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Page:Popular Science Monthly Volume 21.djvu/579

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POPULAR MISCELLANY.

light-hearted and impulsive, because he lives in an easy country, with a soft climate and rich soil. The Highlander is rugged and stern, because his country, where "he has to fight with the elements a never-ending battle, wherein he is often the loser," is so. The apportionment of lands into cultivated, pasture, and feral lands, rests upon geological causes, which determine that each tract shall be used for the purposes by which the most can be made out of it. The sites of towns and villages may often be traced to a similar influence. Formerly they were built around heights that could be fortified; now they are built where the geological features afford the most scope for industrial and commercial development; and the latter towns are the ones that are growing, and to which the population is being transferred at the expense of the others. The style of architecture, which is largely determined by the presence or absence of building-stone, and the kind of the stone or clay, is obviously related to geological features. Lastly, "the history of the development of our system of railways, our steam machinery, our manufactures, is unintelligible except when taken together with the opening up of our resources in coal and iron," and these are traceable wholly to geological features.

 

A New Weighing of the Earth.—Professor von Jolly, of Munich, has recently employed a new process for the determination of the mean density of the earth. He placed a pair of scales in the top of a tower, and attached to each plate of the instrument a wire which reached, passing through a zinc tube, to twenty-one metres below. To the lower ends of the wires other scale plates were suspended, which thus hung within a little more than a metre of the ground. Under one of the lower plates he put a ball of lead, a metre in diameter. The fact that a body at a certain elevation gains in weight as it is brought nearer to the ground was verified by weighing bodies first in one of the upper balances and then in one of the lower ones. Furthermore these bodies varied in weight in the lower plates according as the mass of lead remained under them or was taken away. The differences in these weights showed the degree of attraction exercised by the mass. The value thus obtained, compared with the attraction exerted by the earth alone, furnished a means of ascertaining, according to the laws of gravitation, the ratio between the density of the earth and that of lead, and, the latter being known, of determining the mean density of the globe. M. von Jolly's experiments give this density as 5·692, with a probable error of ±0·068, a figure that agrees quite well with other determinations, particularly with Bailey's of 5·67.

 

Recent Applications of Science to Machinery.—Sir Frederick Bramwell took as the subject of his chairman's address at the recent opening of the 128th session of the Society of Arts, the later applications of science to the promotion of arts, manufactures, and commerce. It could not be said, he remarked, that any new scientific discovery or principle has been applied to the steam-engine, which is still our pre-eminent motor, but the principles on which its economical action depends have been advanced by the application of jacketing for saving steam and the use of higher pressures, with a consequent economy of coal. Available pressures have increased during the last half-century from three and a half pounds to one hundred pounds; and Mr. Loftus Perkins has engines running with four hundred pounds of pressure above that of the atmosphere, demanding a consumption of one and two thirds of a pound of coal per indicated horse-power per hour against two and a half pounds required by engines using a pressure of one hundred pounds. The saving, five sixths of a pound, seems small when expressed in simple figures, but it represents a considerable percentage, and the difference between running a vessel fourteen days and twenty-one days with the same stock of coal. Nevertheless, unless some wholly new and at present undreamed-of discovery is made, the steam engine will have to yield its place to other means of obtaining motive power. The average of British engines do not give forth one twenty-fifth of the energy that may be considered as residing in the fuel they consume; and even if we should obtain a horsepower per hour for as little as one pound of coal, we should still utilize only about a sixth or a fifth of that energy. The opera-