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the pollen grain and its tube, and the female, consisting of the embryo-sac, alternate with the sporophyte generation, the sunflower plant, which begins with the fertilized egg. Some features of the life history of the sunflower are shown in Fig. 4.

FIG. 4.

A, transverse section of anther with four sporangia, each containing spores (pollen grains); B, sectional view of sporangium (ovule) containing the embryo-sac (g); antipodal cells (a); endosperm nucleus (e); synergids(s); egg (o); C, upper end of embryo-sac at time of fertilization; 1, pollen tube which has discharged its sperms; 7, remains of synergids; o, egg; one sperm s1 is fusing with the nucleus of egg and the other sperm, s2, is fusing with the endosperm nucleus, e.

Below the ferns, in the mosses and liverworts, the gametophyte and sporophyte generations alternate just as regularly, the fertilized egg being the first cell of the sporophyte and the spore produced by the sporophyte being the first cell of the gametophyte; but the sporophyte never becomes free from the gametophyte and, consequently, the existence of two generations is not so evident as in the ferns. The spore produces a branching filament called the protonema, upon which buds appear and develop into the familiar leafy moss plants. Upon the leafy plant, often at the top, antheridia and archegonia appear, containing respectively the sperms and eggs. The whole structure from the spore up to this point constitutes the gametophyte. A sperm fertilizes an egg which then develops into a stalk bearing a sporangium, called a capsule, within which spore mother cells appear, each giving rise to four spores, the spore being the first cell of a new gametophyte generation. The sporophyte begins with the fertilized egg and ends with the spore mother cell.

It will be noted that the two generations are more nearly equal than in the fern.

In the liverworts, the life history is essentially the same, but the protonema is inconspicuous or entirely lacking. The sporophyte is not so highly developed as in the moss, and, in the lower liverworts, the sporophyte is entirely included within the gametophyte. But here again the sporophyte begins with the fertilized egg and the gametophyte begins with the spore.

In plants below the liverworts, i. e., in the algæ and fungi, alternation of generations is easily recognized in many cases. In forms which have not reached the level of sexuality there is no alternation, but with the origin of sex, i. e., with the fusion of gametes, the sporophyte had its beginning. In many of these simple plants reduction of chromosomes occurs immediately after the fusion of gametes without the formation of any spores, no recognizable body being built up which could be called a sporophyte. As the interval between the fusion of gametes and the reduction of chromosomes became more prolonged, a recognizable body was formed, which in some cases looked like the gametophyte and in some cases looked different. When this body produces spore mother cells, each of which gives rise to four spores, practically all botanists admit that there is an alternation of generations. It must be admitted that the term sporophyte is a misnomer in those simple forms which do not produce spores, but the fundamental feature is this, that the fusion of gametes initiates a generation-long or short- which comes to a close with the reduction of chromosomes. Consequently, we should insist that the two generations are marked by the number of chromosomes, the sporophyte having twice as many as the gametophyte.

The sporophyte, at its beginning, is small and, in many cases, dependent upon the gametophyte; but higher in the scale it becomes independent and is the generation which we recognize as the plant. On the other hand the gametophyte in the early forms is the dominant generation which, higher in the scale, becomes dependent, and then more and more reduced until it can be seen only with the aid of the miscroscope. Here it is the sporophyte which we recognize as the plant. This evolution of the sporophyte and reduction of the

St...

FIG. 5.-8, spore; p, protonema; 1, leafy plant; st, stalk; c, capsule r, rhizoids.

gametophyte are among the most interesting phenomena of plants.

We believe that in animals, as well as in plants, there are two alternating generations. characterized by the number of chromosomes, but this belief is shared by only a few botanists

and, as far as we know, practically all zoologists oppose it.

Bibliography.- Bower, F. O., 'The Origin of a Land Flora' (Botanical Gazette, Vol. XXXIX, 1905, p. 137); Chamberlain, Charles J., 'Alternation of Generations in Animals from a Botanical Standpoint'; Lang, W. H., On Apogamy and the Development of Sporangia upon Fern Prothallia' (Philosophical Transactions, Royal Society of London, Vol. CXC, 1898, p. 187).

CHARLES J. CHAMBERLAIN,

Professor of Morphology and Cytology, University of Chicago.

