must coexist with the subject. He wrote 'Institutes of Metaphysic' (1854); 'Lectures_on Greek Philosophy and other Philosophical Remains of J. F. Ferrier' (published posthumously, 1866).

FERRIER, fār'yā', Paul, French dramatist : b. Montpelier, 29 March 1843. He wrote several dramas previous to 1873, when he attained his first great success with Chez l'avocat' and 'Les Incendies de Massoulard.' These were followed by other successful pieces including 'Les Compensations) (1876); Les mousquetaires au couvent' (1880); Babolin' (1884); 'Joséphine vendue par ses sœurs' (1886); L'Art de tromper les femmes (1890); Calendæ (1894); Le Carillon' (1896); and the opera libretti, 'La Marocaine) (1879), music by Offenbach; 'Le Chevalier d'Harmental' (1896), music by A. Messager; 'La Fille de Tabarin' (1901), with V. Sardou, music by Gabriel Pierne.'

FERRIER, Susan Edmonstone, Scottish novelist: b. Edinburgh, Scotland, 7 Sept. 1782; d. there, 5 Nov. 1854. She was an intimate friend of Sir Walter Scott and of some of the most eminent literati of her day. She wrote three novels: 'Marriage (1818); The Inheritance (1824); and Destiny, or the Chief's Daughter (1831), all of which appeared at first anonymously. A collected edition, corrected by the author herself, was published in six volumes in 1841, and republished in 1850, 1881 and 1894. They are vigorous and lively pictures of Scottish life and character, full of social satire and clever caricature, but exhibit a certain hardness and want of sympathy at times. They enjoyed a great popularity in their day and the first of the three, especially, was highly praised by Sir Walter Scott. Consult Douglas, Sir George, 'The Blackwood Group (New York 1897); Doyle, J. A., ed., 'Memoir and Correspondence of Susan Ferrier' (London 1899); Howells, W. D., 'Heroines of Fiction' (New York 1901); Saintsbury, G., Miss Ferrier's Novels' (in Fortnightly Review, Vol. XXXVII, p. 314, London 1882).

FERRIÉRES, far'ryar', France, village in the department of Seine-et-Marne, 15 miles southeast of Paris. It contains a church dating from the 13th century and a magnificent château in Renaissance style, built in 1860. The château was the headquarters of the king of Prussia from 19 Sept.-5 Oct. 1870 and here Jules Favre vainly sought to conclude an armistice with Bismarck.

FERRIS, Albert Warren, American physician: b. Brooklyn, N. Y., 3 Dec. 1856. He was graduated at the New York University 1878, and at the Columbia University College of Physicians and Surgeons 1882. He became assistant in neurology, Columbia University, 1893, and assistant in medicine in the New York University medical department 1898. He was president of New York State commission in lunacy, 1907 to 1911; and senior resident physician Glen Springs Sanitarium, Watkins, N. Y., 1912-13; superintending director for commissioners of State reservation at Saratoga Springs, N. Y., since 1913; incorporator, director and financial secretary Pringle Memorial Home for aged men, Poughkeepsie, 1899-1908; editor-in-charge medical department, New International Encyclopedia' since 1901; princi

pal medical contributor to it and to 'International Year Book' since 1898. He is a contributor to several medical journals; department editor of The Modern Hospital, and is a member of several medical societies.

FERRIS, George Washington Gale, American engineer: b. Galesburg, Ill., 14 Feb. 1859; d. Pittsburgh, Pa., 22 Nov. 1896. He was graduated at Rensselaer Polytechnic Institute, Troy, N. Y., in 1881. From 1883-85 he lived in Louisville, Ky., and from then on in Pittsburgh, Pa. In 1892 he conceived the idea of a gigantic revolving wheel which, in spite of attempts of his friends to discourage him, he built successfully in Pittsburgh and erected for the World's Columbian Exposition in Chicago in 1893. The wheel could hold more than 1,000 passengers, and during the exposition it was one of the great attractions. It was named after its inventor Ferris Wheel' and copies of it, modified as to size, are still used as popular attractions at fairs and pleasure parks. Consult Snyder, C., Engineer Ferris and His Wheel' (in Review of Reviews, Vol. VIII, p. 269, New York 1893).

