Investigable

Indeed it is only possible to learn any thing at all of these really curious and interesting aboriginal people, by cross-examining living men, and ascertaining what they remember to have heard their fathers or their grandfathers say. The period which goes back beyond this very brief depth of reliable and investigable tradition is an absolute blank.

This, of course, leaves aside those in value theory who maintain that values are not investigable by science.

The Paris population might hold bacteriological and epidemiological secrets, but to Yersin they were investigable and knowable ones.