SOLIDIFIED SUNLIGHT. 149 



XXVI. SOLIDIFIED SUNLIQHT. 



COAL AND COAL-BEDS. 



I SIT by my genial grate, this pinching winter evening, 

 and watch the play of the flames which leap from the coal 

 and play with the draughts of air passing up the chimney. 

 Here is comfort here is peace. How the fierce wind howls 

 about the windows while I enjoy this life-sustaining warmth. 

 Curious, is this coal this combustible rock, wonderful, and 

 abounding in suggestions. This warmth is yielded by com- 

 bustion. This rock burns up. That which burns up is essen- 

 tially carbon, or a hydrocarbon. It is so with petroleum ; it 

 is so with gas; it is so with coal. The source of uncombined 

 carbon is in vegetation. Our carbonates, like limestone, con- 

 tain carbon ; but it is combined with oxygen ; it is already 

 appropriated, not free not in a condition to be burned. The 

 coal must be composed of free carbon, to a large extent 

 mingled, probably with some hydrocarbon. Carbon, as we see 

 in charcoal, burns without any brilliant flame, and without 

 smoke. Hydrocarbon, as we see in kerosene and illuminating 

 gas, burns with a bright flame. The coal in the grate emits a 

 moderately brilliant flame. It is a mass of carbon saturated with 

 some liquid or gaseous, or perhaps, bituminous, hydrocarbon. 

 In any event, we are induced to trace its carbon to a vege- 

 table origin. 



Now, if we look over a pile of coal we shall probably de- 

 tect some indications of vegetable tissue. In some coals of 

 the soft kind, we may find masses of woody fiber black and 

 brilliant, like some charcoal. In some of the shale attached 

 to pieces of coal, or mingled with the coal, are some impres- 

 sions like fern-fronds. If we go to the mines, we even dis- 

 cover stems of moderate sized trees imbedded in the shales 

 above the coal, and occasionally in the coal itself. Again, if 

 we prepare exceedingly thin slices of coal, and remove the 

 black matter by proper treatment, we may detect, by means 

 of the microscope, minute structures, such as belong to vege- 

 tation. All these circumstances then, conspire to convince us 



