42 THE PROBLEM OF ANTIQUITY OF MAN IN AUSTRALIA 
there are large shell middens forming a series of heaps and mounds 
from 20 to 30 ft. high which extend for several hundred yards 
(Jackson, 1902). 
Middens several acres in extent and up to 10 ft. thick composed 
of oyster and other shells have long been known in ‘Tasmania. 
Noetling (1910) caleulated that the time required for them to 
accumulate is 5,000 to 7,000 years. His calculations are based on 
assumptions, which may or may not be approximately correct, 
concerning the number of natives formerly inhabiting ‘Tasmania, 
and shellfish consumed per head per day. David (1923) thought 
that a considerably longer time is indicated. 
At the Reedbeds, Fulham, near Adelaide (White, 1919; 
Howchin, 1919), and at Shea’s Creek, near Sydney (Etheridge 
and others, 1896), artefacts have been found near the coast in 
swamp deposits or estuarine beds a few feet below sea level.” Both 
deposits are considered to be geologically recent. 
The only records of implements in river terraces are those of 
Ferguson (1894), who found some in terraces a little above the 
level of the present streams in the valleys of the Hopkins and 
Wannon Rivers, near Wickliff, Victoria, and the artefact found 
near the Keilor skulls. 
Large areas of Central Australia are covered with ‘‘gibber,’’ 
that is, with wind-worn fragments of hard rock derived from 
strata disintegrated by subaerial denudation. Among the gibber 
stones Howchin (1921) found flaked pieces of siliceous rock with 
patinated surfaces; he regarded them as ancient artefacts of an 
earlier cultural phase than that of modern aborigines. Wood Jones 
and Campbell (1925) and Tindale (1932) have furnished sound 
reasons for believing that the flaking was fortuitously caused by 
natural agencies. 
Bennett (1867) recorded that sandstone with grooves similar to 
those made on grindstones or outcrops of sandstone by aborigines 
when sharpening their stone axes was found in the Hunter River 
valley, New South Wales, under 30 ft. or more of alluvium. In 
this locality alluvium accumulates rapidly and instances are cited 
of some flats having been buried under 4 ft. of silt during a single 
flood (MacPherson, 1886). 
During the construction in 1913 of the Sugarloaf Dam near the 
junction of the Goulburn and Delatite Rivers, R. B. Comer, 
engineer, State Rivers and Water Supply Commission, collected 
hundreds of stone implements for the National Museum of Vic- 
toria. Among them was an axe fashioned from a pebble found 
more than 20 ft. below the surface, and four others from 28 ft. 
12. See also David (1923 a) and Tindale (1937 b). 
