It may be a wooden ruler, but I like this.

Norman Davies in 'The Isles' devotes a chapter to this idea of Britishness ... and across his book, the equivalent of another chapter all over.

We could get like this trying to pen in types of learning (e-learning, online learning, CBT etc the same applies to many facets of the Internet, it's like trying to define the oceans, ignoring the current the run underneath the surface.