SO COMBUSTION AND FUELS 



No. 2 passes over J-in. mesh and through &-in. mesh. Buck- 

 wheat No. 1 passes over ^-in. mesh and through J-in. square 

 mesh. Pea passes over -in. mesh and through f-in. square 

 mesh. Chestnut passes over f-in. mesh and through If-in. 

 square mesh. Stove passes over If -in. mesh and through 2-in. 

 square mesh. Egg passes over 2-in. mesh and through 2 f-in. 

 square mesh. Broken passes over 2 f-in. mesh and through 

 3i-in. square mesh. Steamboat passes over 3J-in. mesh and out 

 of screen. Lump passes over bars set from 3J to 5 in. apart. 



Semianthracite Coal. Semianthracite coal contains from 

 87.5 to 92.31% of fixed carbon and from 7.69 to 12.5% of vola- 

 tile hydrocarbons. It kindles easily and burns more freely 

 than the true anthracite coal; hence, it is highly esteemed as 

 a fuel. It crumbles readily and may be distinguished from 

 anthracite coal by the fact that when just fractured it will soil 

 the hand, while anthracite will not do so. It burns with very 

 little smoke. Semianthracite coal is broken into different sizes 

 for the market; these sizes are the same and are known by the 

 same trade names as the corresponding sizes of anthracite coal. 



Semibituminous Coal. Semibituminous coal contains from 

 75 to 87.5% of fixed carbon and from 12.5 to 25% of volatile 

 hydrocarbons. It differs from Semianthracite coal only in 

 having a smaller percentage of fixed carbon and more volatile 

 hydrocarbons. Its physical properties are practically the 

 same, and since it burns without the smoke and soot emitted 

 by bituminous coal, it is a valuable steam fuel. Semibitumi- 

 nous and bituminous coals are known to the trade by the fol- 

 lowing names: Lump coal includes all coal passing over screen 

 bars 1J in. apart. Nut coal passes over bars f in. apart and 

 through bars li in. apart. Pea coal passes over bars | in. 

 apart and through bars f in. apart. Slack includes all coal 

 passing through bars f in. apart. 



Bituminous Coal. Bituminous coal contains from to 

 75% of fixed carbon and from 25 to 100% of volatile hydro- 

 carbons. It may be divided into three classes, whose names 

 and characteristics are as follows: Caking coal is the name 

 given to coals that, when burned in the furnace, swell and fuse 

 together, forming a spongy mass that may cover the whole 

 surface of the grate. These coals are difficult to burn, because , 



