THE ROMAN COMAGMATIC REGION. 
Chemical Composition of Viterbal Vulsinose [Leucite-trachyte]. 
II. 
III. 
IV. 
Si0 2 .. 
FeO.. 
MgO. 
CaO.. 
K 2 O... 
H 2 + 
H 2 O-, 
C0 2 ... 
Ti0 2 . . 
MnO 
56.19 
20.75 
1.71 
2. 19 
I-U 
3-53 
2.86 
o. 70 
0.30 
none 
0.65 
o. 24 
n. d. 
100.73 
0.936 
.203 
.on 
.029 
.063 
.046 
.112 
.008 
.002 
55-17 
19.60 
3-27 
2-74 
1.58 
3-73 
2. 27 
0.99 
none 
0.69 
o. 20 
n. d. 
99.82 
0.920 
. 192 
.020 
.038 
.040 
.067 
37 
.102 
.009 
.OOI 
58.08 
19. II 
3-55 
I. 00 
1.05 
3-76 
2.84 
8.86 
o. ii 
none 
0.82 
O.20 
n. d. 
99.92 
58.48 
18.56 
2.03 
3.16 
0.53 
2.60 
3-14 
10.47 
0.24 
0.70 
0.30 
I. Viterbal vulsinose [leucite-trachyte]. Sorgente di Grignano, southwest of Lake Vico, 
Ciminian District. H. S. Washington, analyst. 
II. Viterbal vulsinose [leucite-trachyte]. Below San Rocco, Monte Vico, Ciminian Dis- 
trict. H. S. Washington, analyst. Jour. Geol., V, 1897, p. 370. Additional 
determinations here. 
III. Bolsenal vulsinose [vulsinite]. Bolsena, Vulsinian District. (Cf. p. 31.) 
IV. Bagnoreal vulsinose [leucite-trachyte]. Monte San Antonio, Auruncan District, vom 
Rath, analyst. Zeits. d. 'd. geol. Ges., XXV, 1873, p. 244. Fe 2 O 3 , FeO, TiO 2 , 
and P 2 O S estimated by H. S. W. 
Norms. 
I. II. 
Or 62.27) 56.71 ) 
Ab 5.76^ 80.54) -S3f 82 '97 
An 12-51) { 90.48 14-73) 
Ne 9-94 9-94) 4.26 4.26 
| 2 ' 44 [ 4-86 2 ' 22 \ 5.17 
Ol 2.42 } 2.95 $ 3 ' 
Mt 255? 4-64? ,- 
II x.iif 3 ' 17 9 ' 31 1-375 Ml 
Ap o . 68 o . 68 o . 40 o . 40 
99.79 98.81 
Rest i. oo 0.99 
100.79 99.80 
Ratios. 
I. II. 
Sal 
Class p^ =9-72 7-54 
F 
Order =- =8.10 19-74 
,L* 
K,0'+Na 2 0' 
Ran 8 CaO^~ =3 ' 51 
K a O' 
Subrang ^Q' =2<43 2 ' 7<5 
87-23 
11-58 
