The prose of Mrs. Sigourney should not be compared, in its higher qualities, with her poetry—but appears to us essentially superior in its _minutiæ_. It would be difficult to find fault with the construction of more than a very few passages in the _Letters_—and the general correctness and vigor of the whole would render any such fault-finding a matter of hyper-criticism. We are not prepared to say whether this correctness be the result of labor or not—there are certainly no traces of labor. The most remarkable feature of the volume is its unusually extensive circle of illustration, in the way of brief anecdote, and multiplied reference to authorities—illustration which, while apparently no more than sufficient for the present purpose of the writer, gives evidence, to any critical eye, of a far wider general erudition than that possessed by any of our female writers, and which we were not at all prepared to meet with in one, only known hitherto as the inspired poetess of Natural and Moral Beauty. Would our limits permit us we would gladly copy entire some one of the _Letters_. As it is, we must be contented with a brief extract, (on the subject of Memory,) evincing powers of rigid thought in the writer. Few subjects are more entirely misapprehended than that of the faculty of Memory. For a multiplicity of error on this head Leibnitz and Locke are responsible. That the faculty is neither primitive nor independent is susceptible of direct proof. That it exists in conjunction with each primitive faculty, and inseparable from it, is a fact which might be readily ascertained even without the direct assistance of Phrenology. The remarks of Mrs. Sigourney apply, only collaterally, to what we say, but will be appreciated by the metaphysical student. I am inclined to think Memory capable of indefinite improvement by a judicious and persevering regimen. Were you required to analyze it to its simplest element, you would probably discover it to be a _habit of fixed attention_. Read, therefore, what you desire to remember, with concentrated and undivided attention. Close the book and reflect. Undigested food throws the whole frame into a ferment. Were we as well acquainted with our intellectual, as with our physical structure, we should see undigested knowledge producing equal disorder in the mind. To strengthen the Memory, the best course is not to commit page after page verbatim, but to give the substance of the author, correctly and clearly in your own language. Thus the understanding and memory are exercised at the same time, and the prosperity of the mind is not so much advanced by the undue prominence of any _one faculty_ as by the true balance and vigorous action of _all_. Memory and understanding are also fast friends, and the light which one gains will be reflected upon the other.