194 Proceedings of the Koyal Society of Edinburgh. [Sess. 
Table B. 
No. 
1 . 
2. 
3. 
4. 
5. 
6. 
7. 
Ignition loss . 
9-4 
12-7 
9-9 
7-8 
8-5 
10-4 
8-8 
Si0 2 
45-5 
43-9 
46-2 
46-5 
46-9 
49-8 
48-6 
A1 2 0 3 . . 
26-1 
23*4 
24-7 
25-6 
23-6 
22-0 
20-4 
Fe 2 0 3 
12-0 
12-4 
12-4 
121 
12-6 
9-6 
13*1 
CaO ... 
0*7 
1*4 
0-9 
0-6 
0-9 
1-1 
1*9 
MgO 
3-1 
3-2 
3-2 
4-0 
4-6 
4-0 
4-8 
K 2 0 ... 
2-7 
2-4 
2-2 
2-9 
3T 
2-3 
1-9 
Na 2 0 
0-4 
0-5 
0-4 
0-4 
0-6 
0-7 
0-4 
No. 
8. 
9. 
10. 
11. 
12. 
13. 
14. 
Ignition loss . 
11*0 
100 
11-2 
9-1 
10-3 
7-5 
10-6 
Si0 2 
47*4 
41-3 
47-4 
47-3 
48*9 
48-8 
47-9 
A1 2 0 3 
20-8 
19-9 
29-1 
20-5 
21-6 
22-6 
20-9 
Fe 2 0 3 
11*3 
19-0 
6-5 
12-8 
12-1 
12-8 
12-9 
CaO ... 
1*5 
3-7 
1-3 
2-2 
TO 
1-7 
0-9 
MgO 
2-9 
2-7 
2-6 
4-8 
3-6 
4-7 
34 
K 2 0 ... 
3-6 
2’4 
1*6 
2-4 
T9 
T3 
2-7 
Na 2 0 
1*4 
0-9 
0-2 
0-8 
0-5 
0-5 
0-6 
The above figures, it will be perceived, present a considerable degree of 
uniformity and there are no very serious divergences from the mean of 
Nos. 1 to 13, which runs as follows: — 
Loss 
Si0 2 
ALOo 
Fe 2 0 3 
CaO 
MgO 
k 2 o 
Na 2 0 
9-8 
46*8 
23-1 
12-2 
1- 4 
3-7 
2- 4 
0-5 
99-9 
Chemically, then, this substance is composed in the main of silica, 
alumina, ferric oxide, and water. On calculating molecular ratios from the 
above average we find 
Si0 2 : A1 2 0 3 : Fe 2 0 3 = 1 : 0-287 : 0*096, 
whence 
A1 2 0 3 : Si0 2 =l : 3'5, 
or 
(AlFe)A:Si0 2 =l : 2 6; 
that is, the molecules are in no simple proportion. This is only to be 
expected in view of the mixed nature and origin of the clay-substance. 
