Lectures, reports, letters, and papers on sanitary questions / by Robert Rawlinson.

  • Rawlinson, Robert, 1810-1898.
Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: Lectures, reports, letters, and papers on sanitary questions / by Robert Rawlinson. 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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    repeat the condensation there until a change is brought about either through a process of exhaustion, or in consequence of the more powerful antagonistic action of some other natiiral agency. The average voliime of rainfall in England I have already stated to be about 36 inches. In some parts of India the average is as high as 300 inches; and this fall takes place during the monsoons, vrhich occupy about three months in the year. The actual full weight of the entire volume of the rain, however, falls within a single month. During the last year, in some parts of Bengal 135 inches of rain fell in twenty-four days. This was in the month of .June, on the 2l8t day of which month 16-4 inches of rain fell. In Bombay the lower parts of the town were flooded to the depth of 4 or 5 feet; so that, even if there had existed main sewers as large as railway tunnels, they would have been filled without materially lessening the surface water. Such sudden and violent excesses of rainfall, it must be observed, are not exclusively restricted to the tropics. They occur also in our own country, notwithstanding the comparative smallness of our yearly average. We have just seen how, in Bengal, on the 21st of June last, there was a rainfall of 16-4 inches. This fall occurred within the space of the twenty-four hours of a single day; but in England, during a thunderstorm, as much as 2, 3, or even 4 inches of rain have been known to fall in a single hour. In the consideration of this question of rainfall, for all practical purposes of engineering, there exists the truly terrible contingency of a sweeping destruction being brought about by a sudden storm, unless engineers extend their calculations be- yond averages to maximum excesses. And, from the neglect of such calculations, most serious mistakes have been made in modern engineering, in our own country, in Europe generally, in the East, in Africa, and in Australia. In the wet season, in Yorkshire, to which I have already referred (November, 1866), two days' and nights' rain swept down a large masonry viaduct, belonging to the Midland Kailway, which could not have been erected at a cost of much less than £20,000 or £30,000. When this viaduct was con- structed, the engineer had not contemplated, as a possible contin- gency, that the small river which flowed through a wide valley might sweU into a devastating torrent; and, consequently, when the great storm came, his foundations were under-cut, and the whole viaduct became a heap of ruins. In other parts of the world, and particularly within the tropics, engineers have to contend with floods of a much heavier and more destruc- tive character than the worst that have been known to occur here. In England, some of oui' rivers—as the Eden at Carlisle, the Ouse at York, and the Thames in its upper branches—rise, from their dry water-bed to their flood-water height, 20 feet vertical; but in South Africa the rise of rivers is not less than 60 or 70 feet. In Australia, some rivers have actually risen 120 feet; in Italy, and in Spain, roaring torrents rush furiously along where, in the previous year, there existed only dry ravines. We have all lately learned that similar