Every variety of this stratum agrees in the two following properties, the presence of calcareous matter, which is manifested by a brisk effervescence when any part of it is submitted to the action of acids; and secondly, a more or less abundant mixture of pyrites; all the bituminous slates when exposed to the action of fire burn with a very strong offensive smell; but those found below the depth of eighty yards were not so disagreeable, in that respect, as those which were higher in the stratum. Varieties 33 and 35 were remarkable for their inflammability, and buened with a thick bituminous flame, appearing nearly equal in this respect to common coal; but after the bitumen was exhausted, the remainder was left undiminished in size. The organic remains which I have observed in this stratum as its general characteristics, are impressions of the cornua ammonis and some small bivalve shells.
The last division which I shall here notice, No. 7 of the Section, represents the alluvial collection of earth which appears to consist almost entirely of the spoils of the neighbouring strata. When these parts were deluged by water, the current evidently appears to have set in from east to west; for this collection of matter is found to consist principally of a mixture of the different strata which occur to the east of it in a state of decomposition; and in this mixture which is by no means regular, detached pieces of the beds before alluded to are found unaltered. Of these beds the chalk would expose the greatest surface to the erosion of the water, and next to this the shale would be most extensively acted on; accordingly we find that the alluvial deposition is composed of white marle and of blue, the former of which being of the least specific gravity, has overspread the higher parts and the summits of the hills, while the lower parts and the vallies are occupied chiefly by the latter. In the blue marle I have frequently found a variety of fossil shells,
