4 How discoveries are made. 



of silver and mercury, and converted the latter metal 

 into a red oxide like cinnabar, and he remarked, " a 

 spirit is united with the metal, and what proves it 

 is this, that this artificial cinnabar submitted to 

 distillation, disengages that spirit." The " spirit" 

 was evidently oxygen. 



Some discoveries are made by observing the phe- 

 nomena of bodies placed under special conditions by 

 those operations of nature over which we have little 

 or no control. All our knowledge of Astronomy, 

 and much of that of geology and physiology, was 

 acquired in this way. 



Nearly all modern discoveries of importance in 

 physics or chemistry require long and difficult inves- 

 tigations to be made in order to completely establish 

 their truth. When Crookes discovered Thallium, 

 he saw the first sign of its existence in a momentary 

 flash of green light in a spectroscope, but he had to 

 expend upon the subject several years of most diffi- 

 cult labour, and a considerable sum of money, in 

 order to prove the correctness of his suspicion that 

 he had discovered a new metal. M. Lecocq de 

 Boisbaudran discovered the metal Gallium and 

 Bunsen discovered Rubidium and Caesium in a 

 similar manner. 



Discoveries in science, are usually made, not by 

 trying to obtain some valuable commercial or tech- 

 nical result, but by making new, reliable, and 

 systematic investigations. By investigating the 

 chemical action of electricity upon saline bodies. 



