144 



THE POPULAR EDUCATOR. 



larger maps they are marked at the distance of every 10 de- 

 grees ; and in larger still, at less distances ; the best being those 

 where they are marked at the distance of every single degree ; 

 but these, of course, must be of enormous size. The first 

 meridian, that of Greenwich, is known by its being marked 

 with on the map or the equator. On looking at the eastern 

 hemisphere, you will see this marked on the equator, in the 

 Gulj of Guinea, south of the coast of Guinea in Africa ; this is 

 the origin of the rectangular co-ordinates, the first meridian, and 

 the equator, and it is to this point that all measurements of 

 longitude are to be referred. On running up the meridian, 

 passing through this zero point, towards the north pole, you will 

 find that it passes through London in the British Isles ; this, 

 you know, is not strictly the case, the meridian of St. Paul's 

 Cathedral, London, being about 6' or geographical miles west 

 of the meridian of Greenwich; but this is so small in ordinary 

 maps, that it is scarcely perceptible, and certainly not mark- 

 able; whence the meridians of London and Greenwich are, for 

 common purposes, considered the same. The meridian of Green- 

 wich has been chosen as the first meridian, in preference to 

 that of London, because Greenwich is the site of the Royal 



its intersection with the equator are marked 0, to show that 

 latitude begins to be reckoned from these points. Each of the 

 four quadrants (or fourth parts) of these circles is marked with 

 degrees from to 90 reckoned from the equator to the poles. 

 In the map referred to, these degrees are marked only at the 

 distance of every 10 degrees, on account of its smallness; in 

 larger maps, they are marked at less distances ; and the best 

 are those in which they are marked at the distance of every 

 single degree ; but these, of course, must be of very great size. 

 In the same map, circles are made to pass through the corre- 

 sponding points on the upper or northern quadrants of the outer 

 or surrounding circle of each hemisphere, and of the upper or 

 northern half of the middle straight line extending from pole to 

 pole, at the distance of every 10 degrees ; these upper quad- 

 rants, and this upper half, actually denoting the northern por- 

 tions of meridians passing respectively through the points of 

 the equator marked longitude 20 W., longitude 160 E., and 

 longitude 70 E. These circles, which on the globe are parallel 

 to the equator, are, from the nature of the projection employed in 

 this map, not actually parallel to that line or to each other, being 

 drawn from different centres ; but they are still called parallels 



WESTEKN HEMISPHERE. 



EASTERN HEMISPHERE. 



MAP OP THE WORLD. 



Obstruction/. Accordingly, all meridians which cross the equator 

 to the right of that of Greenwich, are said to be meridians of 

 places in east longitude ; and all meridians which cross the 

 equator to the left of that of Greenwich, are said to be meridians 

 of places in west longitude. For example : if you look at Peking, 

 in China, on this map, you will find that it lies to the right of 

 the first meridian in the northern half of the eastern hemisphere, 

 between two meridians which cross the equator, the one being 

 that which is, or should be, marked at the point of intersection 

 110; and the other that which is, or should be, marked at the 

 point of intersection 120: this enables you to guess, by the 

 vicinity of Peking to the latter meridian, that its longitude is 

 about 116 east; now the actual longitude is 116 26' E. Again, 

 if you look at Buenos Ayres, in South America, on the same 

 map, you will find that it lies to the left of the first meridian in 

 the southern half of the western hemisphere, between two meri- 

 dians which cross the equator, the one being that which is, or 

 should be, marked at the point of intersection 50, and the other 

 that which is, or should be, marked at the point of intersection 

 60 : this enables you to guess, by the vicinity of Buenos Ayres 

 to the latter meridian, that its longitude is about 58 west; 

 now the actual longitude is 58 25' "VV. 



On the first meridian, the degrees of latitude are not marked; 

 but they are marked, in the Map of the World, on the circle 

 which surrounds each hemisphere. On this circle, the points of 



of latitude, and are used to enable us to determine the latitude 

 of any place on the map. Similar parallels of latitude are drawn 

 through the corresponding points on the lower or southern quad- 

 rants of the outer or surrounding circle of each hemisphere, in 

 the same manner, and for the same purpose. For example : if 

 you look at Peking, in China, on this map, you will see that it 

 lies between the equator and the north pole in the eastern hemi- 

 sphere, and just upon the parallel of latitude marked 40 at each 

 side of the map : this enables you to guess that the latitude oi 

 Pekin is nearly 40 north; now the actual latitude is 39 54' N. 

 Again, if you look at Buenos Ayres, in South America, on the 

 same map, you will find that it lies between the equator and the 

 south pole in the western hemisphere, and nearly in the middle 

 between the parallels of latitude marked 30 and 40 at each 

 side of the map : this enables you to guess that the latitude of 

 Buenos Ayres is nearly 35 south; now the actual latitude is 

 34 36' S. Having thus shown how to find separately the lati- 

 tude and longitude of any place on the surface of the globe by 

 means of the circles and lines drawn in the Map of the World, 

 it is easy for the student to combine these, and thus to deter- 

 mine the actual position of any place on the surface of the 

 globe. Thus, we have found that the city of Peking, in China, 

 is situated in lat. 39 54' N., and long. 116 26' E. ; and that the 

 city of Buenos Ayres is situated in lat. 34 36' S., and long- 

 5S25'W. 



