^Q/J FILTERING APPARATUS. 



Th- new metal Thefe properties do not charadlerize any of the known me- 

 »ot yet namsd. jg]^^ ^^^^ i g,^ thereCore authorize:! tocontider it as a new one, 



to which I (hall give a name when I have explored its nature 



more fully. 



XVII. 



Defcription of an Apparatus fnr filtering Water. By Meff. 

 Harman an<i Dearn, of Redriff. 



Apparatus for X HE waters which run near or upon the furface of the earth, 

 filtenng water. ^^^ ufually contaminated by the remains of animal and vege- 

 table fubftances in their progrefs towards entire decompofilion, 

 as well as by the minute powder of earthy or mineral bodies, 

 which render it turbid and lefs fit for the purpofes of domeftic 

 life. Spring or pump waters, by a natural filtration through 

 the fandy ftrata of the ground, are mofily cleared from thefe 

 mechanical admixtures ; but in many places, as is the cafe 

 with ihofe of our metropolis, they are rendered impure, or, as 

 it is called, hard, by an actual foluLion of fulphate of lime or 

 platler of Paris, which prevents their lathering with foap, aad 

 probably renders them le(s wholefome; befides which, they 

 ufually carry a portion of the drainage water in great towns, 

 which renders them ofienlive at certain feafons, and at all times 

 lefs worthy of confidence. For thefe and numerous other 

 reafons, it has always been confidered as a defirable obje(Sl 

 to clear waters, by filtration, from thofe impurities which ren- 

 der them lefs limpid, and a variety of apparatus have been 

 offered to the public for that purpofe. 



In all thefe the procefs of nature has been imitated ; namely, 

 by cauling the water to percolate either through fand or a 

 fand-Ilone ; the latter of which, though coftly, feems at pre- 

 fent to be almoft the only method in ufe among us. 



The contrivers of the fimple and cheap apparatus delineated 

 in Plate VI. are Mell". Harman and Dearn, potters at RedrifF, 

 who remark, that the filtering-ftone is not only expenfive and 

 liable to be clogged up and fpoiled by the bodies depofited in 

 its pores from the water, but that, as thefe bodies are a6lually 

 in the progrefs to decay and decompofition, they are in fome 

 cafes found actually to change the flavour and aiTedt the purity 



of 



