Joshua Bates, a partner in the firm of Messrs. Baring, has conferred a donation of $50,-000 towards the forming of a public library in Boston. The only condition is, that the building shall be an ornament to the city —that there shall be room for one hundred to one hundred and fifty persons to sit at reading tables—that it shall be perfectly frea to all, with no other restrictions than may be necessary for the preservation of the books.