72 J. W. DAWSON ON THE OCCTTKKENCE OP 



advocated by Messrs. Bowney and King, may be dismissed at once. 

 Independently of the insuperable chemical difficulties which have 

 been pointed out by Dr. Hunt*, and which he proposes to discuss 

 more fully in his papers on Chemical Geology, now in the press, we 

 have the further facts that no replacement of serpentine by calcite 

 is indicated by the relations of these minerals to each other, while 

 such replacement as does occur is in the other direction, or the change 

 of calcite into serpentine, as evidenced by the state of preservation 

 of some specimens of Eozoon, above referred to. Further, this 

 theory fails to give any explanation of the specimens mineralized 

 by pyroxene, dolomite, and calcite, or to account for the nummuline 

 wall, except by attributing it to the alteration of chrysotile, which 

 is inadmissible, as the veins of this mineral are newer than the 

 walls supposed to have been derived from them. 



2. Inasmuch as many apparently concretionary grains and lenti- 

 cular masses of serpentine exist in the Laurentian limestones, it 

 may be supposed possible that Eozoon is merely a modification of 

 these concretionary forms. In this case, the filling of each lamina 

 and chamberlet of Eozoon must be regarded as a separate concretion ; 

 and even if we could suppose some special cause to give regularity 

 and uniformity to such concretions in some places and not in others, 

 we still have unaccounted for the canals and tubuli, or the delicate 

 threads of serpentine representing them. Further, we have to sup- 

 pose that a tendency to this regular and complicated arrangement 

 has affected in the same way minerals so diverse as serpentine, 

 loganite, pyroxene, and dolomite. 



3. The only remaining theory is that of infiltration by serpentine 

 of cavities previously existing in the calcite. There is no chemical 

 objection to this, inasmuch as we know of the infiltration of fossils 

 in other formations by minerals akin to serpentine; and in these 

 limestones the veins of fibrous serpentine have evidently been intro- 

 duced by aqueous action subsequently to the production or fossiliza- 

 tion of the Eozoon. Further, the white pyroxene of the Laurentian 

 limestones, and the loganite and dolomite, are all known to have 

 been produced by aqueous deposition. The only question remaining 

 is, Whence came the original calcite skeleton with laminas, chambers, 

 canals, and tubuli to be so infiltrated? The answer is given in the 

 comparison with the tests of Foraminifera, originally proposed by 

 the writer, and illustrated in so conclusive a manner by the re- 

 searches of Dr. Carpenter. 



I may add, in conclusion, that had geologists generally the oppor- 

 tunity of studying Eozoon in situ, in good exposures, like that at 

 St. Pierre, they would much more fully understand and appreciate 

 the arguments for its organic nature, than when they have had 

 opportunities of examining only polished specimens and slicesf. Its 



* Trans. Royal Irish Academy, 1871. 



t I have been sorry to find, from specimens in the cabinets of my friends, that 

 some London dealers are in the habit of circulating specimens labelled " Eozoon 

 canadense" which have no trace of the structures of the fossil, but are either badly 

 preserved acervuline portions or merely ordinary serpentine marble. Such speci- 

 mens can, of course, only mislead, and may produce much unnecessary scepticism. 



