TRACT 19.

TRIGONOMETRICAL TABLES, &C,

305

vero, partem canonis foecundi, partem canonis fcEcundissimi,cotineri. In tertia, reliquam.

“ Sane praeter inscriptas et circumscriptas, circulum etiamadficiunt aliae lineae recto:, velut Incidentes, Tangentes, etSecantes. Verum illas voces substantival sunt, non periphe-riarum relativse. Ac secure' quidem circulum linea rectatunc intelligitur, cum in duobus punctis secat. Itaque nonloquuntur bene geometrice, qui eductas e centro ad metas cir-cumscriptarum vocant secantes improprie, cum secantes ettangentes ad certos angulosvel peripherias referunt. Imm?)verb artem confundunt, cum his vocibus necesse liabeat utigcometra abs relatione.

“ Quare si quibus arrideat Arabum metaphora; quae quidemaut oinninb retinenda videtur, aut omnino explodenda ; utsemisses inscriptas, Arabes vocant sinus ; sic semisses circum-scriptoe, vocentur Prosinus Amsinusve; et eductce e centroTransinuosae. Sin allegoria displiceat, geometrica sane in-scriptarum et circumscriptarum nomina retineantur. Et cumeductEE e centro ad metas circumscriptarum, non habeanthactenus nomen certum neque elcgans, voceantur sane pro-scmidiametri, quasi protensae semidiametri, se habentes adsuas circumscriptas, sicut semidiametri ad inscriptas.”

Against the Arabic origin however of this word (sinus)may be urged its being varied according to the fourth de-clension of Latin nouns, like maims; and that if it were anArabic word latinized, it would have been ranked undereither the first, second, or third declension, as is usual in suchadopted words.

So that, upon the whole, it will perhaps rather seem pro-bable, that the term sinus is the Latin word answering to thename by which the Saracens called that line, and not thenword itself. And this conjecture seems to be rendered stillmore probable by some expressions in pa. 4 and 5 of Otho’s“ Preface to Rheticus’s Canon,” where it is not only said,that the Saracens called the half-chord of double the arc sinus,but also that they called the part of the radius lying betweenthe sine and the arc sinus versus, vel sagitta , which are evi-