ABSTRACT
Joel H. Metcalf, of Taunton, Massachusetts, inverts the method in general use, and allows an average motion to the plate, so that the stars trail, claiming thus to be able to photograph fainter planets than would be the case if the planets had to trail. The discoverers are far less numerous than the asteroids themselves, some discoverers, as Max Wolf at Heidelberg and Charlois of Nice, claiming three-figure totals, practically all photographic; and some of the older observers, before the application of photography, numbered their discoveries by the score. The total mass of the minor planets is probably many times smaller than that of the moon, the estimates having decreased steadily from Le Verrier's suggested limit of a quarter of the earth's mass down to less than a three-thousandth of it. When the total number known was small, all were kept fairly under observation at successive oppositions and elements of orbit soon computed and corrected.
