I am aware that to become critically acquainted with the diversity of styles is not the ultimate object to which the travels and the eager solicitude of the connoisseur aspire. His object is to make himself familiar with the handling of the most celebrated masters, and to distinguish copies from originals. Happy should I be, could I promise to accomplish so much! Even they might consider themselves fortunate, who dedicate their lives to such pursuits, were they enabled to discover any short, general, and certain rules for infallibly determining this delicate point! Many rely much upon history for the truth. But how frequently does it happen that the authority of an historian is cited in favour of a family picture, or an altar-piece, the original of which having been disposed of by some of the predecessors, and a copy substituted in its place, the latter is supposed to be a genuine painting! Others seem to lay great stress on the importance of places, and hesitate to raise doubts respecting any specimen they find contained in royal and select galleries, assuming that they really belong to the artists referred to in the gallery descriptions and catalogues. But here too they are liable to mistake; inasmuch as many private individuals, as well as princes, unable to purchase ancient pictures at any price, contented themselves with such copies of their imitators as approached nearest to the old masters. Some indeed were made by professors purposely despatched by princes in search of them; as in the instance of Rodolph I., who employed Giuseppe Enzo, a celebrated copyist. (See Boschini, p. 62, and Orlandi, on Gioseffo Ains di Berna.) External proofs, therefore, are insufficient, without adding a knowledge of different manners. The acquisition of such discrimination is the fruit only of long experience, and deep reflection on the style of each master: and I shall endeavour to point out the manner in which it may be obtained.[15]