1888.] 49 [Uhler. 
carbonate of iron, the richest of which occur near the base, while the 
nodules and oxidized lumps are found nearer the surface. The extension 
of this bed still higher, at various levels, displays the red and white varie- 
gated clays, such as we see in large areas in crossing the country south 
and east of the iron-ore hills. 
The formation, as far as our present knowledge goes, and disregarding 
the iron-ore clays, first appears beyond the head of Northeast river on the 
eastern shore of Maryland, extending thence south of south-west—with 
an irregular expansion west—down the peninsula between the Northeast 
and Elk rivers, crossing the Chesapeake bay to Harford county, and pro- 
ceeding across Baltimore county, the upper half of Anne Arundel and a 
narrower strip of Howard, Prince George’s and Montgomery counties to 
the Potomac river. It is probably the lowest of the alluvial formations 
thus far discovered in Maryland resting on the outer, eastward, exposures 
of the Archean rocks. ‘Extensive faults in these rocks, besides the ero- 
sions, have left deep basins along a wavy line somewhat parallel to the 
western shores of Chesapeake bay, and in these depressions the beds of 
the Baltimorean formation have been laid down. At the bottom is found 
very micaceous sand containing an abundance of that type of compact 
quartz which belongs to the mica schists, and such as is seen in the Phila- 
delphia micaceous gneiss. * 
These micaceous sands form beds in many localities ten feet thick, but 
oftener much less than that, and they grade almost imperceptibly into 
obscurely stratified beds of white clay. 
Next above this, the white clays alternate with sands in uneven beds, 
more or less stratified, the sandy members usually carrying drifts of quartz 
gravel in the lower portion. In some places the clay forms the chief ele- 
ment of these beds, while in others the sands prevail. The entire thick- 
ness of this part of the formation ranges from thirty to eighty fect, and is 
directly overlaid by whitish mixed sandy clay, upon which rests seven to 
nine feet of a coarse, angular sand, commonly pure white, capped by the 
thin layer of iron-paint-stone supporting the fossiliferous clay strata and 
iron-ore beds. 
Above these latter the more or less ferruginous sands, mixed with drift 
of all sizes, form conspicuous beds of very variable thickne In Clifton 
reservoir they constitute a series of strata and beds rising thirty feet above 
the dark or variegated clays, and are overlaid in turn by a few feet of 
quartz gravel, at or near the surface. Where the clay hills north of Bal- 
timore have been denuded, these gravels are seen at the surface, but 
where they are undisturbed, the gravel lies from three to ten or more feet 
below the superficial sand or loam. 
The region occupied by this formation is a rolling one, and towards the 
* In passing it may be worth while to observe that this variety of gneiss has.at one 
time formed extensive beds in contact with the more basic rocks on the north side of 
Baltimore, but these have been broken up, and now only their shattered remains rest 
on, or in, the soil as huge boulders or scattered fragments. 
PROC. AMER. PHILOS. 800. xXV. 127. G4. PRINTED APRIL 5, 1888. 
