jog NINETEENTH CENTURY. PT. ill. 



our atmosphere, and with a cold of 170 C, obtained a jet 

 of liquid hydrogen, which became partly solid and struck on 

 the floor with * the shrill noise of metallic hail,' thus con- 

 firming the idea first suggested by Faraday, that hydrogen 

 is a metal. These experiments have removed the last 

 barrier between gases and vapours, and we now know that 

 all substances only require suitable conditions to take either 

 of the three forms of solid, liquid, or gas. Thus M. Cail- 

 letet and M. Pictet have abolished the belief in ' permanent 

 gases.' 



Liebig the Great Teacher in the Chemistry of Or- 

 ganic Compounds. And now, before closing the history 

 of chemistry, we must mention, in passing, one great division 

 of the science of which we cannot attempt to give any real 

 account namely, the science of organic chemistry, or more 

 properly the chemistry of organic compounds. This study 

 began, as you will remember, when Boerhaave first examined 

 the juices of plants and the fluids in animal bodies. But it 

 can scarcely be said to have made any great advance till 

 the year 1828, when a German chemist named Wohler first 

 showed that urea, a substance in the bodies of animals, can 

 be made artificially. Since then Berthelot and other eminent 

 chemists who have followed him have discovered how to 

 make many compounds in the laboratory which were before 

 only found in living beings. 



But the great master of organic chemistry whose name 

 you must remember, though we can speak but little about 

 him, was Baron Liebig, of Darmstadt, who was born in 

 1803 and died in 1873. From the days when he was a 

 schoolboy, Liebig had made up his mind to be a chemist, 

 and through the kindness of Humboldt he was fortunate 

 enough to be introduced to Gay-Lussac, and to work with 

 him for some years. In 1824 he was made Professor of 



