124 THE CANADIAN NATURALIST. [April 



2*539. These hydrous alumino-magnesian silicates, which I have 

 included under the name of loganite,* are related to chlorite 

 and to pyrosclerite in composition ; but these last are distinguished 

 from it by their eminently foliated micaceous structure. 



When examined under the microscope, the loganite which re- 

 places the Eozo'on of Burgess, shows traces of cleavage-lines, which 

 indicate a crystalline structure. The grains of insoluble matter 

 found in the analysis, chiefly of quartz-sand, are distinctly seen as 

 foreign bodies imbedded in the mass, which is moreover marked by 

 lines apparently due to cracks formed by a shrinking of the silicate, 

 and subsequently filled by a further infiltration of the same ma- 

 terial. This arrangement resembles on a minute scale that of sep- 

 taria. Similar appearances are also observed in the serpentine which 

 replaces the Eozo'on of Grenville, and also in a massive serpentine 

 from Burgess, resembling this, and enclosing fragments of the fos- 

 sil. In both of these specimens also grains of mechanical impuri- 

 ties are detected by the microscope ; they are however rarer than 

 in the loganite of Burgess. 



From the above facts it may be concluded that the various sili- 

 cates which now constitute pyroxene, serpentine, and loganite were 

 directly deposited in waters in the midst of which the Eozo'on was 

 still growing, or had only recently perished ; and that these silicates 

 penetrated, enclosed, and preserved the calcareous structure pre- 

 cisely as carbonate of lime might have done. The association of 

 the silicates with the Eozo'on is only accidental ; and large quantities 

 of them, deposited at the same time, include no organic remains. 

 Thus, for example, there are found associated with the Eozoon- 

 limestones of Grenville, massive layers and concretions of pure ser- 

 pentine ; and a serpentine from Burgess has already been men- 

 tioned as containing only small broken fragments of the fossil. In 

 like manner large masses of white pyroxene, often surrounded by 

 serpentine, both of which are destitute of traces of organic struc- 

 ture, are found in the limestone at the Calumet. In some cases, 

 however, the crystallization of the pyroxene has given rise to con- 

 siderable cleavage-planes, and has thus obliterated the organic struc- 

 tures from masses which, judging from portions visible here and 

 there, appear to have been at one time penetrated by the calcareous 

 plates of Eozo'on. Small irregular veins of crystalline calcite, and 



* For a description of this and similar silicates, see Geology of Can- 

 ada, p. 491. 



