SECTION XIX. 271 Problem II. " The longitude or latitude of any place being given, how to find that placeon a globe or map." Ifonly the latitude of a place be given, the place itself may be easily found by castingyour eye eastwardand westward along that parallel of latitude in that part of the world where it lies, and the place (if it be marked on the globe) will soon appear. If the longitude only were given, guide your eye along that meri- dian northward or southward, and you will quickly see it. But if both longitude and latitude be given, then the place is immedi- ately found, for where the given line of longitude or meridian cutt the given line of latitude, there is the place required. These two problems also may be practised on a map aswell as on a globe. Problem III. " To find the distance of any two places on the earthly globe, or two stars on the heavenly." Here let it be noted that a degree of the meridian or of the equator, or of any great circle on the earthly globe is found by measure to be 691 or 70 English miles ; See Prob. XII. Sect. XX. Though geographers many times count 60 geographical miles to a degree, making them the same with the minutes of a degree for the greater ease in computation. Let it he noted also, that all the degrees on the meridians or lines of longitude on the globe are equal, because all those lines are great circles ; but in theparallels of latitude, thefarther you go from the equator the circle grows less and less, and con- sequently the degrees of those circles are less also And there- fore if two distant places are either both on the equator or have the same meridian, the number of the degrees of their distance on the equator or on the meridian being reduced to miles shews you their true distance : Bat if the two places are not both on the equator nor on the same meridian, you must find their true distance by the following method. To perform this third problem lay the quadrant of altitude from one place to the other, and that will shew the number of degrees of distance, which being multiplied by 60 geographi- cal miles, or by 70 English miles, will give the distance sought. Or you may take the distance between the two places with a pair of compasses and measure it upon the equator, which shews the distance in degrees, and then reduce them to miles. The quadrant of altitudes or a pair of compasses in the same manner, will shew the distance of any two stars on the heavenly globe, viz. in degrees, but not in miles. " Observe here, that though these methods will find the true distance of places on the globe, yet on a map the same methods are useless; because .ia maps or plain surfaces the degrees of
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