THE FARMER'S MAGAZINE. 



115 



any of the earthy constituents. The insensible progress 

 of fermentation and the suction of vegetables im- 

 poverish it, and deprive it of organic remains, and leave 

 the metallic residue or earths, forming very poor soils, 

 and ochres where the ferruginous principle abounds. 

 The organic matter would seem destined to repair the 

 losses of the vegetable kingdom, and the earthy residue 

 that of the mineral ; for there we find diamonds, spars, 

 and gypsum, and similar productions. 



The pure earthy part of dung is very small, and, alter 

 a perfect putrefaction, bears an inconsiderable propor- 

 tion to the soil it was intended to manure. The great 

 use of soils seems to be in affording a bed to plants, in 

 which to fix the roots, and derive nourishment slowly 

 and gradually by the roots from the earth and from 

 atmospheric air. In order to account for the presence 

 of carbon in plants, it is supposed that vegetables de- 

 compose carbonic acid at the samt; time with water, 

 and absorbs its carbon ; but this supposition has not 

 been proved, though it has gained strength since the 

 decomposition of carbonic acid combined with soda by 

 moans of phosphorus has been discovered. Others are 

 of opinion that vegetables, earths, moulds, and water 

 of dunghills furnish the carbon attenuated and even 

 dissolved in water ; that plants absorb it, and do not 

 extract it from carbonic acid. According to this hypo- 

 thesis, manures afford only caibon, and the water is 

 nothing more than a saturated solution of this principle. 

 To these data the theory of vegetation is at present 

 restricted. 



Four earths have been found in plants — lime and 

 silica most abundantly, and magnesia and alumina in 

 much less quantities. All the alkalies have been found 

 in the fluids of animals : potash not very common ; 

 soda in all fluids combined with albumen; ammonia in 

 urine, and during its decomposition. And of the earths 

 are found lime, magnesia, and silica ; and of the metals, 

 iron in blood, and manganese in hair. None of the 

 earths are simple substances, and animals have a power 

 of forming them by the process of digestion. And it 

 seems very probable that plants have a power of forming 

 earths and other substances from their principles ab- 

 sorbed by the roots from the earth or from the atmos- 

 phere. Hence solution by chemical analysis of the con- 

 stituent parts of the organization of animals, and our 

 knowledge of the nature of the substances that com- 

 pose it, have not given any information in respect of the 

 food which should be supplied to them : they possess the 

 instinctive power of choosing and rejecting by smell and 

 taste, and thereby teach what articles are most agreeable 

 to them, and consequently most suitable for promoting 

 their growth. Any food they eat contains few or none 

 of the substances found in their constituent parts : they 

 must be formed during the process of digestion by many 

 unknown agencies and combinations ; and if an analogy 

 be drawn between animal and vegetable life, it may be 

 supposed that the food of plants differs as much as that 

 of animals from the constituent parts, and that the 

 latter are derived from the former by similar processess 

 and combinations. If an animal be restricted to one 

 kind of food, or to two, the growth of the solid parts 



of the body and the secretion of the fluids will go on 

 uninterrupted, and the animal will thrive and fatten. 

 The kinds of food contain none of the substances found 

 in llie animal org.mization ; and though some of the 

 minor parts may diircr something in quantity than if fed 

 on a greater variety of food, yet all the principal parts 

 are unaffected. Charcoal has been found the only fixed 

 ingredient in plants, and that substance has been sup- 

 plied to the roots without the least apparent advantage. 

 If it could be applied in the form accessible to the roots 

 of plants, it is not known that it would pass through 

 the elaborations and combinations in the plant, and 

 ultimately constitute charcoal in the organization. The 

 case of an animal shows that whatever kind of common 

 food is consumed, the necessary parts are formed ; and 

 it may be supposed that plants have similar power of 

 producing the necessary constituent parts from vaiious 

 substances both dissimilar to each other and to the 

 materials that form the composition of the plant. Of 

 elastic matters there may ever be little or no control : 

 they are generated by causes much beyond command or 

 application ; and of the solid substances that are applied 

 as manures, it is not known what part, or if any part 

 of them, passes into the plant as nourishment, what 

 agencies they and the soil exert over each other, and 

 what combinations they enter into with the atmosphere, 

 by which they ultimately become so highly conducive to 

 the growth of plants. 



The expectation of gaining any knowledge of the 

 matters which form the food of plants, and of a 

 mode of applying those matters to the soil, from an in- 

 vestigation of the constituent parts of the plants them- 

 selves, must rest on a very uncertain supposition ; for, 

 in any case of similarity or analogy that exists in the 

 natural world, no deduction of that kind can be made, 

 and from observation and experience all the knowledge 

 that is possessed on these subjects has been derived. If 

 the veil were withdrawn with which Nature has enshrouded 

 many of her works beyond the reach of our visual 

 organs, and our eyes were permitted to roam over afield 

 very probably for ever, and very justly, forbidden to 

 man, the probability is that our practice might not be 

 any way improved thereby. On the contrary, the atten- 

 tion might be diverted from principles that never fail, 

 and wander in pursuit of an Utopia, probably never to 

 oe obtained by our utmost scientific research, or re- 

 duced to practice by any human skill. But on 

 the other hand, it is very possible to use any 

 advantages that may result from such investigations, 

 without departing in any hurtful degree from the solid 

 principles of practice. The combination of science with 

 practice, so far as the former is capable of application, 

 will ever constitute the safe mode of proceeding wilb, 

 every judicious cultivator, ever bearing in mind, and 

 never for a moment forgetting, the influence of physical 

 causes and of external agencies that bear on every such 

 application, on which the whole matter hinges, which, 

 are generally overlooked, and over which humun agency 

 never can exert any control. From want of a due at- 

 tention to the different circumstances of application, 

 much misunderstanding and acrimonious disputation 



