112 ESSAYS BIOGRAPHICAL AND CHEMICAL 



agricultural chemistry. From his laboratory at Meudon, 

 assisted by his colleague, Andre, have appeared a succes- 

 sion of memoirs, chiefly relating to the absorption of 

 nitrogen by plants, and to their behaviour under the 

 influence of electric energy. To the very end his interest 

 was kept up in these experiments ; and he was hopeful of 

 increasing by electrical means the productiveness of 

 cereals, and of adding to the world's food-supply. 



Though so keenly alive to the present, the past had for 

 Berthelot a great attraction. In 1877 he analysed a 

 sample of Roman wine, which had been preserved in a 

 sealed flask ; and he has contributed to the Journals many 

 notices of the composition of ancient objects of metal. 

 His works on Les Origines de VAlchimie, and on a Collec- 

 tion des anciens Alchimistes grecs, texte et traduction, and 

 his Introduction d I' etude de la Chimie des Anciens et du 

 moyen dge,' involved long research of ancient manuscripts ; 

 he acquired facility in reading ancient Greek, though for 

 Arabian sources he was dependent on others. 



Berthelot was the author of numerous works besides 

 those on Alchemy. In 1872 he published a Treatise on 

 Organic Chemistry; a fourth edition appeared in 1899. 

 This was followed by La Synthese chimique ; Essai de 

 Chimie mechanique (1879), in which he announced the 

 principle of ' maximum work,' a doctrine afterwards with- 

 drawn, or, at least, greatly modified in 1894; Traite 

 2^ratique de Calorimetrie chimique (1893); Thermochimie : 

 Donnees et lois numeriques (1898), in which an account 

 of his long series of calorimetrical measurements is 

 given ; this work and that of Julius Thomsen on Ther- 

 .mochimie are the standard books on the subject, and 

 each contains the results of the individual researches of 

 its author. 



Berthelot's mind was one which interested itself greatly, 

 not merely with things, but with their origins; and in 



