In this phrase the word “public” is used, not in the sense that it must be executed openly and in public, but in the sense of being so general and indefinite in its objects as to be deemed of common and public benefit. Each individual immediately benefited may be private, and the charity may be distributed in private and by a private hand. It is public and general in its scope and purpose, and becomes definite and private only after the individual objects have been selected. Saltonstall v. Sanders, 11 Allen (Mass.) 450