“Consider, my dear boy, the frailty of their structure, and I think that the precarious tenure of their existence will cease to astonish you; indeed, the wonder is, that they should endure so long. The film of which they consist is inconceivably thin,[39] so that the slightest impulse will be apt to rupture them; besides which, there must be a considerable evaporation going on from their surface, while the contraction of the contained air, from change of temperature, must also tend to limit their duration. You must likewise remember that the soap-lather will have a tendency to gravitate towards the depending part of the bubble, and, consequently, by quitting the upper portion, to render it of still greater tenuity. This last effect might, perhaps, be obviated, in some measure, by giving a rotatory motion to the bubble around its axis; but this, again, would accelerate the evaporation: which, after all, is the principal cause of the shortness of its duration; so that, unless this latter effect could be remedied, I despair of suggesting any expedient by which the frail existence of our airy structure could be protracted. You must, therefore, seek, from a succession of bubbles, the prolongation of an amusement which no single one can afford you.” “And could not the evaporation be prevented?” asked Tom. “If the bubble were blown in a glass vessel, and the latter immediately closed after the operation, it would remain for some time; I remember having once preserved a bubble in this manner for a very considerable period.” Tom, however, did not appear to relish this scheme; as, he said, the great sport arose from watching the movements of the floating bubble; the boy, accordingly, determined to pursue the amusement in the usual manner. His father, however, observed, that by mixing a solution of isinglass with the soap lather, larger, as well as more lasting bubbles might be blown; and Tom accordingly determined to make the experiment. During this dialogue, little John had succeeded, for the first time, in launching the airy bauble. Imagination always tinges the objects of our first efforts with brilliant tints: no wonder, therefore, that John, with a shout of ecstasy, should have pronounced it to have been the most beautiful bubble he had ever seen: in truth, the sun was shining brightly, and the colours thus produced very justly excited the admiration of all present. “I cannot understand the cause of these beautiful colours,” said Louisa.