Although many theories have been suggested to account for the formation of coal-beds, all of which agree in the vegatable origin of the coal itself, none have yet apperared which meet many of the difficulties which surround the subject of their origin, and probably they have been deposited under so many varying conditions that no one supposition would account for the difference in the constituents of the mineral, or for the mode of its formation in different localities. From the Stigmaria found in the underclay, in the great majority of cases, it seems fair to assume that the vegetation from which the coal above it was formed, grew where the coal is found, and there are other reasons for coming to the some conclusion in these cases, but in some places, where the underclay is wanting, this may be doubtful.