14 



GEOGRAPHICAL DEFINITIONS. 



of the sphere into equal hemispheres, the one 

 north, and the other south. All places situated 

 on the equator have no latitude, and the days 

 and nights are always of the same length. 

 Longitude is also reckoned in degrees of the 

 equator. 



Equinoctial is a great circle of the heav ens 

 corresponding to the equator on the earth. It 

 cuts the horizon of any place in the east and 

 west points; and when the sun arrives at this 

 circle, it rises and sets in these points, and the 

 days and nights are then equal all over the glolje. 

 Declination is reckoned north and south from it. 



Equinoxes are the times when the sun enters 

 the equinoctial points. This is about the 2 1st 

 of March and the 23d of September; the former 

 being the vernal, and the latter the autumnal 

 equinox. 



Evaporation is the conversion of water into 

 vapor, which, by this process, is raised into the 

 atmosphere, and, by a subsequent, but partial 

 condensation, forms clouds. As a very consid- 

 erable part of the earth's surface is covered 

 with water, which is constantly evaporating and 

 mixing with the atmosphere in the state of va- 

 por, a precise determination of the rate of evap- 

 oration must be of great importance in physical 

 geography. Accordingly, many -experiments 

 have been made by different philosophers to de- 

 termine this jjoint. From these we learn, that 

 evaporation is confined entirely to the surface 

 of the water, to which it is consequently pro- 

 portional. Much more vapor, therefore, rises in 

 maritime countries, or those interspersed with 

 lakes, than '\\\ inland countries. More also rises 

 during hot weather than cold ; hence the quan- 

 tity of evaporation depends upon the tempera- 

 ture. 



Geography is a description of the earth's sur- 

 face ; but the enlarged sense of the term in- 

 cludes a description, both of the inhabitants and 

 productions of the terrestrial globe., Mathemat- 

 ical o-eoo;rapliy describes the figure and magni- 

 tude of the earth, its diurnal and annual revolu- 

 tions, the cause of day and night, the succession 

 of the seasons, the method of determining the 

 positions of places on the earth's surface, and 

 ■he comparison of linear measures, with the 

 construction and use of maps. Physical s;eog- 

 »-«/)/(!/ delineates the principal features in the as- 

 pect of nature, by which the diversified regions 

 of the globe are distinguished from each other, 

 and portrays their agency on its inhabitants and 

 productions. Civil or Political geogi-aphy delin- 

 eates the empires, kingdoms, and states, which 

 occupy the surface of the earth, and exhibits the 

 monuments of human industry and skill. 



Glacie7-s is a name given to extensive fields 

 of ice among the Alps. Some of them clothe 

 the elevated valleys on these lofty regions, 

 while others envelope the sides and summits of^ 

 the mountains ; the former are denominated 

 lower, and the latter upper glaciers. Those in 



the valleys consist chiefly of solid ice. On the 

 summits of the mountains they are composed of 

 snow. 



Gravitation is the tendency which every par. 

 tide of matter has to every other particle, at 

 finite distances from each other. What is called 

 gravitation witii respect to the gravitating body, 

 is called attraction, in reference to the body 

 gravitated to. As all bodies, whatever may be 

 their nature oi- magnitude, are only aggregated 

 particles, gravitation takes place proportionally 

 between them; and this power thus becomes the 

 most universal agent of the material world. It 

 is by it that bodies retain their forms ; that the 

 component ))arts of the earth, and the other 

 planets, are not dissipated in the boundless re- 

 gions of space ; that terrestrial bodies, when 

 unsupported, descend to the earth ; that t-lie 

 planets and their satellites are retained in their 

 orbits ; and that the solar system itself main- 

 tains its place in the universe. 



Harbor is a place of safety for ships. 



Hemisphere is half the globe when it is sup- 

 posed to be cut through the centre by the plane 

 of one of its great circles. Thus the equator 

 separates the northern and southern hemis- 

 pheres ; the meridian divides the eastern and 

 western, and the horizon the upper and lower. 



Horizon is the great circle of the sphere which 

 divides its surface into the upper and lower 

 hemispliere. In this sense it is called tiie ra- 

 tiiinal h<irizon, and its plane passes through tiie 

 centre of the earth. 



Horizon sensible or visible is the small circle 

 of the sphere which bounds the observer's view, 

 and separates the visible from the invisible part 

 of the globe. 



Island is a portion of land wholly encompass- 

 ed by water; as Great Britain or Ireland. 



Isthmus is a narrow neck of land uniting two 

 continents, or frequently a peninsula to a conti- 

 nent ; as the Isthmus of Darien. 



LaJee is a portion of water, either entirely 

 surrounded by land, or having no other outlet 

 than a river, by which its contents are dis- 

 charged. When a lake is very extensive, it 

 obtains the denomination of sea ; as the Caspi- 

 an Sea. 



Latitude is the distance of a place from the 

 equator, and is estimated in degrees, minutes, 

 &c., on the arc of the meridian passing through 

 the place. Hence the latitude is either north 

 or south, as the place is situated on the north 

 or south side of the equator. The latitude of a 

 place is always equal to the elevation of the 

 pole above the horizon of that place. 



League is the 20th part of a degree. 



Longitude is the distance of a place eastward 

 or westward from the first meridian, and is meas- 

 ured on ail arc of the equator. It is by the 

 coiubination of latitude and longitude that the 

 situation of a place on the earth's surface is de- 

 termined. As a degree of longitude is the 360th 



