391 



ture of the earlh, the materials of which it if* conapoged, the- manner in 

 •which these are arrangetl, with regard to each other; and it considers 

 the action of all natural causes in producing changes, such as ihe effects 

 of frost, rain, floods, tidep, currents, winds, earthquakes and volcanoes. 



Economical Geology refers to the application of geological facts and 

 observations to the useful purposes of civilized life. 



Granite. An unstralified rock, composed generally of quartz, feld- 

 spar and mica, and it is usually associated with the oldest of the strati- 

 fied rocks. 



Graywacke, Grauwack^. A group of strata in the transition of rocka 

 — but the terra has been so indefinitely applied, that other names will 

 probably be substituted. 



Greenstone. A trap rock composed of hornblende and feldspar. 



Grit. A coarsegrained sandstone. 



Gypsum. A mineral, composed of sulphuric acid and lime, ard ex- 

 tensively used as a stimulant manure, and for making stucco and plaster 

 casts, &c. It is also called Plaster of Paris. 



BornLlende. A mineral of a dark green or black color, and which 

 is a constituent part of greenstone. 



Hornstone. A silicious mineral, approaching to flmt in its char- 

 acter. 



In Situ. In their original position where they were formed. 



LaminoE. The thin layers into which strata are divided, but to 

 which they are not always parallel. 



Lacustrine. Belonging to a lake. Depositions formed in ancient as 

 well as modern lakes, are called lacustrine deposits. 



Landslip. The removal of a portion of land down an inclined' 

 surface. It is in consequence of the presence of water beneath, whicb 

 either wajihes away the support of the superincumbent mass, or so sat- 

 urates the materials, that they become a slippery paste. 



Line of Bearing, is the direction of the intersection of the planes of 

 the strata with the plane of the horizon. 



Lignite. Wood naturally carbonized and converted into a kind of 

 coal in tbe earlh. 



Littoral. Belonging to the shore. 



Loam. A mixture of sand and clay. 



