26 E. &. Dana on the Datolite from Bergen Hiil, N. J. 
tory combination of O and 3, introducing so much irregularity 
as to make 4-7 at pty slightly triangular in shape. 
The planes T, 1-1, 4-2, , and 2 are never absent ; ore 2-i, O; 
1 are very common; i, are 1, —6-4, —4-2, —4-4, —6-5, —6-3, a 
little less common ; 7-3, 7-2, —8-2, 4, (the last generally associated 
with the cameras planes), were observed o 
tenth of the specimens examined; —1-1, a. 4 
2.9, #-4, on one-twentieth ; — 8-7, 7-2, 42, 3 2, 12, 7-3, 
are rare; and 7-4, 2-2, —6-3, —4-8, 3-3, are very ra 
The following ‘table of all the observed planes, ‘with the let- 
tering employed by different authors, is added for the sake of 
convenience of reference. Miller's letters are taken from Brooke 
and Miller’s Mineralogy (1852); eugene from Pogg. Ann 
xciv, 1855; Dauber, from Pogg., Ann., cili, 1858. The planes 
in this list that have not been found by the author on the Ber- 
gen Hill crystals, have their symbols in parentheses. 
fy 24, 12-4, 
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