No. 7.] DAWSON — LOCUST INVASION OF 1876. 417 



Winnipeg, Man., (F. E. Cornish.) A few passed over in 

 August, from north-west, going southward. 



St. Boniface, Man., (Hon. M. A Girard.) None. Swarms 

 from the west observed occasionally flying overhead, without 

 alighting, during latter part of July and to middle of August. 



Little Britain, Man., (Hon. D. Gunn.) No grasshoppers here. 

 Ten or twelve miles west of Selkirk, however, a little colony 

 covering about 1-J- acre hatched out, and were found more than 

 half grown in the middle of July. 



Lower Fort Garry, Alan.. (W. Flett.) None hatched here. 

 A few seen passing overhead about the middle of August. They 

 came with a south-west wind. 



Crookston, Minn., (E. M. Welsh.) None hatched here. Were 

 observed to pass overhead without alighting about the middle of 

 July. Near the first of August some alighted, and stayed a day. 

 Came from the north-west and north, and went south-eastward. 

 No damage to crops. No eggs deposited. 



THE MECHANICAL EFFECT OF ARCTIC ICE 

 IN PRODUCING OCEAN CURRENTS. 



By Henry Youle Hind, M.A. 



The area of the North Polar Ocean where salt water ice is 

 annually formed to a mean thickness of four feet, may be assumed 

 equal to 4,000,000 square geographical miles. 



This area is less by 521,600 square miles than that of the 

 superficies enclosed by the 70th parallel of north latitude, which 

 is supposed to encircle a space equal to the Arctic water area 

 frozen each year. 



In order to compensate for the land area within the 70th 

 parallel, it is necessary to add Hudson Bay and Straits, part of 

 Davis Strait, the South-East Greenland Sea area, the White Sea, 

 etc., in a word, wherever salt water ice is formed within the 

 Northern zone. 



During the process of freezing, salt water ice is raised about 

 one-tenth of its volume above the level of the sea. The ice con- 