ALTGELD, ält’gěld, John Peter, American politician: b. Germany, Dec. 1847; d. 12 March 1902. Brought to Mansfield, Ohio, in infancy, he received a public-school education; served in the Civil War as a private in the Union army, 1864-65; taught school in Missouri; became a lawyer there and county attorney of Andrew County in 1874. Removing to Chicago in 1875 he became prominent in the Democratic party. An unsuccessful candidate for Congress in 1884, he was judge of the Chicago Superior Court 1886-91. Elected governor in 1892, one of his first official acts was to pardon three anarchists, imprisoned since 1887 (two for life and one for 15 years) for complicity in the bomb-throwing which killed seven policemen in Chicago, 4 May 1886 (See ANARCHISM; HAYMARKET MASSACRE). It should be said that many leading United States citizens had petitioned for their release on the ground of insufficient evidence, an assumption which Judge Gary (q.v.) has vigorously repelled. Altgeld was governor till 1897. He was a prominent champion of free silver and an active supporter of Bryan for the Presidency in 1896 and 1900, and was defeated as independent candidate for mayor, 1899. He was an able speaker, an efficient advocate of prison reform, and appears to have been moved chiefly by sympathy with the working class. He wrote: Our Penal Machinery and Its Victims,' 'Live Questions,'

ALTHORP, Lord. See SPENCER.

ALTHUSIUS, Johannes, German philosopher: b. 1557; d. 1638. He was for many years professor of ethics and law at Herborn. He wrote the first treatise on politics ever produced in Germany. His system claimed that social life was based on a contract express or implied between men; he was thus the forerunner of Rousseau. He claimed that all rights proceed from the people and was quite outspoken against any usurpation of those rights. He included workingmen's unions or combinations among monopolies requiring regulation. He wrote 'Politicia Methodice Digesta' (Herborn 1603); Jurisprudentiæ Romanæ Libri' (ib., 1588); Dicæologica Libri tres Totum et Universum Jus, quo Utimur, Methodice Complectantes' (ib., 1617). Consult Gierke, Otto, Johannes Althusius (Breslau 1880).

ALTIMETRY, the art of ascertaining altitudes geometrically by means of a quadrant, sextant, or theodolite. The instrument so used is then known as an altimeter.

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ALTISCOPE, an instrument consisting of an arrangement of mirrors in a vertical framework, by means of which a person is enabled to overlook an object (a parapet, for instance) intervening between himself and whatever he desires to see, the picture of the latter being reflected from a higher to a lower mirror, where it is seen by the observer.

ALTITUDE, in mathematics, denotes the perpendicular height of the vertex of any plane or solid body above the line or plane of its base; thus the altitude of a triangle is measured by a perpendicular let fall from any one of its angles upon the base, or upon the base produced; therefore the same triangle may have different altitudes, accordingly as we assume one side or another for its base. Again, the altitude of a cone or pyramid, whether right or oblique, is measured by a perpendicular let fall from the vertex to the plane of its base. Similar remarks apply to other solids. In astronomy altitudes are measured or estimated by the angles subtended between the object and the plane of the horizon; and this altitude may be either true or apparent. The apparent altitude is that which is obtained immediately from observation; and the true altitude that which results from correcting the apparent altitude, by making allowance for parallax, refraction, etc. The altitude of a terrestrial object is the height of its vertex above some horizontal plane assumed as a base.

ALTITUDE AND AZIMUTH INSTRUMENT. Altitude, in astronomy, is the height of a heavenly body above the horizon, and is measured, not by linear distance, but by the angle which a line drawn from the eye to the heavenly body makes with the horizontal line, or by the arc of a vertical circle intercepted between the body and the horizon. The azimuth of a heavenly body is the angle measured along the horizon between the north or south point and the point where a circle, passing through the zenith and the body, cuts the horizon. An altitude and azimuth instrument consists essentially of a vertical circle with its telescope so arranged as to be capable of being turned round horizontally to any point of the compass. It thus differs from a transit instrument, which is fixed in the meridian. To take an altitude the telescope is directed toward the body to be observed, and the angle which it makes with the horizon is read off the graduated circle. The altitude thus observed must receive various corrections - the chief being for parallax and refraction-in order to get the true altitude. The azimuth - derived from an Arabic word signifying "a quarter of the heavens," is usually measured westward

from the point most remote from the elevated pole, beginning at 0° and returning to it at 36°. Thus, in northern latitudes, where the north pole is elevated, the azimuth is measured from the south point, so that the east point, for instance, has an azimuth of 270°.

ALTON, äl'ton, Ill., city in Madison County. on the Mississippi River and_on_the_Chicago & Alton, Cleveland, Cin., C. & St. L., C., B. & Q., C., P. & St. L., Illinois Terminal and Missouri & Illinois Bridge & Belt railroads, about seven miles above the mouth of the Missouri River and 25 miles north of St. Louis. Alton was settled early in the century, but was not in

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corporated as a city until 1837. The city, built upon a high limestone bluff, has very picturesque surroundings. Seat of Shurtleff Ĉollege, Monticello Seminary and Western Military Academy. Has 14 public and three parochial schools. Churches of all denominations. Alton has considerable river trade and is a distributing point for farm products. Large manufacturing district producing bottles, pig lead, strawboard, castings, tools, cartridges, stokers, mine cars, brick, sewer pipe, oil products, powder, flour, meat products, stone and sand. Annual value of manufactured products, $40,000,000. The city is governed by a mayor and common council, elected every two years by the people. There are two national and three savings banks and two daily newspapers. In 1837 Elijah P. Lovejoy, the abolitionist, was murdered here. A monument to his memory was erected in 1897. Pop. (1915) 25,000; including suburbs, 30,000.

