616 PROCEEDINGS OF THE NEW YORK MEETING 



if you please) of a practically homogeneous conglomerate. After the ordinary 

 process of erosion uncovers a sufficient surface of the indurated rock, the dome 

 structures are formed by a successive scaling off of blocks, through the devel- 

 opment of cracks approximately parallel to the steeply sloping surfaces. 

 These cracks are probably due to expansive force developed by chemical re- 

 actions (weathering) produced largely by moisture, the moisture passing 

 vipward by capillarity through the incipient cracks caused by expansion, and 

 thus advancing the process. The cracks originate in positions advantageous 

 to the accumulation or retention of the moisture producing the weathering, 

 such, for instance, as that occupied by the detrital mat(H-ial at the base of the 

 slope or in the angle between overhanging blocks and the new dome surface. 

 The direction- of the cracks is determined by the configuration of the rock 

 surface, being approximately parallel to it, the departures from strict paral- 

 lelism being of such a nature as to omit ,angJes and other features of irregu- 

 larity. This parallelism to the surface is due to the expansive force acting 

 along lines of least resistance, which in this case are practically normal to 

 the outer rock surface. The slope of the surface is the governing function in 

 the removal of the scales because the component of gravity tending to dislodge 

 the separated scales is greater on steep slopes than on low, while the com- 

 ponent of the same force tending to counteract the expansion due to weather- 

 ing is correspondingly less on steep slopes, becoming greater as the angle of 

 declivity lessens. 



The paper was published in full in The Journal of Geology, volume xv, 

 pages 560-570, September-October, 1907. 



The next two papers were read without intermission and were discussed 

 together. They were 



BELATIOifS BETWEEN CLIMATE AND TERRESTRIAL DEPOSITS 

 'by JOSEPH iBARRELL 



• - [Ahsh-act]* 



Contents 



Page 



General introduction 616 



Part I. Relation of sediments to regions of erosion 618 



Part II. Relation of sediments to regions of deposition 610 



Part III. Relations of climate to fluviatile transportation ^ 620 



Summary and conclusion 620 



General Introduction 



The environment of the lands may be classified into three fundamental and 

 independent factors — the relations to the surrounding seas, the topography 

 which forms their surfaces, and the climates which envelop them — each of 

 major importance in controlling the character of the lands. . . . The third 

 great problem of terrestrial environment, the succession of ancient climates, 

 lags behind the other two in development, but is no less important in a com- 



• To be published In full in Journal of Geology, vol. xvi, 1908, beginning with no. 2. 



