We have here evidently natural causes of a very marked division in schools of architecture: one group composed of buildings whose shafts are either of a single stone or of few joints; the shafts, therefore, being gracefully tapered, and reduced by successive experiments to the narrowest possible diameter proportioned to the weight they carry: and the other group embracing those buildings whose shafts are of many joints or of small stones; shafts which are therefore not tapered, and rather thick and ponderous in proportion to the weight they carry; the latter school being evidently somewhat imperfect and inelegant as compared with the former. It may perhaps appear, also, that this arrangement of the materials in cylindrical shafts at all would hardly have suggested itself to a people who possessed no large blocks out of which to hew them; and that the shaft built of many pieces is probably derived from, and imitative of the shaft hewn from few or from one. § VIII. If, therefore, you take a good geological map of Europe, and lay your finger upon the spots where volcanic influences supply either travertin or marble in accessible and available masses, you will probably mark the points where the types of the first school have been originated and developed. If, in the next place, you will mark the districts where broken and rugged basalt or whinstone, or slaty sandstone, supply materials on easier terms indeed, but fragmentary and unmanageable, you will probably distinguish some of the birthplaces of the derivative and less graceful school. You will, in the first case, lay your finger on Pæstum, Agrigentum, and Athens; in the second, on Durham and Lindisfarne. The shafts of the great primal school are, indeed, in their first form, as massy as those of the other, and the tendency of both is to continual diminution of their diameters: but in the first school it is a true diminution in the thickness of the independent pier; in the last, it is an apparent diminution, obtained by giving it the appearance of a group of minor piers. The distinction, however, with which we are concerned is not that of slenderness, but of vertical or curved contour; and we may note generally that while throughout the whole range of Northern work, the perpendicular shaft appears in continually clearer development, throughout every group which has inherited the spirit of the Greek, the shaft retains its curved or tapered form; and the occurrence of the vertical detached shaft may at all times, in European architecture, be regarded as one of the most important collateral evidences of Northern influence.