FERRIS, John Mason, American clergyman: b. Albany, N. Y., 1825; d. 1911. He was graduated at New York University in 1843 and subsequently studied at the New Brunswick Theological Seminary. In 1849 he was ordained to the ministry of the Dutch Reformed Church and held successive pastorates at Tarrytown, N. Y., 1851-54, Chicago 1854-62 and Grand Rapids, Mich., 1862-65. He was professor for one year at the Western Theological Seminary of Holland, Mich., and in 1865 became secretary of the Board of Foreign Missions of the Dutch Reformed Church, becoming treasurer of the board in 1886. He edited the Christian Intelligencer from 1881 to 1906.

FERRIS, Woodbridge Nathan, American educator and public official: b. Spencer, N. Y., 6 Jan. 1853. He was educated in the Oswego Normal and Training School and the medical department of the University of Michigan 1873-74. In 1875-76 he was principal of a business college and academy at Freeport, Ill., and in 1878-79 was principal of Dixon Business College and Academy. In 1879-84 he served as superintendent of schools of Pittsfield, Ill. In 1884 he removed to Big Rapids, Mich., where he founded Ferris Institute of which he became president. He was the Democratic candidate for Congress in 1892, and for governor of Michigan in 1904. He was elected governor for the term 1913-14, and was re-elected for the term 1915-16. His administration came in for considerable criticism as a result of the methods employed in handling the striking copper miners.

FERRO, fĕr'rō, or HIERRO, yer'rō, the most westerly of the Canary Islands, and the smallest of those which are inhabited; longitude of the western extremity, 18° 9'. It is about 18 miles long and 9 miles broad. It is a rocky, volcanic island, rising to the height of over 4,100 feet, and has numerous extinct craters, and a number of warm springs. It is by no means fertile, but good wine and brandy are made, and excellent figs are grown on the island. This island was once considered the most westerly point of the Old World, and geographers reckoned longitude from it. For

this purpose the longitude of Ferro was in France taken as exactly 20° west of that of Paris, though this meridian really passes some miles to the east of the island. German geographers adhered longest to the meridian of Ferro in constructing their maps. Pop. 7,667. FERRO-ALLOYS. See ELECTROCHEMICAL INDUSTRIES.

FERROL, fĕr-rōl', or EL FERROL, Spain, seaport in the province of La Coruña; about 12 miles northeast of the town of La Coruña; on the Bay of Betanzos, a few miles from the ocean. The bay forms one of the best natural harbors in Europe, and the narrow channel which leads to it is defended by the forts San Felipe and Palma. Charles III built here an arsenal for the Spanish navy, which is still in use and there is an extensive shipbuilding yard. The manufactures consist chiefly of military and naval equipments, linen, hardware, sail-cloth and leather. The sardine fishery is also important. Ferrol has figured in recent history, was the scene of a British repulse in 1800, and has twice (1809, 1823) been occupied by the French. Pop. 26,270.

FERROMAGNETISM. The property of being strongly attracted by a magnet, possessed by iron, steel, nickel, cobalt and certain alloys. See MAGNETISM.

FERRON, fa'rôn, Théophile Adrien, French general: b. Pré-Saint-Evroult, Eure-etLoire, 1830; d. 1894. He was educated at the Ecole Polytechnique and in 1852 joined the engineers corps. He gained distinction in the campaign in the Crimea and subsequently was appointed professor of military science at the Ecole d'Application de Metz, was employed at the war office in 1880 and in 1887 became Minister of War. In 1878 he became colonel and in 1886 general of division. He has published 'Considérations sur le système défensif de la France (1873); Considérations sur le système défensif de Paris) (1875); 'Instructions sommaires sur le combat (1883); Quelques indications pour le combat) (1892).

