There are several methods extant for the purpose of purifying and softening water, and in the following brief account some of the chief features of these methods are summarized.  The Slack and Brownlow apparatus we will deal with first.  This purifier is one which is intended to remove the matter in suspension in the water to be treated by subsidence and not by filtration.  The apparatus consists of a vertical iron tank or cylinder, inside which are a series of plates arranged in a spiral direction around a fixed center, and sloping at an angle of 45 deg. on both sides outward.  The water to be dealt with flows through a large inlet tube fixed to the bottom of the cylinder, rises to the top by passing spirally round the whole circumference, and depositing on the plates or shelves all solids and impurities at the outer edges of the plates.  Mud cocks are placed to remove the solids deposited during the flow of the water upward to the outlet pipe, placed close to the top of the cylinder.  One of these tanks, a square one, is at work purifying the Medlock water at Manchester, and on drawing samples of water from nearly every plate, that from the lower mud cock showed considerable deposit, which decreased in bulk until the top mud cock was reached, when the water was quite free from deposit.  It is stated that one man would be sufficient to attend to 20 of these purifiers.

To filter or purify 2,000,000 gallons per 24 hours would require 40 tanks, 10 ft. by 7 ft. diameter, each doing 2,000 gallons per hour, and would cost, with their fittings, L6,400, including all patent rights, but exclusive of lime mixing tanks, agitators, lime water and softening tanks, engine and boiler, and suitable buildings, the cost of which would not be far short of L5,000, or a total of L11,400 to soften 2,000,000 gallons per 24 hours.  The labor and other working expenses in connection with this plant would not be less than that necessary to work the Porter-Clark process, which is given as O.55d. per 1,000 gallons.

The Brock and Minton filter press system is another method.  This patent press is made of steel, perforated with 1/2 inch holes.  On the inside of the shell there is first laid a layer of fine wire netting, then a layer of cloth, and lastly another layer of wire netting of a larger mesh than the other.  The matter treated is pumped into the body of the cylinder, the liquid passing through the filtering material to the outside, the solids being retained inside, and are got rid of by partially revolving the upper half to relieve it from the knuckle joint, and, after being raised, the lower half is turned over by machinery, and the solid matter is simply allowed to fall out into wagons or trucks run underneath for that purpose.  Such, in brief, is the manner of using this filter press for chemical works’ purposes.  The cost of each filter press, including royalties, is from L250 to L300, the size being 8 ft. by 4 ft. diameter.  Having a filtering area of 100 square