556 
POPULAR SCIENCE REVIEW. 
consumption. The only food which is ever substantially 
supplied to him, and this only in his infancy, which requires 
no addition of water, is milk. Potatoes contain nearly as 
much water as milk, and those who live entirely on potatoes 
require but little water. A curious proof of this was observed 
during the potato famine in Ireland. It was observed as a 
remarkable fact that in their great poverty the people of 
Ireland were consuming larger quantities of tea, coffee, and 
sugar, which might be regarded as luxuries. The increase, 
however, of these luxuries depended on the fact that whilst the 
starving people of Ireland were fed with rice, flour, and other 
dry food, as substitutes for the potato, they were obliged to 
have recourse to water for drink. As in the case of all other 
civilized people, they preferred their water flavoured, and 
partook of tea and coffee sweetened with sugar. 
Water, then, being essential to the life of man, let us inquire 
into its natural sources and fitness for the dieteticaluses of man. 
Water exists naturally upon the surface of the earth, in its 
interior, and in the atmosphere. The heat of the sun daily 
carries enormous quantities of water into the atmosphere, 
from whence it is precipitated upon the earth in the form of 
snow and rain. This percolates into the earth from whence 
it comes again in the form of springs, and may be reached by 
digging wells. Much of this water finds its way into rivers 
with the rain from the surface, and these empty themselves into 
the ocean. As the water in its course from the atmosphere to 
the sea dissolves all soluble matters it meets with in the earth, 
and these are not evaporate! again, sea water is a strong 
solution of various salts. The principal of these is chloride 
of sodium. The following analysis of sea water from the 
German Ocean gives the other constituents : — 
Solids ill 100 parts of waler . . . 
15 
Chloride of sodium in 100 parts of solids 
77-78 
Chloride of magnesium 
55 
55 
55 
8-12 
Chloride of potassium 
55 
55 
55 
0-97 
Chloride of calcium 
55 
55 
55 
1-39 
Bromide of magnesium 
55 
55 
5 ’ 
0-47 
Sulphate of lime 
55 
55 
55 
3-49 
Sulphate of magTiesia 
55 
55 
55 
6-79 
Carbonate of lime 
55 
55 
55 
0-56 
Snicate of soda 
55 
55 
55 
0-25 
100-00 
The sea also contains oxygen and carbonic acid gas. 
Sometimes the water which passes into the earth comes up 
highly charged with mineral constituents. When such waters 
