THE FARMER'S MAGAZINE. 



385 



mixed with the mass. It is thought that such a 

 preparation is move effectual than marl by itself. 

 Frequency of marling may produce a hurtful loose- 

 ness in the land, which is very easily removed by 

 the pasturing of the land in rest for some few 

 years. The avaricious use of tlie plough has pro- 

 duced the trivial hurtful effects that have been ob- 

 served from the use of marls. 



The action of marls is usually attributed to the 

 quantity of calcareous matter which they contain, 

 and to the change it creates in the land by a me- 

 chanical action, and a mucilaginous matter that is 

 derived from the exuvipe of animals. The ex- 

 tremely minute blending of the ingredients of marl 

 has been supposed to constitute the fertilizing 

 quality, each particle having the power of exerting 

 its peculiar i)roperty on the soil, and on each other, 

 and of retaining or giving out the substances they 

 may form, that are favourable to vegetation by the 

 different agencies and combinations. The clays 

 impart moisture to the sandy parts, and the sand 

 prevents the clay from being too adhesive, and 

 thus the respective qualities are exerted advanta- 

 geously on each other. An oleaginous nature has 

 been discovered in the composition, arising from 

 the mixture of the substances with animal and 

 vegetable matter, and to this property much of the 

 fertihty which it produces has been ascribed. It 

 is also thought to be an absorbent earth, composed 

 of clay and limestone, and that the useful quality 

 is derived from the very intimate mixture of these 

 valuable ingredients. 



The quantity of calcareous matter is no cer- 

 tain criterion either of the quality or of the 

 effect, for the inarls that effervesce Uttle or 

 none by the application of an acid are good 

 manures, and marls of great difference in colour 

 and in chemical composition have been dug from 

 the same pit, where they lay contiguous and almost 

 mixed with each other, and have shown no discern- 

 ible difference of effect in any crop, when appHed 

 in equal quant'ties on the same soils. On coarse, 

 heathy pastures, an application of marl produces 

 the usual effect of calcareous matters in banishing 

 the rough foggage, and substituting a close sward 

 of finer grasses. This result will be obtained by 

 the use of any other substances, provided it be 

 properly prepared for the intended purpose. 



Marls exposed for years retain the same proper- 

 ties as when newly dug — do not effervesce after 

 calcination, and good marls feel greasy when 

 touched, and friable when dry, and the land is 

 generally good above them ; the red and blue 

 colours, with yellow veins, are found to be the best 

 in quality. Marls are known by breaking into small 

 pieces from exposure ; by the crackling of the par- 

 ticles of dry marl in the fire, like salt, and by 

 throwing up bubbles to the surface of the water 

 by which it is covered, and by gradually dissolving 

 and forming with the water a soapy substance like 

 a paste, and not unfrequently of a liquid nature, 

 the marl remaining dissolved and suspended in the 

 water without any coagulation. But water alone 

 will produce bubbles when poured on certain dry 

 clays, and hence it is recommended to subject marls 

 to water for a time before being tested by an acid. 

 Marl contains no alkaline salt, as it imparts no 



quality, smell, nor taste, when digested or builec), 

 and has nothing soluble in water. Muriatic acid may 

 be applied till the effervescence ceases : the loss of 

 weight will show the quantity of air expelled, and 

 the remainder is earths. The quantity of calcareous 

 earths may be ascertained by dissolving the marl 

 in muriatic acid, diluting the liquid with water, 

 passing it through a filtering paper, and then pre- 

 cipitating the calcareous earths from the clear 

 liquid by a solution from some fixed alkaline salt. 



Chalk. 



Chalk is a calcareous earth, and the most recent 

 formation of the carbonate of lime. It is divided 

 into hard and soft chalk, and rests on the third sand- 

 stone formation : effervesces strongly with acids, 

 and is distinguished from magnesia by not being 

 disturbed by the caustic volatile alkali. Its spe- 

 cific gravity has been variously estimated at 2.252, 

 2.316, 2.657, 2.226, and it contains per cent. — 



Lime 56.5 or 53 



Carbonic acid . . . . 43.0 „ 42 



Water 0.5 „ 3 



Alumina 0.0 2 



100.0 100 



Hard chalk is burned like lime, for building and 

 manuring purposes, and soft chalks are used in 

 top-dressing arable and grass lands, as clover leys, 

 stubbles intended for wheat, and for bare summer 

 fallows. It should be dug.from the pits in autumn, 

 and laid at once on the land to be dressed; the 

 rains and frosts will be useful in pulverizing it, and 

 what is left unreduced must be broken by means 

 of axes and hammers. Some attention is required 

 in getting chalk properly pulverized : the fat unc- 

 tuous kinds soon crumble on exposure, but the 

 harder sorts require longer time and more labour. 

 The quantity laid on per acre varies very much, ac- 

 cording to local circumstances; a mediutn may be 

 stated at 40 to 50 cart loads, and from 8 to 15 loads 

 of a waggon. The expense of carrying a rude, 

 heavy article very much restricts the use of the 

 substance, and chalk in the original state falls un- 

 der the list of these materials. 



The use of chalk as a top-dressing is much best 

 obtained in the form of a compost with earths and 

 peat, as is the case with all calcareous substances. 

 It is a mild agent, and possesses no destructive 

 solvent quality, which attaches to the limestones 

 after undergoing the action of fire. In an un- 

 mixed state, chalk absorbs moisture and attracts 

 acids, which hasten putrefaction ; and the mechani- 

 cal action lies in uniting with clays, and forming a 

 resemblance of marl, and preventing the stubborn 

 hardness of the land in summer, and the wet ad- 

 hesiveness in winter. On grass lands, it has the 

 usual property of manures or any application in 

 banishing the coarser herbage, and bringing in their 

 place white clovers and grasses of a sweeter quality. 

 Chalk has a very strong affinity for water, and con- 

 sequently is most useful on dry sands and gravels, by 

 attracting and retaining moisture for the use of the 

 growing plants. And this use is very much as- 

 sisted by being mixed with earths, and brought 

 into contact with animal and vegetable remains in 



