WlfAT IS IN THE WATER? 
101 
clear that a complete and satisfactory answer to this question cannot be 
founded upon chemical analysis alone. By this means we can ascertain the 
amount of inorganic matter in the water with great accuracy, and as far as 
the elements are concerned, we can determine what such matter consists of. 
We can also show the influence of the inorganic or mineral constituents of 
the water in decomposing soap, and in other ways affecting its use for cer¬ 
tain domestic or manufacturing purposes. It is but rarely that the mineral 
constituents of water from any of the ordinary water-supplies are such as in 
any way sensibly to affect the health of those who drink it. In a sanitary 
point of view, therefore, the inorganic or mineral constituents of drinking- 
water are looked upon as comparatively, if not wholly unimportant. It is 
organic impurity, and products resulting from its decomposition, that give to 
water the qualities most to be feared by those who drink it, and here, un¬ 
fortunately, chemistry does not aid us very much. It does, however, afford 
us some insight into the general nature of the organic impurity that is or has 
been present in the water. We can determine, within certain limits, the 
amount of organic matter, not so accurately as we can determine the inor¬ 
ganic constituents, but sufficiently so for practical purposes. We can ascer¬ 
tain the presence or absence of nitrogen and sulphur in the organic matter, 
and thus judge of its animal or vegetable origin. Even if organic matter be 
wholly or almost wholly absent, we may discover products of its decomposi¬ 
tion in the forms of ammonia or nitric acid, from which it may be concluded 
that there is a connection somewhere between the water and organic impu¬ 
rity, and that although the latter has been rendered harmless by its decom¬ 
position, slightly varying conditions might present it in a less advanced state 
of decay, in which it would be decidedly deleterious. Other products of 
decomposition, such as sulphuretted hydrogen, would of course bespeak the 
necessity of avoiding its use, but this makes a direct appeal to the senses 
which hardly requires to be verified by chemical analysis. 
But when the chemist has done his utmost through the exercise of his art, 
he can only represent, and that approximately, the quantity of organic 
matter, say one, two, or four grains in a gallon, and, by a more refined appli¬ 
cation of his art, the presence or absence of nitrogen in this matter. Beyond 
this he cannot specify its particular nature, source, or condition. The quan¬ 
tity is too small and the task too difficult to admit, in an ordinary analysis, 
of its examination being carried even as far as the available means of the 
chemist extend. The results of analysis are therefore usually expressed in 
very general terms. 
All water employed for domestic purposes contains some organic matter, 
aud if, as stated in the document to which we have already referred, “ it is 
not the quantity of organic matter in water so much as its quality which de¬ 
termines its dangerous properties,” what is the value of analysis in such a 
case, seeing that by this means the quality cannot be ascertained? Un¬ 
doubtedly, taken alone, and in the form in which the results are usually 
expressed, analysis does not go for much, but it does nevertheless afford some 
assistance in judging of the extent to which the water has bhen exposed to 
the polluting influences of decomposing matter. This is, perhaps, of more 
value as a guide with reference to the dietetic use of water under ordinary 
circumstances than with special reference to cholera or other contagious 
diseases. In these cases we are told that modern pathological science has 
almost demonstrated that the real agents of such diseases are living germs, 
which the most refined appliances of the chemist have failed to discover, 
Avhich chemical analysis cannot therefore indicate, and with reference to 
which no system of filtration can be depended upon for their removal. 
In answering the question we hare assumed to be put, we should neither 
