654 



FARMERS' REGISTER. 



[No. 11 



tity of water, and making with it a coherent mass. 

 Gypsum is soluble in about 500 times its weight 

 of cold water, and is more soluble in hot water; so 

 that when water has been boiled in contact with 

 gypsum, crystals of this substance are deposited 

 as the water cools. Gypsum is easily distinguish- 

 ed when dissolved by its properties of affording 

 precipitates to solutions of oxalates and barytic salts. 



Great diHerence of opinion has prevailed 

 amongst agriculturists with respect to the uses 

 of gypsum. It has been advantageously used in 

 Kent, and various testimonies in favor of its effi- 

 cacy have been laid before the Board of Agricul- 

 ture by Mr. Smith. In America it is employed 

 with signal success; but in most counties of Eng- 

 land it has failed, though tried in various ways 

 and upon different crops. 



Very discordant notions have been formed as to 

 the mode of operation of gypsum. It has been 

 supposed by some persons to act by its power of 

 attracting moisture from the air; but this agency 

 must be comparatively insignificant. When com- 

 bined with water, it retains that fluid too powerful- 

 ly to yield it to the roots of the plant, and its ad- 

 hesive attraction for moisture is inconsiderable; the 

 small quantity in which it is used, likewise, is a 

 circumstance hostile to this idea. 



It has been said that gypsum assists the putre- 

 faction of animal substances, and the decomposi- 

 tion of manure. I have tried some experiments 

 on this subject, vvhicti are contradictory to the no- 

 tion. I mixed some minced veal with about ^h^ 

 part of its weight of gypsum, and exposed some 

 veal without gypsum under the same circum- 

 stances; there was no difference in the time in 

 which they began to putrefy, and the process 

 seemed to me most rapid in the case in which 

 there was no gypsum present. I made other simi- 

 lar mixtures, employing in some cases larger and 

 in some cases smaller quantities of gypsum; and 

 I used pigeons' dung in one instance instead of 

 flesh, and with precisely similar results. It cer- 

 tainly in no case increased the rapidity of putre- 

 faction. 



Though it is not generally known, yet a series 

 of experiments has been carried on for a great 

 length of time in this country upon the operation 

 of gypsum as a manure. The Berkshire and the 

 Wiltshire peat-ashes contain a considerable por- 

 tion of this substance. In the Newbury peat- 

 ashes I have found from one-fourth to one-third of 

 gypsum ; and a larger quantity in some peat- 

 ashes from the neighborhood of Stockbridge : the 

 other constituents of these ashes are calcareous, 

 aluminous, and siliceous earth, with variable quan- 

 tities of sulphate of potassa, a little connnon salt, 

 and sometimes oxide of iron. The red ashes 

 contain most of this last substance. 



These peat-ashes are used as a top-dressing 

 for cultivated grasses, particularly sainfoin and 

 clover. In examining the ashes of sainfoin, 

 clover, and |rye grass, I found that they afforded 

 considerable quantities of gypsum ; and this sub- 

 stance, probably, is intimately combined as a ne- 

 cessary part of their woody fibre. If this be al- 

 lowed, il is easy to explain the reason why it ope- 

 rates in such small quantities ; for the whole of a 

 clover crop, or sainfoin crop, on an acre, according 

 to my estimation, would afford by incineration only 

 three or four bushels of gypsum. In examining 

 the soil in a field near Newbury, which was taken 



from below a footpath near the gate, where gyp- 

 sum could not have been artificially furnished, I 

 could not detect any of this substance in it ; and 

 at the very time I collected the soil, the peat-ashes 

 were applied to the clover in the field. The rea- 

 son why gyp.«um is not generally efficacious, is 

 probably because most cultivated soils contain it 

 in sufficient quantities for the use of the grasses. 

 In the common course of cultivation, gypsum is 

 furnished in the manure ; for it is contained in sta- 

 ble dung, and in the dung of all cattle fed on grass; 

 and it is not taken up in corn crops, or crops of 

 peas and beans, and in very small quantities in 

 turnip crops; but where lands are exclusively de- 

 voted to pasturage and hay, it will be continually 

 consumed. I have examined lour different soils, 

 cultivated by a series of common courses of crops, 

 for gypsum. One was a light sand from Norfolk; 

 another a clay, bearing good wheat, from Middle- 

 sex; the third a sand from Sussex ; the fourth a 

 clay from Essex. I found gypsum in all of them ; 

 and in the Middlesex soil it amounted nearly to 

 one per cent. Lord Dundas informs me, that 

 having tried gypsum without any benefit on two 

 of his estates in Yorkshire, he was induced to 

 have the soil examined for gypsum, according to 

 the process described in the fourth lecture, and 

 this substance was found in both the soils. 



Should these statements be confirmed by future 

 inquiries, a practical inference of some value may be 

 derived from them. It is possible that lands which 

 have ceased to bear good crops of clover, or arti- 

 ficial grasses, maj' be restored by being manured 

 with gypsum. I have mentioned that this sub- 

 stance is found in Oxfordshire ; it is likewise 

 abundant in many other parts of England ; in 

 Gloucestershire, Somersetshire, Derbyshire, York- 

 shire, &c. ; and requires only pulverisation for its 

 preparation.* 



Some very interesting documents upon the use 

 of sulphate of iron or green vitriol, which is a salt 

 produced from peat in Bedfordshire, have been 

 laid before the Board by Dr. Pearson ; and I have 

 witnessed the fertilizing effects of a ferruginous 

 water used for irrigating a grass meadow made by 

 the Duke of Manchester, at Priestley Bog, near 

 Woburn, an account of the produce of which has 

 been published by the Board of Agriculture. I 

 have no doubt that the peat salt and the vhriolic 

 water acted chiefly by producing gypsum. 



The soils on which both are efficacious are cal- 

 careous; and sulphate of iron is decomposed by 

 the carbonate of lime in such soils. The sulphate 

 of iron consists of sulphuric acid and oxide oi'iron, 

 and is an acid and a very soluble salt : when a 

 solution of it is mixed with carbonate of lime, the 

 sulphuric acid quits the oxide of iron to unite to 

 the lime, and the compounds produced are insipid 

 and comparatively insoluble, 



I collected some of the deposition from the fer- 

 ruginous water on (he soil in Priestley meadow. I 

 found it consisted of gypsum, carbonate or iron, 



* Ttie manner in whicti gypsum acts in promoting the 

 vegetation of tfie grasses, is still a disputed question. 

 M. De CandoUe rejects the opinion expressed in the 

 text, and adopts that of M. Soquet, somewhat modi- 

 fied ; he thinks that gypsum is not so much useful in 

 the soil, if indeed it is at all, as when scattered on the 

 surface, and that it acts chiefly by stimulating the 

 leaves of the plants to which it adheres. (Vide Phy- 

 siologic Vegetale, p. 1273. — J. D. 



