60 PHYSICAL GEOGRAt»Hir 



It has already been stated that the direction of this primary 

 chain is north-east and south-west; its south-eastern flank 

 being covered by extensive arenaceous and argillaceous depo- 

 sites, referrible to the secondary and tertiary periods. On the 

 "Western Shore of the Chesapeake bay, the deposites belong- 

 ing to the secondary period are more extensive, it is believed, 

 than is generally admitted. Those that are contiguous to the 

 primary chain are composed of ferruginous sandh and clays, 

 enveloping masses of ferruginous sandstones, ochres, iron- 

 stones, nodules of carbonate of iron disposed in beds, and in 

 their lower portions. Lignites. They are in many places 

 covered by large bowlders; but more generally with coarse 

 gravel, which does not extend however, beyond a few miles 

 from the upper limits, when it disappears, leaving the sands 

 and clays uncovered, still very ferruginous, and after crossing 

 the head of the Severn much mixed with green particles. 

 North of this, on the banks of the Magothy, there occurs a 

 considerable deposite of Lignites, associated with iron pyrites 

 and amiber, containing nests of insects converted into amber 

 that appear to have been formed around the smaller twigs of 

 the wood from which the Lignites have been produced ; but 

 no other fossils have been discovered. Six miles from this 

 locality, south, on the banks of the Severn, there is a deposite 

 of micaceous black sand offering indisputable proof, in its fos- 

 sil contents, though in a very imperfect state of preservation, 

 of a secondary character ; being Exogyra, casts of Cuculloea 

 Mortonii, associated with Lignites and amber. Other analo- 

 gous formations, possessing the same mineralogical characters, 

 and the same geological features occur so frequently in a broad 

 belt of country contiguous to the more obvious tertiary depo- 

 sites, that although no characteristic fossils have as yet been 

 detected in them, owing probably to their never having been 

 penetrated into to a sufficient depth, it is difficult to resist the 

 belief that they are not of the same epoch. Thus, a micaceous 

 black sand covered by a continuous band of siliceous rock, 

 occurs twenty miles south of the deposite on the Severn, near 

 the Patuxent river, associated with a pure green sand ; it re- 

 appears under the same circumstances, except the attendant 

 green sand, on the opposite side of the river; it is seen in the 

 neighbourhood of Upper Marlborough, containing fossils, but 



