Makefile question...

[kitepilot at kitepilot.com]

Hello virtual inhabitants: 

I have a C++ application scattered over several directories.
Each leaf directory has its own Makefile.
I want to write a top-level Makefile that traverses the tree and builds the 
application.
Makefile(s) are not one of my talents, and I cant' remember how to traverse 
the tree and fire up the nested Makefile(s). 

Any "make Guru" in the population?
Thanks!
ET