104 Scientific Proceedings, Royal Dublin Society. 
and 5). Scales of hexagonal outline giving parallel-sided transverse 
sections, and often of a pale green tint, are thickly disseminated 
through the varioles and the surrounding matrix; many are, no 
doubt, chlorite, but some, judging from the brilliancy of their 
colours, between crossed nicols, are probably secondary mus- 
covite. No definite pseudomorphs after augite are to be seen, 
but it is quite possible that this mineral was originally present, 
and is now represented by decomposition products such as the 
scattered chlorite. In the larger varioles a distinction into a 
central clearer region and an outer more granular zone is of 
Fie. 6.—Confluent varioles with central area and outer zone, the darkly shaded 
portion indicates the opaque border. LE. epidote, Ch. chlorite (x 19). 
frequent occurrence (fig. 6). The outer zone retains the structure 
and general appearance of the substance of the smaller varioles ; 
the central portion which polarizes in more brilliant colours is 
poorer in the radiating opaque lines, representing altered glass, 
and suggests the previous existence of a cavity, which has been 
since obliterated by a growth inwards from the outer zone that 
originally formed its walls. But as opposed to this explanation is 
the apparent existence of traces of a nuclear felspar-lath in some 
of these central regions, leading one rather to regard the whole 
