10 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Diatoms and perhaps Bacteria are the means of 

 producing various ferruginous deposits, such as bog iron 

 ore and laterite ; and plants, principally Mosses. Ferns 

 and Lycopods, have accumulated stores of peat and coal. 

 Petroleum and Elaterite we may regard as the product of 

 the animal and vegetable tissues entombed in the rocks. 



In dealing with the manner in which certain 

 materials are secreted by organisms there are one or two 

 general considerations which may assist us towards sound 

 conclusions. 



It has been commented upon on many occasions* that 

 the composition of ocean water in the earliest period of 

 the Earth's history must have been very different from 

 the present time. It was probably very poor in lime salts, 

 as the thickness of limestone deposits, compared with the 

 sedimentary rocks of a different composition, is very 

 small. 



\Vhen we review the various geological periods, from 

 the oldest formations to those now being laid down, it is 

 evident that there has been a progressive increase in the 

 extent and thickness of calcareous deposits, and probably 

 at no time in the Earth's history has the amount been 

 equal to that now in course of formation. 



T\ r e may regard the water of the primaeval ocean, in 

 the main, as the result of the condensation of water 

 formerly existing as vapour in the atmosphere. It would 

 thus be fairly pure, and the impurities now found in it 

 have come from the land by the agency of rivers. 



But when we contrast the composition of river water 

 with that of sea water, very striking differences arc .it 

 once noticed in the proportions of the various salts in 



*Lomas, Proc. L'pool Cleol. Soc. L898-9, p. 321. Macallum, 

 Trans. Canadian [nst., Vol. VII.. L902-3, p. 545, Forchhammer, 

 Brit. Assoc. Hep.. 1844, p. 153. 



