8 Difference between Discovery and Invention. 



applied knowledge. An invention is usually a com- 

 bination and application to some desired purpose, of 

 scientific truths which have been previously dis- 

 covered. When Oersted first observed a magnetic 

 needle move by means of a current of electricity, 

 he made a scientific discovery ; but when Wheat- 

 stone and Cooke applied Oersted's discovery in their 

 telegraph from Paddington to Slough, they made 

 an invention. The success of the electro-plating 

 process was dependent upon knowledge previously 

 discovered. Mr. Wright, a surgeon in Birmingham, 

 was led to the invention of the use of cyanide of 

 potassium in electro-plating and gilding, by reading 

 in Scheele's "Chemical Essay" (p.p. 405 and 406), 

 that "if after these calces" (i.e. t the cyanides of gold 

 and silver) "have been precipitated, a sufficient 

 quantity of precipitating liquor be added, in order 

 to redissolve them, the solution remains clear in the 

 open air, and in this state the serial acid " (i.e., 

 carbonic acid of the air) "-does not reprecipitate the 

 metallic calx." 



Immediately a discovery is effected it is made 

 public, and is afterwards incorporated in the 

 ordinary text books of science, ready for the use of 

 inventors ; and in this way such books have become 

 filled with valuable knowledge acquired by researches 

 in past times. All this knowledge (which has cost 

 millions of pounds and a vast amount of intellect 

 and labour) has been given by its discoverers freely 

 to the nation. Some idea of the number of scientific 



