74 'TliAXSACTKmS OF THE AmEEICAX INSTITUTE. 



iferous period. A bed of coal is usually composed of the remains of 

 tlie trunks and bark of Sigillaria trees. Examining coal with a 

 microscope, after proper preparation, Ave can see the structure of the 

 wood from which the coal was derived. Of eighty-one distinct 

 seams of coal in Nova Scotia, every one but two or three had Sigil- 

 laria, either in the coal or immediately above or beneath it. The 

 top of a coal seam is merely the debris of the last forest that grew on 

 the swamp where the coal was produced. Great Britain annually 

 consumes 100,000,000 tons of coal, and we know of nothing that will 

 supply its place. The consumption of coal in America is already 

 e(pial to the labor of 150,000,000 horses, and our coal beds are as yet 

 hardly opened. All this power is extracted from the sunbeams of 

 the Paleozoic period. What did these magnificent forests grow for ? 

 There seems to have been no higher animals to enjoy them. We 

 know of no birds that lived among their branches. There were a 

 few insignificant reptiles that crawled beneath them, but we know of 

 nothing higher in that age. What were they created for ? For two' 

 great purposes. First, to purify the atmosphere, so that it might be 

 made suitable for the higher animals that were to live in a future 

 geologic period ; and that very process of purifying the atmosphere 

 was made the means of laying up those enormous stores of fossil fuel 

 upon which so much of our modern civilization is based. See how 

 grand are the economies of nature, preparing far back in geologic 

 periods before man existed, for the existence of the present state of 

 the arts in the world. Next to coal, in its value, comes iron ; and 

 although we are not so dependent upon the coal formation for iron 

 as we are for coal, still we get an immense quantity of iron from the 

 carboniferous rocks, accumulated by the agency of these very plants ; 

 for as they went to decay, and were converted into coal, they helped 

 to gather together the particles of iron out of the clays and sands, 

 and to store them up for us in beds of iron ore. Therefore we owe 

 to the growth of those old forests not only our coal but a large portion 

 of our iron. And wliether we look to the value of the coal in boiling 

 the tea-kettle, of which Prof. Silliman spoke to you in the last lecture, 

 or to the coal and iron which make and feed om* iron horse, and the 

 steam engine of our factories, we owe it all to the primeval plants, 

 or rather the Maker and Creator of these old plants. 



Let me trace these plants a little further back than the period of 

 the coal formation. If we go back from the carboniferous rocks to 

 the Devonian, we shall find a different flora, which no doubt helped 



