2l6 



PRINCIPLES OF STRATIGRAPHY 



region, where their period is probably not over 8 to 1 1 seconds, and 

 their length from loo to 200 meters. 



Depth of Wave Activity. The orbital radius of wave particles 

 in the open sea decreases downward in geometrical progression, so 

 that for each descent in depth equal to 1/9 of the wave length the 

 diameter of the orbit decreases by one-half. (Kriimmel-42 : (5.) 

 Thus : 



At twice the depth of the wave length the orbital diameter will 

 part of the wave height at the surface. A wave of 90 



be — ^- 

 262,144 



meters in length and 3 m. high (a not uncommon size in the open 



ocean, during strong winds) will show the following decrease of 



the orbits in which the particles move. 



Thus with a wave length of 1,500 ft. and a height of 50 ft. the orbital 

 motion, which at the surface is 50 ft., will at a depth of 1500 ft, 

 be 50/512 ft. or 1. 17 inches, while at a depth of 3,000 ft. (500 fathoms) 

 it is 50/262,144 ft. or 0.0023 of an inch, or 0.058 millimeter or 

 practically nothing. At 100 fathoms, a wave 600 feet in length on 

 the surface and with a height of 30 ft. {i. e. an orbital diameter 

 (2p) of 30 ft.) will be represented by orbital movements of 0.7 inch in 

 diameter. 



