"All wonder," said Samuel Johnson, "is the effect of novelty on ignorance." Yet we are so created that without something to wonder at we should find life scarcely worth living. That fact does not make ignorance bliss, or make it "folly to be wise." For the wisest man never gets beyond the reach of novelty, nor can ever make it his boast that there is nothing he is ignorant of; on the contrary, the wiser he becomes the more clearly he sees how much there is of which he remains in ignorance. The more he knows, the more he will find to wonder at. My professional life has been a constant record...