ASSOCIATED ROCKS OF PORTHALLA COVE. 469 
manner in which these rocks have arrived at their present con- 
dition. 
Specimen A.—A confusedly crystalline aggregate of dark green 
“hornblende” and light pinkish-grey and almost uncleavable 
“ felspar” (saussurite), the latter forming, perhaps, 75 per cent. of 
the whole mass. The indistinctly formed crystals of hornblende are 
arranged in bands; but scarcely any tendency to split in the direction 
of these bands is noticeable generally, while across them the rock is 
extraordinarily tough. This may be taken asa typical example of 
the peculiar hornblende schist of the neighbourhood of Porthalla. 
_ Specumen B.—This is like the former, but contains very much 
more of the hornblendic constituent. The foliation in this specimen 
would not be quite so distinct as in A were it not made more evident 
by the existence of a series of small contortions. 
Specomen C.—A polished block of the rich oil-green serpentine 
characteristic of this locality. It exhibits a very distinct banded 
structure which Prof. Bonney regards as “ flow-structure,’ but 
which I consider to be merely the traces of its former stratification. 
This view is, I think, confirmed by the fact that under the micro- 
scope the bands become less rather than more distinct. 
Specimen D.—This is a partly unaltered hornblende schist of 
the kind resembling B, but traversed on one side by a succes- 
sion of little veins and bands of true serpentine. The serpen- 
tine seems to have been developed on either side of numerous 
fissures or shrinkage-cracks, which are for the most part coinci- 
dent with what I consider to be traces of the original bedding. 
At one place, four or five of these little stripes of serpentine have 
coalesced, so as to form a band nearly one inch wide, from which 
might be cut cubes of that size scarcely differing in appearance from 
the compact specimen marked C. Between the stripes of serpentine, 
however, the hornblendic and the felspathic materials remain almost 
unchanged, as is rendered evident to the eye by the want of polish 
of their surfaces as compared with the polish of the serpentinous 
‘portions in the same specimen. ven in these unchanged portions, 
however, if the slabs be viewed in certain positions, thin threads 
and specks of shining serpentinous substance are plainly visible 
throughout the mass. This specimen alone seems to me quite 
sufficient to prove that the serpentine here has been developed by 
molecular change from, rather than intruded into, the hornblende 
schist. ) 
Specumen K.—Is much like D, but more largely hornblendic. 
Specimens F, G, H.—Are similar, but mainly serpentine, the pro- 
gress of the transformation being indicated by the reticulated bands 
and lines of darker colour. 
None of the specimens D to H presenting an intermingling of 
hornblendic, felspathic, and serpentinous substance have been thought 
worthy of analysis, owing to their very heterogeneity ; but itis cer- 
tain that by careful selection of pieces a series of analyses could be 
obtained, giving every variation of composition between hornblende 
schist and pure serpentine. 
