F. Chapman—On Sheared Oolitic Limestones. 103 
Anatysis oF DotomitizeD Limestone (dried at 100° C). 
Calcium carbonate (CaCO3)  ... wn. eee cee wees «| 14°88 
3 eulholnenne) (Casi)! dos se Nene eee Nitec coe) veoa | OR 
ss phosplaten(CaseOo)arec |) -.. 5 sschr scog) ceaumeeneULACE. 
Magnesian carbonate (MgCO3) ... 0. ... we eee ee «14°95 
Ferrous carbonate (FeCOs) BANS MET 02) URS Fe Ae AHO) 
Imsolublesy(SiOa\ersiece vere seer: tlcesy eek | ese) (aeill pee ORO G 
ROGAN ear! Mou. ssa) cher nasa ee MOORS 
As sulphide of iron is present in the rock it would appear that 
in the analysis it is represented by the other iron and sulphur 
compounds. 
The extreme condition of the sheared rocks found is shown in 
Fig. 4, from a specimen collected at Rillage Point. In this specimen 
the grains are drawn out to about ten times their present breadth. 
In one instance a grain was affected by the shearing force on a 
portion only, one side having been drawn out whilst the opposite 
side exhibits the almost circularly concentric layers of the grain. 
In this rock we see, besides the lengthened and contorted grains 
which give an appearance of fluxion structure to the mass, numerous 
well-formed crystals of dolomite disposed along the lines of cleavage, 
and which are stained by ferruginous material; also “eyes” of 
calcite, which can be traced to their origin as portions of joints 
and ossicles of crinoids. 
Fig. 4a is from a more highly magnified photograph of the same 
kind of rock, but from a different specimen. In this we see the 
decomposition which has taken place in the included iron pyrites, 
and the subsequent hydration, giving rise to a brown staining which 
in most cases obscures the centres of the dolomite crystals and in 
rarer cases brings out their zone-structure. The rock itself is of a 
rusty-brown colour instead of the dark blue-grey colour of the 
fresher kinds. 
Fig. 5 is taken from a rock collected at Rillage Point, and differs 
somewhat from the preceding series on account of the scarcity of 
the sheared granules and abundance of calcitic fragments and 
encrinite remains. In this rock there is no dolomite, and its absence 
is quite exceptional. The organic remains, it will be seen from the 
illustration, are conspicuously unaffected by the shearing, whilst the 
oolitic grains are very much attenuated. 
Fig. 6. is from a section taken across the coralla of Cyathophyllum 
cespitosum in a limestone formed of that coral. The attenuated 
form of these coralla is probably entirely due to the shearing action 
upon the rock. This specimen was obtained from Watermouth. 
Conclusions and Suggestions.—Although the sheared oolitic lime- 
stones were all found in the immediate neighbourhood of Rillage 
Point, whilst the less altered specimens were obtained from localities 
to the east of that place, it is highly probable that further investiga- 
tion will show that the comparatively unaltered oolite alternates 
with the sheared rock; that is to say, according to the evidence 
afforded all along this part of the coast of the excessive crumpling 
and crushing of the strata, it is only reasonable to suppose that the 
