SECONDARY UNDULATIOMH OF OCEANIC TIDES. 



35 



GO"" for this mode of oscillation falls fairly within the range of 

 the observed values. 



As to the secondarv undulations of shorter periods, it may 

 be generally observed that for each of the four stations, con- 

 spicuous waves with the periods 8'"-lS'" are found very fre- 

 quently. Periods of 20"-25™ and 32"'- 30'" are also met witli. 

 For Iniazu and Kishiwada, waves of 8" -18'" periods occur very 

 conspicuously ; and apparently idential trains of waves may 

 often be traced at the two stations. Comparing the records of 

 the four stations on the same days, waves common to different 

 stations are often recognized. For examples : — 



Whether these waves are due to some higher modes of stationary 

 oscillation of the sea, or they are merely progressive waves 

 generated by meteorological or other causes is a question still 

 to be solved. 



Waves with periods shorter than about 8'" are also generally 



