BIBLIOGRAPHY. 187 
Dip. The inclination from the horizon, given in. terms of degrees, of a sheet, 
joint, heading, dike, or other structural plane in a rock. 
Drift. Sand and bowlders deposited by the continental glacier. 
Erosion. The wearing away of portions of a rock by such natural agencies as 
stream or ice action. 
Exfoliation. The peeling of a rock surface in sheets owing to changes of tem- 
perature or other causes. 
Faulting. The slippage of a rock mass or masses along a natural fracture. 
( See p. 40. ) 
Flow structure. The parallel arrangement of the minerals in granite or other 
igneous rock in the direction of its flowage during its intrusion. (See 
p. 25. 1 
Geode. A rock cavity lined with crystals. Geodes in granite are attributed to 
steam or gas bubbles. (See p. 50.) 
Grain in granite is practically the direction in which the stone splits " next 
easiest," the "rift" being that in which it splits most readily. (See 
p. 26.) 
Grout. A term applied to the waste material of all sizes obtained in quarrying 
stone. 
Grow-on. Quarrymen's term to designate the place where the sheet structure 
dies out, or the place where two sheets appear to grow onto one another. 
Hard-way. The direction at right angles to both rift and grain in which granite 
does not split readily. (See Cut-off ^) 
Heading. A collection of close joints. (See p. 39, and Pis. VIII, ,4, IX, B.) 
Heading-seam. See Joint. 
Hematite. An oxide of iron (Fe 2 3 ) which when scratched or powdered gives 
a cherry-red color. 
Igneous. A term applied to rocks that have originated in a molten condition. 
Joints. More or less steeply inclined fractures which cross the granite sheets 
and which are attributed to various stresses. (See p. 38.) 
Kaolin. A hydrous silicate of alumina derived from the alteration of feldspar. 
Kaolinization. The process by which a feldspar passes into kaolin. (See 
p. 55. ) 
Knots. A term applied by quarrymen to dark gray or black objects, more or 
less oval or circular in cross-section, which are segregations of black mica 
or hornblende formed in the granite while in a molten state. (See p. 49. ) 
English quarrymen call them " heathen." 
Knox hole. A circular drill hole with two opposite vertical grooves which 
direct the explosive power of the blast. 
Lewis hole. An opening made by drilling two or three holes near together 
and chiseling out the intervening rock. 
Limonite. A hydrous oxide of iron (2Fe 2 3 , 3H 2 0) ; a hydrated hematite, 
which, when scratched or po^vdered, gives a brownish rust color. 
Matrix. The general mass of a rock which has isolated crystals; sometimes 
called groundmass. 
Millimeter. French decimal lineal measure, the thousandth part of a meter 
or the tenth part of a centimeter. It is equivalent to nearly 0.04 inches, 
the meter being 39i£ inches. 
Monolith. A column or monument of one stone. 
