e 
306 Alger’s Localities of Rare Minerals, 
Journal of Science, (vol. xlvi. p. 235,) I gave my reasons for 
classing these two minerals with Heulandite. That Beau- 
montite is Heulandite, I believe, is no longer doubted in this 
country or Europe. An analysis of the mineral, by M. 
Delesse, has appeared since the publication of my paper,’ and 
it agrees with all the other analyses of Heulandite, excepting 
in the slight excess of silicic acid. In this respect, it offers an 
example analogous to that of the variety of Chabasite called 
Acadiolite, in which the silicic acid forms a larger atomic pro- 
portion of the mineral, without causing any appreciable variation 
in the angles of the crystals. As to Lincolnite, I must think 
that the various papers, that have been called forth in relation 
to it since my first communication appeared, have established 
its indisputable identity with Heulandite. 
Peculiarities in the modifying planes, have given rise to a 
secondary form, rarely observed in Heulandite. "These consist 
in the enlargement of the planes f (Phillips,) or ë (Dana,) so 
as nearly to obliterate the primary planes M; being, in fact, 
the reverse of what we usually observe in Heulandite from 
other localities. In the measurements by Prof. Hitchcock and 
Prof. Shepard, the angle of f on T was mistaken for that of 
M on T, and in the figure given by Prof. Hitchcock, it 15 
evident that the planes lettered M should be f. The true 
value of f on T is 115° 10 (Dana); Prof. Shepard's last 
measurements made it 116° 17'. : 
ererite. I am compelled, at last, to declare my convic- 
tion that the specific nature of this mineral can no longer be 
maintained. Connell’s analysis of an Irish Gmelinite, which 
agrees with Lédererite in all its physical and crystallographical 
characters, has shown also an identity in chemical composition. 
The phosphoric acid, detected by Mr. Hayes, must be viewed 
as an accidental constituent, varying probably in different 
1 Ann. de Chim. et de Phys. for 1843, t. ix. p. 395. Phillips’s Min. P- — 416. 
? For the figures see Am. Jour. of Science. vol. xlvi. p. 234, and vol. ni. p. Am. 
Corroborative evidence of the correctness of my opinions, by the editors of the 
rec + b y £ ^£: 
Jour. 
+ J 4" 
