24 Mac Leod, The Place of Science in History. 



and oxygen. In 1807 Davy discovered the electrolysis 

 of potash and soda, and thus isolated the metals potassium 

 and sodium. In 1808 Davy produced the electric arc 

 between two poles of carbon. In 1820 Christian 

 Oersted, professor at the University of Copenhagen, dis- 

 covered the deviation of the magnetic needle under the 

 influence of an electric current. In the same year ARAGO 

 and Davy discovered, independently of one another, the 

 power which an electric current possesses of magnetising 

 iron and steel. In 1824 W. SURGEON, by wrapping a 

 metallic wire round an iron core, discovered that the iron 

 is magnetised as long as the wire is carrying an electric 

 current, and ceases to be magnetised when the current is 

 broken. 



The above mere enumeration, which is far from being 

 complete, fills us with admiration and astonishment. 

 Here we see at work once more the all powerful idea, the 

 impulse of progress, the true maker of history. The 

 achievements which we have mentioned are not only 

 discoveries of new truths ; we know to-day what creative 

 force these truths carried in them. We know the rich 

 harvest of practical applications to which they have given 

 birth. We need only recall to mind the electric telegraph, 

 electroplating, the application of electricity to chemistry, 

 electric locomotion, the telephone, electric heating, and 

 many more. 



All these innovations have their starting point in the 

 discovery of Volta. Superficial minds are sometimes 

 tempted to* believe that these discoveries were made at 

 one blow, the result of one happy inspiration. History 

 teaches us that, on the contrary, each of them is the fruit 

 of long studies, and has passed through a long evolution. 

 Let us pause a moment in the consideration of one of 

 these inventions, the electric telegraph. 



