GEO 



KitT^ct, a centre : applied in 

 to an orbit having the earth for its centre ; 

 having the same centre as the earth. The 

 geocentric latitude of a planet is its distance 

 from the ecliptic as seen from the earth ; 

 and its geocentric place is that wherein it 

 appears to us from the earth. See HELI- 

 ,OCENTRIC. 



GE'ODE, from j/i^^f , earthy. A round- 

 ish piece of mineral matter, sometimes 

 only an incrustation, generally more or 

 less hollow ; usually lined with crystals, 

 but in some cases loose earthy matter. 

 The geodes found in the green sand- 

 stone, near Sidmouth, are composed of 

 opaque chert on the outside, and contain 

 within mammillated concretions of beau- 

 tiful chalcedony, and occasionally perfect 

 though minute crystals of quartz. 



GEOD'ESTJ from <ytct, the earth, and 

 Satia, to divide. That part of geometry 

 which relates to the mensuration of sur- 

 faces. 



GEOG'NOSY, from y/i, the earth, and 

 pKua-tf , knowledge. A knowledge of the 

 htruoiure of the earth. Some have argued 

 that tliis term ought to be substituted for 

 the more common term geology (q. v.). 



GEOGRAPHY, from j-j, the earth, and 

 y{$vi, description. The science which 

 describes the surface of the earth, its 

 kingdoms, states, and empires, rivers, &c. 

 That branch which describes the natural 

 divisions and physical characteristics of 

 countries, is called physical geography ; 

 that which describes the political bound- 

 aries of kingdoms and their subdivisions, 

 the social and political state of the people, 

 the nature of their government, laws, and 

 institutions, is called political geography. 



GEOI/OGY, from y/j, the earth, audAeyaj, 

 discourse. That branch of natural his- 

 tory which investigates the disposition 

 Of the materials composing the earth's 

 crust, the relative situation of the differ- 

 ent orders of rocks, and their connexion 

 with each other, the changes they are 

 undergoing and have undergone, and ex- 

 amines into the relations which existed 

 between organised beings whose remains 

 are buried in the earth, and the physical 

 Circumstances under which they lived, 

 and finally, which ex plains, or endeavours 

 to explain, the proximate causes which 

 have operated the various chancres in the 

 organic and inorganic kingdoms of nature. 



GE'OM&NCY, yr lt earth, fjuti/Ttiot, pro- 

 phecy. Divination by points or circles 

 made on the earth. 



GKOM'ETR.I, a trihe of Lepidoptera, 

 comprising those of the nocturnal family, 

 in which the body is unusually slender, 

 and the probocis small and membranous. 

 Ibeii peculiar mode of progression has 

 t&v>d u s sai to be ityltd geomttra or mta- 



351 



GER 



s-ttrers. When about to advance they first 

 cling with t.'ieir anterior or squamous 

 feet, then elevate their body so as to form 

 a ring, in order to approximate the pos- 

 terior extremity to the anterior, or that 

 which is fixed ; they then cling with the 

 last feet, disengage the first, and move 

 the body forwards, when they recommence 

 the same operation. 



GEOMET'RICAI,, something relating to 

 geometry. Geometrical construction is the 

 representation of a proposition by geome- 

 trical lines. Geometrical curves are such 

 as may have their relations expressed by 

 a finite algebraic equation. Geometrical 

 locus is the line traced by a point, which 

 varies its position according to a given 

 law. Geometrical progression is when the 

 terms increase or decrease by equal ratios ; 

 or it is a series of quantities which are 

 continually proportional, every successive 

 term resulting from that which imme- 

 diately precedes it by a constant multi- 

 plier. Thus 2, 4, 8, 16, 32, 64, &c., is a 

 geometrical progression in which the 

 ratio is 2 ; and 16, 8, 4, 2,1, J,J,&c., is one 

 in which the ratio is j. 



GEOM'ETRY, from y/j, the earth, and 

 [MT^on , measure. Originally and properly 

 the art of measuring the earth, that is, 

 portions of its surface ; but according to 

 the present acceptation of the term, it 

 may be defined the science of extension 

 or of magnitudes considered simply, gene- 

 rally, and abstractly. It is called elemen- 

 tary when it treats of the properties and 

 proportions of right lines and right lined 

 figures. It is theoretical when its object 

 is the demonstration of certain geome- 

 trical propositions ; and practical when it 

 relates to the performance of certain geo- 

 metrical operations, such as the construc- 

 tion of figures. 



GEORA'MA, from yq, the earth, and 

 o^et/Mt, view; an apparatus which exhibits 

 a very complete view of the earth. It is 

 a hollow sphere, say 40 feet diameter, 

 formed by 36 bars of iron representing 

 the parallels and meridians, and covered 

 with cloth of a bluish colour to represent 

 water. The mountains, forests, &c., are 

 painted on paper and pasted on this cover. 

 It is a Parisian invention. 



GEOR'GIUM SIDDS. In astronomy (see 

 UHANCS). 



GEOSXU'RUS, a fossil saurine of the 

 oolite and lias formations. 



GERANIA'CE.E, geranium, or the crane's- 

 bill, is the type. A natural order of her- 

 baceous or shrubby Exogens. 



GER'FALCON. In ornithology, the Falco 

 candicans, Lin., a species most highly 

 pri/cd by falconers. 



GERM or GERMEN, the rudiment of the 

 young fruit and seed of vegetables, found 

 at the bottom of the piivil, aho the SM vl- 



