These small crater-cones resemble, we are told, parasitic cones found on the sides of terrestrial volcanoes, and they are frequently seen on the floors of craters closely associated with light streaks. These crater-cones appear under a high sun as minute white spots and can be studied to advantage only with powerful instruments. The Italian astronomer, Maggini, observing the floor of the lunar crater, Plato, in 1916 noted that one of the small crater-cones that exist there in great numbers, was temporarily obscured from view by a cloud of reddish vapors, and Prof. W. H. Pickering, at Arequipa, Peru, observing the same region some years ago, believed that he saw evidence of change in some of these small markings. The crater, Plato, has probably been more carefully studied than any other portion of the lunar surface. It is sixty miles in diameter and may be seen even without a telescope as a dark "eye" not far from the northern edge of the moon. Its floor is one of the darkest objects in the moon--a dark steel-grey in color--and there is no doubt that for some unknown reason its dark hue deepens from the time the sun has an altitude of twenty degrees until after full moon. It has a brilliant white wall rising from 3,000 to 4,000 feet above its floor, crowned with several lofty peaks and intersected by a number of valleys and passes. The spots and faint light markings on the floor have been the object of much study with small or moderate sized instruments, and at least six of them are known to be crater-cones. Since they can only be studied to advantage with powerful instruments and as such instruments are rarely used for a systematic study of lunar markings, it is difficult to settle the controversy as to whether they have changed in appearance or have been at any time obscured by vapors. Most lunar observing is done--necessarily--with smaller instruments because the majority of astronomers appear to have accepted the view that the moon is a dead world, and those who are engaged in astronomical work with our greatest telescopes seem to feel that other fields of research will prove more fruitful. Possibly it is for this reason that we know so little about our nearest neighbor in space! There are at least as many unsolved problems confronting us on the moon as there are among the distant stars.