Page:Popular Science Monthly Volume 21.djvu/388

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between the water-columns R and Z. The water in R becomes heated by contact with the imprisoned steam, and will obviously attain a higher temperature in the lower than in the upper part of the geyser-tube R. Superheated water is produced in R as well as in Z, because the weight of the water in R and the upward pressure of the water, and the confined steam in Z, produce pressure and counter-pressure. As steam and water continue to rise from the channels V, the level of the water in x y is depressed, for the steam can exercise its force only in the direction of R. As the expansive force of the steam increases, a greater quantity of water is driven over the rim of the basin till the force of the steam becomes so great as to exceed the weight of the column of water in R. Single puffs of steam escape, the elastic force of the vapor is slightly diminished, and a sudden development of steam is produced from the superheated water in Z, causing the whole column of water in R to be thrown forcibly into the air. The super-heated water which has got into R during this movement is likewise converted into steam, increasing the effect. The conditions required by the last theory for the origin of an intermittent spring exist in nature. Volcanic forces produce suitable crevices, and the water, leaving siliceous deposits upon the walls, makes these clefts steam-tight.

The time which elapses between two successive eruptions varies in different intermittent springs. It depends upon the length and breadth of the whole geyser-shaft, and the distance to which it penetrates toward the interior of the earth. The temperature of the superheated water and the amount of steam that is formed from it are also largely dependent on the size of the spring. Thus, Strokr and the Little Geyser, intermittent springs in Iceland, also lying at the foot of Bjärnafell, have much stronger eruptions than the Great Geyser. The intermittent springs of the North Island of New Zealand are distinguished by their beautiful snow-white deposits of siliceous sinter, within which the water of the basin appears blue. The most imposing of known geysers are those of North America, of which the Giant shoots its jet to the height of two hundred and fifty feet.



IN her clever article upon "Science and the Woman Question," in "The Popular Science Monthly" of March, 1882, Miss Hardaker arrives at the definite conclusion that woman is and must necessarily for ever remain the intellectual inferior of man. In view of the importance of this conclusion, it will perhaps be worth while for a critic committed to neither side of the question to point out several flaws in