Page:Carroll - Notes by an Oxford Chiel.djvu/40

2. Polar: i.e. by means of the 2 poles, 'North and South.' This is a very uncertain system of representation, and one that cannot safely be depended upon.

3. Trilinear: i.e. by means of a line which takes 3 different courses. Such a line is usually expressed by three letters, as W.E.G.

 

---

 

That the principle of Representation was known to the ancients is abundantly exemplified by Thucydides, who tells us that the favourite cry of encouragement during a trireme race was that touching allusion to Polar Co-ordinates which is still heard during the races of our own time, $\rho _{5}$, $\rho _{6}$, $\cos \phi$, they're gaining!'