THE 



CANADIAN 



NATURALIST AND GEOLOGIST. 



Vol. IV. JUNE, 1859. No. 3. 



ARTICLE XL — On the Microscopic Structure of some Canadian 

 Limestones. By J. W. Dawson, LL.D., F.G.S., kc 



[Read before the Natural History Society of Montreal.] 



Geology has shewn that over a great part of the earth's surface 

 we can say, almost without hyperbole, "The dust we tread upon 

 was once alive." Great and very extensively distributed beds of 

 rock are of organic origin, made up of the remains of the hard 

 parts of animals, and these often of very minute dimensions. In 

 the bed of the sea, more especially in the coral regions of the 

 Pacific, the Indian ocean and the equatorial Atlantic, such deposits 

 are now manifestly in progress on a large scale; and in the arche- 

 pelagos of the Pacific, the Bermudas, and the peninsula of Florida, 

 we have examples of these modern formations elevated into land. 

 Similar phenomena exist on a still greater scale in the Tertiary 

 rocks; as for instance in the Nummulitic limestones, extending 

 from the west of Europe almost continuously into India, built up 

 into mountain masses in the Alps, Pyrenees, Carpathians and 

 Himmalaya*, and furnishing the materials of the Egyptian Pyra- 

 mids, and of thousands of humbler structures. In the secondary 

 period, the chalk and many of the oolitic limestones present simi- 

 lar phenomena. Similar organic rocks occur in all the members 

 of the palaeozoic series down to the lowest Silurian; and in these 

 earliest periods of the earth's geological history, when organic 

 Canad. Nat. 1 Vol. IV. No. 3- 



