1887. | NEW YORK ACADEMY OF SCIENCES. 49 
Although the largest is only one-half of a crystal, it measures 
over four inches across the prism. Another measures three 
inches in width and two and one-half in length, and is perfectly 
terminated with the O plane. The others were one inch in 
diameter and from one to two inches inlength. One mass of 
rock ten by eight inches contained seventeen beryls from one- 
fourth to one inch in diameter. They were all found in a coarse 
granite in which were also imbedded beautiful almandite- 
garnets from one-eighth to one-fourth inch in diameter, but very 
bright, one beautiful flattened crystal of transparent garnet was 
found between plates of muscovite. 
Muscovite, crystallized out and implanted on orthoclase, two 
of these crystals measuring ten inches across. They were sym- 
metrically arranged. Cleavages showing beautiful hexagonal 
markings were also found. 
Crthoclase, one crystal which was broken and without pyrami- 
dal faces, measured six inches across. 
Washingtonite, in plates two inches square and one-eighth inch 
thick, penetrating the orthoclase. 
Epidote in crystals, 14 inches long, } across, showing faces, 
—li-1- and 7. 
Mr. Kunz also exhibited a photograph of the ‘‘ Great Orange 
Diamond,” which weighs ten carats more than the famous Koh- 
i-nur. Found at Kimberly, South Africa. 
Mr. JAmes F. Kemp presented a paper on’ 
THE GEOLOGY OF MANHATTAN ISLAND. 
Manhattan Island is about thirteen miles in length, from the 
Battery to Kingsbridge, and of a general width of two miles 
below Harlem, and three-quarters of a mile above. It is inclosed 
between the Hudson River on the west, the East River, Harlem 
River, and Spuyten Duyvil Creek on the east and north. ‘The 
direction or trend of its axis is N. 40° E. by the compass, which 
is somewhat wide of the true meridian, as the city avenues are 
recorded as N. 28° 584’ E., and differ but slightly from the strike 
of the rocks. 
The superficial area is approximately twenty square miles; the 
population of the island, according to the census of 1880, is 
1,163,673.7, The thickly settled portion, however, lies below 
59th street, and on this area, except at its northwest corner, 
1The paper was read, in the absence of Mr. Kemp, by Dr. N. L. 
Britton. 
2? Miscel. Doc. 1st Session 47th Congress, Vol. 24. 