FERROTYPE, or ENERGIATYPE, in photography, a process first made public by Robert Hunt in 1844, in which the negative was developed by a saturated solution of protosulphate of iron, with mucilage of gum-arabic, and fixed by soaking in water to which a small quantity of ammonia or hyposulphite of soda had been added. See PHOTOGRAPHY.

FERROUS SULPHATE, FERROUS COMPOUNDS. See IRON.

FERRUCCI, fĕr-roo'che, Andrea, Italian sculptor: b. Fiesole, 1465; d. 1526. He studied under Francesco di Simone Ferrucci and Michele Maini and in 1512-18 superintended the work on the cathedral at Florence, for which he himself executed a statue of Saint Andrew. His greatest work is a baptismal font at Pistoia. The Fiesole cathedral possesses a marble reredos from his hand and the Bargello, Florence, has a Holy Family. Other works of Ferrucci are the tomb of the Saliceti at Bologna, decorations in San Martino, Naples, and the Strozzi tomb in Santa Maria Novella, Florence, begun by him and finished by Casini and Boscoli. His work shows that he was a great admirer of Michelangelo. He excelled in ornamentation.

FERRY, fe'rē, Gabriel, the YOUNGER, French author, dramatist and novelist: b. Paris, 30 May 1846. He is a son of Gabriel the Elder and employs the same pseudonym. At first he was connected with a bank, but soon followed in his father's footsteps and devoted himself to literature. He has written a number of plays, 'Réginah' (1874), being one of the best. His miscellaneous prose includes 'Les dernières années d'Alexandre Dumas' (Paris 1882); 'Les patriotes de 1816) (Paris 1883); 'Les deux maris de Marthe (Paris 1884); Balzac et ses amies (Paris 1888); Cap de fex' (Paris 1889); Les exploits de César (Paris 1889); 'Les exploits de Martin' (Paris 1890); Les pronesses de Martin Robert) (Paris 1890) etc.

FERRY, Jules François Camille, French statesman: b. Saint Dié, France, 5 April 1832; d. Paris, 17 March 1893. He was admitted to the Paris bar in 1854, and speedily identified himself with the opponents of the empire. His hostility was carried into journalism, and a series of articles in the Temps_(Times), were republished as 'The Fantastic Tales of Haussmann' (1868). In 1869 he was elected to the National Assembly, where he voted against the war with Prussia; and during the siege of Paris by the Germans (1870-71) he played a prominent part as central mayor of the city. He was Minister to Athens 1872-73, and in 1879 became Minister of Public Instruction and began an agitation against the Jesuits. Their expulsion was effected, and brought about the dissolution of the ministry in September 1880. M. Ferry then formed a cabinet, which remained in office till November 1881. In February 1883 he again became premier, with a policy of "colonial expansion," involving a war in Madagascar and the invasion of Tonquin, where a minor reverse to the French troops was followed by a storm of criticism directed against the premier which caused his downfall in March 1885. On 10 Dec. 1887 he narrowly escaped assassination at the hands of a madman, one of whose shots was ultimately the cause of his death. In 1890 he was made senator,

and three weeks before his death was elected president of the Senate. The Panama scandal left his reputation unscathed. He was a strong anti-clerical who in the remodeling of primary instruction, placed education on a free, non-clerical and obligatory basis. His 'Discours et Opinions' appeared in seven volumes (1893–98). Consult King, 'French Political Leaders' (New York 1882); Rambaud, Jules Ferry (Paris 1903); Sylvin, Célébrités contemporaines (Paris 1883).

FERRY, Orris Standford, American statesman and solider: b. Bethel, Conn., 15 Aug. 1823; d. Norwalk, Conn., 21 Nov. 1875. He was graduated at Yale in 1844. He studied law and was admitted to the bar in 1846. After filling important political places in his native State he was in 1859 elected to Congress as a Republican, and sat as one of the famous Committee of Thirty-Three appointed to consider and report upon the condition and relations of the seceded States. He was colonel of the Fifth Connecticut Volunteer Infantry (1861), and served from 1862 to the end of the war as brigadier-general of volunteers. He was elected to the United States Senate as a Republican in 1866, and re-elected in 1872.

