and fome valuing another fort more highly, without being able to affign any fatisfactory reafon for the preference they give in either cafe.

It is of importance that this matter should be elucidated.

Altho' it does not always happen, yet, in many parts of the country, the real nature of lime is fo little understood, that the weightiest lime is preferred to that which is lighter; because it is imagined the first has more Jubftance, and will therefore produce a more powerful effect upon ground than the finest and lighteft lime.

But there feems to be no reafon to think that there is any difference in the specific gravity of different parcels of pure calcareous matter, when fully calcined; therefore, if there is any difference in the weight of various forts of line, it inuft arife entirely from a variation in the quantity, or gravity of fome

fome extraneous matter that is mixed with the lime.

And, as fand is almoft the only extraneous body that is ever found in lime-ftone;-and, as fand is always of much greater fpecitic gravity than pure quick-lime,-it follows, that the weighty lime only owes its fuperior gravity to a larger proportion of fand that is mixed with it.

But fand is of no value as a manure; so that he who voluntarily purchases this kind of lime in preference to the other, is guilty of a great degree of folly; which will be the greater, if he has likewife to drive it from a confiderable diftance. It would be better for him, if he is determined to ule nothing but weighty lime, to buy fuch as is pure, if it can be obtained, and mix it with and after he has got it home, fo as to give it the gravity required. Some might laugh at this as a proof of his folly; and july Lut it is furely lefs foolish in him to do this than to pay money

for

for the fand, which he would. thus obtain for nothing, and drive it from a distance, when he might have it at his door. This practice would alfo be attended with the further advantage, of enabling him to know exactly what quantity of real lime he applied to his ground, as he would not be in danger of confidering the fand as a part of it.

Those who have accefs to only one fort of lime-ftone must be contented with it, what

4

ever may be its quality. But, fuch as have an opportunity of chufing, may be benefited by the followi g obfervations:

Pure lime-ttone, when fully calcined and flaked, is reduced to a fine impalpable pow÷ der, that feels foft between the fingers, without the smallest tendency to grittiness. -Such

Such lime as contains fand, is never fo fine nor so soft, but feels gritty between the fingers; and is more or lefs fo, as the fand is coarfer, or finer, or in greater or smaller proportions.

The lime from pure lime-ftone is always of a bright white, when perfectly calcined, without a tendency to any colour.—When it has any colour, it proceeds from the fand in its compofition. There are, however, some forts of fand that are of fuch a pure whitenefs as not to debafe the colour of the lime in the smallest degree; but these are

rare.

Hence it follows, that the beft lime for the purpose of the farmer is that which is lighteft, fofteft to the touch, and whiteft. -The more they deviate from either of these tests of purity, the worfe they are for him.

$ 12.

That the farmer may have under his eye at one time the several criteria of the purity of lime that have been enumerated in different places of this Effay, I chufe to mention them here all at one time.-If he is attentive to remark thefe peculiarities, he needs, be very little follicitous about examining the qualities of his lime by any more minute. and troublesome trials.-They are as under :

If the lime-ftone lofes much of its weight in calcination, and the lime-fhells are extremely light; if the fhells require a very large proportion of water to flake them fully; if it is long before they begin to fall if the lime-ftone is not apt to run (or be vitrified) in the operation of burning ;-if it, falls entirely when it gets a fufficient quantity of water after it has been properly calci

ned;