30 FISHERIES OF THE NORTH SEA 



the surface. These minute organisms mul- 

 tiply so greatly and with , such rapidity, 

 that they form a constant source of food 

 supply for the millions of small fry. Every- 

 where are forms of life so minute as to be 

 invisible to the naked eye, but in such 

 quantities that, if a square mile of the 

 North Sea water could be properly 

 filtered, these invisible microscopic live 

 substances would by their remains supply 

 several tons of lime. In addition, there are 

 incalculable millions of white-fish eggs in 

 the surface waters, the eggs of the herring 

 and larvae of all kinds on the bottom, 

 and almost all forms of marine flora in 

 abundance. 



We have just seen how nature transforms 

 the barren rocks of the earth into soil 

 suitable for growing all the food that man 

 requires. -This process is continued under 

 the sea. The soil brought down by the 

 rivers and eroded by the tides is carried 

 in suspension and spread over the sub- 

 marine bottom. The temperature and 

 salinity of the water, which are agents in 

 circulating the currents, act beneficially on 

 the soil. Plants spring up and in their 



