88 
THE CULTIVATOR. 
pared to lift up either harrow when choked by weeds, or otherwise 
interrupted. 
The method of attaching the animals of draught will be explain¬ 
ed by the apparatus of swing-trees, shown in the figure, by means 
of which each animal must exert an equal foree in pulling. There 
are plates of iron, N, N, passing through the left-hand bars of 
each harrow. These plates have a few holes in them, so that the 
line of draught may be shifted to the right or left as may be re¬ 
quired. The staple P upon the swing-tree RR, being the point to 
which the moving power of the harrow is attached, it is important 
to ascertain its proper position. 
Were a perpendicular to be let fall from the staple P upon the 
line LM, the point of intersection would be in the middle of the 
entile breadth covered by the harrows, and an equal number of 
teeth would be on each side of the line of traction, and this would 
seem to indicate the position of the staple P. But the larger bars 
being placed oblique to the line of the harrow’s motion, when any 
obstacle raised above the surface of the ground strikes one of these 
bars, it tends to press it to the right hand side. And as there are 
eight bars of this kind, and these of considerable length, it will 
appear that, in ground where there is any great unevenness of 
surface, there will be a constant succession of strokes, forming a 
strong lateral pressure on the left side of the several bars. But 
the staple P being nearly fixed in its position, while the harrows 
may be moved round, the effect of this lateral pressure is to turn 
the whole harrows on P as a pivot from left to right. In practice, 
accordingly, there is found to be a constant tendency in the har¬ 
rows of this construction to swing around from left to right, and 
this often to so great a degree in verv rough ground, as to place 
the larger bars parallel to the line of motion, thus causing all the 
teeth in the same bar to follow in the same track. Hence the point 
P ought not to be precisely in the middle of the space covered by 
the harrows, but placed somewhat to the left hand, in order that 
so great a number of teeth may be placed on the right side of the 
line of traction as to counteract the tendency of the harrows to turn 
from left to right. But further, the position of T is not fixed, 
but must vary with the roughness of the surface over which the 
harrows are dragged. Hence not only must the staple P be placed 
somewhat to the left hand, but there must be the power of mov¬ 
ing it more or less towards the left hand, according to the rough¬ 
ness of the surface passed over. This is effected by the iron plates, 
with holes, of which menfion has been made, and by means of 
which the driver can readily shift the line of draught more or less 
to the left hand, as may be required. 
From Ruffin's Essay on Calcareous Manures. 
OBSERVATIONS ON MARL AND LIME. 
The theory of the constitution of fertile and barren soils, has now been 
regularly discussed; it remains to show its practical application, in the use 
of calcareous earth as a manure. If the opinions which have been main¬ 
tained are unsound, the attempt to reduce them to practice will surely ex¬ 
pose their futility; and if they pass through that trial, agreeing with, and 
confirmed by facts, their truth and value must stand unquestioned. The 
belief in the most important of these opinions, (the incapacity of poor soils 
for improvement, and its cause;) directed the commencement of my use 
of calcareous manures; and the manner of my practice has also been di¬ 
rected entirely by the views which have been exhibited. Yet in every 
respect the results of practice have sustained the theory of the action of 
calcareous manures—unless there be found an exception in the damage 
which has been caused by applying too heavy dressings to weak lands. 
My use of calcareous earth as manure, has been almost entirely con¬ 
fined to that form of it which is so abundant in the neighborhood of our 
tide-waters—the beds of fossil shells, together with the earth with which 
they are found mixed. The shells are in various states— in some beds ge¬ 
nerally whole, and in others, reduced nearly to a coarse powder. The 
earth which fills their vacancies, and serves to make the whole a compact 
mass, in most cases is principally siiicious sand, and contains no putres¬ 
cent or valuable matter, other than the calcareous. The same effects 
might be expected from calcareous earth in any other form, whether chalk, 
limestone, gravel, wood-ashes orlime—though the two last have other qua¬ 
lities besides the calcareous. During the short time that lime can remain 
quick or caustic, after being applied as manure, it exerts, (as belore stat¬ 
ed,) a solvent power, sometimes beneficial and at others hurtful, which has 
no connexion with its subsequent and permanent action as calcareous earth. 
