When a lava forced upward through the strata reaches the level at which under the law of hydrostatic equilibrium it must stop, we may conceive that it expands along some plane of bedding in a thin sheet, until its horizontal extent becomes so great that it overcomes the resistance offered by the rigidity of its cover, and it begins to uplift it. The direction of least resistance is now upward, and the reservoir of lava increases in depth instead of width. The area of a laccolite thus tends to remain at its minimum limit, and may be regarded as more or less perfectly an index of that limit. In equations 1 and 2, if _f_ = _r_, then _c_^2 _C_{ll}_ = _d c C_ or _c_ = _d_(_C_/_C_{ll}_) (3) That is to say, if the force exerted by the lava is barely sufficient to overcome the resistance to uplift, then the circumference of the laccolite is proportional to the depth of its cover. Or in other words, the (linear) size of a laccolite is proportioned to its depth beneath the surface. If now we return from the faulted cylinder which for simplicity’s sake has been hypothecated, to the actual cylinder which is surrounded by a flexure instead of a fault, can we retain our conclusions? With certain modifications I think we can. The strains developed in deformation by flexure are less easy of analysis than those which arise in faulting, but the two cases are in some degree analogous. The expression (equation 2) for the force which the lava applies to deformation is unaffected by the manner in which the strata yield. The expression (equation 1) for the resistance to deformation by faulting involves two terms, each in its simplest relations; the resistance varies directly as the circumference of the laccolite, and it varies directly as the depth of the cover. In order to pass to an expression for the resistance to deformation by flexure, only one of these terms need be changed. The resistance bears the same relation to the circumference of the laccolite; but it is no longer simply proportional to the depth of the cover. It varies more rapidly. If the covering strata were all of a given thickness, were identical in kind, and were free to slide upon each other without friction, their total resistance to deformation would be equal to the resistance of a single stratum multiplied by the number of strata. But since they are not free to slide one upon another, they sustain each other, and the resistance offered by the combination is greater than that product.