3^4 



TRANSACTIONS OF THE CANADIAN INSTITUTE. 



[Vol. v. 



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Figures 2 and 3 illustrate the descent of three great channels roin the col of the Straits ot Florida to the 

 floors of the Mexican and Atlantic basins, (for their locations see Map). They show a succession of steps 

 like great base levels separated by precipitous slopes. The soundings have been made where the figures are 

 shown in feet. The gradients are given in feet, for distances expressed in miles. The descent of the 

 Colorado canyon is illustrated in figure 2. 