FERRY, Thomas White, American politician: b. Mackinac, Mich., 10 June 1827; d. Grand Haven, Mich., 13 Oct. 1896. Early in life he moved with his family to Grand Haven, Mich., and was educated in its public schools, entering business there. He served in the State legislature and from 1865 to 1871 was a Republican member of Congress. He was elected to the United States Senate and served from 1871 to 1883. On the death of Henry Wilson he became acting Vice-President of the United States and president of the Senate pro tempore from 1875 to 1877. He presided over the high court of impeachment of Secretary of War Belknap and over the 16 joint meetings of the two houses of Congress during the Hayes-Tilden contest. After the end of his term as acting Vice-President he was re-elected president of the Senate pro tempore in 1877, 1878 and 1879.

FERRY, a franchise or right to maintain a boat upon a river or other body of water and carry people, animals, vehicles and other property between certain places for a reasonable toll. It is considered to be in the nature of a public highway over the water, and the franchise can only be acquired by legislative authority, either directly, as by a special act, or indirectly, through courts, municipalities, counties, commissioners or other subordinate bodies acting under powers conferred by the legislature. The grant by which the franchise is given usually specifies certain conditions as to time, service, etc., and whether the privilege is exclusive within certain limits or not. Either an individual or a corporation may hold this franchise, and preference is given to riparian owners. A ferryman is a common carrier, subject to the same duties and liabilities.

Ferry-Boats.- Steam vessels are now employed for carrying passengers and vehicles for short distances across rivers, lakes and straits. On narrow rivers, ferries are frequently operated by means of a chain, lying along the bottom of the river, secured at both ends and passing over a drum on board the ferry-boat, the drum being revolved by the engine, or in small boats, by hand. This method is particularly suitable for working in foggy weather, or where there is a strong current. Another type of ferryboat, used on the Rhine and elsewhere, is moved across by the combined efforts of the current and the pull exerted by a long moving chain which is fixed upstream. By directing the bow upstream, the pressure of the current against the side of the boat causes it to cross from one side to the other. The large ferry-boat for passenger traffic is now usually a screw-vessel having a screw at either end, it having been found that greater speed and more room could thus be obtained than with paddle-wheels. These vessels are found in large numbers in New York harbor where thousands of people are transported across the rivers and bay every day. There are also many large paddle-vessels, this type being usually selected for small or mediumsized ferry-boats. Large vessels are employed for conveying railway trains in places where it is impracticable or undesirable to construct bridges. These vessels are almost exclusively paddle-steamers, owing to the greater facility which they possess for stopping and reversing when being brought into position for running the trains on board. Vessels of this type plied

on Lake Baikal before the opening of the circum-Baikal section of the Trans-Siberian Railroad. They are also employed at San Francisco and New York and on Lake Michigan.

FERRYLAND, Newfoundland, the capital of a district of the same name, 35 miles south of Saint Johns. It has a good harbor with a lighthouse. Sir George Calvert, afterward Lord Baltimore, founded a settlement here named Avalon. There exist remains of an old fort. Pop. 600.

FERSEN, fĕr'sĕn, Fredrik Axel von, Swedish statesman: b. Stockholm, 1719; d. 1794. He was descended from a Scottish family named McPherson, entered the Swedish Life Guards in 1740 and from 1743 to 1748 was in the French army, in which he rose to the rank of brigadiergeneral. He was in the Swedish service in the Seven Years' War in which he won signal successes over the Prussians. He became field marshal in 1770. His later years were occupied with politics; he was one of the leaders of the "Hats" and for several years obstructed the measures of Gustavus III, whom he treated with colossal insolence. He was arrested in 1789 and thereafter remained aloof from politics. His 'Historiska Skrifter' is mainly autobiographical, but its historical accounts are often biased. Consult Bain, R. N., Gustavus III' (London 1895).

