FILTER. 



purest part of tiie liquor distils drop by 

 drop out of the vessel, leaving 1 the dregs 

 behind : a filter of this kind acts upon the 

 principle of the syphon. Water is freed 

 from various impurities by means of ba- 

 sins made of porous stone ; this is often 

 very necessary at sea, when the water be- 

 comes foul, and on land, where there are 

 no fresh springs. The filter is of use to 

 all those in and near the metropolis, who 

 are supplied with water from the Thames, 

 the New River, and the ponds from 

 Hampstead. Many patents have been 

 obtained for filtering machines, which 

 may be seen in various parts of London. 



We shall observe, that Mr. Peacock 

 obtained, about twelve years since, one 

 for a new species of filtration, by means 

 of gravel of different sizes, suitable to the 

 several strata. The various sizes of the 

 particles of gravel, as placed in layers, 

 should be nearly in the quadruple ratio 

 of their surfaces; that is, upon the first 

 layer, a second is to be placed, the diame- 

 ters of whose particles are not to be less 

 than one half of the first, and so on in this 

 proportion. This arrangement of filter- 

 ing particles will gradually fine the water, 

 by the grosser particles being quite inter- 

 cepted in their partly ascending with the 

 water. An advantage in these filters is, 

 that they may be readily cleansed by 

 drawing out the body of the fluid, by 

 which it will descend in the filter, and 

 carry with it all the foul and extraneous 

 substances. 



A patent was also granted to Mr. Joshua 

 Collier of Southwark, for a most ingeni- 

 ous method of filtering and sweetening 

 water, oil, and every other liquid. The 

 following 1 is the contrivance, which com- 

 bines the application of machinery with 

 the antiseptic properties of charcoal. 

 Fish oil is one of the liquids which he 

 had particularly in view, to free it from 

 every thing disagreeable, either in taste, 

 smell, or colour ; to accomplish which he 

 poured a quantity of oil into a conveni- 

 ent vessel, heated to the temperature of 

 120 of Fahrenheit's thermometer, add- 

 ing caustic mineral alkali of the specific 

 gravity of 1.25. He then agitated the 

 mixture, afterwards allowing" it to stand 

 till the sediment subsided, and then drew 

 it off' into another vessel, with a suffici- 

 ent quantity of burnt charcoal finely 

 powdered, and a small quantity of diluted 

 sulphuric ackl, to decompose the sapo- 

 naceous matter still suspended in the 

 oil, when the oil became clear at the 

 surface: he then agitated the contents 

 of this vessel, and left the coally, saline, 



and aqueous particles to subside ; aft'er- 

 wards passing it through proper strainers, 

 when it became quite transparent and th 

 for use. 



The principle of the improved filter- 

 ing machines consists in combining hy- 

 drostatic pressure with the mode of fil- 

 tering per ascensuin, which procures the 

 peculiar advantage of causing the fluid 

 and its sediment to take opposite direc- 

 tions. The filtering surface remains the 

 same, while the dimensions of the cham- 

 ber in which the sediment is received 

 may be varied. To adapt the machines 

 to every purpose for which they are in- 

 tended, chambers must be provided, of 

 various capacities, for the precipitated 

 matter. The space required is very 

 great with respect to the oil trade, and 

 as all dimensions will be required oc- 

 casionally, no particular limits can be 

 fixed. For distilleries and breweries 

 tiiey may be smaller in proportion, and 

 a very small chamber will be sufficient 

 for domestic economy. If water is to be 

 freed from noxious particles, it must be 

 made to pass through an iron box in its 

 way to the filtering chamber, and the 

 box must contain charcoal finely pow- 

 dered ; the water is received into this 

 box, and delivered by two apertures, 

 which are opened and closed by cocks. 

 Another part of the invention consists hi 

 filtering machines in the form of stills, in 

 which charcoal may be repeatedly burnt, 

 aftev any fluid substances have passed 

 through it, for the purpose of freeing 1 

 them from noxious particles, or discharg- 

 ing their colouring 1 matter. 



To the filtering apparatus of Mr. Col- 

 lier, instruments are attached for disco- 

 vering the comparative qualities of oils, 

 which depend, in some measure, on their 

 specific gravities : spermaceti oil, when 

 compared with fish oils, being as 875 to 

 920. To do this a glass vessel, of any 

 shape most convenient, is employed, 

 with a glass bubble and a thermometer. 

 If the oil is pure, the bubble sinks, when 

 the mercury rises to a particular stand- 

 ard. When spermaceti oil is impure, 

 the bubble floats, though of the tempe- 

 rature required. To determine the ten- 

 dency of oils, used for burning', to con- 

 geal in cold weather, a freezing mix- 

 ture may be put into a phial of thin 

 glass, into which let a thermometer be 

 immersed, and a single drop of the oil 

 permitted to fall on the outside of the 

 vessel, where it will instantly congeaL 

 As the cold produced by the mixture de- 

 creases, let the temperature be observed. 



