In mofussil towns in Bengal the night-soil is generally collected from public and private latrines by conservancy carts drawn by bullocks, and varying in capacity from 60 to 200 gallons. These, as a rule, begin work early in the morning so as to avoid causing a nuisance in the thoroughfares, travel at a very low rate of speed, not over 2 miles an hour, and only make one trip a day, in the majority of cases, owing to the distance the trenching grounds are away from the centre of the town. This means that a large proportion of the human excreta remains at least 24 hours in the receptacles of the latrines in the immediate vicinity of densely populated localities. In the temperate climate of England it is accepted as an axiom that sewage should never be more than 24 hours in finding its way to the outfall, as it is, when it has begun to decompose, more dangerous than when fresh and decomposition sets in much more quickly in the semi-tropical climate of Bengal. In many cases the quantity of night-soil collected per head per diem is exceedingly small; the average amount of solid matter evacuated by natives may be taken at 10 ounces, and of urine 30 ounces, whereas returns from several municipalities show a quantity varying from ·047 to ·37 of a gallon removed by the conservancy carts. These quantities are, however, calculated on the entire area of the municipalities, including the suburbs, where, owing to the custom of Indians, the gardens and adjacent fields dispose of a large quantity. In order to obtain reliable results, the densely crowded areas should be divided up into blocks or sections, keeping the figures well separated in the municipal books, the density of population per block calculated and the quantity of night-soil removed registered daily. Many of the Indian bazaars are long narrow ones, situated on a high ridge of ground, in which case it is desirable to have several trenching grounds, one for each block or group of blocks, instead of having one large one situated at a considerable distance from the centre of the town.

In order to effect the speedy removal of fÆcal matter, the provision of suitable conservancy carts is of vital importance. Fig. 15, page 32, is an illustration of Crawley’s Patent Night-Soil Cart, and is a good one for general purposes. It is made entirely of wrought iron, with an air-tight door for filling and emptying; the latter is done by releasing a clip from the front of the barrel which connects it to the shafts and opening the lid, when the barrel turns on its centre and shoots out the contents. A 75–gallon capacity cart costs Rs. 130; a 110–gallon, Rs. 160; and a 200–gallon one Rs. 225. Small carts are preferable to large ones, as they take a shorter time to fill, and therefore tend to the more speedy removal of night-soil from crowded localities. They are also more easy to handle at the trenching grounds.

It will sometimes be found advisable to provide receptacle carts for removing receptacles from latrines. Fig. 16, page 33, shows this arrangement. These, however, owing to their weight, and to the difficulties of placing and removing the receptacles when full cannot, excepting under special conditions, be recommended for municipal purposes. They cost, including 12–gallon receptacles, about Rs. 275.

Each latrine must be provided with a receptacle, into which the buckets are emptied, this being placed in a convenient position at the back of the latrine; the cart starts on its rounds with six empty receptacles, visits the latrines where it picks up the full ones, and replaces them by clean ones. They are supplied in 6, 12 and 24–gallon sizes to suit requirements, and the arrangement avoids the nuisance of transferring the contents to a second utensil.

Hand carts are necessary in order to remove night-soil from houses built in narrow lanes and places where it is impossible to get bullock carts into. Fig. 17, page 34, shows a convenient arrangement for this. The receptacles vary in size from 12 to 33–gallons, and cost from Rs. 37 to Rs. 68 each; the bodies are detached from the hand truck by simply raising the handles and disengaging the two-forked bearings with the trunnion; they are fitted with a hinged lid and are made of strong galvanized iron; the hand truck is of strong and light design, the whole being of wrought iron.

Where regularly-flushed masonry-lined side drains are unavailable, the drainage from houses must be led into masonry-lined cesspools, which will be cleaned out daily by the municipal sweepers, and the contents removed in conservancy carts. These cesspools should be semi-circular in shape, and plastered on the inside with Portland cement. In many cases, where masonry drains exist, it will be found possible to intercept this sullage, and purify it through Biological Agency in small tanks, filled with pieces of vitrified brick, broken so as to pass through a 2–inch ring. The broken bricks will last for about a year, when they should be renewed.

A drawing of a small Sullage Filter is given in Fig. 18, page 36. The estimated cost of which is Rs. 180.

It is of the very greatest importance to insist on the prompt disposal of night-soil and refuse, and all means which aid this, good roads, proper care and feeding of animals, good carts, and the provision of houses for sweepers, help to a great extent.

In order to systematise the removal of night-soil from private latrines, all these should be registered and numbered according to the beats of the attendant, or otherwise definitely indicated and located, and the sweepers told off accordingly.

When purchasing carts especial attention should be paid to the quality of the wheels and axles. The carts should not be too heavy and must be of a convenient height to facilitate working.