74 POPULAR LECTURES AND ADDRESSES. 



Thus the actual length of a minute of latitude 

 at the equator is '993 of the geographical mile, 

 at the pole it is 1*007 geographical miles. Ac- 

 cording to the foundation of the French metrical 

 system, the length of any meridional quadrant of 

 the earth or of a quadrant of the earth's equator 

 is very approximately, nearly enough for all 

 practical purposes of geography and navigation, 

 equal to 10,000,000 metres or 10,000 kilometres. 

 Thus 10,000 kilometres are equal to 5,400 nautical 

 miles, and as one kilometre is equal to '54 of a 

 geographical mile, a geographical mile is equal 

 to I '85 kilometres. The existence of the British 

 statute mile (5280 feet!) is an evil of not incon- 

 siderable moment to the British nation. I shall 

 never use the unqualified expression u mile" in 

 this lecture, nor, indeed, I hope on any other 

 occasion, as meaning anything else than the 

 geographical or nautical mile. The mean equa- 

 torial diameter of the earth is 6,876 miles, the 

 diameter from pole to pole is 6,853 miles. There are 

 60 times 360 or 21,600 minutes in the circumference 

 of a circle, hence the earth's circumference, which 



