688 WHITMAN CROSS 
is neglected. This ratio is exactly that of analcite except for 
the silica. It cannot be assumed that the material isolated was 
pure, and small amounts of various substances no doubt went 
into solution. But we can reasonably consider it demonstrated 
that the isotropic substance acting like a mineral constituent 
has practically the composition of analcite. I can see no reason 
for doubting this identification. 
The analysis of the soluble portion of the rock leads to prac- 
tically the same result as that of the isolated analcite. By 
deducting olivine, apatite, and magnetite, there remains a resi- 
due having about the ratio 1 : 1 for Al,O, to alkalis. Silica is 
again low. If nepheline were present in the rock the low silica 
of both analyses might be explained. It is possibly there in 
some small amount but probably not in sufficient quantity to 
entirely explain the figures of the analyses. 
The augite proves to be quite high in alumina and to have 
more titanic acid than would be inferred from the pale violet 
tinge it exhibits. It is thoroughly normal augite. 
An analysis of the rock of The Basin was also made by Dr. 
Hillebrand, and it is given in column IV of the following table, 
in which analyses of several allied rocks are introduced for pur- 
poses of comparison. Of the other analyses, V is of a rock from 
Shelburne Point, Vermont, described by J. F. Kemp and V. F. 
Marsters,’ with other dikes of the Lake Champlain region, In 
the original description Kemp published another analysis of this 
rock, the accuracy of which he was afterward led to question, 
and the analysis here quoted, made by H. T. Vulté, was published 
by Pirsson, at Kemp’s request, in his cited discussion of the mon- 
chiquite group. VI is of one of the original monchiquites from 
Brazil, by M. Hunter. The relation between the analcite-basalt 
and the other basalts of the region is illustrated by analysis VII, 
by W. F. Hillebrand, of a normal plagioclase-basalt occurring in 
Saddle Mountain, a few miles northwest of The Basin. 
t The trap dikes of the Lake Champlain region. Bull. 107,U.S.G.5S., 1893 p. 32 
2 Uber Monchiquit, ein camptonitisches Ganggestein aus der Gefolgschaft der Elz- 
olithsyenite, Tschermak’s Min. und petr. Mitth. Vol. XI, 1890, p. 445. 
