and Union of Supposed Distinct Species. 999 
composition, a difference which is also shown by the different 
analyses of common Chabasite, resulting in varieties havi 
different formularic expressions. For example, Acadiolite 
contains three per cent. more of silicic acid than common 
Chabasite, and is a tersilicate of lime and the other isomorphous 
bases, instead of a bisilicate of the same bases.: The minera- 
logical formula of Acadiolite is, 3 Al Si? + (Cal, N, K,) Si? + 
6 Aq., while that of Chabasite is, 3 Al Si? + (Cal, N, K,) Si? + 
6Aq. Rammelsberg is inclined to regard Phacolite as a mix- 
ture of Acadiolite and Scolecite (lime mesotype,) the latter 
containing an additional atom of water. By uniting the atoms 
of both, he thus states the chemical formula for Phacolite : 
2 R Si + AF SP + 10H. | As the analyses stand, (compare 
Berzelius’s and Thomson’s with the two just referred to,) 
Phacolite differs from Chabasite in containing three per cent. 
less of silicic acid, and three atoms less of water. Now it is 
obvious that these differences are insufficient to authorize a 
Separation of the two minerals, unless there be a want of 
agreement in crystallographical and other characters, greater 
than that as yet pointed out. An equally valid reason could 
be urged for the separation of Acadiolite from Chabasite, on 
the ground of a difference in their composition, had not the 
examinations of Prof. G. Rose proved an exact agreement in 
e angles of their primary crystals. So, also, of Levyne and 
melinite, which are now admitted to be only varieties of 
C basite, their occurring forms all being secondaries to the 
Same primary rhombohedron. ‘The evidence of the identity 
9f any two minerals is best shown by the incipient or inter- 
mediate passages of one into the other, in the same specimen. 
am not aware that, in the case of the Irish or Bohemian 
Phacolite, such evidence has been adduced ; no tendency of 
the sort is shown in the specimens I have examined, from those 
e wie Suppl. to his Handwörterbuch, p. 112. Tt was on these grounds that 
Chabasite. Proposed to separate Acadiolite, > wall as the 
— Poggendor.f's Annalen, xxv. 495. 
