GULLIVER. — SHORELINE TOPOGRAPHY. 171 



as to give criteria of uplift in one portion o£ the tilted region and those 

 of depression in another. 



The former shoreline in a tilted region, unless the axis of tilting was 

 parallel to the general direction of the coast, would not be level, as it 

 was found to be in a region uniformly uplifted. It will be progressively 

 higher away from the axis on the side of elevation, and will be more 

 irregular in height the more sinuous the shoreline before the tilting took 

 place. The raised beaches around lake Ontario, taking Dr. Spencer's 

 elevations of the Iroquois beach, show a very nearly even tilt. 



The position of the pivotal axis, as pointed out by Professor Shaler,* 

 gives differing results, and thus the criteria differ for the several cases. 

 The pivotal axis may lie parallel to the coast, at right angles to it, or 

 in any intermediate position. This axis may be at the shoreline, inland 

 from the coast, or seaward from the shore. The tilting itself may be of 

 two kinds; either the seaward slope maybe increased, or diminished. 

 These various possibilities will cause many variations in the quantity and 

 quality of the criteria. 



Topography of Tilted Regions : California ; New England. — A two- 

 cycle history of a region, in which an uplift occurs between the first and 

 the second, causes the development of composite topography. "When, 

 however, the uplift is not uniform, a new element comes in ; the topo- 

 graphic forms developed after a tilt are not only composite, but are also 

 inclined with respect to baselevel. Those forms of land, which were 

 developed with reference to one spheroidal plane when it coincided with 

 baselevel, are tilted, so that this spheroidal plane of the first cycle forms 

 throughout the region a constant angle with the plane of the sea in the 

 second cycle. The first cycle of course may be in any stage of develop- 

 ment when the tilt is made, but the recognition of the tilt will be pro- 

 gressively easier the later the stage reached before tilting. 



A peneplain extends north for a hundred miles from about the fortieth 

 parallel to the great bend of Pit river, California. f Tliis plain is tilted 

 at an inclination of 100 feet to the mile toward the east, and is canyoned 

 by streams 300 to 400 feet deep, which have not yet reached grade. 

 "The caiions in general are deepest to the westward and gradually run 

 out to the Sacramento river in the newer deposits which fill the valley. 

 It is evident that since the baselevel was formed, it has been affected by 



* Mem. B. Soc. Nat. Hist., 1874, II. 337. 



t J. S. Diller, Jour, of Geol., 1894, II. 32-54; 14tli Ann. U. S. G. S., 1892-93, 

 Pt. II. 429 ; W. Lindgren, Bull. G. S. A., 1893, IV. 257-298. 



