes on Burdwan Coal. [No. 4. 



Indian Coal, except that it is a troublesome coal — that it clinkers 

 excessively ; and sometimes, where they get a large proportion of 

 inferior kinds in their lot, — that the steam cannot be kept up with 

 the Burdivan Coal — they are clamorous for English Coal, — and get it. 

 "We are thus in very many cases trying to burn Indian Coal on 

 English grates! and are always complaining that we do not succeed. 



9. I have succeeded, and on a large scale, when boiling sugar in 

 open pans, in obtaining, not the duty of English Coal from Burdwan 

 Coal, but something much higher than could be looked for — say 

 within ten or fifteen per cent, of English Coal, and without much 

 more trouble, except in a little more work with the picker, which 

 the men carefully attended to because the furnaces being con- 

 structed to burn their own smoke, which they did very completely, 

 the men, who were well paid, were liable to a fine, if the smoke- 

 flag was seen for any length of time at the top of the chimney. 



10. And I managed this by the following simple expedient. 

 Whenever I had Burdwan Coal to burn, I took out one of the bars 



and steadied the others by bits of scrap iron put in between their 

 shoulders. This increased the air-way and the Burdivan Coal then 

 burnt freely, but of course gave a larger quantity of its white ash. 



11. The reason of this is simple enough. If we suppose a given 

 quantity of English, or Welsh, Coal to perform its highest duty as a 

 steam coal, in any given time, with, say a certain number of cubic 

 feet of air, which we will call 1000, we have first a coal containing 

 say 2\ per cent, of earthy matter requiring this amount of air in a 

 given time. 



12. But it is clear that a coal containing 12 or 15 per cent, will 

 require a much larger amount of air in the same time. We do not 

 know how much, or what is the proportion in which the earthy 

 matter obstructs the combustion of the coal in which it is contained ; 

 but we do certainly know that every question of combustion from 

 Cannel Coal to Anthracite is a question of draft, and of air-way ; of 

 the rapidity of the passage of the air, which is the draft, and of the 

 size of the spaces through which this draft passes, which is the air- way. 



13. Now as we can only alter our funnels by reducing them, 

 which we do not want to do, the draft is a constant quantity, and 

 hence the resource is that which I have spoken of above — to increase 



