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Spongy Iron Filter.—Spongy iron has been lately discovered to 
be a filtering medium of great value ; water passed through it has 
been found to be entirely free from bacterial germs, and it is the 
only known substance applicable to the treatment of large 
volumes of water which immediately destroy living bacteria. 
Spongy iron is metallic iron in a state of exceedingly fine 
division, which renders it sufficiently porous for water to percolate. 
It takes the place of carbon in other filters, it counteracts lead 
contamination, reduces the hardness of water, and needs cleansing 
only once in 12 months. 
Spencer’s Magnetic Filter.—This filter is very much in request, 
and claims to possess superior advantages, probably, however, it 
produces much the same results as the spongy iron filter, but 
there is little doubt that no other filter surpasses, if it equals, this 
invention in its chemical action upon water. 
The substance used is called ‘‘ magnetic carbide,” or in chemical 
language “magnetic protocarbide of iron.” Magnetic oxide of 
iror is made to combine with a small portion of pure carbon. 
The inventor states that he was led to the discovery by noticing 
that where magnetic oxide of iron existed in the strata, there the 
spring water was purest; where deficient, the water retained the 
organic impurities it had acquired on the surface. 
Malvern is quoted as an instance of the purity of the water, 
owing to the presence of this. 
The new red sandstone as deficient. 
_ Maignen’s Filter Rapide.—This is the last of the new type of 
filters of the present day. It will be known to the visitors at the 
Health Exhibition as having supplied the drinking fountains. 
The mechanism of this filter consists of a funnel pierced by 
apertures, over which an abestos cloth is fitted, and the filtering 
medium deposited uniformly over the whole of this surface. The 
filtering medium is a mixture of carbon and lime in a minute 
state of subdivision, one square inch of which—1-8th of an inch in 
thickness—is said to spread over 200,000 square inches of 
