SILICA. Dae 
chloride 3-7, magnesium sulphate 2°30, caleium sulphate 
1:4, calcium carbonate 0-03, with some magnesium bromide 
and probably traces of iodides, fluorides, phosphates and 
borates. ‘I'he bitter taste of sea water is owing to the salts 
of magnesium present. 
The waters of the Dead Sea contain 200 to 260 parts of 
solid raatial in 1,000 parts (or 20 to 26 per cent.), including 
7 to 10 per cent. of common salt, the same proportion of 
magnesian salts, principally the chloride, 24 to 34 per cent. 
of calcium carbonate and sulphate, besides some bromides 
and alumina. ‘The density of these waters is owing to this 
large proportion of saline ingredients. The brine springs 
of New York and other States south and west, are well- 
known sources of salt (see under Common salt). Many of 
the springs afford bromine, and large quantities of it are 
manufactured for making photographic plates and for other 
purposes. 
Mineral waters vary much in constitution. They often 
contain iron in the state of bicarbonate, like those of Sara- 
toga and Ballstown, and are then called chalybeate waters, 
from the ancient name for iron or steel, chalybs, derived 
from the name of a country on the Baltic. Hydrogen sul- 
phide is often held in mineral waters and imparts to them 
its odor and taste; such are the so-called sulphur springs. 
Minute traces of salts of zinc, arsenic, lead, copper, an- 
timony and tin, have been found in some waters. What- 
ever is soluble in a region through which waters flow, will 
of course be taken up y by them, and many ingredients are 
soluble in minute proportions, which are usually described 
as insoluble. 
II. SILICA AND SILICATES. 
OPE iCx. 
Quartz. 
Rhombohedral. Occurs usually in six-sided prisms, more 
or less modified, terminated with six-sided pyramids : RAR 
=94° 15’. No cleavage apparent, seldom even in traces ; 
but sometimes obtained by heating the crystal and plunging 
it into cold water. Sometimes in coarse radiated forms; 
