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: 



NO. LOCALITY COLOR OP SEA APPEARANCE^ LUMINOUS 



1 Gibraltar Harbor Green Thick with fine particles 



2 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 Much less thick 



11 Bet\yeen Capes St. Mary and 



Vincent Deep indigo Very little matter, very pure 



12 Off the Buiiings Strong green Thick, with fine matter 



13 Beyond the Burlings Indigo Very little matter, pure 



14 Off Cape Finisterre Undecided Less pure 



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 



1 8 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 

 us 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. 



