Historical Relations 131 



uniform movements of heavenly bodies. Kepler was the real 

 founder of the modern astronomical system. The period from 1 600 

 onward lies with new men, Galileo and Kepler among astronomers 

 and physicists, Harvey among biologists, Descartes among philo- 

 sophers. The year 1600 thus represents as real a division as any 

 that we can expect in the history of thought. 



1 2. The Reign of Law 



The seventeenth century opened with an extraordinary wealth 

 of scientific discovery. As we glance at the mass of fundamental 

 work produced during that period, we perceive the major depart- 

 ments of science as we know them to-day becoming clearly 

 differentiated. The acceptance of observation and experiment as 

 the only method of eliciting the laws of nature reaches an ever- 

 widening circle. Even to enumerate the names of the seventeenth- 

 century scientific pioneers would be a formidable task. The 

 sciences penetrated to the universities and influenced the curri- 

 cula. The number of scientific men became so large and so 

 influential that separate organisations were formed by them in the 

 interests of their studies. It is the age of the foundations of the 

 Academies. 



In the realm of experimental physics, Galileo's invention of the 

 thermometer, with his discovery of the isochronism of the pendulum 

 and of the law of acceleration of falling bodies, had a little preceded 

 the publication of Gilbert's epoch-making work on the magnet. 

 Soon there followed the construction of the telescope and micro- 

 scope by Galileo, and the elucidation of the optical principles of 

 these instruments by Johannes Kepler. Biology, still apart from 

 the main development of scientific thought, had made great advances 

 before a third of the century was out. The first scientific attempts 

 at a classification of plants had been made by Cesalpino (1579-1603). 

 The Paduan school had launched human anatomy on to the final 

 stage of its development and had laid sound foundations to the study 

 of the comparative structure of animals. Nor had the advance in 

 experimental physics been without its influence on biological 

 development, for the first application of instrumental methods had 

 been made to bodily processes. Above all, a firm foundation had 

 been provided for the mechanical explanation of these processes by 

 the demonstration of the circulation of the blood by William 

 Harvey (i 578-1 657), a disciple of the Paduan school. Thereby 



