Merging disparate projects with repositories into a single solution with hg?

Question

I started two disparate projects in Visual Studio 2010, each with their own hg repository.

Later I decided that the two projects belonged under one solution, and thus one hg repository.

The new solution the following file structure:

SolutionFolder
   |---.hg
   +---Lib
   |    ∟ dlls
   +---Source
   |    ∟ Project_A
   |      ∟--.hg  
   |    ∟ Project_B
   |      ∟--.hg
   +---OverarchingSolution.sln

Is there a way that I can merge Project_A's and Project_B's changesets into the solution folder's repository?

Thus resulting in:

SolutionFolder
   |---.hg
   +---Lib
   |    ∟ dlls
   +---Source
   |    ∟ Project_A
   |    ∟ Project_B
   +---OverarchingSolution.sln

With all of the changesets from Project_A's and Project_B's landing in the SolutionFolder's repository?