Sometimes, instead of a series of separate wells, the whole mass of a pier has been built in a block, with hollows at intervals, and sunk together by several parties of well-sinkers. In this way the piers of the great Solani Aqueduct, at Roorkee, were constructed and sunk 20 feet; but this work requires very experienced men, and is subject to such risks that, as a rule, separate wells are preferred.
Such work as the above can only be carried on when the river is low, and the current very slack, and this may be a good place to speak of the general nature of such Indian Rivers. I refer chiefly to such streams as the Ganges, Jumna, Indus, and others, as there are few things of more vital interest to the Indian engineer.
They rise in the region of perpetual snow, generally from glaciers at a height of over 20,000 feet, and make their way to the plains (receiving numerous affluents on the road), as great torrents with numerous rapids, and quite unnavigable, except in particular places. On emerging into the plains, which they do very suddenly, the bed changes, first from boulders to shingle, and then to sand, and the stream cutting deep into this soft soil, becomes more and more charged with silt, especially as the lessening slope of the country checks the onward velocity. Thenceforward, the river is a sluggish stream, pursuing a tortuous course between low, flat banks, and full of shoals and quicksands, until near its mouth, where it parts into numerous channels, and forms a vast delta reaching to the sea. Owing to the vast quantity of silt brought down by these rivers, which elevates their beds and during the inundation season is freely deposited on both banks for some distance inland, it follows that these streams, in the lower portions of their course, often run on a ridge, and not at the lowest points of their valleys,—just like the Po and Mississippi, which are retained between artificial dykes.
These rivers are at their lowest in the cold season; and in December, January, and February, their navigation is attended with the greatest difficulties. From March to June, the increasing heat of the sun melts the snow in the higher ranges, and the rivers rise rapidly. In June, July, and August, the monsoon rains increase their volume to a prodigious extent. Their banks are often inundated far inland, and the yellow turbid waters carry down more silt than ever; the increased velocity of the current, acting on the light sandy soil of the sides and bed of the channel, cuts away the banks and scours out shoals in one place, and then at the next bend a temporary check will throw down enormous quantities of this silt, and the stream shoots off in a new direction altogether. I have seen the whole of the Indus concentrated in a not very deep channel 1000 feet across; six months later I have been in a boat on the same spot, and was unable to see either bank from mid-stream. In one year I have known it cut its way inland a full mile, measured perpendicular to the thread of the stream.
It is these violent changes in velocity and direction, and the soft and treacherous character of the soil, that make the question of foundations in water a peculiarly difficult one in India. The sudden shifting of a shoal may dam up the archway of a bridge, and the increased velocity in the narrowed waterway acting on such soil, often scours out a hole 30 feet deep in a single night. Almost every rainy season in India sees failures and disasters on this score, and the most carefully considered design may be a mass of ruins in twenty-four hours. The Bengal mode of dealing with these difficulties is to carry down every pier-cylinder, whether of masonry or iron, to such a depth as either to rest in the firm soil below, or to be absolutely beyond the reach of any possible scour, but to put no flooring or curtain walls by which the stream can possibly be checked and incited to tear up the bed. The Madras system is to be content with a much smaller depth of foundation, but to provide, by means of a flooring and apron walls, a compact dam of masonry solidly bound together, front and rear and from shore to shore, which shall be proof against any action of the stream. The subject is one which has excited much discussion, but is too long to enter upon here. You will find it treated of in the works already quoted.
I have now described the most important specialities of Indian foundations, and have to ask you to follow me in the first section of what I may call special engineering constructions, viz. Buildings, or rather dwellings, such as houses, [barracks], churches, and the like. The subject is, of course, a very extensive one, and I only propose here to draw attention to those buildings which the Indian engineer is generally called upon to construct. First, then, let us take Indian Barracks, that is, barracks for English soldiers in India, as they are not only the most important buildings that you will have to deal with, but there are many vexed questions concerning them which are still far from settled, and which apply equally to all dwellings erected for Europeans in an Indian climate.
In the earlier days of our Indian empire, the barracks constructed for the European soldiers were often built on ill-chosen sites; the rooms were low and a great deal too crowded, and drainage and conservancy scarcely thought of; the consequence was a frightful mortality, which often reached the high figure of 70 to 90 per thousand. As the important subject of sanitation received more and more attention in England, it was not likely it should be neglected in India, where a tropical climate aggravated the results of neglect of sanitary laws, and where every English soldier who died cost the Government a large sum of money to replace him.
At the same time that attention was thus roused, the conquest of the Punjab and the necessity of quartering a large number of troops in that province to defend the most exposed frontier of the empire, made the subject doubly important, while it gave a field on which to carry out the results of recent investigations. Large sums of money were accordingly spent on the barracks at Mean Meer, Sealkote, Nowshera, and other new stations. They were all single-storied buildings—each company of 100 men having a barrack to itself, consisting of six wards, each 48 by 24 feet, and 24 feet high, with double verandahs on both sides, besides rooms for the non-commissioned officers. The men were to sleep in the wards, and to dine in the inner verandahs. A reading-room was also supplied at the end of each barrack. Wash-houses and privies were arranged in separate buildings near the barracks.
These buildings were certainly a great improvement on anything hitherto erected, and were decidedly not open to the charge of being overcrowded. Unfortunately, however, the Punjab has a cold season as well as a hot, and in the winter months the men complained that it was almost impossible to keep themselves warm; while even in hot weather, the high winds and dust found their way through the numerous doors and windows, and the barracks were anything but comfortable residences.
Nor did they prove at all healthy, for cholera and intermittent fever played sad havoc among the troops in more than one season at Mean Meer. This was not, however, owing to any fault in the barracks, but to what was an error in the choice of site for the cantonment; and attention is drawn to it because the instance is instructive, and has more than once been repeated. Apparently under the idea that there was something in the very presence of vegetation which might engender malaria, a flat, bare, dreary-looking site was selected, totally devoid of all vegetation, and with water 40 to 50 feet below the surface; while, from the presence of a kunkur or stony stratum a few feet below the top, it has been found impossible to get a tree to grow to a respectable size. It may be taken as a rule that the presence of healthy vegetation shows a site favourable to human beings as well as to trees and crops, and that such sites as that of Mean Meer should be carefully avoided in future.