We are surprised to find, in the Bolognese MS., olive oil mentioned as mixed with linseed oil in equal proportions, because we never yet heard of any successful experiment to render it drying. As it is the property of olive oil to turn lighter, not, as other oils, darker, a proof of successful experiment would be valuable. Pacheco mentions "salad oil" with honey, in a mixture of flour paste for grounds; but this may have been nut-oil. Besides the passages in Vasari and Lomazzo, which attribute to Lionardo the use of distilled oil, there is the recipe in the _Secreti_ of Alessio, which is conclusive as to the fact that linseed-oil was distilled and used to dilute amber varnish. We are aware that Mr Hendrie, in his valuable translation of Theophilus, strongly insists upon the superiority of distilled over other oil, but it does not appear ever to have been in general use.
The recommendation of amber varnish being the chief result of the commission, numerous authorities as well as recipes are given. "It appears to be mentioned in the Marciana MS., under the term 'carbone,' which has undoubtedly been written instead of 'caribe,' the Arabic and Persian term for amber." We would suggest the possibility that "carbone" may still be the right word, and mean amber, if it has been before mentioned in the MS.,--for one mode of making the varnish was to burn the amber to a "carbone," and then to grind it, as recommended in the recipe. In speaking of amber varnish as the result of Mrs Merrifield's research, we should be wrong in ascribing it to that alone; nor should we be doing justice to her own liberal and full acknowledgment of the prior recommendation of it by Mr Sheldrake in 1801, whose authority she quotes at much length, with detail of his experiments. "The use of amber varnish as a vehicle for painting, was revived and recommended so long ago as 1801, by Mr Sheldrake, in a paper published in the 19th volume of the _Transactions of the Society of Arts_. In these papers, Mr Sheldrake endeavours to prove that this varnish was used by the Italian painters; and as his opinion has been in a great measure confirmed by documentary evidence, his papers acquire additional interest from his having recorded the experiments made by himself in painting with this varnish."