PHYSICAL GEOGBAPHY. 309 



diation, and which remain nearer to the surface, owing to the 

 hinderance placed in the way of their greater descent by the 

 intervention of sand-hanks. By his observations Franklin may 

 be eaid to have converted the thermometer into a sounding 

 line. Mists are frequently found to rest over these depths, ow- 

 ing to the condensation of the vapor of the atmosphere by the 

 cooled waters. I have seen such mists in the south of Jamai- 

 ca, and also in the Pacific, defining with sharpness and clear- 

 ness the form of the shoals below them, appearing to the eye 

 as the aerial reflection of the bottom of the sea. A still more 

 striking effect of the cooling produced by shoals is manifested 

 in the higher strata of air, in a somewhat analogous manner 

 to that observed in the case of flat coral reefs, or sand islands. 

 In the open sea, far from the land, and when the air is calm, 

 clouds are often observed to rest over the spots where shoals 

 are situated, and their bearing may then be taken by the com- 

 pass in the same manner as that of a high mountain or isola- 

 ted peak. 



Although the surface of the ocean is less rich in living forms 

 than that of continents, it is not improbable that, on a further 

 investigation of its depths, its interior may be found to possess 

 a greater richness of organic life than any other portion of our 

 planet. Charles Darwin, in the agreeable narrative of his ex- 

 tensive voyages, justly remarks that our forests do not conceal 

 so many animals as the low woody regions of the ocean, where 

 the sea- weed, rooted to the bottom of the shoals, and the sev 

 ered branches of fuci, loosened by the force of the waves and 

 currents, and swimming free, tmibld their delicate foliage, up- 

 borne by air-cells.* The application of the microscope increas- 

 es, in the most striking manner, our impression of the rich lux- 

 uriance of animal life in the ocean, and reveals to the aston- 

 ished senses a consciousness of the universality of life. In the 

 oceanic depths, far exceeding the height of our loftiest mount- 

 ain chains, every stratum of water is animated with polygas- 

 tric sea- worms, Cyclidiae, and Ophrydina;. The waters swarm 

 with countless hosts of small luminiferous animalcules, Mam- 

 maria(of the order of Acalephae), Crustacea, Peridinea, and cir- 

 cling Nereides, which, when attracted to the surface by peculiar 

 meteorological conditions, convert every wave into a foaming 

 band of flashing light. 



* [See Structure and Distribution of Coral Reefs,\>y Charles Darwin, 

 London, 1842. Also, Narrative of the Surveying Voyage of H.M.S. 

 " Fly," in the Eastern Archipelago, during the Years 1842-184G, by J 

 B Tukes, Naturalist to the expedition, 1817.] Tr. 



