1875-1876.] 157 



mysterious pile, with its grey cap o'ertopping the trees, the route to 

 the Fort Bog — the next stopping place — lay by way of Birchill and 

 Ballynoe, passing through bye-lanes fragrant and white with the 

 blossoms of the hawthorn. A short drive brought the party to the 

 fort, which lies about a quarter mile east of the road, and here a 

 stop was made to examine it. It is of considerable magnitude, 

 and, being in good preservation, is one of the most interesting of 

 the many which occur in this neighbourhood. The fort consists 

 of a central earthen mound, surrounded by a double trench. The 

 mound has a diameter of 140 feet, and is hollowed in the centre ; 

 on it the ancient residences were probably situated. The distance 

 from the margin of the mound to the outer edge of the enclosing 

 rath (or rampart between the two trenches) is 45 feet, and from 

 that to the circumference of the outer trench 27 feet, thus giving 

 a total diameter of 284 feet. The depth of the central hollow is 

 6 feet, and that of the inner and outer trenches 14 feet and 8 feet 

 respectively. The garden of an adjoining house touches upon the 

 outer circular trench for about one-sixth of its circumference, 

 otherwise the fort is perfect in every respect. Leaving the fort, the 

 cars are again taken, and the party proceed to Tardree Mountain 

 (Tardree signifying in Irish the Height of the Heather), and, after a 

 drive of three miles, passing another and much smaller fort at 

 Tardree Cottage, the porphyry quarries are reached. The porphy- 

 ritic district visited on this occasion occupies an area of some ten 

 square miles, the southern limit of which is about three miles north- 

 east of the town of Antrim, Tardree Hill being nearly in the centre. 

 The rock here found is a trachyte-porphyry, differing remarkably 

 in appearance and in lithological character from the surrounding 

 trap. It is usually of a light grey or almost white colour, highly 

 and coarsely crystaline, and, at first sight, resembling a granite. 

 It consists of a felspathic base, with crystals of glassy felspar, 

 smoke quartz, and several other minerals, and is readily, disin- 

 tegrated by weathering on the slopes of the hills, and the result is 

 a fine gravel or sand, which circumstance gives the name "Sandy 

 Braes" to a district east of Tardree. The porphyry is extensively 



