Black Ale?

Having a cold one today I realized that I didn't know the difference between the various dark beers. My drinking companion was quaffing some New Belgium 1554 which is a Black Ale. Being more familiar with Irish beers, I figured that dark brews were stouts.

Not so: there are porters, stouts, dark wheat beers and probably a bunch more. I am having difficulty finding a definition for Black Ale, however. My trusty Wikipedia let me down on that specific search, but did yield "Schwarzbier" as a German Black Beer. Surely our Belgium friends have a similar drink, even if the recipe was lost for centuries until rediscovered in 1997.

Know anything about black ale? I would love to know.