42 



The Irish Naturalist. 



and the stones were chosen as if they were to ornament a 

 museum. While literary and antiquarian visitors cannot fail 

 to appreciate the artistic beauty of the slabs, naturalists will 

 find many points of interest, even in their minuter details. 



Two of the slabs are from the lyissoughter quarry in 

 Connemara, and show the unique serpentinous marble in all 

 the perfection of its green and grey streaks and foldings. The 

 highly metamorphosed character of the rock is at once ap- 

 parent, and in one table the contortion of the bands can be 

 traced, while in the other a more parallel structure has been 

 set up by the continued deformation of the mass. The recent 

 paper by Messrs. Lavis and Gregory (^) on eozoonal structure 

 in limestones from around the vent of Vesuvius has given new 

 interest to these similar altered limestones of Connemara. 

 The green serpentine seems to result from the hydration of 

 bands and knots of olivine, which developed in the heart of 

 the Lissoughter limestone under the influence of an adjacent 

 igneous mass. How far the silica and magnesia required for 

 this change already existed in the limestone, or how far they 

 were transferred from the invading igneous rock, is one of the 

 vexed questions of contact-metamorphism. Messrs. Marr and 

 Harker, working on the alterations round the granite of Shap 

 in Westmoreland, conclude that such transference has only 

 gone on over distances of about g^tb of an inch ; while Messrs. 

 Lavis and Gregory, in their stud}^ of the blocks of Monte 

 Somma, above cited, are forced to believe in a more extended 

 process. 



These two handsome green slabs have as companions two 

 from the red quarries of Co. Cork. These also show the 

 effect of earth-movements in brecciating and streaking-out 

 the constituents of a rock. In one, the remains of crinoid- 

 stems are clearl}^ visible, and fragments of yellowish coralline 

 limestone, probably true blocks broken by wave-action from 

 adjacent reefs, lie in the fine red matrix. But pressure has 

 already affected the whole mass, and it has begun to break up 

 and to flow, as it were, under metamorphic influences. 



The second slab of ** Cork Red" is the tj'pical brecciated 

 variety, with abundant traces of crinoids, in the form of little 

 white circular sections, but with no good connected series of 



' Trans. Ro^xl Dublin Soc, 1 894. 



