This paper has investigated the displacement of the needle threads twists of the stitches which were made by one-needle lockstitch machine (forward or backward stitching), two-needle lockstitch machine and zigzag seamer. In order to determine easily the number of twists in sewed threads, a three piled thread consisting of three single yarns dyed in diffe rent colors were used as needle threads. The results obtained were as follows :
(1) Remarkable increases of sewed thread twists on reverse sewing by one-needle lockstitch machine and on the left needle of two-needle lockstitch machine and the change of the twist in the zigzag seam are caused by the effect of the edge of the needle eye.
(2) The needle thread breakage and irregular stitches occur owing to the remarkable decrease of the twists in the threads under the sewing operation on reverse sewing of one-needle lockstitch machine and on the left of two-needle lockstitch machine by the edge effect of the needle eye.
(3) The displacement of the thread twists by the edge effect of the needle eye in the zigzag seam is largely dependent on the angle (θ) between needle eye direction and the needle thread, and it is also influenced by the thread tension.

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ミシン針の針穴によるEdge Effectによる縫糸の撚移動の原理を明確にする.このため, 検撚器を改良したワイヤー縫糸摩擦装置を試作し撚移動の機構をモデル化し実験した.結果は次のとおりである.
1.撚移動は2点で固定された縫糸に中間にあるワイヤーが摩擦して移動するとき, ワイヤーを境に縫糸は同方向に回転し一方に加撚, 他方に解撚がかかる仮撚の機構と同じである.
2.加撚するか, 解撚するかは縫糸の撚角α, 縫糸とワイヤーの交叉角βと, ワイヤーの摩擦の方向に影響される.
3.撚移動の量はワイヤーの交叉角βが縫糸の撚角αと同じか近いときに多く, ワイヤーの交叉角βが撚角α+90゜を超えたときは少ない.

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縫糸の種類の違いによる撚移動の影響を調べるため, 現在市販されている主な縫糸について, 1本針本縫ミシンで前進縫および後進縫を行い, それぞれ糸道上の糸の撚数と強度および可縫長を測定して比較した.また, 後進縫での可縫性の改善策について, ミシン針へ縫糸をS字状にまわして通す, 針取り付け角度の変更, およびS撚の縫糸を使用して実験した結果, つぎのことがわかった.
1) Z撚の縫糸を使用した後進縫では, 撚数残存率, 強度残存率, 可縫長の結果を総合して適性をみると, フィラメント系縫糸<スパン系縫糸<コアスパン縫糸の順となった.
2) Z撚の縫糸を使用した後進縫での糸切れは, ループの糸割れのところにかまの剣先が入って糸切れになる場合もみられた.
3) ミシン針に縫糸をS字状にまわして通すことにより撚移動を減少させ可縫長を増加させることができた.
4) 撚数の変化により, ミシン針にできる縫糸のループ面が傾く.そこで, このループ面がかまの剣先の方向と直角になるようにミシン針の取り付け角度を変えることにより, 可縫長を増加させることができた.
5) ミシン針の取り付け角度を変え, さらにS字状にまわして通すことにより, 連続後進縫での可縫長を著しく増加させることができた.
6) 連続後進縫にはS撚の縫糸が適している.これはS撚の縫糸が, 針のEdgeと縫糸との交叉において, Edge Effectの影響を受けにくい撚角度をもつことによる.

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Rice is a main product of all the agricultural regions of Japan and the economic nature of its production has long been defined as “self-sufficient”. However, in accordance with economic development and population growth, the common nature of “self-sufficiency” in Japanese rice production seems to be loosening. The inter-regional supply-demand relationship of rice diverges, reflecting the regional specialization of economic activities in the progress of the national economy. It seems to represent the differentiation in the role of the paddy farming which each of the agricultural regions performs. It would be reasonable, therefore, to reconsider the nature of paddy farming for every agricultural region.
The present report intends to characterize each of the rice producing regions by pursuing its contribution to the national market of rice during the past 80 years. Three indices-supply-demand coefficient, land productivity and labourcost-productivity ratio-were calculated over the four periods of 1883-1887, 1918-1922, 1937-1941 and 1958-1962 for each of the 45 prefectures.
The shift in these indices proved to represent the regional and historical movement of paddy farming. The 45 prefectures would be grouped into the following four main types; Types A, B, C and D.
Type A……Commercial Production Region. The regions falling into this category are characterized by the rapid increase in supply coefficient, land productivity and labourcost-productivity ratio. They apparently perform the role of rice supplying area for the national market, and are seen mainly in the north-eastern part of Japan.
Type B……Subsistent Production Region. Land productivity and labourcost-productivity ratio have emerged to decrease in these regions. Supply coefficient has also decreased and reached the level of subsistent production. That is, the supply capacity of rice is not so great as before, and rice is produced mainly for the local market. In these regions, the economic activities are carried on by non-agricultural industries, and the contribution of agriculture to them is definitely limited. These regions appeared in the central and western Japan, especially in the neighbourhood of the industrial regions described below.
Type C……Big-Demand Region. These regions are represented by the extra-ordinary decrease in land-productivity and labourcost-productivity ratio, and the increase in demand coefficient. The leading industrial regions of Japan including Tokyo, Kanagawa, Aichi and Osaka belong to this category. These regions are the principal national market of rice, which is formed by the concentration of population and the rapid development of industrial activities in these regions. In the late 19th century, they had the highest level of land and labour productivity of rice.
Type D……Small-Demand Region. All of the indices have consistently remained at the relatively low level through the four periods in these regions. They are under-developed areas of agriculture characterized by the lowest productivity. The south-western part of Japan is a typical case of this category.

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