DISCOVERY BY EXTENDING THE RESEARCHES OF OTHERS. 545 



the same in a large number of bodies. Out of a very large 

 number of instances which might be mentioned, I select 

 a very few. After the property of magnetism had been, 

 discovered in iron, and that of electric attraction in 

 amber which had been rubbed, Gilbert extended, by means 

 of experiments, the list of magnetic bodies, and of those 

 which became electric by friction. After Seebeck, of Ber- 

 lin, had, in the year 1822, discovered thermo-electricity, 

 Professor Gumming, of Cambridge, in the year 1823, 

 extended the number of thermo-electric substances, and 

 determined their order in a series. Haiiy similarly ex- 

 tended the list of pyro-electric bodies ; Faraday that of 

 liquefiable gases and of magnetic substances ; Stokes that 

 of fluorescent substances, &c. &c. It having been dis- 

 covered by De Luc, in the year 1755, that ice, during the 

 act of melting, did not rise in temperature, although heat 

 was being absorbed by it, other investigators subsequently 

 discovered that all solid substances which are capable of 

 melting, -remain stationary in temperature during the act 

 of fusion. 



Other discoveries are often made by extending the 

 researches of a previous investigator in a more or less new 

 direction. Galileo, having heard that Lippersley, a Dutch 

 maker of spectacles, had constructed and presented to 

 Count Maurice of Nassau an apparatus which caused 

 distant objects to appear near, repeated his experiment, 

 developed the telescope, and thus laid the foundation of 

 modern astronomy. Gerboin, in 1801, having discovered 

 the electrolytic movements of mercury, Sir John Herschel, 

 in 1823, by extending the research on that subject in 

 various directions, discovered a number of new truths ; and 

 the author, by a similar process, in the year 1862, was 

 led to discover the phenomenon of 6 electrolytic sounds.' 

 Fraunhofer, Fox Talbot, Brewster, Van der Willigen, 



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