452 



SCIENCE 



[N. S. Vol. XXVI. No. 666 



1906). The older rocks of the district are 

 chiefly deformed mica schists. They have 

 been reduced to a peneplain, which is now 

 uplifted and scored in its seaward portion by 

 deep, narrow valleys. Farther inland, the 

 peneplain has been broken into a number of 

 sub-parallel blocks, of which the higher ones 

 form mountain ranges, generally trending 

 northeast-southwest, and reaching from 5,000 

 to 6,000 feet altitude; while the relatively de- 

 pressed blocks are buried under heavy basin 

 deposits of lacustrine, fluviatile and glacial 

 origin. The ranges are not forested and ex- 

 pose a large amount of bare rock; they are 

 as a rule flat topped ; " the skyline of the 

 Hawkduns for a distance of twenty miles ap- 

 pears as even as the ridge of a house " ; they 

 have no lateral spurs or foothills, but descend 

 to an almost straight base line. The basin 

 deposits have been more or less terraced and 

 dissected. A rough cross-profile suggests that 

 some of the heaved blocks are bounded by 

 faults on both sides, and that, though retain- 

 ing old forms on their flat uplands, they have 

 lost miieh of their edges by new erosion. 



The few pages from which the above state- 

 ments are gleaned are only incidental to the 

 chapters on geological and economic problems 

 to which the body of the report is devoted ; the 

 student of physiography must, however, be 

 grateful if he gets even so much as these few 

 pages from a professor of mining, whose first 

 responsibilities are elsewhere directed. Tet 

 is it not probable that, if a well-systematized 

 plan for the physiographic description of 

 block mountains were in general use among 

 geographers, there would not so often be occa- 

 sion to regret that significant physiographic 

 features' are passed over without mention in 

 a geological report? To illustrate: When a 

 comet is discovered, it is customary for 

 astronomers to secure at once certain previ- 

 ously planned observations, according to a 

 standardized method; and from these observa- 

 tions the elements of the comet's orbit are 

 promptly calculated according to an accepted 

 scheme. As a result, the chief items which 

 astronomers have come to agree upon as 

 essential regarding comets are irmnediately 



determined and placed on record. No such 

 standardized method of procedure is yet 

 adopted by geographers, still less by explorers ; 

 and as a result it is largely a matter of chance 

 whether the description of a new member of an 

 already known class of land forms — block 

 mountains, for example — ^will include its es- 

 sential elements or not. In a case of the kind 

 above cited, the most important elements 

 would probably be: the general structure of 

 the region, briefly stated at first, with details 

 added later when needed; the stage of erosion 

 that the region had reached when block-fault- 

 ing took place; the relation of the fault lines 

 to the preexistent structural lines and topo- 

 graphical features; the number and attitude 

 of the heaved and of the thrown blocks ; sys- 

 tematic account of the main drainage lines, 

 suificient to show whether they persist from 

 the previous cycle as antecedent streams in 

 spite of the adverse faulting, whether they are 

 revived into new activity by favoring deforma- 

 tion, whether they are of a new generation 

 consequent upon the slope of the tilted or 

 faulted faces of the displaced blocks, or wheth- 

 er they are developed as subsequent streams by 

 headward erosion along newly exposed weak 

 structures ; definite indication of the stage 

 reached in the work of erosion by the several 

 kinds of streams on their valley lines, and in 

 the work of gradation by weathering on the 

 fault faces and valley sides, with particular 

 reference to the manner in which the features 

 produced in the new cycle are related to those 

 still holding over from the previous cycle and 

 to those produced directly by faulting; indi- 

 cation of the stage reached in the work of 

 ag-g-radation (and afterwards of degradation) 

 over the thrown blocks; and finally, as many 

 specific details as possible, not described em- 

 pirically, but systematically presented as in- 

 stances of the above-named elements. 



It will always be difficult for even the 

 best trained physiographers to secure a com- 

 plete record of all desired elements of land 

 forms; but the knowledge of land physiog- 

 raphy will be immensely advanced when work 

 in the field is carried on in view of carefully 

 standardized and generally accepted schemes. 



