INTRODUCTION. 27 



-south poles; and the curve lines uniting them are other meridians 

 passing through every tenth degree of the equator, and showing 

 the longitude cast or west from the first meridian. The straight line 

 intersecting these meridians, and passing through the centre, is the 

 eauator, or equinoctial ; at proper distances from which, on each 

 side, are curve lines representing the tropics and polar circles. 



Maps and charts, especially the latter, are sometimes drawn on, 

 what is called Mercator's Projection, which is particularly of use 

 to navigators. In these the meridians and parallels are straight 

 lines, and the former equidistant from each other. The degrees 

 of longitude in every parallel are the same, while the degrees of 

 latitude are all unequal, being lengthened towards the poles. We 

 have annexed a Chart of the World on this projection. 



In maps of particular countries, the top is generally considered 

 as the north, the botiom as the south ; and the east is consequent- 

 ly on the right hand, and the west on the left. Where this rule is 

 not followed, a flower-de-luce is usually placed on some part of the 

 map, pointing towards the north, by which the other points may be 

 easily known. From the top to the bottom of the map are drawn 

 meridians, or lines of longitude ; and from side to side parallels of 

 latitude. The outermost of the meridians and parallels are mark- 

 ed with degrees of latitude and longitude, by means of which, and 

 the scale of miles commonly placed in the corner of the map, the 

 situation, distance, &c. of places may be found Thus, to find the 

 distance of two places, suppose London and Paris, by the map, we 

 have only to measure the space between them with the compasses, 

 and to apply this distance to the scale of miles, which shows that 

 London is 210 miles distant from Paris. It' the places lie directly 

 north or south, east or west, from each other, we have only to ob- 

 serve the degrees on the meridians and parallels ; and by turning 

 these into miles, we obtain the distance without measuring. Rivers 

 are described in maps by black lines, and are wider towards the 

 mouth than towards the head or spring. Mountains are sketched 

 on maps as on a picture. Forests and woods are represented by a 

 kind of shrub ; bogs and morasses by shades ; sands and shallows 

 are described by small dots ; and roads usually by double lines. 

 Near harbours, the depth of the water is expressed by figures de- 

 noting fathoms. 



Length of miles in different countries. ...There is scarce- 

 ly a greater variety in any thing than in this sort of measure : not 

 only those of separate countries differ, as the French from the Eng- 

 lish, but those of the same country vary in the different provinces 

 from each other, and from the standard. Thus the common Eng- 

 lish mile differs from the statute mile : and the French have three 

 sorts of leagues. We shall here give the miles of several coun- 

 tries, compared with the English by Dr. Halley. 



The English statute mile consists of 5280 feet, 1760 yards, or 8 

 furlongs 



The Russian verst is little more than $of a mile English. 



The Scotch and Irish mile is about If English. 



The Dutch, Spanish, and Polish, is about 3^ English. 



The German is more than 4 English. 



The Swedish, Danish, and Hungarian, is from 5 to 6 English, 



The French common league is near 3 English ; and 



The English marine league is 3 English miles, 



