Experiments on American and Foreign Building Stones. 3 
disintegration. It is certainly a most egregious mistake to con- 
struct any tall public edifice in such a manner as not to sustain ~~ 
its own dead weight, but there are operations scarcely less dis- © 
bine and which apply with equal force to structures profess- * 
ing to be enduring whatever be their height, their form, propor- 
tions or weight. es 
The usual trial of materials in small cubes is intended to fur- 
nish the relative strength or durability of the several species of 
materials to which it is applied. 
The stone used in the Washington National Monument, and re-— 
ferred to in the following comparisons of experiments, is the same 
as that mentioned under the name of “alum limestone,” in the 
report of the building committee to the Regents of the Smithso- 
pian Institution, Dec. 7, 1847 
~The marble quarries of Maryland, chiefly in the vicinity of 
the village of Clarksville, about thirteen miles from Baltimore, on & 
the line of the Susquehanna Railroad, contain two qualities of = 
marble; one fine grained and of beautiful uniform color, ap- - 
sotthing the character of statuary marble ; the other of inferior Py: 
quality, similar to the Sing Sing marble employed i in New York q 
in Grace Church and other public structures, of a somewhat coarse he 
and highly crystalline structure, and known to the quarrymen 
_ here under the name of ‘alum limestone.’ ”’* 
Trials of these two kinds of stone by the the process of Brardt — 
‘Were made by Dr. Page in 1847, and shewed that “an inch cube 
of the fine-grained marble lost in four weeks about one-fifth of a 
grain; and acube of the best or of the ‘alum stone,’ or coarse- 
grained marble from half a grain to a grain and a half?’t 
This indicated with dotitont press the inferior durability 
of the coarse-grained stone; since it underwent from two and a 
half to seven and a half times as much disintegration as the 
fine-grained variety. The fine-grained stone is understood to be 
- derived from the Taylor quarries, half a mile westward of Cock- 
eysville, and about a mile distant from the Griscom lime quarries + 
loose granules of the same rock. In some parts it is drotied 
to slo oping channels, lined. with skeletons of crystals and their 
alighly cohering nuclei 
removing the soil, the rock is found with alternating peak 
and cavities; its surfaces are more or less deeply tinged with the 
* Hints on Public Architecture, by R. D. Owen, p. 114. 
ae Chim. et de Phys, tom. 38. t Owen, p. 116. 
