208 THE COMPLETE FARMER 



and gradually thrown into the flask, until, after repeated ad- 

 ditions, no farther effervescence is perceived. Let the re- 

 mainder of the powdered marl be weighed, by which the 

 quantity projected will be known. Let the balance be then 

 restored. The difference of weight between the quantity 

 projected and that requisite to restore the balance, will show 

 the weight of air lost during effervescence. [That air pro- 

 ceeds from the calcareous earth alone, which contnins forty- 

 four per cent, of this carbonic acid air. Suppose five hundred 

 grains of marl lose forty-four grains by the escape of air, 

 then that marl contained one hundred grains, or one-fifth of 

 its whole weight, of limestone. — T. C] If the loss amount 

 to twenty or twenty-five per cent, of the quantity of marl 

 projected, the marl assayed is calareous marl, or marl rich 

 in calcareous earth. Clayey marls, or those in which the 

 argillaceous ingredient prevails, lose only eight or ten per 

 cent, of their weight by this treatment, and sandy marls 

 about the same proportion. The presence of much argilla- 

 ceous earth may be judged by drying the marl, after being 

 washed with spirit of salt, when it will harden and form a 

 brick. 



'To determine with still greater precision the quantity of 

 calcareous earth in marl, let the solution in muriatic acid 

 be filtered and mixed with a solution of carbonate of potash, 

 till no farther precipitation appear. Let the sediment sub- 

 side ; wash it well with water ; lay it on a filter, previously 

 weighed, and dry it. The weight of the dry mass will show 

 how much carbonate of lime the quantity of marl submit- 

 ted to experiment contained. See Kirwan on Manures. 



' The quantity necessary to be used, varies according to 

 the nature of the soil ; but the utmost caution is requisite, 

 because if too large a portion be scattered on the land, it 

 cannot be easily removed, and if too little be employed, the 

 deficiency may be readily supplied. On sandy, gravelly, or 

 light soils, it will be advisable to spread os much as will 

 form a thick coat, in order to bind and stiffen the ground. 

 But, of whatever nature the land may be, the most judicious 

 cultivators recommend such a portion to be laid on it, as will 

 form a thin coat over the whole surface. 



' The proper season for marling is the summer ; as this 

 kind of manure is then perfectly dry, and not only lighter, 

 but also more easily reduced to a powder. Marl, however, 

 may be advantageously spread during the winter frosts ; as 



