Nevertheless many valuable theories being proposed, many simple points of the course of sintering are yet unsettled. For instance, the inner structure of a sintered bond between two particles, and whether pores do in general become spherical rapidly or not do so much slowly than the shrinkage change, etc.. In this experimental study, placeing spherical metal particles (silver, gold and copper) in a row, or in one layer on un-reacted plates, and then heating them in various conditions, the changes of bonds between particles are observed from many sides to reveal these unresolved points in detail. Main results are as following : A-1) The inner-structure of a sintered bond (copper or silver) seem to be not always such simple, as considered in previous papers, but more complicate porous structure in the begining-stage of sintering. A-2) In heating one layer of silver, copper particles, each growing-rate of bonds are also varied at eachh contacted points. A-3) The bridge-bond is able to be formed between particles previously separated. A-4) Resulting from deformations of silver particles sphapes after heating, variations of both evaporation-rate and the diffusion of evaporated atomes are observed under various conditions of placeing. A-5) With variations of arrangements of particles, the growingrate of bond, the sintering process itself is varied such as observed in the results of sintering gold-silver particles. A-6) Heating copper particles, previously oxidized on the surface, in the reducing atmosphere, the sintering rate are accera-ted more rapidly than in fresh particles.
From these results, it is appointed that the elementary process of sintering must be more complicate and moreover, the effect of evaporation and condensation on the essential process of sintering more important than hitherto considered. Nevertheless, compacting and succeedingly heating silver spherical particles, shrinkage change is always occured, it is not observed when these powders are heated after placeing them in a row on porcelain plate. The sum of distances between centers of spherical particles are not shrinked, but expanded even after sintering.
More over, the pore, surrounded by these three particles, do become not spherical even after sintering for longer time.
From these results, it will be suggested that the shrinkage change, which has ever been regarded the effective parmeter of sintering progress should not be always related with the growing-rate of bond directly.

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