ALTON LOCKE, a story by Charles Kingsley, published in 1850. It was his first novel, and displayed the author's broad sympathy for the condition of the English working classes. It excited immediate attention, and was an important factor in arousing the upper classes to a realization of their responsibilities toward the less fortunate. The altru

ism of Locke and his friends,. Crossthwaite, Mackaye, Lady Ellerton and Eleanor, forms an admirable and inspiring feature of the book.

ALTONA, äl'to-na, Germany, a town in the Prussian province of Schleswig-Holstein, on the Elbe, immediately west of Hamburg. It has spacious squares and streets, which are embellished by several monuments, notably the memorials of the wars of 1864 and 1870. There are fine municipal and judicial buildings, a theatre, a gymnasium, technical schools, a school of navigation and a hospital. It has manufactures of tobacco and cigars, of machinery, woolens, cottons and chemicals. There are also extensive breweries, tanneries and soap and oil works. It has an extensive maritime trade, but its neighbor, Hamburg, is easily its commercial superior. Pop. 168,301.

ALTOONA, ǎl-too'na, Pa., city in Blair County, on the Pennsylvania Railroad, 118 miles east of Pittsburg. It has an elevation of 1,182 feet above the sea; situated in the midst of a most picturesque mountain region, at the eastern base of the Alleghany Mountains. For many years Altoona has been regarded as the most typical of American railroad towns, for here are located the immense machine shops of the Pennsylvania Railroad, the largest railroad shops in the world, where over 17,000 workmen are engaged in manufacturing and repairing locomotives, passenger coaches and freight cars. The normal output from the shops is five engines a week. There are also silk mills, planing mills, a bar iron plant, brick and tile works and other important manufactories of machinery, agricultural implements, etc. According to 1917 estimate of manufactures there were in that year 70 establishments of factory grade employing 19,165 persons, of whom 16,971 were wage earners, receiving a total of $20,301,165 in wages and salaries. Altoona is centrally situated in a bituminous coal region and is also the business centre of a considerable agricultural region. The city has an excellent school sys

tem, a fine high school and many private schools. Among its 52 churches are many handsome buildings. It has three banks and three trust companies with a combined capital of over $1,000,000; a public library building and several hospitals. The famous Horseshoe Bend, on the line of the Pennsylvania Railroad, is located near the city, and Lakemont Park is a well-known pleasure ground in Logan township. The city owns the water-works plant, which was acquired in 1872 at a cost of $680,000, and upon which $97,000 is expended annually. The city's expenses aggregate $565,000 yearly, of which amount about $280,000 is expended for schools, $50,000 for the police department and $20,000 for municipal lighting. The city was founded in 1850 by the Pennsylvania Railroad Company. It was first incorporated as a borough in 1854, and chartered as a city in 1868. The commission form of government was adopted in 1914. During the great railroad strike of 1877 Altoona was the centre of the disturbed section and troops were ordered out to protect railroad property here. It is a growing, thriving city. There are three daily and numerous weekly newspapers. Pop. (1910) 52,127; (1916) 60,000.

ALTOONA, or ALLATOONA PASS, a mountain pass in northern Georgia, the scene of a sharp engagement between the Federal troops under General Corse and the Confederates commanded by General French, on 5 Oct. 1864. The losses on each side were about equal.

ALTO-RELIEVO, äl'tō-rě-lyā'vō (Ital. "high relief"), the term applied to sculpture that projects from the plane to which it is attached to the extent of more than one-half the outline of the principal figures.

ALTRICES, birds that are hatched from the egg before they have acquired feathers or the ability to care for themselves. Hence they must remain in a nest and be protected and fed by the parents. This division, also called Nidicolæ, includes all birds except those known as game-birds and seafowl.

ALTRINCHAM, äl'tring-ăm, or ALTRINGHAM (and so pronounced), England, a town in Cheshire, eight miles southwest of Manchester. Many residences are occupied by those whose business is in Manchester, who are attracted by the healthful climate and the vicinity of Bowdon Downs and Dunham Massey Woods. Market gardening is carried on, large quantities of fruit and flowers being grown for sale in Manchester. Cabinet-making is also practised, and there are saw-mills, iron foundries and manufactures of cotton, yarn and worsted. Pop. 16,831.

