86o 



THE POPULAR SCIENCE MONTHLY. 



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 super- 

 stitions 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 peas- 

 ant will do nothing that is opposed to cer- 

 tain 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 under- 

 taking 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 be- 

 liefs 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 func- 

 tionaries 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 Cen- 

 tral America, according to Prof. M. W. Har- 

 rington, is that taken at San Jose, Costa 

 Rica, by Prof. Enrique Pettier. Several 

 other series are nearly as good. The great- 

 est 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 qucbradas, 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 wa- 

 ter, is overflowed, and soon the new camp- 

 ing 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 tem- 

 perate 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 pos- 

 sible 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 posi- 

 tions. 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 prac- 

 tice. 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 ma- 



