106. With respect to remote periods of antiquity, we believe that the use of a hydrofuge oil-varnish for the protection of works in tempera, the only fact insisted upon by Mr. Eastlake, is also the only one which the labor of innumerable ingenious writers has established: nor up to the beginning of the twelfth century is there proof of any practice of painting except in tempera, encaustic (wax applied by the aid of heat), and fresco. Subsequent to that period, notices of works executed in solid color mixed with oil are frequent, but all that can be proved respecting earlier times is a gradually increasing acquaintance with the different kinds of oil and the modes of their adaptation to artistical uses. Several drying oils are mentioned by the writers of the first three centuries of the Christian era--walnut by Pliny and Galen, walnut, poppy, and castor-oil (afterwards used by the painters of the twelfth century as a varnish) by Dioscorides--yet these notices occur only with reference to medicinal or culinary purposes. But at length a drying oil is mentioned in connection with works of art by Aetius, a medical writer of the fifth century. His words are:-- * * * "Walnut oil is prepared like that of almonds, either by pounding or pressing the nuts, or by throwing them, after they have been bruised, into boiling water. The (medicinal) uses are the same: but it has a use besides these, being employed by gilders or encaustic painters; for it dries, and preserves gildings and encaustic paintings for a long time." "It is therefore clear," says Mr. Eastlake, "that an oil varnish, composed either of inspissated nut oil, or of nut oil combined with a dissolved resin, was employed on gilt surfaces and pictures, with a view to preserve them, at least as early as the fifth century. It may be added that a writer who could then state, as if from his own experience, that such varnishes had the effect of preserving works 'for a long time,' can hardly be understood to speak of a new invention."--P. 22. * * * Linseed-oil is also mentioned by Aetius, though still for medicinal uses only; but a varnish, composed of linseed-oil mixed with a variety of resins, is described in a manuscript at Lucca, belonging probably to the eighth century:-- * * * "The age of Charlemagne was an era in the arts; and the addition of linseed-oil to the materials of the varnisher and decorator may on the above evidence be assigned to it. From this time, and during many ages, the linseed-oil varnish, though composed of simpler materials (such as sandarac and mastic resin boiled in the oil), alone appears in the recipes hitherto brought to light."--_Ib._, p. 24. * * *