[ M ] 
VIII. On the Secondary Undulations of Oceanic Tides. (An 
Abstract.) By K. Honda, T. Terada, and D. Isitani, 
Tohio Imperial University, Japan *. 
[Plates I.-VI.] 
Contents. 
§ 1. Introduction. 
2. General Conclusions. 
3. Results in Detail. 
4. Experiments with Models. 
5. Formulae for Calculating the Periods of the Oscillations in Bays. 
6. Method and Results of Determining the Period of Oscillation by 
Calculation. 
S 7. Sea- Waves and Secondary Undulations. 
§ 8. Oscillations of Large Bays and Anomaly of Tides. 
§ 1. Introduction. 
fT^HE tidal curves obtained by self-recording tide-gauges 
JL are often accompanied by a peculiar zigzag or secondary 
undulation of considerable amplitude, which becomes per- 
ceptible at a station situated in a bay or an estuary. This 
fact seems to have been noticed by many earlier observers. 
Without discussing all these earlier contributions to 
the subject, we will briefly mention some comparatively 
recent valuable investigations. David Milne f discussed the 
remarkable undulations of July 1843 which were noticeable 
on the coasts of Great Britain, and ascribed their origin to 
the storm then prevailing in that district. Admiral Smyth J 
referred to the same phenomenon observed at Mazzara, where 
it has long been termed Mirabia or Marrobbio. Sir George 
Airy§ believes that the secondary undulation is the seiches 
•between the Sicilian and African coasts. This phenomenon || 
has also been observed on the coast of Italy and the northern 
* Communicated by the Authors. 
+ D. Milne : "Ou a remarkable Oscillation of the Sea observed at 
various Coasts of Great Britain," Trans. Roy. Soc. Edinb. 1844. 
% Smyth : Memoir descriptive of the Resources, Inhabitants, and 
Hydrography of Sicily ; London, 1824. 
§ G. Airy : " On tides in Malta," Phil. Trans. Roy. Soc. London, 
clxix. 1878. 
|| G. Grablovitz : u Ricerche sulle maree d'Ischia," Rend. Ace. Lincei, 
vi. 1890. " Sulle osservazioni mareograhche in Italia e specialmente su 
quelle fatte ad Ischia," Attidel 1. Congr. ItaL, Genova, 1893. R. Sieger : 
*• Niveauveranderungen an Skandinavischen Seen fund Kiisten," Verh. 
9ten Deutsch. Geogr., Wien. E. Bruckner : " Ueber Schwankungen der 
See und Meere," Verh. 9ten Deutsch. Geogr., Wien, 1892. 
