172 PROCEEDINGS OF THE AMERICAN ACADEMY. 



differential elevation in the uplifting of the Coast range and Klamath 

 mountains, just north of the fortieth parallel, to the extent of over 

 2,000 feet." * 



A slope of small angular value, viz. 0° 8' 5", across the State of Mas- 

 sachusetts carries the southern New England peneplain to an eleva- 

 tion of twenty-five hundred feet in a distance of one hundred and sixty 

 miles. As one stands upon the peneplain in the western part of Massa- 

 chusetts, he may look to the southeast across an almost even surface of 

 denudation with liere and there a mouaduock rising above it, a monument 

 of resistant rock. 



Warping: New Brunswick, N.J. — The definition of a warped surface 

 here adopted is that given in geometry, namely, a surface generated by a 

 straight line moving so that no two of its consecutive positions shall be 

 in the same plane. Various cases under warping may occur, the marked 

 characteristic of them all being the variability of the criteria. 



In the depression or uplifting of the Schooley peneplain t there appears 

 to have been a warp, which causes the portion of the Cretaceous pene- 

 plain near New Brunswick to be lower than the rest. 



Santa Catalina Depression. — Professor Andrew C. Lawson has de- 

 scribed t a very beautiful instance of differential movement between San 

 Pedro hill on the mainland and San Cleraente island. Upon the south- 

 ern California coast and also upon San Clemeute are many well marked 

 sea-cliffs rising one above another to an elevation of some 1500 feet.§ 

 These show pauses in a progressive series of uplifts. But between San 

 Clemente island and San Pedro hill lies Santa Catalina island (C. S., 

 5100), whose land sculpture shows subsidence and not elevation. Upon 

 this island (C. S., 5128, old number 613) there is a good example of a 

 divide almost submerged. Professor Lawson says that the sea-cliffs 

 show more rapid recession than is usually found in stationary or rising 

 coasts. He considers this Santa Catalina depression an erogenic, or local 

 movement, which occurred at the same time or later than the epeiro- 

 genio or general uplift, shown by many observations along the coast of 

 California. 



Crumpling and Faulting. — Cycles and epicycles caused by uplift or 

 depression merge through tilting, crumpling, and faulting into those in- 

 augurated by mountain-building. A graded series of forms may be con- 



* Jour, of Geol., 1894, II. 45. 



t Messrs. Davis and Wood, Proc. B. Soc. Nat. Hist., 1889, XXIV. 380. 



X Bull. Dept. Geol, Univ. of Cal., No. 4, 1893, I. 122-139. 



§ See p. 164 and Figure 4. 



