SOME ASPECTS OF MICROBIOLOCY M THE "REATof filtering medium. Filtors C and D were opernted in sekics, with MENT OF SEWAGE* n chnnge in the order of the filters every week. The rnte of trentment of sewage in filters C nnd D hns been increhscd in stages from 90 to nbout 220 gallons per dny per cubic yard of filtering mediurii Ey T . 'C. TOMLINSON In Ihis pnlar'soiiic prob~cnls connected with tho occilrrcnnm O f fungi in the two filters together. The filtoring medium consists of &g, in pcrrolnting filters nm discussed with spcciiil refarcnm to tho trentmcnt grnvel, broken brick, rind broken grnGte from 1 in, to 2fr in. ill size. of sewngo by tho proress of nltemnting doiiblc fillrntion. Onc fnctor rvliich liniits tho nniount of mango whirh rnn Lw cfficicntly Settled purified in n ~~crcoliiting filter is tho nccumuliition of biologicnl filni in tho sewego pnsscs on to ono of the filters, kuown ns the primary filter. surfnnm In~mx of thu filtering medium. Tliis film consists of on nssocintion The emuont from the priniary filter, after a period of settlelneut ill of organisms, inrlutling dgm, fungi, bneteria, nnd nmorplious mnttcr dcrivfcl from tho own go nnd tho disintegrntion of tho film. Protozoa. After worms, mites, spiders, insects in cvcry stngC of dasclopment, nnd other ~ opernting in this order for a Period, in this Case week, the order orgnnisnis nrc nssocintetl with this film. Tlio putifrrntion of tho mango of tbc filters is chnngcd, the priiunry filtor becoming the secondnry is duo Inrgcly to tho nctivity of tlicao orgnnisins but crcessivo growth of filter and vice verse day per film at tho allrfnm of tho filter " ' B Y LPntlY i"'PdC tho FrcolntiOn of cubic yard of fi]tcrirrg for the two filkrs bgcther meBI1y wwngo to tho lower pnrtn of tho filter nnd nlso thc nnturnl nerntion of tho filter nnd mny tlius eniisc n docrcnsc in thc efficiency of tho promas.