10 Art. 7.— S. Hirayama. 



instrument referred to the bench-mark, and in this column the 

 positive sign indicates that the bench-mark is lower than the zero- 

 point, and the negative the contrary. In the column H^ the sum 

 of Hi and H2 is given ; obviously it is the required height of the 

 zero-point of the instrument, referred to the mean sea-level of the 

 Bay of Tokyo. 



station Hj H... H, 



Takaw — — — 



Kiirun — — — 



TTi fn m 



Fukabori 3.U47 1.164 4.211 



Hosojima 2.526 1.740 4.266 



Tonoura 2.792 1.125 3.917 



Kobe — — — 



Kushimoto 3.333 0.515 3.848 



Wajima 2.704 1.239 3.943 



Aburatsubo 3.635 -0.039 3.596 



Yokohama — — —1.477 



o 



Iwasaki 3.244 2.229 5.47c) 



Ayukawa 2.769 0.759 3.528 



Otaru — — — 



Hanasaki — — — 



The Determination of the Distance of the Surface 

 below the Zero-Point. 



The tide-gauge is provided with two pencils, besides the one 

 which actually draws the tidal oscillations; we can easily see them 

 at the right-hand side of the right-hand scale in the figure of the 

 instrument. Of course, these pencils may be moved up or down 

 as much as we please, so that to adjust the distance between them. 

 In this way, when the clock starts, the two straight lines which 



