1883. 133 Trans. N. Y. Ac. Set. 



horizontal slabs, observed in St. Paul's churchyard, produced by the sag- 

 ging of the supporting masonry beneath the centre of the slab, is sim- 

 ply indicative of the flexibility of the material. 



Geikie states : " The results of my observations among our burial- 

 grounds show that, save in exceptionally sheltered situations, slabs ot 

 marble, exposed to the weather in such a climate and atmosphere as 

 that of Edinburgh, are entirely destroyed in less than a century. 

 Where this destruction takes place by simple comparatively rapid 

 superficial solution and removal of the stone, the rate of lowering of the 

 surface amounts sometimes to about a third of an inch (or roughly 9 

 millimetres) m a century. Where it is effected by internal displace- 

 ment, a curvature of 2}i inches, with abundant rents, a partial efface- 

 ment of the inscription, and a reduction of the marble to a pulver- 

 ulent condition, may be produced in about forty years, and a total dis- 

 ruption and effacement of the stone within one hundred. It is evident 

 that while marble is here utterly unsuited for out-of-door use." My 

 own conclusions, from observations in New York, is that, in the ceme- 

 teries within the city, the polish on vertical slabs is usually destroyed in 

 about ten years; that the inscriptions are only in small part effaced within 

 thirty to fifiy years, and are for the most part perfectly legible on the 

 oldest tombstones, dating 1798; and that, although the reduction of 

 the surface to a loose granular condition may reach the depth of ten 

 millimetres, the actual lowering of the surface seldom exceeds five 

 or six miUimetres, the internal disintegration is never sufficient to 

 affect sensibly the strength of the stone during the periods of exposure 

 which have been noted, and a slight flexure, sometimes to the amount 

 of twelve or fifteen millimetres, sometimes affects the centre of horizon- 

 tal slabs, two metres in length. 



In the cemeteries without the city, the polish may often survive 

 near the ground, on the faces ot vertical slabs, for over one hundred 

 and fifty years ; the granulation of the surface rarely exceeds a depth of 

 three or four millimetres ; and all the inscriptions remain perfect on 

 the oldest vertical tombstones, suffering partial effacement only on 

 horizontal slabs. 



Although these facts show the far greater durability of marble in 

 our dry and pure atmosphere, the frequent obliteration of inscriptions, 

 the general, and often rapid, granulation of the surface, and the occa- 

 sional Assuring of slabs, show that the decay of marble — in the varieties 

 hitherto long used in New York City — is steady, inevitable, and but a 

 question of time ; and with Geikie, 1, too, am convinced that, if un- 

 protected, such materials are utterly unsuited for out-of-door use, at 

 least for decorative purposes or cemetery-records, within the atmo- 

 sphere of a city. 



