INVESTIGATION VERSUS PROPAGANDISM 313 



tract ; the formation back of the ridge — more or less contemporane- 

 ously with this — of a more extensive flat area with boggy tendencies, 

 the most significant feature of which is an indurated black sand, 

 from which pebbles ranging up to *' cannon balls " were later derived 

 and borne into the lower and upper fossil-bearing layers (Sellards' 

 No. 2 and No. 3); the development of the drainage system of 

 Van Valkenburg's Creek, partly in the one and partly in the other 

 of these two upland formations; the excavation of the creek 

 trench to a breadth and gradient suitable for the beginning of 

 aggradation; the^first stage of aggradation (Sellards' layer No. 2); 

 and the second stage of aggradation (Sellards' No. 3). 



On the basis of this analysis, a hypothesis was proposed which 

 seemed to reconcile some of the apparently conflicting imports of 

 the fossils in the lower and upper parts of the creek deposits. It 

 postulated that the oldest extinct mammals came into the region 

 as soon as it emerged from the sea, and were buried in the hollows 

 and flats of the ridged tract, and more especially in the poorly 

 drained, flattish area lying west of the Vero Ridge, whence at some 

 time notably later they were carried into the creek deposits much as 

 the black pebbles from the indurated sandstone of the same area 

 were found to have been. 



No time was available during the first conference after this 

 hypothesis was formulated for testing it, and it was offered in this 

 state in the first symposium as a hypothesis of reconciliation, and the 

 earliest opportunity sought to put the hypothesis to the test. On 

 his second visit. Dr. Chamberlin found the bog deposits back of 

 the ridge essentially barren of fossils, suggesting conditions either 

 inhospitable to life or unfavorable for its preservation. In his 

 contribution to the second symposium the part of the hypothesis 

 relating to the bog deposits was therefore frankly laid on the 

 shelf; nor was the alternative phase which made the upland marl 

 beds of other parts of the tract the source of the older fossils of the 

 creek deposits further urged, because fossil-bearing deposits of this 

 kind were not found in available situations, though they occur 

 elsewhere. The part played by this stage between the retreat of 

 the sea and the aggradation on the bottoms of Van Valkenburg's 



