The daily morning journal and courier., 1904-11-18

the lakes is owned by the water com- pany, and in fact large proportion Of the total area of the watersheds. The lakes and streams are very carefully guarded from pollution of any kind, and all leaves and vegetable matter rabed up from the edges and burned.
 Tn fact the conditions in these water sheds are almost ideal for surface water supply.
 The West river watershed differs in degree rather than in kind from those already mentioned, the territory being largely pasture land, and the population being relatively smailS probably about 400 persons iii all.
 The territory, however, is so large, some fourteen square miles, that very careful policing is necessary to Insure satisfactory sanitary conditions, and when there is high water In times of freshet large quantities of silt are sometimes brought down.
 On the whole, conditions are better here than In other localities having supplies of similar size and location.
 Mill river, which supplies Lake Whit ney. presents radically different con- dftions from the other watersheds. It's area is much larger, about thirty six square miles, and the population considerably greater, some 5000 proba- ply.
 What is still more important from 2 sanitary point of view is that about lone-third Of this population is concen- trated in villages along the banks of the streams. Some of these villages are. severed and do not present such nenacing conditions as threaten so many American cities. Tn such manu- featuring settlements however, it is inl- practicable to prevent occasional polu- tion. The possibility Is always present of extreme danger in case of an epi- demic in some water-bourne disease like typhoid fever. Tn times of high water this river carries large amounts of sediment, but only for short periods.
 A controlling factor in the question of the necessity of Altering this sup ply is that it is essential for drawn water from Lake Whitney at all times, as the other supplies can not alone furnish New Haven with sufficient wa ter.
 The whole question of the protection and filtration of it's supplies has been carefully considered by the water com pany, with the assistance of its own engineers and an engineer from New York. who is an expert in all questions of water supply and puriffcation, and as a result it was decided to filter the Lake Whitney supply.
 In deciding what type of filter to be used many considerations had to be weighed.
 1 The two kinds of filters in common use are the mechanical and slow sand l types. Both are sand filters in the sense that the water passes through a bed of sand two or more feet in thick ness, but they differ radically in the method of operation. In the slow sand k type the water merely passes by grav- l ity down through a bed of carefully prepared sand, usually at a rate of nine feet vertically per day.
 In the mechanical type some chem ical. usually sulphate of aluminium, is l first added to the water. It causes the suspended matter to precipitate large- ly and the water then passes through the sand at rate of perhaps forty times as great as in the other type, that is it would filter in one day column of water about $50 feet high. The use of chemicals is absolutely es- sential in mechanical filtration, but is not attended with any harmful effect if properly managed. In deciding be- tween these types there is one other point which you may be sure is all ways considered, that is the question of cost.
 The slow sand filtration plant limits at Lake Whitney covers about five acres, and is divided into twelve beds.