CHAPTER VI. 



STUDIES OF SPECIAL LACUSTRAL HISTORY. 



It will appear to the reader of the preceding chapter that not only 

 are lakes ephemeral features of the earth's surface, but even the changes 

 they make in the' topography of their shores, although perhaps engraved 

 in solid rock, are of short duration in comparison with the length of the 

 eras into which the earth's history has Ijeen sul^divided. The lakes of 

 Pleistocene times, however, left records which in many instances are still 

 legible, and form a connection between historical and the most recent 

 geological times. 



As examples of extinct lakes whose histories are still clearly legible, 

 a brief account will be given of former water bodies of the Laurentian 

 basin, and in the region now draining to Lake Winnepeg, where the 

 climate is humid, and of two formerly extensive lakes of the Arid region. 



PLEISTOCENE LAKES OF THE LAURENTIAN BASIN. 



Long curving ridges of gravel having the appearance of great railroad 

 embankments, following the general trend of the shores of lakes Ontario 

 and Erie, but usually at a distance of several miles from their present 

 borders, were noticed at an early day in the settlement of New York, 

 Ohio, and Ontario, and correctly interpreted as being the records of previous 

 high-water stages of the lakes they encircle. These ridges became high- 

 ways of travel as civilization advanced, and gave origin to the term "ridge 

 road " still to be seen on local maps of the region referred to. These 

 ridges and other associated records have claimed the attention of geolo- 

 gists and others and have been made the subject of special i]U|uiry. The 

 territory traversed by them is so extensive, however, that their study is 

 still far from complete. 



The ancient beaches about lakes Ontario and Erie have been followed 

 and studied, especially l)y G. K. Gill)ert, in New York and Ohio, and by 

 J. W. Spencer, in Canada. The records of former water levels north of 

 Lake Superior from Duluth to Sault Sainte INIarie, have been traced and 

 mapped by A. C. Lawson. To the soutli of Lake Superior the ancient 

 shores have been systematically followed by F. B. Taylor. Many other 



