Sir John Lawes and Sir Joseph Gilbert. 243 



years, and the land left unmanured ; the effect of the residue of the 

 former manuring was thus made apparent. The produce of each plot was 

 carefully weighed, and at the laboratory the proportion of dry matter 

 and ash was determined, while in selected instances the percentage of 

 nitrogen was ascertained, and the plant ash was submitted to analysis. 

 The great variety of seasons met with in so long a series of field ex- 

 periments enabled the effect of season upon the weight and composition 

 of the crops to be studied, as well as the effect produced by manures. 



In later years samples of the soils and subsoils of the various 

 experimental plots were repeatedly taken and analysed ; the accumula- 

 tion or loss of nitrogen, carbon, phosphoric, acid and potash resulting 

 from the particular treatment of each plot was thus ascertained. In the 

 case of the wheat field each plot was provided with a drain-pipe, and 

 the water percolating through the soil was regularly collected and some 

 of its constituents determined by chemical analysis ; information was 

 thus gained as to the losses which manured land suffers by drainage. 



In order to make the chemical statistics of the experimental crops 

 more complete, the rain was collected in a large rain-gauge, and some 

 of its constituents determined. Three drain-gauges, consisting of three 

 masses of bare soil of various depth, were also constructed to ascertain 

 what proportion of the rainfall passed through the soil ; the drainage 

 waters from these bare and unmanured soils were also analysed for 

 comparison with the drainage waters furnished by the soils cropped and 

 manured in Broadbalk field. 



Besides the field experiments with individual crops, there was a 

 rotation field in which four systems of cropping were carried out, repre- 

 senting ordinary farm practice. A part of this field was permanently 

 unmanured, another portion received only the important ash con- 

 stituents of crops, and a third portion the ash constituents together 

 with nitrogenous manures. Here, too, both crops and soil have been 

 submitted to analysis in order to complete the chemical statistics of the 

 experiment. In other fields the simple rotations of wheat and beans, 

 and wheat and fallow have been studied. 



In the experiments with meadow land mown for hay, the same 

 conditions of manuring were adopted as with other crops. In this 

 case the continued application of different manures produced a great 

 alteration in the botanical character of the herbage, which became 

 extremely different on different plots. This result led to a systematic 

 botanical analysis of the hay produced by each experimental manure. 

 The aid of Dr. Maxwell Masters, F.R.S., was obtained in this part of 

 the inquiry, which has been continued for many years. 



The question whether plants assimilated the free nitrogen of the 

 atmosphere was a subject much debated in the early years of the 

 Kothamsted experiments. Dr. Evan Pugh came to England early in 1857, 



