DISCOVERY BY MEANS OF HYPOTHESES. 509 



The hypotheses and questions chiefly referred to at the 

 head of this chapter are those which form the starting- 

 point of a research, and to settle which a research is 

 made ; but we must remember that during the progress of 

 every single investigation many hypotheses and questions 

 are usually raised, and many discoveries are made whilst 

 testing them, all of which are subsidiary to the settlement 

 of the main idea which originated the inquiry. 



There are many hypotheses and questions which, from 

 their very nature, are of great importance ; and if the 

 experiments made to test them yield an answer, either for 

 or against, the results must also be of great value ; but 

 in such cases this method of discovery is often very un- 

 certain. Harvey was nineteen years verifying by experiment 

 and observation his theory of the circulation of the blood. 

 Newton was many years trying to verify his hypothesis 

 of the law of action of gravity before he succeeded ; 

 Oersted's experience was similar with his conception of 

 electro-magnetism ; and Faraday's not unlike, with his idea 

 of the relation of magnetism to light. Faraday also suc- 

 cessfully sought to determine his hypothesis of the iden- 

 tity of frictional, voltaic, and animal electricity, in order 

 to obtain ' the decision of a doubtful point which interfered 

 with the extension of his views, and destroyed the strict- 

 ness of reasoning ; ' but even after many years of trial he 

 did not succeed in verifying his hypothesis of the relation 

 of gravity to the physical forces. Many hypotheses in 

 science have, however, been successfully verified. 



In order to test the hypothesis of an exploded planet, 

 * the Grerman astronomers agreed to examine the whole of 

 the zone in which Ceres and Pallas move, in the hope of 

 finding other planets fragments, as Olbers conceived they 

 might possibly be of an original mass. In the course of 

 this search Mr. Harding, of Lilienthal, on September 1, 



