CORROSIVE ACTION OF BRINES IN MANITOBA 



465 



the bowlders from the salt flats. The relatively small difference 

 in concentration of sodium chloride is not sufficient to account for 

 the difference in chemical activity in the two cases. 



Bowlders between high and low watermark are situated simi- 

 larly to those on the salt flats in one particular — -they are in intimate 

 contact with the solution and with the atmosphere. They are 



Fig. 3. — Corroded bowlder, salt flat, Pelican Bay, Lake Winnipegosis 



differently placed, however, in that they are alternately water- 

 covered and dry to the base. Evaporation does not proceed so 

 far that sodium chloride is precipitated, and films of liquid are not 

 fed over the surface of the bowlder from the base. The initial 

 disintegration of the bowlder is consequently less readily effected, 

 and the acidification of the solution through absorption is to a 

 similar extent retarded. 



While to different physical conditions may be attributed the 

 difference in degree of corrosion of beach bowlders and bowlders 



