Secondary Undulations of Oceanic Tides. 123 
are different for different bays and gulfs. Ferrei* attempted 
to explain some irregularities of oceanic tides, by considering 
oceans as making stationary oscillations like the seiche in 
lakes. Recently R. A. Harris f, acting on a similar theory, 
constructed a co-tidal chart of the world. According to his 
view, all the water on the globe is divided into several 
distinct portions, each of which has the period proper to its 
own stationary oscillation. This point has been subjected to 
criticism by G. H. Darwin. Harris applied his theory also 
for the explanation of tidal phenomena in many bays and 
straits, the standing oscillations of which are forced by tidal 
waves incident on their mouths. He has considered, however, 
exclusively the forced oscillation with diurnal and the semi- 
diurnal periods, and has not considered those oscillations 
peculiar to each bay. 
Now, according to our view, any bay or gulf, either small 
or large, may be put into a standing oscillation, if it be excited 
by the incident waves of a proper period. If the proper 
period of the bay happens to coincide nearly with one of 
the tidal components, that component will become more or 
less prominent, according to the degree of proximity of 
the proper and the exciting period. In this way, tides o£ 
the superior orders or indefinite components arising from 
meteorological causes, may sometimes become prominent 
in a bay, though almost insensibly small in the open sea. 
Moreover, the case may occur in which a solitary wave of 
wide extent, caused by some disturbances either meteorological 
or geotectonic, excites the oscillation of a Jong period proper 
to a bay. These oscillations in a bay will more or less deform 
the tidal curve, and cause an anomaly of the tides peculiar to 
the bay. Believing this view correct, the proper periods as 
given by our formula were calculated for different bays or 
gulfs, which are notorious for abnormal range of tide, and 
also those for which some remarkable irregularities of the 
tide were observed in the mareograms given in the Report of 
the Krakatoa eruption. The results of these calculations 
were found to confirm the above views. Some of the results 
will be given below. 
(i.) Bay of Fundi/, Canada. — Near the end of this bay, 
spring-tides range 15 m., while near its entrance the rise is 
only 2'5 m. to 3'5 m. For the calculation, the mouth-line 
was taken from Cape Cod to Cape Sable, and the end of the 
bay was taken at Port Greville. Then 1 — 4:60 km. h = 141 m. ; 
* Ferrei, {i Tidal Researches," Rep. Coast and Geodetic Survey, 
Washington, 1874. 
f R. A. Harris, * Manual of Tides.' 
