Page:Popular Science Monthly Volume 44.djvu/110

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102
THE POPULAR SCIENCE MONTHLY.

without hardly knowing what is the matter with them, who would be all the better for trying whether their discomforts spring from too high and rich a diet or from the inability to procure any but inferior meat, or fish. In the first case they would soon feel their tired digestions rested and their irritated nerves calming down, while in the latter they would find out that it is easy to get a healthier and an equally satisfying meal for half the cost of what they were in the habit of spending before.

Though these motives are not perhaps the highest which ought to lead us to a result, they are those which exercise a most general influence. The small number who change their mode of life from principle only know how far above bodily health the blessings are which grow out of the sacrifice. Before the eyes of everybody the lines of the Latin poet must conjure up a delightful and attractive picture:

“Forbear, O mortals, to taint your bodies with forbidden food;
Corn have we; the boughs bend under a load of fruit;
Our vines abound in swelling grapes; our fields with wholesome herbs,
Whereof those of a cruder kind may be softened and mellowed by fire.
Nor is milk denied us, nor honey smelling of the fragrant thyme;
Earth is lavish of her riches, and teems with kindly stores.
Providing without slaughter or bloodshed for all manner of delights.”


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ORIGIN OF THE MISSISSIPPI VALLEY RAINFALL.

By J. HARRIS PATTON, Ph. D.

IT has been assumed that the evaporation off the Gulf of Mexico furnishes the most part of the rainfall of the great valley. Says an authority, when speaking of that of the whole country, "By far the greater portion comes from the gulf and spreads over the central and eastern part of the Mississippi Valley, and even much of the Atlantic slope." Let us examine the data on which this statement is based. The area of the Mississippi Valley is estimated at 1,244,000 square miles, and the annual average rainfall on its surface is forty-two inches — that is, if the rain water did not penetrate the earth, run off", or evaporate, at the end of the year the depth would be three feet and a half.

The area of the Gulf of Mexico is estimated to be one fourth that of the valley. It is easily shown by mathematical calculation that it would require an annual evaporation off this area of fourteen feet to furnish the required rainfall, even if all the water thus raised into the atmosphere were utilized. Again, the area of the gulf is swept by the extreme right flank of the trade winds. These winds must carry toward the west a large portion of the