King and Rowney— On Serpentine Marble of Shy e. 137 
specimens : its absence, however, is readily explained by the fact that 
the grains of serpentine on their surfaces are for the most part floccu- 
lent — a condition which experience teaches us is incompatible with the 
co-existence of a fibrous coat. Fig. 5, pi. xiv,, represents an example 
of it, in addition to the larger and more varied one given in our last 
memoir. 
As regards the structures presumed to have formed the canal 
system," we find our Skye specimens containing finer and more nume- 
rous examples than we were led to expect, judging from the inferiority 
of those that occurred to us in the pre-cited specimen still we have 
failed in detecting any so remarkable as some we have seen in the 
Canadian ophite. As in the latter rock, many consist of serpentine, 
and others of malacolite : both kinds are irregularly rounded and exca- 
vated ; and, besides being simply rod-like, they are often remarkably 
subdivided or branching. The serpentinous examples (fig. 6, pi. xiv. ) 
are usually of a dull- white colour, and somewhat nodulose ; while those 
in malacolite (fig. 7, pi. xiv.) have often crystalline planes, a vitreous 
lustre, and a beaded appearance. In the specimens laminated with the 
amphibole-like mineral, the dolomite intercalations are crowded with 
miniature examples of typical forms. 
Having elsewhere entered considerably into detail in disproof of 
the view advocated by others as to the origin of the different ' ' eozoo- 
nal" features, we have no intention of taking up the matter in the 
present Paper, except so far as it bears on certain pseudomorphic phe- 
nomena; a subject, which, with few exceptions, has been singularly 
neglected by geologists of this country. The evidences we have 
adduced, as observed in various ophites and other crystalline rocks, all 
combine to prove — that the '^chamber casts" and'' canal system" 
have resulted from structural and chemical changes, inherent in and 
peculiar to the mineral silicates composing them — that this is also the 
case with the '' nummuline layer," which we have shown originated 
from chrysotile, a fibrous variety of serpentine — and that the substance 
(calcite, or dolomite) of the ''skeleton" has replaced one or other of 
the mineral silicates, consequent on the partial or complete removal 
of the latter by the above changes. The same conclusions are forced 
on us by an examination of the Skye specimens. 
As the malacolite exhibits most instructively the origin of three 
of the foregoing features,! we propose in the next place to give a brief 
account of our observations in connexion with this point. Being gra- 
nule-crystalline, the present mineral often exhibits itself as grains — 
usually elongated spheroids — with planes, edges, and angles. Generally, 
however, these parts are rounded off, and the resulting surfaces dis- 
play precisely the appearance of having been produced by some dis- 
solving agent. These peculiarities characterize the grains, whether 
they occur singly, or in laminar aggregations (" chamber casts") ; or at- 
* *' Quarterly Journal Geological Society," vol. xxii., p. 204. 
t The *' nummuline layer" seems to be restricted to serpentine. 
R. I. A. PROC. — VOL. I., SBR. II,, SCIENCE. T 
