SECONDARY UNDULATIONS OF OCEANIC TIDES. 1 3 



made by his portable tide-gange ; the duration of observation 

 was generally a day and night. 



In addition, the records obtained by Lord Kelvin's tide- 

 gauges set up at the following ten stations were made use of : 

 Hanasaki in Nemuro, Ayukawa in Eikuzen, Kushimoto in Kii, 

 Hososhima in Hiuga, Fukahori in Hizen, Tonoura in Iwami, 

 Wajima in Noto, Iwasaki in Mutsu, Kelung and Takow in 

 Formosa. 



The topographs of these stations and the records are given 

 in the plates annexed to the present paper. 



From the thorough study of the numerous records obtained, 

 we may infer the following general conclusions : — 



1. On the Pacific coasts free from any inlet in the coast 

 line, the secondary undulation is very inconspicuous, and of a 

 quite irregular nature. 



2. On the Japan Sea side, the secondary undulation on 

 open coast is conspicuous, though not regular. 



3. In a bay of considerable area, or a shallow bay com- 

 municating with the ocean by a narrow opening, the secondary 

 undulation is in ordinary cases inconspicuous. 



4. In a deep bay or estuary, the breadth of which is not 

 large in comparison with its length, the secondary undulations 

 are most pronounced. 



5. In bays or on open coasts, which are not far from each 

 other, common undulation is often observed. 



6. The secondary undulations in many bays often change 

 their periods continuously, through certain ranges. 



7. In some bays, the periods of the undulation are fairly 

 constant. 



8. In many cases, the same trains of secondary undula- 



