Yol.  49.]  ANNIVERSARY  ADDRESS  OE  THE  PRESIDENT.  95 
From  the  original  discoveries  of  the  Blanfords  in  India,  and 
from  the  further  evidence  of  the  Dwyka  Conglomerate  in  Africa, 
there  can  hardly  he  any  doubt  that  similar  deposits,  approximately 
contemporaneous,  extend  over  a  very  wide  area.  Indeed,  one 
cannot  help  calling  to  mind  that  even  in  Britain  the  Permian 
conglomerates  and  breccias  have  often  been  and  still  are  quoted  as 
evidences  of  a  Palaeozoic  ice-age.  That  something  very  remarkable 
occurred  in  the  physical  history  of  the  earth’s  crust  about  this 
period  (Permo-Carboniferous  interval)  is  perfectly  certain,  and  the 
results  of  this  action  may  be  traced  over  widely  separated  regions. 
It  is  quite  legitimate  to  seek  for  an  explanation  of  the  cause,  but 
geologists  especially  should  be  careful  how  they  accept  theories 
which  require  the  earth’s  axis  of  rotation  to  be  shifted,  or  which 
profess  to  account  for  general  climatic  conditions,  which  perhaps 
never  existed,  during  the  period  in  question. 
Date  and  Duration  of  the  Glacial  ( and  4 post-  Glacial’)  Period. — 
Two  well-known  authors  have  ventured  to  place  an  approximate 
chronological  value  on  the  whole  or  on  a  portion  of  Pleistocene 
time,  viz.  Prof.  Prestwich  and  Mr.  Mellard  Beade. 
Prof.  Prestwich  commenced  by  stating  his  belief  that  there 
is  no  valid  evidence  of  the  recurrence  of  Glacial  epochs  ;  and  he 
pointed  out  the  divergence  in  the  late  Dr.  Groffs  estimates  as 
to  the  beginning  of  what  is  usually  known  as  the  Glacial  Epoch, 
these  estimates  having  ranged  from  nearly  a  million  years 
ago  to  something  less  than  a  quarter  of  a  million  years  ago. 
Prof.  Prestwich  is  inclined  to  believe  that  a  much  smaller  figure 
than  the  lowest  of  these  will  suffice,  basing  his  calculations,  in  part, 
on  a  study  of  the  laws  affecting  the  growth  of  ice  and  the  motion 
of  glaciers.  The  observations  made  by  Steenstrup,  Bink,  and  others 
in  Greenland  tend  to  show  that  there  is  a  general  movement  of  the 
‘  inland  ice  ’  towards  the  sea,  and  that  it  concentrates  its  force  upon 
comparatively  few  points,  which  are  represented  by  the '  so-called 
ice-fields,  through  which  the  annual  surplus  of  ice  is  carried  off.  The 
velocity  of  the  ice  was  noted  in  seventeen  glaciers,  and  it  was  calcu¬ 
lated  that  these  move  at  rates  varying  from  30  to  50  feet  per  diem 
throughout  the  year,  the  rate  of  movement  not  being  materially 
influenced  by  the  seasons.  The  precipitation  in  Greenland  is 
thought  to  be  less  than  20  inches  per  annum.  From  the  above  data, 
and  bearing  in  mind  the  ratio  of  ice-front  to  rock-front  along  the 
whole  coast, 'the  total  annual  discharge  is  equal  to  a  fringe  of  ice 
one-eighth  of  a  mile  in  breadth,  or  one  mile  of  ice  in  eight  years. 
