18 E. &. Dana on the Datolite from Bergen Hill, N. J. 
Among the new planes, the following are determined by the 
zones in which they occur, as will be seen in the figures: 
O-§, 24 (fig. 4), 4-2 (fig. 8), ¢2 (fig. 14), —4-3 (fig. 8,) 
3-8 (fig. 12),* 1-2 pe ae Sicchaa 1 and 1-2). OA1-1=171° 1’ 
(measure ae is e plane 7-2 consists of an oscillatory 
combination of 7-7 < 'L 
Other new vertical prisms are 7-4 (fig. 11), and 7-3 (fig. 8); 
1-4 %-t = 170° 58’ ‘gece 171° 11’); +8 A7¢= 117° 39’ 
(measured = 117° 51’). 3 (fig. 8) is a new octahedral plane; 
OA 2=158° 36’ sabieisiate 158°50’). §-3 has always the shape 
and position shown in . figs. 9and 12; t-tr4 -8=108°4’ (measured 
=107°-108°) ; Ov §-8=188° 14’ (ere ee 188°). -6-3 (fig. 
9) is on the edge between J and —4-2, consequently m=— 
n . 
SE | } 
the case did not admit of determination by measurement ; ta n 
is obviously less than 2 and greater than 1, and it is hence very 
probably equal to 3 , Which puts it in the same zone with 12-3. 
Between 4 a and 22 a rough plane was observed in one 
case. Here maa" +43 the plane gives an angle of 165° to 168° 
upon 2-2, and consequently n cannot be less than 3. 
A remarkable series of planes, usually convex (figs. 
17), in the ne zone with —2-2, 2-1 and J (opposite —2- 3 
having ins = often takes the place of the clinodome 2-%, 
which Boel present is very narrow. The common form of this 
+m-n plane (G) is convex ; starting from —2-i, where it makes 
on 7-7 an angle of about 95°, it curves around toward J, chang- 
ing in the value of m and n constantly till the intersections wit 
4-4 and 1 become parallel and it makes an angle on 7-7 of 101° 
to 102°30’. This is represented in fig. 17, which is a front view 
of the plane. In fig. 14 we have a plane of this zone quite flat 
though unpolished, and giving on measurement the angle on t-t 
of 94° 80’-96°; its s ce oe is consequently }- 9 (required 95° 42’). 
Another plane of this zone, also sometimes occurring alone, as 
shown in fig. 16, a direct view of it, makes parallel intersec- 
Fis with 4-2 and 1, oe is hence 3 - ¢¢,5-5=100° 57. On 
e edge between §-5 and —2-7 the same crystal, a plane 
spice , fig. 16) which heat to the other part of @. 
Des Cloizeaux gives the planes y, , x, #, %, misapprehending the form which 
he tubes frome Doone Mineralogy; placed in the proper position y would become 
dh, x, g, ete. y (-2 2), however, he figures also from a crystal of Haytorite. 
* In figures 12 and 15 the crystal is represented in eesti gs ses necessary 
in order to show well the new planes. 
