120 SECTION PHYSICS. 



Renieri was employed on the composition of the tables, Galileo gave 

 himself up to meditations on his time-measurer, and I remember one 

 day in the year 1641, when I lived near him in the Villa d'Arcetri, 

 that the idea struck him that it would be possible to adapt the pen- 

 dulum to clocks with weights or springs, and avail himself of it 

 instead of the usual regulator, hoping that the perfectly equable and 

 natural motion of the pendulum would correct all the defects in 

 the mechanism of the clocks. But as his blindness deprived him 

 of the power of making designs and models which would answer 

 to the designs which he had formed in his brain, his son Vincenzo 

 having arrived one day at Arcctri from Florence, Galileo con- 

 fided his idea to him, and many times afterwards did they reason 

 over the matter, and at last they settled upon the method which 

 is shown in the accompanying drawing, and they set at once to work, 

 in order practically to overcome those difficulties which it is for the 

 most part impossible to foresee. But Signer Vincenzo intended to 

 construct the instrument with his own hand, in order that by this 

 means the secret of the invention should not be reported by tlio 

 artificers, before it had been presented to his Serene Highness the 

 Grand Duke, his master, and the States-General (to be used for ob- 

 serving the longitude), but he put off the execution of his work so fre- 

 quently, that a few months later, Galileo, the author of all these 

 admirable inventions, fell sick, and on the 8th of January, 1641, ' ab 

 Incarnazione,' according to the Roman style, he died. And conse- 

 quently Signer Vincenzo's energies so cooled down that it was not 

 until the month of April, 1649, that he actually began to make the 

 present clock upon the idea explained to him by his father, Galileo. 

 He then managed to obtain the services of a young man who is 

 yet living named Domenico Balestri, a locksmith who had had 

 some experience in making large wail clocks, and he made him 

 construct the iron frame, the wheels with their axes and pinions, 

 without cutting (intagliare) ^ and the remainder he made with his own 

 hand, constructing on the highest wheel, called the wheel of notches 

 (tacche), No. 12 teeth, with as many cogs, divided between each 

 tooth, and with the pinion in the axis of No. 6 ; and another wheel 

 which moves the above-mentioned of No. 90. He then fixed on one 

 side of the support which is at right angles to the frame, the key 



