ART OF BUILDING. 237 



compact. The most common kinds for building are red, 

 white and gray. In New England the red sandstone is 

 extensively used by the mason for jambs, hearths, door 

 and window caps ; there are, however, some kinds of 

 sandstone which are easily affected by the frost, and of 

 course should not be used in our climate. We may ob- 

 serve several specimens of this in Boston, in which the 

 frost has caused them to crumble to pieces. 



These stones are extracted from quarries or from single 

 beds. In quarrying limestone gunpowder is necessary 

 in detaching the stone at first, after which it is split with 

 wedges. Granite is quarried by means of wedges only 

 when taken from single blocks, gunpowder is used when 

 in large masses, Sandstone is generally found in layers, 

 and it is quarried with the pick, wedge and lever. Gneiss, 

 generally, only requires the wedges and hammer. 



Brick is the next most durable material to stone for 

 building. Bricks are made of clay mixed with a certain 

 portion of sand ; the quality of the brick depends mainly 

 upon the proportions of these ingredients; if there is too 

 much clay, they shrink greatly in burning, and if too 

 much sand, the bricks are brittle and heavy. The proper 

 tempering of the raw material has another great effect 

 upon the quality, which is most effectually done by means 

 of a pttg-mill instead of the rude contrivance of our New 

 England brickmakers. This mill consists of a hollow, 

 upright cone, the interior being set with knives arranged 

 in a spiral form ; in this cone an upright shaft is placed, 

 armed in the same manner with knives, having a pivot at 

 the bottom on which it revolves. The clay being put in 

 at the top and a horse attached to the shaft, the knives 

 cut, separate, and most admirably prepare it for the 

 moulder's bench. 



Bricks are burned in kilns in this country, which, pre- 

 vious to the fire being applied, are covered with a coat of 

 clay and sand ; this being a bad conductor of heat keeps 

 it in. A kiln forty bricks long, thirtyseven wide and 

 thirty high, will require about sixty cords of pine wood, 

 or about half a cord to a thousand. The heat in burning 



VOL. i. NO, x. 21* 



