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THE TROPICAL AGRICULTURIST. 



[June 2, 1884. 



ii can be classed as one of the sciences ; is it pure science ? 

 Assuredly not. But it certainly has progressed suflficieutly I 

 to be rated ;is scientific. Its attainmeuts in this are far 

 greater than its deficiencies. Its problems are not all solved, j 

 it must be admitted. There are certain questions in agri- 

 culture that so far have baffled all investigations. Time ' 

 may explain them. Perhaps we should rather call agri- 

 culture inchoate science. Tbis much we may safely claim, : 

 I think clearly, there are many things it has firmly estab- 

 lished, and upon which it can and does safely proceed, i 

 Analysis by its wondrous searching reveal facts wliicli be- 

 come truths, axioms ; and upon the strength of which action 

 can be logically based. Herein is agriculture science in 

 the most rigid acceptation of the term. Its conquests are 

 many and great. But Uttle that is tentative belongs unto 

 it. True, certain processes of growth and assimilation are 

 yet a sealed book as to their comprehension. 



Dr. I. R. NichoUs very pertiuently says;— '-I have said 

 that the new agriculture rests upon science and positive 

 knowledge ; but this remark must not be understood to 

 mean that all the various departments of modern husbandry 

 rest upon pure knowledge or demonstrated facts, for this 

 position would plainly be indefensible ; but I do say that 

 the great fundamental principles are understood and estab- 

 lished as clearly as those of most other branches of human 

 knowledge. So far as the chemistry of plant structures 

 and the forms of food they require are involved, our know- 

 ledge is positive ; and also it is true that most of the 

 details of i>ractical farm industry are now so well under- 

 stood that they may be said to be almost or quite_ re- 

 moved from the regions of doubt. Clouds of uncertainty, 

 the feeling that every step was governed by chance or 

 blind caprice, belonged to the old agriculture ; it certainly 

 does not to the new." 



Dr. J. B. Lawes uses the term, scientific agriculture, in 

 his able writings. He speaks of *' our advance in the path 

 of scientific agriculture.*' Says Prof. aicBryde : *' Agricult- 

 ure requires for the elucidation of the principles involved 

 in its various practices, a very wide range of scientific in- 

 quiry." It is this scientific inquiry which has brought to 

 light many truths bearing upon agriculture which now rest 

 on the bed-rock of accuracy. The intelligent farmer, with 

 all the accumulated data of plant hfe, food assimilation, 

 weather influences, soil structiu-e and soil treatment, can 

 proceed confidently, and not be tossed about on the waves 

 of uncertainty and mere caprice. 



[We are not prepared to accept the proposition that 

 applied science is synonjnnous with art. Nor can we admit 

 that because we properly use the term "scientific agri- 

 culture," science and art are therefore one and the same 

 thing ; and notnnthstandiug the original " ars " of the Latin 

 may have meant skill in execution, the modern '* art " 

 must have a broader significance. There are numerous 

 artisans who are anything but " skilled "' in their arts — 

 mere bunglers in fact. In short, art, as we must under- 

 stand it today, is simply the power of imitation — the 

 ability to do something without any particular reason — 

 while' science is the power of reasoning on what we do, 

 so that by the facts we gather from this experience we 

 may do something or know something which we have never 

 done or known before. By art we can make a right-angled 

 triangle ; by science derived from the triangle we can meas- 

 ure the height of a tree or a star. Thus, it is not difficult 

 to see that in agriculture mere art and science are two 

 distinct things. Scientific agriculture becomes agriculture 

 aided by science. — Ed.] — Gardeners' Monthly. 



CONSTITUENTS OF SOILS. 



What are salts? Salts are all combinations of acids with 

 alkahes, or, as they are called, alkaline bases. In their pro- 

 perties salts differ as widely as possible; some are cryastal- 

 lisable, others not so ; some are colorless, others o£ various 

 colors; some excite taste, others are insipid; some are soluble, 

 others insoluble ; some are volatile, others fixed. The term 

 salt is of wide and various appUcation. But, in relation 

 to the subject under consideration, the common salt, used as 

 a seasoner and preserver of food, is a good example. This 

 isthf chloride of sodium, formed when chlorine and sodium, 

 or hydrochloric acid and soda, come together. Sodium is a 

 soft metal of a silver white color, and light enough to float 

 upon water. In the metallic state it is not known to occur 



in nature, and, therefore, does not directly act upon veget- 

 ation. "With chloriue it forms the chloride of sodium (com- 

 mon sail ), and in this form it is more or less beneficial to 

 vegetation. With oxygen it forms soda; with sulphur, the 

 sulphuret of sodium; and these salts are likewise variously 

 beneficial to plants. Saltpetre is a salt. It is potash united 

 to aquafortis. These have united, and their characters are 

 ueutrahseil by each other, so that in saltpetre one will not 

 perceive either potash or aquafortis. They have formed a 

 neutral salt. 



