88 THE POPULAR SCIENCE MONTHLY. 



covered by the first, and leave the two in a quiet place where dust will 

 settle upon them, the unprotected margin of the second sheet will in 

 course of time become discolored and show a contrast. Many draw- 

 ings are so delicate that the dust can not be cleared from them without 

 injuring the drawings themselves. Unfixed charcoals and pastels are 

 the most delicate drawings of all, and require the most perfect protec- 

 tion against dust. The tidy housekeeper who dusts the unfinished 

 charcoal on the easel is alluded to with horror in the little treatises on 

 that art as the most destructive of all its enemies. As the charcoal 

 itself is nothing but unfixed dust, it obeys the housekeeper's feather- 

 brush only .too readily, and disappears with the other dust that means 

 nothing and is valueless. The housekeeper in such cases seems strik- 

 ingly like the blind destructive forces of the natural world which 

 respect genius and its productions no more than the commonest matter ; 

 she is like the sea which drowns Shelley and rolls the fragment of a 

 Greek statue among its pebbles. 



Protection against damp and dust may seem less necessary in the 

 case of oil-pictures, but here also it has its importance. Unquestion- 

 ably an oil-picture has a much stronger constitution than a water-color, 

 yet it is admitted that some colors used in oil-paintings are affected 

 unfavorably by moisture, and are insufficiently protected by pure oil. 

 De Mayerne affirms that indigo fades in oil without varnish, but is 

 durable under varnish, and the following quotation from Sir Charles 

 Eastlake's "Materials for a History of Oil-Painting" w T ill show the 

 peculiar kind of danger that may arise from damp : 



" The effect of moisture on verdigris, even when the color is mixed 

 with oil, as noticed by Leonardo da Vinci, shows that such a vehicle, 

 unless it be half resinified, affords no durable protection to some colors 

 in humid climates ; and the efficacy of resinous solutions, as hydro- 

 fuges, is at once exemplified by the fact that they answer the end 

 which (unprepared) oil alone is insufficient to accomplish. Colors 

 which are easily affected by humidity require to be protected accord- 

 ing to the extent of the evil. Whatever precaution of this kind was 

 requisite in Italy was doubly needed in Flanders. The superficial 

 varnish which sufficed in the extreme case referred to by Leonardo 

 was incorporated with the color by the oil-painters of the North. So 

 in proportion as the Flemish painters adopted a thinner vehicle, the 

 protecting varnish w r as applied on colors which the Italians could safely 

 leave exposed, at all events till a general varnish was spread over the 

 work. It will be remembered that this last method was unnecessary 

 in the original Flemish process, according to which the colors, being 

 more or less mixed with varnish, and being painted at once, remained 

 glossy, and needed no additional defense." 



It would not be safe, however, to conclude from this that a simple 

 coat of varnish is a perfect insurance against damp, for varnish itself 

 may be ultimately penetrated by damp, as Field showed in his chapter 



