HELP with glass material - cycles 2.71

I am trying to do a sort of glassed in world & am having problems getting the glass right.

This is simply glass [1.45] plus transparent @ 0.50% … transparent bottom

What am I missing, I want the ground [blue right now] to be visible but not with the double effect in the first image

try to add the solidify modifier to your sphere.
(the material is as expected. The problem is your mesh; and this can mean inverted normals or forgeting about the glass thickness)