728 Water in Relation to Health and Disease. 
so-called “ blood poisoning ” — of which we occasionally hear have 
their origin in this kind of water contamination. It is a form of 
pollution against which stockowners would do well to guard them- 
selves, and one which should be borne in mind in dealing with 
outbreaks of disease where water is under suspicion. 
Decaying leaves and other parts of trees, as well as lime and 
other matters, are also washed from the roofs of buildings, and 
if they are less hurtful than pigeon excrement, they certainly 
render water unwholesome when existing in large amount. 
Moreover, when lead gutters or tanks are in use, decomposing 
vegetable matter favours solution of the metal, and induces lead 
contamination, out of which may arise lead colic and other 
animal ailments. 
In the vicinity of white lead and other factories substances 
of a poisonous nature find their way to the roofs of buildings, and 
thence into the w r ell or tank. One of our most recent experiences 
of horse poisoning arose from contamination of water in this way. 
Pure as water may be when it falls to the ground, it soon 
suffers contamination to a more or less considerable extent. The 
nature of the polluting matters will depend in a large measure 
upon the description of soil and rocks with which the water 
is brought into contact, and through which, or over which, it 
passes. Whatever that may be, they invariably exist in one 
of two conditions, or in both. Either they undergo solution, 
or they are suspended. Dissolved matters may be derived from 
the surface, or from the subsoil, or from the underground 
formations which they traverse. 
Cultivated soil and marsh land no doubt give up a consider- 
able amount of animal and vegetable matter as well as the 
products of their decay. These latter present themselves in the 
form of ammonia, together with nitrates and nitrites. Certain 
phosphatic and other salts, derived from natural and artificial 
fertilisers, are also present. In its further passage through the 
earth a quantity of saline matter, the nature of which depends on 
the geological formation, also becomes dissolved in the water. 
Conspicuous among these saline bodies are chalk (calcium car- 
bonate), gypsum (calcium sulphate), carbonate of magnesia 
(magnesium carbonate), besides others such as Glauber’s salts 
(sodium sulphate), common salt (sodium chloride), Epsom salts 
(magnesian sulphate), &c. 
A few analytical examples 1 will show how variable is the 
composition of different waters and the proportion of inorganic 
constituents they contain. 
* Wunklyn, Water Analysis, 
