The modifications of the external aspects of organic nature produced by man's interference / by George Rolleston.

  • George Rolleston
Date:
1880
Catalogue details

Licence: Public Domain Mark

Credit: The modifications of the external aspects of organic nature produced by man's interference / by George Rolleston. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    it is that from so many quarters of the world we liave more or less well-established histories of belts or curtains of trees protecting towns from malarious and anti-sanitary influences. Secondly, though doubt may be raised {e.g. by M. J. Bellucci cit. ‘ Athena3um,’ March 14,1874, p. 300) as to the giving off by trees of ozone into the air, there can be no doubt as to another mechanical effect besides the one already dwelt upon in the way of breaking the force and the fall of raindrops, and thereby ])reventing, jiro tanto, the over-rapid flowing away of such rain and the over-violent washing away of the soil. Simple as this action is, it is, when coupled with the action of the roots and their spongioles to which it gives a fairer chance of coming into play, one of the most important which a tree in leaf exercises. Finely divided rain sinks into the soil, whilst rain which falls in larger masses runs off and forms torrents. The roots making up an interlacing fibrillar mass by their multitudinous divisions, entangle and detain the moisture which comes to them in capillary columns; and from the loaded sponge which they thus come to represent, they dole or issue out in rations the supplies necessary for keeping springs and streams in constant and perennial volume.* It is, I must say, a considerable marvel that upon a third function of that part of a tree which man can affect, either by his own hands or through the intermediation of his domestic animals with the greatest results in the way of mischief at the least cost of labom* to himself, so much room for dispute and doubt should still be left open by the botanists. Upon this third function of the leaves, their power as evaporators, the most important perhaps of all their functions, both as regards the tree’s own economy and as regards ours, it is little less than marvellous that a Professor of Botany should have to write thus in 1875. Professor Koch, however (‘Vorlesungen iiber die Uendrologie,’ 1875, p. 284), following Ebermayer, 1. c., p. 183, says : “ The question of the evaporation of water through the * It is of course possible to exaggerate the preventive power of arboriculture, as of other beneficial agencies. If a mountain is sufficiently high, and can be blown upon by sea breezes as yet undeprivecl of the full proportion of moisture which a warm latitude can give them, you will have from time to time destructive torrents rushing down their sides, however well wooded they may be. But what is an occasional occurrence only in a well wooded mountainous country, is a verj common one in a district where the charcoal burner, the wood merchant, and the goat, have been allowed to have their wasteful will unchecked. Homer’s lines, II. xi., •492-495, show that however striking the phenomenon ho describes, it was never- theless not so very common as the complaints with which so many of the Keports I have referred to prove it to be now in so many countries in Europe and elsewhere.