FERSEN, Hans Axel, COUNT VON, Swedish military officer and diplomat: b. Stockholm, Sweden, 4 Sept. 1755; d. there, 20 June 1810. He came to America in 1780 on the staff of Rochambeau; fought under Lafayette and received from Washington the Order of the Society of the Cincinnati. Later he returned to Paris where he had already been stationed in 1778-80; he became a favorite at court, and was the disguised coachman at the flight of the royal family from Versailles during the Revolution. He was deeply devoted to Queen Marie Antoinette and made a number of unsuccessful attempts to save her. His relations with her have been the subject of a number of books. He returned to Sweden, where he was received with honor, and in 1801 was made grand marshal of that country. He was entrusted with a number of important diplomatic missions. On suspicion of complicity in the death of Prince Christian of Sweden he was seized by a mob while marshaling the funeral procession, and beaten to death. After his brutal assassination his entire innocence was clearly established. Consult Carnegy, M., A Queen's Knight; the Life of Count Axel de Fersen' (London 1912); Fersen, Comte J. A. de, The French Army in the Revolutionary War' (in Magazine of American History, Vol. XXV, pp. 55 and 156, New York 1891); Gaulot, P., Un Ami de la Reine (Paris 1894; translated into English as 'A Friend of the Queen' by C. Hoey, 2 vols., London 1894); Granath, W., Fersenska Mordet. Historisk Roman' (Stockholm 1904); Hansson, O., 'L'Assassinat de Fersen' (in Revue d'Histoire Diplomatique, Vol. XXV, p. 195, Paris 1911); Heidenstam, O. G. de, 'Marie-Antoinette, Fersen et Barnave; leur Correspondance (Paris 1913); Klinckowström, R. M. de, ed., Le Comte de Fersen et la Cour de France) (2 vols., Paris 1878); O'Connor, T. P. Some Old Love Stories (London 1895).

FERTILIZATION. See EMBRYOLOGY.

FERTILIZATION OF FLOWERS BY INSECTS. See POLLINATION.

FERTILIZATION OF THE OVUM. See EMBRYOLOGY.

Fer

FERTILIZATION IN PLANTS. tilization is generally defined as the union of definitely organized male and female elements. This definition is strictly correct for plants in which the uniting elements can be called sperms and eggs; but in many of the lower plants algae and fungi - the elements which unite are alike in size and appearance, not being differentiated as male and female. Many botanists use the term conjugation to describe the union of such similar gametes, as the uniting elements are called. Between these cases in which the gametes are alike and those in which they are very different, there are all imaginable gradations. However, in all cases, the essential feature is the union of the two nuclei of the gametes, whether the gametes be alike or unlike. It is still quite generally believed that the two nuclei fuse in the resting condition and that the chromatin of the two parents becomes mixed. A thorough cytological study of fertilization has been made in only a few plants, and in most of these the chromatin at the time of fertilization is in the form of separate chromosomes. (See CHROMOSOME). There is no doubt that the chromosomes of the male and female, in these cases, are entirely separated and that the first division of the egg takes place without any fusion or even close association of chromosomes. The two nuclei resulting from the first division of the egg pass into the resting condition and the chromatin of the male and female parents becomes indistinguishable. During all the rest of the life history no one has yet been able to identify the male and female chromosomes; but there is such strong evidence that the chromosome is an individual organ of the cell, maintaining its identity throughout the life history, that most cytologists believe there is never any real fusion of male and female chromosomes, although there is a very close

contact.

Fertilization serves two purposes: it acts as a stimulus to development and it keeps the characters of the species approximately constant. As a result of the stimulus, the fertilized egg divides repeatedly and builds up the embryo. There seems to be a limit to the duration of the stimulus and, when that limit is reached, the organism grows old and dies, but, as it reaches maturity, it produces eggs, which, stimulated by fertilization, begin the process again. That fertilization functions in keeping the species approximately constant is generally admitted. Variation is universal and no two individuals are exactly alike. If an individual varies widely from the type, we generally call it a freak or sport. Such freaks or sports are either incapable of fertilization and consequently leave no progeny, or they are fertilized by some individual of the species which has not varied much, and the union with a normal individual reduces the aberrant form to the ordinary plane of the species. A perennial illustration is the six-fingered man, an obvious freak. Intermarriage with normal individuals for generation after generation finally breeded the six-fingered condition out of the family. Doubtless, plants behave in the same way.

