58 



2400 



Physiography 



Figure 55. Topographic profiles made by compositing sections of a record drawn by the precision depth recorder 

 (Luskin, Heezen. Ewing, and Landisman, 1954). The original, recorded on 19-inch newspaper facsimile tape, was photo- 

 graphed, cut into sections, and assembled as shown. The 19-inch tape width represents only 400 fathoms (2400 feet): 

 thus, as the water deepens the scale changes from 0-2400feet to 2400-4800 feet to 4800-7200 feet, etc. In 1. note 

 deep sagpond at west side of San Diego Trough. In 2, the crossing of traces at east side of San Clemente Basin is re- 

 sult of side echoes from steep east slope. In 3, the scattered echoes above bottom of Cortes Bank represent schools 

 offish; two partial traces beneath bottom are double and triple echoes. Record from Chinook Expedition, Scripps 

 Institution of Oceanography. 



