crack-brained

I could plainly discover whence one family derives a long chin; why a second has abounded with knaves for two generations, and fools for two more; why a third happened to be crack-brained, and a fourth to be sharpers; whence it came, what Polydore Virgil says of a certain great house, NEC VIR FORTIS, NEC FOEMINA CASTA; how cruelty, falsehood, and cowardice, grew to be characteristics by which certain families are distinguished as much as by their coats of arms; who first brought the pox into a noble house, which has lineally descended scrofulous tumours to their posterity.

You insist on my introducing you to Dexter, and I refuse to trust you alone with th at crack-brained personage.

Keck, the editor of the "Trumpet," in asserting that Ladislaw, if the truth were known, was not only a Polish emissary but crack-brained, which accounted for the preternatural quickness and glibness of his speech when he got on to a platform--as he did whenever he had an opportunity, speaking with a facility which cast reflections on solid Englishmen generally.