274 [Proc. B. N. F. C, 



faces in periods of quiescence, burnt red by the succeeding flows. 

 Five of these can be seen at different levels at the Pleaskin, and 

 such abound in Madeira, Iceland, and Vesuvius, and probably in 

 most volcanic countries. The pisolitic ores are more peculiar, 

 and I am not aware of their accompanying volcanic lavas else- 

 where ; they are apparently confined here to the middle zone. 

 Messrs. Tate and Holden contended that they were the direct 

 products of metamorphic action, but this view has not passed 

 unchallenged, and the pisolitic ore is more generally thought to 

 have been formed by confervoid algae in shallow lakes, and in 

 the same manner that similiar ore is forming in Sweden at the 

 present day. Much of the lithomarge passes insensibly into 

 basalt, and has been directly formed from it without any 

 re-arrangement by water, and by ordinary atmospheric action. 

 All boles or ochres that were once surface soils are naturally 

 unfossiliferous, and for the same reason that the iron con- 

 glomerates are destitute of plant remains, namely, the coarseness 

 of the matrix being unsuited to retain delicate impressions, and 

 the looseness of the material permitting decay to continue after 

 plants were imbedded. The only f6ssiliferous iron-ores with 

 which I am acquainted, are those of Ballypalady, and all are 

 agreed that these decomposed basalts or ashes were re-arranged 

 by water. Several sections have been published, and they are 

 supposed to be on a not greatly different horizon to the Lignites 

 and Bauxites of the north-east coast, and to the pisolitic iron 

 ores. Duffin places them at about 600 feet from the base of the 

 basalts, and 400 feet below the nearest outflow. This must be 

 of course where the full thicknesses are present. Portlock believes 

 the materials to have been blown into the air, and afterwards 

 deposited in the quiet waters of a series of shallow lakes, the 

 iron being derived from basaltic uplands. Professor Hull 

 coincides in this opinion, and adds that the lakes were formed 

 in a depression of the basaltic area, due to the sinking of the 

 surface at the close of the second period of volcanic activity. 

 The iron was brought down by streams from the decomposing 

 basalts, and was dissolved as carbonate, and precipitated as oxide. 



