of Science to Agriculture. I4f 



points of theory recently introduced^ and pregnant with some most 

 important applications to practice. 



Upon turning to the Table of Agricultural Constants you will 

 perceive, that whilst an average crop of turnips, if estimated at 

 25 tons, contains 24 lbs. of phosphoric acid, one of wheat, con- 

 sisting of 1800 lbs., will contain only 7 lbs. 3 ozs. of that ingre- 

 dient ; and yet that, on examining the per centage of nitrogen, its 

 proportion in either case will appear to approach nearly to an 

 equality : that present in the crop of wheat being about 4J lbs. ; 

 and in the crop of turnips, 5Jlbs. 



Now the interesting researches of Professor Liebig, with which 

 I presume the agricultural world is by this time familiar, and 

 upon which, moreover, I am unwilling here to dwell, as they 

 have already formed the subject of one of my former lectures, 

 reprinted in a late Number of this Society's Journal — these re- 

 searches, I say, seem to have rendered it probable that nitrogen 

 cannot be secreted by plants directly from the atmosphere. 



I am aware, indeed, that the French chemist, Boussingault, was 

 led to the opposite conclusion, from experiments made by him 

 upon the Jerusalem Artichoke ; but the nitrogen which this 

 vegetable appeared to have drawn from the air may, I conceive, 

 have been derived from the ammonia which rain-water always 

 contains, and which vegetable mould holds in a condensed state 

 within its pores. 



If this be admitted, it will then follow, that nitrogen, in order 

 to furnish food to plants, must always have been previously 

 combined with some other element, by which that tendency to 

 assume an elastic state, which would prevent its assimilation, may 

 be controlled. 



Hence the dependence of a productive wheat-crop upon an 

 abundant supply of animal manure, which, by disengaging am- 

 monia, affords it this necessary element in a fit condition to undergo 

 absorption ; and hence the superior efficacy of liquid manure over 

 every other kind, as it disengages a larger amount of the volatile 

 alkali. 



By reference to the Table now standing in the room,* it will be 



* The Table is extracted from one given by Hermbstoedl, in the ' Annalen 

 der Landwirthschaft,' vol. xxii., Part I., and is as follows : — 

 100 parts of wheat, in soil manured with — 



Human urine (dried) 

 Bullock's blood (dried) . 

 Human fgeces (dried) 

 Sheep's dung . 



Pigeon's dung , . 



Cow's dung . 

 Vegetable humus 

 Same, but not manured . 



