RELATIONS TO OTHER SCIENCES 689 



cyclonic areas, the prevailing winds, and the greatly diversified 

 climates in different parts of the world. The aqueo-aerial currents 

 from sea to land, and the oceanic currents thus brought about by 

 changes of temperature in the atmosphere, are the great equalizers 

 of temperature in diverse regions; for instance, except for these 

 currents the mean winter temperature of London would be 17 F. 

 in place of 39 F., London thus being benefited 22 F., while the 

 Shetland Islands to the north of Scotland are benefited 36 F. by 

 the Gulf Stream and the aqueo-aerial currents due to the winds 

 from the southwest. 



At the surface of the earth, both on land and on sea, bands of 

 equal temperature run more or less parallel to the equator. This is 

 true, notwithstanding the fact that oceanic currents cause wide 

 deflections, as, for instance, in the case of the Gulf Stream: on the 

 sea-floor the bands of equal temperature run north and south along 

 the continental shores. 



The extreme range of temperature in the surface waters of the 

 ocean is from 28 to 95 F., and 84 per cent of the surface waters 

 have a temperature exceeding 40 F. There is a circum-tropical 

 zone where there is a high temperature and small range not exceeding 

 10 F., which embraces most of the coral-reef regions of the world, and 

 there are two circum-polar zones where there is a low temperature 

 and small range not exceeding 10 F., where carbonate -of -lime 

 secreting organisms are poorly developed. Between these two polar 

 zones and the circum-tropical zone are two intermediate zones where 

 there is a wide range of temperature. It is in these intermediate 

 zones that warm currents occupy the surface at one season of the 

 year and cold currents at another season, and here there is a con- 

 sequent great destruction of marine life. This gives us some indica- 

 tion of the conditions under which phosphatic and glauconitic 

 deposits were laid down in past ages. 



Many areas at the surface of the ocean used formerly to be re- 

 garded as barren and devoid of life, but there are no such barren 

 regions. The whole surface of the ocean both in cold and warm 

 waters, and down to a depth of 600 feet must be regarded as a 

 vast meadow, more extensive and more important than the vege- 

 table covering on land-surfaces. Everywhere there are myriads of 

 Diatoms, calcareous and other microscopic Algae with a red-brown 

 color, the chlorophyll in which is ever busy under the influence of the 

 sun's rays converting inorganic into organic compounds. These 

 minute organisms are the original source of food for the vast ma- 

 jority of marine animals both in the surface waters and on the floor 

 of the ocean, even at the greatest depths. The reserve food of these 

 minute organisms is little globules of oil, instead of granules of 



