LESSONS IN PHTSrCS. 18 



department of science, however limited, will be of greater educa- 

 tional value to the individual and will make him more helpful to 

 his fellows, than less careful work over a wider range of the sub- 

 ject. And so intimate are the relations of } the different parts of 

 the scientific field, that a thorough knowledge of one portion gives 

 one a better view of the whole than does the mere superficial 

 knowledge of even several branches. 



Time is an important element in scientific investigations. It 

 takes time, often a long time, to gather sufficient facts, time to 

 arrange these facts according to their relations, time to draw 

 conclusions and form judgments. Many would-be scientific men 

 fail because they are over-anxious to reach conclusions. It was 

 a long time from Galvani's observations of the muscles of a frog 

 to the laying of the Atlantic cable, and yet they were related as 

 cause and effect. While time is necessary to reach scientific con- 

 clusions, some of the best scientific work the world has known 

 was done at odd moments, between the hours of regular employ- 

 ment. 



The term law, as used in scientific discussions, means simply a 

 statement of the observed order, sequence or relation observed 

 among natural phenomena. The law of gravitation merely ex- 

 plains to us how every particle of matter in the universe is, or 

 appears to be, altering its motion with reference to every other 

 particle. It does not tell why the particles move as they do; it 

 does not tell why the moon moves in a certain curve about the 

 earth. It simply gives in a few brief words the relationships 

 observed between a vast range of phenomena. This is the nature 

 of all scientific law. Men gather facts, classify them, analyze 

 them, discover their relationships, and then describe in simple 

 terms the widest possible range of phenomena. A scientific law is 

 always liable to be replaced or reformed as knowledge increases. 

 Newton's law of gravitation has stood the test of human expe- 

 rience for over 200 years without necessity of change. 



An hypothesis or theory is the supposition assumed to account 

 for that which is only partially known. Such suppositions have 

 been baaed on a larger or smaller knowledge of facts. They may 



