[68] Ludovico delle Colombe in a tract Contra Il Moto della Terra, which is reprinted in the national edition of Galilei’s works, Vol. III.
[69] In a letter of May 4th, 1612, he says that he has seen them for eighteen months; in the Dialogue on the Two Systems (III., p. 312, in Salusbury’s translation) he says that he saw them while he still lectured at Padua, i.e. presumably by September 1610, as he moved to Florence in that month.
[70] Historia e Dimostrazioni intorno alle Macchie Solari.
[71] Acts i. 11. The pun is not quite so bad in its Latin form: Viri Galilaci, etc.
[72] Spiritui sancto mentem fuisse nos docere, quo modo ad Coelum eatur, non autem quomodo Coelum gradiatur.
[73] From the translation by Salusbury, in Vol. I. of his Mathematical Collections.
[74] The only point of any importance in connection with Galilei’s relations with the Inquisition on which there seems to be room for any serious doubt is as to the stringency of this warning. It is probable that Galilei was at the same time specifically forbidden to “hold, teach, or defend in any way, whether verbally or in writing,” the obnoxious doctrine.
[75] This is illustrated by the well-known optical illusion whereby a white circle on a black background appears larger than an equal black one on a white background. The apparent size of the hot filament in a modern incandescent electric lamp is another good illustration.
[76] Actually, since the top of the tower is describing a slightly larger circle than its foot, the stone is at first moving eastward slightly faster than the foot of the tower, and therefore should reach the ground slightly to the east of it. This displacement is, however, very minute, and can only be detected by more delicate experiments than any devised by Galilei.
[77] From the translation by Salusbury, in Vol. I. of his Mathematical Collections.