“ He was fond of representing subjects in lantern or candle light, the effects of which he reproduced with a fidelity and skill which no other master has equalled. He frequently painted by the aid of a concave mirror, and to obtain exactness looked at his subject through a frame crossed with squares of silk thread. ”

“ Gifted with unusual clearness of vision and precision of manipulation, he cultivated a minute and elaborate style of treatment; and probably few painters ever spent more time and pains on all the details of their pictures down to the most trivial. ”