ject of dedicating his "Dialoghi delle Nuove Scienze" to the German Emperor, Ferdinand II., and of publishing them at Vienna, as he learnt from his friend and former pupil there, Giovanni Pieroni, that his implacable foes, the Jesuits, were all-powerful; that Ferdinand himself was entirely under their influence; and moreover that his bitterest foe, Father Scheiner, was just then at Vienna.[1] In the following year, however (1637), Pieroni succeeded by his prudent and untiring efforts, during the temporary absence of Scheiner, in obtaining a licence for Galileo's latest work,[2] and afterwards one at Olmütz also; but meanwhile he had sent the MS. by Micanzio[3] to be printed by the Elzevirs at Leyden, and, under the circumstances described by Pieroni, he did not prefer to bring out his book at a place where his bitterest enemies were in power.
He was at this time also deeply interested in a subject which originated as far back as 1610. It had occurred to him soon after the discovery of Jupiter's moons, by a series of observations of them, to make astronomical calculations and tables which would enable him to predict every year their configurations, their relative positions and occasional eclipses with the utmost precision; this would furnish the means of ascertaining the longitude of the point of observation at any hour of the night, which appeared to be of special importance to navigation. For hitherto the eclipses of the sun and moon had had to be employed for the purpose, which, however, on account of their rarity and the want of precise calculation, were neither entirely to be relied on nor sufficient. Galileo had offered his discovery,—the practical value of which he overrated,—in 1612, to the Spanish Government, and in 1616 tedious negotiations were carried on about it, which however led to no result,
