When Sir Wm, Logan made his geological survey of Canada, by order of the British Government, lie came to the conclusion, that from the deposits of that district, there could be no coal in the country. This statement was promulgated with all the weight that his name as an eminent geologist could give it, and consequently was unanimously received. During the last few weeks it has been reported that good coal has been discovered in Canada at a depth of 150 feet from the surface, and consequently many persons feel inclined to doubt the knowledge of the geologist, and seem to regard it as a detraction from his scientific character. Coal is a stratified rock which is composed entirely of organic remains, and the plants which we find in it in the fossil state, and from which we deduce that it has been formed, are not water but land plants ; and although much coal has been the result of plants of marshy growth, and all the remains hitherto discovered in coal are such as would require the moist, carbonic acid atmosphere of the carboniferous period for their support, yet there is no reason why coal may not have been formed in other ways and at another geological epoch. All the beds of coal at present known have an underlaying seam or strata of clay or even sandstone, which has formed the soil on whichthe coal plants grew. Whether the one in Canada has or not we do not know, but we rather suspect it has not. What are the plants that compose the coal ? Monstrous ferrs, gigantic mosses, and magnificent pines have fallen on one another, in a lake of carbonic acid, some still standing erect, while the others lie prostrate around them, the rock which overlies the coal has been deposited on the top of them and they have been pressed into the solid, firm, and compact fuel we call coal. Sir Wm. Logan, we suppose, judging from these well known facts, prophesied the absence of coal in Canada, and he was right, for it was beyond his province as an observer to speculate upon probabilities, but now the coal has been found, it does not show that the above eminent geologist was wrong, it is simply the opening up of a new field for geological research. We have noticed that ooal is now supposed to exist near London, England, a place where no one ever dreamt of finding it, and from a similar accident, Canada may also enjoy the blessings of the possession of this valuable mineral, on which the wealth of a nation so much depends. Let us for the moment imagine a scne, in the ages long since rolled- awaf, which would form a seam of coal in any formation or at any epoch. The spring had been very wet, and the summer's heat had caused malaria and carbonic acid to accumulate in the hollows and valleys ; the lovely autumn bringing on its " sere and yellow leaf " stripped the rich woods of their many-tinted leaves and the winds took them on their wings and spread them as a curtain over the land, local causes decayed the trees and the shrubs died away.the winter covered them with frost and snow, and the rains of spring spread them over soil and sand. Carry this process on and you may have a very respectable seam of coal, where, geologically speaking, no coal ought to be. Geology has to study the principles of nature, she has not yet had time to investigate the accidents, and by some such circumstances as those described, i, e., local or accidental,' the Canada coal, if there be such a material, has been formed. In conclusion, every fact discovered should be turned to some practical use rather than used as a ground of complaint against men of science, as has been the ten. dency of the majority of articles on this sub-ject which we have seen in onr exchanges.