Notices of Memoirs—On a Fragment of Mica Schist. 515 
antiquity of deposits in particular cases based on the view that the 
accumulation is very slow, are without value. 
The mountain limestone ravines and passes are to be viewed in 
the main as caverns formed in the manner above stated, which have 
lost their roofs by the various sub-aerial agents which are ever at 
work attacking the surface of the limestone. If any of these be 
examined, it will be seen that the tributary caves open on their 
sides, and in some cases the ravine itself is abruptly terminated by 
a cavern. 
TI.—On a Fracment or Mica Scuisr. 
By Professor W. J. Sonuas, M.A., F.RS.E., F.G.S. 
HE author called attention to some appearances presented by a 
fragment of mica schist, pointed out to him by Prof. William 
Ramsay, Ph.D., while walking on the beach at Bodé, Norway. It 
is a tabular fragment, showing fine foliation-lamine, and traversed 
by two undulating veins of quartz, the undulations are very high and 
narrow, eight complete ones occurring along a distance of ten inches 
in a straight line. 
vu 
Face or Fracment or Mrca-Scuist, Boné, Norway. 
f f planes of foliation. » v and o’ vo folded veins of quartz, crossing the 
planes of foliation. (Scale 3.) 
The planes of foliation correspond to the bedding in the rocks of 
the neighbourhood (amongst which this same phenomenon was after- 
wards noticed). The folded quartz vein was at one time straight 
and cut across the foliz at right angles; the folding must have been 
accomplished by compression of the schist at right angles io its folie, 
and by measuring the length of the quartz vein between two points 
along its undulations (26 inches) and also directly along its path 
