A PIECE OF COAL. 



611 



after all, to telling what men have more or less clearly perceived for 

 the last thousand years or more, that coal loill hum. By proper ma- 

 nipulation we may obtain thin slices of coal suitable for microscopic 

 examination, and in this way may demonstrate that a large propor- 

 tion of it is composed of what seems to be crushed and flattened vege- 

 table cells. You are all aware that plants of every kind are made up 

 of little microscopic units called cells, and that these cells differ so 

 much in markings and other characteristics in the different groups of 

 plants that one group may often be distinguished from another by the 

 study of the smallest microscopic fragments. Now, in the coal itself, 

 and often in the ashes that remain after combustion, it is ^^ossible to 



Fig. 1. Lspidodendron modulatom. 



Fig. 2. Lepidodendbon diplotigioides. 



recognize the peculiar cells that characterize certain great divisions of 

 the vegetable kingdom ; and, as this method of study is extended, we 

 are gradually led to the conclusion that coal has somehow been de- 

 rived from plants. Let me say, however, that to reach a conclusion 

 and to entertain an opinion on a question of this or any other kind, 

 where matters of fact are involved, is too serious a thing to bo accom- 

 plished lightly. The color, hardness, and other physical properties of 

 coal, together with the fact that coal-beds are often buried under hun- 

 dreds of feet of rock and soil, may well make us hesitate before accept- 

 ing any such conclusion. Let us attempt the solution of the question 

 in another way : All around the globe, in the middle and higher lati- 

 tudes, are beds of peat. Now, peat, especially when well pressed and 

 dried, presents many very suggestive resemblances to coal. But there 

 is not the slightest difficulty in determining how peat is formed, for we 

 may see the process going on before our eyes. We can study every 

 stage in the process, from the living and dead plants growing and ac- 

 cumulating in the marsh at one end of the series, to the completed peat- 



