308 
GEOLOGY OF NORTH CAROLINA. 
No. 6 is a well at Thorn asville, (of Mr. Thomas). This is notable a6 
containing a grain of phosphoric acid to the gallon. The analysis also 
showed minute quantities of nitric acid and of the sulphides. The 
presence of these substances furnishes ground of suspicion of contamina- 
tion. 
No. 7 is from Warrenton, analyzed at the request of the mayor. It is 
a sulphur water, otherwise very pure, containing only four grains of solid 
matter to the gallon. 
It will be observed that the amount of solid matter does not reach 
twenty grains in any of these samples, all of which are popularly con- 
sidered mineral waters. But an ordinary potable water may, and often 
does, contain even more than that amount. Some of the wells of Raleigh 
contain much more. A few examples will show the range of solid mat- 
ters in drinkable waters, in grains per gallon : 
Cochituate, Boston,, 3.11 
Croton, New York,...., 4.78 
Ridgewood, Brooklyn, 3.92 
Fairmount, Philadelphia, 3.50 
Lake Michigan, Chicago, 6.68 
Genesee River, Rochester, 13.25 
Thames, London, 18.50 
Kent, “ 26.50 
Seine, Paris, 8. S3 
Rhine, Basle, 11.80 
Loch Katrine, Glasgow, 2.30 
Distilled Water, 0.10 
Absolutely pure water is unknown, outside of the laboratory of the 
chemist. 
No spring, or well, or lake water is pure. And it is generally consid- 
ered that a certain (small) per centage of mineral matter improves not 
only the taste, but the wholesomeness, of drinking water. Lime carbon- 
ate, one of the most common impurities, does not impair its healthfulness, 
until the quantity passes twelve or fifteen grains, but sulphate of lime, 
magnesia salts, and whatever communicates permanent hardness to 
waters, are reckoned injurious, even when existing in small proportions. 
Organic matter is commonly set down as injurious, if found in quantities 
above one grain to the gallon. 
But whether a larger proportion is hurtful, depends altogether on the 
nature and (especially) the source of it. If derived from the putrid de- 
