April 28, 1905.] 



SCIENCE. 



651 



It is true that every time we drink fil- 

 tered river water we are imbibing a puri- 

 fied sewage of greater or less concentration, 

 and, with a continued growth of our great 

 cities, and the increased pollution of our 

 water-sheds, it would seem that the day is 

 not far distant when a naturally 'safe and 

 suitable' water shall become a thing of the 

 past, and we shall be forced to employ a 

 purified water as our only source of supply. 



Let it be remembered, however, that we 

 can control the artificial purifying devices 

 of which we make use, and we can repair 

 them, should they at any time refuse their 

 work. 



The case is quite different, however, 

 when our safety lies upon the proper op- 

 eration of those natural processes of puri- 

 fication which are beyond our power to 

 direct. Such purification, to be satisfac- 

 tory, must appeal to us as being continu- 

 ously effective. 



We know very well that the raising of 

 water vapor by solar heat will leave objec- 

 tionable material behind, and we are satis- 

 fied that the result is perfect and that it 

 will continue to be so during all time. We 

 also know that the filtering and oxidizing 

 power of the soil is very great, and in gen- 

 eral we are willing to pin our faith upon 

 its efficiency. But we can not avoid a feel- 

 ing of uncomfortable doubt when we note 

 that a small amount of soil has been given 

 a large quantity of work to perform, and 

 we naturally ask, can not the purifying 

 powers of such soil be overtaxed, with the 

 result that our protective filter will become 

 damaged at a point beyond reach of re- 

 pair 1 Let an English case be quoted here : 



A certain farm-house was notoriously un- 

 healthy. The inmates had suffered at various 

 times from diphtheria and typhoid fever. The 

 water had been examined, and was reported to be 

 satisfactory. Upon examining the premises it 

 was found that there was a water-closet in the 

 house, which was in good order, but where the 

 contents were discharged was unknown. The 



drains were said to be satisfactory and never to 

 get blocked, and upon tracing them, it was found 

 that they discharged into a dry-steyned cesspool 

 witliout overflow about four yards from the well, 

 both sunk in the gravel, which here was twenty 

 feet or more in thickness. This well yielded an 

 unfailing supply of water, which was used for all 

 domestic purposes, and upon analysis it was 

 found to be remarkably free from organic matter. 

 It was said to be always cool, bright and spark- 

 ling, probably due to its containing a very exces- 

 sive amount of chlorides and nitrates derived from 

 the sewage percolating into the subsoil and the 

 opinion was expressed that the water was a con- 

 centrated purified sewage. This was not believed 

 at the time, but when the cesspool was filled in 

 and the sewage carried elsewhere, the well ran 

 dry. There is no doubt that in this case the 

 same water was used over and over again. After 

 being defiled by the closet, slops, etc., it ran into 

 the cesspool, then filtered through the soil, in its 

 progress the organic matters becoming completely 

 oxidized, and ultimately it found its way back to 

 the well, to be utilized again for domestic pur- 

 poses. Doubtless at times, possibly after heavy 

 rains, the cesspool contents filtered too rapidly for 

 complete purification to be eff'ected, and this im- 

 pure water may have been the cause of the ill 

 health amongst those who consumed it. 



In this instance, as in the one quoted by 

 the author, the danger signal was held out 

 by the chemical side of the investigation 

 alone, the other methods of inquiry failing 

 to detect any trace of evil. 



It would seem that bacteriology deals 

 with the present and that chemistry, be- 

 sides throwing light upon the past, does 

 to some degree, prophesy what may happen 

 in the future. 



Many a water which the bacteriologist 

 has pronounced harmless lias been con- 

 demned by the chemist because of what it 

 might unexpectedly become at some future 

 time ; and, on the other hand, the bacteriol- 

 ogist has time and again shown the pres- 

 ence of unlooked-for pollution when the 

 chemist might search for it in vain. 



A good instance of the saving of the 

 situation by a 'sanitary survey' when both 

 chemistry and bacteriology show adverse 



