At! Analysis of Filtered W'afvr — Dodge. 78 



rnendatious of physicians and others in this city, that we adopt the 

 })hm of filtering all the water which we are to drink. The cost 

 of a domestic filtering apperatus is not great. One could be con- 

 structed quite cheaply from simple parts and materials. 



(The plan of a cheap filter suggested by Dr. Smart, an emin- 

 ent sanitarian, was given on the blackboard.) 



Bone charcoal can be obtained from druggists. It is not ex- 

 pensive, varying according to quality from twelve cents to fifty 

 cents per pound. It will retain its purifying power a good while 

 before needing to be replaced. An efficient filter is something 

 more than a strainer. The small globuler filters which are attach- 

 ed directly to the faucets of supply pipes, seem to be hardly more 

 than strainers, as the amount of filtei-ing medium in them cannot 

 be great and as the water passes through rapidly and under strong 

 pressure. A quiet and gradual passage of the water through a 

 comparatively large amount of filtering medium seems essential to 

 thorough effectiveness; still the small filters are much better than 

 none. A good filter does not merely separate out the visible par- 

 ticles of suspended matter, such as clay and sand, from the water. 

 l>one charcoal, by a peculiar absorptive power, separates also most 

 of the organic matter which is in a state of partial or complete so- 

 lution, and besides this, it destroys the organic matter in great 

 measure by a process of oxidation. In this respect it is much supe- 

 rior to wood charcoal. In fact, wood charcoal is said by those who 

 have investigated the subject to be of very moderate efficiency, 

 and not much better than sand or a similar material for purifying 

 water. In many cities the entire vater supply is filtered, but on 

 so large a scale nothing more than sand and gravel is generally 

 employed, though as stated, spongy iron seems to be coming into 

 use. A filtration through sand is of much advantage. It takes 

 out all course impurities, but it do^s not effect a thorough sanitary 

 purification, like bone charcoal. As we all know% no filtration 

 of any kind is employed here in connection with the city water 

 works. The new intake pipe terminates in a mass of loose stone- 

 work which serves the purpose of a coarse strainer and that is all. 

 Filtration of the great amount of water pumped at the works 

 would probably, under present circumstances, of location, etc., be 

 impossible. Perhaps when the water is taken higher up the river, 

 a system of filtering basins, etc., may be adopted. This is much to 

 be desired. 



