50 THE DOMESTIC WATER FILTER. 



filtered, A filter is therefore purchased which is supposed to be 

 capable of rendering the water passed through it absolutely pure, 

 and the householder is satisfied that he and his family are pro- 

 tected from the risk of disease so long as they drink filtered 

 water. How much reliance may be placed on the filter to purify 

 the water will be seen further on when I refer to the results of 

 " An inquiry into the relative efficiency of water filters in the 

 prevention of infective diseases," conducted by Drs. Sims Wood- 

 head and Cartwright Wood, and published in the November and 

 December, 1894, numbers of The British Medical Journal. In 

 the case of the Public Water Supply, or what is usually denomi- 

 nated " tap water," the necessity for the use of filters is much 

 more apparent than in that of the private supply or the water 

 collected from the roofs of buildings, for the former always 

 contains a large quantity of suspended matters which are only 

 too visible to the naked eye, and which boiling will not precipi- 

 tate, and has a strong peaty taste when drawn from Enoggera 

 or Gold Creek, and either a mineral or muddy flavour, as the 

 river is low or in flood when obtained from the Mount Crosby 

 Works. The tap water, containing as it does such an excess of 

 suspended matters, will in a very short time clog and destroy 

 any filtering medium, unless renewed very frequently. Now, 

 in niiOst of the filters in use here the medium is charcoal, either 

 in the form of blocks or granular, and with the filter, when 

 purchased, only a second block, or an extra change of charcoal 

 is given, so that when these are rendered useless it is very 

 difficult if not impossible to obtain a fresh supply of charcoal or 

 blocks. One is then recommended to boil the charcoal and dry 

 it in the sun. Well, this might be of some use in destroying 

 bacterial organisms provided the boiling were continued suffi. 

 ciently long to destroy the spores, and provided the charcoal had 

 not been clogged by having muddy water passed through it, in 

 which case the boiling would not free the granules of charcoal 

 from the earthy and organic matters which adhered to them, but 

 would in all probability tend to fix them more firmly to the atoms 

 of charcoal ; and in the case of blocks, boiling would not free 

 the clogged pores, but would render them impervious. I have 

 had some experience in this respect recently which I will briefly 

 relate. The house in which I resided prior to removing to my 



