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 AGRIOOLA mitia married Tacitus the historian, who wrote his life. AGRICOLA. I. Genre, a German mineralo- gist and physician, born at Glauchau, Saxony, March 24, 1490, died in Chemnitz, Nov. 21, 1555. His name was originally Bauer (peas- ant), of which he adopted the Latin equivalent. He was at first rector of a school in Zwickau, afterward studied medicine at Leipsic, devoted himself to metallurgy, and in 1531, on the invi- tation of Duke Maurice, settled at Chemnitz. He attempted to reduce mineralogy and metal- lurgy to a science, and introduced considerable improvements in the previously rude art of mining. He first made chemical analyses of the different earths. His mind was, however, deeply tinged with the superstitions of his age. Having renounced Protestantism before his death, his body was refused burial in Chem- nitz. He wrote De Re Metallic^ De Ortu et Causw Subterraneorum, and De Mensuris et Ponderibus Romanorum atque GrcBcorum. II. Joliann Friedrieh, a German musician and com- poser, born near Altenburg, Jan. 4, 1720, died in Berlin, Nov. 12, 1774. He studied music under Sebastian Bach, was chapelmaster of Frederick the Great, and wrote several operas, among them "Iphigenia in Tauris." He was husband of the vocalist Mme. Molteni. III. Johannes (originally SCHNITTEB or SCHNEIDEB), a German theologian, born in Eisleben, whence he is called Magister Islebius, April 10, 1492, died in Berlin, Sept. 22, 1566. He studied at Wittenberg and Leipsic, and acquired the friendship and esteem of Luther, who in 1525 sent him to Frankfort-on-the-Main, to institute Protestant worship there. On his return he was parish priest of Eisleben, and here he com- menced that Antinomian controversy which he subsequently renewed from his professorial chair in Wittenberg (1536-'8), and for which he was dismissed from that university. He next became chaplain and general superintendent to the elector of Brandenburg. He wrote several theological works, as well as an account of the common German proverbs. IV. Rndolf, an eminent scholar, born in Groningen in 1442 or 1443, died in Heidelberg, Oct. 28, 1485. He travelled in France and Italy, and won the es- teem and patronage of Ercole d'Este, duke of Ferrara. On his return he was chosen profes- sor of philosophy at the university of Heidel- berg. He wrote various works of a miscella- neous character, the most remarkable of which, perhaps, is an essay entitled Tractatus de In- ventione Dialectic^ in which he devotes con- siderable space to the discussion of the ability of deaf mutes to acquire such knowledge of language as to be able to converse with others by writing. He was among the first to intro- duce the study of Greek into Germany, and gave lectures on Greek literature at Worms and Heidelberg. AGRICtXTlIRAL CHEMISTRY, the study of the chemical relations of substances concerned in agricultural production. The whole natural 14 VOL. i. 14 AGRICULTURAL CHEMISTRY 193 science of vegetable and animal production ie usually called agricultural chemistry, although it includes much of physics, meteorology, vege- table and animal physiology, and geology. It is impossible to separate these subjects, with- out grave errors; and hence those works which give the justest view of the chemistry of agriculture are not strictly treatises on ag- ricultural chemistry. The object of agricul- ture is to develop from the soil as large a quan- tity as possible of useful vegetable products; or indirectly, of animal products. To assist in this, agricultural chemistry must inquire into the composition of the plant and animal. It finds that all vegetable and animal substances contain a variable, usually large proportion of water, which is essential to their life, but may be separated from them by heat without other- wise affecting their chemical composition. At a high temperature, dry animal or vegetable tis- sues are resolved into two portions ; one passes into the air as volatile gases or vapors ; another, indestructible by heat, remains as ashes. In most vegetable and animal substances, the com- bustible or organic part forms 90 to 99 per cent, of the whole dry matter ; the proportion of inorganic substances (ash) being small. The organic matter mainly consists of four elements, viz. : carbon, oxygen, hydrogen, and nitrogen. These simple bodies are united in the plant and animal into thousands of combinations, the ex- tended study of which belongs to organic chem- istry. Most agricultural products, however, consist chiefly of but a few of these combina- tions or proximate elements. These may be specified under four classes: 1. The oils and resins, including wax. 2. Cellulose (cell tissue, woody fibre); starch; the sugars, cane and grape ; the gums, arabine, bassorine, dextrine (starch gums). 3. Pectose (the pulp of green fruits) and its derivatives. 4. The nitrogenous or sanguigenous* principles, viz. : albumen, case- ine (legumine, avenine), emulsine, and fibrine (gluten). The first three groups are com- posed exclusively of carbon, hydrogen, and oxygen (some of the oils, of carbon and hydro- gen only), while all the members of the fourth group contain 15 to 18 per cent, of nitrogen, most of them small quantities of sulphur, and phosphorus also, in addition to the three ele- ments above named. The whole growing part of the plant is a porous substance, as easily penetrable by air as a sieve, and a hygroscopic substance, absorbing and retaining the vapor of water from the air or soil with great force and obstinacy. When a vegetable is destroyed by burning, it is mostly resolved into air. On the other hand, when it is formed by growth, its substance is mostly derived from air. The atmosphere which perpetually bathes and pene- trates the leaves of plants supplies them with carbon, hydrogen, nitrogen, and oxygen. The atmospheric source of carbon is carbonic acid. This gas is a constant ingredient of the atinos- bodies in animal nutrition.
 * Blood-producing ; so called from the function of these