﻿Animal Nature of Eozobn Canadense. (jr> 



cess of concentration by evaporation under the solar heat. 

 Klement has more recently taken up this fact in the way 

 of experiment, and finds that, while in the case of ordi- 

 nary calcite this action is slow and imperfect, with the 

 arasonite which constitutes the calcareous framework of 

 certain corals, and at temperatures of 60° or over, it is 

 very rapid and complete, producing a mixture of calcium 

 and magnesium carbonates, from which a pure dolomite 

 more or less mixed with calcite may subsequently result.^ 



I regard these observations as of the utmost importance 

 in reference to the relations of dolomite with fossiliferous 

 limestones, and especially with those of the Grenville 

 Series. The waters of the Laurentian ocean must have 

 been much richer in salts of magnesium than those of the 

 present seas, and the temperature was probably higher, 

 so that chemical changes now proceeding in limited 

 lagoons might have occurred over much larger areas. If 

 at that time there were, as in later periods, calcareous 

 organisms composed of aragonite, these may have been 

 destroyed by conversion into dolomite, while others more 

 resisting were preserved, just as a modern Polytrema or 

 Balaniis might remain, when a coral to which it might be 

 attached would be dolomitized. This would account for 

 the persistence of Eozoon and its fragments, when other 

 organisms may have perished, and also for the frequent 

 filling of the canals and tubuli with the magnesian car- 

 bonate. 



The question now arises as to the mineralization of 

 Eozoon with serpentine, and more rarely, especially in the 

 case of its larger and lower chambers, with pyroxene. 

 Connected with this is the alternation, as above described^ 

 of serpentinous and dolomitic layers in the limestone, as 

 if in successive times the conditions were alternately 

 favourable to the deposition of magnesium in the form of 

 carbonate and in that of silicate. 



1 Bulletin Geol. Soc. Belgium, Vol. IX. (1895, p. 3). Also notice"_iii Geol. Mag., 

 July, 1895, p. 329. 



5 



