VOYAGE TO ALGERIA. 127 
opinion, scatter no light at all. The track of a luminous 
beam could not be seen in such water. But "an amount 
of impurity so infinitesimal as to be scarcely expressible in 
numbers, and the individual particles of which are so small 
as wholly to elude the microscope, may, when examined by 
the method alluded to, produce not only sensible, but strik- 
ing effects upon the eye." 
The result of the examination of nineteen bottles filled 
at various places between Gibraltar and Spithead, are 
here tabulated: 
1 Gibraltar Harbor Green Thick with fine particles 
a Two miles from Gibraltar .... Clearer green Thick with very fine particles 
3 Off Cabreta Point Bright green Still thick, but less so 
4 Off Cabreta Point Black-indigo Much less thick, very pure 
5 Off Tarifa Undecided Thicker than No. 4 
6 Beyond Tarifa Cobalt-blue Much purer than No. 5 
7 Twelve miles from Cadiz Yellow-green Very thick 
8 Cadiz Harbor Yellow-green Exceedingly thick 
9 Fourteen miles from Cadiz. . .Yellow-green. . . .Thick, but less so 
10 Fourteen miles from Cadiz. . Bright green.. 
11 Between Capes St. Mary and 
Vincent Deep indigo. . 
12 Off the Burlings Strong green . 
" Beyond the Burlings Indigo 
..Much less thick 
. .Very little matter, very pure 
. .Thick, with fine matter 
. .Very little matter, pure 
pill' 
litt 
14 Off Cape Finisterre Undecided. . . . 
15 Bay of Biscay Black-indigo . . . .Very little matter, very pure 
16 Bay of Biscay Indigo Very fine matter. Iridescent 
17 Off Ushant Dark green A good deal of matter 
18 Off St. Catherine's Yellow-green Exceedingly thick 
19 Spithead Green Exceedingly thick 
Here we have three specimens of water, described as 
green, a clearer green, and bright green, taken in Gibraltar 
harbor, at a point two miles from the harbor, and off 
Cabreta Point. The home examination showed the first 
to be thick with suspended matter, the second less thick, 
and the third still less thick. Thus the green brightened 
as the suspended matter diminished in amount. 
Previous to the fourth observation our excellent navigat- 
ing lieutenant, Mr. Brown, steered along the coast, thus 
avoiding the adverse current which sets in, through the 
strait, from the Atlantic to the Mediterranean. He was at 
length forced to cross the boundary of the Atlantic current, 
which was defined with extraordinary sharpness. On the 
one side of it the water was a vivid green, on the other a 
deep blue. Standing at the bow of the ship, a bottle 'could 
be filled with blue water, while at the same moment a 
bottle cast from the stern could be filled with green water. 
