It has been clearly shown by analysis that the grounds for painting from the thirteenth to the sixteenth centuries were universally prepared either with 'gesso' (sulphate of lime, or 'plaster of Paris') or with a mixture of gesso and chalk; and apart from analysis, we have documentary evidence that, from the time of Giotto to that of Titian, gesso was considered the proper material. We now prepare our grounds with white lead, -a substance which has much greater body and is more easily prevented from cracking than sulphate of lime, -and we assume that it is as good. Mr. Holman Hunt, in his excellent paper on 'Artists' Materials,'* notices the point, and says that white lead 'may' be as good; but is by no means proved to be so. I think he should rather have said that there is every reason to believe that white lead is by no means equal to gesso. It is well known that many beautiful effects of colour are obtained by allowing a white ground to shine through the superimposed pigments, and Eastlake indeed attributes much of the charm of Van Eycks's pictures to his clever recognition of this principle of the preservation of inner light in painting. For the permanence of such effects it is, however, necessary that the ground should remain in its pristine whiteness, and while we have every chemical guarantee that the gesso will remain so, we have none with regard to the ground of white lead; indeed we have rather reason to surmise from its general behaviour that it will seize every available opportunity of deteriorating in colour, and will utilize to this end every possible influence both from the back and front of the picture, the back being usually the more vulnerable. It is perhaps a little troublesome on canvas to give proper elasticity to the gesso ground; but the old Italian Painters did it perfectly. On Panel there is no difficulty at all about the matter, and the painting surface thus produced is, according to all the historical evidence we possess, the best at our command.,,* Journal of the Society of Arts, April 1880,, ,