92 On Similarities in the 



annual temperature downwards, and the energy with which 

 this takes place depends on the excess of salinity of the surface 

 waters over that of the waters beneath, and on the range of 

 daily and especially annual temperature. The greater the 

 range of salinity and of surface temperature, the greater will 

 be the oscillation produced, and the deeper will its effect 

 be felt. Thus in the North Atlantic everything conspires to 

 collect heat and propagate it downwards, and as a con- 

 sequence we find a higher temperature at 1000 fathoms in 

 the Sargasso Sea than in any other part of the globe. In the 

 North Pacific the range of density is small, and the subsurface 

 water is comparatively cold. 



In passing over the surface of the ocean, the winds not 

 only remove water in the form of vapour, they also impart 

 motion to the water immediately under their influence. The 

 effect of this is to produce a general motion of the denser 

 intertropical water towards the equator and towards the west, 

 which is intensified near the equator and forms the well- 

 known westerly equatorial current. 



In the Atlantic the westerly running waters are collected 

 in the western sinus of the ocean, and the head of water thus 

 produced is relieved by the overflow of the Gulf Stream. In 

 the Pacific the westerly running waters meet no continental 

 obstacle, and pass freely into the eastern waters of the Indian 

 Ocean, subject to a partial reversal during the season of the 

 south-west monsoon. 



Everything conspires to produce an exaggerated heating 

 effect in the waters of the western portion of an intertropical 

 ocean. It is supplied with water which has already been heated 

 further to the eastward, and this water, in virtue of its density, 

 has the property of propagating the high temperature to greater 

 depths. A secondary consequence of a leeward position in the 

 ocean, due to this characteristic of such waters, is the presence 

 of coral formations in the western regions of the Atlantic and 

 Pacific, and, owing to the mixture of conditions, in both the 

 eastern and western regions of the Indian Ocean. 



Continental homologies, or similar features in corresponding 

 localities, are found on the western as well as on the eastern 



