116 MR. A. W. WATERS ON A CHANGE IN 



each square mile, we get about 5000 million tons removed 

 from the land-surface each year, so that in ten years a 

 weight equal to that o£ Vesuvius"^ is removed from the 

 land to the oceanic area by this means. 



If an equal amount were removed from each latitude, and 

 the deposition were also regular, it could never have any 

 effect; but the deposition takes place most irregularly, 

 since, from the northern hemisphere, with about 37,000,000 

 square miles, 3700 million tons will be removed per annum, 

 while from the southern hemisphere only about 1300 

 million tons ; and, dividing the amount to be deposited pro- 

 portionally in the water-area, the north gets 2073 million 

 tons, and the south 2935 million tons. Now if we suppose 

 there is no subsidence, and allowing for the difference be- 

 tween sp. gr. of solid matter in solution and water, we still 

 get a difference of 863 million tons ; and this added to the 

 2400 million tons surplus removed from the north gives a 

 gain for the southern hemisphere of 3230 million tons over 

 the northern, or one Vesuvius in fifteen years. 



But it is not at all the case that the matter will be de- 

 posited equally over the water-area ; for it will be abstracted 

 much more rapidly in the warmer zones, especially the 

 tropical, as it is the warm waters that teem the most with 

 animal life. Here it is that the coral grows, and here and 

 in the temperate region that the Lithothamnium and other 

 calcareous sea-weeds of the group of the Melobesiacea grow 

 and have formed such massive deposits in the Tertiary 

 period ; and the Bryozoa and Testacea also here occur in 

 greatest abundance. 



If we look at the map of the world or a globe, we shall 

 find that the area, as bearing on this subject, from which 

 most weight will be removed will be that of the Asiatic 

 continent ; and on the other hand the locality where the 



* Mallet, " On Volcanic Energy," Trans. Eojal Soc. 



