After first ascertaining that the well has not been temporarily blocked by interested persons—even here in the remote interior of the desert there is an inherent objection to the paying of taxes—the bed and sides of the water-channel are made as smooth as possible for a distance of five or ten paces below the mouth of the well, so that the water flows away with an even ripple. A small pointed stick is now inserted in the centre of the bed of the stream, in such a way that the top of the peg is exactly flush with the surface of the water. Then the Omda, hitching up his flowing robes, steps into the stream, and, selecting a gauge of suitable dimensions, fixes it firmly in the bed of the channel, in such a position that the whole of the flow passes freely through, without raising or lowering the surface of the stream above, as indicated by the peg. The interior of the gauge, a roughly-made wooden frame, is intended to be a definite number of centimetres in length, but in many of those used there is a small error. As soon as the stream flows evenly over the gauge or weir, without its surface-level being altered, the depth of water is measured on a scale. The latter is wetted and plunged into a heap of dry sand before being used, the depth of water being indicated by that portion of the scale from which the sand has been removed by the immersion. Observations are made at both ends of the weir to insure any error due to want of horizontality of the frame being detected. The actual discharge is reckoned in ‘qirats’ and eighths of a qirat (tumns), a qirat being a water-section of 64 square centimetres. For example, if the depth of water passing over a gauge having an internal length of 40 centimetres was found to be 8 centimetres, the water-section would amount to 40 × 8 = 320 square centimetres, which would be reckoned as a discharge of 5 qirats.