1884. 101 Trans. N. Y. Ac. Sci. 
In regard to the cause of coloration, some varieties are brecciated 
(the ‘‘dolomitic breccias” of Hitchcock), and in these the coloring 
material is generally oxide of iron, but in the Isle La Motte marble 
carbonaceous matter produced the color, the percentage of water and 
organic matter amounting to I.40. 
The PRESIDENT exhibited a large collection of similar colored mar- 
bles from Vermont, and remarked that he had studied and reported 
upon them at the Centennial Exposition. 
One variety from Plymouth has not yet entered into commerce. 
The demand for the colored marbles was increasing with the growing 
luxury of the timesand the appreciation of their beauty by the people. 
However, it was likely that the lighter-colored marbles would always be 
more extensively used, in the proportion of one hundred to one, than 
the colored. The Winooski was already in general use, though 
worked with difficulty on account of its density and its high content 
of silica, this substance being sometimes present in geodes. It had 
been often used, mistakenly, in this city for pavements, doorways, 
etc., but, like all the colored marbles, it both weathered and wore 
unequally, in consequence of its veins, etc. A most beautiful collec- 
tion of colored marbles had been exhibited from Maryland, rivalling 
any that had been used by the ancients in the Old World. Very few 
of these had yet been worked and polished, but many very brilliant 
specimens had been shown at the Centennial Exposition. In the far 
West, wherever the limestones have been affected by metamorphism, 
marbles occur in exceeding abundance, ¢.g., in the Rocky Mountains 
and the Sierra Nevada. They occurred also along the Alleghanies, 
as in West Virginia and Tennessee. In Vermont, at Rutland, 
white marbles occur of very great importance. At Pittsford, also, a 
heavy bed of marble occurs, 450 feet in width, the stratum standing 
nearly on its edge. In this vicinity some of the marbles have been 
used for building. 
He also exhibited a specimen of black marble, veined with white, 
from Southern Nevada. This rock had evidently been shattered, and 
the crevices infiltrated by white carbonate of lime. Iron oxide, some- 
times as a greenish silicate, was the almost universal coloring matter 
of the limestones. 
But recently native tin had been discovered in the Black Hills ; in 
fact, from the diamond to coal, the resources of that country were 
ample. So, too, the black marbles of the West will be ready when 
there will be a demand for them. 
In the Old World, the colored marbles, inan enormous series, came 
into use at an early date. Many of the quarries, known to the Greeks 
and Romans, are indeed as yet unknown to us; but many have been 
