In kutcha roadside drains care must be taken that, in the process of cleaning, which generally consists in the removal of the bed, they do not in time become permanent roadside trenches without fall; it is much better to have no drains at all than this; mere depressions which, when dry, can be swept, and which will be washed clean after a heavy shower of rain, are much preferable. The proper bed-level of a kutcha drain should be permanently marked by wooden pegs driven well into the earth, and built into a masonry pillar, 1 foot 10 inches square, or by masonry profiles, at intervals of 100 feet apart; this shows at once if the bed-level or section has been unduly lowered during the process of cleaning out. [Sidenote: Flushing.] When designing a drainage system for a town it is essential that provision for flushing be made at the same time, otherwise the drains become receptacles for filth for about two-thirds of the year. This can be arranged by the construction of flushing tanks, which, when full automatically discharge into the drains, by water mains laid underground discharging into the head or summits of the drains; and also by the drains being divided up into convenient sections by stops or sluices, which are lifted automatically, or by manual labour, when the section is full of water, thus ensuring an effective flush. [Illustration: FIG. 1. AUTOMATIC FLUSHING TANK ] A type design of an automatic flushing tank is shown in Fig. 1. These cost about Rs. 100 each complete, the syphon pipe alone representing some Rs. 30. Where sufficient head is not unavailable for this type, Adams’ Patent Adamic Flusher may be suitable. These cost about Rs. 70 for a 4″ pipe size, and works with a head of 10 inches. Where sullage water is discharged into storm-water drains this should be treated in sullage filters at convenient intervals. _See_ Fig. 18, page 36. [Sidenote: Masonry drains.] The most suitable form for surface drains is the semi-circular base, with side slopes of 1 to 2·4, as the discharge is only slightly less than that of the ovoid section, and the drains are more easy to construct. They can be easily swept clean, or run through with a wooden board made to fit the section, and pushed along by a boy. The Dacca type rectangular drain, as shown in Fig. 2, page 5, is very suitable for narrow lanes. The dimensions can be altered to suit local conditions. Much useful information as to the preparation of drainage projects, and tables of discharges of different sections, will be found in Practical Instructions in Surface Drainage, by Mr. H. A. Gubbay, Executive Engineer, Public Works Department, published by the Government of Bengal.