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sia ‘Tho form ofthe fragments ms leche noticed. This 
- 
is either, 
a, angu ular, 8. water-worn, ¥. rolled. 
3. The Gagnon should be referred, if possible, to some 
mineral species of lithoidal rocks, and their varieties, if any, 
taken notice of; as well as the occurrence of isolated crys- 
tals, rare minerals, shells, wo c 
4, The solidity of the con lomerate rock ; which may be, 
o incoherent, or earthy, Bind ated, 
. The divisionary Amani ure, pare occasionally me 
with in conglomerate as well as in lithoidal rocks, ee 
ject to the same varieties of form 
The volcanic rocks, both lithoidal and conglomerate, are 
sometimes found in-an altered state, from having been expo- 
sed to the decomposing influence either 
proximate emanations of Lcoenete vapours charged 
with sulphuric and muriatic acids ; or, 
, Of the ordinary atmospheric pai nis. 
Ta the first case, the alumine and potass of the felspar and 
augite are taken up by the sulphuric acid, and deposited by 
the agency of water, as sulphat a alumine (alumstone,) in 
the cavities aud fissures of the rock, and in neighbouring hol- 
lows ; leaving the remainder of the rock, composed almost 
solely of silex, in a canous state, but often filled NP ier other 
infiltrated matters as well as alum, and stained w rrugi- 
nous oxides, from the union of its iron with re 202 pons of 
the acids. In the second case, the decomposition 
gite and felspar, sometimes of one, at others of both, —_— 
ces a variety of argillaceous earths or boles, giving to the 
rock, which is then often called wacke, a more or less argil- 
laceous aspect, proportionate to the degree of decomposi- 
tion, and sufficient to render it occasionally difficult to recog- 
nise its original mineral composition. These boles are some- 
times conveyed by aqueous infiltrations into the cellular and 
other cavities = the rock, giving occasion to the amygdaloi- 
dal compositio 
The object ono posbtls in the foregoing remarks is to endea- 
vour to establish a fixed nomenclature for the principal cha- 
racteristics of the voleanic rocks, so as to enable any obser- 
ver to define or describe their Mn accurately and 
distinctly; for the ulterior purposes of geology. Names may 
be subsequently given by geologists to any of these varie- 
ties, for the sake of avoiding a redundancy of words, or not, 
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