Variations which maintain themselves and stubbornly refuse to be reduced to the type are called mutations (q.v.) It is very probable that many "species have arisen in this way. Consult Wilson, E. B., The Cell in Development and Inheritance'; Mottier, D. M., Fecundation in Plants (Carnegie Inst. of Washington. Publication No. 15). CHARLES J. CHAMBERLAIN. FERTILIZERS. Any substance applied to the soil to aid the growth of plants may properly be called a fertilizer. The name has, however, become associated with a class of materials manufactured and sold for this purpose, the handling of which now constitutes an important industry.

The constituents of the plant that it derives from the soil are nitrogen phosphorus, sulphur, potassium, sodium, calcium, magnesium, iron, aluminum, manganese, silicon, chlorine. Of these nitrogen, phosphorus or phosphoric acid, and potassium or potash, are the substances most likely to be deficient in the soil and therefore the ones that are contained in fertilizers. A fertilizer may contain any one or more of these substances.

The chief distinction between the functions of farm manure and commercial fertilizers may be stated in a general way to be that farm manure increases crop production by improving the condition of the soil, as well as by furnishing plant nutrients, while commercial fertilizers may act directly as a plant-food material without_materially affecting soil structure.

It is evident, therefore, that commercial fertilizers are not an adequate substitute for farm manure or green manures for producing permanent improvement. Their function consists in supplementing the available supply of plant-food in a soil which may be deficient in any one or more of the substances usually contained in fertilizers. On virgin soils commercial fertilizers are usually superfluous; but as loss of plant-food goes on under cropping, restitution must be made and, as this is usually not adequately done with farm manure, fertilizers are finally called upon.

Where there is large loss of plant-food from soil constituents due to leaching, there must be a large excess of potential fertility, in order that the growing crop shall at all times be supplied with available plant-food. A deficiency in any constituent will check growth by compelling the plant to depend upon a less readily available supply. Commercial fertilizers are useful by presenting readily available food to the plant when it is beginning growth and when a deficiency in the supply is likely to produce a permanent injury.

As the price of land increases, as the cost of labor becomes greater and as the value of the crop augments it becomes more important that maximum crops shall be raised, and for these reasons commercial fertilizers usually have greatest sale where agriculture is most intensive. There are also many special crops requiring more of one plant-food element than of another, and the needs of these can best be met by the use of commercial fertilizers.

Historical. The value of animal excrements applied to soils on which crops were grown has been appreciated by the husbandman as far back as records go. Why this manure

is beneficial, and what relation its constituents bear to those of plants, are matters which have only been worked out during the last century, and knowledge of which has led to the use of fertilizers composed of mineral salts, commonly known as commercial fertilizers.

The earliest record of the use of artificial manures for increasing the yield of crops is contained in a book entitled A Discourse Concerning the Vegetation of Plants.' The title page also contains the following announcements: "Spoken by Sir Kenelm Digby, at Gresham College, on the 23d of January 1660." The author advocates the use of saltpetre to increase the yield of crops, and says: "By the help of plain saltpetre, dilated in water and mingled with some other fit earthly substance, that may familiarize it a little with the corn into which I endeavored to introduce it, I have made the barrenest ground far outgo the richest, in giving a prodigiously plentiful harvest." His dissertation does not, however, show any true conception of the reason for the increase in the crop through the use of this fertilizer. The almost total absence of any knowledge of the composition of plants, and the crude state of chemistry at that time, made this quite impossible.

