29, On the Materials vfcd 



1:40 pounds of fplint (lightly mixt yield 1000 lbs. coaks, lofs 1240 lbs. 



:24a - - of pure fplint ... UO o - - lofs 1 1 *o lbs. 



This great weight thus loft is chiefly carried off in fmoke. 

 If a veffel is placed, filled with cold water, in the midft of one 

 of thefe maffy columns of vapour, before the fire has pene- 

 trated to the furface of the heap, a confiderable quantity of 

 tar will condenfe upon its external furface : this will con- 

 tinue to increafe till fuch time as the water affumes the tem- 

 perature of the fmoke. At many ironworks from 300 to 

 1000 tons of coals are thus weekly reduced to cinder. What 

 a prodigious quantity of bituminous vapour, furcharged with 

 tar, ammoniac and oil, muft for the prefent be loft ! ! 



I have found the fpecific gravities of the above coals and 

 coaks to be as follow ; 



Sp. Gr. lbs. Avoirdup. Sp. Gr. 



Bituminous coal - im8oi — Cubic foot 71*60 — thecoak '3985 



free coal and little fplints i'i954 — Ditto 73-75 —Ditto "4793 



Mixture fplint and free 1*2307 — Ditto 76*9 1 — Ditto "6547 



Pure fplint - - 1-3121— Ditto Ez-o: — Ditto "9533 



P.efults obtained from the fame coals by ignition unexpofed 

 to external air : 



Bituminous coal icopts.comp. of Bit". 51-5 Carb. 3-65Afh.i2 S.g. -45.34 



Free coal, pure - - - - 44-8 - 53-45 - 1,75- -4827 



Mixture of free and fplint - - 45-5 - 512 - 3,3 --6698 



Pure fplint .... 42-4 - 53-4 - 4,2 -"9599 



The comparative quantity of coaks produced from 100 parts 

 in both ways will ftand thus : 



Bituminous coal coaked in air 31-20 Coaked, unexpofed to air 49*5 



Pure free coal an ;1 a little fplint 37-50 Ditto - 55'* 



Splint and free coal * - 44'59 Ditto - . - 34-5 



Splint, pure - - - 49"'° Ditto - 57-6 



Thefe experiments were performed on coals found imme- 

 diately in this neighbourhood, part of which are ufed in the 

 manufacturing of iron. The qualities of coal, however, even, 

 of^he fame feam, vary in different places. 



Iron* 



