48 ESSAYS BIOGRAPHICAL AND CHEMICAL 



thoughts too nearly analogous to enlighten and vivify.' 

 Still many of our scientific workers of to-day would be 

 glad if they could extract as much leisure time from 

 amidst their daily employments. Davy generally entered 

 the laboratory about ten or eleven o'clock, and if uninter- 

 rupted, remained there till about three or four. His 

 evenings were almost invariably spent in dining out, and at 

 evening parties afterwards. ' To the frequenters of these 

 parties he must have appeared a votary of fashion, rather 

 than of science,' as his brother remarked. 



Yet, during the years which followed, he accomplished 

 an immense amount of very remarkable work. Besides 

 investigating, by the request of the managers of the Royal 

 Institution, the chemistry of tanning, an investigation 

 which led to the use of catechu as a substitute for the 

 old-fashioned oak-bark, he lectured, by the request of the 

 Board of Agriculture, on ' The Connection of Chemistry 

 with Vegetable Physiology.' These lectures were given 

 every year, and in them were incorporated the results of a 

 considerable number of experiments made by him, or 

 under his direction, on the chemistry of plants. In 1813, 

 when he ceased to lecture on the subject, he published his 

 lectures, under the title The Elements of Agricultural 

 Chemistry. For the copyright of this work he received 

 one thousand guineas, and fifty guineas for each subse- 

 quent edition. Truly he was a fortunate man ! 



Between January 1801 and April 1812 he accomplished 

 two of his most remarkable pieces of work ; first, on the 

 decomposition of the alkalies ; and second, on the nature 

 of chlorine. As his name rives chiefly in connection with 

 these two investigations, and in his research on the 

 nature of flame, which culminated in the invention of the 

 safety-lamp, I shall give some account of them in 

 minuter detail. 



The Swedish chemist, Scheele, had discovered in 1774, 



