MANURES 39 



ot'lime. They are a useful application to land in consequence 

 of the lime they yield, and when containing the phosphate 

 in addition, their value is largely increased. The quantity 

 that may be advantageously used is even more variable 

 than that of pure lime, inasmuch as the quality varies with 

 every bed in which it is found. They are adapted to the 

 improvement of all soils, unless such as are already 

 sufficiently filled with lime, and they are more generally 

 useful to meadows than the pure carbonate. Their benefits 

 will be greatly enhanced if the clay marl be used on light or 

 sandy soils, and sandy marls on clay and heavy lands- 

 From 20 to 400 cart loads of marl per acre have been applied 

 according to its quality and the character of the land to be 

 benefitted. Circumstances must alone determine the proper 

 quantity to be used.* Marl should be carried out and 

 exposed in small heaps before spreading on the land. 

 Exposure to the sun and especially to the frosts of winter, is 

 necessiry to prepare it for use. 



SHELL SAND. 



This is a calcareous sand, sometimes mixed with animal 

 matter. It abounds on some parts of the coast of Cornwall, 

 and on the western shores of Scotland, and Ireland. It is also 

 found on the coast of France, and particularly in Brittany 

 where it is known by the name of trez. This produces 

 prodigious effects on peaty, clay and other soils, to which it is 

 applied at the rate of 10 to 15 tons per acre. It is so much 

 esteemed for the former, that it is sometfmes carried to .a 

 distance of 100 miles. It is probable there are similar 

 deposites on the coast of some of the Atlantic States, though 

 we are not aware of any such application for agricultural 

 objects. Its great value as a top dressing, will fully justify 

 exploration, for the purpose of detecting it wherever it may 

 exist. 



*Marls may be readily analyzed by any one with a pair of accurate scales and 

 weights, and a large mouthed vial. To" one part muriatic acid, add 2 parts water 

 and fill the vialto about one third, and balance it on.the scales. Then slowly 

 add 100 grains of the pulverized marl, thoroughly dried over the fire. When the 

 effervescence has subsided, expel the carbonic acid from the vial, by pouring it off, 

 blowing into the vial through a reed or with a bellows, its greater weight causing 

 it to retain its place to the exclusion of the air. Now add weights to the opposite 

 scale till balanced, and the deficiency of grains under 100, will show the amount of 

 carbonic acid expelled; and as this is combined in the proportion of 46 to 54 of 

 quick or pure lime, in every 100, the loss indicates 46 per cent of the carbonate of 

 lime contained in the marl. 



From the frequent presence of phosphate and sulphate of lime, and sometimes 

 potash and animali/.ed matters in marls, this kind of analysis seldom indicates tin.- 

 value of a marl bed for agricultural purposes. It its exact worth is to be ascertain- 

 ed, there must be a more perfect analysis by an experienced chemist. 



