622 HISTORY OF SCIENCE. 



hand of a master. It admirably answers the conditions of exposing 

 of a large surface of liquid to the gas, of agitating of the whole as each 

 bubble of gas passes, and of guarding against loss of the liquid from the 

 agitation caused by the passage of gas in either direction. Liebig's 

 combustion apparatus for determining the quantities of carbon and 

 hydrogen in organic substances is also distinguished by great sim- 

 plicity in its construction and management, and to the facilities it 

 has afforded, organic chemistry is to this day indebted for the vast 

 development which a few decades have sufficed to bring about. In 

 addition to the creation of organic analysis, chemists have also to 

 thank Liebig for the invention of the general plan of the regular 

 analysis of mineral substances which is followed in our laboratories. 

 Liebig's literary labours were not confined to his purely scientific papers, 

 numerous as these are. He (with his friends Wohler and Kopp as 

 coadjutors in the later years) regularly issued a record of the progress 

 of chemical discovery. Of this publication, called " Liebig's Annals 

 of Chemistry," one hundred and sixty-five volumes appeared be- 

 tween 1832 and 1873, the time of Liebig's death. He was joint 

 author of a large Dictionary of Chemistry and of the " Handbook of 

 Organic Chemistry," in which that science for the first time exhibited 

 an orderly and comprehensive outline. Then there are his several 

 very important works on agricultural and physiological chemistry : 

 the " Familiar Letters on Chemistry," of which several editions have 

 appeared in England, may probably be known to the reader. These 

 letters were originally published in a German newspaper, and were 

 intended to impart to general readers from time to time such results 

 of Liebig's inquiries or meditations on experimental science, agriculture, 

 physiology, or general topics, as might be available. 



Liebig's character was specially distinguished by his eagerness for 

 truth before all things ; for this he would without reluctance abandon 

 cherished theories, and cordially acknowledge his mistakes when con- 

 vinced that his former views were untenable. He esteemed the actual 

 results of experiments more highly than the most plausible speculation, 

 and although his own speculations were often most happy, he would 

 rely conclusively upon no other foundation than experiment. His 

 distinguished pupil and friend, Professor Hofmann of Berlin, says of 

 him, " During his long contest with Gerhardt, Liebig never loses the 

 sure foundation of experiment. He has not to retract a single state- 

 ment as to facts, though he does not deny having committed mistakes 

 in interpretation ; but these he happily compares to the broken crock- 

 ery found in the corners of the best-regulated houses in which a good 

 deal of work has been going on." In kindliness of character and in 

 simplicity of life Liebig appears to have resembled his great English 

 contemporary, Faraday. 



Faraday, whose career and whose discoveries in another department 

 of science have been presented in a previous chapter, began as a 



