The Philosophy of the Weather. And a Guide to Its Changes

by T. B. Butler

The observations for April disclose another singular and instructive condition. The temperature, that had every where been above the mean in March, fell below it in April under the concentrated trade. And snow fell on three days in some localities, and four in others.

Along the Ohio River, it fell to the depth of 8 to 10 inches on the 17th, and east of the mountains to a greater depth on the 18th, one day later. It fell to the depth of 4 inches at Marietta on the 29th also. Dr. Hilldreth, American Journal of Science for March, 1855, says:—

“It is a singular fact that the deepest snow, 8 inches, fell on the 17th of April, and at the head waters about Pittsburg over a foot. Also, on the 29th of the month, at Marietta, 4 inches, a very rare occurrence.” This depression of the temperature was quite general, but the fall of snow was local. The latter was north of a line drawn from Fort Laramie, at the base of the Rocky Mountains, in an E. S. E. direction—north of Forts Kearney and Leavenworth, and of St. Louis, but south of Newport barracks in Kentucky, and from thence to the Atlantic. Snow fell at every station north of this line, at no station south of it. The depression of temperature, however, was experienced over the continent, east of the Rocky Mountains, under, and south of, the belt of precipitation. Now what occasioned this general depression of temperature, and local fall of snow? It will not do to say, as perhaps some calorific theorist may be inclined to say, because the concentrated trade had been carried up where it was cold, a month too soon; or that the sun had heated the land in advance of it, and drawn it up.

For, 1st, it might be asked how, if it was warm enough to draw it up, could it be cold enough to make it snow; or, 2d, how happened it to start, when, as we have seen, it was warmer than the mean under it, and colder than the mean to the north and west of it, when it commenced its journey?

But again, it snowed at posts north of the line, while the thermometer remained above the mean; and the thermometer fell below the mean down to Fort Brown in south-western Texas, and at Key West in the southern part of Florida; and what is more remarkable still, at Key West, Fort Barrancas, and every other south-eastern station, except Forts Brooke and Moultrie, it not only fell below the mean of the month, but below the actual temperature of March. (See [Table I].) At Forts Brooke and Moultrie it did not rise above that temperature. West of the Rocky Mountains the depression was not felt; nor at stations north, or north-west of the belt of precipitation.

It is obvious, the calorific theory can furnish no rational explanation of this matter; for the reason that, whatever the cause, it operated not only under, but south, and far south of the belt of precipitation. It could not have been spots upon the sun, or other general cause, for then it would have operated in New Mexico and California, and at the north-western stations. It operated most intensely in Florida and the South-Eastern States, which approach most nearly the volcanic areas of South America and the West Indies. I believe it to have been occasioned by volcanic action affecting the local magnetism of our intense area; but it is a most important development, and should be thoroughly investigated. We may find in it the key to the mysterious, but unquestionable, influence of volcanic upon magnetic action; and I hope the distinguished surgeon-general will cause the records of that month to be published “in extenso.”

In May and June, the trade became more concentrated, a perfectly developed belt from the Rio Grande to the Lakes and British possessions, and doubtless to the Atlantic, with every where a central focus of excessive precipitation, gathering to itself in one vast wave the current that should have been spread out over the whole country; and leaving every where on its eastern and southern borders, down to the northern edge of the inter-tropical belt of rains—(which extended up to lines drawn from Baton Rouge to Charleston)—a perfectly well developed and defined drought. That drought will long be remembered. The following cuts show, approximately, the location of the belt of precipitation and drought for those months, and the table which follows will show their correctness.

The tables also show that this wave was occasionally a double, or divided one—evinced by an intervening partial precipitation. Tables IV., V., and VI., also show the commencement of the drought at the several stations, as the wave moved to the west and north.

MAY.