in the Air and in the Sea. 37 



with river-mouths, the upper current in the channel of discharge 

 will flow outwards, while an undercurrent of constantly salt 

 water must flow inwards. But in seas where the evaporation 

 exceeds the influx (for example, in the Mediterranean and the 

 Red Sea), the upper current must flow in through the channel, 

 and the undercurrent carry out the superfluous salt. An 

 extremely interesting example of this sort is presented by the 

 Gulf of Karabughaz, which is connected with the Caspian by a 

 very flat channel of only a few feet depth. As the evaporation 

 from the very spacious surface of the gulf, into which no streams 

 flow, is very great, especially in summer, water is perpetually 

 flowing in from the Caspian with a velocity that sometimes rises 

 to 6 knots an hour. Of course this current brings much salt 

 into the gulf, from which it cannot get out again, because the 

 channel is too shallow to permit an outflow beneath. The salt 

 thus accumulating is deposited in crystals on the bottom ; and 

 thus the Gulf of Karabughaz plays the part of a saltpan conti- 

 nually withdrawing salt from the Caspian Sea. If in the course 

 of time the sand washed in by the waves should completely 

 block up the shallow strait which joins the gulf to the sea (which 

 would long since have happened if the current were not so 

 strong), Karabughaz as a lake would soon evaporate completely 

 and leave behind a basin of solid salt, such as we see in the 

 Elton- See and in Uetzkaja Saschtschita as formations of pri- 

 meval times. 



If in any part of the ocean animal life be developed in greater 

 abundance than in others, the excessive abstraction of salt or 

 lime from the water by the animals will also give rise to slight 

 movements of the water. Although such movements could 

 scarcely be called a current, it cannot be doubted that such must 

 take place in the deepest seas even at the bottom, because other- 

 wise no life would be possible there ; for among the animals 

 living in the depths there are creatures that cannot change their 

 place ; nourishment must consequently be brought to them by 

 currents. 



The theory of perfect stillness in the bottom waters of the 

 sea * is therefore, like the theories of Ross and Forbes, to be 

 regarded as incorrect. 



We have thus examined all the causes which affect the specific 

 gravity of sea-water and the air, and come to the conclusion tint 

 differences of temperature and in the saltness of the water of the 

 sea assist only in a slight degree in maintaining the great ocean- 

 currents and the trade- winds, but cannot possibly produce them j 



* Miihry says, " At the bottom of the ocean we must assume that there 

 is almost complete stillness." — Lehre iiber die Meeres-Stromungen , p. 5. 



