DISCOVERIES IN THE CELESTIAL SPACES. 323 



of the insuperable difficulties presented to its practical appli- 

 cation on the unstable element. He wished to go himself, or 

 to send his son Vicenzio, to Spain, with a hundred telescopes, 

 which he would prepare. He required as a recompense " una 

 croce di San Jago," and an annual payment of 4000 scudi, a 

 small sum, he says, considering that hopes had been given to 

 him, in the house of Cardinal Borgia, of receiving 6000 ducats 

 annually. 



The discovery of the secondary planets of Jupiter was soon 

 followed by the observations of the so-called triple form of 

 Saturn as a planeta tergeminus. As early as November, 

 1610, Galileo informed Kepler that " Saturn consisted of three 

 stars, which were in mutual contact with one another." In 

 this observation lay the germ of the discovery of Saturn's ring. 

 Hevelius, in 1656, described the variations in its form, the un- 

 equal opening of the handles (ansae), and their occasional total 

 disappearance. The merit of having given a scientific expla- 

 nation of all the phenomena of Saturn's ring belongs, how- 

 ever, to the acute observer Huygens, who, in 1 655, in accord- 

 ance with the suspicious custom of the age, and like Galileo, 

 concealed his discovery in an anagram of eighty-eight letters. 

 Dominicus Cassini was the first who observed the black stripe 

 on the ring, and in 1684 he recognized that it is divided into 

 at least two concentric rings. I have here collected together 

 what has been learned during a century regarding the most 

 wonderful and least anticipated of all the forms occurring in 

 the heavenly regions a form which has led to ingenious con- 

 jectures regarding the original mode of formation of the sec- 

 ondary and primary planets. 



embassador in 1636, but without leading to the desired object. The 

 telescopes were to magnify from forty to fifty times. In order more 

 easily to find the satellites when the ship is in motion, and (as he be- 

 lieved) to keep them in the field, he invented, in 1617 (Nelli, vol. ii., 

 p. 663), the binocular telescope, which has generally been ascribed tc 

 the Capuciue monk Schyrleus de Rheita, who had much experience ic 

 optical matters, and who endeavored to construct telescopes magnifying 

 four thousand times. Galileo made experiments with his binocular 

 (which he also called a celatone or testiera) in the harbor of Leghorn, 

 while the ship was violently moved by a strong wind. He also caused 

 a contrivance to be prepared in the arsenal at Pisa, by B which the ob- 

 server of the satellites might be protected from all motion, by seating 

 himself in a kind of boat, floating in another boat filled with water or 

 with oil (Lettera al Picchena de' 22 Marzo, 1617 ; Nelli, Vita, vol. i., p. 

 281 ; Galilei, Opere, t. ii., p. 473 ; Lettera a Lorenzo Realio del 5 Giug~ 

 no, 1637). The proof which Galileo (Opere, t. ii., p. 454) brought 6h> 

 ward of the advantage to the naval service of his method over Moriu'i 

 method of lunar distances is very striking. 



