Hill, Brodrick, and Rule — The Mitchelstoivn Caves. 267 



4 mm. ; the tube in the majority of cases is hollow, and contains a drop of 

 water at its lowest point. Owing to their fragile nature, they have all been 

 destroyed in the generally known parts ; in fact, in many cases they are too 

 fragile to sustain their own weight, fragments littering the floor in all 

 directions. The longest example was found in the Maze ; this stem measured 



5 feet 3 inches in length, and was, so delicate that its tip oscillated through 

 an arc of 6 inches when blown upon. It was unfortunately necessary to 

 break it to get along the passage. 



The Clay. 



The clay which has been mentioned as occurring in various parts of the 

 caves is found in the following places : — 



Old Cave. — The Eastern Chamber: the passage from the Three-tiered 

 Pillar to the Eastern Chamber. 



New Cave. — The Gallery of Arches: the two chambers to the south of 

 the Four Courts ; the Victoria Cave. 



In this last chamber- the clay which covers the floor has evidently dried 

 and cracked, and has subsequently been covered with a thin coating of 

 stalagmite, with the result that the floor sounds as if it were hollow. 



It will be noted that this clay occurs in every case in the most southerly 

 portions of the caves, which are also the lowest. Chemical analysis shows 

 that it consists largely of ferric oxide, with a little magnesium carbonate, 

 and a trace of calcium carbonate ; under the microscope it is seen to be in 

 a state of extremely fine division, and to contain minute fragments of 

 quartz, which in some cases possess the typical crystalline form of that 

 substance ; a few diatoms were also noted. Erom these facts one can 

 deduce that this clay is derived for the most part from the Old Eed 

 Sandstone of the Galtees, carried down either by glacial action or atmospheric 

 denudation. 



R.I. A. PKOO., VOL. XXVn., SKCT. B. [2 Pl\ 



