HUSBANDRY. sm 
probable that much depends on the date and manner of 
its being put in or upon lands, and that it is only where 
it is; laid on in a moderate fuitable proportion, and after 
it has been well broken, down and reduced into a. fine 
powdery, form, fours that it may be very minutely and 
intimate!-' blended with the foil, that its belt eHeels can 
be exerted. 
Dr., Hunter has an elaborate effay .on the nature and 
properties of marl. From his analy.fis and experiments 
it appears,- that marl confifts of clay, or a mixture of clay 
and land,; and. of: a real calcareor s.earth, differing in no 
rel'pedl from that, of limeftone and the (hells of animals. 
According to’him, the. effence of marl.confifts. in this 
calcareous earth. All bodies however which have calca¬ 
reous earth: are .not marl. To entitle them to this name, 
they mull tail into powder upon being expofed. to the air. 
Hence the purity of marls will be in proportion to the 
quantity of calcareous earth.in their compofition. 
The different proportions, of the conftituent parts of 
marl in the fev.eral varieties of it, making a choice of 
marls for particular foils a matter of confequence; it 
is definable to know the procefs for difeovering this pro¬ 
portion. Having dried and powdered the marl to be ex¬ 
amined, pour upon any given weight of it a fmall quan¬ 
tity of water. To this mixture well fhaken add a little 
acid of fea-falt-, or any other mineral acid, except the vi¬ 
triolic; and, when the effervefcence is over, add a little 
more. Repeat this addition at proper intervals, till no 
more effervefcence enfues. Then.,put the whole, with an 
equal or greater proportion of water, into a filter of'grey 
paper, the weight of which is known. When all the 
fluid parts have palled through, fill up the filter again 
and ao-ain with warm water. Thus the diffolved parti¬ 
cles of calcareous earth, adhering to the refidue, or en¬ 
tangled in the pores of the paper, will be waflied away, 
and nothing but what is really infoluble will remain in 
the filter. This refidue, with the filter be dried and 
then weighed. The difference between its weight and 
the original weight of the filter, gives the weight of info¬ 
luble parts. This being known, the proportion of calca¬ 
reous earth in the fame marl is evident. The propor¬ 
tions of clay and fand in it are difeovered by fubjefling 
the refidue to a proper elutriation or wafhing, which is 
thus performed s Having weighed the dry refidue, mix 
and fhake it well with a fufficient quantity of water. 
After allowing a lirtle time for the fubfiding of the grof- 
fer parts, let the water, with the fined particles of clay 
fufpended in it, be gently poured off. Add more wa- 
ter to the remainder, and, after fufficient mixture and 
iubfidence, pour that off likewife. In the fame manner 
reneat the operation again and again till the w'ater comes 
off perfectly pure. The fubflance which then remains is 
fand, mixed perhaps with fome flakes of talc ; and what¬ 
ever this fubflance wants of the weight of the refidue, is 
the weight of pure clay, carried away by the water in 
the wafhing. -The effervefcence enfuing upon the appli¬ 
cation of acids to marl, although it fhows the exiftence 
of calcareous earth, yet is no indication of the quantity 
of it; for the effervefcence varies according to the flrength 
of the acid employed; but flill more according to the pe¬ 
netrability and other more latent qualities of calcareous 
bodies. 
The calcareous earth of marl is equally calculable to 
quicklime, whether it is expofed to the aftion of fire be¬ 
fore or after its reparation from-the other earths which it 
contains. Marl indeed has a very intimate affinity to 
limeftone. A gentle gradation from one to the other 
may be eafily traced out ; and it will be difficult to eljta- 
blifh the prerife limits of either. Both are found in con¬ 
tinued flrata ;. both diffolve in part with confiderable ef- 
fervefcence in acids, and-both yield by calcination a 
quicklime. There are however two remarkable differ¬ 
ences : marl, by being expofed to air, falls into powder; 
Jimeflone retains its original liability. On the contrary, 
limeflone, after undergoing the a&ion of fire, is reduced 
Vol.X. No. 6S5. 
to powder by the application of water; marl fuffers no 
change, 
The expence'of marl, at fome places is very great. 
