322 



REVIEWS GEOLOGICAL SURVEY OF CANABA. 



means of tracing out the physical structure of the Laurentide 

 district." 



The more important details of this Report, have already appeared 

 m the Canadian Journal, in the form of separate papers communi- 

 cated by Sir William Logan ; * but the following additional remarks 

 on the economic capabilities of the limestones and lime feldspars of 

 the gneissoid rocks, will be read with much interest : 



The crystalline limestones of the Laurentian series are quite as good for all 

 the economic purposes to -which carbonate of lime is applied, as the earthj' lime- 

 stones of the fossiliferous formations. It is from the latter, however, that i^ 

 obtained nine-tenths of the material used throughout the country, for the very 

 good reason that more than nine-tenths of the -works of construction, both public 

 and private, are raised upon the fossiliferous rocks, and for such present -works, 

 these rocks therefore afford the nearest sources of supply. Thus the inhabitants 

 are -well acquainted -with the aspect of the fossiliferous limestones, and can easily 

 recognise them, but very fe-w of them understand the nature of the highly crystal- 

 line calcareous beds of the Laurentian series. Hence it is that settlers in the 

 back townships, who have dwelt many years upon these rocks, have been ac- 

 customed, -when in -want of lime for the manufacture of potash, or the construc- 

 tion of their chimneys, to send to the fossiliferous deposits for it — the distance 

 being sometimes thirty miles — -when it might have been obtained at their own 

 doors. In folio-wing out the calcareous bands of the gneiss district, in 1853, there- 

 fore, especial pains were taken to point out their character to the settlers, where- 

 ever exposures were met with ; and in visiting some of the same localities last 

 season, I had the satisfaction of finding lime-kilns erected, and lime burnt in four 

 of them. 



The fossiliferous rocks, in a large part of Canada, maintaining an attitude ap- 

 proaching horizontality, give a much more even surface than the corrugated series 

 coming from beneath them, and this, combined with a generally good soil, renders 

 them more favorable for agricultural purposes. It is over them, too, that the 

 River St. Lawrence maintains its course, affording an unrivalled means of exit for 

 the produce of the land, and of entrance for the materials that are to be received 

 in exchange. It is only a natural result of these conditions that the area sup- 

 ported by the fossiliferous rocks should be the first settled. Tliis area, however, 

 constitutes only between 60,00C and 80,000 square miles, while the whole super- 

 ficies of Canada comprehends 330,000 square miles, or about five times the 

 amount. 



Four-fifths of Canada thus stand upon the lower unfossiliferous rocks, and it be- 

 comes a question of some importance, before it has been extensively tested by 

 agricultural experiments, to know what support this large area may offer to an 

 agricultural population. An undulating surface, derived from the contorted con- 

 dition of the strata on which it rests, will more or less prevail over the whole of 

 this region ; but the quality of its soil will depend on the character of the rocks 

 from which it is derived. 



* See ante. Vol. II. p. 439, Vol. III. pp. 1, 107. 



