H 367, 308, 369] limb in soils. 209 



Almost all plants require for their full development, more or less Soda, also. 

 But while the absence of available potash from a soil is one of the most common 

 causes of infertility, a sufficient amount of soda is rarely wanting. 



367. Calcium with oxygen, forms Lime ; the latter, in combination with 

 carbonic acid, constitutes marble, and the prevalent as well as the all-important 

 ingre lient of limestones, most of which are a mixture of carbonate ol lime with 

 earthy matters — sand, clay, etc. Most limestones contain magnesia, also, and a 

 great many contain small amounts of potash, soda and phosphoric acid. In the 

 process of burning lime, the carbonic acid of the carbonate of lime is expelled 

 by heat : in the hardening of common mortar, the lime partially resumes its 

 carbonic acid from the air. Hydraulic cement is burnt out of limestones con- 

 taining certain proportions of other earthy matters, or out ol an artificial 

 mixture of pure limestone and clay. 



Of phosphite of lime (being the chief ingredient of bones) and sulphate, of 

 lim a (being gypsum or plaster of Paris) I have spoken above i IToBf, olio). 



36S. Action of Lime in Soils. — Most plants require for their growth notable 

 quantities of lime, which must, therefore, be present in the soil. Few soils are 

 infertile for want of lime ; the increase of fertility observed a'ter liming, is 

 mostly due, not so much to the direct action of the lime itsell on plants, as to its 

 chemical action in rendering available to vegetation other ingredients, especially 

 potash and silica, when contained in the soil in a "locked up" condition (-557), 

 in the undecomposed part of the minerals.* Lime, especially when applied 

 freshly burnt, greatly accelerates the decomposition both of minerals and of 

 vegetable matter. Hence we see that by means of liming, we can in a brief 

 period of time, produce the same effects on the soil, which the unassisted action 

 of the atmosphere, or f. Mowing, would h»*ve required centuries to effect. 



36y But in so doing, we exhaust the soil very rapidly ; what we gain in the 

 fullness of crops, we lose in the duration of our land; hence the well-known 

 adage, that :< Lime enriches the father, but impoverishes the son." When land 

 whicli has been limed moderately, ceases to pioduce falovving will have liitle 

 effect on it for several years, because all the nutritive matter which was easily 

 accessible, has been already developed by the powerful action of the lime. Yet, 

 after fallowing for a number of years, such land may again become productive, 

 in consequence of the decomposing action of the atmosphere having at last- 

 penetrated to that portion of the soil which even the lime had not reached, and 

 thus made available a new supply of nourishing ingredients. Usually, however, 

 after a moderate dressing of lime has ceased to be effective, another and stronger 

 dressing is put on ; and thus the process of exhaustion may be continued, until 

 the soil becomes really and utterly exhausted — stripped completely, of all, or of 

 some, of the ingredients required by the plants. Henceforth, the crops will 

 depend entirely upon the application of manures — true manures (of which stable- 

 manure, or still better, night-soil, is the type), not mere stimulants, like lime, 

 ammoniacal salts, common salt, Chilian salipetre, elc. 



The use of lime on land to the extent above referred to, is scarcely better policy 

 than that of the drunkard, who, in order to sustain the excitement he desires, 

 finds it necessary to take deeper potations each succeeding day, until at la-t the 

 energies of life are completely exhausted, and the foundation gives way, before 



♦While there can be no doubt that the greater part of the favorable effects of 

 liming i- due to the indirect action ab jve referred to, experiments made upon 

 the growth of plants in lime water se in to show that lime also exercise- a kind 

 of direct stimulation on the vegetable functions, which in the experiments 

 mentione I, was manifested in the more vigorous development and deeper green 

 of the see dings vegetating in lime water, as compared with thjose placed in pure 

 water It may be doubted, however, whether the effects are in any manner 

 comparable tu those exercised by '•stimulants" upon the animal economy* 

 11— 14 



