E. S. Dana on the Datolite from Bergen Hill, N. J. 21 
Dana. Mohs. Miller, Schreeder. Dauber. Des Cl. 
g 
(—$2) ‘ a i (h Gregg) 
Zz 
=eEer RNR 
—82 q g B g 
29 h h a h 
& 
14(2) (new) 
In the figures the axes have the positions and ‘the relative 
values adopted by Professor Dana, and the system of symbo 
employed is also the same. It is to be noticed that Lé 
adopted this position of the axes in his work on the Heuland 
Cabinet (1837), while other authors have taken 7-1 as O an 
made either 2-2 or 4-2 the fundamental prism. This position 
has the considerable advantage of giving the planes in vertical 
the . 
double the length of the vertical axis; the theoretical form 
would then approach more closely to the dimensions commonly 
occurring in the crystals. 
It is worthy of note that the planes of the fundamental plus 
octahedrons are represented by the terms in the series ¢ $ $ } 
444; and excluding 8-2 and 3-2, two clinodomes mentioned b 
Des Cloizeaux, the clinodomes are all of the same series, thoug 
wanting thus far the members £ and 4. 
In the preparation of this article I have had the free use of 
the specimens of datolite in the cabinets of Yale College, Prof. 
G. J. Brush, Rev. E. Seymour of New York, and Mr. Benjamin 
