| Lat. | Jan. | Feb. | Mar. | Apr. | May. | June. | July. | Aug. | Sept. | Oct. | Nov. | Dec. | Year. | |
| San Diego, Cal. | 32° 41′ | 0.3 | 1.7 | 1.1 | 0.9 | 0.5 | 0.0 | 0.0 | 0.2 | 0.0 | 0.1 | 1.5 | 3.4 | 9.6 |
| San Francisco. | 37° 48′ | 1.7 | 0.5 | 4.4 | 2.1 | 0.4 | 0.0 | 0.0 | 0.0 | 0.4 | 0.6 | 3.0 | 5.5 | 18.8 |
| Cant., Far W., Cal. | 39° 02′ | 3.3 | 0.6 | 6.4 | 2.2 | 0.9 | 0.0 | 0.0 | 0.0 | 0.3 | 0.1 | 3.5 | 4.6 | 21.9 |
| Astoria, Oregon. | 46° 11′ | 27.0 | 10.9 | 6.1 | 4.4 | 5.9 | 2.6 | 0.0 | 2.3 | 1.9 | 6.7 | 13.2 | 6.2 | 87.2 |
| Puget’s S’d, Ore. | 47° 07′ | 11.8 | 3.9 | 4.7 | 4.1 | 0.8 | 0.6 | 0.5 | 1.3 | 1.6 | 3.6 | 5.9 | 6.1 | 44.8 |
| Sitka, Russ. Am. | 57° 3′ | 2.5 | 9.6 | 3.5 | 3.3 | 1.9 | 5.9 | 3.7 | 10.1 | 14.8 | 12.7 | 7.4 | 4.2 | 79.5 |
The figures are for inches and tenths of an inch of rain.
Thus, it will be seen that in January, when the southern line is at San Diego, at the south line of California, the focus of precipitation is over Oregon; and that in August and September when the southern line is carried up and over Oregon, the focus has traveled north to Sitka, and that it is always at least 10° north of the southern line of the belt upon that coast. The increased quantities of rain which fall at the focus of precipitation there, from Oregon up, are doubtless much enhanced by the equatorial oceanic current which flows over opposite that part of the continent. A like effect, precisely, is produced in Europe. The quantity of rain which falls at Bergen, in Norway, being 8761⁄100 inches per year, more than three times the average for that continent.
The difference shown in the foregoing table, between Astoria and Puget’s Sound, is owing to the fact that the latter lies in the interior and within the coast range of mountains, while Astoria is situated at the mouth of the Columbia River, with an open view of the ocean.
A like comparative increase of precipitation in northern latitudes, in summer, is found every where varying according to the local influences which operate in the particular case. Thus,
| There falls in | Winter. | Spring. | Summer. | Aut’mn. | Year. |
| Burlington, Vt., lat. 44° 20′ | 5.7 | 7.3 | 11.4 | 9.8 | 33.9 |
| Albany, N. Y., lat. 42° 39′ | 8.3 | 9.8 | 12.3 | 10.3 | 40.7 |
| Minnesota, Iowa, lat. 41° 28′ | 7.3 | 12.3 | 17.4 | 11.7 | 48.8 |
| St. Peters’g, Russ., lat. 59° 56′ | 3.89 | 3.20 | 5.70 | 4.71 | 17.51 |
| Pekin, China, lat. 40° | .54 | 3.35 | 18.80 | 2.29 | 25.68 |
Pekin lies in the northern part of China, and would have a much larger fall of rain from a concentrated counter-trade, but for the numerous mountain-ranges which intersect its path in winter, but over which it passes at a greater elevation during the summer—a peculiarity from which the eastern section of this country is most remarkably and happily free.
Thus, it is obvious that the focus of precipitation in the zone of extra tropical rains, is some 8° to 12° north of its southern line, and travels with the whole machinery in its annual transit north and south.
It is a question of some difficulty, perhaps, whether this focus is increased by the increase of magnetic action at this point, for both the line of descent of the counter-trade, and the focus of magnetic action, are carried up in a like manner, and for a like cause, and, in all probability, both concur in the result.
There is exceeding wisdom in this provision for the gradual subsidence of the counter-trade, and gradual increase of magnetic intensity, and consequent gradual precipitation. On the European continent, and over western Asia, there are 50° of latitude to be supplied with moisture by this polar belt of rains. If the focus of precipitation was at its southern border, the counter-trade would be deprived of its moisture at that point, and little would reach the more northern portions of the globe which are to be supplied by it. But the movement of the whole machinery carries up the southern line from the south boundaries of the Barbary States on to the Mediterranean and portions of southern Europe, and the focus of precipitation and of near approach of the counter-trade to the earth, being situated far north of the southern line, is carried up correspondingly, while the combination of the moisture with the atmosphere by south polar magnetism and electricity, and the gradual descent of the counter-trade, enable it to resist, to some extent, the influence of north polar magnetism and cold, and thus retain portions of its moisture for distribution in the polar regions.