S/J^ HUMPHREY DA VY. 63 



his laboratory, and those of the child among his play-things. 

 Of course, however, every hypothesis must give way before an 

 experiment the result of which cannot be reconciled with it. 

 Newton, in proceeding to investigate the system of the heavens, 

 set out on the hypothesis that the same power of gravitation 

 which made a stone fall to the ground would be found to retain 

 the moon and the planets in their orbits around the earth and 

 the sun. The result of his first calculation was unfavourable to 

 this supposition, and he at once abandoned it. We have here 

 an example both of the use of an hypothesis, and of the proper 

 limits of reliance on it. The grand discovery which eventually 

 resulted from Newton's investigations affords us, again, an 

 illustration of the manner in which an hypothesis serves to lead 

 to, and originate a theory. 



The metal which Sir Humphrey Davy obtained from potash 

 he called Potassiufti ; and from soda he also, by a similar pro- 

 cess, obtained another, which he called Sodium. Both these 

 new metals he found to possess several curious properties, 

 which, however, we cannot here stop to enumerate. He after- 

 wards decomposed also the different earths, and showed them 

 to be all, as well as the alkalis, compounds of oxygen with a 

 metallic base. But these important discoveries, which may be 

 said to have revolutionised the science of chemistry, were not 

 the only results which he obtained from his galvanic and 

 electrical experiments. The interesting subject of the connec- 

 tion between electricity and magnetism received considerable 

 elucidation from his researches. For an account of his con- 

 tributions to this branch of science, we must refer to the able 

 memoir we have already mentioned, or to his papers on the 

 magnetic phenomena produced by electricity, in the Philoso- 

 phical Transactions. 



