MAUL. 909 



Bhortly after it is dug from the bed that supplies it ; the practice 

 where its employment is most general, and proliably best understood, 

 is to let it lie exposed through the summer or winter, or even the 

 whole year before laying it on the land. It is also held not to be 

 proper to cover it in marl deeply. Marl is advantageously laid out 

 in heaps upon stubbles in the autumn ; and in the early spring when 

 it has been pulverized by the frost, it is spread with the shovel. 

 When it is to be used with winter wheat or rye, it is laid on in the 

 sunmier, and spread at the time of ploughing; the latter plan of 

 proceeding, however, as Schwertz observes, can only be followed 

 with marl that pulverizes readily. In England it is also laid down 

 as a kind of principle that marl ought to be exposed for as long a 

 time as possible to the influences of the atmosphere ; that it ought 

 to have a sunmier's heat and a winter's cold before it is applied. 

 And that, in fact, which is at all consistent, and has not been expos- 

 ed to the frost, scarcely pulverizes sufficiently to be readily miscible 

 with the soil even under the influence of repeated ploughings ; more- 

 over, it produces very little obvious effect upon the crop with which 

 it is first used. After spreading, a rough harrow is passed over the 

 surface of the ground, which is then ploughed superficially two or 

 three times, the harrow being again had recourse to repeatedly to 

 break lumps, and so bring out the effect of the marl. 



The quantity of marl that may be advantageously given varies 

 according to the circumstances of the district. Marl, it may fairly 

 be said, is frequently abused. In an excellent paper on the subject, 

 M. Puvis lays it down as a principle that the first element in the 

 calculation of the proper dose of marl, is the quantity of calcareous 

 matter that is wanting in the soil. He says that every soil which 

 contains more than 9 or 10 per cent, of carbonate of lime can dis- 

 pense with marl ; and that soils in which the lime falls short of this 

 quantity, may advantageously receive a dose or successive doses of 

 the substance that will bring them up to the point. The proper 

 dose, consequently, depends first on the proportion of carbonate of 

 lime contained in the soil, and then on that which the marl itself 

 includes. 



Considered from the rational point of view which M. Puvis has 

 taken, marling is no longer an arbitrary process, but one that may 

 be conducted on determinate principles. The extravagant quanti- 

 ties that are often laid on without other assignable reason than blind 

 custom, are shown to be, if not injurious, yet useless : the quantity 

 of marl to be incorporated is determined by the quality of the sub- 

 stance which is at our disposal, and by the depth of the layer of 

 vegetable ea-th taken in connection with its chemical constitution. 

 To facilitate the calculation of the proper dose, M. Puvis has drawn 

 up a table, which, as it may be found useful in practice, I append. 

 It shows at a glance the quantity of marl in cubic feet that ought to 

 be put upon an acre of ground, the depth of the arable soil being 

 considered in connection wath the composition of the marl at com- 

 mand : — 



