236 ART OF BUILDING. 



nular, the grains varying from the size of a pin's head to 

 that of a nut or even larger. 



The color of granite depends upon the feldspar, which 

 is white, gray, yellow, green, &c ; the predominant color 

 is gray ; its beauty for building depends upon the inti- 

 mate mixture of the white feldspar and black mica. 

 Granite is not generally acted upon by fire or water, nor 

 does the frosts of our winters affect it ; it is about two and 

 a half times heavier than water. 



Granite is found extensively distributed over the whole 

 surface of the earth. It forms the principal part of the 

 highest mountains, and is found in low places, in beds, or 

 what are called ledges; single blocks of granite are 

 found resting upon loose earth. 



Beautiful varieties of granite for building are found in 

 Maine, New Hampshire and Massachusetts. 



Granite is used by the mason for the construction of 

 whole edifices, and for window and door stools and caps, 

 also for ashlar ; in some situations it is used undressed, 

 for foundations, cellar-walls, &,c. 



Sienite resembles granite in its external characters, 

 but differs from it in being- essentially composed of feld- 

 spar and hornblende; sometimes it contains quartz and 

 mica. Feldspar is the principal ingredient in sienite. 

 This stone is much less abundant than any other stone 

 which is used for building; it is found in the vicinity 

 of Boston, where it is extensively used. The Stone 

 Chapel and Tremont House in Boston, the State 

 Prison (old) in Charlestown are built with sienite. This 

 stone received its name from Siena, a city in Egypt, 

 whence the Romans obtained it for building and statuary. 



Gneiss resembles granite in its appearance, and is 

 of the same composition, but differs from it in always 

 being more or loss slaty, and when viewed in the mass, 

 appears to be formed of layers of different colors. Gneiss 

 is a hard rock, and answers very well for cellar and foun- 

 dation walls. 



Sandstone (Ores of the French, Freestone,) is com- 

 posed of grains of quartz united together by a cement, 

 which is variable in quantity and quality ; it may be 

 limey, clayey, or even silicious. The texture of some 

 sandstones is loose and porous, while some are hard and 



