BUILDING AND ORNAMENTAL STONES. 351 



the so-called verdantique marbles, where the white veins of calcite or 

 dolomite lose their polish and crumble away more rapidly than the 

 serpentine composing the balk of the rock. Good examples of this are 

 to be seen in the bases of the two statues in front ot the City Hall in 

 Boston. Stones which, like many marbles, contain seams of mica, talc, 

 or other minerals, are objectionable for like reasons. Thus the marble 

 column supporting the statue of Lincoln in front of the City Hall at 

 Washington, though having been in place but some twenty years, is to- 

 day cracked from top to bottom, owing to the opening of one of ihese 

 seams of talc. It may be stated further that in the majority of marbles 

 and such other stones as are used chiefly for decoration work, those 

 variously colored lines and veins or structural features which give 

 the stone its chief beauty are in reality flaws and lines ot weakness. 

 There is many a beautiful imported marble which when sawn into a 

 thin slab will scarcely bear its own weight, but must be backed by 

 cheaper and strouger material. 



It may be said here that the essential qualities of a marble, aside from 

 color, which may vary almost indefinitely, are that it shall possess a text- 

 ure sufficiently compact and hard to take a smooth surface and acquire a 

 high polish. The chief defect in nearly all American marbles, and one 

 that does not as yet seem to be fully realized, is that they are too coarsely 

 crystalline. This not only renders the production of a perfect surface 

 difficult, but the cleavage facets frequently reflect the light from below 

 the surface in such a way as to destroy its uniformity. However good 

 the color may be, a stone of this nature must always rank lower than 

 one that is so fine grained as to appear non-crystalline or amorphous. 

 It is this fact, and this alone, that renders the American marbles now 

 in the market inferior to such as are imported from Belgium, the French 

 Pyrenees, Italy, or northern Africa. Those who are seeking new sources 

 of material will do well to bear this in mind.* 



Time of quarrying. — The season of year during which a stone was 

 quarried may also, in certain cases, be worthy of note. It is well kuowu 

 that many stones can be quarried with safety only during the summer 

 season, but Griiber goes a step further and states f that while the best 

 time for quarrying is during the summer, the freshly quarried material 

 should not be allowed to lie in the sun and dry too quickly, as it is lia- 

 ble thereby to become shaky. This he regards as particularly likely to 

 happen to sandstone. Stone quarried in winter, or during very wet 

 seasons, is liable, according to this authority, to have but slight tenacity 

 when dried, and to remain always particularly susceptible to the effects 

 of moisture. Finally, he states, a stone is liable to disintegration if 

 built immediately into a wall without seasoning. Stones for carved 

 work are to be quarried in the spring, since such longest retain their 

 quarry water, and this, if once lost, no subsequent wetting can restore. 



"Stone, Indianapolis, Iud., February, 1889. 

 Die Baumaterialien-Lehre, p. 61, 



