On the Theory of Manures. 3 



the coal measures ; and the varieties produced by the mixture of 

 these are immense. 



One end of the seedling beds, along a whole quarter of the 

 garden, may be of a loose friable, though loamy, nature, suiting 

 most seasons well; Avhile the other end of the beds may be 

 found of a stiff retentive nature, which hardly any season is 

 found to suit, yielding scarcely any crop in comparison, though 

 covered with double the quantity both of manure and seed ; yet 

 at times, by the agency of frost, with dry digging and pulverising, 

 these same ends may, in some seasons, be nearly equal to the 

 other. Many districts also, from the prevalence of moor land, 

 and the want of plantations to shelter, are much colder than 

 others in the neighbourhood more favourably situated. Some 

 hills sloj)e to the south, and others to the north ; some abound 

 in inequalities, while in others the slope is regular. Fields, and 

 pieces of fields, and gardens will also diifer much, as to the quan- 

 tity of organic remains left from previous crops, or deposited 

 from the roots, or accumulated by accident. The mechanical 

 state will also diifer much, from portions being dug for the 

 previous crop in wet or in dry weather, from trenching, 

 draining, &c. 



When so many causes are at work, which may all at times 

 affect the results of experiments, we must not be discouraged 

 though we do not get exact comparative results from measured 

 portions of soils and manures ; and be content, if, from a great 

 variety of experiments carefully observed in all their bearings, 

 on various soils, in various pieces of the same field or garden, 

 and in various seasons and circumstances, the truth should after 

 all begin to emerge. If these experiments give rise to theo- 

 retical opinions for which the reasons seem well grounded, and 

 if these theoretical opinions are confirmed by future practice, 

 a solid basis may be built, by the united aid of science and 

 practice, which neither the one nor the other could, of itself, 

 have so perfectly attained. The subject must be tho- 

 roughly investigated in all its bearings ; and, however many 

 deceive themselves or succeed in deceiving others, it can only 

 be for a time. Practice will banish false theories and establish 

 the truth, if properly and unprejudicedly observed. We must 

 not be hasty in our conclusions, and must take proper observation 

 of the soils experimented on, the circumstances they are placed 

 in, the nature of the seasons, and how all these bear on one 

 another, and may be calculated to affect or be affected by the 

 substances deposited as manures. When practical men, gene- 

 rally, get so far versed in the elements of science as to enable 

 them to follow out all these subjects in all their bearings, an 

 immense power of observation will be brought into action, 

 and must ultimately be productive of vast benefit. 



B 2 



