Trans. N. V. Ac. Sa\ 132 Apr. 30, 



off particles ; e.g., in the white marble of the anticlinal axis at Suther- 

 land Falls, Vt. 



These results are confirmed by the appearances, familiar to all lithol- 

 ogists, in the study of thin sections of marble, the latent interstices 

 between the grains of calciie having been often developed by the insin- 

 uation of films and veinletsof iron-oxide, manganese-oxide, etc. While 

 a polished slab of marble, fresh from the stone-yard, may not be par- 

 ticularly sensitive to stains ; after it has been erected and used as a 

 mantelpiece over a fire-place, its increased absorbence for ink, fruit- 

 juices, etc., becomes strongly marked. On this property are founded 

 the processes, always preceded by heat, for the artificial coloring of 

 marbles. 



In the decay of the marble, largely Italian, in the atmosphere of 

 Edinburgh, Geikie has recognized three phases : 



1. Loss of polish, superficial solution, and production of a rough, 

 loosely granular surface. This is effected, Geikie states, by " exposure 

 for not more than a year or two to our prevalent westerly rains." The 

 solution of the surface may sometimes reach the depth of about a 

 quarter of an inch, and the inscriptions may become almost illegible 

 in sixteen years. 



In our own dry climate, however, these results do not appear. The 

 polish often survives ten years in our city cemeteries, and even for 

 over half a century near the ground, in the suburban cemeteries ; in 

 one instance, at Flatbush, it has remained intact for over 150 years, on 

 the tombstone of F. and P. Stryker, dated 1730. Inscriptions are 

 decipherable in St. Paul's churchyard back to the date of 1798, but 

 about one-tenth are illegible or obliterated ; the latter effect was never 

 seen in a single instance on the suburban stones, and is evidently due to 

 the acid vapors in the rain-waters of the city. 



2. Incrustation of the marble with a begrimed blackish film, some- 

 times a millimeter in thickness, consisting of town-dust, cemented by 

 calcium sulphate, and thorough internal disintegration of the stone, 

 sufficient, alter a century, to cause it to crumble into powder by very 

 slight pressure. 



Neither the crust nor any deep disintegration has been observed 

 in the oldest marble-tombstones in the cemeteries of New York ; 

 their absence is plainly attributable to the inferior humidity of 

 our atmosphere and the absence of smoke from soft coals. 



3. Curvature and fracture, observed in slabs of marble, firmly in- 

 serted into a solid framework of sandstone. This process consists in the 

 bulging out of the marble, accompanied with a series of fractures, and 

 has been accomplished by expansion due to frost. Tombstones are 

 never constructed in this wav, in our cemeteries ; but the curvature of 