It was not until 1804 that any light was thrown upon the subject. In that year was published 'Recherches Chimique sur la Végétation' by Theodore de Saussure. This brilliant French investigator was the first to appreciate the significance of the ash ingredients of plants; to point out that without them plant life was impossible, and to show that only the ash of the plant was derived from the soil.

Justus von Liebig is commonly regarded as having laid the foundation upon which the commercial fertilizer industry has been built. Certainly his reports to the British Association in 1840 and again in 1842 made the British agriculturists regard as they never had done before the importance of a sufficient supply of certain readily soluble mineral substances in the soil. He supported the contention of De Saussure regarding the importance of mineral matter in the plant, and its extraction from the soil. He refuted the theory, at that time popular, that plants absorbed their carbon from humus, but made the mistake of attaching little importance to the presence of humus in the soil. He showed the importance of potash and phosphates in manures, and in his earlier writings spoke of the value of nitrogen for fertilizing crops, but afterward made the mistake of denying the usefulness of nitrogenous manures for plants, holding that the ammonia washed down by rain affords a sufficient supply.

By the middle of the 19th century it was well understood that potash, phosphoric acid and nitrogen were valuable constituents of fertilizers, and that the other mineral elements of plant-food, with the occasional exception of calcium, were always present in sufficient quantity in arable soils. It has since been shown that the family of plants known as the Leguminosa have the ability to secure a large part, at least, of their nitrogen from the air, and that as these plants are very rich in nitrogen they leave a supply of nitrogen in organic matter in the soil when plowed under.

VOL. 11-10

Complete and Incomplete Fertilizers. Fertilizers, containing nitrogen, phosphoric acid and potash, mixed together so that an application of the preparation will result in bringing each of these substances in contact with the soil wherever applied, are called complete fertilizers. The proportions in which the constituents are mixed vary with the different brands and factories. Sometimes a fertilizer of this kind will be advertised for use on a certain crop, and will contain the nitrogen, phosphoric acid and potash in the proportion in which the manufacturer believes they will produce the best yields of that crop. He has, however, no means of knowing the requirements of the soils on which the fertilizer is to be used.

Incomplete fertilizers contain only one or two of the customary fertilizer ingredients.

Available and Unavailable Fertilizer Material. The fertilizing constituents in a fertilizer may be present in a readily soluble or difficultly soluble condition, depending upon the chemical combinations and, to some extent, upon the physical condition in which they are found. Thus phosphoric acid when in the form of phosphate rock as it is taken from the deposits is a very difficultly soluble substance, and plants can avail themselves of it only in small quantities. After the same rock has been treated with sulphuric acid the phosphoric acid is in a form in which it can be readily used by plants. To a more limited extent the same is true of the phosphoric acid in basic slag, which, when the slag is in an unground condition, is not of much use to plants, but when the slag has been finely ground furnishes a valuable form of plant-food.

When the fertilizing material is in a condition in which it can be readily used by the plant it is said to be "available," and when it can be used only with great difficulty it is said. to be "unavailable." It is important that the purchaser should know in what form the constituents are present in a fertilizer.

Nitrogenous Fertilizers.- Nitrogen is ab sorbed by most plants only in the form of a soluble salt; hence for the cereals and many other crops it is desirable either to have it in this form or to incorporate it in the soil in a condition in which it will be readily converted into a soluble condition. Plants like the clovers, alfalfa, peas, beans, etc., have the power of using the nitrogen of the air, and hence do not require nitrogenous fertilizers in such large amounts. These plants may be used to increase the supply of nitrogen in the soil. Nitrogen is the most expensive constituent of fertilizers, and is extremely important, as it is used in large amounts by plants and is likely to be deficient in soils. The form in which nitrogen is present in a fertilizer may make a great difference in its value and in the way, in which it can be best applied. Nitrogenous fertilizers differ in having their nitrogen either in the form of a soluble salt or combined as organic material.

Nitrate of Soda.- This now constitutes one of the principal sources of inorganic nitrogen in artificial manures, having largely taken the place of Peruvian guano, which was used for many years, and the profitable use of which did much to promote the extensive use of com