Page 545 



ECHO SOUNDING 



571 



■HIOTMH 



c 



Figure 117. — Types of bottom relief shown vividly in fathograms of the 808 Fathometer. 



A shows hard bottom protruding through soft bottom. B shows silt-filled depressions. C shows rugged bottom and is an inter- 

 esting example of multiple echoes. The second echo is marked 7, the third is marked 8, and even the fourth is visible at 9. The trace 

 above each shoal is from kelp. Note that the scale of A and £ is six times that of C. See text for number references. 



