The Scientific AgricultiLre of the Period. 289 



vegetable life ; ^ and tliougli he rightly concurred with Virgil 

 in associating with lees of oil the qualities of a manure,- he 

 could give no better explanation for this phenomenon than the 

 Latin poet. On a par with such defective sapience were the 

 wonderful results of cereal growth obtained by a learned 

 society in Paris by experimenting with the essence of the 

 heliotrope or sunflower. 



Amidst all this obscurity there were occasional gleams of 

 coming light. Homberg had proved the salutary effects of 

 potassium and nitrogen on plants by his experiments with 

 cresses grown in a weak solution of saltpetre. Sir Kenelm 

 Digby had enunciated a truth when he gave the preference 

 to the manurial effects of rain-water over those of common 

 water.^ Yet it was impossible for him to have realised the 

 true virtues of the nitrites and nitrates which the dew and 

 cloud contain. Indeed, before the discovery of oxygen, 

 analysis and synthesis were deceptive and unreliable pro- 

 cesses. All the niceties of the modern chemical nomenclature 

 resulted from the discovery of this gas ; and the subtle 

 distinctions between the terminations "ous" and " ic," " ite," 

 " ide," and " ate," helped to codify the various chemical com- 

 pounds in a manner intelligible to the ordinary human 

 understanding. 



Such being the scanty outcome of all the scientific learning 

 of the time, can we hope to find better results when we turn 

 for information to the empirical wisdom of the eighteenth- 

 century husbandman ? 



Typical of this class was Jethro Tull, whose wide mind was 

 capable of realising how much scientific experiment could 

 assist that industry in which he was specially interested. He 

 had therefore put to the drastic test of practice the various 

 theories of Richard Bradley, and thus convinced himself of 

 their futility.*^ As far as actual examination could teach him, 



* " Docuimus etiam Arbores vina potare."— Plin., Hist. Xaf., lib. 12, 

 cap. 1. 



^ Virg., Georg., lib. 1. 



^ "Sir Kenelme Digby presented every one of ixs his Discourse of the 



Vegetation of Plants," writes Evelyn in his Diary, Aug. 9th, 1661. 



* Horse-hoeing Husbandry, etc. Jethro Tull. 



II. U 



