INTRODUCTION 7 



at Rothamsted, Eng. Dr. Gilbert had previously been 

 a pupil at L,iebig, and his becoming associated with 

 Sir J. B. La wes marks the establishment of the second 

 experiment station. Many of the Rothamsted experi- 

 ments have been continued since 1844, and results of 

 the greatest value io agriculture have been obtained. 

 The investigations on the non-assimilation of the at- 

 mospheric nitrogen by crops, published in 1861, were 

 accepted as conclusive evidence upon this much-vexed 

 question. The work on manures, nitrification, the 

 nitrogen supply of crops, and on the increase and de- 

 crease of the nitrogen of the soil when different crops 

 are produced, has had a most important bearing upon 

 maintaining the fertility of soils. 



u The general plan of the field experiments has been 

 to grow some of the most important crops of rotation, 

 each separately, for many years in succession on the 

 same land, without manure, with farmyard manure, 

 and with a great variety of chemical manures, the 

 same kind of manure being, as a rule, applied year after 

 year on the same plot. Experiments with different 

 manures on the mixed herbage of permanent grass 

 land, on the effects of fallow, and on the actual course 

 of rotation without manure, and with different manures 

 have likewise been made." 4 



In addition to Davy, Thaer, DeSaussure, Bous- 

 singault, Liebig, and Lawes and Gilbert, a great 

 many others have contributed to our knowledge of 

 the properties of soils. The work of Pasteur, while 

 it did not directly relate to soils, indirectly had great 

 influence upon soil investigations. His researches 

 upon fermentation made it possible for Schlosing to 



