THE FARMER'S MAGAZINE. 



209 



The chalk marl in Norfolk contains, in 100 grains — 



Grains. 



Chalk ..- 85 



Sand 10 



Clay 5 



100 



Clay marl in the same county, in 100 grains, con- 

 tains — Grains. 



Clay with some iron 50 



Impure chalk 43 



Sand r 7 



100 



A kind called " dove marl," from the similarity to 

 pigeon-dung, contains as much as 98 per cent, of car- 

 bonate of lime. 



ftlarls have been supposed to be derived from the ruins 

 of the primary and secondary rocks, worn down, carried 

 about, agitated, and deposited without any relation to 

 the laws of specific gravity. Animal remains arc found 

 at considerable depths, and even stones of great weight 

 are met with where no rocks of the same or a similar 

 kind are known to exist in the surrounding locality or 

 in the adjoining geological formations. Fire wholly 

 changes the nature of bodies that are subjected to its 

 violent influence, and gives them qualities they did not 

 before possess, and banishes others which they never 

 after recover. Decomposed lavas are exceedingly 

 fruitful, and the heat of volcanoes produce a most 

 luxuriant vegetation in all places within their reach ; 

 and it has been very fancifully conjectured that marl 

 may retain some of the qualities which its constituent 

 substances acquired as rocks by the igneous agency of 

 their production. Such conjectures are amusing, but 

 add nothing to the science or the systematized expe- 

 rience of any art, or to the use of any material. 



For the sake of conciseness, marls may be divided 

 into two kinds — shelly and earthy. Minute accuracy 

 will make many subdivisions ; but these two names will 

 mark the distinction of having more earths or lime in 

 the constitution of the substance. Shell marl is gener- 

 ally found under mosses, and at the bottom of lakes, 

 soft and of a bluish-white colour, and seems to be a 

 natural deposit where water has been stagnant. The 

 composition usually partakes of the nature of the sur- 

 rounding earths, and may properly be considered as a 

 compost of organic matters with earths and calcareous 

 materials reduced without the action of fire. It often 

 occurs in ponds and land-locked bogs, on the sides of 

 hills and the banks of river, formed by the accumulation 

 and decomposition of small shells, as wilks and peri- 

 winkles, and also bivalves, and lying in beds of different 

 thickness, running horizontally, but seldom of great 

 extent. It has been found to contain 84 per cent, of pure 

 lime. 



Clayey marls are found below mosses, and in low wet 

 places at the base of hills, and in the valleys between 

 them. The composition of the quality varies much — 

 from 15 to 40 per cent, of calcareous matter, and the 

 remainder of clay and sand, with mixtures of sand, 

 loam, clay, and chalk, according to the nature of the 

 animal, vegetable, and earthy matters which abound in 

 the locality, and which have been collected and 

 decomposed together. Separate and distinct beds of 

 clayey and sandy marls have been found alternating with 

 clays and limestone, of which clay is the undermost 

 stratum, the marl being of different colours, as it has 

 been exposed ta the elements composing and sur- 

 rounding it, the redness showing the presence of iron, 

 whiteness that of calx, the blue and yellow showing the 

 clayey composition mixed with other substances. It is 

 sometimes found very hard to dig, with lumps of chalk 



and limestone in it, lying under stifl" clays and low black 

 ground, and very compact and greasy — sometimes 

 flaky, smooth, and red in colour, crumbling, and of a 

 very good quality. Other kinds are slaty, and of the 

 shape of flags, and of a bluish colour; are easily dis- 

 solved by the action of rains and frosts, and are of good 

 quality. 



Marls are well suited to be used as a manure in top- 

 dressing grass lands, as the substance crambles by ex- 

 posure, and the particles are most minutely divided. 

 The most preferable application consists in laying it on 

 grass leys in the end of autumn or in the early winter, 

 when the herbage will be of little value, and when the 

 changes of weather will effect the decomposition of the 

 marl by the time the grass shoots in the spring. It will 

 thus secure an even spreading over the surface, and the 

 bush harrow and the roll being afterwards employed, 

 the particles will be well reduced, and pressed into the 

 soil. The crop of grass is greatly improved ; and if 

 the land is ploughed for a grain crop in the fol- 

 lowing years, the marl will be thoroughly matted in the 

 turf, and the vegetable sward which it it has raised will 

 most materially promote by its decomposition the sub- 

 sequent fertility of the land. This mode affords time 

 for the crumbling of the marl, and it raises a close 

 vegetable growth, on the decay of which the future 

 crops of grass or grains depend for nutriment. The 

 substance that is used for top-dressing cannot be incor- 

 porated with the soil from want of arable culture, and 

 consequently the effects depend on the influence which 

 it is able to exert on the materials with which it comes 

 into contact. By raising a large quantity of grassy 

 herbage in the shape of roots, leaves, "and culms, it 

 affords by the decomposition of these substances, when 

 the land is ploughed, a vegetable " pabulum" to the 

 growing crop, to which no manure yet known is 

 superior, if any one be equal to it, either In power or 

 durability. Consequently all top-dressing of an earthy 

 nature should be used with the view of producing this 

 growth for the benefit of future crops. The quantity of 

 marls used in this way on grass lands may be stated at 

 an average of forty to sixty cart-loads of two horses. 



The use of marls on the fallows of barley and turnips, 

 in the spring, admits of the better mixing with the soil, 

 provided the suitable reduction of the marl be accom- 

 plished, which may be done by exposure, if the weather 

 be favourable, before the last ploughing of the land, and 

 when the nature of the marl itself favours the dissolu- 

 tion. It is often necessary to go over the work, and 

 break the lumps of the marl with hand-mallets. The 

 weather is the best operator ; and the time of exposure 

 may produce some useful reciprocal actions. In what- 

 ever manner marls are applied, it is most absolutely ne- 

 cessary that the substance be reduced as fine as possible, 

 by breaking the lumps, spreading it evenly by harrow- 

 ing and rolling when dried after rains, and by being 

 ploughed into the ground by means of a shallow furrow. 

 Some marls will crumble to powder immediately on ex- 

 posure, or very soon after : others require the changes 

 both of summer and winter, and also much attention in 

 improving on the action of the weather, by breaking, 

 harrowing, and rolling. 



The effects of marl have been much the greatest on 

 dry, heathy grounds, that have been converted into 

 arable cultivation, and on sandy loams; and on all sandy 

 lands, generally, the applications have been very bene- 

 ficial. On raw, damp loams, reports have been unfa- 

 vourable. The marl attracts moisture, and thus in- 

 creases the poachy looseness of the land. Clays are 

 much improved by large quantities of marl ; but the 

 clay must be well pulverized, in order to facilitate the 

 incorporation with the marly substance. Practice di- 

 rects the use of clayey marls on all light lands, and the 