About Yarmouth, in Norfolk, it is-74. 4 -d. a-cart-load. 
About Colchefler they have it from Kent; it coils them 
from 7s. to 9s, a waggon-load, they carry it ten miles, and 
lay feven waggon-loads on an acre. 
Marl has been much ufed in' Staffordfhire for ages 
back. In many places, they fay; the land has been over- 
marled, and ij rendered har!h ;. this, is reftored by fallow¬ 
ing and liming. It is in general only in loamy foils that 
a true marl is found ; in mixed-gravelly foils they have 
a friable brick- clay, which is ufed on filch foils with 
good efl'edl; the quantity laid-on is generally one hun¬ 
dred and twenty-eight cubic yards on an acre, which 
adds.nearly an inch-to the ftaple of- the foil; the expence 
is about 25s. an acre, befides carting- out, which is worth 
50s. an acre more. It is thought to" be much more 
adapted 'to tillage than pafture, and its; goodeft'edts on 
corn-lands are long vifible; in thin light lands it endures- 
for ever, as it not only confolidates the foil, but gives it 
ftaple. 
Marl is the foundation of improvements in agriculture 
in Lancafhire and Chefhire. TheyJiave' feverai varieties 
of it, valuable in proportion to the calcareous matter 
which they contain, or the nature of the foil to which 
they are to be applied. To ftiff clay-lands the blue or 
reddilh flate-mari, or {hell-marl, containing much calca¬ 
reous earth with fome fluid, are more beneficial; but to 
light lands ftrong clay-marl is more genial. 
Barren fluids and poor heaths have been rendered pro¬ 
ductive by marl, but at a great expence ; indeed there is 
reafon to believe that the greateft part of the fouthern.- 
diftrict of Lancafhire has been reclaimed by it. 
The general cultom is to lay upon the great Chefhire 
acre of eight yards to the rood, from three to feven roods 
of fixty-four fquare yards each. From four to five roods 
may be confidered as the average quantity ; but it ought 
to be in proportion to the quality of the foil and of thd 
marl. -A Chefhire acre contains two acres eighteen 
perches and a half ftatute meafure. They lay it upon 
grafs-land which is intended to be broken-up the enfu-" 
ing fpring. Sometimes a coat of marl is fpread upon the 
green-fward, and left, unploughed many years ; in this 
cafe the grafs fometimes receives confiderable detriment, 
the marl (inking down in a body without incorporating 
with the foil; though, when marl has lain feveral years in 
this ftate, the lublequent crops of corn have been enor¬ 
mous. 
Mr. Macro, of Barrow, in Suffolk, is convinced, that 
about feventy fquare yards or loads of marl is the pro- 
pereft quantity to be laid on an acre, pole meafure. If 
more be laid on, it will be longer before it incorporates 
with-the foil, and therefore before any benefit can be re T 
ceived from it. The effefl however of a larger quantity 
will continue longer. 
In open fields marling feldom anfwers the expence, for- 
this is only a beginning of improvement; by going on 
diredtly with a courfe of ploughing, which cannot well 
be avoided in fhiftable fields, the marl is often buried- and 
loft before it mixes properly with the foil, efpecially if 
turned in too deep the firft- earth, of which great care 
fhould be taken. Marling therefore, can only or clfiefiy 
anfwer on inclofed land, that can be managed as thgi-oc- 
cupier pleafes. In that cafe, it fhould be laid dowfe with 
clover, ray-grafs, and trefoil, the fpring .twelvemonth be¬ 
fore laying on the marl, and remain at lead fix months 
after, that it may have time to fink' into the flag before 
it is ploughed up, and then there will be little danger of ■ 
lofing it, as it will be in fome meafure incorporated with 
the foil. No pains fhould be fpared to break all the 
lumps, and to get it fine by repeated harrowings and roll¬ 
ings, and to have the Hones picked and carried away, 
that the grafs may get through, for flock to be grazing 
upOu it, which is the great and fimlhing improvement. 
7 F Let 
