Here, I think, then, is one familiar matter which up to the possible point, science might condescendingly interpret for us. The exhaustion of the film in preparation for its change: the determination of the smaller bubble to yield itself up to the larger; the instantaneous flash into the new shape, and the swift adjustment of the rectangular lines of intersection in the marvellous vaulting--all this I want to be explained to us, so that, if we cannot understand it altogether, we may at least know exactly how far we do, and how far we do not. 135. And, next to the laws of the formation of a bubble, I want to see, in simple statement, those of the formation of a bottle. Namely, the laws of its resistance to fracture, from without and within, by concussion or explosion; and the due relations of form to thickness of material; so that, putting the problem in a constant form, we may know, out of a given quantity of material, how to make the strongest bottle under given limitations as to shape. For instance,--you have so much glass given you: your bottle is to hold two pints, to be flat-bottomed, and so narrow and long in the neck that you can grasp it with your hand. What will be its best ultimate form? 136. Probably, if you thought it courteous, you would laugh at me just now; and, at any rate, are thinking to yourselves that _this_ art problem at least needs no scientific investigation, having been practically solved, long ago, by the imperative human instinct for the preservation of bottled stout. But you are only feeling now, gentlemen, and recognizing in one instance, what I tell you of all. Every scientific investigation is, in the same sense as this would be, useless to the trained master of any art. To the soap-bubble blower, and glass-blower,--to the pot-maker and bottle-maker,--if dexterous craftsmen, your science is of no account; and the imp of their art may be imagined as always looking triumphantly and contemptuously, out of its successfully-produced bottle, on the vain analysis of centrifugal impulse and inflating breath. 137. Nevertheless, in the present confusion of instinct and opinion as to beautiful form, it is desirable to have these two questions more accurately dealt with. For observe what they branch into. The coloured segments of globe out of which foam is constituted, are portions of spherical vaults constructed of fluent particles. You cannot have the principles of spherical vaulting put in more abstract terms. Then considering the arch as the section of a vault, the greater number of Gothic arches may be regarded as the intersections of two spherical vaults. Simple Gothic foliation is merely the triple, quadruple, or variously multiple repetition of such intersection.