Longitude and Latitude

(by Cdr. Alastair Wilson, RN.)

In Verse 3 of This is the mouth-filling song of the race that was run by a Boomer, in Just So Stories, Kipling writes:

‘They ran thirty degrees, From Torres Straits to the Leeuwin’.

Conscious that a degree is not always of fixed length we asked Alastair Wilson, who was a Navigating Officer in the Royal Navy, to construe.

Alastair writes: Yes, old man Kangaroo was chased through 30 degrees of longitude, but a degree of longitude varies in length, depending on the latitude. A degree of latitude is the same length, whatever the latitude – it is, as near as makes no matter, sixty sea-miles in length (so one minute of arc is one sea-mile), whether at the equator, from 0º to 1º N or S, or at 89º N or S, The degrees of latitude are parallel to each other, and are an arc of a circle (they’re often referred to a ‘parallels of latitude’ (remember the film, 49th Parallel referring to the latitude of the Canada/USA border?).

But longitude is different: at the equator, a degree of longitude is the same (give or take) as a degree of latitude, but up at 60º N (or down at 60º S) each degree of longitude is only half a sea-mile long, while if you’re a yard from either Pole, then it is only about three inches long. Kipling was indeed accurate, but a little misleading. [A.W.]

Our note now runs as follows :

They ran thirty degrees, From Torres Straits to the Leeuwin Kipling is pretty accurate. Cape York, the northernmost point of Australia, on the south side of Torres Straits, is at 10°S 142°E., and Cape Leeuwin, right at the south-west of the continent, is at 34°S 115°E. The straight-line distance between them is about 3900 km. (2450 miles). [P.H.]