16 -Art. 7. — S. Hirajama. 



graduated to half millimetres, is used, so that v.dien we estimate 

 each division to its tenth part, the actual height of the water is 

 measured to a millimetre. But as one-twentieth is only the ap- 

 proximate value of the scale of the instrument, it is necessary to 

 multiply the reading by the ratio, the assumed scale by the work- 

 ing scale, in order to obtain the true height of the water. In our 

 case, we did not multiply each reading by this ratio, as our object 

 was to derive the harmonic constants and the mean sea-level; so 

 only the results of the analysis are reduced to the working scale. 



The measurements on the marigrams provided by the tem- 

 porary office for constructing the harbour of Kobe are different 

 from the above, as the curve is drawn on a sectioned paper, pro- 

 perly scaled in hours and feet. The height of the water is read 

 here to the one-hundredth part of a foot. 



The observations at the port of Yokohama were read to the 

 one-tenth part of a sliakii. 



All these results are entered in the form S. Each series of 

 S-sheets begins at the beginning of each corresponding year and 

 extends to the end of the year. 



Harmonic Analysis. 



The method of analysis is entirely that of Professor George 

 H. Darwin: the reduction forms are made according to him. The 

 rearrangements of the observed heights from the form S for variety 

 of time to be reckoned for have been made by means of strips 

 with short pins on their under sides, so that they can be stuck on 

 to a drawing board in any desired position, according to the guide 

 sheets prepared by Professor Darwin. In this work the Japanese 

 abacus, a very simple but exceedingly convenient computing 



