462 R. C. WALLACE 



values are due to the fact that in the statement of the analysis of 

 sea-water the total carbonate is reckoned as normal carbonate. 

 The concentration of the brine is, however, notably higher than 

 that of sea-water. 



Action on the bowlders. — -The glacial drift was to a large extent 

 derived from the pre-Cambrian areas in the north. The bowlders 

 which cover the bare flats where the salt springs are found are 

 mainly gneissose or granitic, though occasionally dark-green epi- 

 diorites or Paleozoic limestones are seen. Chemical solution has 

 taken place on an extensive scale, many bowlders having been 

 reduced on every side by at least a foot. This is very clearly seen 

 in the salt creeks in which the water is carried from the springs to 

 the lake, the bowlders standing on a much-eroded base, like the 

 rocks of a great sand desert. On the flats the bowlders are pitted 

 into very fantastic forms, the ferromagnesian minerals having 

 suffered to the greatest extent. Not even quartz nor garnet has 

 escaped the action of the solvent. Gneissose structures are accen- 

 tuated by differential weathering, garnetiferous bands standing out 

 in special relief. As the corrosive power of the brine is apparently 

 much more intense than that of sea-water, it is of interest to inquire 

 into the processes involved in the disintegration of the rock. 



Chemical processes. — -Regarded as a chemical agent, the brine 

 may be considered to be a weak solution of sodium chloride. A 

 considerable amount of experimental work has been done on the 

 action of solutions of sodium chloride on minerals, but the evidence 

 is somewhat conflicting. 1 Toly has, however, proved that sodium 

 chloride, in the presence of the atmosphere, is a more active dis- 

 integrating agent than pure water. Daubree's experiments were 

 conducted under somewhat different conditions. In the case of 

 the brines physical conditions have been favorable. Normally 

 the salt crystallized in thin crusts at the base of the bowlders. The 

 salt is somewhat deliquescent, and gradually extends upward over 

 the side of the bowlder, till a thin coating of brine, somewhat diluted 

 during the process, covers the whole bowlder. The conditions are 

 thus most favorable for chemical activity in presence of the atmos- 



1 Daubree, Synthetische Studien zur Experimentalgeologie, 1880, 205; Thoulet, 

 Compt. Rendu, CX, (1890), 652; Joly, Proc. Roy. Irish Acad., XXIV (1902). 



