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Proceedings of the Royal Irish Academy. 
whether by a direct, or an indirect process — is immaterial ; but that it 
has been effected by some process of pseudomorphism is a conclusion 
which our investigations have placed beyond all doubt. 
Two-thirds of Dr. Hunt's Paper are chiefly taken up with criticisms 
on our theoretical views, explanatory of the origin of the various 
" eozoonal features" by a process of pseudomorphic replacement. The 
other third is devoted to a singidar explanation of the author's ''view of 
the origin of limestones," and to the purpose of showing that we have 
formed a " misconception" of it. The view was simply adverted to 
by us in a foot note ; and, being only collaterally connected with the 
subject of *' Eozoon," we may be excused from going into it on 
the present occasion. We may observe, however, that the explana- 
tion in 710 loay modifies our conception. Leaving out of consideration 
the origin of the cited "great beds of ancient marble," the azoic for- 
mation of which is enunciated in a manner unfortunately too common 
with Dr. Hunt, we contend that in the formation of marine limestones, 
both vital and chemical processes — the one primarily, and the other 
secondarily — have been concerned. The idea that such limestones 
have originated solely by chemical action, " without the intervention 
of life " — that their containing fossils is merely an " accidental occur- 
rence" — reminds us of Dr. Hunt's "novel doctrine" of the direct 
chemical precipitation of serpentine from the water of the ocean. "We 
have shown that there is nothing in jN'ature to support this doctrine; 
and, with the exception of fresh water and littoral travertines — whose 
chemical origin is easily explained by causes which it is difficult to 
understand could operate where ordinary limestones have been formed, 
that is, in marine depths — we feel satisfied that its author is quite 
unable to advance any cases of a really apposite nature to support his 
view of the origin of limestones. 
"We shall conclude this communication by briefly recapitulating the 
various points detailed in our previously published Papers, in order 
that the reader may readily become acquainted with the present aspect 
of the question discussed in these pages. 
1st. The serpentine in ophitic rocks has been shown to present 
appearances, which can only be explained on the view that it under- 
goes structural and chemical changes, causing it to pass into variously 
subdivided states, and etching out the resulting portions into a variety 
of forms — grains and plates, with lobulated or segmented surfaces — 
fibres and aciculi — simple and branching configurations. Crystals of 
malacolite, often associated with the serpentine, manifest some of these 
changes in a remarkable degree. 
2nd. The "intermediate skeleton" of " Eozoon" (which we hold to be 
the calcareous matrix of the above lobulated grains, &c.) is completely 
paralleled in various crystalline rocks — notably marble containing 
grains of coccolite (Aker and Tyree), pargasite (Finland), chondrodite 
(New Jersey, &c.). 
3rd. The " chamber casts" in the acervuline variety of "Eozoon" 
