Without it, the motives which impelled the strange pertinacity of my pursuit would have been unintelligible.

You use that expression with strange pertinacity.

I bought a beetle or two, and then my merchant, with strange pertinacity, returned to the bull-frog.

"Then, why not?" she persisted with a strange pertinacity.

" Strange pertinacity," he said, "in this Hakim, and a wonderful chance to interfere between that audacious Scot and the chastisement he has merited so richly.