PHYSICAL GEOGRAPHY. 97 



course of the year is vertical, is called the Torrid zone ; 

 those parts below whose horizon the sun remains for a 

 certain space of time without setting or going below it, 

 are called the Frigid zones ; while the remaining parts, or 

 those contained between each of the frigid zones, and 

 the torrid zone, are called the Temperate zones. 



OF THE LATITUDE, LONGITUDE AND ELLIPTICITY. 



In order to mark any particular part or spot of the 

 Earth's surface, geographers have imagined it to be di- 

 vided by or surrounded with various circles. From the 

 extremities of the Earth's axis, called the Poles, an in- 

 definite number of semicircles are supposed to extend, 

 which are termed Meridians, and form the nearest 

 distance between the two Poles. Equidistant from the 

 Poles, and at right angles with the Meridians, there is an 

 imaginary circle surrounding the Earth, called the Equa- 

 tor from its apparently dividing the Earth into two 

 equal parts or hemispheres. Parallel with the Equator 

 there is supposed to be an indefinite number of circles 

 extending to the Poles by means of which, together with, 

 the Meridians, any particular spot may be designated. 



All circles are supposed to be divided into 360 

 parts called degrees, and each degree into sixty minutes ; 

 every Meridian therefore from the Equator to the Poles, 

 which is a quarter of a circle, will be divided into ninety 

 degrees commencing from the Equator : so that what- 

 ever distance any place may be in degrees either 

 Northward or Southward from the Equator, it is said to 

 have that number of degrees of North or South Latitude. 



The Equator is also divided into 360 degrees j but 

 these are reckoned from a certain Meridian called the 

 first Meridian, 180 degrees each way; which first Me- 

 ridian, as it is an arbitrary assumption, is generally con- 

 sidered by mathematicians as passing through the 

 capital, or rather the Observatory of their own country : 

 thus the first Meridian of Great Britain is supposed to 

 pass through the Royal Observatory of Greenwich ; the 

 first meridian of France, to pass through the Observa- 

 tory of Paris, &c. The number of degrees that the 



