after all, to telling what men have more or less clearly perceived for the last thousand years or more, that coal will burn. By proper manipulation we may obtain thin slices of coal suitable for microscopic examination, and in this way may demonstrate that a large proportion of it is composed of what seems to be crushed and flattened vegetable 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 possible to
| Fig. 1.—Lepidodendron modulatum. | Fig. 2.—Lepidodendron 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 derived 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 be accomplished lightly. The color, hardness, and other physical properties of coal, together with the fact that coal-beds are often buried under hundreds of feet of rock and soil, may well make us hesitate before accepting any such conclusion. Let us attempt the solution of the question in another way: All around the globe, in the middle and higher latitudes, 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 accumulating in the marsh at one end of the series, to the completed peat-
