Merging Results from Multiple Solr Instances

[Sangraal Aiken]

I have three instances of Solr on a single machine that I would like  
to query as if they were a single instance.

I was wondering if there's a facility, or if anyone has any  
recommendations, for searching across multiple instances with a  
single query, or merging the results of multiple instances into one  
result set.

-STA