344 



EARTH FEATURES AND THEIR MEANING 



If now we descend from our position and visit the " battle- 

 field/' we find there a great ridge of level crest, behind which 

 the British force was stationed in its defense of the island in 

 1812. Near by in the woods is Pulpit Rock, a strikingly perfect 

 stack of the Nipissing Lake. Across the straits at St. Ignace is an 



even finer example of the notched 

 stack (Fig. 372). Other less prom- 

 inent beaches, but all later than the 

 Nipissing Lakes, intervene between 

 this level and the present shore to 

 mark the stages in the continued up- 

 lift of the land. 



The present inclinations of the up- 

 lifted strands. It is not enough that 

 we should have recognized the marks 

 of former shores now at considerable 

 elevations above the existing lakes; 

 if we are to know the nature of the 

 uplift, we must prepare accurate maps 

 based upon measurements by precise 

 leveling at many localities. Such 

 methods are, however, of compara- 

 tively recent application in this field ; 

 and, as in the investigation of so many 

 other problems, the earlier observa- 

 tions were largely of the nature of 

 reconnaissances with the elevation of 

 beaches estimated by comparatively 

 crude methods only. The evolution 



FIG. 373. Series of diagrams to 

 illustrate the evolution of ideas 

 concerning the uplift of the lake 

 region since the ice age. A, 

 simple northerly up-canting 



(Gilbert) ; B, northerly acceler- . -, . , -i , r 



ation of the up-canting (Spen- f ldeaS Concerning the Uptllt has, 



therefore, been a gradual one. 



It was early observed that the 

 beaches corresponding to a given lake 

 stage were higher to the northward 

 and northeastward, and the natural 

 conclusion from this was that the 

 earth's crust had here been canted 

 like a trap door (Fig. 373, A). As we are to see, this btft half- 

 correct assumption has led to a striking prophecy relating to future 



cer and Upham) ; C, northerly 

 "feathering out" of beaches 

 (Spencer and Upham) ; D, hinge 

 line of up-canting found within 

 the lake region (Leverett) ; E, 

 multiple and northwardly mi- 

 grating hinge lines of up-canting 

 (Hobbs). 



