118 W. M. DAVIS RELATION OF GEOGitAPIIY TO GEOLOGY 



such a series of events we add a recent and slight depression, whereby the 

 bordering lowland is drowned on the north and south and the sea is thus 

 allowed to attack the border of the maturely dissected hard-rock uplands 

 along the base. of their stripped slope, M'e should have the best l)rief ex- 

 planatory account that I have been able to gather of the north and south 

 coasts of that picturesque region. 



During the deduction of a series of imaginary morvans, or during the 

 observation of a number of actual cases, a geographer has occasion to 

 make repeated mention of the essential elements which recur with differ- 

 ent values in every example, and he will thus in the most natural manner 

 possible come to designate the elements by the same set of names and to 

 qualify each of them by selected sets of adjectives. He will talk of the 

 undermass or the oldermass, and of the covering strata or overmass or 

 cover, and he will note that in most cases the undermass is composed of 

 disordered resistant crystalline rocks, while the stratified series in the 

 cover are usually less resistant ; he will talk of the earlier peneplain, now 

 partly revealed in a stripped belt, where the inclined cover has been worn, 

 off of the undermass ; of the later peneplain, now more or less dissected in 

 the upland or highland to which the term morvan more particularly 

 applies, and more or less completely destroyed in the area of the cover, 

 which may indeed be worn down to a third peneplain, and of the morvan 

 angle, namely, the acute angle between the intersecting peneplains. The 

 more definitely these elements are conceived and the more concisely and 

 consistently they are named, the easier will it be to describe new examples, 

 imaginary or real. 



TEE COLORADO FROST RANGE IS A MORVAN 



Conceive a morvan in which the undermass was worn down to a re- 

 markably smooth peneplain in its first cycle of erosion, heavily covered 

 with for the most part weak strata, uptilted to the east at a strong angle, 

 then long eroded, so that even the hard rocks of the undermass were re- 

 duced to a gently rolling later peneplain, here and there interrupted by 

 good sized monadnocks, irregularly placed, singly or in groups ; we should 

 thus have the morvan, which, when again uplifted and this time with 

 broad up-arching to a lofty altitude, and when then submaturely dis- 

 sected in its harder western undermass, of which the higher parts are well 

 carved by local glaciers, while the weaker eastern covering strata are worn 

 down a thousand feet lower to a new peneplain, would represent the Colo- 

 rado Front Eange and the adjacent plains here under discussion. In 

 other words, the Colorado Front Eange is a morvan, in which a belt of 

 the earlier peneplain appears as an inclined surface slanting about 30 



