232 ANNUAL EEPOKT SMITHSONIAN INSTITUTION, 1932 



rence of such rock in the walls is, however, perhaps accidental ; i.e., 

 it may have been thrown up by the impact and is not in situ at all. 

 It will be seen that the age indications are very vague indeed. 

 The author is, however, of the opinon that the fall took place a very 

 long time ago and that the age of the craters must be reckoned in 

 terms of thousands of years. 



CONCLUSION 



This description would not be complete without some reference 

 to the meteorite craters at Canyon Diablo (or Coon Butte) in Arizona, 

 and near the Tunguska Kiver in Siberia. The Canyon Diablo Crater 

 is, of course, nmch larger than the largest at Henbury, being some 

 three-quarters of a mile in diameter and with a depth of 570 feet 

 from floor to rim. There are, however, many points of similarity 

 between the tAvo occurrences. Doctor Merrill's general description ^ 

 of the nature of the Canyon Diablo Crater could easily be applied to 

 the larger ones at Henbury with but fevv' modifications. Other 

 notable points of similarity are the nature and occurrence of the iron 

 fragments and the presence of fused country rock. Dissimilarities 

 which may be particularly noted are the large number of craters in 

 Central Australia compared with the single large one in Arizona; 

 also the oval shape of the main crater at Henbury. 



Fewer details are available concerning the craters in Siberia. 

 Apparently the largest crater is 150 feet in diameter and about 

 12 feet deep, and it is interesting to note that digging in one of these 

 craters to a depth of 30 feet failed to reveal any meteoric material. 

 The largest of the Siberian craters is thus much smaller than the 

 Main Crater at Henbury, so that it is possible that meteoric material 

 at Henbury may be buried to a very considerable depth. A bore 

 sunk in the Canyon Diablo Crater reached a hard mass at about 1,376 

 feet. It is, however, still uncertain that this is the main bulk of the 

 meteorite. 



Bearing these facts in mind the author would suggest that further 

 work at Henbury should obviously be along the following lines: 



(1) That a wider survey of the area be made. Owing to difficul- 

 ties of transport and lack of the necessary time only a comparatively 

 small area was examined. The author believes that a wider survey 

 may lead to the discovery of more craters, some of which may be of 

 considerable importance. 



(2) That use be made of geophysical methods in an attempt to 

 locate the position of masses of meteoric iron in any of the craters. 

 The locality, the type of country rock, and the natui'e of the material 

 to be located seem most ideally suited to the use of such methods. 



6 Merrill, G. P., Smithsonian Misc. Coll., vol. 50 (Quarterly Issue, vol. 4), p. 461, 1908. 



