“When the thing is perceived, the idea conceived,” says Professor Whitney, “(men) find in the existing resources of speech the means of its expression—a name which formerly belonged to something else in some way akin to it; a combination of words,” &c.[13] For example, a word, W, which has always been the name of a thing, M, is applied to some new thing, N, which has been devised for the same use as M and answers the purpose better.[14] W thus represents both M and N for an indefinite time,[15] until M eventually drops into disuse and W comes to mean N and N only. The confusion necessarily arising from the equivocal meaning of W during this indefinite period, is entirely due, of course, to neglect of Horace’s advice to coin new names for new things.[16] Had a new name been given to N from the first, no difficulty could possibly have ensued, and our way would have been straight and clear. But as matters have fallen out, not only have we to determine whether W means M or N, whenever it is used during the transition period,[17] but we have to meet the arguments of those, never far off, who insist that because W meant N _finally_, it must have meant N at some bygone time when history and probability alike show that it meant M and M only. Examples, enough and to spare, of such arguments will be met with shortly. In consequence of the change of meaning which many military words have suffered, no translation of passages in foreign books containing ambiguous words should be relied upon, if access to the originals, or faithful copies of them, can be obtained. As an example of the necessity for this precaution, let us compare a few sentences relating to the siege of Jerusalem, A.D. 70, from the “Polychronicon” of Higden (_d._ cir. 1363), Rolls Series, iv. 429 _ff._, with the translations of them by Trevisa, 1385, and by the author of MS. Harl. No. 2261, of A.D. 1432-50. A (1) Inde Vespasianus ictu arietis murum conturbat (Higden). (2) Thanne Vaspacianus destourbed the wal with the stroke of an engyne (Trevisa). (3) Wherefore Vespasian troublede the walle soore with gunnes and other engynes (MS. Harl.). B (1) Josephus tamen ardenti oleo superjecto omnia machinamenta exussit (Higden). (2) But Joseph threwe out brennynge oyle uppon alle her gynnes and smoot all her gynnes (Trevisa). (3) Then Josephus destroyede alle theire instruments in castenge brennenge oyle on hit (MS. Harl.). C (1) Quo viso tanta vis telorum ex parte Titi proruit, ut unius de sociis Josephi occipitium lapide percussum ultra tertium stadium excuteretur (Higden). (2) Whan that was i-seie there fil so gret strenthe of castynge and of schot of Titus his side, that the noble knyght of oon of Josephus his felowes was i-smyte of that place with a stoon and flewe over the thrydde forlong (Trevisa).