1886.] NEW YORK ACADEMY OF SCIENCES. 12T 



NOTES ON LOCAL MINERALOGY. 



It is a well-known fact that tourmaline is sparingly found on 

 the east side of Manhattan Island, except in boulders between' 

 Third and Fourth avenues and 99th and 104th streets. Lately, 

 however, I found a locality in an excavation in East 47th street 

 between First and Second avenues, where tourmaline is very 

 abundant in the top rock, consisting of coarse granite. In some 

 portions, tourmaline forms an essential constituent of the rock, 

 which then deserves rather the name of schorl. This rock also 

 contains traces of green tourmaline and green garnet. Green 

 feldspar is also frequently met with. 



From the same locality, I have some nicely crystallized speci- 

 mens of an iron pyrite, probably marcasite, found between the 

 lamellae of large lumps of mica and adhering to them. It took 

 a very sharp knife to separate the lamellae, whereby the crystals 

 were often destroyed, as the material is very thin and brittle. 



I further have to present some specimens of chalcopyrite in 

 epidote rock found in an excavation in East 96th street, between 

 Third and Lexington avenues. Some of the workmen found 

 pieces of considerable size, as large as a hen's egg. The epidote 

 rock appears at the surface from this locality up to 101st street. 



The President exhibited some tubes of earth built up by 

 pupae of Cicada on the floor of a dark, dry cellar. 



Dr. E. p. Stevens read a paper 



ON the SAN JUAN MOUNTAINS OF COLORADO. 



In the southwestern portion of the State of Colorado lies an 

 area of fifteen thousand square miles of eruptive rocks, extending 

 from Mt. Gunnison on the north, to New Mexico on the south, 

 and from Saguache on the east, to San Miguel on the west, one 

 hundred and twenty miles. Some fifty miles of the west end — 

 that portion which lies in the counties of Hinsdale, Ouray, San 

 Juan, and San Miguel — is the subject of this communication. 

 These mountains are unlike any found in the Eastern States, 

 and unique among those of the west. Looking at them from the 

 mesa country on the south, west, or north, they appear to rise 

 quite abruptly from their base, and are depicted on the sky in 

 sharp needles, minarets, and domes, and seem to stand alone 

 without any connection with any other range. But looking at 

 them from the east, they appear to be connected with ranges 

 that extend as far east as the great bend of the Rio Grande 



