102 



^Agricultural Chemistry. 



Vol. ly. 



what he considers the best plan for cultivating- 

 potatoes, but they must be physiological po- 

 tatoes to bear to have " their branches, all but 

 the tops, covered up three times," before they 

 are allowed to go to seed ! Now after this, 

 if any one will turn to the 36th page of the 

 Cabinet, and peruse the article "on hilling 

 potatoes," written evidently by a practical 

 man, he will, I think, be capable of forming 

 a correct judgment of the value of a theoret- 

 ical "study of the elements of science." 



A Jersey Farmer. 

 Rancocus Creek, Sept. 24th, 1839. 



For the Farmers' Cabinet. 

 Agricultural Chemistry. By Davy* 



[Continued from page 21.1 



It is a common practice amongst farmers to 

 suffer the farm-yard dung to ferment till the 

 fibrous texture of the vegetable matter is en- 

 tirely broken down, and till the manure be- 

 comes perfectly cold, and so soft as to be easily 

 cut by the spade. 



Independent of the general theoretical 

 views unfavorable to this practice, founded 

 upon the nature and composition of vegetable 

 substances, there are many arguments and 

 facts which show that it is prejudicial to the 

 interests of the farmer. 



During the violent fermentation which is 

 necessary for reducing farm-yard manure to 

 the state in which it is called short muck, 

 not only a large quantity of fluid, but like- 

 wise of gaseous matter, is lost ; so much so, 

 that the dung is reduced one half, or two 

 thirds in weight; and the principal elastic 

 matter disengaged is carbonic acid, with some 

 ammonia; and both these, if retained by the 

 moisture in the soil, are capable of becoming 

 an useful nourishment of plants. 



In the writings of scientific agriculturists, 

 a great mass of facts may be found in favor of 

 the application of farm-yard dung in a recent 

 state. Mr. Young, in the essays on manures, 

 adduces a number of excellent authorities 

 in support of the plan. Many who doubted 

 have been lately convinced ; and perhaps there 

 is no subject of investigation in which there 

 is such a union of theoretical and practical 

 evidence. I have myself within the last ten 

 years witnessed a number of distinct proofs 

 on the subject. I shall content myself with 

 quoting that which ought to have, and which 

 I am sure will have, the greatest weight 

 among agriculturists. Within the last seven 

 years Mr. Coke has entirely given up the 

 system formerly adopted on his farm of apply- 

 ing fermented dung ; and he informs me that 

 his crops have been since, as good as they 

 ever were, and that his manure goes nearly 

 twice as far. 



In cases where farm yard dung cannot be 

 immediately applied to crops, the destructive 



fermentation of it should be prevented as much 

 as possible. The surface should be defended 

 as much as possible from the oxygen of the 

 atmosphere; a compact marl, or a tenacious 

 clay, offers the best protection against the air ; 

 and before the dung is covered over, or, as 

 it were, sealed up, it should be dried as much 

 as possible. If the dung is found at any time 

 to heat strongly, it should be turned over, and 

 cooled by exposure to air. 



When dung is to be preserved for any time, 

 the situation in which it is kept is of import- 

 ance. It should, if possible, be defended from 

 the sun. To preserve it under sheds would 

 be of great use ; or to make the si te of a d ung- 

 hill on the north side of a wall. The floorer 

 which the dung is heaped, should have an in- 

 clination to the centre, and there should be 

 drains connected with a small well, furnishec 

 with a pump, by which any fluid matter maj 

 be collected for the use of the land. It to( 

 otlen happens that a dense mucilaginous anc 

 extractive fluid is suffered to drain away fron 

 the dung-hill, so as to be entirely lost to th< 

 farm. 



In America, plaster of paris, or gypsum, i; 

 employed with signal success ; but in mos 

 counties of England it has failed, though triei 

 in various ways, and upon different crops. 



Very discordant notions have been formei 

 as to the mode of operation of gypsum. I 

 has been supposed by some persons to act b; 

 its power of attracting moisture from the air 

 but this agency must be comparatively insig 

 nificant. When combined with water, it re 

 tains that fluid too powerfully to yield it t 

 the roots of the plant, and its adhesive attrac 

 tion for moisture is inconsiderable ; the smal 

 quantity in which it is used, likewise is a cii 

 cumstance hostile to this idea. 



It has been said that gypsum assists thi 

 putrefaction of animal substances, and thi 

 decomposition of manure. I have tried somi 

 experiments on this subject, which are con 

 tradictory to the notion. 1 mixed some mincei 

 veal with about one-hundredth part of it 

 weight of gypsum, and exposed some vea 

 without gypsum under the same circum 

 stances ; there was no difference in the timi 

 in which they began to putrefy, and the pro 

 cess was most rapid in the case in which then 

 was no gypsum present. I made other simi 

 lar mixtures, employing in some cases large 

 and in some cases smaller quantities of gyp 

 sum ; and I u?ed pigeon's dung in one instance 

 instead of flesh, and with precisely simila 

 results. It certainly in no case increased th( 

 rapidity of putrefaction. The Berkshire an( 

 the Wiltshire peat ashes, which are used a; 

 a top-dressing for cultivated grasses, particu 

 larly sainfoin and clover, contain a considera 

 ble portion of gypsum. In the Newborn 

 peat ashes, I have found from one-fourth tt 



