AGRICULTURAL TEXT-BOOK. 333 



ally takes from the land. The best Michigan marls will proba 

 bly be found much richer than the above and here is the very 

 substance in which our oldest wheat lands are beginning to be 

 deficient, (See Genesee Farmer, August, 1853J and yet it is 

 allowed to lie neglected and despised in almost every marsh and 

 lake. Marls may be applied in two modes, (a,) burned as lime, 

 in which respect they do not much differ in effect from the best 

 agricultural lime rocks ; (b,) in the natural state, but dried so as 

 to powder. Like lime they produce a mechanical and chemi 

 cal effect; the first differing with the soils and the character of 

 the marl. The chemical effect consists in actually rendering 

 the soil productive of larger crops. The exact mode of acting 

 does not appear to be well understood. The observed effects of 

 marl and shell sand, in so far as they are chemical, are chiefly 

 the following : They alter the nature and quality of the grasses 

 when applied to pasture ; they cover even the undrained bog r 

 with a short rich grass they extirpate coarse grasses and moss, 

 and the weeds which infest unlimed wheat fields ; they increase the 

 quality and enable the land to grow a better quantity of wheat; 

 they manifest a continued action for many years after they have 

 been applied ; like the purer limes, they act more energetically if 

 aided by the occasional addition of other manure; and like 

 them they finally exhaust a soil from which successive crops are 

 reaped, without the requisite return of decaying animal or veg 

 etable matter. (Johnston.) 



In practice it is probably best to dig the marl, and leave it to dry and 

 disintegrate for some months before applying. One ton and upwards 

 may be applied to the acre, and plowed in shallow at the last plowing, 

 or worked in with the cultivator. To act effectually, lime must be kept 

 near the surface, and its constant effort is to sink below the reach of 

 roots. 



706. SALT is chemically composed of the metal sodium, and 

 the gas chlorine, chloride of sodium, or called by the older 

 chemists muriate of soda. It is procured by evaporating the 



