30 HOW CROPS FEED. 



Inaccuracy of Ville's Results. — In comparing the in- 

 vestigations of Boussingault an<l Yille as detailed in their 

 own words, the critical reader cannot fail to be struck 

 with the greater simplicity of the apparatus used by the 

 former, and his more exhaustive study of the possible 

 sources of error incidental to the investigation — facts which 

 are greatly in favor of the conclusions of this skillful and 

 experienced philosoi^her. Furthermore Cloez, who was 

 employed by a Commission of the French Academy to 

 oversee the repetition of Ville's experiments, found that a 

 considerable quantity of ammonia was either generated 

 within or introduced into the apparatus of Ville during 

 the period of the trials, which of course vitiated all his 

 results. 



Any further doubts with regard to this important sub- 

 ject have been effectually disposed of by another most 

 elaborate investigation. 



Research of Lawes, Gilbert, and Pugh.— In 1857 and 

 '58, the late Dr. Pugh, afterward President of the Penn- 

 sylvania Agricultural College, associated himself with 

 Messrs. Lawes and Gilbert, of Rothamstead, England, 

 for the purpose of investigating all those points con- 

 nected with the subject, which the spirited discussion of 

 the researches of Boussingault and Ville had suggested as 

 possibly accounting for the diversity of their results. 

 Lawes, Gilbert, and Pugh, conducted 27 experiments on 

 graminaceous and leguminous plants, and on buckwheat. 

 The plants vegetated witliin large glass bells. They were 

 cut off from the external air by the bells dipping into 

 mercury. They were supplied with renewed portions of 

 purified air mixed Avith carbonic acid, which, being forced 

 into the bells instead of being drawn through them, e^ 

 fectually prevented any ordinary air from getting access 

 to the plants. 



To li'iw. ail idea of the mode in which these delicate investigations are 

 c(*nducted, we give here a figure and concise description of the ajipara- 