These natural deposites of fossil shells are commonly, but very impro¬ 
perly, called marl. This misapplied term is particularly objectionable, 
because it induces erroneous views of this manure. Other earthy ma¬ 
nures have long been used in England, under the name of marl, and nu¬ 
merous publications have described their general effects, and recommend¬ 
ed their use. When the same name is given here to a different manure, 
many persons will consider both operations as similar, and perhaps may 
refer to English authorities foi the purpose of testing the truth of my opi¬ 
nions, and the results of my practice. But no two operations called by 
the same name can well differ more. The process which it is my object to 
recommend, is simply the application of calcareous earth in any form 
whatever, to soils wanting that ingredient, and generally quite destitute 
of it; and the propriety of the application depends entirely on our know¬ 
ing that the manure contains calcareous earth, and what proportion, and 
that the soil contains none. In England, the most scientific agricultur¬ 
ists apply the term marl correctly to a calcareous clay, of peculiar tex¬ 
ture; but most authors as well as mere cultivators, have used it for any 
smooth soapy clay, which may, or may not have contained, so far a3 they 
knew, any proportion of calcareous matter. Indeed, in most cases, they 
seem unconscious of the presence, as well as of the importance of that in¬ 
gredient, by not alluding to it when attempting most carefully to point out 
the characters by which marl may be known. Still less do they inquire 
into the deficiency of calcareous earth, in soils proposed to be marled— 
but apply any earths which cither science or ignorance may have called 
marl, to any soils within a convenient distance—and rely upon the subse¬ 
quent effects to direct whether the operation shall be continued or aban¬ 
doned. Authors of the highest character, (as Sinclair and Young, for ex¬ 
ample,) when telling of the practical use, and valuable effects of marl, 
omit giving the strength of the manure, and generally even its nature— 
and in no instance have I found the ingredients of the soil stated, so that 
the reader might learn what kind of operation really was described, or be en¬ 
abled to form ajudgmentof its propriety. From all this, it follows that though 
what is called marling, in England, may sometimes (though very rarely, 
I infer,) be the same chemical operation on the soil that I am recommend¬ 
ing, yet it may also be, either applying clay to sand, or clay to chalk, or 
true marl to either of those soils—and the reader will generally be left to 
guess in every separate case, which of ail these operations is meant by the 
term marling. For these reasons, the practical knowledge to be gathered 
from all this mass of written instruction on marling, will be far less abund¬ 
ant, than the inevitable errors and mistakes The recommendations of 
marl by English authors, induced me very early to look to what was here 
called by the same name, as a means for improvement: but their descrip¬ 
tions of the manure convinced me that our mail was nothing like theirs, 
and thus actually deterred me from using it, until other views instructed 
me that its value did not depend on its having “ a soapy feel,” or on any 
mixture of clay whatever. 
Nevertheless, much valuable information may be obtained from these 
same works, on calcareous manure, or on marl, (in the sense it is used 
among us) but under a different head, viz. lime. This manure is gene¬ 
rally treated of with as little clearness or correctness, as is done with marl: 
but the reader at least cannot be mistaken in this, that the ultimate effect 
of every application of lime, must be to make the soil more calcareous— 
and to that cause solely are to be imputed all the long continued beneficial 
consequences, and great profits, which have been derived from liming. 
But excepting this one point, in which we cannot be misled by ignorance, 
or want of precision, the mass of writings on lime, as well as on calcare¬ 
ous manures in general, will need much silting to yield instruction. The 
opinions published on the operation of lime, are so many, so various and 
contradictory, that it seems as if each author had hazarded a guess, and 
added it to a compilation of those of all who had preceded him. For a 
reader of these publications to be able to reject all that is erroneous in rea¬ 
soning, and in statements of facts—or inapplicable on account of difference 
of soil or other circumstances—and thus obtain only what is true and va¬ 
luable—it would be necessary for him first to understand the subject better 
than most of those whose opinions he was studying. It was not possible 
for them to be correct, when treating (as most do) of lime, as one kind of 
manure, and every different form of the carbonate of lime, as so many 
others. Only one distinction of this kind (as to operation and effects) 
should be made and never lost sight of—and that is one of substance, still 
more than of name. Pure or quicklime, and carbonate of lime, are ma¬ 
nures entirely different in their powers and effects. But it should be re¬ 
membered that the substance which was pure lime when just burned, of¬ 
ten becomes carbonate of lime before it is used, (by absorbing carbonic acid 
from the atmosphere,)—still more frequently before a crop is planted— 
and probably always, before the first crop ripens. Thus, it should be 
borne in mind that the manure spoken of as lime, is often at first, and al¬ 
ways at a later period, neither more nor less than calcareous earth: that 
lime which at different periods is two distinct kinds of manure, is consi¬ 
dered in agricultural treatises as only one: and to calcareous earth are given 
as many different names, all considered to have different values and ef¬ 
fects, as there are different forms and mixtures of the substances present¬ 
ed by nature. 
But however incorrect and inconvenient the term marl may be, custom 
has too strongly fixed its application for any proposed change to be adopt¬ 
ed. Therefore, I must submit to use the word marl to mean beds of fos¬ 
sil shells, notwithstanding my protest against the propriety of its being so 
applied. 
