CRATER-CONES.--These objects, plentifully distributed on the lunar surface, are especially interesting from their outward resemblance to the parasitic cones found on the flanks of terrestrial volcanoes (Etna, for instance). In the larger examples it is occasionally possible to see that the interiors are either inverted cones without a floor, or cup-shaped depressions on the summit of the object. Frequently, however, they are so small that the orifice can only be detected under oblique illumination. Under a high sun they generally appear as white spots, more or less ill- defined, as on the floors of Archimedes, Fracastorius, Plato, and many other formations, which include a great number, all of which are probably crater cones, although only a few have been seen as such. It is a significant fact that in these situations they are always found to be closely associated with the light streaks which traverse the interior of the formations, standing either on their surface or close to their edges. The instrumental and meteorological requirements necessary for a successful scrutiny of the smallest type of these features, are beyond the reach of the ordinary observer in this country, as they demand direct observation in large telescopes under the best atmospheric conditions. Some years ago Dr. Klein of Cologne called attention to some very interesting types of crater-cones, which may be found on certain dark or smoky-grey areas on the moon. These, he considers, may probably represent active volcanic vents, and urges that they should be diligently examined and watched by observers who possess telescopes adequate to the task. The most noteworthy examples of these objects are in the following positions:--(1) West of a prominent ridge running from Beaumont to the west side of Theophilus, and about midway between these formations; (2) in the Mare Vaporum, south of Hyginus; (3) on the floor of Werner, near the foot of the north wall; (4) under the east wall of Alphonsus, on the dusky patch in the interior; (5) on the south side of the floor of Atlas. I have frequently described elsewhere with considerable detail the telescopic appearance of these features under various phases, and have pointed out that though large apertures and high powers are needed to see these cones to advantage, the dusky areas, easily traced on photograms, might be usefully studied by observers with smaller instruments, as if they represent the _ejecta_ from the crater-cones which stand upon them, changes in their form and extent could very possibly be detected. In addition to those already referred to, a number of mysterious dark spots were discovered by Schmidt in the dusky region about midway between Copernicus and Gambart, which Klein describes as perforated like a sieve with minute craters. A short distance south-west of Copernicus stands a bright crater-cone surrounded by a grey nimbus, which may be classed with these objects.