You understand me, therefore, to recommend that those hours of the system which you are to impose upon yourself to employ in a certain manner are not to exceed the number you can ordinarily secure without interruption on every day of the week, exclusive of visitors, &c. &c.  Every advantage pertaining to the system I recommend is much enhanced by the uniformity of its observance:  indeed, it is on rigid attention to this point that its efficacy principally depends.  I will now enter into the details of the system of study which, however modified by your own mind and habits, will, I hope, in some form or other, be adopted by you.  The first arrangement of your time ought to be the laying apart of a certain period every day for the deepest thinking you can compel yourself to, either on or off book.

Having said so much on this point in my last letter, I should run the risk of repetition if I dwelt longer upon it here.  I only mention it at all to give it again the most prominent position in your studies, and to recommend its invariably occupying a daily place in them.  For every other pursuit, two or three times a week might answer as well, perhaps better, as it would be too great an interruption to devote to each only so short a period of time as could be allotted to it in a daily distribution.  It may be desirable, before I take leave of the subject of your deeper studies, to mention here some of the books which will give you the most effectual aid in the formation of your mind.

Butler’s Analogy will be perhaps the very best to begin with:  you must not, however, flatter yourself that you in any degree understand this or other books of the same nature until you penetrate into their extreme difficulty,—­until, in short, you find out that you can not thoroughly understand them yet.  Queen Caroline, George II.’s wife, in the hope of proving to Bishop Horsley how fully she appreciated the value of the work I have just mentioned, told him that she had it constantly beside her at her breakfast-table, to read a page or two in it whenever she had an idle moment.  The Bishop’s reply was scarcely intended for a compliment.  He said he could never open the book without a headache; and really a headache is in general no bad test of our having thought over a book sufficiently to enter in some degree into its real meaning:  only remember, that when the headache begins the reading or the thinking must stop.  As you value tho long and unimpaired preservation of your powers of mind, guard carefully against any over-exertion of them.

To return to the “Analogy.”  It is a book of which you cannot too soon begin the study,—­providing you, as it will do, at once with materials for the deepest thought, and laying a safe foundation for all future ethical studies; it is at the same time so clearly expressed, that you will have no perplexity in puzzling out the mere external form of the idea, instead of fixing all your attention on solving the