IT cannot be considered as superfluous or assuming to present the reader of the following lectures with a succinct characteristic sketch of the principal technic instruction, ancient and modern, which we possess: I say, a sketch, for an elaborate and methodical survey, or a plan well digested and strictly followed, would demand a volume. These observations, less written for the man of letters and cultivated taste, than for the student who wishes to inform himself of the history and progress of his art, are to direct him to the sources from which my principles are deduced, to enable him, by comparing my authors with myself, to judge how far the theory which I deliver, may be depended on as genuine, or ought to be rejected as erroneous or false.
The works, or fragments of works, which we possess, are either purely elementary, critically historical, biographic, or mixed up of all three. On the books purely elementary, the van of which is led by Lionardo da Vinci and Albert Durer, and the rear by Gherard Lairesse, as the principles which they detail must be supposed to be already in the student's possession, or are occasionally interwoven with the topics of the Lectures, I shall not expatiate, but immediately proceed to the historically critical writers; who consist of all the ancients yet remaining, Pausanias excepted.
