146 A Short History of Astronomy [CH. vi. 



evidence, but on the authority of the great writers of the 

 past. This valuable characteristic, which marked him 

 throughout his life, coupled with his skill in argument, 

 earned for him the dislike of some of his professors, and 

 from his fellow-students the nickname of The Wrangler. 



114. In 1582 his keen observation led to his first scien- 

 tific discovery. Happening one day in the Cathedral of 

 Pisa to be looking at the swinging of a lamp which was 

 hanging from the roof, he noticed that as the motion 

 gradually died away and the extent of each oscillation 

 became less, the time occupied by each oscillation remained 

 sensibly the same, a result which he verified more precisely 

 by comparison with the beating of his pulse. Further 

 thought and trial shewed him that this property was not 

 peculiar to cathedral lamps, but that any weight hung by 

 a string (or any other form of pendulum) swung to and fro 

 in a time which depended only on the length of the string 

 and other characteristics of the pendulum itself, and not 

 to any appreciable extent on the way in which it was set 

 in motion or on the extent of each oscillation. He devised 

 accordingly an instrument the oscillations of which could 

 be used while they lasted as a measure of time, and which 

 was in practice found very useful by doctors for measuring 

 the rate of a patient's pulse. 



115. Before very long it became evident that Galilei had 

 no special taste for medicine, a study selected for him 

 chiefly as leading to a reasonably lucrative professional 

 career, and that his real bent was for mathematics and its 

 applications to experimental science. He had received 

 little or no formal teaching in mathematics before his second 

 year at the University, in the course of which he happened 

 to overhear a lesson on Euclid's geometry, given at the 

 Grand Duke's court, and was so fascinated that he con- 

 tinued to attend the course, at first surreptitiously, afterwards 

 openly ; his interest in the subject was thereby so much 

 stimulated, and his aptitude for it was so marked, that he 

 obtained his father's consent to abandon medicine in favour 

 of mathematics. 



In 1585, however, poverty compelled him to quit the 

 University without completing the regular course and 

 obtaining a degree, and the next four years were spent 



