Benefits of using Rain-water.

171

fact among intelligent medicalmen, that the stomach and bowels are far less liable to derangement and disease, and to attacks of epidemics under the uniform use of rainwater than of hard-water." This is confirmed by numerous medical and scientific reports in different countries.

"It has been clearly ascertained both in Paris and elsewhere, that rain-water is a prophylactic (antidote) to cholera: and that the disease was not proved an epidemic in any city where rain-water was exclusively used." Dr. Hobbs of Memphis states,-" By the exclusive use of cistern-water (i.e., rain-water), cholera will speedily disappear and not return;" and Dr. Lea, of Cincinnati, declares," That it is a verified fact, which will stand the strictest investigation, that the exclusive using of rainwater for all purposes of drinking, cooking, and bathing, instead of hard or well-water, is a sure preventive of cholera and bowel complaints; and that no town or city supplied exclusively with rain-water ever suffers seriously from epidemic cholera." The late Dr. Parkes, of Netley, also gives valuable testimony in favor of the use of rainwater in preference to spring or well water. He says,"The greatest benefits have resulted in many cases (especially in the West Indian Islands) from the use of rain, instead of spring or well water, which is often largely impregnated with earthy salts." Of course, these opinions hold good only in regard to rain-water as received from the clouds and so collected and stored as to prevent its being contaminated by organic and other impurities.

Davis mentions as a curious fact in reference to the West Indies, that "ships' crews, when ordered to Tortola, were 'invariably seized with fluxes,' which were caused by the water. But the inhabitants, who used tank,

172

Use of Rain-water in Calcutta.

i.e., rain water, were free, and so well was this known that, when any resident at Tortola was invited to dinner on board a man-of-war, it was no unusual thing for him to carry his drinking-water with him."

Not many years ago before the present filtered water supply was provided for the city of Calcutta, nearly all the old residents used to store the rain-water collected from the flat terraced roofs of their houses in large earthen jars, or jallahs, the care of which was one of the principal duties of the now-extinct, but formerly important domestic official, the abdar or waterman; and nearly every house had a special abdarkhana or waterhouse set apart for the keeping of the drinking-water jars. There were indeed several old European Calcutta residents alive up to a very recent date, if they are not so still, who, having for many years been accustomed to drink nothing but rain-water, continued to do so even after the introduction of the filtered public supply; and an advertisement of about seventy years ago shows, that the aerated soda-water manufacturers of that day held out as an inducement to consumers that their sodawater was prepared from rain-water only.

Many large cities in the south of Europe are entirely supplied with rain-water, such as Constantinople, Venice, Cadiz, and other places. In the latter city the roofs have a self-acting tilt-trough, which throws off the first rainfall with the impurities washed from the roof, before allowing the water to run into the reservoir. The Spaniards, who have a proverb for every thing and every occasion, say of rain-water, that it neither makes men sick, nor indebted, nor women widows: "Agua que no enferma, no adeuda, no enviuda."

Objects of Tree-Planting in Towns.

173

CHAPTER XV.

"No tree in all the grove but has its charms."-Cowper.

"States, societies, and individuals have encouraged by bounties the planting of trees with sufficient success, at least to excite thought and stimulate effort upon the subject of practical arboriculture."American State Reports.

There are several objects to be attained by a systematic planting of trees on the road sides, the public squares, and on waste and unoccupied lands, recently reclaimed ground, and old and unused burial-grounds.

First, we have in view the beautifying of the town, the provision of grateful shade, and the diffusion of sweet scents. Secondly, the purification of the atmosphere by the absorption by plant-life of carbonic acid and ammonia, and the diffusion of oxygen and ozone. Thirdly, the drying of the subsoil, and the withdrawing from it, by the same powerful agency, of the elements of decomposition. Fourthly, the preservation of the road surfaces. Fifthly, the equalization of the rainfall. Sixthly, the interception of malarious air currents by belts of trees; and seventhly, the production of valuable and useful timber and refreshing or nourishing fruits.

The first of these objects must be patent to every one. What can be more dreary and depressing than a town destitute of trees and vegetation, and what visitor to

174

Transpiration of Plants.

Calcutta in the months of March, April, and May has not been struck with the wondrous blaze of color exhibited by the simul or cotton tree, and the Poinciana regias glowing above the soft refreshing verdure of the numberless foliage trees with which the town and its surroundings abounds. What traveller has not blessed the grateful shade of the umbrageous banyan, the bokal or the tamarind; and what manner of man is he who has not scented up with delight the cool evening air laden with the delicate perfume of the magnolia, the har singha (Nyctanthes arbortristis) and the jasmine, or the more potent honey-like fragrance of the champa and the kuddum.

Of the second object sufficient explanation has been given in the chapter on Rank Vegetation. Of the third, the explanation is easy. Plants transpire freely when they have a moist soil to draw water from, and a dry atmosphere around them. For example, it has been calculated that a beegah of grass will part with moisture to the atmosphere at the rate of 4,266 pints per day. A single sun-flower plant transpires about one pint of water daily, nearly all this water being drunk up from the soil by the roots, the speed of the circulation being nearly twenty-four inches per hour. Experiments recently made show, that "plants in a saturated atmosphere transpire most when exposed to the sun, and that in the shade transpiration ceases when the atmosphere is loaded with watery vapour." Trees also affect the drainage of the soil by mechanical action, the roots permeate the subsoil and open up numberless drainage channels through otherwise impervious strata. In fact, they perform the office of draining in a manner analo

Effects of Disforesting.

175

gous to that artificially practised in parts of Holland and the British Islands. This method consists in driving down deeply into the soil several hundred stakes to the acre; the water filters down along the stakes, and in some cases as favorable results are said to have been obtained by this means as by horizontal drains (d'Hericourt, Annales Forestieres, 1857). It will be found that the earth is always much dryer near the roots of trees. than elsewhere; and it is an established fact that cutting down woods and forests has, in many known instances, converted considerable tracts of well-drained land into swamps and marshes.

The preservation of the road surfaces is effected by shielding them from the baking torrid heat of the summer sun and retarding evaporation from their surfaces. The equalization of rainfall is, undoubtedly, affected by the planting or denuding of a district of trees. On this head all good authorities are at one. Humbolt, Herschell, Bousingault, and others are agreed that the destruction of forests is followed by diminished and less equable rainfall; and it is known that in forest regions the ground covered with trees receives more water than the uncovered ground of regions with little or no wood. The rainfall is also greater over forests when the trees are in full foliage. The late Pasha Mehemet Alli made extensive plantations in Lower Egypt with a view to increase the rainfall. Previous to this there was hardly any rain, often none for more than a twelve-month; now that the forests have grown up, the annual average is said to be thirty days rain in the year. On the contrary, it is asserted, that, in Upper Egypt, the rains, which a century ago were abundant, have ceased since the Arabs cut down