446 
-In- short, it follows from this theory, that, 
other things being equal, the color of natural 
waters must be a function of the temperature ; 
and this conclusion is sustained by observation. 
One general exception, however, should be 
noted ; viz., that shallow water near shore is 
usually green, even in warm seas, on account 
of the large amount of foreign matter in sus- 
pension. This was very noticeable on the 
coast of Cuba; the sea being of a pure blue 
color to within a few rods of the beach, and 
then rapidly changing to green. When view- 
ing the coast from an elevated promontory, 
these colors were quite distinct to the eye for 
a distance of one to two miles along the 
shore. 
As affording additional confirmation of the 
theory, I offer the following notes on the colors 
of European waters, which were made during 
the summer of 1883, while travelling from Sicily 
to Throndhjem in Norway. I was not able to 
make corresponding observations of the tem- 
perature of the water; but this may be ap- 
proximately inferred, in most cases, from the 
latitude and season. 
April 14 to 16.— The Mediterranean, be- 
tween Stromboli and Sicily, is a decided blue, 
but not so deep and brilliant as the blue of the 
Gulf Stream and West-Indian waters. In the 
harbors of Messina and Catania the water is a 
brilliant green, inclining to blue. The color of 
the sea along the entire east coast of Sicily, 
from Messina to Syracuse, as viewed from 
the land, is blue, inclining to green. 
April 22 to 26. — The water about the Lipari 
Islands, and between them and Messina, is of 
a dark, intense blue. 
April 27.— The Bay of Naples is dark 
green, with scarcely a trace of blue. 
April 28. — The sea about Salerno, and be- 
tween that and Amalfi, as seen from the shore, 
is a beautiful blue-green, but sometimes pure 
bright green, and again, when deep, inclining 
strongly to blue. 
May 1.— The Bay of Naples, between 
Naples and Ischia, is a deep green, without a 
trace of blue. 
May 4.— The sea all about Capri and Sor- 
rento is a pure, deep, and beautiful blue. 
These shores are vertical walls of rock, which 
afford very little sediment to the water. Later 
in the summer, as many observers testify, the 
Pay of Naples is blue throughout. 
June 1 to 4.—The waters of the Italian 
lakes — Como, Lugano, and Maggiore — are 
a beautiful and distinct green. John Ball, 
F.R.S., in his ‘ Alpine guide,’ states that the 
southern end of Lake Maggiore is blue. I 
SCIENCE. 
[Von IIL, No. 62) 
found it almost as green as the northern: end: 
but it is probably blue in mid-summer ; and, if 
so, it must be regarded as a striking confirma 
tion of the theory. “ 
June and July. — The Swiss lakes | are: gen- 
erally bright green and somewhat: opaque. 
Lake Geneva, however, as is well known, is a 
lovely blue, resembling the sea about Sicily ; 
but toward the upper end it seemed to be 
slightly greenish. The other Swiss lakes de- 
rive their waters from regions that are large- 
ly composed of limestone, and hence these 
waters are saturated with carbonate of calcium. 
But the Rhone, which is the principal tributary 
of Lake Geneva, drains a region of metamor-~ 
phic rocks containing but little limestone. 
Aug.,2.— The Baltic, between Stralsund 
and Copenhagen, is dull green. | ) 
Aug. 3 to 4. — The color of the Cattegat is 
dull green, without a trace of blue. 
Aug. 7 to 23. — Between Christiansand and 
Throndhjem the open sea and the lower parts 
of the fiords have a deep, dark green color, 
with scarcely ever a suspicion of blue. As we 
ascend the fiords, the color becomes a lighter 
green, and more vivid and opaque, in propor- 
tion as the water becomes fresher. The heads 
of the fiords and the adjacent lakes are usually 
indistinguishable in color from the Swiss lakes ; 
but the beautiful Ringedalsvand, lying between 
the head of the Hardanger Fiord and the cele- 
brated Ringedalsfos, at an altitude of fifteen 
hundred feet, is a notable exception. This 
lake is deep blue except near the shore, where 
it is greenish blue; and the streams flowing 
into it, as well as that flowing out, are nearly 
pure blue. The rule that cold water is green 
does not hold in this case, but the exception 
is readily explained as due to the unusual 
purity of the water. The lake is bounded on 
all sides by cliffs of granitoid gneiss, and where 
there is a talus at the bottom it is usually des- 
titute of soil. Above the cliffs are immense 
fields of snow, whence the water of the lake 
is derived. None of the tributary streams flow 
from glaciers; but they are all limpid snow- 
water flowing down over hard rocks, which are 
alike destitute of soil or material which could 
be carried away in suspension in the water, 
and of limestone or other materials capable 
of being dissolved in the water. It would 
probably be difficult to find any considerable 
body of natural water which is more nearly a 
pure distilled water than this. And we may 
fairly say, that, on account of its remarkable 
purity, it is blue, in spite of its low ton 
ture. 
| ma i Crossy. 
