Yol.  49.]  ANNIVERSARY  ADDRESS  OE  THE  PRESIDENT.  93 
western  glens.  Such  a  state  of  things  it  was  which  produced  the 
glacial  lakes  of  Lochaber,  and  he  quotes  the  authority  of  Hansen, 
who  maintains  that  it  was  the  great  decaying  mass  of  the  ‘  inland- 
ice/  and  no  mere  local  glaciers,  which  constituted  the  barriers  of  the 
lakes.  The  thinner  ice  towards  the  north-east  having  melted,  the 
watershed  at  the  head  of  the  Spey  became  sufficiently  open  to  admit 
of  water  passing  out,  and  a  lake  resting  on  the  surface  of  the 
decaying  glacier  would  in  the  first  instance  discharge  over  this  col. 
The  several  stages  are  thus  explained  and  the  corresponding  points 
of  escapement  indicated.  The  alluvium  of  Bohuntine  is  considered 
to  be  the  gravel  and  mud  that  fell  into  the  lake  from  the  front  of 
the  ice  when  it  stood  at  the  mouth  of  Glen  Boy  during  the  formation 
of  the  two  upper  lines.  It  also  serves  to  show,  in  opposition  to 
the  opinion  of  Prestwich,  that  the  lake  must  have  existed  for  a 
considerable  length  of  time.  During  the  last  stage  of  the  lake 
the  ice-dam  retreated  gradually  from  the  entrance  of  Glen  Boy  until 
it  finally  stood  across  the  mouth  of  Glen  Spean.  The  Author  then 
refers  to  the  ultimate  subsidence  of  the  lake  and  to  the  traces  of 
a  debacle. 
Theories  in  connexion  with  Glaciation. 
In  addition  to  the  mass  of  papers  dealing  with  what  is  usually 
known  as  the  Great  Ice  Age  of  Pleistocene  time,  there  have  been  a 
few  papers  in  which  subjects  connected  with  glaciation  have  been 
discussed  from  a  more  or  less  theoretical  point  of  view.  These 
may  be  grouped  as  follows  : — (1)  The  evidence  of  glacial  conditions 
in  the  Palaeozoic  era ;  (2)  Date  and  duration  of  the  [Pleistocene] 
Glacial  and  post-Glacial  Periods  ;  (3)  Misconceptions  regarding  the 
evidence  of  former  Glacial  Periods. 
Evidence  of  Glacial  Conditions  in  the  Palaeozoic  Era. — Dr.  Blanford 
is  of  opinion  that  the  existence  of  boulder-beds  over  areas  so  extensive 
and  so  widely  separated  as  the  Karoo  Beds  of  South  Africa,  the 
Gondwana  of  India,  and  the  Coal-measures  of  Eastern  Australia,  all 
of  which  boulder-beds  might  probably  be  of  the  same  age,  renders 
it  likely  that  these  were  really  contemporaneous  and  due  to  one 
great  Glacial  Period,  occurring  towards  the  close  of  the  Palaeozoic 
era.  He  even  goes  so  far  as  to  speculate  on  the  possibility  of  this 
presumed  Glacial  Period  having  terminated  the  Palaeozoic  era  by 
destroying  many  of  the  principal  forms  of  life.  How  far  the 
floras  of  these  beds  justify  such  a  supposition  must  be  decided  by 
those  well  versed  in  palaeobotany,  but  at  least  it  is  not  claimed 
