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 difficulties
of the thoughts and arguments themselves. Locke on the Human
Understanding is a work that has probably been often recommended to you.
Perhaps, if you keep steadily in view the danger of his materialistic,
unpoetic, and therefore untrue philosophy, the book may do you more good
than harm; it will furnish you with useful exercise for your thinking
powers; and you will see it so often quoted as authority, on one side as
truth, on the other as falsehood, that it may be as well you should form
your own judgment of it. You should previously, however, become guarded
against any dangers that might result from your study of Locke, by
acquiring a thorough-knowledge of the philosophy of Coleridge. This will