304: ANNUAL OF SCIENTIFIC DISCOVERY. 



pierced a way lower down the valley. At a former period, the val- 

 leys of the Frazer and the Thompson seern to have been occupied by 

 a succession of lakes, the cascade ridge then forming a barrier which 

 dammed up this great volume of water. The highest tier of terraces 

 would mark the level at which it then stood. Some geological con- 

 vulsion caused a rent in the mountain barrier, allowing the waters to 

 escape partially, so as to form a chain of lakes at the level of the 

 middle terraces ; and subsequently, after long periods of repose, two 

 other similar disturbances successively deepened the cleft, and drained 

 the waters first to the hight of the lowest terrace, and finally to their 

 present level. 



ORGANIC REMAINS IN THE LAURENTIAN ROCKS OF CANADA. 



One of the most interesting of recent geological discoveries has 

 been the detection of the remains of a protozoic animal in lower 

 series of the Laurentian rocks of Canada, which are among the oldest 

 of the stratified rocks which have been designated as Azoic (want- 

 ing in life). The facts relating to this discovery are substantially as 

 follows : 



The oldest known rocks of North America, composing the Lau- 

 rentian Mountains in Canada, and the Adirondacks of New York, 

 have been divided into two unconformable groups, which have been 

 called the Upper and Lower Laurentian respectively. In both divis- 

 ions zones of limestone are known to occur, and three of these 

 zones have been ascertained to belong to the Lower Laurentian. 

 From one of these limestone bands, occurring at the Grand Calumet 

 on the River Ottawa, Mr. J. McCulloch obtained, in 1858, specimens 

 apparently of organic origin, and other specimens have also been 

 obtained from Grenville and Burgess. These specimens consist of 

 alternating layers of calcareous spar, and a magnesian silicate (either 

 serpentine, white pyroxene, phyrallolite, or Logauite), the latter 

 minerals, instead of replacing the skeleton of the organic form, really 

 filling up the interspaces of the calcareous fossil. Dr. Dawson of 

 Montreal, carefully examined the laminated material, and he found it 

 to consist of the remains of an organism which grew in large ses- 

 sile patches, increasing at the surface by the addition of successive 

 layers of ch mibers separated by calcareous laminae. Slices examined 

 microscopically showed large irregular chambers with numerous 



f^ ^j 



rounded extensions, and bounded by walls of variable thickness, 

 which are studded with septal orifices irregularly disposed; the thick- 

 er parts of the walls revealed the existence of bundles of fine branch- 

 ing tubuli. Dr. Dawson, therefore, concludes that this ancient organ- 

 ism, to which he gave the name of Eozoon Canadense, was a 

 Foraminifer allied to Carpentaria by its habits of growth, but of 

 more complex structure, as indicated by the complicated systems of 

 tnbuli ; it attained an enormous size, and by the aggregation of indi- 

 viduals, assumed the aspect of a coral reef. In a paper read before 

 the (London) Geological Society, Nov. 1804, Dr. Carpenter, the 

 eminent English microscopist and physiologist, corroborated Dr. 

 Dawson's observations on the structure and affinities of Eozoon, but 

 stated also that, as he considered the characters furnished by the in- 

 timate structure of the shell to be of primary importance, and the 



