Usefully synonyms and antonyms

Though all true cast iron is brittle, in the sense that it is not usefully malleable, i.e.

We know, in short, that the water is not being usefully employed.

I feel I've spent a couple of hours very usefully.

The related literature is enormous (see the bibliographies to the special articles); it is indexed annually in Orientalische Bibliographie (Berlin), and is usefully summarized in the Theologische Jahresbericht (Berlin).

Several of the papers look into the practicalities of usefully exploiting human anthropomorphism in particular situations.