Mr. Martineau is so thoroughly acquainted with the processes and results of spiritual experience, with the sciences of nature, and with the whole realm of metaphysical philosophy, and his own wealthy faculties are so tenacious in their activity and freshness, that every subject he touches receives novelty, light, and ornament. He is emphatically a teacher for the teachers,--a greater guide and master for the common guides and masters. Traversing the whole domain of human contemplation with the defining lines of analysis, clothing the severe materials of science with the colors of æsthetic art, he sheds on every theme the illumination of intellectual genius, and transfuses every thought with the distinctive sentiments of piety. Thus is afforded that rarest of all spectacles,--and the one now most needed by the cultivated religious world,--of a man who is greatly endowed at once as philosopher, poet, and Christian, and who with simultaneous earnestness in each capacity is devoted, by the whole labors of his life, to the instruction of mankind. For these reasons, we feel it a duty to attract as much attention as possible to Mr. Martineau's past and expected publications. The peerless intelligence, the bracing fidelity, the essential nobleness and catholicity, the tender beauty and reverence, of his utterances, his consummate mastery of the great topics he handles, seem to us fitted in a solitary degree to meet the highest wants of the age,--to do divine service in the conflict of scepticism, sensuality, and decay against all that is truest and purest in the religious faith and moral life of Christendom. Therefore, to persons who, unacquainted with the author's previous works, may read the papers here collected, we would recommend as the best books for educated and earnest Christian thinkers, Mr. Martineau's "Rationale of Religious Inquiry," the volume of his "Miscellanies" edited by the Rev. T. S. King, and the two series of "Endeavors after the Christian Life" recently republished in one volume by Messrs. Munroe and Company. We shall make up the rest of this introductory paper by quoting from some of Mr. Martineau's articles, not generally accessible, a few specimens of those thoughts which, if freely received in these times of theological doubt and turmoil, would lead many a religious thinker towards the truth and peace he covets. How clearly the following passage shows the true RELATION BETWEEN NATURAL AND REVEALED RELIGION.