No. 105.] 219 



growth of plants ; yet its presence has never been directly detected, 

 and only indirectly by favorable opportunities when absorbed in 

 snow or rain water. Eminent and accurate experiments had not dis- 

 covered even this until within a few years. 



It is not denied that a bright light may be thrown on the practice 

 of agriculture by carefully conducted analyses of soils. The results 

 of many examinations which have been made, show frequently a 

 very striking difference between fertile and barren soils. But these 

 analyses were conducted with the most rigid care and accuracy, by 

 men of such skill and eminence as could hardly be expected to be at 

 the service of any common practical farmer. And after all accurate 

 experiments in cultivation would determine all that is necessary in 

 many points of practice, and would in any case be needed as a test 

 of the truth of the theory. 



It is to be hoped that chemists will continue to pursue their inves- 

 tigations on doubtful points, until certainty, if possible, may be ar* 

 rived at; and that all well-established facts may have as extensive 

 application in farming as their value merits. But it must be admit- 

 ted that there has been a disposition to take too much for granted, 

 and to overstate the certainty of success in connecting chemistry 

 with agriculture. The precision, so striking in other sciences, and 

 other applications of this science to various arts, does not hold in case 

 of the growth of plants, which, though governed by fixed laws, is 

 too much controlled by circumstances, and too much obscured from 

 view, to be thoroughly understood. This growth is slow and imper- 

 ceptible to the sight ; plants are surrounded by an invisible air above 

 ground, and are hidden from view below ground ; their surfaces re- 

 ceive nourishment by pores only seen by powerful microscopes ; the 

 nourishment is drawn from vapors and floating gases in the air, and 

 liquids in the earth charged with many substances in minute propor- 

 tions ; and the whole process is entirely beyond the reach of the clo- 

 sest scrutiny of the eye. 



It is not surprising therefore that there should be a difference of 

 opinion among high authorities. The constituents of vegetable mould 

 have led to much dispute, and no less than twenty different substan- 

 ces have been discovered or named by various chemists. Dr. Dana, 

 in attempting to prove the inutility of applying lime and potash as 

 manures, shows that nearly all soils contain lime and potash enough 



