§ 747. TIDE-RIPS AND SEA DRIFT. 401 



in blackness, and the stars going out, seemed to indicate that all 

 nature was preparing for that last grand conflagration which we 

 are taught to believe is to annihilate this material world. After 

 passing through the patch, we noticed that the sky, for four or 

 five degrees above the horizon, was considerably illuminated, 

 something like a faint aurora borealis. We soon passed out of 

 sight of the whole concern, and had a fine night, without any con- 

 flagration (except of midnight oil in trying to find out what was 

 in the water). I send you this because I believe you request your 

 corps of ' one thousand assistants' to furnish you with all such 

 items, and I trust it will be acceptable. But as to its furnishing 

 you with much, if any, information relative to the insects or ani- 

 mals that inhabit the mighty deep, time will only tell ; I can not 

 think it will." 



747. These discolorations are no doubt caused by organisms 

 's^^lence the Red Sea ^f the sca, but whcthcr wholly animal or wholly 

 derives it3 name. vegetable, or whether sometimes the one and some- 

 times the other, has not been satisfactorily ascertained. I have 

 had specimens of the coloring matter sent to me from the pink- 

 stained patches of the sea. They were animalculaB well defined. 

 The tints which have given to the Eed Sea its name may per- 

 haps be in some measure due to agencies similar to those which, 

 in the salt-makers' ponds, give a reddish cast (§ 71) to the brine 

 just before it reaches that point of concentration when crystalli- 

 zation is to commence. Some microscopists maintain that this 

 tinge is imparted by the shells and other remains of infusoria 

 which have perished in the growing saltness of the water. The 

 Red Sea may be regarded, in a certain light, as the scene of nat- 

 ural salt-works on a grand scale. The process is by solar evap- 

 oration. No rains interfere, for that sea (§ 876) is in a riverless 

 district, and the evaporation goes on unceasingly, day and night, 

 the year round. The shores are lined with incrustations of salt, 

 and the same causes which tinge with red (§ 71) the brine in the 

 vats of the salt-makers probably impart a like hue to the arms and 

 ponds along the shore of this sea. Quantities, also, of slimy, red 

 coloring matter are, at certain seasons of the year, washed up 

 along the shores of the Red Sea, which Dr. Ehrenberg, after an 

 examination under the microscope, pronounces to be a very deli- 

 cate kind of sea- weed : from this matter that sea derives its name. 



Co 



