ON SCIENTIFIC METHOD 3 



Somerset and north of France, the most likely locality being 

 the neighbourhood of Dover". 



3. Verification of the generalization. A shaft is sunk at 

 Dover and a buried coal-field is actually discovered. 



Among other striking examples of the scientific method may 

 be mentioned the discovery of the Laws of Gravitation by 

 Newton, and the discovery of the planet Neptune by Galle in 

 the position where Adams and Leverrier independently pro- 

 phesied a new planet would be found. It may be stated 

 generally that when a theory or generalization enables us 

 correctly to prophesy future events, that theory may be re- 

 garded as embodying one or more Laws of Nature. Thus, 

 from calculations based on the theory of gravity, the position 

 of the heavenly bodies at a given time can be predicted. 

 Such calculations are to be found in the Nautical Almanac, 

 published every three years, and these have always been found 

 correct. Hence the Laws of Gravitation are regarded as Laws 

 of Nature. 



The scientific method is essentially experimental, and thus 

 requires further illustration. Much can be done by observation 

 only, but the progress of science would be exceedingly slow 

 if it were not for experiment, i.e. the observation of facts under 

 controlled conditions, enabling us to determine points which the 

 mere watching of nature might never allow us to elucidate. 

 Very good instances are found in the history of the "germ 

 theory ", which explains infectious diseases as only the action 

 of microscopic organisms found within the body. Cattle, for 

 example, are liable to be attacked by a most virulent com- 

 plaint of the sort known as anthrax or splenic fever. It was 

 noticed that the blood of animals which had died from 

 this disease always swarmed with rod-shaped microscopic or- 

 ganisms, members of the large group of bacteria (microbes), 

 the lowest subdivision of the vegetable kingdom. Mainly on 

 the strength of this fact was founded the generalization — 

 " Anthrax is due to rod-like bacteria in the blood ". Then 

 followed experiments designed to test the truth of this propo- 

 sition. It was found that if healthy animals were inoculated 

 with infected blood they quickly developed all the symptoms of 

 anthrax, and died in the same manner and after the same time 

 as in naturally occurring cases of the disease. A certain support 



