324 EFFECTS OF CLAY AND MARL. 



soil by an admixture of clay, and openness and porosity to stiff' clays by 

 the addition of sand. 



Th^ first and obvious effect of such additions is to alter the physical 

 qualities of the soil — to consolidate the peats and sands, and to loosen 

 the clays. But we have already seen that the fertility of a soil, or its 

 power of producing a profitable return of this or that crop, depends in 

 the first place on its chemical constitution. It must contain in sufficient 

 abundance all the inorganic substances which that crop requires for 

 its daily food. Where this is already the case, as in a rich stiff" clay, a 

 decided improvement may be produced by an admixture with siliceous 

 sand, which merely separates the particles mechanically, and renders 

 the whole more porous. But let the clay be deficient in some necessary 

 constituent of a fertile soil, and such an addition of siliceous sand would 

 not produce by any means an equal benefit. It may be proper to add 

 this sand with the view of producing the mere physical alteration, but 

 we must add some other substance also for the purpose of producing the 

 necessary chemical change. 



The good eflfects which almost invariably follow from the addition of 

 clay to peaty or sandy soils are due to the production at one and the same 

 time of a physical and of a chemical change. They are not only ren- 

 dered firmer or more solid by the admixture of clay, but they derive 

 from this clay at the same time some of those mineral substances which 

 they previously contained in less abundance. 



The addition of marl to the land acts often in a similar two-fold capa- 

 city. It renders clay lands more open and friable, and to all soils brings 

 an addition of carbonate, and generally of phosphate of lime, both of 

 which are proved by experience to be not only very influential, but to be 

 absolutely necessary to healthy vegetation. 



That much benefit to the land would in many instances accrue from 

 such simple admixtures as those above adverted to, where the means 

 are available, will be readily granted. The only question on the sub- 

 ject that ought to arise in the mind of a prudent man, is that which is 

 connected with the economy of the case. Is this the most profitable way 

 in which I can spend my money ? Can I employ the spare labour of 

 my men and horses in any other way which will yield me a larger 

 return ? It is obvious that tlie answer to these questions will be modi- 

 fied by the circumstances of the district in which he lives. It may be 

 more profitable to drain, — or labour may be in great request and at a 

 high premium, — or a larger return may be obtained by the investment 

 of money in purchasing new than in improving old lands. It is quite 

 true that the country at large is no gainer by the mere transfer of land 

 from the hands of A to those of B, and that he is undoubtedly the most 

 meritorious citizen who, by expending his money in improving the soil, 

 virtually adds to the breadth of the land, in causing it to yield a larger 

 produce. Yet it is no less true that the employment of individual capi- 

 tal in such improvement is not to be expected generally to take place, 

 unless it be made to appear that such an investment is likely to be as 

 profitable as any other within the reach of its possessor. It seems to be 

 established beyond a doubt, that in very many districts no money is more 

 profitably invested, or yields a quicker return, than that which is ex- 

 pended in draining and subsoiling — and yet in reality one main obstacle 



