Harmonie Analysis of Tidal Observations. 53 



AYUKAWA. 



Long. 141° 31' E., Lat. 38° 18' N. 



This is one of the permanent observatories belonging to the 

 Land Survey Department of the Army. The situation is on a 

 small bay of the north-eastern part of the Pacific coast. Accord- 

 ing to Drs. Honda and Terada and others, the length of the bay 

 is one and a half kilometres, and the mean depth of the water is 

 12.7 metres. The first registration was made on October 25th, 

 1891, and the observations were continued until Jane 11th, 1901, 

 without finding any serious obstacle, but about the latter date it 

 was found that a corner of the foundation was sinking and this 

 necessitated the moving of the building about three metres south- 

 wards from the old location. But after interruption of only eleven 

 days, the new series of registrations was begun, and continued 

 until June of 1905, when the old tide-gauge was replaced by a new 

 one. The latter is of the same pattern as the old one, and is 

 similar in every particular. 



The series on which the reductions were made are only five, 

 obtained in 1894, 1895, 1903, 1904 and 1906, and the results will 

 be found in the accompanying table. 



The highest high-water recorded here was 2.65, referred to 

 the zero-point of the instrument, and occurred on December 21, 

 1907. The lowest low-water recorded was 4.63, referred to the 

 same origin, and occurred on January 14, 1903. Thus the extreme 

 range is 1.98 metres. 



The height of the mean sea-level, referred to the zero-point 

 of the instrument, is obtained for each year-series as follows: — 



1894 3.654 



