234 Beaumontite and Lincolnite identical with Heulandite. 
tises on mineralogy, nor am Ts aware that any notice has been ta- 
ken of it in the American Journal of Science. 
On comparing the crystals of this substance, with several of 
those of the Heulandite of Nova Seotia, which presented a modi- 
fication rather uncommon, I was satisfied that they were both 
derived from the similar replacement of the acute lateral edges, 
and obtuse solid angles, of the same primary right oblique angled 
prism; the planes f, which in most ‘inet nees are small, being — 
now so extended as to reduce the length of the figure to nearly 
the same dimensions with its breadth ; thus giving 1 rise to what 
might, at first sight, appear to bea squsire prism, terminated by — 
‘two obtuse four sided pyramids, resting upon the opposite late al 
faces of the crystal, as I have endeavored to represent by the sub- — 
joined figure 2. The planes a a’, being carried to the extreme, 
Fig. 1. . Fig. 2. 
+ or on M or T 90° — 
M on T 130 s 
M ona 147 17! 
M on f 114 20/ 
Pona 111 59! 
T ona 14 
so as to entirely obliterate the edge formed by the planes M and T, — 
of the right oblique prism, fig. 1,—the pyramids thus resulting, — 
are very beautiful in both minerals, particularly in the Beaumont- 
ite, and they present the same characteristic vitreous lustre, con- 
trasted with the soft, pearly white ‘reflection of the planes P, 
which we always observe in the crystals of this mineral from 
other localities. Both minerals, however, present shades of brown — 
and yellow. On further comparing their hardness and pyrognos- 
tic characters, and failing also to obtain any other cleavage in the 
Baltimore specimens, than that well known in Heulandite, I could 
have but little doubt that M. Levy, (unles§ he had described 
some other very analogous mineral from this locality, which I 
have not seen,) had been misled by its unusual crystalline form, : 
and,.instead of making known a new species, had only given us — 
the wrong characters of an old one. I am sure that he would — 
not have been led into a mistake of this kind, had the crystals 
examined by him presented those gradual changes which have | 
ultimately given rise to the figure supposed by him to be the 
primary right square prism of the Beaumontite, and which we 80 
readily observe in the crystals from Nova Scotia. : 
# 
