In this part of the analysis, I have found it necessary to deviate in some degree from the rigid rules of the exhaustive method I set out with. By me, or by some one else, this method may, perhaps, be more strictly pursued at some maturer period of the science. At present, the benefit that might result from the unrelaxed observance of it, seemed so precarious that I could not help doubting whether it would pay for the delay and trouble. Doubtless such a method is eminently instructive: but the fatigue of following it out is so great, not only to the author, but probably also to the reader, that carried to its utmost length at the first attempt, it might perhaps do more disservice in the way of disgust, than service in the way of information. For knowledge, like physic, how salutary soever in itself, becomes no longer of any use, when made too unpalatable to be swallowed. Mean time, it cannot but be a mortifying circumstance to a writer, who is sensible of the importance of his subject, and anxious to do it justice, to find himself obliged to exhibit what he perceives to be faulty, with any view, how indistinct soever, of something more perfect before his eyes. If there be any thing new and original in this work, it is to the exhaustive method so often aimed at that I am indebted for it. It will, therefore, be no great wonder if I should not be able to quit it without reluctance. On the other hand, the marks of stiffness which will doubtless be perceived in a multitude of places, are chiefly owing to a solicitous, and not perfectly successful, pursuit of this same method. New instruments are seldom handled at first with perfect ease.