HENBURY METEORITE CRATERS ALDERMAN 231 



peded to a greater extent by air resistance, and would thus fall short 

 of the larger masses. This would then suggest a movement from 

 west to east. 



It is, of course, difficult to realize how a huge mass of iron would 

 behave under the conditions which must have prevailed when the 

 meteorite landed, but one would expect that the impact would cause 

 the bodies to be at least partly shattered. This idea is supported 

 by the shape of many of the fragments. The absence of the minute 

 '• pitting " over the whole or part of the surface of a great number of 

 the fragments also suggests that the period of their separate existence 

 must have been a very short one. 



AGE OF THE FALL 



Judged from human standards, the age of the fall must be con- 

 siderable. There are many indications that it is by no means recent, 

 but one can not as yet make any positive determination of its age. 

 Summarized, these indications are : 



(1) The complete oxidation and disintegration of certain of the 

 iron fragments. These and other geological processes proceed with 

 extreme slowness in a climate of such aridity. The average annual 

 rainfall for the locality is probably about 6 inches. Some frag- 

 ments were found which consisted entirely of scaly ferric oxide. 



(2) The presence of fully grown mulga and Acacia sal'icina trees 

 would put a certain minimum on its age. The author believes, 

 however, that generations of trees have lived and died in the craters 

 since the meteoric fall. The trunks of many dead mulgas are to 

 be seen everywhere, some apparently of great age. The mulga is a 

 notably slow-growing tree. 



(3) Inquiries from aborigines of the district gave negative results. 

 None of them had any ideas as to the origin of the craters. If the 

 fall had taken place since the human occupation of the area, one 

 would have expected accounts of such a notable happening to be 

 handed down from generation to generation, and that also the 

 locality would be regarded with superstitious awe. The aborigines, 

 however, showed no interest in the craters. 



(4) In the walls of the Main Crater some shattered slaty reck has 

 the same dip as that of the surrounding country rock and may 

 j)ossibly be in situ. This is several feet higher than the general 

 level of the plain, and may indicate that the level of the plain has 

 been reduced by several feet since the formation of the crater, which 

 in such a climate would require a very long period of time. The 

 rock in situ in the crater walls would have been protected from 

 erosion by the superincumbent layer of fragmentary material which 

 formed the upper part of the previously higher walls. The occur- 



