It cannot be too widely known, or too often pressed on the attention, especially of the young, that a true acquaintance with science, so delightful to its possessors, is not to be acquired at second-hand. Text-books and manuals are valuable only so far as they supplement and direct our own observations. A man whose knowledge of Nature is derived solely from these sources, differs about as much from one who betakes himself to Nature herself, as a dusty, desiccated mummy does from a living man. You have the same bones and sinews in both; but in the one they are hard and dry, wholly incapable of action; in the other they are instinct with freshness and life. He who would know what physical science really is, must go out into the fields and learn it for himself: and whatever branch he may choose, he will not be long in discovering that a forenoon intelligently spent there must be deemed of far more worth than days and weeks passed among books. He sees the objects of his study with his own eyes, and not through "the spectacles of books;" facts come home to him with a vividness and reality they never can possess in the closet; the free buoyant air brightens his spirits and invigorates his mind, and he returns again to his desk or his workshop with a store of new health and pleasure and knowledge. Geology is peculiarly rich in these advantages, and lies in a manner open to all. No matter what may be the season of the year, it offers always some material for observation. In the depth of winter we have the effects of ice and frost to fall back upon, though the country should lie buried in snow; and then when the longer and brighter days of spring and summer come round, how easily may the hammer be buckled round the waist, and the student emerge from the dust of town into the joyous air of the country, for a few delightful hours among the rocks; or when autumn returns with its long anticipated holidays, and preparations are made for a scamper in some distant locality, hammer and note-book will not occupy much room in the portmanteau, and will certainly be found most entertaining company. The following pages--forming a digest of the Carboniferous rocks--may, perhaps, in some measure, guide the explorations of the observer, by indicating to him the scope of geological research, the principles on which the science rests, and the mode in which it is pursued. But I repeat, no book, no lecture-room, no museum, will make a geologist of him. He must away to the fields and study for himself, and the more he can learn there he will become the better geologist.