Mrs. Sigourney has published a new work, under the title of 'Letters to Mothers.' The sentiments and principles inculcated in these letters, like everything from the pen of this amiable, intelligent, and excellent woman, are practical, useful, and imbued with the spirit of pure morality and elevated piety. Mrs. Sigourney's standard is found in the Bible. All her didactic works have immediate reference to the religion of the Bible; and none of her writings disclose a sentiment or a doctrine that is not founded upon the immoveable basis of genuine Christianity. We have no doubt that this will prove to be one of the most popular of her works. From the Daily Courant, Hartford, Conn.