“Most liquids, by agitation, exhibit the appearance of froth, in consequence of the escape of the air in small bubbles, which had been forced into them by the operation. If, however, the liquid be viscid and tenacious, like soap and water, the air is, as it were, imprisoned in the mass, producing the appearance which is commonly called lather.”
Louisa here enquired “Whether the air did not escape with more or less readiness, according to the degree of resistance it met with in the liquid?”
“I thank you,” said Mr. Seymour, “for having so kindly assisted me in the explanation.”
Louisa smiled at this mark of her father’s approbation, and Mr. Seymour proceeded,--“It is on that very account, that spirit, after it has been shaken, so soon regains its transparency: for, in consequence of the superior lightness of that fluid, and the little cohesion which subsists between its particles, the air makes a rapid escape. In like manner we may account for the spongy appearance which gives such superiority to our bread; in that case, the air disengaged during the fermentation of the dough cannot escape through so viscid a mass; it therefore remains, and thus produces the eyes or bubbles, which you may always observe in every well-baked loaf.”
“See, papa,” exclaimed Tom, “the bubbles which John has blown in the lather, are not round, but angular figures--they appear to be like the hexagons which we used to cut out for our papyro-plastics.”
“They are certainly hexagonal,” replied Mr. Seymour; “and the form arises from the pressure of the bubbles upon each other. The same appearance is to be seen in the pith of vegetables, when examined by the microscope, and is the result of the general reaction of the solid parts upon each other: but let us proceed to blow some bubbles. Plunge the bowl of the tobacco-pipe into the lather.”
Tom obeyed his father’s directions, and blowing through the stem produced a bubble.
“See! see!” cried Louisa, “what a beautiful bubble! but there is a quantity of soap hanging to its under part.”
“I will take it off with my finger,” said Mr. Seymour.
“There it goes!” exclaimed Tom.