CALCAREOUS MANURES— APPENDIX jgj 



NOTE III. — Extension of the subject of page 68. 



THE STATEMENTS OF BRITISH AUTHORS ON MARL, AND THEIR APPLICATIONS OP THE 

 NAME, GENERALLY INCORRECT AND CONTRADICTORY. 



Custom compels me to apply improperly the name marl to our deposites 

 of fossil shells. But as I have defined the manuring by this substance, which 

 is called marling, to be simply making a soil calcareous, or more so than it 

 was before, any term used for that operation would serve, if its meaning 

 was always kept in view. But this terra, unfortunately, is of old and fre- 

 ,quent use in English books, with very different meanings. The existence 

 of these diffei'ences and errors has been generally stated in the foregoing 

 pages of this essay, and I shall here present the proofs. The following 

 quotations will show that the term marl is frequently applied in Britain to 

 clays containing no known or certain proportion of calcareous earth — that 

 when calcareous earth is known to be contained, it is seldom relied on as 

 the most valuable part of the manure — and that in many cases the reader 

 is left in doubt whether the manure has served to increase, or diminish, or 

 has not altered materially the amount of the previous calcareous contents 

 of the soil. 



The passages quoted will exhibit so fully the striking contradictions and 

 ignorance generally prevailing as to the nature and operation of marl, that 

 it will scarcely be necessary for me to express dissent in every case, or to 

 point out the errors or uncertainty of facts, or of reasoning, which will ap- 

 pear so manifestly and abundantly. 



1. Kirwan, on the authority of Arthur Young and the Bath Memoirs, 

 [1783,] states that, 



" In some parts of England, where husbandry is successfully practised, any loose clay is 

 called marl : in others, 7)iarl is called chalk, and in others, clay is called loam." — Kirwan 

 on Manures, p. 4. 



2. The learned and practical Miller thus defines and describes marl, in 

 the Abridgment of the Gardener's Dictionary, fifth London edition, at the 

 article marl : 



" Marl is a kind of clay wliich is become fatter and of a more enriching quality, by a 

 better fermentation, and by its having lain so deep in the earth as not to have spent or 

 weakened its fertilizing quality by any product. Marls are of different qualities in dif- 

 ferent counties of England." 



He then names and describes ten varieties, most of them being very mi- 

 nutely and particularly characterized — and in only two of the ten is there 

 any allusion to a calcareous ingredient, and in these, it is evidently not 

 deemed to constitute their value as manures. These are " the cowshut 

 marl" of Cheshire, which — 



" Is of a brownish color, with blue veins in it, and little lumps of chalk or limestone,":^ 

 and " clay-marl ; this resembles clay, and is pretty near akin to it, but is fatter, and some- 

 times mixed with cbalk stones. 



" The properties of any sorts of marls, by which the goodness of them may be best 

 known, are better judged of by their purity and uncompoundedness, than their color : as 

 if it will break in pieces like dice, or into thin flakes, or is smooth like lead ore, and is 

 without a mixture of gravel or sand; if it will slake like slate-stones and shatter after 

 wet, or will tumble into dust, when it has been exposed to the sun ; or will not hang and 

 stick together when it is thoroughly dry, like tough cla)' ; but is fat and fender, and will 

 open the land it is laid on, and not bind ; it may be taken for granted that it will be be- 

 neficial to it." 



3. Johnson''s Dictionary (octavo edition) defines marl in precisely the 

 words of the first sentence of Miller, as quoted above. 



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