But, if marle be exposed to the action of a moderate fire, the clay in its compofition becomes hard, it is no longer capable of absorbing water, or of being affected by it. in any degree; fo that the marle, if not of a very pure fort, or fuch as contains only a very small proportion of clay mixed with the fand in its compofition, will become firmer after burning than it was before, and be in this ftate with more difficulty reduced to powder, which is the reverse of what happens with limestone.

Marle, therefore, is fit to act as a manure without any other preparation than digging it from the pit and spreading it upon the ground, whereas, limeftone always requires to be reduced to a powder, either by burning or otherwife, before it can be of any use in

that way,

But, as limeftone is at once reduced into much smaller parts by calcination than marle can ever be brought to at first, a much smal

ler

ler proportion of lime may be equally spread over an acre of ground, than of marle ; and therefore it will produce, in equal quantities, a much more fenfible effect.

$ 31.

The difcerning reader, who attends to thefe circumftances, will eafily perceive the reafons for all the peculiarities of practice that prevail with regard to the application of lime and marle, and be able, without embarraffment, to judge in what cases it may be moft for his profit to employ the one or the other of these manures, when they are both within his power.

the in

He may ascertain the proportion of calcareous matter contained in the marle, by the fame process already defcribed for trying limestone, p. 409, and thus coin pare trinfic value of the lime and marle in cafe. For this is always in proportion to the calcareous matter contained in either.

any

He

He will eafily perceive, however, that the fame quantity of calcareous matter in the ftate of lime, will produce a much great

er effect, than when it is in the ftate of marie; because it is divided into infinitely finaller particles, can be more equally fpread upon the ground, and more intimately mixed with the soil.

Hence it univerfally happens, that a much larger quantity of marle is applied at one dreffing, than of lime. From one to two hundred cart loads of marle, is a common dreffing to an acre; that is, from three thoufand to fix thousand bufhels;whereas, from thirty to three hundred bufhels of lime, is a common dreffing for an acre of ground.

In these proportions, it is reafonable to think, that the effects of the marle will continue to be longer felt, than thofe of the lime: For, as the marle is gradually broken into smaller pieces every year, thefe will fuccef

fively mix with the foil, and produce an effect nearly fimilar to what might be expected from an annual dreffing of lime.

It may likewife be expected, that a full dreffing of marle, in the proportions above named, will produce a more capital improvement upon light fpungy grounds, than an ordinary dreffing of lime;-becaufe, independent of the calcareous matter, the large proportion of clay applied in this manner may produce fome alteration on the quality of the foil. This alteration, however, will be different according to the nature of the extraneous matter contained in the marle.

But, as all marles contain clay,-it is natural to think, that clay lands will not be benefited at all by this circumstance,—as the calcareous matter alone in the marle will be to these an ufeful addition.Hence, light land will be in general more highly benefited by this manure than clay

land,

land, which has given rife to the following

vulgar rhyme.

He that marles fand,

Will foon buy land;

But he that marles clay,
Throws all away.

The truth, however, is, that clay is as highly benefited by the calcareous matter in marle as fand is,-fo that a rich marle will be nearly equally beneficial in both cases.

But, there are some kinds of clays that are very free from any mixture of fand, and affume the appearance of marle, and are fo called, altho' they hardly contain almost any calcareous matter at all.-These may, perhaps, on fome occafions, be an useful addition to light foils, and worth the expence of carrying to them when near,— but could never be of almost any ufe at all upon clayey foils. It has probably been fome

poor kind of marle of this fort that has given rifeto the proverb above quoted.