8o 
the superficial soil is to l)e regarded as wind-borne this 
explanation of the ironstone pebbles is almost the onlv 
one possible, for it is clear that these heavy i)ebbles could not 
have been wind-borne to any appreciable extent. As a matter of 
personal opinion the writer does not attach much faith to this ex- 
planation of the formation of the iron oxide pebbles, as most of 
them seem to him not (o be concretions in sifn, but rather more or 
less worn concretionary laterite pebbles which have been moved 
from their })Iace of origin and involved in sedimentarv drift. Thev 
are often much mixed with pebbles of jasper, chert, and other hard 
and weather-resistant rocks, and fragments of ^^'hite quartz. In 
places where the bedrock is close to the surface, it is not at all 
uncommon to see the surface so thickly strewn with quartz frag- 
ments as to be white in colour over quite extensive areas. Usually 
such quartz is not perceptibly water-worn, the fragments being 
shari)-angular or no more rounded than is usual w ith fragments of 
even hard rocks which ha\'e been exposed to weather on the surface 
of the ground, but every now and then it is by no means uncom- 
mon to find fairly well rounded pebbles of these hard rocks. It is 
not at all unusual to find that when trenches have been cut through 
areas where much fragmentary quartz is visible that the liedrock 
is not so close to surface as one might have thought, but is covered 
by several feet of superficial soil, all containing a good deal of the 
fragmentary quartz, ft is difficult to understand how wind borne 
material could have through it heavy lum])S of material mounting 
ujnvards from the bedrock, hut the explanation is simple if we re- 
gard the drifts as sedimentary, as water has very considerable 
lateral transt)orting power. I he stony layer is usually much more 
noticeable right at surface than on sinking a little way downwards, 
often appearing as if angular gravel had been thickh^ spread pur- 
posely over hr()wii soil. 1 his is doubtless due to superficial con- 
centration of the heavier stones included in the soil. The advocates 
of the theory of the soil being wind-borne material, if ihev can 
succeed in explaining satisfactorily why heavy angular fragments 
of stone should he distributed through the sui)crficial material, can 
easily explain the concentration of a suiierficial layer by ap])ealing 
to the removal of the light soil by wind and rain, as no doul)t these 
agencies are tjuite ca])al)Ie of so exi)laining the occurrence. At the 
present moment, we know that wind docs h]o\\' away some dust 
from the surface, and that rains wash au'ay .soil as mud. leaving 
any heavier material in the soil accumulating as a layer of super- 
ficial gravel. The only difficulty is to see, if tlic stuff was wind and 
rain borne in the first place, how it came to be so full of stones 
which could be so concentrated on surface, d'hc theory of aqueous 
deposition finds no difficulty in cx])laining the occurrence of the 
stones in the drift — quite similar muds with stones in them mav 
be seen along the shores of Lake Cowan any day one cares to look 
along the trenches dug for the Norseman Causeway — hut suggests 
