Page:Popular Science Monthly Volume 16.djvu/209

  2. Supposing the data obtainable, the organization essential to dealing with it in such detail would be immense: a lifetime would hardly suffice to reach a practical result, 3. Its publication would require five times as many volumes as the present system—a series already bulky enough to deter any one from increasing it. 4. Throughout by far the greater part of the ocean, the several quantities do not vary rapidly enough to warrant compiling them for such small areas.

The prevailing direction and force of the wind are substantially the same in many adjoining 1° squares; and so also are the pressure and temperature of the air, the weather, etc.: therefore, to classify them for 1° squares would only be multiplying what, for the most part, was equally applicable to the whole extent of a 5° square.

Besides, the object sought by the 1° system, the determination of the well-defined limits of the different phenomena, is more accurately attained by a method pursued in connection with the 5° system: on a Mercator's projection of very large scale, all the observations relating to one subject of inquiry are plotted in the position where they were observed. For example, the winds: at each noon position of the ship, an arrow is drawn to indicate its direction, and a small figure placed beside it to denote the force; a circle represents calms, and several short lines radiating from a point, light variable airs.

This continued until the whole sheet is studded with symbols, it is evident that we can determine, not to the closeness of one degree only, but to within a few miles, the precise area covered by the trades, or calms, or monsoons, or irregular breezes. The observations of the temperature of the air, of the sea-water, and of the barometer, are all similarly plotted, each on a sheet by itself. In every instance the symbols are in different colors, to distinguish the data peculiar to each month.

In order to determine with the greatest possible precision the limits of the Gulf Stream, as well as the veins of varied temperature that permeate it, a separate sheet for each month on an unusually large scale is provided for the observations relating to it.

It might seem that, instead of publishing such elaborate charts as the series described, a single sheet containing merely the conclusions arrived at would suffice—a chart showing those courses from port to port on which the most favorable winds and weather would be found. As well lay railway-tracks over the ocean and expect ships to glide upon them! In matters pertaining to their profession, none are more tenacious of their opinions than sailors—and justly so: they form them after hard experience. To dislodge those opinions it must be proved wherein they are faulty and others correct; and this can not be done by mere results. To lay down a rigid rule for a man to follow is to deprive him of the exercise of discretion and