Page:Popular Science Monthly Volume 40.djvu/834

812 exemplified at the winter seaside resorts on the south coast of England, where certain spots enjoying conditions of shelter from cold winds, combined with exposures favoring the concentration of the sun's rays and the warm winds upon them, enjoy a springlike mildness through much of the winter. Prof. W. Mattieu Williams speaks of Torbay, Torquay, Broadstairs, and Hastings as possessing these characteristics. A considerable difference has been noticed in the winter temperatures of places east and west of a certain point on the coast, though all are nearly in the same latitude.

Dr. D. Hart Merriam has described a succession of temperature zones in descending from the plateau level to the bottom of the Colorado Cañon equivalent to those stretching from the coniferous forests of northern Canada to the cactus plains of Mexico, with marked variations of climatic conditions under apparently very slight diversities of exposure.

A variation of only 5·3° Fahr. in the mean annual temperature at Uskfield, England, is shown by Mr. C. Leeson Prince to be sufficient to exert an enormous influence on the general character of the seasons, the produce of the soil, and the health of the population.

The fact of changes in climate being admitted, discussion turns upon their extent, and the laws by which they are governed. In many cases they are brought about by changes in local conditions, of which the removal or replacement of forests, or the relations of land and water, are among the most important. In other cases a periodical law is supposed. The attempt has been made by some meteorologists and astronomers to show that there is a connection between such changes and an eleven-year period of abundance and scarcity of sun-spots. It was believed by an observer in Ceylon in 1872 that that island was on the eve of an important change of climate depending upon a cycle of thirty or thirty-five years. The previous thirty years, he asserted, had shown a complete contrast to the thirty years preceding them, with manifestly different effects on animal and vegetable life. It had been a period of relatively lighter rainfall, and the next cycle of thirty years was expected to be, above the average, wet. This theory of changes by thirty or thirty-six years is often met in following the discussions on this subject. A paper published recently in the Archives des Sciences Physiques et Naturelles deduced from a total of twenty thousand years of observations, at about five hundred stations, that the climates of all the continents, excepting only a few maritime coast regions, were subject to simultaneous