40 Descriptive Arrangement of Volcanic Rocks. 
character, ’ 
Resinous trachyte is generally by the name of pitch- 
sibel Ae ciive es 
stone ; wtreous by that of obsidian; and the same when 
med into globular concretions, perlite or pearlstone ; and 
the same vitreous basalt has been called gallinace by the 
French geologists. 
