[18] That Galileo had been in Rome before 8th January, 1588, a fact hitherto unknown to his biographers, is clear from the letter of that date addressed from Florence to Clavius. (Op. vi. pp. 1-3.) [19] See their letters to Galileo. (Op. viii. pp. 1-13.) [20] About £13.—[TR.] [21] About 7¼_d._ 100 kreuzers = the Austrian florin. [22] Op. xv. (Viviani), p. 336; and Nelli, vol. i. p. 44. [23] Op. xv. (Viviani), pp. 336, 337; Nelli, vol. i. pp. 46, 47; Venturi, vol. i. p. 11. [24] See the decree of installation of 26th Sept. (Op. xv. p. 388.) [25] Op. viii. p. 18; Nelli, vol. i. p. 51. [26] Op. xv. (Viviani), pp. 337 and 389. [27] Published by Venturi, 1818, vol. i. pp. 26-74. [28] Op. xv. (Viviani), pp. 339, 340. [29] Op. xv. (Viviani), pp. 337, 338. [30] Op. ii. pp. 1-6. [31] “Prodromus Dissertationum Cosmographicarum.” [32] Op. vi. pp. 11, 12. [33] Op. viii. pp. 21-24. [34] See Humboldt’s “Cosmos,” vol. ii. pp. 345, 346, and 497-499. [35] Op. xv. p. 390. His salary at first was 72 Florentine zecchini = £18, and rose by degrees to 400 zecchini = £100. (Op. viii. p. 18, note 3.) [36] Some fragments of these lectures are extant, and are included by Albèri in the Op. v. part ii. [37] Op. iii. (“Astronomicus Nuncius,” pp. 60, 61.) In his “Saggiatore” also he relates the circumstance in precisely the same way, only adding that he devised the construction of the telescope in one night, and carried it out the next day. [38] Nelli, pp. 186, 187. [39] History has acknowledged the optician Hans Lipperhey, of Middelburg, to be the inventor of the telescope. Compare the historical sketch in “Das neue Buch der Erfindungen,” etc., vol. ii. pp. 217-220. (Leipzig, 1865.) The instrument received its name from Prince Cesi, who, on the advice of the learned Greek scholar Demiscianus, called it a “teleskopium.” [40] Op. vi. pp. 75-77. [41] See the decree of the senate, 25th Aug., 1609 (Op. xv. pp. 392-393.) [42] Cosmo II. showed all his life a sincere attachment to his old teacher, Galileo. From 1605, before Cosmo was reigning prince, Galileo had regularly given him mathematical lessons during the academical holidays at Florence, and had thereby gained great favour at the court of Tuscany. [43] Op. vi. pp. 107-111. [44] See the letter of Martin Hasdal from Prague, of 15th April, 1610, to Galileo (Op. viii. pp. 58-60); also a letter from Julian de’ Medici, Tuscan ambassador at the Imperial court, to Galileo, from Prague, 19th April, 1610. (Wolynski, “Lettere inedite,” etc., p. 20.) [45] This reprint bore the following superscription: “Joannis Kepleri Mathematici Cæsarei Dissertatio cum Nuncio Sidereo nuper ad mortales misso a Galilaeo Galilaeo Mathematico Patavino.” Comp. Venturi, vol. i. pp. 99-120. [46] Op. vi. p. 121, note 1. [47] Compare the letters of Martin Hasdal, Alexander Sertini, and Kepler to Galileo in 1610. (Op. viii. pp. 60-63, 65-68, 82-85, 88, 89, 101, 113-117.)