“Shall we not return immediately?”
“No, my dear; it would not be in my power to attend you at present; but join me in the library after dinner; Mr. Twaddleton will now accompany me to the village, and do you remain and enjoy the amusement of your kite.”
It was not until the evening, that Tom and his sisters requested their father to fulfil the promises he had made them in the morning.
“You told us,” said Louisa, “that you would give us some information about the wind; the subject has been puzzling me ever since, for I cannot make out the cause of it.”
“Wind, my love, is nothing more than air in motion; and is produced by a large volume of it flowing in a current, or stream, from one place, or region, to another, and with different velocities.”
“And what can produce these currents?” asked Tom.
“After the explanation of the action of the pump, I do not think that I shall have much difficulty in making you understand the nature of the operations by which wind is occasioned. Suppose a partial vacuum should be formed in any region, would not the neighbouring air immediately rush in to supply the deficiency and restore the balance?”
“Undoubtedly; from the pressure of the air behind it.”
“Heat,” continued Mr. Seymour, “will produce a partial vacuum, by rarefying the air, and thus rendering it lighter; in consequence of which, it will ascend, and the colder air will rush in to supply its place.”
“I do not exactly see why the rarefied air should ascend,” observed Louisa. “It appears to offer an exception to the general law of gravity.”