“Among these rocks and stones, methinks I see More than the heedless impress that belongs To lonely nature’s _casual_ work; they bear A semblance strange to Power intelligent, And of Design not wholly worn away. And I own Some shadowy intimations haunt me here, That in these shows a chronicle survives Of purposes akin to those of man, Measuring through all degrees, until the scale Of time and conscious nature disappear, Lost in unsearchable eternity.”—WORDSWORTH. We will now proceed to the diagram to which we have made allusion, and which represents an ideal section of the earth’s crust as the various formations are there found arranged. (Diagram II.) [Illustration: DIAGRAM II. ] Here, in the words of another writer, we would add for the reader’s guidance, that “the unstratified or igneous rocks occur in no regular succession, but appear amidst the stratified without order or arrangement; heaving them out of their original horizontal positions, breaking up through them in volcanic masses, and sometimes overrunning them after the manner of liquid lava. From these circumstances they are, in general, better known by their mineral composition than by their order of occurrence. Still it may be convenient to divide them into three great classes; _granite_, _trappean_, and _volcanic_—_granite_ being the basis of all known rocks, and occurring along with the primary and transition strata; the _trappean_, of a darker and less crystalline structure than the granite, and occurring along with the secondary and tertiary rocks; and the _volcanic_, still less crystalline and compact, and of comparatively recent origin, or still in process of formation.” This the student will observe by another reference to the previous diagram; but, in looking at the one now before him, we must also add for his further guidance,—for we are presuming that we address those who need initiation into the rudiments of this science, and the circumstance that we never met with a preliminary treatise that quite satisfied us, or helped such intelligent youth as were prying into the apparently cabalistic mysteries of the earth’s structural divisions, is one strong inducement to the present undertaking;—we must add, that “it must not be supposed, however, that all the stratified rocks always occur in any one portion of the earth’s crust in full and complete succession as represented” in Diagram II. “All that is meant is, that such would be their order if every group and formation were present. But whatever number of groups may be present, they never happen out of their regular order of succession; that is, clay-slate never occurs above coal, nor coal above chalk. Thus in London, tertiary strata occupy the surface; in Durham, magnesian limestone; in Fife, the coal measures; and in