Abstract
In this transaction, we have treated the "Sasu (Principal rafter) construction" of the south-western islands of Japan, including Osumi, Tokara, Amami and Loo-choo islands. The roof constructions of these islands are able to bs divided into 4 characteristic types, corresponding to the 4 types of the dwelling houses of this area. They are: 1) Sakishima type. The Sakishima islands are situated at the southern-most of Loo-choo. The roof construction of this district is "Nakabashira (central-post) construction", and not Sasu-construction, showing peculiarity among Japanese dwelling houses. 2) Okinawa type. From Okinawa to the southern parts of the Amami, a kind of Sasu construction is predominated. It is very simple and far from the perfect Sasu construction. It is supposed that this type was brought forth from the Nakabashira construction, being influenced from Sasu construction of the north province. 3) Amami type. This type is nearer to the perfect Sasu construction. From Tokunoshima to Oshima main island, we can find the construction of this type. 4) Hondo type. This is the perfect Sasu construction of the main Japan, including Kyushu proper. In Osumi, this type can be found. From architectural and geographical investigations, we can conclude that the Sasu construction of these islands was introduced from north, namely from Kyushu proper, and its prototype is Nakabashira construction.
