Yol.  49.] 
CLAYS  OF  THE  MALTESE  ISLANDS. 
123 
the  Clays  just  exceed  20  feet  in  thickness,  whereas  at  the  eastern 
extremities  of  these  valleys  and  of  others  situated  along  the  same 
line  the  thickness  barely  exceeds  10  feet  (see  fig.  4).  The  strata 
lying  between  the  northern  side  of 
the  Great  Fault  and  the  fault  which 
bounds  the  southern  side  of  St.  Paul’s 
Bay  dip  in  an  easterly  direction,  so 
that  the  thickest  part  of  the  Clays 
is  found  on  the  western  side  at 
Ghain  Toifiha  and  Karraba,  and  the 
most  attenuated  along  the  western 
boundary  of  the  Yasciar  Plain. 
In  Gozo  the  thickness  of  the  for¬ 
mation  is  not  so  variable,  owing  to 
the  comparative  absence  of  faults  and 
the  more  uniform  horizontally  of 
the  strata.  At  Port  Chambray,  and 
along  the  shores  of  the  bay  at  its  foot, 
the  Clay  outcrop  varies  from  30  to 
40  feet  in  thickness  :  but  the  taluses 
that  have  been  formed  along  the 
slopes  make  the  formation  appear  to 
be  at  least  120  feet  thick.  At  a 
distance  of  |  mile  east  of  Chambray  a 
vertical  section  shows  the  Clays  to  be 
only  10  feet  thick ;  this  thinning-out 
is  also  attributable  to  the  marked 
southerly  dip  of  the  overlying  strata. 
In  the  isolated  hills  and  the  smaller 
plateaux  this  dependence  of  the 
thickness  of  the  Clay-formation  upon 
the  dip  of  the  beds  that  overlie  it 
is  still  more  strikingly  shown. 
At  Ghain  Tofiiha,  in  Malta,  a  huge 
mass  of  rock,  having  an  area  of  about 
100  acres,  has  been  detached  from 
the  cliffs,  and  has  fallen  so  as  to  dip 
towards  the  cliff  of  which  it  was 
formerly  a  part.  The  Clay-bed  has 
been  dislocated,  and  while  on  the 
shore  side  it  shows  a  thickness  of  20 
feet,  at  the  point  of  dislocation  the  bed 
has  been  thinned  out  to  a  few  inches. 
But  it  is  not  only  along  the 
outcrops  that  these  differences  in 
thickness  occur.  The  formation  is 
overlain  conformably  by  the  Green¬ 
sands,  the  line  of  demarcation  between  the  two  being  as  a 
rule  well  defined ;  but  in  some  localities  the  transition  is  shown, 
by  the  admixture  of  the  Clay  and  Greensand,  to  be  of  a  very 
Fig.  4. — Diagrammatic  Section  from  the  Emtalileb  Valley  to  Citta  Vecchia  {Malta). 
