Sir W. Daivson — The Animal Nature of Eozoon. 445 



my notes, and camera drawings prepared by the artist of the 

 Geological Survey. Dr. Sterry Hunt had also examined chemically 

 the serpentine and other minerals associated with the supposed 

 fossils, and various hydrous silicates mineralizing organic remains 

 in Silurian and other limestones, as terms of comparison. The 

 whole was then communicated to the Geological Society of London, 

 and appeared in the somewhat elaborate joint paper published in 

 1865. 



[But a preliminary account entitled " On the occurrence of 

 Organic Remains in the Laurentian Eocks of Canada," by Sir W. E. 

 Logan, F.R.S., F.G.S., with communications on the structure by 

 J. W. Dawson, LL.D.. F.E.S., and on the Mineralogy of the same 

 remains by T. Sterrj'^ Hunt, F.E.S., had, however, been communicated 

 to the British Association at Bath, Sept. 15-21, 1864, and was 

 subsequently published in the Geological Magazine, Vol. I, for 

 November 1864, pp. 225-227.] 



I confess that in the intervening time I liave seen no good reason 

 to induce me to doubt the essential validity of the work embodied -^ 

 in this paper of 1865, or to modify to any considerable extent 

 the conclusions thei'ein stated. On the other hand, many new and 

 confirmatory facts have been disclosed, and after careful and, I trust, 

 candid study of the objections raised, down to those which have 

 recently appeared in the Dublin Transactions, I believe that they 

 largely depend on want of knowledge of the character of the 

 Grenville formation, and on misapprehension as to the form and 

 structure of Eozoon and its mode of occurrence. 



It is true that in those members of the Laurentian system of 

 Logan which are below and above the Grenville Series, later obser- 

 vations have not only failed to detect fossils, but have shown valid 

 reasons adverse to the probability of their occurrence, at least in 

 the portions of those formations hitherto open to our study. ^ 



The lowest Laurentian gneiss of Logan (Trembling Mountain 

 gneiss, Ottawa gneiss, fundamental gneiss), which occupies a vast 

 area in Northern Canada,^ and is the only part of the system known 

 to many geologists, consists, so far as known, wholly of foliated 

 or massive orthoclase gneiss, with bands of hornblendic schist 

 (amphibolite), and of hornblendo-micaceous schist. While in some 

 places it appears to have a truly bedded structure, especially where 

 different varieties of gneiss, amphibolite, and biotitic schist alternate, 

 in others its foliation is obscure, or seems to have been induced by 

 heat and pressure. Dr. F. D. Adams, who has given much study 

 both to its characters on the large scale, and to the microscopic 

 structure of the rocks, in his latest publication on the subject^ 

 characterizes it as a complicated series of rocks of unknown origin, 



1 See Geological Magazine, June, 1895. 



2 According to the geokigical map of Northern Canada prepared by Dr. G. M. 

 Dawson for the Geological Survey, the area of Laurentian rocks exceeds two 

 millions of square miles. Of this, so far as is known, the older or fundamental 

 gneiss occupies by far the larger portion. 



2 American Journal of Geology, vol. i, No. 4, 1893. 



