GEOLOGICAL SOCIETY OF PENNSYLVANIA. 365 



they appear to be irregular, both in size and direction, 

 but generally not wider than six inches. 



Veins of chlorite occur in clay slate and green stone. 



Veins of iron stone or free stone, this name having been 

 given to it in consequence of its great hardness, appear 

 to consist principally of very compact hornblende, with 

 chlorite and quartz. They are generally very large, 

 sometimes having been ascertained to be more than one 

 hundred feet wide. They have hitherto been found in 

 the clay slate. 



Veins of serpentine have been observed in the green 

 stone formations, occasionally crossing without specific 

 direction. 



In serpentine formations it is usual to remark veins of 

 one colour crossing a mass of a difierent colour. They 

 are not generally very wide, and are short and tortuaus. 



Veins of green stone are met with in serpentine as also 

 in the green stone itself, differing in this case by being 

 either more compact or less so than the environing rock. 

 They are, when occurring in the serpentine, very small. 



Veins of asbestos are found in the serpentine forma- 

 tions; are also met with in green stone; their width 

 being not great, and their position nearly horizontal. 

 They are remarked of considerable extent in the gold 

 districts of the United States in the talcose slate. 



Veins of agate are met with in serpentine near its 

 junction with clay slate. They are very minute and 

 irregular; but little information has as yet been received 

 of those occurring in Germany. 



Veins of calcareous spar in limestone are so common 

 in the transition limestone, that a particular description 

 of them is unnecessary. 



There are also other veins which appear under differ- 

 ent circumstances, and v^'hich deserve a notice here. 

 They may be styled veins within veins, as they are only 

 found in the vein stones or matrix of other veins. They 



