igoo-i.] Physical Geology of Central Ontario. 151 



Had the ridges existed prior to the deposition of the sediments, 

 having- been the product of erosion, the structure of ridge and valley- 

 would frequently have the same dip ; in cases where the dips varied the 

 diversity would not be systematic. The position assumed by the 

 sediments would depend upon three factors, two of which are, in 

 practice, determinable by observation, the third by inference only. The 

 steepness of the grade of the ridge would necessarily be an important 

 factor. Where the grade was light the sediments would be deposited 

 evenly over the inclined floor. As the inclination of the floor increased 

 the tendenc}- would be for the beds to wedge out and finally to abut 

 against, rather than to rest upon the incline. The fineness or coarseness 

 of material and the degree of agitation of the water would be important 

 varying factors. Where the waters were quiet, and the sediments 

 coarse, the deposition could take place upon slopes down which the 

 materials would readily move if the waters were agitated. If the 

 sediments were fine, the slopes upon which they could rest would be 

 much steeper. The angle of repose for the sediments will then vary as 

 each factor varies, and hence numerous variations are possible and 

 many of these are also probable. 



The deduction leads to inquiry as to what is the maximum angle of 

 repose at which, under what ma}^ be called normal conditions of 

 deposition, strata of different compositions may be deposited, for 

 obviousl}' this must be known before we can determine, from the dip 

 alone, whether strata were deposited in an inclined position. The 

 number of variants is too great to permit of a complete reply to the 

 .question ; it seems advisable rather to apply the criteria already 

 deduced to the facts under consideration, and indirectl}' to obtain a 

 partial answer to the last problem. 



In the areas where the gneiss is not obscured by a cover in the 

 bottoms of the valleys, we frequently find the dips the same over large 

 areas of ridge and valley; sometimes there is diversity, in the valley it 

 may be vertical while in the ridge it is inclined, or vice versa, but 

 uniform diversity is not found. This iinifonn continuity and lack of 

 uniform diversity, particularly in areas where the structures are inclined 

 away from the vertical, would alone indicate that these are not ridges of 

 deformation, but on the contrary, would lead us to infer that they are 

 the result of erosion. 



Attention has already been called to the lack of sympathetic dip in 

 limestones adjacent to steep gneissic ridges. At Kingston Mills cut the 

 upper part of the granite face was too steep for the coarse sedimentary 



