^24 The Philippine Journal of Science 1923 



downpours 1 cause one to project these effects into the geologic 

 past. In December, 1921, Mr. H. P. Whitmarsh, former gov- 

 ernor of Benguet Subprovince, conducted Dr. W. D. Smith, 

 Mr. G. B. Moody, and the writer to an interesting locality west 

 of Baguio where an excellent and characteristic fauna of Vigo- 

 Miocene age was obtained. Governor Whitmarsh had pre- 

 viously sent to the writer some excellent specimens of Vicarya 

 callosa Jenkins, the finger post of the Miocene of the East 

 Indian Archipelago, from one of these localities. With this 

 evidence in hand an excellent geologic "datum plane of refer- 

 ence" was established in this region, and further data were 

 secured which gave fairly definite evidence that Baguio Plateau 

 had been developed by the wearing down of mountain systems, 

 probably formed at the close of the Pliocene, to a gently rolling 

 subdued topography which, in terms of Davis's geographic 

 cycles, would be described as being of early old age. Not only 

 was this surface apparently developed during the Pleistocene, 

 but also it was hoisted to its present position, 1,250 to 1,500 

 meters (4,000 to 5,000 feet) above sea level during middle or 

 late Pleistocene, faulted, and over much of the area of north- 

 central Luzon eroded so completely that there are now but few 

 isolated remnants of this once extensive low-lying country, 

 which probably covered the central portion of northern Luzon 

 during early Pleistocene. The deep erosion of Bued Canon, 

 Antamok Valley, and a large part of Agno River Gorge ap- 

 parently has taken place during late Pleistocene and Recent 

 times (Plates 1 and 2). 



A great annual rainfall, alone, is not sufficient to cause this 

 enormous erosion and the vast acceleration of geologic processes 

 in this interesting locality; but the great rainfall delivered as 

 torrential downpour, .of intensity unknown in temperate re- 

 gions, must be an important factor. This opinion is based 

 upon observation in western Washington in the vicinity of the 

 Olympic Mountains, the region of greatest rainfall in conti- 

 nental United States. This rainfall, however, while extremely 

 large, is distributed over a considerable period of time, and a 

 part of the precipitation during this time is not exceedingly 

 heavy. The results are that the western slopes of the Olympic 

 Mountains are covered with heavy forests of spruce, pine, 

 hemlock, and cypress, with an exceedingly heavy undergrowth 

 of tough shrubs with well-developed root systems. These root 



1 Annual average rainfall at Baguio, 4,598 



