394 THE POPULAR SCIENCE MONTHLY. 



White, black, yellow, red, or gray are the usual colors. On one 

 of these grounds, before it is dry, about one eighth of an inch of 

 cement of one of the other colors is laid, the pattern is pounced 

 on, and the parts outside the pouncing are scraped off with a 

 modeling-tool, a knife, or a bit of stick. "When the whole has 

 set, you have a picture or a pattern in two colors. This sort of 

 work has stood in England for over twenty years when executed 

 in the country, and in Italy the whole fronts of many large palaces 

 have been adorned in this way, and have stood for centuries. 



Public buildings built of polished marble, granite, porphyry, 

 jasper, agate, or onyx, or faced with these, are sometimes orna- 

 mented by inlaying pictures or patterns with colored marble or 

 precious stones ; but I do not know of any external example in 

 England. This work is called pietta dura. The Taj Mahal in 

 India is a celebrated example. There are plenty of slabs, basins, 

 vases, paper-weights, and jewelry imported from India and Italy 

 of pietra dura work. 



All external work in calcareous marbles soon perishes in the 

 atmosphere of London, whether plain or inlaid, and all incised 

 work filled with mastic so soon gets blackened that to execute 

 it is merely labor lost. The only other work that can be used 

 externally is in metal. Iron rusts unless constantly painted, and 

 almost all other metals turn black. Real block-tin, not tinned 

 iron, is said to stand the climate of London, but of course does 

 not lack its pall of soot. Iron plates tinned are much used in 

 Switzerland for the covering of steeples, but even there they get 

 rusty. Lead takes its own blackish gray, but, as it otherwise 

 stands the climate well, I wonder it is not more used for orna- 

 mental purposes, as vases, statues, roof-crestings, and the like. 

 When I was a boy, some plumbers' shops were ornamented with 

 leaden statues, vases, and ornamental cistern fronts. Lead is 

 still used for ornamental roof-crestings in France, often height- 

 ened by gold, black varnish, and color. Lead is still much used 

 for ornamental accessories in Holland or perhaps I ought to 

 say, was once used. Up to a short time ago there were leaden 

 statues and vases in the gardens of the stately mansions in Mark 

 Lane, near the Tower of London ; there are still some at Hamp- 

 ton Court, and they would do very well in the niches or on the 

 pedestals of our red brick fronts, if we could not afford bronze. 



It is unnecessary to speak of the ordinary freestones that 

 weather in London, the sandstones, the brick, both cut and 

 moulded, the red, yellow, or gray terra-cotta, for all these have 

 more or less granulated surfaces that can only be cleaned by 

 tooling or rubbing, but plaster has never of late, as far as I 

 know, been even tried I mean plaster of common sand and lime, 

 or, what is still better, of lime and marble-dust. Yitruvius tells 



