Page:Popular Science Monthly Volume 32.djvu/445

Rh on the subject, with the present methods of teaching the science, and of the desire for important changes.

Mr. has projected a new theory of the origin of mountains, which contradicts all the other theories. Having shown that periods of great sedimentary deposit precede the birth of every large mountain-chain, he supposes, as Babbage has proved, that a great elevation of temperature ensues, producing expansions of the strata. These being prevented from spreading horizontally by the rigid mass of the earth's crust that bounds the local area, can only swell upward and cause those ridges which we know as mountains. The author has tried experiments in the mechanical effects of expansion by heat on various rocks, and has found a similar result in miniature produced upon them.

are made in Jersey for the use of the Channel Islands farmers which will fold up when empty, and thus, having been sent to market, can be packed into a small space on the return. The staves are fixed upon the hoops so that, the heads being removed, they may be rolled up. They are made perfect cylinders, and therefore occupy less space for the same capacity than ordinary barrels.

spoke at a school festival, some time ago, of the importance of "learning how to learn," and showed that knowledge not immediately useful in itself may be the means of developing the power of learning in the mind acquiring it. The cultivation of the faculty of knowing is of incomparably greater importance than the mere acquisition of knowledge; and to the student this faculty, so developed that when need arises, knowledge may be quickly obtained, is a better provision for the business of life than is afforded by the largest and richest stores of information packed away in the memory; thus the brain-property most worth carrying about is the power of finding at pleasure and learning at will precisely what is wanted.

has had a great development in France. Thus, while in 1857 there were in the Bay of Arcachon twenty parks, or district oyster-beds, in 1865 there were 297 beds, producing 10,000,000 oysters annually; and there are now 15,000 acres of beds, yielding an annual supply of 300, • 000,000 oysters. From Auray, on the coast of Brittany, 7,000,000 oysters were sent to market in 1876-'77; in 1885, the numbers exceeded 70,000,000. On the other hand, the British oyster-industry has declined; and the coast which furnished ancient Rome with oysters, and within a generation exported then to Paris, now ranks low in the list of oyster-nurseries.

recent International Hygienic Congress at Vienna was attended by twenty-two hundred and fifty members. M. Brouardel spoke upon typhoid fever, which he said was a far more dangerous disease to man than cholera. Concerning its origin—whether from the decomposition of organic matter or from specific virus—there was still an open question. Herr Pettenkofer, in a lecture on hygienic instruction in universities and technical schools, dwelt on the necessity of spreading hygienic principles among all classes of society. lie referred to the statistics of mortality of London as showing bow hygienic piety there had been rewarded.

climate of the Sandwich Islands is peculiarly adapted to the cultivation of rice of a superior quality and in great quantity, its evenness of temperature permitting the raising of two crops a year without any particular strain upon the soil. The crops are raised in fields called patches, most of which were formerly used by the natives for raising taro, and which are often not more than an acre in extent. The fields are situated in the lowlands, where abundant irrigation can be obtained, and sometimes on slight elevations where artesian wells can be successfully established, and are the highest priced lands in the kingdom. The cultivation is almost entirely in the hands of the Chinese.

a London photographer claims to have perfected a system of photography in colors. He takes a negative on a specially sensitized plate; from this a positive is produced on a chemically treated basis by the aid of a solar camera and a spectroscopic arrangement. The image is produced in colors on the basis without the aid of hand-work or brush. The colors are said to be all hydrocarbons, specially prepared and capable of subdivision to the 180-millionth of an inch. When the colored picture is produced by chemical action, the image exists between two films not more than the hundredth part of an inch in thickness. These photographs are said to be permanent and not affected by climate.

has observed that the workmen in the petroleum-mines of the Carpathians, having to breathe an air contaminated with various hydrocarbons, carbonic acid and oxide, and sulphureted hydrogen, are not rarely subject to asphyxia. They are also exposed to tingling in the ears, dazzling, beating of the arteries of the head, syneopessyncopes [sic], and hallucinations of usually an agreeable character. The respiration of petroleum vapors induces at first feelings of lightness in the breast and greater freedom in breathing, but in the end palpitations and general weakness. The rareness of consumption and infectious and epidemic diseases among the workmen is remarked upon.