Notices of Memoirs — W. A. Traill on the " Glen Rock." 609 



Eiver, and which forms such a remarkable feature in the district. 

 This rock was a mass of Travertine or Calcareous Tuff, approxi- 

 mately of the following dimensions : in length, N. and S. 310 ft. ; 

 E. and W. 285 ft. ; and in thickness varying from 6 ft. to about 

 80 ft., and estimated as containing over 2,100,000 cubic feet. 



This tuff varies from a soft, open, porous nature to a hard, ringing 

 travertine. It is in part stalactitic, mammillated, or reniform, and 

 often efflorescent, but mostly an intricate network of the casts or 

 incrusted forms of various vegetations, brambles, grasses, mosses, 

 ferns, ivy, etc., which, on being coated with the deposit of carbonate 

 of lime, and the vegetable matters decomposing, have left their im- 

 pressions behind. In addition to these are also included the bones of 

 some small animals and birds and the shells of land snails, etc., in- 

 stances occurring of their being thus entombed while still alive. 



The origin or source of this large mass, in the author's opinion, 

 was due solely to a large spring or Holy Well situated a little above, 

 on the slope of the hill, from which there issues a copious and con- 

 stant supply of water. This probably passing for a considerable 

 distance through the limestone rocks, and becoming thus highly 

 impregnated with lime, and prevented from flowing in a regular 

 channel, overspread the rank vegetation, which engendered a more 

 rapid evaporation and consequent deposition of the carbonate of 

 lime, the marly soil encouraging the more rapid growth of the 

 mosses, ferns, weeds, etc., each in succession falling a prey to the 

 covering of lime as it was deposited upon them, and thus more 

 rapidly building up this isolated mass of calcareous tuff. 



At present the action does not seem to be going on as actively as 

 at former times, the stream being more confined to a regular channel, 

 and flowing round the side of the mass ; but even still the ivy roots 

 and stems are inclosed in stony cases, the living plant growing out 

 therefrom. Large quantities are annually carried away for spreading 

 over the cultivated lands and for forming ditches. 



Although many streams in a limestone country have a tendency 

 to deposit calcareous matter, in few localities in the North of Ire- 

 land does there exist such a remarkable and isolated mass of Tuff. 

 The age of this rock must be considered of very late origin geo- 

 logically, long after the present configuration of the country 

 had been formed, and though probably accumulating somewhat 

 even to the present time, it has not increased in thickness for the 

 last 300 years, as foundations of that age exist on its highest part ; 

 it seems rather to be now breaking up under its own superincumbent 

 weight. In the year 1831, a large mass becoming detached fell and 

 completely crushed a cottage which was built adjacent to it, killing 

 four people within it at the time. 



In addition to the geological interest, there was an historical and 

 local interest connected with it, and also many legendary tales. 



In one portion of the rock, in a cave partly natural, but enlarged 

 to a circular form of about 22 feet in diameter, for upwards of 

 20 years a school was held, with an attendance of 60 children. This 

 school was supported by the inhabitants of the Glen, but was dis- 



