C *7 2 1 



egg ; fra&ure uneven, or earthy, and porous 5 

 commonly filled with particles of pumice, quartz, 

 fcoriae, Sec, ; very brittle ; does not efferyefce 

 with acids ; magnetic before it is heated, but not 

 after; contains filex, argill, and iron, 



b. Trass % or Terras ; refeuibles^ puzzolana; 

 though often the product bf pfeudo volcanos, or 

 external fires ; colour greyifli brown, or yellow- 

 ifli ; furface rough and porous ; fra&ure earthy, 

 rarely lamellar; found principally near Ander- 

 nach, in the vicinity of the Rhine ; alfp near 

 Frankfort, Cologne, Pleith, Sec. ; and there called 

 DurFftein; containing fragments of argillite anct 

 bafaltine, often branches of trees half cleared, and 

 impreffions of leaves, with mica, iron ore, Sec. 



'*■* • ' ' ■ II'- ■ ■ \ • I " '\\ t 



c. Tafa; a kind of puzzojana formed by na- 

 ture into a mortar ; colour brown, or reddifh 

 brown, brick red, or fpeckled with various co- 

 lours; fracture earthy; contains fand, fcoriae, 

 fragments of lava, Kmeftone and pumice ; often, 

 bafaltines and Vefuvian ; commonly inagnetic, 

 and not eafily decompofed by the a&ioji of the 

 ore. 



d. Pumice colour grey, rarely brown, or 

 blackened by fuliginous fumes ; furface rough and 

 fibrous, with elongated pores ; fometimes fibres 

 not difcernible ; fracture ftria,ted and open, un^ 

 even and fplintery • fragments oblorig, obtufe, and 

 irregular; brittle in a high degree ; fufible at 

 igo.' Q. irito a grey flagg. 



e, Piperino 1 



