1909-10.] The Clay Substance in the Glenboig Fireclay. 375 
The analysis of the clay substance points to its being either kaolinite 
or halloysite. A comparison of the results tabulated below leads to no 
very satisfactory conclusion. 
Analyses of Kaolinite given by Lacroix in “Min^ralogie de la France,” 
vol. i., 1895, p. 463. 
I. 
II. 
III. 
IV. 
V. 
Si0 2 . . . 
47-0 
45-97 
48-68 
46-5 
46-67 
A1A- • • 
39-4 
40-12 
36-92 
39-5 
37-65 
MgO -52 
CaO -16 
Na 9 0 -58 
MgO not det. 
H 2 0 . . . 
14-4 
13-91 
" 13-13 
14-0 
14-79 
100-8 
100-00 
99-83 
100-0 
99-27 
I. (Pholerite, Lodeve) ; M. Pisani ( Comptes rendus, liii. 1072, 1861). 
II. (La Chartreuse pres Liege) ; de Koninck (Bull. Ac. Sc. Belg . , lxiv. 734, 1877). 
III. ( Saint- Yrieix ) ; Forchammer (Pog. Ann., xxxv. 337, 1835). 
IY. Calculated from the formula for kaolinite. 
Y. Present analysis. 
Analyses of Halloysite given by Lacroix in “Min^ralogie de la France,” 
vol. i. p. 475. 
i. 
II. 
III. 
IV. 
V. 
VI. 
Si0 2 . . . 
A1 2 0 3 . . . 
48-95 
47-9 
46-3 
46-3 
48-7 
47-7 
31-46 
38-0 
39-5 
38-7 
36-5 
38-5 
CaO . . . 
3-88 
•17 
MgO not det. 
H 2 0 . . . 
14-48 
14-3 
14-3 
14-0 
13-6 
12-9 
Loosely 1 
98-77 
100'2 
100-1 
99-0 
98-8 
99-27 
combined > 
h 2 o j 
5-4 
8-5 
12-5 
4-0 
2-13 
I. (Huelgoat) ; Dufrenoy (Mem. pour servir d une descript. g6ol. de la France, ii. 220, 1834). 
II. (Huelgoat) ; M. Lechatelier (Bull. Soc. Miner, de France, x. 210). 
III. (Angleur (Belgique)) ; M. Lechatelier (Bull. Soc. Miner, de France, x. 210, 1887). 
IY. (Miglos, Ariege) ; ibid. 
Y. (Laumede, Dordogne) ; ibid. 
YI. Present analysis calculated for comparison. 
The microscopic examination of the sample showed that, in spite of the 
repeated washing, there was still a small amount of free quartz present. 
As the clay in the ordinary condition is highly siliceous, this might be 
expected to be the case. In order, therefore, to eliminate the free quartz, 
the A1 2 O s was supposed to exist in combination as the hydrous silicate of 
alumina, kaolinite. 
YOL. XXX. 
25 
