By the above-described construction of floors, I would attempt to get rid of the obnoxious and expensive iron lath, so generally used. But it is more difficult to avoid their use on side walls, when the walls are to be plastered—and let me say here, that there can be no excuse for plastering the side walls in a fire-proof building, except for economy’s sake. The easiest and by all means the cheapest expedient when plastering is required is to build four inch walls, secured to the main exterior walls by iron straps. These will not conflict with the building laws, provided you build your walls thick enough at the outset. There is, however, no better way in which to finish interior walls than to line them with stone or marble, or both combined. Where decorative effect is desired, I would use stone with marble panels. Our native quarries now afford stone light enough in color to set at rest all objections that may be made to its use on the score of light. But if those should hold good the material might be marble paneled with marble, the former white, and the latter colored. Obviously the cheapest material for wall covering in natural materials would be slabs of white marble. Let us then make some comparison of figures, and see what can be done with this material. Iron lath, of the form generally used, cost $1.25 per foot. Three coat plastering costs nine cents per foot. A responsible dealer in marble informs me that he will put up inch slabs of Italian veined or Vermont marble for one dollar and a half per foot. Which, then, would you choose, polished marble at $1.50, or plaster, as good in appearance as that in any tenement house, at $1.34? This is a fair comparison for exterior walls or ceilings. Italian marble slabs can be procured in any quantity, from eight to nine feet long and three feet wide. In a room fifteen feet high, allowing four feet for wainscot and two feet for cornice, you may line your walls with one length of marble.