Water and other Fluids. 341 



•ultra of improvement in an art of fo much importance to 

 fociety as that of purifying water. So far, however, as con- 

 cerns the difficulty hitherto complained of in the procefs of 

 filtration, we think he has completely fucceeded. He has 

 aUb confuhed the only true principles which can (liorten the 

 extreme tedioufnefs of this procefs. 



Firft, The grofler particles and corruption form no obftruc- 

 lion, as the fluid takes a dire&ion from the exterior of the 

 filter inwards. 



Secondly, As the filtering medium comprifes numerous 

 cylinders of fmall diameters, the contents of which are alfo 

 fmall compared with their external furface, the percolating 

 fiipcrficies''aTtogetber is as much increafed as the magnitude 

 of the machine will allow. 



Thirdly, As thefe cylinders do not themfelves form the 

 veffel containing the fluid, but are placed in the veflel, they 

 fuftain a preflure proportioned to the whole perpendicular 

 height of tlie fluid within it. 



Moreover, it muft be admitted that the fubftance chofeh 

 as a percolating medium is free from any poffible chemical 

 objedlion, being formed of materials of fufficient durability, 

 and altogether infoluble in water and moft other fluids. 



■ Fig. I, (Plate IX.) a feclion of a ciftern of any materials 

 and of any fize, with a cock A to draw water for common 

 ufe. B, a leaden refervoir, holding 4, 6, or 8 gallons, placed 

 infide, the cock C of which comes through and is foldered 

 into the fide of the ciftern, from which filtered water is drawn 

 off". The bottom of the refervoir is raifed about two inches 

 above the lower edge D D of the fide B, that it may fiand 

 above the fediment in the water. — EE are 4, 6, or more 

 hollow cylinders, plofed at one end, faftened into the lead, 

 formed of argil and filex baked together in a potter's kiln, 

 through which the water percolates into the refervoir B. — > 

 F, a tube a few inches diameter, as high as the ciftern, with 

 a fmall aperture at top for the air to efcape, while its dimcn- 

 fions anfwer Another purpofe. As water Will find its level 

 when the machine has been long at reft, the water will ob- 

 tain the fame altitude in the tube as it ftands at in the ciftern ; 

 and whenever it is drawn off for common purpofes, the fame 

 principle caufcs it to fall in the tube, puffing inverfely through 

 Vol. VI. I i the 



