274 ASSINNIBOINE AND SASKATCHEWAN EXPEDITION. 



The crystalline limestones in the Laurentian series 

 are daily acquiring increased importance. In the Eeport 

 for the year 1858, recently issued, Sir William Logan 

 states that in the present state of the investigation there 

 appears to be a sequence of four important bands of 

 crystalline limestone in the Laurentian area examined ; 

 but the wrinkled condition of the strata is such that in a 

 space of not more than fifty miles by twenty, one of the- 

 bands exhibits an outcrop exceeding two hundred miles 

 in length, which renders it very difficult to determine 

 with precision the volume of rock in which the four cal- 

 careous bands are enclosed. The following is Sir William 



minerals in places so far apart. If the specimens had been obtained from 

 the altered rocks of the Lower Silurian series there would have been little 

 hesitation in pronouncing them to be fossils. The resemblance of these 

 forms to Stromatocerium from the Bird's-eye limestone, when the coral has 

 been replaced by concretionary silica, is very striking. In the pyroxenic 

 specimens, the pyroxene and the carbonate of lime being both white, the 

 forms, although weathered into strong relief on the surface, are not percepti- 

 ble in fresh fractures until the fragments arc subjected to an acid, the appli- 

 cation of which shows the structure running throughout the mass, Several 

 specimens of these supposed fossils were exhibited to the section." 



The suppositions embodied in the foregoing extract do not coincide with 

 the views relating to the origin of life expressed by Sir Roderick Mur- 

 chison in the proceedings of the Geological Society for November, 1859, 

 p. 219. The Cambrian rocks referred to, rest on the fundamental gneiss or 

 Laurentian rocks of the North Highlands of Scotland : — 



u The phenomenon relating to these Cambrian sandstones which may well 

 strike the geologist as he passes over the summits of Suilven and Queenaig, 

 is that these very ancient rocks, on which unquestionably the Lower Silurian 

 rocks repose, should be simply sandstones and grits, which have undergone 

 much less change than the sandstone which lies upon them,— the latter 

 having been metamorphosed into quartz-rock. However difficult it may be 

 to account for this fact, it is at all events most instructive as regards the origin 

 and succession of life in the crust of the earth, and sustains my view of 

 a beginning. For here (and I have applied the same argument before to the 

 Cambrian sandstones of the Longmynd, which certainly underlie the quartz- 

 rock of the Stiper Stones) the older of the two rocks in Scotland has 

 offered no trace of fossils, whilst the more crystallized structure above 

 exhibits unmistakable signs of former living things." 



