504 Hev. T. G. Bonney — Pitchstones and Felsites of Ar ran. 
themselves in alternate layers cbaracterized by differences in texture 
only.” The Southern dyke at Tormore seems to indicate that the 
banding is here caused by the more complete crystallization of the 
augitic constituent, the fine dust having aliuost disappeared from the 
glass with a marked increase in the number of belonites ; there are 
also several spherules. The pitchstone by the path in Birk Gien 
shows some fairly regulär isolated bands of yellowish glass, together 
with several more irregulär patches. In no case, however, liave the 
ends of these a torn or “teazed” look, as if they had been subjected 
to strain ; some indeed are quite round. Belonites occur in botk the 
clear and the yellow glass, sometimes singly, but commonly with 
the usual alga-like aggregates. They pass from the clear to the 
yellow glass, sometimes, however, being a little crowded on the 
surface of the latter, as though they stuck in a denser fluid. In it 
also the lateral microliths are less clearly defined, as though the side 
branches had fallen from the main stem of the plant, and had been 
replaced by a liehen growth. With polarized light these bands 
show an imperfect spherulitic structure, as do some of the rounded 
spots. In the former, however, there is no indication of any dis- 
turbance of the spherulitic structure, that is, it does not appear as if 
one or more spherules had been elongated into a band, but as if a 
line of imperfect spherules had formed out of a band. 
The first pitchstone on the shore south of King’s Cove gives 
indications of a rough perlitic structure. Under the microscope this 
appears more as a polygonal network of exceedingly minute cracks 
than as the ordinary perlitic structure. There are irregulär bands 
and cloudy spots of yellow glass ; the latter fi-equently showiug 
rings of darker glass, which, on examination, prove to be roughly 
concentric with the above reticulations. With crossed piisms these 
rings prove to be the boundaries of more or less perfect spherules. 
This rock does not show the alga-like tufts, but has numerous 
scattered belonites about -001 inch long. These often pass indiffer- 
ently into the spherulites, but are sometimes arranged radiately. 
There are a good many larger crystals scattered about, chiefly of 
sanidine ; some of which (but not all) show a growth of belonites 
perpendicular to their surface, and a radial structure of the sur- 
rounding mass. A pitchstone, from an erratic, 1 on the Old Lamlash 
Road, also shows a similar spherulitic growth on some of the larger 
crystals contained, but here also this structure is visible in many 
isolated patches of brown glass. 
The larger crystals occurring in the pitchstones sometimes, as 
described by Mr. Allport, include portions of the glassy matrix, but 
rarely, if ever, well-defined belonites. Sometimes they have evidently 
been broken, and the fragments lie close together. They appear then 
to be the first things formed in the rock, and perhaps may some- 
times be very muck anterior to the solidification of the ground-mass. 2 
1 I am not aware that the locality where this occurs in situ is known. It is the 
same rock as is described by Mr. Allport from a boulder occurring near W. Benan 
(Geoi,. Mag. Dec. I. Vol. IX. p. 537). 
2 I ha\e observed in numerous instances in trachytes, felsites, etc., that the forma- 
