It groups particulars so as to lead up to a general conception which embraces them all, but which could not be fully understood until they had been estimated; or else it starts from some general conception, already familar to the mind, and as it moves along, casts its light upon numerous particulars, which are thus shown to be related to it, but which without that light would have been overlooked.

The author is most familar with the Leitz microscopes, which are furnished by Wm. Krafft, 411 West 59th St., New York city, or by the Franklin Educational Co., 15 and 17 Harcourt St., Boston.