Page:Physical Geography of the Sea and its Meteorology.djvu/201

Rh 95° 39' west. Neither of these poles is a point susceptible of definite and exact position. The polar calms are no more a point than the equatorial calms are a line; and, considering that these poles are areas or discs, not points, it is a little curious that philosophers in different parts of the world, using different data, and following up investigation each through a separate and independent system of research, and each aiming at the solution of different problems, should nevertheless agree in assigning very nearly the same position to them all. Are these three poles grouped together by chance or by some physical cause? By the latter, undoubtedly. Here, then, we have another of those gossamer-like clews, that sometimes seem almost palpable enough for the mind, in its happiest mood, to lay hold of, and follow up to the very portals of knowledge, where we pause and linger, fondly hoping that the chambers of hidden things may be thrown open, and that we may be permitted to behold and contemplate the mysteries of the winds, the frost, and the trembling needle. In the polar calms there is (§ 215) an ascent of air; if an ascent, a diminution of pressure and an expansion; and if expansion, a decrease of temperature. Therefore we have palpably enough a connecting link here between the polar calms and the polar place of maximum cold. Thus we establish a relation between the pole of the winds and the pole of cold, with evident indications that there is also a physical connection between these and the magnetic pole. Here the out-croppings of a relation between magnetism and the circulation of the atmosphere again appear.

362. The barometer in the wind bands.—Thousands of observations, made by mariners and recorded in their abstract logs, have enabled us to determine approximately the mean height of the barometer for the various bands (§ 352) at sea. Between the parallels of 36° S. and 50° N., Lieut. Andrau, of the Dutch Navy, has collected from the abstract logs at the Meteorological Institute of Utrecht no less than 83,334 observations on the height of the barometer in the following bands. (See table, page 176.)

363. More atmosphere in the northern than in the southern hemisphere.—The diagram of the winds (Plate I.) has been constructed so as to show by its shaded border this unequal distribution of the atmosphere between the two hemispheres. Have we not here proof that the southern hemisphere (§ 261) is indeed the boiler to this mighty atmospherical engine? The aqueous vapour rising from its waste of waters drives the air