38 



NEW ENGLAND FARMER. 



f^rowing clover, in the sprinp;, should so soon descend, 

 and become incorporated with, and act upon, the 

 soil ; but so, it secm^, it does. 



Xiiw Haven, Dec. 11, 1848. 

 Hon. J. S. Skixxkij. 



Dear Su- : I have read with interest the various 

 articles in the December number of your valuable 

 journal; and desire to remark briefly upon one para- 

 graph relative to the effect of plaster of Paris, or o;yp- 

 sum. This paragraph is upon the ;5n9th page, and 

 the essential part of it as follows : " ]Mr. Stabler 

 states that land whifh had before been insensible to 

 the action of plaster of Paris, when raised by clover, 

 otherwise, t") a certain degree of fertility, becomes 

 alive to the influence of that cheapest of all ferti- 

 lizers, where it will act at all ; and this, like other 

 facts and considerations that might be adduced, 

 would seem to show that its action is not due to its 

 attraction of fcrtilizinr] powers from the atmosphere." 



The idea that plaster of Paris acted wholly by the 

 absorption of ammonia from the atmosphere, originat- 

 ed with the great German chemist, Liebig ; and the 

 sanction of his name has given it general credence. 

 I believe in this matter, as in several others relating 

 to agricultural science, he has erred through a lack 

 of practical knowledge, and perhaps through the 

 strong temptation to promulgate beautiful theories. 



I think that experience points more plainly to at 

 least a decided modification of his opinions. The 

 instance above cited is one which the ammonia 

 theory fails to explain. I at this moment recall one of 

 a yet more decided character. I know of several local- 

 ities, where, in adjoining fields, plaster exerts on the 

 one a very marked influence, and on the other is of 

 no use whatever. These two kinds of land are uni- 

 formly treated in the same manner, and always have 

 been ; yet this difference remains. There is no 

 doubt but ammoniacal manures would do good on 

 both of these soils ; and yet, on one of them, the use 

 of plaster never repays the outlay. Clearly we must 

 look for some new cxiilanation. This is to be found 

 in the chemical composition of plaster. It is com- 

 posed of lime and sulphuric acid, and is known to 

 chemists as sulphate of lime. Now, sulphuric acid is 

 well known to bo a powerful manure on many soils, 

 and it is unnecessary to praise lime. In the case of 

 the two adjoining fields above mentioned, the soil of 

 one was formed from a species of shale, which con- 

 tained scarcely a trace of cither of these substances ; 

 and that of the other from a rock Avhich had a pret- 

 ty good supply of both. The inference in such a 

 case is irresistible. We find the soil known to be 

 /^without the constituents of plaster benefited, while 

 the other remains unchanged. Now ammonia should 

 produce the same effect on both, if to supply it were 

 the use of plaster. We must, therefore, conclude 

 that the mineral constituents of the manure were of 

 primary importance here. 



Mr. Stabler's case is rather different. Here the 

 soil must be brought up to a certain degree of fertili- 

 ty, and then plaster acts. This will not seem strange 

 when we consider the composition of the soil ; that 

 ton or twelve mineral ingredients are requisite to 

 fertility. Plaster only contains two of these ; and 

 if others besides be wanting, the addition of it will 

 <vf course not supply them. But when they are 

 added by green cropping or otherwise, the gypsum 

 tolls at once. 



In all land, then, where plaster produces no decid- 

 ed effect, wc may expect to find the constituents of 

 that manure already present. 



These are but hints upon a subject which would 

 require very many pages for its full discussion. 



Plaster undoubtedly has a strong tendency to the 

 absorption of ammonia, and probably is often of bene- 

 fit in that way ; so that I would not so much con- 

 demn licbig's theory, as simply unite another with 



it ; these two causes of benefit to the soil affording 

 an explanation to almost every case of perplexity. 

 Much is yet to be learned on this subject ; but the 

 above view will, I think, be found correct in its 

 main features, as well as practical in its applications. 

 I enclose a copy of the last circular issued from 

 our laboratory, as I cannot remember having sent 

 joM one before. Wc have a fine class now of ten 

 students, and our numbers are increasing ; but not 

 so fast as the demand for instruction in agricultural 

 science. We shall not be able to supply it in a long 

 period, even if our numbers are more than doubled. 

 I am, sir, vours, rc-ipcctfuUy, 



"JOIIX P. NORTON. 



AGRICULTURAL CHEMISTRY. 



No manure can be taken up by the roots of plants, 

 unless water is present ; and water or its elements 

 exist in all the products of vegetation. The 

 germination of seeds does not take place without 

 the presence of ah* or oxygen gas. 



Plants are fouird by analysis to consist principally 

 of charcoal and aeriform matter. They give out by 

 distillation volatile compounds, the elements of which 

 are pure air, coally matter, inflammable air, and 

 azote, or the elastic substance v.'hich forms a part of 

 the atmosi^here, and which is capable of supporting 

 combustion. These elements they gain either by 

 their leaves from the air, or by their roots from the 

 soil. 



All manures from organized substances contain 

 the principles of vegetable matter, which, during 

 putrefaction, are rendered cither soluble in water or 

 aeriform ; and in these states, they are capable of 

 being assimilated to the vegetable organs. No one 

 principle affords the pabulum of vegetable life ; it is 

 neither charcoal, nor hydrogen, nor azote, nor oxy- 

 gen, alone, but all of them together, in various states 

 and various combinations. 



Plants require only a .certain quantity of manure, 



and excess may be detrimental, and cannot be useful. 



Slaked lime was used by the Romans for man^ir- 



ing the soil in which fi-uit-trecs grew. This we arc 



informed by Pliny. 



Nothing is more wanting to agriculture than ex- 

 periments in Avhich all the circumstances are minutely 

 and scientifically detailed. This art will advance 

 with rapidity in proportion as it becomes exact in its 

 methods. 



Discoveries made in the cultivation of the earth 

 are not merely for the time and country in which 

 they are developed, but they may be considered as 

 extending to future ages, and as ultimately tending 

 to benefit the human race ; as aflbrding subsistence 

 for generations yet to come ; as multiplying life, but 

 likewise providing for its enjoyment. 



Potatoes in general afford li-onr one fifth to one 

 seventh of their weight of dry starch. 



One fourth part of the weight of the potato, at 

 least, may be considered as nutritive matter. 



The principal consumption of the carbonic acid in 

 the atmosphere, seems to be in affording nourish- 

 ment to plants ; and some of them appear to be 

 supplied with carbon chiefly from this source. Car- 

 bonic acid gas is formed during fermentation, com- 

 bustion, putrefaction, and a number of operations 

 taking place upon the surface of the earth ; and there 

 is no other process known in nature by which it can 

 be destroyed btit by vegetation. 



It is usual to carry straw, that can be cmploj'cd 

 for no other purpose, to the dunghill, to ferment and 

 decompose ; but it is worth experiment, whether it 

 may not be more economically applied when chopped 

 small by a proper machine, and kept dry until it is 

 ploughed in for the use of a crop. In this case, 

 though it would decompose mirch more slowly, and 



