REPORT OP THE DIRECTOR AND STATE GEOLOGIST 1900 r27 



if it exists. There is no sudden shallowing of the water in pass- 

 ing from the main lake into the bays, nor are the lakes them- 

 selves specially deep. They also contain numerous rock islands. 



It is not believed that the presence of this preglacial drainage 

 system in any way accounts for the topographic peculiarities of 

 the lake belt. It is too sharply and abruptly m>arked off from 

 the adjoining districts, that to the east particularly. It is, rather, 

 believed that it is a structural depression. The evidence that 

 the mountainous belt to the east is along an axis of compara- 

 tively recent uplift has been presented in the 18th annual report. 

 Meridional faults of large throw are present; and it is thought 

 that the uplift has been mainly effected by differential move- 

 ments along the fault planes. The miost reasonable explanation 

 of the lake belt is that it is a dropped fault block, the district 

 to the east having been largely uplifted with respect to it,, that 

 to the west much less so. The following topographic features 

 seem to fall in line with this explanation. 



In the eastern Adirondacks the altitude and relief are con- 

 siderable, and the hilltops rise to various levels, with little sign of 

 that concordance in altitude which might reasonably be expected 

 in such an old land area, as marking periodis of rest between 

 the various uplifting movements which the region has undergone. 

 In St Lawrence county, in the western Adirondacks, the numer- 

 ous hills and ridges do attain very coincident altitudes and 

 strongly suggest a peneplain with occasional monadnocks rising 

 above the general level. In the pre-Oambrian district in central 

 Ontario, which the writer had the pleasure of seeing last sum- 

 mer, under the guidance of Dr A. E. Barlow of the Canadian 

 survey, the same accordant altitudes of the ridge crests were 

 noted and commented on. The slight relief in the lake belt has 

 been already noted. Now, recent uplifting in varying degrees 

 along the meridional faults of the eastern Adirondacks would 

 have largely obscured or destroyed the traces of such previous 

 accordance there, and is thought to be the most probable cause 

 of their absence. The known presence of such faults and the 

 impressive fault scarps which are such a prominent feature in 



