Every gauge-reader has to be given definite instructions as to the gauge reading to be maintained, until further orders, in each distributary. At the places where the large branches take off, the gauge reader is instructed what gauge to maintain in each. In the event of too much water arriving, he turns the surplus into the escape if there is one. If there is no escape he has usually to raise the gauge readings of the branches by equal amounts. By means of the telegraph, adjustment is promptly effected at the headworks. It has already been mentioned that rain may cause an abrupt reduction in, or even cessation of the demand for water. At the same time it increases the actual supply. Rain, or the signs of rain, in any part of a canal system ought always to be reported to the other parts. Owing to changes in the channels, to fluctuation in the water level of the river, especially during the night, to rain or to changes in the temperature and moisture of the air and to lack of continuous attention on the part of the gauge reader, particularly at night, there is a constant, though perhaps small, fluctuation in the water level in all parts of a canal. It may happen that--owing to enlargement of the channels by scour, or to other causes--the channels of a canal system are able to carry more water than was intended. In such cases the channels are usually run with as much as they can carry. This may give a lavish supply and a lowered duty, but it increases the irrigated area. To restrict the supply would cause loss of revenue. Sometimes however, it is restricted to prevent water-logging of the soil. The proper procedure is to extend the canal to other tracts. In India the farmers pay for the water, not according to the volume used, but according to the area irrigated. Different rates per acre are charged for different kinds of crops according to the varying amounts of water which they are known to require. Sugarcane, which is sown in the spring and stands for nearly a year before being cut, thus extending over the whole of the kharif and most of the rabi, is assessed at the highest rate. Next comes rice which crop, though only four or five months elapse between its sowing and reaping, requires a great quantity of water. Gardens which receive water all the year round also pay a high rate. Other kharif crops are cotton and millet. The chief rabi crops are wheat, barley and “gram.”