374 THE CANADIAN NATURALIST. [Vol. viii. 



To those who pay little attention to the subject the disappear- 

 ance of the swarms that left the Mississippi Valley is matter for 

 wonder. " What is hit is history, but what is missed is mystery." 

 Who, at the explanation of some simple trick or piece of leger- 

 demain, has not smiled to think how easily he was baffled ! But 

 there are those who prefer the mystery of ignorance, and would 

 much rather believe that the locusts have vanished in the hsavens 

 or been swept into the ocean than accept any explanation ; and 

 there are others who, from sectional feelings, would much rather 

 believe that the insects have flown to Canada and New England 

 than accept the facts. 



MISCELLANEOUS. 



Archaean of Canada. (Letter from Mr. Henry G. Vennor, 

 of the Geological Survey of Canada, to J. D.Dana, dated Buck- 

 ingham, July 10th, 1877.) — I take the liberty of addressing this 

 letter to you, on a subject in which I have for some years been 

 particularly interested, viz : the stratigraphical position of the 

 economic minerals in what we have hitherto called the Lower 

 Laurentian system of rocks. 



I may briefly give you the results arrived at, after now some 

 ten years work in Eastern Ontario and the adjoining portion of 

 the Province of Quebec, namely, Pontiac and Ottawa counties. 

 We find that there still exists a great Azoic formation, consisting 

 of syenite and gneiss (?) without crystalline limestones. In this 

 there are but little indications of stratification. Occasionally a 

 limited surface presents an approach to an obscure stratification, 

 but this does not appear to be due to the deposition of sediment. 

 This rock forms the back-bone of Canada. On it there has been 

 deposited a great series of gneisses, schists, slates, crystalline 

 limestones and dolomites, which, although heretofore grouped 

 with the former, >s clearly distinct and unconformable. This 

 second system contains all of the economics of any importance ; 

 none having been found in the old fundamental red gneiss system. 

 All of these economics are in close proximity and have close 

 relationship to each of the four or five great bands of crystalline 

 limestone. 



Eozoon Canadense belongs undoubtedly in the main to the 



