Scientific Lectures. 75 



to purify the air, and prepare the world for the carboniferous flora. 

 We have in Canada a bed of coal two or three inches thick, belonging 

 to that epoch, and it is the only one I know of in America. In this 

 di-awing, some of the plants of that period are represented ; and here 

 you find the Sigillaria, the Lapidodendi'on, the Calamites, the pines, 

 &c., as in the latter period ; so that you see that the Devonian flora 

 was really not very difierent from that of the carboniferous period. 

 The species are mostly different, but the generic forms are the same. 

 As a whole the Devonian flora may be characterized as less massive and 

 magnificent, more delicate and slender in its proportions ; not less beau- 

 tiful, but less useful, perhaps, in the accumulation for us of vast stores 

 of fuel. If we go down below the Devonian rocks into the Silurian, 

 we find a few plants ; but in the lower Silurian formation we hardly 

 find any traces of plants. jSTearly all the rocks kno^m to us of that 

 age were marine rocks. Prof. D. was not hopeless of the Eozoic 

 period even, We have as yet found no plants there ; but we have 

 found carbon. We have found plumbago ; and even in later forma- 

 tions the remains of plants have sometimes been converted into black 

 lead. We have inunense quantities of graphite or black-lead in the 

 Eozoic strata, occurring in beds, so as much to resemble the remains 

 of plants. They may have been sea plants. If they were land plants 

 we may guess what they were — Anophytes and Thallophy tes, gigantic 

 mosses and gigantic lichens. If we were to walk among those 

 ancient forests of mosses, if tbey really did exist, we should be in a 

 world something like what this would appear to an insect creeping 

 upon the mosses of our woods. I have given you but a faint outline 

 of a great subject, on which treaties might be and have been written, 

 which would aff'ord the material for a course of lectures more interesting 

 than a single one can possibly be. The chief interest of the subject, 

 no doubt, is to the botanist and geologist. The vegetable kingdom 

 now is most beautiful and most varied, especially when we look at it 

 as presenting forms of plants adapted to every climate and every 

 situation upon the earth, all of them finding their proper place and 

 their own due season. But the subject before us carries us back into 

 geologic times, and shows us a plan too large to be realized on one 

 earth. The plan of the Creator was so vast that the whole surface 

 of the earth was not big enough to hold it. It required a series of 

 earths, one after the other, to develop it, just as it has required a 

 series of ages to develop the history of the human race, AYe have in 

 these old plants something that adds enormously to the variety of the 



