Page:Popular Science Monthly Volume 8.djvu/783

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volves use of nerves. The external force, if exerted by a muscle, is only part of that which it produces. Now, the proportion between these two in their several degrees is a subject of great practical importance, and some interesting facts have recently been published by Helmholtz. From these it is clear that the greater the external force exerted the greater is the proportion of the needful internal force—that is, great exertion is more wasteful than moderate exertion. Then force has to be evolved in proportion to the external work done, and therefore the greater is the wear and tear of the animal machine. The same increased proportion of non-productive work is seen when the external energy is below a moderate amount. It is found, for instance, that in walking, a speed of three miles an hour gives the most economical use of the forces. No doubt in these facts we have an index to much of the ill effects of the present high-pressure rate of work and life. The waste of force is out of proportion to the work done. More is effected in a given time, but the body feels it more, and its working period is proportionately shorter. These facts cannot be too often repeated or too constantly remembered by those who have the regulation of labor.—Lancet.

Contributions to Meteorology.—The American Journal of Science, for January, contains the fourth paper by Prof. Loomis, giving results of recent researches in the science of meteorology, founded on data derived chiefly from the weather-maps of the United States Signal Service.

In a former article attention was called to the fact that low temperatures at the surface of the earth are produced by descent of cold air from the upper regions of the atmosphere. It was shown that, in areas of high barometer, the movement of the air is outward from the centre, instead of inward, as in case of low barometer or storm. This implies a supply from downward motion.

The current notion, that extreme cold is brought by wind from colder areas, is met by the fact that, at Yakootsk, in Siberia, which is about the coldest place in the Northern Hemisphere, the temperature is lowest when the air is quite still, and equally when the wind is from north, south, east, or west. These results are obtained from four years' observations at that place, and are similar to those obtained at New Haven, except as to direction of wind. It would be difficult to explain where the extreme cold of Yakootsk came from, except from the upper atmosphere, seeing that it is colder than the country round about.

A diurnal variation in the progress of storms was noticed by Prof. Loomis in a former paper. This fact suggested to him the further one that there is a diurnal inequality in the rainfall. This is now shown by observations made at Philadelphia, not by the Signal Service maps, which do not record hourly observations. It appears that the maximum rainfall occurs at about six o'clock in the afternoon; and the minimum at three o'clock in the morning.

By observations which cover a period of ten years, made at Prague, in Bohemia, it appears that the greatest rainfall during the day occurs in the afternoon, the maximum being from three until six o'clock.

The tracks of storms in America and Europe, already noticed by Prof. Loomis, are further considered in this paper. He determined the precise latitude at which the storm-centres cross certain lines of longitude, and in this way establishes a line which is the track of the storm-centre; a similar method was applied to storms in Europe. It appears that the average track is not regular, but varies. In an article published in July, 1874, it was stated that the average direction of the storms of the United States was, for the year, 8° north of east, and that is correct as a general statement. Connected with the present article is a chart, by which it is seen that the average track of American storm-centres is over Chicago and Detroit, and is deflected to the south coast of Newfoundland. From this point it seems to be continuous over the ocean, being deflected northward near the Irish coast, passes over Dublin, and thence across Denmark. These results, however, are obtained from the Paris maps, and the continuity of the line may, in some measure, depend on the extent of the field of observations by which it was determined.

The number of storms traced across the Atlantic Ocean is not large; they undergo changes on the ocean, and frequently are merged in other storms.