138 



BOOK V. 



waxed margin through the first semi-circular hne, and reaching to the second, 

 there proceed straight hues converging toward the centre of the hemicycle ; 

 these mark the middles of intervening spaces lying between other straight hnes 

 which extend to the fourth semi-circular hne. But all lines whatsoever, from 

 the waxed margin up to the fourth hne, whether they go beyond it or not, 

 correspond with the graduated hnes which mark the minor spaces of a rod. 

 Those which go beyond the fourth hne correspond with the hnes marking 



A — Waxed semicircle of the hemicycle. B — Semicircular lines. C — Str.^ight 

 LINES. D — Line measuring the h.\lf. E — Line .measuring the whole. F — Tongue. 



