SECONDAKY UNDULATIONS OF OCE.\NIC TIDES. 107 



with one of the semidmrnal tides, though the tidal phase is 

 slightly retarded toward the end of the Bay and therefore the phe- 

 nomenon can not be wholly attributed to the standing oscillation. 



(&) Bay of Bengal. Near the mouth of this bay, the tidal 

 range is small, being less than half a meter at the southern 

 coast of Ceylon, while in the bay, the range is 1-2.7 m., in- 

 creasing abruptly near the end of the Bay. Since the tidal 

 phase is nearly the same for the great part of the bay, principal 

 part of the tide in the Bay is probably due to the standing oscil- 

 lation of it. Taking the mouth line from the eastern coast 

 of Ceylon to the northern end of Sumatra, and the end of the 

 Bay at Akyab in Burma, we obtain /= 1500 km. and A == 1950 m., 

 which gives 2'=12.0'\ coinciding with the period of semidiurnal 

 solar tide. 



(c) Madura Strait, Java. Mareograms of Ujong Sourabaya 

 and Karang Kleta reproduced in the Krakatoa Eeport of the 

 British Association show very marked irregularities of tide in 

 the narrow strait of Sourabaya, which connects the end of wide 

 Strait of Madura with the Java Sea. Since the width of the 

 Strait of Sourabaya is extremely small in comparison with that 

 of the Madura Strait, we may consider the latter strait as a 

 rectangular bay, having its end inside the former strait. The 

 effect of narrow opening at the end of a bay is only to shghtly 

 reduce the effective length of the bay, or in other words to 

 shorten the period of oscillation by a small amount. The length 

 of the Madura Strait, considered as a bay is about 1(30 km. 

 As for the mean depth of the basin, no chart of a sufficient 

 scale is at hand, so that we may only roughly estimate it from 

 the data collected from different maps'-' available. In any case, 



*) Maps of Encyclopedia Britanica, Bergbaus' Physikal. Atlas, etc. 



