GEO 



GEO 



earth, the figures and areas of large por- 

 tions of the earth's surface, and the 

 variations of the intensity of gravity in 

 different regions, by means of direct ob- 

 servation and measurement. 



GEO'GRAPHY (7^, the earth, 7pa.^a), 

 to describe). The science which teaches 

 the knowledge of the earth. This is the 

 strict etymological meaning of the term, 

 which is thus distinguished from hydro- 

 graphy, or the description of water, or 

 seas, which constitute the greater portion 

 of the terraqueous globe. It differs from 

 cosmography, as a part differs from the 

 whole ; from chorography and topography, 

 as a whole differs from a part. 



1. Physical Geography, though, strictly 

 speaking, it denotes merely a description 

 of the principal features of the earth's 

 surface, usually includes the subjects of 

 climate and of temperature, the effect of 

 these agents on the condition of the 

 human race, and, generally, an account 

 of the animals and productions of the 

 globe. Hence it comprises the various 

 questions of Hydrography, Meteorology, 

 and Climate. 



2. Mathematical Geography is that 

 branch of the general science which is 

 derived from the application of mathe- 

 matical truths to the figure and dimen- 

 sions of the earth, to its relations with 

 the celestial bodies, to the relative posi- 

 tions and distances of places on its sur- 

 face, and to their representations by 

 globes or maps. 



3. Political Geography relates to his- 

 tory and statistics, and comprises all the 

 moral and social conditions of nations, as 

 inhabitants of the globe. 



GEO'LOGY (7?i, the earth, Aoyo?, an 

 account). Geognosy. A description of 

 the structure of the earth, and of the 

 theories entertained respecting its forma- 

 tion. A short tabular view of the suc- 

 cessive geological periods is here given, 

 with particular reference to the forms of 

 organic life most strikingly exhibited in 

 each: — 



I. The Fikst or Ancient Epoch. 



1. The period antecedent to the intro- 

 duction of life. The deposit of non- 

 fossiliferous rocks. 



2. The period of invertebrated animals, 

 as the most highly organized inhabitants 

 of the sea. The Silurian rocks. 



3. The introduction of fishes, the cha- 

 racteristic animals of the second fossili- 

 ferous period. The Devonian, or Old 

 Red Sandstone system of Formations. 



150 



4. The period marked by the presence 

 of vegetables and the first introduction 

 of reptilian animals. The Permian and 

 Carboniferous Systems. 



II. The Middle Epoch. 



5. The periods of the frog-like, bird- 

 like, and marine reptiles. The formation 

 of the New Red Sandstone, or Triassic 

 Series. Animals characteristic of the 

 Lias Formation. 



6. The periods of the gigantic land 

 reptiles, the flying reptiles, the gigantic 

 crocodilians, and the first introduction of 

 mammalian animals. Wealden and Oolitic 

 Formations. 



7. The periods of the Chalk and Green- 

 sand, during the deposit of which there 

 was probably a deep sea, covering a large 

 proportion of the existing land. Creta- 

 ceous Period. 



III. The Modern Epoch. 



8. The period of the pachydermatous 

 animals of the Paris basin, and of the 

 sub-tropical (?) fruits and animals of the 

 London and Hampshire basins. Older 

 Tertiary System. 



9. The period of various large animals 

 of the Middle Rhine valley, succeeded 

 by that of the mastodon and elephants 

 in North America, England, Northern 

 Europe, and India. Middle Tertiary 

 System. 



10. The period of the caverns and 

 gravel; with Carnivora, the Megaceros 

 and other gigantic ruminating animals, 

 and the elephants of Europe; and of 

 various gigantic animals in Asia, Ame- 

 rica, Australia, and New Zealand. Newer 

 Tertiary System. 



GEO'METRY (Yeco/xerpta, land-mea- 

 suring). The etymological meaning of 

 this term seems to imply that the mea- 

 surement of land was the most important, 

 perhaps the only, use to which this 

 science was at first applied. It now em- 

 braces the measurement of the earth and 

 of the heavens ; and it forms, with Arith- 

 metic, the basis of all accurate conclusions 

 in the mixed sciences. 



Geometry, Descriptive. A term em- 

 ployed by Monge to denote a systematized 

 method of geometry, by which a ground- 

 plan and an elevation are made to give 

 the form and dimensions of a building. 

 The projections of a point upon two 

 planes at right angles to each other, 

 called the planes of projection, being 

 given, the position of the point itself is 

 given. 



