242 THE PHYSICAL GEOGRAPHY OF THE SEA. 



gions of the tropics. Whatever is beautiful, wondrous, or uncom- 

 mon in the great classes of fish and Echinoderms, jelly-fishes and 

 polypes, and the molluscs of all kinds, is crowded into the warm 

 and crystal waters of the tropical ocean — rests in the white sands, 

 clothes the rough clifis, clings, where the room is already occupied, 

 like a parasite, upon the first comers, or swims through the shal- 

 lows and depths of the elements — while the mass of the vegeta- 

 tion is of a far inferior magnitude. It is peculiar in relation to 

 this, that the law valid on land, according to which the animal 

 kingdom, being better adapted to accommodate itself to outward 

 circumstances, has a greater diffusion than the vegetable king- 

 dom ; for the Polar seas swarm with whales, seals, sea-birds, fish- 

 es, and countless numbers of the lower animals, even where every 

 trace of vegetation has long vanished in the eternally frozen ice, 

 and the cooled sea fosters no sea-weed — that this law, I say, holds 

 good also for the sea, in the direction of its depth ; for when we 

 descend, vegetable life vanishes much sooner than the animal, and, 

 even from the depths to which no ray of light is capable of pene- 

 trating, the sounding-lead brings up news at least of living infu- 

 soria." — Schleiden's Lectures^ p. 403-406. 



676. Until the commencement of the plan of deep-sea sound- 

 ings, as now conducted in the American Navy, the bottom of what 

 the sailors call " blue water" was as unknown to us as is the in- 

 terior of any of the planets of our system. Koss and Dupetit 

 Thouars, with other officers of the English, French, and Dutch na- 

 vies, had attempted to fathom the deep sea, some with silk threads, 

 some with spun-yarn (coarse hemp threads twisted together), and 

 some with the common lead and line of navigation. All of these 

 attempts were made upon the supposition that when the lead 

 reached the bottom, either a shock would be felt, or the line, be- 

 coming slack, would cease to run out. 



677. The series of systematic experiments recently made upon 

 this subject shows that there is no reliance to be placed on such 

 a supposition, for the shock caused by striking bottom can not be 

 communicated through very great depths. Furthermore, the lights 

 of experience show tliat, as a general rule, the under currents of 

 the deep sea have force enough to take the line out long after the 



