x The Hydrosphere 187 



the distribution of energy, acting as a great fly-wheel to the 

 world machine. Solar energy directly or indirectly is the 

 cause of all its movements. The sea carries nearly half of 

 the sun-heat falling in the tropical zone to higher latitudes, 

 and from the high latitudes of the south it tempers the 

 tropical climates of the western shores of the continents 

 by cold updraughts. By the solution and restoration of 

 carbonic acid, it helps to maintain the uniform composition 

 of the atmosphere, and by its comparatively slow changes 

 of temperature, it keeps up land and sea breezes and 

 monsoons. It is an unfailing reservoir for supplying water- 

 vapour to the atmosphere, and rain for the lakes and rivers. 

 The smooth and level surface of the ocearis allow the 

 normal system of atmospheric circulation ( 177) to be 

 developed to a far larger extent than is possible on the 

 land, and produces the steady winds which dominate the 

 climate of the whole globe. In the sea also the material 

 brought down by rivers from the land is redistributed and 

 worked up into new forms. 



REFERENCES 



1 J. Y. Buchanan, "On Ice and Brines," Proc. Roy. Soc. Ed. 

 xiv. 129 (1887) ; or Nature, xxxv. 608, and xxxvi. 9. 



2 H. R. Mill, "On the Physical Conditions of the Clyde Sea 

 Area," Proc. Phil. Soc. Glasgow, xviii. 332 (1887) ; or Nature, 

 xxxvi. 37, 56 (1887). Also Trans. Roy. Soc. Ed. (1891). 



3 H. R. Mill and T. M. Ritchie, "On the Physical Conditions 

 of Rivers entering a Tidal Sea," Proc. Roy. Soc. Ed. xiii. 460. 



4 H. R. Mill, "On the Salinity and Temperature of the Firth of 

 Forth," Proc. Roy. Soc. Ed. xiii. 29 (1885);* and xiii. 157; also 

 Nature, xxxi. 541 (1885) ; Scot. Geog. Mag. ii. 20. 



5 J. Murray, " Effects of Wind on Distribution of Temperature," 

 Scot. Geog. Mag. iv. 345 (1888). 



6 J. Y. Buchanan, " Physical Exploration of the Gulf of Guinea," 

 Scot. Geog. Mag. iv. 177, 233 (1888). "On Similarities in the 

 Physical Geography of the Great Oceans," Proc. Roy. Geog. Soc. 

 vu 'i- 753 (1886) ; also Nattire, xxxv. 33, 76. 



