著者

宮川 陟

出版者

日本計量史学会

雑誌

計量史研究 (ISSN:02867214)

巻号頁・発行日

vol.18, no.1, pp.8-26, 1996

参考文献数

16

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Based on a survey of the Mozu Otsukayama burial mound, I considered how the mound was built. I found that earth was heaped in a cone shape with a diameter of about 12 meters, or else as a trapezoid with earth packed in layers based on a level of about 1.3 m. The writer calls this 12 meter pile a hiro, and the 1.3 m height as being at eye level. The structural plan discussed to this point is a study for the reconstruction of the technology and techniques to construct a keyhole-shaped burial mound. Based on this assumption, sufficient land was allotted on the school grounds for a three-module type Ozono burial mound and a 1/8 scale Daisen burial mound, which is a large, eight-moudule type mound. The course and results of this experiment were described. The only approach available to actually allot land for the structural plan of a keyhole-shaped burial mound was to use a leveling string to accurately determine the basic main line and the lateral line that meets the main line at right angles. To obtain a right angle, strings of a ratio of 3 : 4 : 5 (corresponding to the Pythagorean theorem) Were used. To draw a big are on the ground, a string or rope measured to the radius of the intended are is usually used as a compass, However, the experiment confirmed that, with a large are of radius 15 meters, the string stretches like rubber however hard the strands are twisted together, making it impossible to draw an accurate are. We confirmed that an are can be drawn with a very small error by stretching leveling strings across a radius from the center of a circle, measuring the radius to be obtained by connecting the hiro measuring rods, and then by connecting the polygons. For the "module" for each portion of the mound, the method we used was to simply allot a length of the module in the same way by connecting hiro measuring rods. It was not at all necessary to draw a complicated mesh of square divisions. This method produced good results, with a total error of about 0.3% to 0.5%. The method used resulted in virtually no error produced by rope stretching. It probably had further significance, namely the use of this method constituted a repetition of the magical act of inscribing spiritual power from the ground by allotting land for the burial mound using the hiro, which symbolizes a chief buried in the mound. From the land allotment experiment, which we performed twice, we demonstrated that the structural plan and its execution are a technical system refined to a very simplified technique in which land allotment for a burial mound can be made on the spot, even without a "design drawing, " provided the numerical value for one module is decided beforchand, keeping in mind the allotment based on square division, which is a master plan for building a keyhole-shaped burial mound and which was discussed in Part (1) of the paper.