Page:Popular Science Monthly Volume 47.djvu/878

860 are for a moment alarmed because you have broken a mirror; but among a great portion of mankind, including a section of the poor of enlightened countries, the smaller superstitions make up a real and heavy burden. They keep up a permanent distrust in the goodness of Providence, and a watchfulness to avoid evils from unknown forces which is most enfeebling. A French or Italian peasant will do nothing that is opposed to certain apothegms registered in his mind as dogmas, and an Asiatic peasant is bound hand and foot by a whole system of beliefs in omens which cramp his energies as much as even the rabbinical views of the law as to anise and cummin cramped the energies of the Jews in the time of Christ. There is not an Asiatic in the world who would dare go dead against the warnings of his horoscope, and very few Europeans of the Continent would stride forward resolutely in an undertaking the beginning of which has been marked by a stumble or a failure. Even in England this special idea about omens has amazing influence, as have also the other beliefs in premonition or presentiment. We all know the annoyance to which the belief in the superstition about thirteen subjects English dinner-goers, while on the Continent it is difficult, and in Paris impossible, to let a house with the number thirteen on the door. Even the iron logic of French functionaries gives way before that belief, and proprietors of rows are permitted to register the thirteenth house as 12 B.

Heavy Rainfall and Ship Canals.—The best series of rainfall observations in Central America, according to Prof. M. W. Harrington, is that taken at San José, Costa Rica, by Prof. Enrique Pettier. Several other series are nearly as good. The greatest hourly rainfall observed there was l·9 inches, or at a rate of forty-six inches—or nearly four feet—per day. "The results of such enormous falls of rain have often been described and can easily be imagined. The dry stream beds or quebradas, very common on the plateaus, are rapidly filled; the water comes down in a wall several feet high; the camping place, two or six feet above the water, is overflowed, and soon the new camping place, hastily sought in the dark and several feet higher, is also overflowed. In such a country as Mosquitia dry stream beds become rivers, marshes change to lakes, and the natives temporarily take to the trees or to their boats. While all this is striking, it is by no means unparalleled in the temperate regions. . . . The difference between such falls of rain id the tropics and in the temperate zones is chiefly that in the latter they are occasional, while in the tropics they are customary. These conditions are especially interesting from the standpoint of the possible ship canals in Central America. . . . It must be acknowledged that the conditions at Suez, Sault St. Marie, and the Welland Canal are in this respect very favorable, for in them the question of sudden floods does not enter. It enters in the case of the great ship canal of St. Petersburg-Cronstadt and of those of the Ganges-Brahmaputra Delta; but in these cases there are no changes of level sufficient to make the use of locks necessary. Indeed, the use of locks on ship canals where feeders are subject to sudden and violent floods appears to present a new engineering problem, first met in the Panama Canal."

House and Room Ventilation.—Draughts in houses may be defined, Dr. G. V. Poore says, as currents of air rushing in at the many places through channels that have insufficient area. The only way to cure draughts is to place inlets of sufficient area in proper positions. When building a house, one might place louvre ventilators in the walls between room and passage at a height of six and a half feet above the floor. The alteration of a door panel into a ventilator costs only a trifle. In the author's experience it is a most excellent way of ventilating a room, always provided that the air of the passages be wholesome. Windows should extend to within a few inches of the ceiling, and should open at the top. If the room be twelve or thirteen feet high, and the windows go to the top, then the window becomes unmanageable from its height, and the opening at the top, though theoretically possible, is seldom put in practice. The wholesomeness of a room depends very much upon the rapidity with which the air within it can be renewed—the facility, in short, with which one can give it a blow-out. This depends upon the relation of window area to entire capacity. Windows should be so constructed that they can be easily