520 REPORTS ON THE STATE OF SCIENCE. 
No. 151A is a Sillimanite Gneiss, from the heart of the central 
Its peculiarity of composition will be at 
complex, and highly crystalline. 
once obvious. 
No. 151a, 
12 V.B. Big boss N. Tyddyngyrfa. 
8i0, 
Al,O, 
Fe,0, 
FeO 
CaO 
MgO 
K,O 
Na,O 
CO, . - . 
H,0 (at 110°) 5 
H,O (above 110°) . 
Site 9 : : 
Lic 
54:01 
99-04 
N.E. corner. 
Il. 
53°99 
2105 
1:23 
10°35 
2°79 
The percentage MgO in above analysis is probably too low. 
The second determination of alkalies is by Dr. Orton. 
Nos. 269 and 292-3 are two highly crystalline marbles from the 
mica schist zone, that of 1124. 269a is the beautiful Bodwrog Limestone. 
The other is a rock not before described. The insoluble residues consist 
of micas, calc, silicates, titaniferous minerals, and zircon, besides quartz. 
No. 269, 
13. 8.W. Bodwrog, B. of Church St. Trerog. 
Residues insoluble in HCl. 
Fe,0,+Al,0, . F 
MnO. x 5 ° 
CaO . 5 5 
MgO . ° . . ° 
CO, . . . . 
99°82 
.”. percentage CaCO, = 89°48 
Nos, 292 and 293s, 
13. N.B. Ddraenog. 8. of wood, about 4 mile to N.N.E. 
Residues insoluble in HCl 
¥e,0, + Al,0, 
MnO. 
CaO . t 
MgO. : , : 
COP. - : : 
i: 
23% 
6 
> 
98°11 
.”. percentage CaCO, = 66°57 
2nd Limestone from W. 
rE; 
4:93 
2°02 
50°17 
0:12 
42-01 
99°25 
89°59 
Il. 
23°22 
6°94 
37:36 
0:72 
30°42 
98°66 
66°71 
Slightly different specimens from adjacent parts of a slightly variable 
rock were mixed and analysed as one. 
Besides these rocks from the hornfels and adjacent Zones, certain 
others have been analysed for various reasons, 
