obstinate perseverance that must triumph over all difficulties but those which are insurmountable."[201] _List of Kepler's published Works._ Ein Calender _Gratz_, 1594 Prodromus Dissertat. Cosmograph. _Tubingæ_, 1596, 4to. De fundamentis Astrologiæ _Pragæ_, 1602, 4to. Paralipomena ad Vitellionem _Francofurti_, 1604, 4to. Epistola de Solis deliquio 1605 De stellâ novâ _Pragæ_, 1606, 4to. Vom Kometen _Halle_, 1608, 4to. Antwort an Röslin _Pragæ_, 1609, 4to. Astronomia Nova _Pragæ_, 1609, fol. Tertius interveniens _Frankfurt_, 1610, 4to. Dissertatio cum Nuncio Sidereo _Francofurti_, 1610, 4to. Strena, seu De dive sexangulâ _Frankfurt_, 1611, 4to. Dioptrica _Francofurti_, 1611, 4to. Vom Geburts Jahre des Heylandes _Strasburg_, 1613, 4to. Respons. ad epist S. Calvisiii _Francofurti_, 1614, 4to. Eclogæ Chronicæ _Frankfurt_, 1615, 4to. Nova Stereometria _Lincii_, 1615, 4to. Ephemerides 1617-1620 _Lincii_, 1616, 4to. Epitomes Astron. Copern. Libri i. ii. iii. _Lentiis_, 1618, 8vo. De Cometis _Aug. Vindelic._ 1619, 4to. Harmonice Mundi _Lincii_, 1619, fol. Kanones Pueriles _Ulmæ_, 1620 Epitomes Astron. Copern. Liber iv. _Lentiis_, 1622, 8vo. Epitomes Astron. Copern. Libri v. vi. vii. _Francofurti_, 1622, 8vo. Discurs von der grossen Conjunction _Linz._ 1623, 4to. Chilias Logarithmorum _Marpurgi_, 1624, fol. Supplementum _Lentiis_, 1625, 4to. Hyperaspistes _Francofurti_, 1625, 8vo. Tabulæ Rudolphinæ _Ulmæ_, 1627, fol. Resp. ad epist. J. Bartschii _Sagani_, 1629, 4to. De anni 1631 phænomenis _Lipsæ_, 1629, 4to. Terrentii epistolium cum commentatiunculâ _Sagani_, 1630, 4to. Ephemerides. _Sagani_, 1630, 4to. Somnium _Francofurti_, 1634, 4to. Tabulæ mannales _Argentorati_, 1700, 12mo. FOOTNOTES: [199] The meaning of this passage is not very clear: Kepler evidently had seen and used logarithms at the time of writing this letter; yet there is nothing in the method to justify this expression,—"_At tamen opus est ipsi Tangentium canone._" [200] This was the objection originally made to Newton's "Fluxions," and in fact, Napier's idea of logarithms is identical with that method of conceiving quantities. This may be seen at once from a few of his definitions,