Page:Popular Science Monthly Volume 46.djvu/881

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Their circular walls consisted of wattle and daub; three or four stout poles with forked ends protruded above the rest of the wall to receive the ribs of the umbrella-shaped roof, this roof being first covered with a plastering of mud, and then thatched with long grass. Some of the granaries measured six feet in height to the eaves and six feet in diameter, but they varied in size to suit the area of level rock available on the several bowlders. The interior is partitioned, by walls of wattle and daub, into three or sometimes four compartments, to separate the bulk of the grain. The building is covered with an inner roof of sticks plastered into mud before the outer roof is put on. A small door or manhole made from an oval or round slab of rock, and with a handle fitted to it, is let into the wall of the hut about four feet above the ground. The outside ornamentation of nearly all the huts consists of moldings representing the female breast—an emblem of plenty—and a longitudinal bar in relief above them, the significance of which is open to conjecture. In the aggregate these granaries were capable of storing upward of six thousand bushels of grain."

Height of Ocean Wares.—Dr. G. Schott, studying the form and height of the waves of the deep sea, found that under a moderate breeze their velocity was 24·6 feet per second, or 168 miles an hour, which is about the speed of a modern sailing vessel. As the wind rises, the size and speed of the waves increase. In a strong breeze their length rises to 260 feet, and their speed reaches 360 or 364 feet per second. Waves, the period of which is nine seconds, the length 400 or 425 feet, and the speed twenty-eight nautical miles per hour, are produced only in storms. During a southeast storm in the southern Atlantic Dr. Schott measured waves 690 feet long; and this was not a maximum; for in latitude 28º south and longitude 39º east he observed waves of fifteen seconds period which were 1,150 feet long, with a velocity of 78·7 feet per second, or 461/8 nautical miles an hour. Dr. Schott does not think that the maximum height of the waves is very great. Some observers have estimated it at 30 or 40 feet in a wind of the force represented by 1 1 on the Beaufort scale (the highest number on which is 12); and Dr. Schott's maximum is just 32 feet. He believes that in great tempests waves of more than 60 feet are rare, and that even those of 50 feet are exceptional. In the ordinary trade winds the height is five or six feet. The ratio of height to length is about 1: 33 in a moderate wind, 1: 18 in a strong wind, and 1: 17 in a storm; from which it follows that the inclination of the waves is respectively about 6º, 10º, and 11º. The ratio of the height of the waves to the force of the wind varies greatly.

Climate of Galveston.—The advantages of the climate of Galveston, Tex., are well set forth in a paper by Dr. I. M. Cline. The city is situated on an island four miles from the mainland, in latitude 29º 17' north, and has, therefore, a real insular climate. During twenty years the lowest temperature was below 20º only in two, while the highest recorded temperature is 98º. July is the only month in which the maximum temperature reaches 90º in every year. During August it has reached that point in eighteen years; during September, in eight years; during June, in four years; and during May, in three years. The highest monthly range is 58º, and the average diurnal range is 10º 5'. The amount of moisture in the atmosphere ranges between seventy and eighty per cent. There are on the average 133 clear, 140 partly cloudy, and 92 cloudy days in a year; and it is estimated approximately that the sun shines to some extent on 318 days in a year. The average annual death rate is about 15 per 1,000 inhabitants, consumption leading the list with one in fourteen deaths. No epidemic diseases, except a few cases of smallpox, have visited the region since 1870, and none of the more destructive epidemics have ever originated in Galveston.

Flameless Explosives.—A committee appointed in 1888 by the North of England Institute of Mechanical Engineers to investigate upon the subject of flameless explosives in relation to their degree of safety in mines, has only recently published the first part of its report upon experiments that were begun in 1892. They find that all the high explosives are less liable than blasting powder to ignite inflammable mixtures of air and fire damp. They can not, however, be relied upon as insuring absolute safety when used