A like close relation between master and scholar, the effect of which was to multiply works by joint labor, obtained among the contemporaries of Raphael as well as of Giotto.  The precise number of the genuine works of Raphael, owing to the cleverness of many of his pupils, will perhaps never be known.  Coindet ascribes to him from one hundred and eighty to two hundred Holy Families alone.  Some writers compute the entire number of his paintings at from five hundred to six hundred; others quote twelve hundred as authentic.  These exaggerated estimates only prove how extremely popular his designs became and the great number of pictures ordered from them, some of which no doubt had the advantage of being touched by his hand, while all in some way or other bear his mental impress.

Moreover, the great masters frequently changed their methods and styles, so that one might be mistaken for another, and at times studied and copied each other.  Andrea del Sarto’s copy of Raphael’s Leo Tenth passed undetected even by Giulio Romano, who had himself worked on the latter.  Rubens and Velasquez imitated and copied the great Italian masters, particularly Paul Veronese and Titian; the Caracci and their followers multiplied Correggios, Raphaels, and the chief Venetians; Girolamo da Carpi of Ferrara the same; and all with a degree of success that has greatly perplexed later generations:  their own works, in turn, as they became popular, experiencing from subsequent artists the same process of multiplication.  Of the celebrated Madonna of Loreto there are not fewer than ten rival claimants for authenticity; while sketches, studies, and works not directly imitated from, but partaking of the character of great artists, and often clever enough to be confounded with their undoubted works, are not rare.  Portraits, being direct studies from Nature, are difficult to decide upon.  Hence it is that criticism is so variable in its decisions.

Beside the above sources of perplexity, it encounters another obstacle from the restorations pictures have undergone.  Injured by time or obscured by repeated varnishings, they often require some degree of cleaning to make them intelligible.  Unfortunately, in most instances, the process is sheer assassination.  Many of the best works of public galleries have been subjected to scrubbings more analogous to the labors of a washtub than to the delicate and scientific treatment requisite to preserve intact the virgin surface of the painting.  Mechanical operators have passed over them with as little remorse as locusts blight fields of grain.  Their rude hands in numberless instances have skinned the pictures, obliterating those peerless tints, lights, and shadows, and those delicate but emphatic touches that bespeak the master-stroke, leaving instead cold, blank, hard surfaces and outlines, opaque shadows and crude coloring, out of tone, and in consequence with deteriorated sentiment as well as execution.  The profound knowledge and vigorous