It is true that you can more or less imitate the forms of cloud with explosive vapour or steam; but the steam melts instantly, and the explosive vapour dissipates itself. The cloud, of perfect form, proceeds unchanged. It is not an explosion, but an enduring and advancing presence. The more you think of it, the less explicable it will become to you.
132. That this should yet be unexplained in the kingdom of the air is, however, no marvel, since aspects of a similar kind are unexplained in the earth, which we tread, and in the water which we drink and wash with. You seldom pass a day without receiving some pleasure from the cloudings in marble; can you explain how the stone was clouded? You certainly do not pass a day without washing your hands. Can you explain the frame of a soap-bubble?
133. I have allowed myself, by way of showing at once what I wanted to come to, to overlook the proper arrangement of my subject, and I must draw back a little.
For all his own purposes, merely graphic, we say, if an artist’s eye is fine and faithful, the fewer points of science he has in his head, the better. But for purposes more than graphic, in order that he may feel towards things as he should, and choose them as we should, he ought to know something about them; and if he is quite sure that he can receive the science of them without letting himself become uncandid and narrow in observation, it is very desirable that he should be acquainted with a little of the alphabet of structure,—just as much as may quicken and certify his observation, without prejudicing it. Cautiously, therefore, and receiving it as a perilous indulgence, he may venture to learn, perhaps as much astronomy as may prevent his carelessly putting the new moon wrong side upwards; and as much botany as will prevent him from confusing, which I am sorry to say Turner did, too often, Scotch firs with stone pines. He may concede so much to geology as to choose, of two equally picturesque views, one that illustrates rather than conceals the structure of a crag: and perhaps, once or twice in his life, a portrait painter might advantageously observe how unlike a skull is to a face. And for you, who are to use your drawing as one element in general education, it is desirable that physical science should assist in the attainment of truth which a real painter seizes by practice of eye.
134. For this purpose I shall appeal to your masters in science to furnish us, as they have leisure, with some simple and readable accounts of the structure of things which we have to draw continually. Such scientific accounts will not usually much help us to draw them, but will make the drawing, when done, far more valuable to us.
I have told you, for instance, that nobody—at least, no painter—can at present explain the structure of a bubble. To know that structure will not help you to draw sea-foam, but it will make you look at sea-foam with greater interest.
I am not able now to watch the course of modern science, and may perhaps be in error in thinking that the frame of a bubble is still unexplained. But I have not yet met, by any chance, with an account of the forces which, under concussion, arrange the particles of a fluid into a globular film; though, from what I know of cohesion, gravity, and the nature of the atmosphere, I can make some shift to guess at the kind of action that takes place in forming a single bubble. But how one bubble absorbs another without breaking it; or what exact methods of tension prepare for the change of form, and establish it in an instant, I am utterly at a loss to conceive.
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.