HE.  J.  H.  COOKE  OK  THE  MAELS  AHD 
122 
[Feb.  1893, 
measurements  will  show  the  extent  to  which  the  thickness  varies 
in  different  parts  of  the  Islands  : — 
No. 
Locality. 
Thickness. 
Remarks. 
1. 
2. 
3. 
4. 
5. 
6. 
7. 
8. 
9. 
10. 
11. 
12. 
13. 
14. 
15. 
16. 
17. 
18. 
19. 
Ghain  Toffiha,  Malta. 
Chambray,  Gozo. 
Ras-el-Kammieh,  Gozo. 
Xagbra  Hill,  ,, 
Dabreni,  ,, 
Chelmus,  „ 
Dueira,  „ 
Giurdan,  ,, 
Ghar  lima,  ,, 
Gebel  Ciantar,  Malta. 
Boscbetto  Valley,  „ 
Citta  Veccbia,  „ 
Gebel  Imtarfa,  „ 
Ta  Binjemma,  ,, 
Wardia,  ,, 
Selmone,  ,, 
D  ingib  „ 
Gomerino,  ,, 
Fom-ir-rieb,  „ 
about  50  feet. 
55  60  ,, 
„  50  „ 
„  40  „ 
40  „ 
,,  40  „ 
„  20  „ 
„  40  „ 
„  40  „ 
„  15  „ 
»  25  „ 
„  20  „ 
„  14  „ 
„  15  „ 
»  20  „ 
from  10  to  20  feet. 
„  6  to  10  „ 
about  22  feet. 
»  6  „ 
1 
|  These  localities  are  in  a 
y  line  running  due  N.E. 
|  and  S.W. 
J 
These  localities  lie  west 
of  the  above  men¬ 
tioned  line. 
\ 
These  localities  are  in  a 
y  line  running  N.E.  and 
S.W. 
I  These  localities  lie  west 
1  of  the  above  men- 
J  tioned  line. 
The  pressure  of  the  overlying  strata  upon  the  plastic  Clays  has 
caused  the  original  thickness  of  the  formation  to  be  much  diminished 
in  many  parts  of  both  islands,  but  especially  so  in  the  smaller 
plateaux  and  in  the  isolated  hills  ;  while  in  other  localities  the 
taluses  that  have  been  formed  at  the  outcrops  have,  by  cloaking 
the  hillsides  and  cliff-sections,  caused  the  thickness  of  the  Clays 
to  appear  to  be  double  and  even  treble  of  what  it  really  is.  It  is  to 
these  extensive  taluses  that  the  many  exaggerated  estimates  of  the 
thickness  of  the  formation  are  due. 
Great  caution  is  needed  in  determining  where  the  lower  horizon 
of  the  Clays  is  situated,  as  no  little  experience  is  necessary  to  be 
able  to  distinguish  between  the  transition-bed  of  the  Marls  and 
Clays  and  the  bands  of  argillaceous  blue  limestone  which  are  dis¬ 
tributed  at  various  levels  throughout  the  Globigerina- rock. 
The  most  accurate  measurements  are  those  that  were  obtained  in 
the  well-shafts,  and  in  the  sections  that  were  cut  by  the  Engineer 
Corps  at  Gebel  Imtarfa  during  the  construction  of  the  new  road. 
The  extreme  thinning-out  that  the  above  measurements  indicate  is 
in  every  case  due  to  local  depressions.  If  a  line  be  drawn  from 
Gebel  Ciantar  to  Selmone  it  will  pass  through  the  localities  in  which 
the  Clays  are  most  attenuated.  This  attenuation  is  apparently  due 
to  the  north-east-by-east  dip,  which  the  strata  have  from  the  Great 
Fault  to  the  eastern  extremity  of  Malta.  The  pressure  of  the 
superincumbent  strata  on  the  Clays  is  therefore  the  greatest  in  that 
direction,  with  the  result  that  the  Clays  have  been  compressed  and 
thinned  out  at  the  outcrops  on  the  east  and  north-east.  In  the 
shafts  that  have  been  cut  in  the  Boschetto  and  Gomerino  Valleys 
