[Illustration: COURTESY OF E. L. KRINOV Workmen excavating one of the large craters formed by the impact of the Ussuri meteorites.] Most impressive of all, though, were the numerous meteorite craters ranging in size from small bowl-like features to a basin more than 28 yards across and over 6 yards deep—a depression large enough to hold a two-story house. The investigators recovered many fragments of the iron meteorite that had broken to pieces not far above the earth’s surface and had peppered the area of fall with high-speed meteoritic “shrapnel.” With their meteorite recoveries and photographs of the cratered area, the members of this first expedition returned to their respective towns and began a campaign by letter and wire to interest the Moscow office of the Academy of Sciences of the U.S.S.R. in making a full-scale investigation of the Ussuri fall. The officials of the Academy decided at once to send a special scientific expedition to the site of the meteorite fall. A member of this later and better-equipped expedition compared the Ussuri crater field to a bombed-out area. In fact, some of the meteorite specimens were fragments that closely resembled pieces of shattered shell-casing. The edges of these fragments were jagged and bent, and their surfaces, which often displayed a rainbow-colored sheen, were grooved and scarred by impact against the hard rock underlying the region in which the crater field had been formed. In rare instances, the investigators noted spiral twisting of the fragments, an indication of the unusually violent disruptive forces to which they had been subjected at impact. The scientists found several instances in which fist-sized meteorite fragments had actually penetrated into or through standing tree trunks, either becoming imbedded in the wood or driving a hole right through the trunk. [Illustration: COURTESY OF E. L. KRINOV A nickel-iron meteorite from the Ussuri fall imbedded in the trunk of a cedar tree.] Many whole individual meteorites also were recovered. These were almost always covered by a thin, smooth “glaze” known as _fusion crust_. This crust forms on the surface of a meteorite as it plunges rapidly through the air. The heat generated during its flight causes the outer “skin” of the meteorite to melt. Later, when the mass has cooled off, the thin coating of melted material hardens, forming a rind or crust.