What are "carbonates," "chlorides," "nitrates," "silicates," 

 &c., frequently named in agriculture? These are some of 

 the salts formed by the mutual action of acids and alkalies, 

 or, in some cases, metals, already described. Thus: the 

 carbonates (carbonic acid) of lime, magnesia, potash, soda, 

 iron, manganese. Chlorides (chloric acid) of potash, soda, 

 lime, manganese, silver, zinc. Citrates (citric acid) of potash 

 and Ume. Humates (the humate acid of soils) of lime. 

 Nitrates (nitric acid) of potash, soda, lime, ammonia, mag- 

 nesia. I'liosphates (acid of phos]:)horus) of alumina, lime, 

 magnesia, poiash, soila. Silicates (acid of silica) of potash, 

 soda, lime, magnesia, alimaina. Sulphates (sulphuric acid) of 

 ammonia, potash, soda, Ume, magnesia, alumina, iron, copper, 

 manganese. Thus it will be seen that the same acid with 

 another base forms a different kind of salt. Many of these 

 acids, alkahes and salts form essential constituents of animal 

 and vegetable bodies, soils and manures; and the changes 

 and combinations which they undurgo are intimately con- 

 nected with the development of animal and vegetable life, 

 and the growth of animal and vegetable forms. 



What are bases? The term base implies the leading con- 

 stituent of a compound. Thus, m the compound '"carbonate 

 of lime." the latter is the alkaline earthy base. Every one 

 is acquainted with the general properties of that group of 

 substances which bears the name of acids. The term base 

 is perhaps not so universally understood. We designate com- 

 pounds possessing the power of combining with acids and 

 neutralising their acid properties by the word bases. A com- 

 pound of an acid with a base is denominated a salt (this 

 name has no reference to the taste). Now, in these com- 

 pounds — in salts — one base may be made to replace another 

 base, one acid another acid. Carbonic acid, water, ammonia 

 and sulphates are necessary for the existence of plants, be- 

 cause they contain the elements of which their organs are 

 formed. But other substances are requisite for the form- 

 ation of certain organs destined for special functions pe- 

 culiar to each family of plants. Most plants, perhaps all 

 of them, contain organic acids of very different composition 

 and properties, all of which are in combination with bases, 

 such as potash, soda, lime or magnesia; plants containing 

 free organic acids are few in number. The bases eWdently 

 regulate the formation of the acids, for the diminution of 

 the one is followed by a decrease of the other; thus in 

 the grape, for example, the quantity of acid contained in its 

 juice is less when it is ripe than when unripe; and the bases, 

 under the same circumstances, are found to vary in a sim- 

 ilar manner. Such constituents exist in the smallest quantity 

 in those parts of a plant in which the process of assimil- 

 ation is most active, Jis in the mass of woody fibre ; and their 

 quantity is greatest in those organs whose office it is to pre- 

 pare substances conveyed to them for assimilation by other 

 parts. The leaves contain more inorganic matters than the 

 stem. 



It is most important to bear in mind that any one of the 

 many alkaline bases may be substituted for another, the 

 action of all being the same. The law that one base may 

 be substituted for another is of the highest practical value. 

 This will be perceived when it is considered that if a soil, 

 containing originally all the elements essential to a crop, 

 becomes exhausted of one, yet another may be substituted, 

 which, combining with the organic acid of the plant, enables 

 it to perform and perfect all its functions: potash, soda, 

 magnesia, t&c, may, in certain circumstances, supply the 

 place of lime. When roots find their more appropriate^ base 

 in sufficient quantity they will take up less of another. The 

 base of all sales acts ever the same in agriculture. Pecuh'ar- 

 ity of action depends upon the acid of trie salt. This is 

 ttie great practical principle of agricultural chemistry. It. 

 opens veins, rich in results, more precious than mines of gold. 

 It is not known in what form manganese and oxide of iron 

 are contained in plants; but we are certain that pota.*;h. soda 

 and magnesia can be extracted, by means of water, from 



