300 Maw — Distribution of White Clays and Sands 



able alluvial deposition of that substance, resting on the top of the 

 Limestone strata. This clay occurs on the lands of Ballymacadam, 

 Lough Logher, Morristown, etc. ; the principal workings were made 

 upwards of 25 years since on the lands of Ballymacadam, and Lough 

 Logher. The first stratum of clay is said to be 30 feet thick ; be- 

 neath it is a bed of Surturbrand, or Wood Coal, 10 feet thick, exactly 

 similar to that at Bovey in Devonshire ; below which is a second 

 stratum of claj'' that has never been sunk through. The old workings, 

 both at Ballymacadam and Lough Logher, were made close to the 

 edge of the claj'- district, where it was not likely to be pure, and no 

 trials have yet been undertaken in the interior of the valley, where 

 it is probable a great body will be found." 



A reference to these beds is also made by Mr. A, B. Wynne, 

 (late of the Irish Geological Survey, and now of the Geological 

 Survey of India), in the data and descriptions accompanying 

 quarter-sheet 45 S.E. of the Irish Survey. A fuller account of the 

 formation is also given by Mr. Wynne in a paper read before the 

 British Association in Dublin (see abstract, p. 94, of British Asso- 

 ciation report, 1857), from which I abridge the following. " The clay 

 is found under and about the mine of the old Castle of Ballymac- 

 adam. The mode of its occurrence is very strange ; for when stand- 

 ing in the centre of the small hollow which it occupies, at a distance 

 of about 100 yards on almost every side, the Carboniferous Lime- 

 stone may be seen to protrude through the ordinary Drift, which is 

 spread over the surrounding country, and which most probably once 

 covered this isolated basin of Tertiary Clay, occuping an area of at 

 most about an acre and a half. One small pit has recently been 

 opened to a depth of 4 or 5 feet ; and in this in situ was found a 

 lenticular mass of Lignite. The clay is usually white, more or less 

 pure, and sometimes of a dun or bluish tinge, smooth to the touch, 

 and extremely tenacious. The Lignite is brown, and occurs in 

 different states of decomposition and alteration ; but none of it re- 

 mains sufficiently perfect to prove what kind of wood it was. Within 

 the space occupied hj the clay occur some of those natural drains so 

 common to the Mountain Limestone of Ireland, expressively called 

 by the peasantry Swallow-in-holes, they carry off all the surplus 

 water accumulated in the pits ; one in particular having been used to 

 drain them wherever they were opened. 



"Under about fifteen feet of white clay, containing small frag- 

 ments of plants, a bed of Lignite is reached, of varying thickness, 

 from which parts of trees four or five feet in length could be raised 

 without difficulty ; beneath this occurs the purest and best clay, 

 which is white (with sometimes a pale shade of blue) and soft, and 

 has a soapy feel. Lower than this no person has penetrated, as 

 springs of water bursting up through the clay filled the pits, accom- 

 panied by so offensive an odour of sulphuretted hydrogen gas as 

 could scarcely be endured; even now the place is not quite free 

 from a mitigated form of this unpleasant effluvium, which, as 

 stated by Dr. Griffith, attends the occurrence of potter's-clay in 

 many other places in Ireland, as the south-eastern margin of Lough 



