Page 21 - 1915, Springs of CA.

NATURAL WATEES. 21

of the pool. If the basin is funnel-shaped * * * with flaring or saucer-shaped
expansion, algse grow in the cooler and shallower water of the margin, forming con-
centric rings of yellow, old gold and orange, shading into salmon-red and crimson,
and this to brown at the border of the spring. Around such springs the growth at
the margin often forms a raised rim of spongy, stiff jelly, sometimes almost rubber-like
in consistency, and red or brown in color.
Crenothrix is a small filamentous plant that has a gelatinous sheath
colored by ferric oxide. It grows especially in ground waters that
contain considerable iron, and is probably the brown flocculent
material that is found in some iron springs. It sometimes causes
rusty stains on clothing, and when excessive it may clog faucets and
pipes.
Sulphuraria is a slender green plant that secretes silica and grows in
sulphur waters that have a temperature of less than 122°.
DEGREE OP CONCENTRATION OP NATURAL WATERS.
It is probable that none of the several ways of reporting water
analyses conveys to the nontechnical person a clear idea how much
solid matter is present in solution. The amount of any constituent
stated in parts per million indicates the proportion, by weight, of the
amount of that constituent to the solution. For instance, if the
amount of calcium radicle is stated as 210 parts per million it is to be
inferred that each million pounds of the natural water contains 210
pounds of the calcium radicle. To correlate this form of expression
with better known values, it may be stated that one heaping tea-
spoonful of a substance dissolved in one gallon of water represents
approximately 4,000 parts per million; a rounding teaspoonful, about
2,500 parts; a thimbleful, about 600 parts; and the amount that can
be held on the point of a penknife, 10 to 20 parts. The minimum
amount of solid material in solution that is perceptible to the taste
varies greatly with the material, and to a less degree but notably with
the individual. Experiments on taste sensitiveness have been made
by Whipple,1 and from his tables and from summaries by Dole 2 it
appears that as small amounts as 2 or 3 parts per million of iron are
distinctly perceptible to some people, while several times as much
aluminum is barely so. The alkalies and alkaline earths are much less
readily detected by the taste. About 200 parts per million of calcium
and magnesium render a water noticeably "hard;" but it seems
probable that the negative radicles (chloride, carbonate, and sul-
phate), rather than the positive ones, give the distinctive tastes to
most mineral waters. About 250 parts per million of chloride renders
a water distinctly "salty." Of the dissolved gases which occur in
1 Whipple, G. C., The value of pure water, pp. 65-67, Wiley & Sons, New York, 1907.
2 Capps, S. R., Ground waters of north-central Indiana: U. S. Geol. Survey Water-Supply Paper 254,
pp. 237-239,1910.