“In spite of everything, however, I still felt confident. Our calculations had been gone over again and again, and I could see nothing that in my opinion warranted the worst apprehensions of my kind critics. “It was with ill-restrained impatience that I waited for the first night when the moon should show herself in a suitable position for being observed; but the night arrived in due course. “Everything was in readiness. The movable portion of the roof of the building had been slid back, and the mirror of the siderostat stood bared to the sky. “In the dark, square chamber at the other end of the instrument, 200 feet away, into which the eyepiece of the instrument opened, I had taken my station with two or three friends. An attendant at the telephone stood waiting at my elbow to transmit my orders to his colleague in charge of the levers that regulated the siderostat and its mirror. “The moon had risen now, and her silvery glory shone and sparkled in the mirror. “‘A right declension,’ I ordered. “The telephone bell rang in reply. ‘Slowly, still slower; now to the left--enough; again a right declension--slower; stop now--very, very slowly.’ “On the ground-glass before our eyes the moon’s image crept up from one corner until it had overspread the glass completely. And there we stood in the centre of Paris, examining the surface of our satellite with all its craters and valleys and bleak desolation. “I had won the day.” PHOTOGRAPHING THE INVISIBLE. Most of us are able to recognise when we see them shadowgraphs taken by the aid of the now famous X-rays. They generally represent some part of the structure of men, beasts, birds, or fishes. Very dark patches show the position of the bones, large and small; lighter patches the more solid muscles clinging to the bony framework; and outside these again are shadowy tracts corresponding to the thinnest and most transparent portions of the fleshy envelope.