I must inform you, however, that old pictures, deservedly celebrated for their colouring, are often so changed by dirt and varnish that we ought not to wonder if they do not appear equal to their reputation in the eyes of unexperienced painters, or young Students. An artist whose judgment is matured by long observation considers rather what the picture once was than what it is at present. He has by habit acquired a power of seeing the brilliancy of tints through the cloud by which it is obscured. An exact imitation, therefore, of those pictures is likely to fill the Student's mind with false opinions, and to send him back a colourist of his own formation, with ideas equally remote from nature and from art, from the genuine practice of the masters and the real appearances of things. Following these rules, and using these precautions, when you have clearly and distinctly learned in what good colouring consists, you cannot do better than have recourse to nature herself, who is always at hand, and in comparison of whose true splendour the best coloured pictures are but faint and feeble. However, as the practice of copying is not entirely to be excluded, since the mechanical practice of painting is learned in some measure by it, let those choice parts only be selected which have recommended the work to notice. If its excellence consists in its general effect, it would be proper to make slight sketches of the machinery and general management of the picture. Those sketches should be kept always by you for the regulation of your style. Instead of copying the touches of those great masters, copy only their conceptions. Instead of treading in their footsteps, endeavour only to keep the same road. Labour to invent on their general principles and way of thinking. Possess yourself with their spirit. Consider with yourself how a Michel Angelo or a Raffaelle would have treated this subject, and work yourself into a belief that your picture is to be seen and criticised by them when completed. Even an attempt of this kind will rouse your powers.