CHARLES. "I am very glad that is not my creed, for I should not at all enjoy life with the continual idea of wicked spirits hovering in the air around me. They might as reasonably believe in ghosts."
MRS. WILTON. "In the Indian and China Seas, and in many other parts of the great tropical belt, the periodical winds called 'monsoons' are found. The south-west monsoon prevails from April to October, between the equator and the tropic of Cancer: and it reaches from the east coast of Africa to the coasts of India, China, and the Philippine Islands. Its influence extends sometimes into the Pacific Ocean, as far as the Marcian Isles, or to longitude about 145º east; and it reaches as far north as the Japan Islands. The north-east monsoon prevails from October to May, throughout nearly the same space, that the south-west monsoon prevails in during the former season. But the monsoons are subject to great obstructions by land; and in contracted places, such as Malacca Straits, they are changed into variable winds. Their limits are not everywhere the same; nor do they always shift exactly at the same period, but they are generally calculated upon about the times I have mentioned."
EMMA. "Mamma, are not trade-winds something like monsoons?"
MRS. WILTON. "So far similar that they are confined to a certain region, and are tolerably regular in their operations. The trade-winds blow, more or less, from the eastern half of the compass to the western. Their chief region lies between the tropics from 23-1/2º north to 23-1/2º south latitude, although in some parts of the world they extend farther; but it is only in the open parts of the Pacific and Atlantic Oceans that the true trade-winds blow. These winds shift many degrees of latitude in the course of the year; but skilful navigators usually know where to catch them, and make them serviceable in helping to blow their richly laden vessels 'o'er the glad waters of the bright blue sea.'"
GEORGE. "Do you know the cause of these regular winds, papa? You say learned men try to discover why such things are so, and generally find out causes from their effects."
MR. WILTON. "Exactly so, my boy; and learned women do the same: as an instance, I will quote the learned Mrs. Somerville on this very subject, and give you an excellent reply to your question.
"'The heat of the sun occasions the trade-winds, by rarefying the air at the equator, which causes the cooler and more dense part of the atmosphere to rush along the surface of the earth to the equator, while that which is heated is carried along the higher strata to the poles, forming two currents in the direction of the meridian. But the rotatory velocity of the air corresponding to its geographical situation, decreases towards the poles; in approaching the equator it must therefore revolve more slowly than the corresponding parts of the earth, and the bodies of the surface of the earth must strike against it with the excess of their velocity, and by its reaction they will meet with a resistance contrary to their motion of rotation; so that the wind will appear, to a person supposing himself to be at rest, to blow in a contrary direction to the earth's rotation, or from east to west, which is the direction of the trade-winds.'"
GEORGE. "May I read that to-morrow, papa? I do not quite understand it; and if you have the book, I could read it over and over until I found out the meaning."
MR. WILTON. "You will find it in Mrs. Somerville's 'Mechanism of the Heavens.' If you come to my study to-morrow morning before I leave home, I will assist you in the solution of the difficulties."
MR. BARRAUD. "In an account of Cabul I have read a fine description of the commencement of a monsoon:—'The approach is announced by vast masses of clouds that rise from the Indian Ocean, advancing towards the north-east, gathering and thickening as they approach the land. After some threatening days, the sky assumes a troubled appearance in the evening, and the monsoon sets in generally during the night. It is attended by such a violent thunder-storm as can scarcely be imagined by those who have only witnessed the phenomenon in a temperate climate. It generally begins with violent blasts of wind, which are succeeded by floods of rain. For some hours lightning is seen without intermission: sometimes it only illuminates the sky, and shows the clouds near the horizon; at others, it discovers the distant hills, and again leaves all in darkness; when, in an instant, it reappears in vivid and successive flashes, and exhibits the nearest objects in all the brightness of day. During all this time the distant thunder never ceases to roll, and is only silenced by some nearer peal, which bursts on the ear with such a sudden and tremendous crash, as can scarcely fail to strike the most insensible heart with awe. At length the thunder ceases, and nothing is heard but the continued pouring of the rain and the rushing of the rising streams.'"