266 Leonard — Midden on Omey Island, 



its overlying claj', with the fact that, together, they do not attain a 

 maximum thickness of eighty feet — oftener less than forty — we 

 shall see how improbable it is that such deposits could resist all the 

 geological changes, with their disturbing, abrading, denuding forces, 

 from Devonian times until now. In the manner of its occurrence, 

 as well as in its stratigraphical position, the deposit appears to me 

 to be analogous to the deposits of white clay, which Mr. Maw has 

 recently described as lying in pockets and hollows of the carboni- 

 ferous limestone of North Wales, just below the mass of sands, 

 gravels, and clays of the Glacial epoch.^ To that epoch I think the 

 clay and gravel overlying the Nassau phosphorite must be referred, 

 and from the way in Avhich this deposit is interlaced, dovetailed and 

 mingled with the lower portion of the clay, I am led to regard it as 

 a Tertiary deposit, whose formation immediately preceded the 

 somewhat indefinite period which we term Glacial. 



It may be interesting to note that the absence of boulders of any 

 considerable size, either foreign or local, from the clays and gravels 

 of Nassau appear to confirm the opinion of the late Edward Forbes, 

 that, at a point not far south of England, the severe climate of the 

 north passed rapidly, even during the Glacial epoch, into one much 

 warmer. 



The discovery of large stores of the raw material at a time when 

 superphosphates of lime are so largely in demand for agricultural 

 purposes, must be of great importance, and already considerable 

 quantities of the Nassau phosphorite have been shipped to this country 

 for use in the manufacture of artificial manures, — if, indeed, it be 

 true that the lapse of time makes that artificial, which was as 

 natural in its origin as the phosphates of yesterday. 



V. — Kitchen Midden on Omey Island, Co. Galwat. 

 By H. Leonard, F.R.G.S.I., of the Geological Survey of Ireland. 



OMEY is a half-tide island off the coast of Galway. It is chiefly 

 a Porphyritic Granite rock, on the north-west portion of which 

 are wind-blown sands that are for ever changing their positions, the 

 houses of the inhabitants being covered to such an extent by them, 

 that, in order to reach the interior, they are compelled to descend 

 through holes, like large rabbit-burrows. The oldest record we 

 have in connection with the island is, that St. Fechin built an 

 Abbejr there previous to a.d. 664. This abbey is said to be buried 

 in the sands, but its exact site cannot be pointed out; however, 

 there is a supposed fifteenth-century church, that is now sunk 

 12 feet deep in the sand. 



Tlie Kitchen-Midden or shell-heap (the subject of this paper) is 

 situated on the south shore of a small bay, which indents the western, 

 shore of the island ; and opposite to which, on the north shore, is a 

 very ancient well, dedicated to St. Fechin. The shell-heap is 50 



^ Geological Magazine, 1867. Vol. IV., pp. 241 and 299. 



