Volcanos  on  the  Banks  of  the  Rhine.  3 
made  me  keep  a fharp  look-out,  and,  on  my  approach  to 
Bonn,  was  ftruck  with  the  volcanic  forms  of  the  Seven- 
bergen,  or  Seven  Mountains,  about  two  leagues  from  the 
town,  on  the  other  fide  of  the  Rhine.  In  the  walls  and 
ftreets  of  Bonn  are  many  of  the  above  mentioned  co- 
lumns of  bafaltes,  and  the  pavement  of  the  Town  is  of 
lava.  The  ftone  in  general  ufe  for  building  here,  is  a 
very  compact  one,  a hard  volcanic  tuffa  like  that  of  Pia- 
nura  near  Naples,  and  of  the  fort  called  Piperno  in  Italy ; 
it  is  fomething  like  free-ftone,  but,  upon  near  infpeftion, 
is  mixed  with  fragments  of  lava  and  other  volcanic  fub- 
ftances. 
The  day  after  my  arrival  at  Bonn  I vifited  Wolcken- 
berg,  Tackenfelts,  and  Stromberg,  three  of  the  Seven- 
bergen,  and  found  the  two  firft  entirely  compofed  of 
tuffa,  and  the  laft  of  tuffa  and  lava : I dare  fay,  by  the 
fhape  and  appearance  of  the  reft  of  thefe  mountains,  I 
fhould  have  found  them  all  equally  compofed  of  the 
fame  volcanic  fubftances,  had  my  time  allowed  me  to 
t 
have  examined  them.  The  craters  on  the  mountains  I 
vifited  are  difcernable,  though  much  altered,  and  filled 
up  by  time  and  the  rubbifli  thrown  from  the  quarries 
that  are  conftantly  worked  on  their  tops.  On  each  fide 
of  the  Rhine,  moft  of  the  way  from  Bonn  to  Coblenz, 
particularly  between  Prohl  and  Andernach,  I perceived 
B % high 
