To most minds mystery is more fascinating than science. But when science itself leads straight up to the borders of mystery and there comes to a dead stop, saying, ``At present I can no longer see my way,'' the force of the charm is redoubled. On the other hand, the illimitable is no less potent in mystery than the invisible, whence the dramatic effect of Keats' ``stout Cortez'' staring at the boundless Pacific while all his men look at each other with a wild surmise, ``silent upon a peak in Darien.'' It is with similar feelings that the astronomer regards certain places where from the peaks of the universe his vision seems to range out into endless empty space. He sees there the shore of his little isthmus, and, beyond, unexplored immensity.