15 



next summer, but was taken seriously ill during a visit to Scotland, 

 and returned home with difficulty. He died at Harpenden on Decem- 

 ber 23, 1901, in his 85th year.* R. W. 



The Investigations of Lawes and Gilbert. 



The Rothamsted Agricultural Station was the first of the many 

 Agricultural Research Stations now in existence ; the only earlier work 

 of the same kind was that carried out for some years by Boussingault 

 on his farm at Be-?helbronn, commencing in 1834. 



An extensive and long-continued series of field experiments upon 

 the principal agricultural crops is the most striking feature of the 

 Rothamsted work. The trials commenced with turnips and wheat, and 

 soon extended to many other crops, till nearly 40 acres were occupied by 

 these experiments. In each case the same crop was grown year after 

 year on the same land. Thus, at the death of Sir John Lawes, the 

 fifty-seventh successive crop of wheat had been harvested in Broadbalk 

 field. From the commencement of each field experiment one plot was 

 left entirely unmanured and one received farmyard manure each year. 

 The remaining plots received at first various manures, but in a few 

 years the earliest experimental fields were brought under a continuous 

 system of manuring, and the fields afterwards taken for crop experi- 

 ments received from the first a uniform treatment. The plan in each 

 case was to supply certain plots every year with the various ash con- 

 stituents of the crop called by Lawes and Gilbert " mineral manures " 

 while other plots received nitrogenous manure in various forms, and 

 others various mixtures of the mineral and nitrogenous manures used 

 separately on the other plots. The plan of manuring adopted in these 

 field experiments was originally intended as a practical test of the 

 " mineral theory " of Baron Liebig ; no better scheme could, however, 

 have been chosen for the elucidation of the general problems of the 

 relation of crop, soil, and manure to each other. Experimenting in 

 this way many important facts were brought to light the capacity of 

 the crop to supply itself with nitrogen from the natural sources of the 

 soil and atmosphere ; its capacity to supply itself with ash constituents 

 from the soil ; the particular ash constituents most necessary to be applied 

 as manure, and those of which the soil soonest became exhausted ; the 

 relative value of various nitrogenous manures, and the effect produced 

 by varying amounts of nitiogen. A comparison of the crops produced 

 by chemical manures with the crop yielded by ordinary farmyard 

 manure was also obtained every year. In some instances the special 

 application of manure was stopped on certain plots after a number of 



* For some further information upon Sir Henry Gilbert's life and work see 

 Nature, January 2. 1902, p. 205; Jo-it r. Roy Agrlc. Soc., 1901, p. 347 Trans 

 Chem. Soc., 1902, p. 625. 



