128 FKAGMKNTS 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 

 in-digo. 



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 

 than the green. We approach Cadiz, and at twelve miles 

 from the city get into yellow-green water; this the London 

 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 borne 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, 



