No. 424.] NOTES AND LITERATURE, 347 
aggregate of leucite and nepheline, with subordinate dark components. 
The author defines it as a “holocrystalline, porphyritic, leucocratic 
combination of leucite (or pseudo-leucite) and nephelite, with 
pyroxene and garnet.” The jacupirangites of Brazil vary from rocks 
rich in nepheline (true ijolites), through rocks composed predomi- 
nantly of pyroxene with small and varying amounts of magnetite 
and nepheline, to types rich in magnetite and with little or no nephe- 
line. The Magnet Cove rock corresponds to the intermediate of the 
Brazilian types. 







I. Ik I1. IVi Xp FIA VER 
Orthoclase.. . ..| 351. |.28.6 | 51-8.] 293 39 
An s su 39.8 39.0 hee 22.8 
Leucite . Ew ; 36.9 
Nepheline. . . . 3-1 6.2 20.3 9.0 25.5 38.7 4.0 
Cancrinite. . t3 
Sodalite 5.2 
Nosean Ls 
irit 5.1 6.9 5.7 4 4.6 
Hornblende 18.8 |Augite| 6.9 15.0 
iopsi I1.0 . &6 9.0 10.8 ird 64.0 
Biotite . . ‘ 7.9 5.0 
Apatite. 5 1.0 3.0 
phene . 2.7 5 3.1 
Magnetite ror 2.5 8.7 
Extra AlOs .. ——.—.L—42 Garnet 14.5 15.3 







i6 Pulaskite, from Fourche Mt., Arka 
II. Pulaskite sla Braddock's. uiid. 3 our M 
oQ 
III. Foyaite , Magnet 
Covite, near Voc tal Magnet Cov: 
- V,- Arkite (leucite-porphyry), near Diamond Jo Quarry. 
VI. Ijolite, near Dr. Thornton's, Magnet Cove. 
VII. Jac —— a C 
oma idiom anticis the author discusses the dendi elatis 
» the rocks with great fullness.. He represents the variations in 
their composition by diagrams and with the aid of these calculates 
the composition of the magma which, gave them birth by meth 
that are somewhat novel, The peculiar differentiation of the mass is 
- thought to be due to its small size.. The process was probably a “sort 
of fractional crystallization, the magma being regarded. as a solution, 
so that, in. accordance with the laws of cooling. solutions, the solvent 
(the portion in excess) crystallizes out first around the borders on 
RUE 1 
s Journ. of Geol., y vol. ix (1901), P: 645. 
