226 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 2 



the brim and in appearance entirely resembles one of the low eleva- 

 tions which foot the adjacent qnartzite ridges. However, as soon 

 as the rim of the Main Crater is reached the effect is startling. A 

 huge depression is seen, 50 to 60 feet deep and of oval shape, being 

 about 220 yards in its longest axis and 120 in its shortest. Mulga 

 trees and grasses cover the floor, which consists of cracked mud cakes 

 resembling the floor of a " clay pan," and which apparently retains 

 water for some time after rain (pi. 1, fig. 2). The crater walls 

 are generally steep near the summit (pi. 2, fig. 1), but at lower 

 levels slopes of talus reach more gently in toward the center of the 

 depression. The height of the walls from floor to rim is on the 

 average from 40 to 50 feet, but it is evident that they have formerly 

 been considerably higher than they are at present. The walls them- 

 selves consist for the most part of shattered and crushed fragments 

 of sandstone and slaty rock varying in size from the finest powder 

 up to large blocks several cubic feet in volume. In one or two 

 places slaty rock, very much shattered, has the same dip as the 

 country rock and seems to be in situ in the walls. This point is of 

 interest and will be mentioned later. 



Adjacent to the Main Crater and lying to the south of it are two 

 other craters, the larger of which may be called the Water Crater. 

 A watercourse having broken through the walls, an inflow of water 

 evidently results after rain. This water is apparently preserved for 

 some weeks after the rain has fallen. This has led to the greater 

 development of vegetation, and both mulgas and other acacias have 

 grown in this crater to a size unusual in the area. One or two trees 

 (apparently Acacia salicina) have a height of about 45 feet, the 

 diameter of the trunk being up to 21 inches. In shape the Water 

 Crater is roughly circular with a general diameter of about 80 yards. 

 The walls vary in height from 12 to 25 feet, reaching the maximum 

 at that point where they divide the Main Crater from the Water 

 Crater. The general description of the walls of the Main Crater 

 may be applied to the walls of this and all the other craters. 



A summarized description of the craters follows (fig. 2) : 



No. 1. Somewhat indefinite owing to the complete removal by erosion of the 

 crater walls. An isolated circle of mulgas with a " clay pan " floor, together 

 with the presence of meteoric iron fragments surrounding it, leaves little doubt 

 in the author's mind that this is a former crater. Probably originally circular, 

 with a diameter of possibly 25 yards. 



No. 2. Similar to No. 1, but somewhat larger. Circular, with diameter of 

 possibly 30 yards. 



No. 3. A very well-defined crater, circular, with a diameter of about 45 yards. 

 General height of walls 10 to IS feet. Ab<iut 160 iron fragments, many being 

 very small, were found surrounding this crater, and of this number about four- 

 fifths were lying to the west. A large jagged piece, weighing 13 pounds was 

 found within the crater walls. Another large mass was found in a position 



