THE MIDDLE AGES AND DURING THE REVIVAL. 59 



the great science of the moderns after his experiments on 

 the fall of bodies, and the PENDULUM. " The pendulum," says 

 one of our best authorities on scientific researches,* " is the 

 most perfect (certainly one of the most perfect) of all instru- 

 ments, chiefly because it admits of almost endless repetitions. 

 Since the force of gravity never ceases, one swing of the 

 pendulum is no sooner ended than the other is begun, so that 

 the juxtaposition of successive units is absolutely perfect. 

 Provided that the oscillations be equal, 1,000 oscillations 

 will occupy 1,000 times as great an interval of time as one 

 oscillation. The excessive value of this instrument arises 

 from two circumstances : (i) the method of repetition which 

 is invaluable in science is eminently applicable to it ; (2) 

 unlike other instruments, it connects together three different 

 quantities, those of space, time, and force. (A) A pen- 

 dulum of invariable length, suspended at the same place 

 where the force of gravity may be considered constant, 

 furnishes a measure of time, (B) The same pendulum, 

 made to vibrate at different parts of the earth's surface, 

 and the times of vibration being astronomically determined, 

 the force of gravity becomes accurately known, (c) With 

 a known force of gravity, and time of vibration ascertained, 

 by reference to the stars, the length is determinate." We 

 have quoted this passage in full a liberty the author will be 

 the first to forgive us for knowledge' sake because of the 

 important part the pendulum has played in the science of the 

 last three centuries. We leave Galileo for the present, as we 

 shall again have occasion to speak of him and his scientific 

 discoveries. 



1566 1624. Antonio de Dominis explained the true 

 theory of the RAINBOW, in 1591, which Harriot still more 

 perfectly elucidated about the same time or shortly after. 



1566 1627. Ghetaldi published the earliest determina- 

 tions of SPECIFIC GRAVITIES of metals "in 1603 a subject 

 which Archimedes and the two great Arabian physicists Abur 

 Raihan and Alhazen had partly treated. 



15 d. 1600. Cavaliere created the ORATORIO, which, 

 with the Opera, constitutes dramatic music. 



* Jevons. 



