120 
Rex T. Prider. 
The yelloAV sand throug'hout the nia})ped area app(‘ars to be constant 
in character, wherevei* exposed in small pits the profile is similar, i.e. a thin 
surface layer of gr(‘y sand underlain by the structureless yelloAV sand. ]\rap- 
l)ing’ of Ibis formatidii was facilitated by the numerous small anthills of 
bright yellow sand brought uj) fi'om below th(‘ surface grey sand. The 
yellow sand possesses tht* ability to stand up in vertical walls such as the 
walls of a pit and in this respect and in its structurehss profile it vtu’.v 
closely resembles the yellow sand dt'posits of the Pei’lh .Alidropolitan Area. 
What is the origin of this sand ? It is (i) a residual sand derived from 
the low-level laterite and ferruginous sandstone, (ii) a dei)osit of the same- 
origin as the yellow sand of the Aletroimlitan Area or (iii) an aeolian de- 
posit against the Darling Scarp ? 
These various hy])otheses were lested by making mechanical analyses, 
heavy minei’al separations, shapt' analyses and an examination of the surface 
textui’es of the sand grains of the Ridge Hill yellow sand (two samples) and a 
yellow -sand from' tlie \icinity of the Department of Geology at Crawley 
(since t\u data exist I'Oiuau'ning the yellow sand of the Metro]>olitaii Ar<*a), 
on the lines described abov(* for the acid-insoluhle fraction of the Rid^ge Tlill 
ferruginous sandstone. The results of these determinations are set down 
in Tables HI, and V and the histograms of figures live and six. 
Ti’ask (lt)d2, p. 72) considers that if the eoenicient of sorting is less 
than 2.0 the sam]>le is well sorted— all the samples examined (see Table 
lAD therefore are Avell sorted. Aloreover in all cases the maximum sort- 
ing lies slightly on the fine side of the median as evidenced by the co- 
Tablu tit. 
MECriANirAL ANALYSIS OF YELLOW SANDS. 
(hand sieving with TvIcm* screens.) 
Grade. 
A 
0/ 
/o 
by weight of grades indicated. 
Tyler screen 
mesh. 
V 
Size (mm.) 
A. 
B. 
C. 
D. 
5- 9 
> 1-981 
XU 
XU 
0-81 
Nil 
9- 10 
•991-1-981 
0-.58 
1-44 
3-88 
0-04 
10- 32 
•495- -991 
19-50 
12-83 
12-33 
6-70 
32- on 
■240- -495 
50- 01 
35-42 
40-40 
18-03 
60-115 
•124- -240 
22-22 
20-90 
23-11 
30-41 
115-250 
•001- -124 
3-47 
1 1 • 85 
7-12 
3-02 
< 250 
< 001 
3 ■ 50* 
11 -.50* 
0-29* 
11-20* 
*Ry difference. 
A. Yellow sand (22804), Geology Department, Crawley. 
B. Yellow sand (21304), ft’om wall of gulley, 7 chains south-west from 14-mile peg. 
Ridge Hill. 
C. Yellow sand (22802), north-west corner Loc. 1298, IHdge Hill. 
D. Acid-insoluble residue from ferruginous sandstone (22798), Ridge Hill. 
