1919.] 
Departmental Reports. 
213 
Table I. 
Faster- 
settling 
Sample. 
Slower- 
settling 
Sample. 
Mean. 
Composition 
of Complete 
Sample. 
Best Cornish 
Kaolin (for 
reference). 
Theoretical 
Values for 
H^AbS^O;). 
Al 2 0 3 , &C. • . . • 
Si0 2 
Water of constitution.. 
Per Cent. 
38-6 
47-8 
Per Cent. 
40-5 
46-6 
Per Cent. 
39-6 
47-2 
Per Cent. 
402 
47-3 
13-8 
Per Cent. 
40-6 
47-1 
9-3 
Per Cent. 
39-8 
46-3 
13-9 
On firing, the sample was refractory, showing no tendency to fuse at 
Seger cone No. 16 (1450° C.), and giving a grey, slightly mottled biscuit. 
CLAYS FROM THE WAITEMATA SERIES AND FROM WHANGAREI. 
Sample No. 1. —A strong plastic clay from New Lynn, where it is used 
in the brick industry. 
Sample No. 3.— A brick-sand from the Whitford district, where it is 
used for the manufacture of dry-pressed bricks. 
Sample No. 7. —A strong plastic clay from the banks of Turanga 
Creek, used in the local brick industry. 
Sample No. 14. —A strong plastic clay from Whangarei, where it is 
used in the local brick industry. 
Table II.—Results of Combined Analyses. 
(See p. 211 for full reference.) 
Sample No. 1. 
Sample No. 3. 
Sample No. 7. 
Sample No. 14. 
(d.) Actual clay 
{c .) Fine sand, &c. 
(e.) Coarse sand, &c. 
( b .) Fine fluxes 
(f.) Coarse fluxes 
65-6 
102 \ n 
22-4 ) 32 6 
Trace 
Nil 
4-2 
2 ^ ^ 90T 
87-4 ) yu 1 
1-6 7 AR 
3-0) 4 ' 6 
24-4 
60 ‘° I 76-3 
16-3) d 
Trace 
Nil 
44-1 
24-2 * 44-8 
20-6 ) 44 8 
8 f 9-2 
1-2) 
Ultimate Analyses and Notes :— 
Sample No. 1.—A large proportion of isotropic glass was distinguished in (c) and (e) ; 
otherwise (e) was chiefly quartz grains. 
Sample No. 3.— Whole sample : Fe 2 0 3 , 10-0 per cent. ; CaO, 1*6 per cent. ; 
MgO, trace. In ( b ) and (/), Fe 2 0 3 = 1*1 per cent. In (c) and (e), glass was 
in much greater proportion than quartz. 
Sample No. 7.—( c ) and (e) chiefly glass, with a little quartz in (e). A remarkably 
strong clay for the relatively low value of (d). 
Sample No. 14.—Volumetric estimation of Fe in ( b ) and (/) gave Fe 2-5 per cent. ; 
CaO and MgO both present, but actual amount not determined. 
Effect of Rhyolitic-glass Residue. —The microscopic examination of the 
residues (c) and (e) from the clays of the Waitemata series (Nos. 1, 3, 7) 
established the interesting fact that there is a large preponderance of an 
isotropic glass showing flow-structure and otherwise closely resembling 
the rhyolitic material which was mentioned at the beginning of the paper 
as being interstratified with the beds of clay. Now, Zschokke developed 
this analytical method for clays with a residue of feldspar, mica, and 
quartz. In order to determine whether his methods are applicable to 
these clays the following investigations were made : (1) The action of 
dilute hydrochloric acid on the clays, and (2) the action of strong sulphuric 
acid on rhyolite pumice. 
