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 tliese 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 times and 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, e.g., in the Rocky Mountains 

 and the Sierra Nevada. They occurred also along the AUeghanies, 

 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, in an 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 



