1866.] GUMBEL — ON LATJRENTIAN ROCKS. 85 



crystalline limestone which occur in the Lauren tian system. Such 

 were collected in 1858, by Mr. J. McMullen from the Grand 

 Calumet on the Ottawa River, and were observed by Sir Wm. 

 Logan to resemble closely similar specimens obtained by Dr. James 

 "Wilson in Burgess, a few years previously. In 1859, Sir Wm. 

 Logan first expressed his opinion that these masses, in which 

 pyroxene, serpentine, and an allied mineral, alternated in thin 

 layers, with carbonate of lime or dolomite, were of organic origin ; 

 and in 1862 he reiterated this opinion in England, without 

 however being able to convince the English geologists, Ramsay 

 excepted, of the correctness of his views. Soon after this, 

 however, the discovery of other and more perfect specimens, at 

 Grenville, furnished decisive proofs of the organic nature of these 

 singular fossils. 



The careful and admirable investigations of Dawson and of 

 Carpenter, to whom specimens of the rock were confided, have 

 placed beyond doubt the organic structure of these remains, and 

 confirmed the important fact that these ancient Laurentian lime- 

 stones abound in a peculiar organic fossil, unknown in more recent 

 formations, to which has been given the name of Eozoon.* 



The researches of Sterry Hunt on the mineralogical relations of 

 the Eozoon-bearing rocks, lead him to the important conclusion 

 that certain silicates, namely serpentine, white pyroxene, and 

 loganite, have filled up the vacant spaces left by the disappearance 

 of the destructible animal matter of the sarcode, the calcareous 

 skeleton remaining more or less unchanged. If, by the aid of 

 acids, we remove from such specimens the carbonate of lime, (or, 

 in certain cases, the dolomite which replaces it,) there remains a 

 coherent skeleton, which is evidently a cast of the soft parts of the 

 Eozoon. The process by which the silicates have been introduced 

 into the empty spaces corresponds evidently to that of ordinary 

 silicification through the action of water. It is to be noted that 

 Hunt found serpentine and pyroxene, side by side, in adjacent 

 chambers, and even sharing the same chamber between them ; 

 thus affording a beautiful proof of their origin through the 



* Here follows, in the original, a lengthened analysis of the memoirs 

 of Messrs. Logan, Dawson, Carpenter, and Hunt, published in the 

 Quarterly Journal of the Geological Society of London, and already 

 reprinted in the Canadian ^Naturalist. 



