38 
POPULAR SCIENCE REVIEW. 
limited extent, possesses some of the advantages of the arrange- 
ment of Mr. Danchell, next to be described 
The cistern filter sold by the London Water Purifying 
Company is constructed according to Danchell’s patent. The 
chamber containing the filtering material is immersed in the 
water-cistern, and in whatever way the tube passing out of the 
SILICATED CARBON FILTER 
AND MAGNETIC CARBIDE 
FILTER. 
A, Silicated Carbon or Mag- 
netic Carbide. 
*• d, Unfiltered Water. 
e, Filtered Water. 
MOULDED CARBON FILTER. 
b, Moulded Carbon. 
d, Unfiltered Water. 
e, Filtered Water. 
LONDON "WATER PURIFYING 
COMPANY’S FILTER. 
c, Animal Charcoal. 
d, Unfiltered Water. 
e, Siphon. 
cistern is made to go, the water during filtration passes up- 
wards through the filtering material. Fig. 3 represents a sec- 
tion of this filter with the delivery tube arranged as a common 
siphon, passing out of the top of the cistern. 
By this method of filtration, only those particles which have 
not subsided before the water passes through the filter come in 
contact with the filtering material, and even then in such a 
position as to favour their falling away from it to the bottom 
of the cistern. In the ordinary arrangement of filters all the 
matters suspended in the water, whether separated by subsi- 
dence or filtration, lodge in and on the upper parts of the fil- 
tering material, thereby more rapidly choking up its interstices. 
The pipe delivering the filtered water is closed by a tap, and 
the water is only drawn off through the filter as wanted. This 
arrangement is attended with both advantages and evils. The 
great advantage we see in it is that the water, in quantity suffi- 
cient to charge the chamber containing the filtering material, 
remains in contact with this material during the period — it 
may be for many hours — between the times of drawing off any 
water : in consequence of this, whatever purifying power is 
