Vitrification would not depend upon the introduction of glass only,--calcined bones, which, it is now known, were much used in vehicles, will produce the same result. In a note, page 345, Mr Eastlake says that he requested Mr Marris Dimsdale to analyse a fragment of a picture by Cariani of Bergamo, (a contemporary and scholar, or imitator of Giorgione;)--the result being, that "one portion ran fairly into a vitrified state. Hypothetically," adds Mr Dimsdale, "I should say it had burned bones in it." And again, "Every colour mixed with phosphate of lime, (calcined bones,) vitrifies when exposed to strong heat. As Venetian pigments vitrify, might not phosphate of lime have been used as a dryer?" We cannot but suspect any medium under which the pigments will not vitrify. The publication of Mr Eastlake's most important and valuable volume, rather strengthens our reliance upon the various communications made to us by Mr Rainier. For instance, many years ago, we used, at his recommendation, sandarach, dissolved in spike oil, and then mixed with the oil heated. It may not be amiss here, as sandarach is now so strongly recommended, and shown at least to have formed a part of one of the precious vehicles, to state the result of its use some twenty years ago. A picture we then painted with it, is still without a crack, extremely hard, and though by no means well painted, is good in texture, and resembles in the quality of the pigments very much that of the old schools. Though for some years shut up in a portfolio, the colours do not appear to have undergone any change. Although it will not probably be found that borax was used in the good recipes by name, it may have been in the Venetian glass--at all events, though we are now rather in search of what _was_ in use, than what may be useful and good in itself, as it were _de novo_, it may be worth while to remember the double facility it offers of use with oil or water, both or either; and it may be added that the experience of some years shows nothing against it and much in its favour. We have thought it to be a preservative of colours. In our review of M. Merimée, we threw out a conjecture that it might have been the Gummi Fornis in the recipe of Theophilus--and which M. Merimée believed to be copal. But we are quite convinced of our error by the arguments--we might say proofs--adduced by Mrs Merrifield, contained in a note, in her admirable and most useful volume, "Cennino Cennini." That it was sandarach there can be no doubt; and we were in consequence induced to try the making the vehicle according to the recipe of Theophilus, and perfectly succeeded. It has a pleasant lustre, not that somewhat disagreeable shine which is often visible in pictures painted with copal. For the quality of sandarach Mrs Merrifield quotes Raffael Borghini, from his "Reposo"--"If you would have your varnish very brilliant, use much sandarach."