Symud i'r prif gynnwys
Cuddio Rhestr Erthyglau

11 erthygl ar y dudalen hon









[No title]



CHEMISTRY AND AGRICULTURE. The greater part of practical knowledge being derived from observation and experience, the scientific principles on which the facts are founded are always learned last, and no person is capable of taking a comprehensive grasp of these principles and of their application, unless the mind be stored with a most intimate knowledge of the practice in every detail. This observation is applied to every practical art, and to none more strictly than to agriculture. The science of the art is only now being learned, and chemists are busied in discover- ing in what the effects consist that have been long esta- blished by experience. All chemical action is combination or union, and decomposition or separation; light and heat often appear as the new arrangements take place, heat is disengaged and often absorbed, and a change of temperature happens. Bodies that have little or no affinity, and do not enter into combinations, are made to do so by the addition of one or more substances and this principle'shows the ne- cessity cf applying a number of substances at one time, and of bringing them into contact with each other in a state of minute adherence. Many kinds of chemical action are effected by heat, electricity, and other agencies over which any control is impossible, and which do not take place from any comminution and mixture; yet by that process a ready accession of means will be afforded of producing combina- tions, which in another state of existence of the substances would not have happened. Chemical affinity is reckoned a case of electrical attraction,, and that bodies combine from being in opposite electrical states. A decomposition consequently proceeds from the same electrical condition. Though usually reckoned the same, electric attraction may be termed the principle in action, and chemical affinity the power by which bodies I unite—the one being in this sense a measure of the other. All chemical forces are subordinate to the cause of life, and to heat and electricity, and to mechanical friction and motion. The latter power is able to change their direction, increase ot diminish tendency, and also completely to stop and reverse their action. But causes must exist to produce chemical affinity, or the cycle of life would stand still; and from our ignorance of these causes, and of the application, it is pro- bable that in many cases their action is arrested and stopped, and often rendered useless, not produced at all, or at best but accidentally, arising from our proceedings not being yet based on definite or measured causes. I have ever been of opinion that the want of practical knowledge effectually prevents the professors of chemistry from rendering any tangible assistance to, the performance of agriculture, lo teach an art simply by itself, and to state and explain the science, or the systematised experience of it, is a simple process but to use it in relation with another that is either allied or remote is a widely different subject, and requires a thorough and most intimate knowledge of the nature and properties of both objects which are sought to be connected. And the want of practical knowledge will ever disable the cbei-iiigtfrom being useful to agriculture Chemists expect that their art wiII effect in agriculture the same results as in medicine, where the inert ligneous matter, formerly so hurtful to living organs by its decompo- sition, has been separated in vegetable products, and the active prin-clple has been presented in a pure crystalline form. But the circumstances are wholly different; no living body will suffer without harm the contact of decaying matter- but the earth is a dead receptacle, and can sustain no ininry from that process. On the contrary, the inert ligneous mat- ter affords by its decomposition the materials or body on which the refined manure must act in the soil. A medicine supplies no food to the body, but modifies the action of the functions of its organs and food must be provided in order to develop its effects. The most concentrated and powerful manure would produce no effect on pure earths or oxides- nor could medicine exert any influence on the original constitu- ents of an animated body without the living mechanism of muscular fibre and functional organs. Now, instead of informing us of what elements the sub. stances of crops and manures are formed, it would be much I. more likely to forward the art of cultivation if the time Was spent in bringing different bodies into contact, observing the affinity, marking, the effects of the reciprocal action, and con- verting into use the new combinations that are known to re- sult from chemical action. It would even- be useful to know where an affinity existed, or where a repulsive quality was inherent between what bodies an easy union is effected, and in what cases a peculiar quality is required, and a certain quantity of materials is necessary. We yet know very, little of the power of acids in dissolving bodies, and in renderino- them minutely transmissible; the application to bones is only a beginning. And we are only beginning to think of the benefits that may happen from mixing manures with the soil. It is the business of Government, or some powerfiil society to employ scientific men on such pointsbut, unless they b<? also practical men, the labour would be useless, for the rea- sons now mentioned. J. D. 10th May, 1848.