Fig. 56.
Later on, a well, similar to the one previously destroyed, was met with. The brickwork was remarkably good and about 3 feet thick, and the mortar was excellent. One charge of 4 lb. of gun-cotton broke it up into large pieces; but it took another similar charge, and two charges of 20 lb. of gunpowder to destroy it completely. On the same day, two trees were removed with ghurrah charges, which had been used throughout, for small charges, with unvarying success.
At a place called Farrashdangah, there was a very bad obstruction in the river, caused by the remains of an old bathing ghat and bridge having been cut out from the bank by the water getting underneath the masonry. Both were projecting about 3 feet above the water, and in the rainy season they formed the centre of a very nasty and dangerous whirlpool, in which many boats had, according to the Executive Engineer of the Nuddea Rivers Division, been lost. There was an immense mass of masonry, but no means of getting a charge placed underneath it; so a charge of 100 lb. of powder was placed close alongside it in about 15 feet of water. This shunted the mass bodily over and underneath the water. Two 50-lb. charges were next placed underneath the mass, and these shattered it all up, except one piece, which was got rid of with a fourth charge of 20 lb. placed well underneath it. The Executive Engineer wishing that the wing-wall of the bridge, which was on dry land during the dry season, might be removed as well, a small hole was made at the foot of the visible portion of the brickwork, and a charge of 2 lb. of gun-cotton was introduced into this, and fired with only a tolerable effect, the brickwork being cracked for a distance of 3 or 4 feet from the centre of the charge. A hole was next dug down about 5 feet at one side of the wing-wall, and a charge of 4 lb. of gun-cotton well tamped was fired. The tamping was blown out, and the wall foundations cracked a good deal. The excavation was now deepened to 6 feet, and a hole made under the brickwork big enough to contain a 100-lb. charge. It was then well tamped up and fired. Its effect was excellent. All the brickwork of the wing-wall was got rid of, and a crater about 30 feet in width at the top blown out in the point of the bank that was required to be removed, and which was one of the chief causes of the whirlpool, so that the next rise of the river was sure to carry it all away. The following day an old pucka ghat opposite to Berhampore was entirely broken up with three 20-lb. charges, and an enormous quantity of old bricks were thrown into the river.
The last operation undertaken consisted in the blowing up of a very large ghat opposite to the Nawáb of Moorshedabád’s palaces. The river during successive rains had cut into and underneath the steps of the ghat, bringing down large masses of it into the river, where they formed most dangerous obstacles to navigation. The work was necessarily carried out in a very rough way, for want of the proper tools. Deep excavations were made under the three largest masses of masonry, at about 25 feet apart, and into these were introduced three 50-lb. and one 20-lb. charges of powder. These charges were well tamped, connected up in divided circuit, and fired simultaneously. All the masonry was broken up completely, so as to be easily removable afterwards by coolie labour, which was all that was required.
The conclusions to be drawn from the foregoing notes are, that large trees lying in shallow water require charges of 50 lb. of gunpowder and upwards for their effectual removal; but that where there is plenty of water, and the trees are not very large, 20 lb. is sufficient.
For these small charges, it has been seen that the common earthenware ghurrah answers admirably, and under similar circumstances it would undoubtedly be advantageous to use them, as they are inexpensive, and obtainable in nearly every Indian village.
The charges used might, in many cases, at first have been no doubt made smaller with advantage, both for safety and economy; but as speed was the great object, these were not so much thought of.
For the removal of masonry under water, it is not necessary to place the charge underneath the mass, which is often impossible; a large charge alongside it being generally quite sufficient to break it up pretty effectually where there is sufficient head of water. Smaller charges can of course be easily used afterwards, whenever required, and for these small charges, gun-cotton is very effective, as it can be easily introduced, in the end of a bamboo, into holes and crevices where it would be impossible to get any but the smallest charges of gunpowder.