JEROME CARDAN 211 



there an old friend in Ludovico Ferrari, who was at 

 this time lecturing on mathematics. He also received 

 into his house a new pupil, a Bolognese youth named 

 Rodolfo Sylvestro, who was destined hereafter to bring 

 as great credit to his teacher's name in Medicine as 

 Ferrari had already brought thereto in Mathematics. 

 Rodolfo proved to be one of the most faithful and 

 devoted of friends ; he remained at Bologna as long as 

 Cardan continued to live there, sharing his master's 

 ill-fortune, and ultimately accompanied him to Rome 

 in 1571. He gives the names of two other Bolognese 

 students, Giulio Pozzo and Camillo Zanolino, but of all 

 his surviving pupils he rates Sylvestro as the most gifted. 

 The records of Cardan's life at this period are scant 

 and fragmentary, few events being chronicled except 

 dreams and portents. In giving an account of one of 

 these manifestations, which happened in September 1563, 

 he incidentally lets light upon certain changes and 

 vicissitudes in his own affairs. He was at this time 

 living in an apartment in the house of the Ranucci, next 

 door to a half-ruined palace of the Ghislieri. One night 

 he awoke from sleep, and found that the neck-band of 

 his shirt had become entangled with the cord by which 

 he kept his precious emerald and a written charm sus- 

 pended round his neck. He tried to disentangle the 

 knot, but in vain, so he left the complication as it was, 

 purposing to unravel it by daylight. He did not fall 

 asleep ; but, after lying quiet for a little, he determined 

 to attempt once more whether he could undo the knot, 

 when he found that everything was clear, and the stone 

 under his armpit. " This sign showed me an unhoped- 

 for solution of certain weighty difficulties, and at the 

 same time proved, as I have often said elsewhere, that 

 there must have been present something else unperceived 



