THli FAKMEK'S MAGAZINE. 



213 



pend on vaiious changing circumstances. Besides the 

 quantity and quality of the substances, much influence 

 is exerted by temperature, by electricity, and by mecha- 

 nical pressure, by insolubility, and by other causes 

 arising from peculiar circumstances. 



The compost manure that has now been described, 

 being a cool mass, will be best used in cool weather, 

 when the solubility will not be too much hastened by 

 violent heats, nor be retarded by the pinching colds. A 

 gradual decomposition will best answer the purpose of 

 the assimilation of the elements to the condition of the 

 food of plants. 



The value is very great of earthy composts prepared 

 in tliis way, for being used as top-dressings on grass- 

 lands of all kinds, and also on fallow lands. Not only 

 the common herbage is increased in one-third of the 

 average pioduce, but the quality is very much improved 

 by the invariable result of grass-plants of a better kind 

 being brought forward, and established on the ground. 

 It is a very beneficial praciice to sow the seeds of the 

 better grasses on the top of a liberal application of a 

 rich earthy compost, to harrow the surface, and then to 

 press the seeds firmly into the ground by means of a 

 heavy roll. Inferior grass-lands are very much im- 

 proved in this way, and at a very moderate cost in the 

 purchase of the lime and the price of the grass-seeds. 

 In every case of application, the compost of lime and 

 earth is much superior in eft'ect to lime by itself, espe- 

 cially on lands of an inferior quality. This fact has 

 been settled beyond all dispute, and arises from the 

 earth of the compost imbibing and retaining the caloric 

 imparted by the lime, by which the future crops are 

 more binefited than by the weak soil that is devoid of 

 the quality of using caloric. Lime, in any condition, 

 only raises the temperature of the ground in the form 

 of benefit from its use. 



The burning of clay for the purpose of being con- 

 verted into a manure has been often tried with much 

 vaunting confidence. By the application of a smother- 

 ing fire the earths are divided and reduced into very fine 

 particles, and invested with an unknown property, 

 which substances acquire that have undergone the ac- 

 tion of fire. In this state it is supposed to attract and 

 retain ammonia, that is conveyed to the soil by rain- 

 water, and thus aflTords to plants the nitrogen contained 

 in the ammonia or volatile alkali. Clay is the oxide of 

 " aluminum," one of the newly discovered terrigenous 

 metals, and is composed of silica, alumina, oxide of 

 iron, and some little inflammable matter; and proba- 

 bly some other substances, but in a very minute ratio. 

 The combination of alumina with the oxide of iron pro- 

 duces the well-known earthy smell of clays. An 

 oxide is heavier than the primitive body, by reason of 

 the quantity of oxygen which has been absorbed. The 

 action of fire on clay will oxidize the residual calces 

 that compose it, and must contain none of the elements 

 of vegetation — a property which belongs to all bodies 

 that exist in that state. Very much, if not the whole, 

 value will consist in the composition of the clay itself ; 

 and when it is taken from the surface of the ground 

 will contain both animal and vegetable matters, and the 

 ashes will be of the usual nature after burning. The 

 practice of burning clay by itself has wholly sunk in 

 repute, as it never had any legitimate existence on 

 scientific grounds. A metallic base that has been 

 divested of every other ingredient can form no fertiliz- 

 ing substance, and the preparation adds very considera- 

 bly to the lessening of its value. On the other hand, 

 alumina has a very strong affinity for lime, and hence 

 tlie very beneficial results that attend the reciprocal 

 action, and which arise from the union of the com- 

 bination. 



On ths subject of using clay it may be added, that 



the clods of clay-land fallows may be very advantage- 

 ously pulverized by being laid in heaps, and mixed with 

 the cinders of hot lime, and which are dissolved by ex- 

 posure, or by the application of water. The damp heat 

 evolved by the lime will produce a smothering effect on 

 the clay, penetrate the viscid mass, and impart a fertil- 

 izing property to the mixed substances. The lime and 

 the clay will be pulverized together, and most minutely 

 blended, and mixed in a manner that is otherwise im- 

 jiossible. This mode of using clay has been seldom 

 noticed ; but of the value of the application no doubt 

 can be entertained. 



Clay has been laid on longitudinal heaps of hot dis- 

 solving lime, and it is benefited by the penetration of 

 the damp vapours from the bursting of the cinders • it 

 is afterwards removed, and used as a manure. Little, 

 certainly, is known of this method of using lime. The 

 quantity of lime must be very considerable, in order to 

 pierce and crumble a tough mass by means of damp ex- 

 halations. The duration may be doubted of the fertil- 

 izing quality that is communicated to the clay by the 

 volatile elements of the caustic lime. 



In mixing clays with lime, in order to form the com- 

 post as now recommended, the special attention must 

 be directed to the placing the clay and lime together in 

 the hottest possible state after the lime has been burned. 

 The dissolution of the cinders by the efi'ect of moisture 

 evolves much heat, which penetrates and crumbles the 

 tough harshness of the aluminous mass, and re- 

 duces it to the condition of being combined in a 

 milder and more useful form. If the lime be 

 allowed to lie exposed, and becomes mild, it 

 loses the character of a caustic solvent, and assumes the 

 state of an earthy ingredient. In this form, it does not 

 act on other bodies, and enters only into a mechanical 

 mixture with substances that are pulverized in a similar 

 state. The clay is usually in the form of clods and 

 lumps, and requires a powerful solvent, in order to dis- 

 integrate the mass and sunder the particles. If this re- 

 duction be not effected, the lime merely adheres to the 

 outside of the clods : no combinations are effected, and 

 no results are produced by the union of the different 

 bodies. It is an object of the very last importance that 

 the ultimate elements of bodies are brought into contact 

 at insensible distances. The surface of one body being 

 presented to the aggregated mass of another substance, 

 affords no opportunity of reciprocal action : the distance 

 is much too great ; and the efficacy of combination is 

 in the inverse ratio of the affinity of aggregation ; and 

 the greater the latter power is, the less efficacious will 

 be the power of composition. Hence pulverized lime, 

 being brought into contact with lumps of clay, can 

 exert no useful influence, and merely gilds the clods 

 with a whiter varnish than they before possessed. This 

 principle is equally applicable to the use of lime on 

 rough clay fallows. The lime is in fine particles, and 

 the land in large pieces ; and, consequently, no recipro- 

 cal action can happen. The lime is powerless from want 

 of opportunity, and the soil is formed into masses which 

 admit no influence of exterior action. Hence it would 

 answer a very beneficial purpose to form heaps of the 

 clods of clay fallows, mixed with lime-cinders, which, 

 by bursting and evolving much beat, would penetrate, 

 crumble, and pulverize the clayey lumps, and reduce 

 them to ashes, and mix with the granulated particles of 

 the lime in the most extreme comminution. Peat may 

 also be reduced to ashes by the hot cinders of lime ; and 

 during the process, some useful combinations may hap- 

 pen between the lime, the clay, and the moss. Bodies 

 that undergo, in conjunction, the powerful influence of 

 fire, will have a better opportunity of forming new 

 states of existence, than when brought into contact after 

 the action has ceased, and the mutual change of condi- 



