2 Art. 7.— S. Hirayau'a. 



Committee that it should take up this work in an extended form. 

 Fortunately the Committee approved my proposition, and the 

 work was begun in 1900 under my superintendence. 



The method of analysing is entirely that of Prof. Darwin. At 

 first, in order to reach the final results with the least labour and 

 smallest expense, his various methods were tried, and for some of 

 them the clerical labour was reduced by the use of the Japanese 

 abacus (a simple calculating machine). The method of stencils, 

 used in conjunction with the abacus, seemed promising, especially 

 when modified into the form drawn on tracing paper. But finally 

 I came to the conclusion that the last method by Prof. Darwin is 

 the most convenient, and it alone has been used. 



Although the work is done by the Geodetic Committee, the 

 Committee has no tidal observatory. Thus at the beginning of 

 the work the material was borrowed from the Land Survey De- 

 partment. At that time, the number of tidal observatories was 

 not so large as we have now. By and by more observatories were 

 established and our work became necessarily extended. In the 

 course of nearly ten years the frequent changes of the computers 

 made the progress of the work quite slow. 



This work relates only to the measurements of the marigrams 

 and their reductions, and we are not concerned at all with the 

 construction of the tidal observatories and the setting of the tide- 

 gauges therein, nor with the operations of the observatories. But 

 for the sake of convenience, some remarks on these matters are 

 included in the present Report, and for these we are indebted to 

 the information kindly supplied by the authorities of the observa- 

 tories. 



As the superintendent of the work, I desire to express my 

 sincere thanks to the following gentlemen who kindly supplied 



