GLOSSARY. 



Eocene. The strata deposited during the oldest of the tertiary 

 epochs, as, for example, the Paris Basin. 



Estuaries. Inlets of the sea into the land. The tides and fresh- 

 water streams mingle and flow into them. They include not 

 only the portion of the sea adjacent to the mouths of rivers, bu^ 

 extend txj the limit of tide- water on these streams. 



Exuvia. In geology, fossil remains. 



F. 



Fault. A dislocation of strata, at which the layers on one side 

 of a dike or fissure have slidden past the corresponding ones on 

 the other. These dislocations are often accompanied by a dike. 

 They vary from a few lines to several hundred feet. 



Feldspar. One of the simple minerals, and, next to quartz, one 

 of the most abundant in nature. 



Ferrvginous. Containing iron. 



Fluviatile. Belonging to a river. 



Formation. A group of rocks which were formed during a 

 particular period, or which are referred to a common origin. 



Fossils. The remains of animals and plants found buried in 

 the earth or enclosed in rocks. Some of these are but slightly 

 changed, others are petrified, and the organic replaced by mineral 

 matter ; some have decayed and left the impression of the bodies, 

 while others have been formed by rnir.eral matter deposited in 

 the cavities left by the decay of the organic body. These last 

 are called casts. The term petrifaction is applied to those causes 

 in which organic matter has been replaced by mineral substances. 

 The form and structure of the original body both remain. In 

 casts the exterior form alone is preserved. Fossils are also called 

 organic remains. 



Fossiliferous. Containing organic remains. 



G. 



Galena. An ore of lead, composed of lead and sulphur. 



Garnet. A simple mineral, which is usually red and crystal- 

 lized. It is abundant in most primitive rocks. 



Gneiss. A stratified primary rock, composed of the same ma- 

 terials as granite, but the mica is distributed in parallel layers, 

 which give it a striped aspect. 



Geology. A science which has for its object to investigate the 

 ■ Etructure of the earth, the materials of which it is composed, the 

 manner in which these are arranged with regard to each other; 

 and it considers the action of all natural causes in producing 

 changes, such as the effects of frost, rain, floods, tides, currents, 

 wind.s, earthquakes, and volcanoes. 



Economical Geology refers to the application of geological facts 

 and observations to the useful purposes of civilized life. 



