[18] Totum Isocratis μυροθήκιον atque omnes ejus discipulorum arculas (Ad Att. ii. 1).
[19] Idque princeps Isocrates instituisse fertur, ... ut inconditam antiquorum dicendi consuetudinem ... numeris astringeret (De or. iii. 44, 173).
[20] The dates here given differ to some extent from those in F. Blass, Die attische Beredsamkeit (2nd ed., 1887-1898).
[21] Some authorities consider the Ad Demonicum spurious.
[22] This was shown by R. C. Jebb in a paper on “The Sixth Letter of Isocrates,” Journal of Philology, v. 266 (1874). The fact that Thebe, widow of Alexander of Pherae, was the daughter of Jason is incidentally noticed by Plutarch in his life of Pelopidas, c. 28. It is this fact which gives the clue to the occasion of the letter; cf. Diod. Sic. xvi. 14.
ISODYNAMIC LINES (Gr. ἰσοδύναμος, equal in power), lines connecting those parts of the earth’s surface where the magnetic force has the same intensity (see [Magnetism, Terrestrial]).
ISOGONIC LINES (Gr. ἰσογώνιος, equiangular), lines connecting those parts of the earth’s surface where the magnetic declination is the same in amount (see [Magnetism, Terrestrial]).