EARLY EXPERIMENTS OF LAWES 5 



this was the period of the first introduction of what we now 

 call artificial manures; the virtue of bones had long been 

 known, and at Liebig's instigation their phosphoric acid was 

 being made soluble by acid, and dissolved bones were becoming 

 an article of commerce. Lawes had followed up Henslow's 

 discovery of coprolites by converting them into mineral super- 

 phosphate, and setting up the earliest manufactory of artificial 

 manures. The first importations of Peruvian guano had been 

 made, and nitrate of soda was also beginning to find its way 

 into the country. 



With these and many other substances Lawes had been 

 experimenting on a small scale, and the results of his trials 

 and all his farming experience went to show that a supply 

 of combined nitrogen in some form or other was not only 

 necessary to the crop, but on the whole determined its 

 yield to a far greater extent than the supply of ash 

 constituents. Yet Liebig's argument in the second (1843) 

 edition of his report all inclined to represent the mineral 

 manures as fundamental, and a supply of combined 

 nitrogen as unnecessary, or at least of secondary import- 

 ance. This question of the value or otherwise of nitrogenous 

 manures supplied the main guiding principle in the design of 

 all the earlier field experiments at Rothamsted, as will be 

 evident when the individual fields come to be considered, and 

 the controversy which arose with Liebig on the publication of 

 the first reports from Rothamsted endured for more than a 

 generation. Indeed the source and fate of the nitrogen of 

 vegetation remained in one form or another the dominant 

 interest in the Rothamsted Experiments up to the death of 

 Lawes and Gilbert. 



The evidence from the field experiments that farm crops 

 require a supply of combined nitrogen will be considered else- 

 where, as also the results of the determinations made of the 

 amounts of ammonia and other nitrogenous compounds 

 brought down by the rain ; in neither case was there evidence 

 that a normal vegetation could supply itself with the necessary 



