226 SCIENCE OF COMMON THINGS. 



Difference between anthracite and bituminous coal. 



studied with nearly as great ease and facility as the 

 botany of any given section of the present surface of 

 the earth. 



1505 What occasions the difference between bituminous and anthracite 

 coal? 



Bituminous coal contains a large amount of bitumen 

 and other pitchy volatile substances which readily 

 ignite and burn with smoke and flame. In anthracite 

 coal these substances have been driven out ; it is there- 

 fore a purer variety of carbon, and burns without smoke 

 or flame. 



1506 Are the deposits of coal of very great extent f 



They are ; mineral coal exists in all the great divi- 

 sions of the earth. The largest deposits of coal, how- 

 ever, occur, in the United States, in Pennsylvania and 

 the Yalley of the Mississippi. 



1507 Why will not stones do for fuel as well as coal f 



Because they contain no hydrogen, and little or no 

 carbon. 



1508 Of what are oil, tallow, and wax composed t 



Principally of carbon and hydrogen gas. The solid 

 part is carbon, the volatile part is hydrogen gas. 



1509 At what period of the year does wood contain the greatest amount 

 of water ? 



In the spring and summer, when the sap flows freely 

 and the influence of vegetation is the greatest. 



1510 Why is wood generally cut in the winter season f 



Because at that season there is but little sap in the 

 tissues, and the w r ood is drier than at any other period. 



1511 Why is it difficult to inflame coal or hard wood with the blaze of 

 a match f 



Coal and hard wood on account of their density are 

 good conductors, and carry off the heat of the kindling 

 substance, so as to extinguish it, before they themselves 

 become raised to the temperature necessary for their 

 combustion. 



1513 Why is it easy to ignite light fuel with a smatt blaze f 



Light fuel being a slow conductor of heat kindles 



