1. The Message on the Monument
 2. Crossing the River
 3. The Zombie
 4. The Fog
 5. The Bull
 6. The Quicksand
 
 1.  Simply substitution. As a start, C is E.
 
 2.  First, take safety precautions. Then, consider what might be able
     to float, and is big  enough to carry you with it.
 
 3.  Import some London weather, with a little help from the French.
 
 4.  Think sharp here! The fog is thick stuff.
 
 5.  The bull is really a Marxist fish in disguise.
 
 6.  Well, if it was a mountain, you could.....