210 PROFESSOR FORBES ON THE VISCOUS THEORY OF GLACIER MOTION. 
be developed at all ; the flow being- equal to the supply, no part of the vis viva would 
be expended in producing- internal pressures. With this concluding observation I 
commit the Plastic or Viscous Theory of Glaciers to the impartial judgment of those 
qualified to decide on its merits in explaining facts, and on the variety of difficult 
and complicated considerations which opposed and still oppose themselves to a com- 
plete development of it. 
Edinburgh, Jan. 10, 1845. 
