46 ANNUAL ADDRESS, MDCCCLXXIII. 



greater than is required to hold the carbonate of lime in 

 solution, and says that even if a temporary precipita- 

 tion took place it would almost immediately be redissolved 

 by this free carbonic acid. He also says it is only through 

 organic or life agency that carbonate of lime can be se- 

 creted from sea water. 



To this ought to be added the testimony of Mr. Hull 

 from his paper previously quoted. He is a believer in 

 the organic origin of limestone, as will be seen from the 

 following interesting table, which he terms " a synopsis of 

 the chief limestone builders of successive geologic periods 

 in ascending order " : 



LAURENTIAN. Foraminifera (?). Eozoon. 



SILURIAN and DEVONIAN. Corals, chiefly of the orders Zoantharia tabu- 



lata, and 2. rugosa of MM. Milne- Edwards 

 and Haime), Crinoids, Brachiopods, and 

 Entomostraca. 



CARBONIFEROUS Corals, (Zoantharia tdbulata, Z. rugosa, Z. 



tabulosa), Crinoids, Bryozoa, Brachiopods, 

 and Entomostraca. 



PERMIAN Corals (not abundant; Zoantliaria tabulata, Z. 



rugosa,} Bryozoa, Conchifera, Entomostraca. 



TRIASSIC Bryozoa, Echinoderms, Conchifera. 



JURASSIC Corals (Zoantharia aporosa), Bryozoa, Echino- 

 derms, Molluscs largely. 



CRETACEOUS Amorphozoa, Foraminifera, Corals (Zoantharia 



aporosa, Z. tabulata, Z. rugosa), Echinoidae, 

 Bryozoa, Entomostraca, Brachiopods, (Tere- 

 bratulse). 



TERTIARY Foraminifera, (Nummulites), Corals (Zoantharia 



aporosa, Z. perforata, Z. tubulata), Echi- 

 noderms, (Echinoidfz, Asteroidce), and 

 Ophiuridas. 



Although I have been searching for facts without pre- 

 judice, the wish was almost father to the thought that I 



