4 MR GOODCHILD ON 
the river-waters derived from the land mingle with the 
waters of the sea. That this is the case, must be obvious 
to any one who has attentively considered the statements 
just made. The nature of this chemical change may be 
briefly described as the conversion of the soluble bicarbonate 
of lime into a solution of the sulphate. In this latter form 
lime-salts become widely diffused, and equalised in amount, 
throughout the oceanic areas; so that if an excess of either 
supply or demand arises at any part, the balance is presently 
made good by diffusion from the areas adjoining. One 
result of the chemical conversion just referred to is that 
much of the Carbonic Acid which formed the solvent of the 
bicarbonate of lime must be liberated at the zone where the 
conversion of the bicarbonate of lime into the sulphate takes 
place. Part of this newly-liberated gas must be carried by 
diffusion to other areas where rocks are undergoing much 
weathering, or where the drain upon the atmosphere, due to 
the growth of vegetation, is heavier than usual. But 
perhaps the rank growth of sea-weeds which characterises 
the outer part of the estuaries of so many rivers, may 
account for the refixation of a large part of the remainder. 
It must be obvious that if so large a quantity of lime is 
being continually poured into the ocean by the rivers of 
the globe, while the actual quantity in solution remains both 
small and constant in amount, that there must be some 
agency at work using up this lime as fast as it arrives. It 
is well known that the agent in question is, in the main, 
organic. Vast numbers of both animal- and vegetable- 
organisms are continually at work secreting lime-salts from 
a state of solution in sea-water, and fixing it in the solid 
form as part of their own structures. It is important to 
bear in mind that the organisms which are thus engaged in 
secreting lime from sea-water include representatives of the 
lower orders of plants (Nullipores and Corallines), as well 
as Protozoa, Hydrocorallines, Corals, Echinoderms, Polyzoa, 
Brachiopoda, Crustacea, and Mollusca. Of these the great 
majority live at the bottom of the water; but floating 
organisms, which live near the surface, also play a by no 
means unimportant part. Referring to these latter, Sir 
