^58 REPORT OF NATIONAL MUSEUM, 1893. 



after another as carelessly as bricks iu a wall. One-half of the amount 

 of material might have been more effective had proper taste been exer- 

 cised. It is Avorthy of remark that our architects, decorators, and arti- 

 sans of to-day seem to rely for effect wholly upon perfection of surface 

 and color, beauty of design and excellence of execution being alnu)st 

 Avholly overlooked. Everywhere are Hat surfaces, moldings, and machine- 

 made columns, all brilliantly polished, but nothing more. Yet the stone 

 will cut to as sharp an edge as the finest Carrara marble, and is emi- 

 nently adapted for bas-relief, small statues, busts, and objects of like 

 nature. Its transluceucy and ever varying shades of color, so far from 

 being defects, are, under proper treatment, actual merits, and it seems 

 almost unaccountable that they have so long been overlooked. Modern 

 manulacturers are not infrequently guilty of the utterly reprehensible 

 custom of seeking to improve the paler hues by paint or other coloring 

 materials applied to the back or unexposed side of the thin slabs, the 

 transluceucy of the stone being just sufficient to transnut the colors, 

 without permitting its cause to be discovered. This is especially the 

 case with much of the Parisian work now brought into America, but 

 unfortunately the practice is not confined to the French. 



CHEMICAL AND PHYSICAL PROPERTIES. 



As has been noted, the onyx marbles consist essentiallv of carbonate 

 of lime crystallized in the form of calcite; very rarel/as aragonite. 

 The results of quantitative chemical analyses of some of the princi- 

 pal varieties are given in the accompanying table. As will be noted, 

 the percentage of lime carbonate rarely falls below 90. J^-ext to the 

 hme, iron as carbonate or oxide forms the most prominent constituent, 

 and IS apparently the main cause of color variation, the tints depending 

 upon its state of combination, whether as carbonate or sesquioxide! 

 The small amounts of manganese may have some effect, but this could 

 not be ascertained with any degree of certainty. It is interesting to 

 note that the almost milk-white varieties from San Luis Obispo, Calffor- 

 nisi (25571), and Lower California (08240) carry, respectively, 3.03 and 

 2.70 per cent, of iron, calculated as carbonate (FeCO^). The most pro- 

 nonnced green and brown varieties carry but from 4.19 to 5.51 per cent, 

 of the carbonate, while the faintly tinted greens from Lower Calilbruia 

 run as high as 7.49 per cent. As a rule, it seems safe to say that the 

 green and red-brown colors are due to this ferruginous constituent, the 

 green colors containing the iron as a carbonate, and the ocher red, yel- 

 low, and browns being derived, therefore, by a process of oxidation^ as 

 noted on p. o48. Certain amber browns and yellows, (and iu one case a 

 bright tiesh-piuk color), as exemplified in the stones from Suisin City 

 and Sulpliur Creek, California, and in all the stalagmitic marbles, both 

 American and Egyptian, are, however, due to organic matter, all burn- 

 ing white, giving off the characteristic empyrenmatic odor, and showing 

 but the merest traces, if any, of metallic oxides. It ma v fnrther be said 



