630 



SCIENCE. 



[N. S. Vol. XXIII. No. 590. 



ing their properties. The investigation is 

 still in progress at the "University of Wis- 

 consin. So far a ton of the material has 

 been produced. C. J. Borgmeyer, 



Corresponding Secretary. 



THE CLEMSON COLLEGE SCIENCE CLUB. 



The sixtieth regular meeting of the club 

 was held on Friday evening, January 19. The 

 following program was given: 



De. E. N. Bkackett : ' The Contact Process of 

 Making Sulphuric Acid.' 



Professor F. T. Dargan : ' Modifications in 

 Laboratory Apparatus.' 



Dr. L. a. Klein : ' New Developments in the 

 Prophylaxis and Treatment of Tuberculosis.' 



Professor S. B. Earle: 'The Internal Com- 

 bustion Engine with Especial Reference to the 

 Diesel Engine.' 



Fred H. H. Calhoun, 



Secretary. 



DISCUSSION AND CORRESPONDENCE. 

 the physiography of the adirondacks. 



To THE Editor of Science: An article by 

 Professor Kemp in the March number of the 

 Popular Science Monthly with the above title 

 treats a subject on which I have been desirous 

 of getting fuller information for some years 

 past, namely, the origin of the mountain and 

 valley forms in the Adirondacks; but there 

 is a certain phase of the subject which still, 

 to my reading, remains in doubt, namely, the 

 age of the faults by which the mountain sides 

 — or valley sides — are determined. The ques- 

 tion arises whether the faults may not be rela- 

 tively ancient rather than 'of no great geolog- 

 ical antiquity,' and whether the valley-side 

 scarps which now indicate the course of the 

 faults may not be, not ' obviously the result of 

 faulting,' but the result of differential erosion. 



It is well known that the scarps which follow 

 fault lines are of two kinds. Of one kind are 

 those scarps which are the direct result of 

 faulting or displacement, modified more or 

 less by later erosion on the scarp face. Such 

 a scarp is found along the western base of the 

 Wasatch Mountains in Utah ; and I believe that 

 a similar fault scarp marks the base of the 

 Eocky Mountains a few miles south of Colo- 

 rado Springs. In both these eases, the dis- 



placement seems to have been progressive and 

 to have continued through so long a period of 

 time that the upper part of the fault face has 

 been much dissected and worn back by erosion ; 

 the true fault scarp is seen only along the moun- 

 tain base, where the face of the most recent 

 uplift is comparatively little changed. It is 

 evident that, as time passes, such fault scarps 

 will be more and more worn back, and that 

 in time they will be topographically obliterated. 

 Topographically obliterated faults are common 

 in the Appalachians where the faulting is of 

 remote date. 



Of another kind are those scarps which truly 

 follow fault lines, yet which are directly the 

 result of erosion rather than of faulting. For 

 example, the Hurricane Ledge or escarpment 

 in the Arizona plateaus north of the Colorado 

 canyon. This scarp was originally described 

 as wholly the direct effect of faulting; but 

 later study has given good reason for believing 

 that it is the effect of differential erosion ; that 

 the original effect of the displacement was ob- 

 literated in a past cycle of erosion, and that 

 in the present cycle the scarp has been brought 

 to light again by the removal of the weaker 

 strata on the west of the displacement, while 

 the more resistant strata remain in strong re- 

 lief on the eastern side. Similarly in the 

 Triassic formation of Connecticut, numerous 

 scarps in the trap ridges are here known to 

 follow fault lines; yet the faults are demon- 

 strably so old that their original topographic 

 effects were completely obliterated in a past 

 cycle of erosion, and the fault scarps as now 

 seen result from the revival of erosion follow- 

 ing a general uplift of the worn-down region 

 and the consequent removal of the weaker 

 rocks on one side of the fault line, leaving the 

 resistant trap sheets on the other side in strong 

 relief. (This statement does not apply to the 

 western faces of the trap ridges, which are 

 merely retreating escarpments entirely due to 

 erosion; but to the oblique escarpments, where 

 the trap ridges are cut off by the faults.) In 

 the same region there are a few narrow graben- 

 like troughs, enclosed by steep walls; they are 

 not due to recent faulting, but to the removal 

 by modern erosion of the zone of shattered 



