CARBONIC ACID CONTAINED IN SEA-WATER. 125 



to the vegetation those salts necessary to its ex- 

 istence. This is the origin of the salts found in the 

 ashes of plants, in those cases where the soil could 

 not have yielded them. 



In a comprehensive view of the phenomena of 

 nature, we have no scale for that which we are 

 accustomed to name, small or great ; all our ideas 

 are proportioned to what we see around us, but how 

 insignificant are they in comparison with the whole 

 mass of the globe ! that which is scarcely observable 

 in a confined district appears inconceivably large 

 when regarded in its extension through unlimited 

 space. The atmosphere contains only a thousandth 

 part of its weight of carbonic acid ; and yet small 

 as this proportion appears, it is quite sufficient to 

 supply the whole of the present generation of living 

 beings with carbon for a thousand years, even if it 

 were not renewed. Sea-water contains ^^loo of its 

 weight of carbonate of lime; and this quantity, 

 although scarcely appreciable in a pound, is the 

 source from which myriads of marine mollusca and 

 corals are supplied with materials for their habita- 

 tions. 



Whilst the air contains only from 4 to 6 ten-thou- 

 sandth parts of its volume of carbonic acid, sea- 

 water contains 100 times more, (10,000 volumes of 

 sea-w^ater contain 620 volumes of carbonic acid — 

 Laurent, Bouillon, Lagrange). Ammonia* is also 

 found in this water, so that the same conditions 

 which sustain living beings on the land are combined 

 in this medium, in which a whole world of other 

 plants and animals exists. 



The roots of plants are constantly engaged in 

 collecting from the rain those alkalies which formed 

 part of the sea-water, and also those of the water 

 of springs, which penetrates the soil. Without 

 alkalies and alkaline bases most plants could not 



* When the solid saline residue obtained by the evaporation of sea- 

 water is heated in a retort to redness, a sublimate of sal-ammoniac is 

 obtained. — Marcet. 



11* 



