J. EL. Marr—Some Effects of Pressure. 219 
present the appearance shown in Fig. 1c, where we find a series of 
lengthened “eyes,” forming flattened lenticular patches interbanded 
with the normal cleaved argillaceous material. By these simple 
changes we have produced a rock having all the mechanical 
characters of a schist, but consisting of alternating lenticular patches 
of limestone and clay-slate, and presenting the apparent false- 
bedding which is also seen in true schists. The apparent dip of the 
rocks is here entirely fallacious, and is due to the pulling out of the 
limestone “eyes,” so as to have their longer axes parallel with the 
general strike of the cleavage planes. In many cases the cores of 
the larger folds have the “eyes” compressed together to form an 
irregular nodular mass, in which the separate ‘‘eyes”’ can be some- 
My yy) 
THU 
Fic. 1 1’. Transition from ordinary overfolds to the stage 1a. 
>, la. As in text. 
», la la’. Transition from 1a to 1c as produced along the fault plane in 14. 
», 6 le. As in text. 
times with difficulty determined, but at other times the lines of 
demarcation are wholly obliterated. In these masses, the crinoid 
joints of which the limestones are largely composed are affected in 
the way described by Dr. Sorby in his Presidential Address to the 
Geological Society (Q.J.G.S. vol. xxxv. p. 89), and in some cases 
are seen converted into a number of irregular polygons. Along 
the planes where the limestone ‘“‘ eyes” have been dragged out, we 
find that the crinoid stems are separated in a way similar to that 
fizured by Heim in the case of a Belemnite (Mechanismus der 
Gebirgsbildung, pl. xv. fig. 6), and the spaces separating the different 
joints are then filled with crystalline calcite. 
