History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c32.s2.t3.10

v1.c32.s2.t3.10

The following information regarding the working of the tūmbu sluices is based on in situ inspection of certain early sites by Rajan Gurukkal, since none of the tūmbu inscriptions is published (Fig.1). “The tūmbu was a single valve system operated without any devices for mechanical advantage. It consisted of two granite pillars installed in the reservoir on either side of the sluice-mouth. The pillars varied in height, according to the depth of the reservoirs. The distance between the two pillars was about one to one and a half meters. The pillars were connected to each other by a series of cross-slabs from the base of the sluice to the top. Each cross-slab had a hole in the centre with a diameter of about 5 to 8 inches. The base of the system was a rectangular enclosure built in granite on the bed of the reservoir. It had a rectangular opening of 1 ×2 feet. The stone above the opening had a long aperture and the stones on either side of the opening had slots, obviously for the movement of the shutter plank. It appears that, through the series of holes in the cross-slabs, a wooden rod lowered to the sluice-mouth. The edge of the rod must have been connected to a shutter-plank lowered through the long aperture so as to cover the opening of the sluice. The operation of the system was quite simple. The sluice-mouth could be opened by lifting the rod. The lifting of the rod was not difficult since a little opening would cause enough upward thrust from the flow of water for the shutter-plank to move easily. The sluice opened into an underground conduit which lead water to a well called etirakkiṇaru built outside the embankment. Unlike the ordinary wells, the etirakkiṇaru was constructed upwards Fig. 1. Tūmbu (sluice) system