62 Mineral Food of Plants in the Soil. [Jan., 



marl, with a few obscure fossil, which appear to belong to fresh 

 water. Without doubt it is a valuable fertilizer. No. 4. — Indu- 

 rated marl or white lime, and belongs to the preceding. It is 

 quite compact and yellowish. It is rich in potash for a fresh 

 water deposit. 



No. 5. — Black tenacious or plaster marl. This also will form 

 a valuable fertilizer, though it is less rich in lime and entirely 

 destitute of potash. Accompanying the above specimens was 

 one labelled, " Part of a trunk of a tree converted into coal, found 

 embedded in lime rock." This is an interesting specimen, but is 

 really petroleum. 



It would appear from the above and from the examinations we 

 have made, that the South is really rich in fertilizers, and that 

 there is no necessity lor her lands to become poor and barren. 



MINERAL FOOD OF PLANTS IN THE SOIL. 



After all the differences of opinion which have arisen among 

 the men of science, in reference to what is the most important 

 element in the various kinds of manure, the question must be 

 settled by acknowledging on all sides, that no one in particular 

 will answer the demands of growing plants. There may be an 

 absence of any one, and the plant or its produce will be imper- 

 fect. The compensating power of Nature may restore the absence 

 of one by another of a corresponding class of substances, as the 

 want of our alkali in the soil in which a vegetable grows is often 

 supplied by another, that is taken up and incorporated in the 

 plant, but either the one or its substitute must be present. From 

 these theories of certain substances being the controlling ones in 

 manures, have arisen many fallacious practices, even in the days 

 of improved modern farming. 



Such was the old doctrine, that growing plants required only 

 water to nourish them, and to which the experiment of Van Hel- 

 mont was allowed for a long time to give countenance. He 

 planted a willow tree in a quantity of earth of ascertained weight, 

 in which it grew for live years, being watered with rain water 

 only. At the end of that })eriod, the willow had become a tree 

 weighing one hundred and fifty pounds, whilst the earth had but 

 slightly diminished in weight. The experiment, however, does 

 not appear to have been conducted with much accuracy, in ex- 

 cluding foreign substances from the water. Besides, the amount 

 of mineral substances in the willow is very small, and might very 

 readily be overlooked in weighing a quantity of earth sufficient 

 to support a tree of one hundred and fifty pounds. But Duhamel's 

 experiment wiihihe horse-chestnut and oaA:, watered v,''\th distilled 



