320 godon's mineralogical observations, &c. 



centric strata of o.iy dated iron, (hematites) which are sometimes 

 shining. Federal Hill, near Baltimore, affords on its flanks 

 numerous examples of this variety. When the grains of 

 which this sand-stone is formed are of great tenuity, they 

 take the appearance and characters of Tripoli, and probably 

 may be employed for the same uses;* such is that found on 

 a new road, which communicates with the Frederick road, 

 two miles from Baltimore. This last • variety very frequent- 

 ly accompanies a small bed of oxydated iron, which is cel- 

 lular, sometimes two inches thick ; but, most frequently, this 

 iron forms only a thin pellicle, which exhibits the colours ol 

 the iris. 



This sand-stone is found on the top of almost every hill 

 that occurs on the road from Baltimore to Washington ; it is 

 easiiy observed in the places where the soil has been washed 

 away by floods, or cut down for public roads. 



Sometimes the bed of quartzose stones has been itself agluti 

 nated by a ferruginous cement, and constitutes a sort of pud 

 ding-stone. This pudding-stone is often found of the thickness 

 of one or two feet. 



The rocks of transport, which are found in this soil are, in 

 general, the Amphibotic rock, (grunstein of the Germans) a 

 coarse quartz, and the variety of quartz designated by Werner, 

 under the name of Hornstein. 



Some fossil bodies are also found in this soil, namely, some re- 

 mains of shells, and particularly a deposit of fossil wood, which 

 is observed in a ravine at a little distance from Rock-Creek church. 

 This wood lies immediately under the ferruginous sand-stone, 

 in which it is sometimes, as it were, enveloped. It appears that 

 the ligneous particles of this wood, have been wholly replaced 

 by siliceous earth; the parts in which were interstices, as the 

 bark for example, are covered with a multitude of small crys- 

 tals of quartz, which belong to the variety prismed of 

 Hauy. 



All these sand-stones and ferruginous puddings, seem to 

 have a common origin. When the limits of this stratum shall 

 have been observed, and the space which it occupies shall have 



* To polish metals and hard stones. 



