ascertain

But all these are facts of nature, belonging to the case, ascertainable by experience and reason.

Descent would necessarily be traced through females, because the paternity of children was not ascertainable with certainty.

The only ascertainable fact is that he was the proprietor of the house with the sign of the Bear (l'Ours).

As for the elasticity of the ether, that is ascertainable at once from the speed at which it transmits waves.