The author states that nowhere in the old world is the influence of man on the physical configuration better seen than in Russia, as there some of the operations long ago effected in Western Europe (such as the clearing of forests and the cultivation of the land) are of recent date, and we can examine if the change of climate caused by the destruction of forests is as great as it is stated to be. The observations on the Wolga, made at the harbours of Astracan, furnish us with some means of doing so. With this view four ten-year periods are compared, as otherwise the anomalies of single years would be too conspicuous.
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|—||High Water||Height in Eng. inches.||Days Elapsed|
|(a.) Covered with ice.||(b.) Opened.||(c) Beginning.||(d.) Highest.||(e.) End.||a-b||b-c||b-d||c-e|
|1830-37||Dec. 18||March 22||April 30||June 16||August 17||104||94||39||86||109|
|1838-47||" 14||" 23||" 28||" 18||" 31||90||99||36||86||125|
|1848-57||" 22||" 27||" 29||" 14||Sept. 12||113||95||33||79||136|
|1858-67||" 11||" 29||" 22||" 13||Oct. 31||117||108||24||76||191|
|General mean||" 16||" 25||" 26||" 15||Sept.15||106||99|
|1844, 1857.||1837.||1835.||1848, 1864.||1831.||1867.|
|Earliest||Nov. 21||Feb. 20||March 25||May 25||June 30||147||Highest.|
|Latest||Feb. 6||April 17||May 19||July 4||The water
did not fall
to 0 till
The deductions drawn from these results are as follows:—-
(1.) Though the opening of the river from ice now happens a little later than in former times, the high water begins earlier, so that the time elapsing between the opening and the beginning of high water is diminished from thirty-nine to twenty-four days, and the highest flood now arrives seventy-six days after the opening instead of eighty-six.
(2.) The period of high water is becoming longer, and the height of the water generally a little increasing. In the continental climate of Eastern and Central Russia the earth is covered with snow for four or five months in the year, and the rivers are frozen for nearly the same time. Even in Astracan, in 46° 40′ north latitude, the river is frozen for nearly 100 days, and the middle temperature of winter is 21.7° Fahr. The rivers rise in spring, when the snow is melting. From Astracan to 51° north latitude, the land is generally a steppe and unaltered, but to the north the basin of the Wolga was covered with beautiful forests. Now, with the settling and cultivation, with the enormous increase of factories, and steam navigation on the rivers, the forest has been devastated to a great degree. In wooded countries the snow lies longer in spring, as it is protected by the trees—in some cases the difference may be a month. It melts slowly, and does not cause the disastrous floods which occur in a bare country. It will be seen also that the end of the flood arrives later and later. This gives an indirect answer to the question whether the quantity of rain has diminished or not after the felling of the wood. The table leads the author to think that there has been no diminution, but it must be remarked that in a wooded country more of the rain is retained by the roots, mosses, and fallen leaves, and, in consequence, less of it is free to reach the mouth of a river. In an open country most of the water which falls during the rains of summer runs to the rivers, destroying the arable land, so that even a greater quantity of rain may profit the surrounding country very little, and the inhabitants may be in the right when complaining of drought, if the land is cleared of forests, as seems to be the case in the basin of the Wolga. The complaints of the agriculturists are general, and the observations on rainfall have not been of sufficient duration to decide the question.
The position of the Wolga basin affords indirect evidence on this point, as its rainfall is gathered into an inland sea—the Caspian—the level of which has greatly risen since 1866, and as most of its waters are poured in by the Wolga, we must infer that this river now collects more water than it did formerly.
Dr. Hector said that the paper just read, the manuscript of which had been sent to him by the learned author, related so a subject of peculiar interest to New Zealand meteorologists, as the effect on the climate produced by the clearing of forests can be observed in this country without the complications due to distant influences which affect continental climates.
Mr. Hood thought that ten years was too short a time to judge of the effect. The climate of Egypt, Canada, and Scotland had been altered by the clearing of forests, and he considered that trees should be extensively planted.
Mr. Blackett remarked that there was no doubt that the clearing of the forests in the province of Nelson had made the floods there much more serious than formerly.
The President said that of late years the destruction of forest had been so great in France that the Government had been spending large sums of money in replanting. Floods in the Hutt River had much increased since clearings had been made, and they would probably still further increase unless steps were taken to preserve the forests. The same thing had also occurred in the province of Canterbury.
Mr. J. A. Wilson remarked that Dr. Wojeikof's paper applied more to trees preventing the melting and blowing away of snow, and the case was, therefore, not quite similar to that of New Zealand. He thought that it would be very desirable to obtain observations of the snowfall on the globe as distinguished from the rainfall.