Trans. N. V. Ac. Set. 13 J. Apr. 30, 



Granyte. 



The bluish variety from Ouincy, Mass., his been used in many build- 

 ings and rarely shows as yet many signs of decay. In the U.S. Custom 

 House on Wall street, most of the huge blocks appear laid "on bed," 

 but, nevertheless, show some pitting in places, by the attack and par- 

 tial removal of the larger grains of hornblende. In the church at 

 Fourth street and Lafayette Place, erected in 1830, a little exfoliation 

 has been produced by street-dust on the faces of some steps. In the 

 Astor House, at Barclay street and Broadway, no decay was observed. 



In the fine-gramed granyte from Concord, N. H., employed in the 

 building on the southeast corner of Twenty-third street and Sixth 

 avenue, many of the blocks are set on edge, but the only change yet 

 seen is that of discoloration by street-dust and iron-oxide from the 

 Elevated Railway. 



The light-colored and fine-grained granyte of Hallowell, Me., has 

 been used for the construction of the City Prison, the Halls of Justice 

 or "Tombs," in Centre street. This stone consists of a white feldspar, 

 which predominates, a greyish-white quartz, which is abundant, and a 

 considerable quantity of a silvery white mica, thoroughly intermixed. 

 The rock possesses several properties — fineness of grain, homogene- 

 ity of structure, and freedom from iron, as shown by the color of the 

 feldspar — likely to render it durable ; the only unfavorable conditions 

 are the predominance of feldspar and the laminated structure. The 

 rock is a granitoid gneiss, with lamination often clearly marked ; these 

 markings at once show to the eye that most of the blocks are set, not 

 on bed, but irregularly on edge. 



The building is square and occupies an entire block. On a 

 study of the weathering, the south face was found to present an 

 exfoliation to the depth of one-eighth to one-fourth of an inch at many 

 points, up to the very summit of the building, particularly on the sides 

 of the pillars at the southeast entrance, on the ashlar near the south- 

 west gate, under and over the cornice and string pieces. In some 

 places the stone was loosened or peeled off in sheets of the area of a 

 square foot. The west front presents much exfoliation all over the sur- 

 face, though always thin ; it seems to begin chiefly along and near the 

 joints. In places, fragments have separated from the corners of the 

 blocks. The north front exhibits very little exfoliation ; so also the east 

 front, in a few small scattered spots. 



The exfoliation appears to be the result directly of the sun's heat, ex- 

 erted most intensely on the southern and western sides of the building. 

 An examination of the disintegrated material shows but little decom- 

 position ; a little kaolin may be distinguished in films, but the bulk of 



