1838] 



FARMERS' REGISTER. 



655 



and insoluble sulphate of iron. The principal 

 grasses in Priestley meadow are, meadow Ibx- 

 tail, cock's -foot, meadow fescue, florin, and sweet- 

 scented vernal grass. I have examined the ashes 

 of three of these grasses, meadow Ibx-tail, cock's- 

 ibot, and florin. They contained a considerable 

 proportion of gypsum. 



Vitriolic impregnations, in soils where there is 

 no calcareous matter, as in a soil from Lincolii- 

 ehire, to which I referred in the fourth lecture, are 

 injurious ; but it is probably in consequence of their 

 supplying an excess of ferruginous matter to the 

 eap. Oxide of iron in small quantities forms a 

 usetiil part of soils ; nnd, as is evident from the 

 details in the third lecture, it ia found in the ashes 

 of plants ; and probably, is hurtful only in its acid 

 combinations. 



I have just mentioned certain peats, the ashes 

 of which afford gypsum ; but it must not be infer- 

 red from this that all peats agree with them. 1 

 have examined various peat-ashes from Scotland, 

 Ireland, Wales, and the northern and western parts 

 of England, which contained no quantity that 

 could be useful ; and these ashes abounded in sili- 

 ceou-?, aluminous earths, and oxide of iron. 



Lord Charleville found in some peat-ashes from 

 Ireland sulphate of polassa, i. e. the sulphuric acid 

 combined with potassa. 



Vitriolic matter is usually formed in peats; and 

 if the soil or substratum is calcareous, the ultimate 

 result is the production of gypsum. In general, 

 when a recent peat-ash emits a strong smell re- 

 sembling that of rotten eggs when acted upon by 

 vinegar, it will furnish gypsum. 



Phosphate of lime is a combination of phospho- 

 ric acid and lime, one proportion of each. It is a 

 compound insoluble in pure water, but soluble in 

 water containing any acid matter. It Ibrms the 

 greatest part of calcined bones. It exists in most 

 excrementitious substances, and is found both in 

 the straw and grain of wheat, barley, oats, and 

 rye, and likewise in beans, peas, and tares. It 

 exists in some places in these islands native; but 

 only in very small quantities. Phosphate of lime 

 is generally conveyed to the land in the composi- 

 tion of other manure; and it is probably necessary 

 to com crops and other white crops. 



Bone-ashes ground to powder will probably be 

 found useful on arable lands containing much ve- 

 getable matter, and may perhaps enable soft peats 

 to produce wheat; but the powdered bone in an 

 uncalcined state is much to be preferred in all 

 cases when it can be procured. 



The saline compounds of magnesia will require 

 very little discussion as to their uses as manures. 

 The most important relations of this subject to ag- 

 riculture have been considered in the former part 

 of this lecture, when the application of the mag- 

 nesian limestone was examined. In combina- 

 tion with sulphuric acid magnesia forms a soluble 

 salt. This substance, it is stated by some inqui- 

 rers, has been found of use as a manure; but it is 

 not found in nature in sufficient abundance, nor is 

 it capable of being made artificially sufficienliy 

 cheap to be of useful application in the common 

 course of husbandry. 



Wood ashes consist principally of the vegetable 

 alkali united to carbonic acid; and as this alkali is 

 found in almost all plants, it is not difficult to con- 

 ceive that it may form an essential part of their 

 organs. The general tendency of the alkalies is 



to give solubility to vegetable matters; and in this 

 way they may render carbonaceous and other sub- 

 stances capable of being taken up by the tubes in 

 the radicle fibres of plants. The vegetable alkali, 

 likewise, has a strong attraction Ibr water, and 

 even in small quantities may tend to give a due 

 degree of moisture to the soil, or to other ma- 

 nures*; though this operation, Irom the small 

 quantities used, or existing in the soil, can be only 

 of a secondary kind. 



The mineral alkali or soda is found in (he ashes 

 of sea-weed, and may be procured by certain che- 

 mical agencies from common salt. Common salt 

 consists of the metal named sodium combined 

 with chlorine; and pure soda consists of the same 

 metal united to oxygen. When water is present 

 which can allord oxygen to the sodium, soda may 

 be obtained in several modes fiom salt. 



The same reasoning will apply to the operation 

 of the pure mineral alkali, or the carbonated alkali, 

 as to that of the vegetable alkali; and when com- 

 mon salt acts as a manure, it is probably by en- 

 tering into the composition of the plant in the same 

 manner as gypsum, phosphate of lime, and the 

 alkalies. Sir John Pringle has stated that salt in 

 small quantities assists the decomposition of ani- 

 mal and vegetable matter. This circumstance 

 may render it useful in certain soils. Common 

 salt likewise isofiensive to insects. That in small 

 quantities it is sometimes a useful manure, I be- 

 lieve is fully proved; and it is probable that its ef- 

 ficacy depends upon many combined causes. 



Some persons have argued against the employ- 

 ment of salt; because, when used in large quan- 

 tities, it either does no good, or renders the ground 

 steril; but this is a very unfair mode of reason- 

 ing. That salt in large quantities rendered land 

 barren, was known long before any records of ag- 

 ricultural science existed. We read in the Scrip- 

 tures, that Abimelech took the city of Shechem, 

 "and beat down the city, and sowed it with salt," 

 that the soil might be for ever unfruitful. Virgil 

 reprobates a salt soil; ana Pliny, though he re- 

 commends giving salt to cattle, yet affirms that 

 when strewed over land it renders it barren. But 

 these are not arguments against a proper applica- 

 tion of it. Refuse salt in Cornwall, which, how- 

 ever, likewise contains some of the oil and exuvia; 

 of fish, has long been known as an admirable 

 manure. And the Cheshire farmers contend for 

 the benefit of the peculiar produce of their country. 

 It is not unlikely that the same causes influence 

 the effects of salt as those which act in modifying 

 the operation of gypsum. Most lands in this 

 island, particularly those near the sea, probably 

 contain a sufficient quantity of salt for all the pur- 

 poses of vegetation ; and in such cases the supply 

 of it to the soil will not only be useless, but may 

 be injurious. In great storms the spray of the sea 

 has been carried more than 50 miles from the 

 shore ; so that from this source salt must be often 

 supplied to the soil. I have found salt in all the 

 sandstone rocks that I have examined, and it must 



* Tfiis effect is well illustrated by the dampness of 

 walls and floors impregnated with minute quantities of 

 deliquescent salts, such as exist in sea- water. In fur- 

 ther illustration, I may mention a striking instance of 

 dampness, amounting to a constant dropping of wa- 

 ter, from the ceiling of an uninhabited room impreg- 

 nated with salt, from brine having been spilt on the 

 floor of the room above some years previously. — J. D, 



