4 6 WOODWARD 



acknowledged master to a system of the world which dominated 

 scientific thought for nearly fifteen hundred years-. 



The period during which the observ^ations and researches of 

 Ptolemy were carried on is commonly referred to in history as 

 extending from the reign of the emperor Hadrian to that of 

 Marcus Aurelius. Thus, while Ptolemy was an Egyptian by 

 birth, the fact that he was permitted to pursue his astronomical 

 studies under the empire helps to some extent to relieve the 

 Romans of the charge that they were, as regards science, the most 

 ignorant people of antiquity. But the gravity of that charge is 

 only palliated by the work of Ptolemy, for he left no successors. 

 Roman astronomy did not rise above the level of astrology; the 

 spirit of scientific enquiry gave way to speculation and declama- 

 tion ; and the long night which followed was not broken until 

 the dawn of the epoch of Galileo — the modern epoch, whose 

 advances have been founded on observation an experiment. 



If astronomy is preeminent among the sciences for its depen- 

 dence on observation, chemistry and physics are equally preem- 

 inent for their dependence on experiment. This difference in 

 methods of investigation between the former and the two latter 

 sciences is a difference imposed by the circumstances that astron- 

 omy deals chiefly with objects at long range while chemistry 

 and physics are concerned with objects near at hand. It seems 

 not a little singular, however, at first thought, that progress in 

 the development of knowledge concerning the behavior of dis- 

 tant bodies should have been almost as rapid up to the present 

 time as the development of knowledge concerning bodies much 

 more familiar and accessible to us. 



Chemistry and physics, like astronomy, had their forerunners 

 in mythological follies and extravagances. Semi-civilized and 

 civilized man required a long time after he had learned how 

 to talk and to write well, after he had founded states and con- 

 structed systems of philosophy and religion, before he could 

 reason rationally and successfully with respect to the common- 

 est material things about him. Thus, chemistry was long ob- 

 scured by merely verbal speculations on the *' four elements, 

 earth, air, fire and water " or on the " three elements, salt, sul- 



