128 FRAGMENTS OF SCIENCE. 
Two bottles were secured, one on each side of this remark- 
able boundary. In the distance the Atlantic had the hue 
called ultra-marine; but looked fairly down upon, it was 
of almost inky blackness black qualified by a trace of 
indigo. 
What change does the home examination here reveal? 
In passing to indigo, the water becomes suddenly augmented 
in purity, the suspended matter becoming suddenly less. 
Off Tarifa, the deep indigo disappears, and the sea is un- 
decided in color. Accompanying this change, we have a 
rise in the quantity of suspended matter. Beyond Tarifa, 
we change to cobalt-blue, the suspended matter falling at 
the same time in quantity. This water is distinctly purer 
i. We approach 
from the city get into yellow-green water; this the London 
than the green. We approach Cadiz, and at twelve miles 
examination shows to be thick with suspended matter. 
The same is true of Cadiz harbor, and also of a point 
fourteen miles from Cadiz in the homeward direction. 
Here there is a sudden change from yellow-green to a 
bright emerald-green, and accompanying the change 
a sudden fall in the quantity of suspended matter. 
Between Cape St. Mary and Cape St. Vincent the 
water changes to the deepest indigo, a further diminution 
of the suspended matter being the concomitant phenom- 
enon. 
We now reach the remarkable group of rocks called the 
Burlings, and find the water between the shore and the 
rocks a strong green; the home examination shows it to be 
thick with fine matter. Fifteen or twenty miles beyond 
the Burlings we come again into indigo water, from which 
the suspended matter has in great part disappeared. Off 
Cape Finisterre, about the place where the Captain went 
down, the water becomes green, and the home examination 
pronounces it to be thicker. Then we enter the bay of 
Biscay, where the indigo resumes its power, and where the 
home examination shows the greatly augmented purity of 
the water. A second specimen of water, taken from the 
bay of Biscay, held in suspension fine particles of a peculiar 
kind; the size of them was such as to render the water 
richly iridescent. It showed itself green, blue, or salmon- 
colored, according to the direction of the line of vision. 
Finally, we come to our last two bottles, the one taken 
opposite St. Catherine's lighthouse, in the Isle of Wight, 