ALTRUISM, a term in psychology and ethics to denote disposition and conduct directed toward the well-being of others. It is contrasted with egoism, or self-seeking disposition and conduct. It is essential to altruism, as well as to egoism, that the good of others, or of self, should be consciously and intentionally pursued. Actions and dispositions which are instinctive, such as maternal instinct, are not, properly speaking, altruistic, nor are the opposite egoistic. It is only when the consciousness of self is sufficiently developed in the child to give rise to a contrast between self

and the "other" (alter), that the conscious pursuit of the interest of one of them is possible. This is covered by psychologists by saying that real altruism and egoism are always "reflective." Altruism is also applied to the type of ethical theory which bases morality upon generous or altruistic disposition or conduct (in the sense defined above).

ALTSHELER, ält'sha-ler, Joseph Alexander, American author and journalist: b. Three Springs, Ky., 29 April 1862. He studied at Vanderbilt University and has been connected with the Louisville Courier-Journal and the New York World. His numerous novels are chiefly on American historical subjects and among them are The Sun of Saratoga' (1897); A Soldier of Manhattan' (1897); 'The Last Rebel' (1899); 'In Hostile Red" (1900); In Circling Camps' (1900); 'My Captive' (1902); The Wilderness Road (1901); The Candidate) (1905); The Forest of Swords' (1915); The Hosts of the Air' (1915); The Guns of Europe' (1915).

ALTUS, Okla., city and county-seat of Jackson County, 145 miles southwest of Oklahoma, on the Saint Louis and San Francisco, the Kansas City, Mexico and Orient and other railroads. It contains flour, oil and alfalfa mills. Stock raising and truck farming are important industries of the surrounding district. The city owns the electric plant and the waterworks. Pop. 5,200.

ALTWASSER, ält'väs-ĕr, Germany, town in Silesia, 43 miles southwest of Breslau. It has factories for glass, porcelain, machinery, cotton-spinning, iron foundries and coal mines. Pop. (1910) 12,144.

ALUM, in chemistry, a general name for a large class of substances, which may be defined as double sulphates or selenates, in which one of the bases is aluminum, chromium, manganese, iron, indium or gallium, and the other is sodium, potassium, rubidium, cæsium, ammonium, silver or thallium. The alums all crystallize in cubes or octahedra, with 24 molecules of water, and are all isomorphous, so that when in solution together they cannot be separated by crystallization. In naming them aluminum is understood to be one of the metals present unless the contrary is expressly indicated. Thus "potash alum" is the alum whose formula is Al2(SO4)2 + K2SO. + 24H2O. aluminum is not present, the metal that replaces it is stated; thus "iron-sodium alum" is the alum whose formula is Fe2(SO1),+ Na2SO.+24H2O. When selenium replaces the sulphur in one or both of its positions, the alum is most clearly identified by giving its formula. In addition to the true alums a class of substances known as "pseudo-alums" exists. These also crystallize with 24 molecules of water, but they are not isomorphous with the true alums. Mn2(SO4)3 + MgSO. + 24H2O is an example of this class.

If

All the alums are soluble in water, and it is probable that all are resolved, at least partially, into their constituents, by solution. It is known that in certain cases (in silver alum, for example) the separation is absolute. All of the alums give an acid reaction when in solution, all have an astringent taste and all lose their water of crystallization when heated.

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The alum of commerce is assumed to be potash alum, the formula of which has been already given. Ammonia alum (NH)SO.AL, O3(SO3)324H2O — is sometimes substituted, however, owing to the cheapness of sulphate of ammonia, which is now obtained as a byproduct in the manufacture of illuminating gas. Sodium alum is probably not substituted for potash alum to any great extent.

The alums are largely used in the arts, especially in dyeing and tanning, and in the purification of water. Potassium alum is also used with borax in waterproofing cloth and with lime in preserving timber; in the size used in paper making; and as a soap precipitant in the manufacture of glycerine. Bread made from flour containing a small amount of alum is said to be very white, and partly for this reason and partly on account of the cheapness of the substance, ammonia alum has been largely used in the manufacture of baking-powders. This practice has been condemned and pronounced detrimental to health, however, by nearly all the authorities who have written on the subject.

Commercial alum is made from alum stone (see ALUNITE), from alum shale, or from bauxite and cryolite, generally by roasting. It is also made in greater purity by mixing solutions of the sulphates of alumina and potassa and allowing the alum to crystallize out. In making ammonia alum, sulphate of ammonia is substituted for the potassium sulphate (see ALUNITE). Some alums occur native. (See MENDOZITE; TSCHERMIGITE.) The United State census of 1914 reported 19 establishments making alums, with a total output of 313,712,000 pounds, valued at $3,467,969, an increase over 1909 of 37,418,000 pounds, and $445,614. Of the 19 establishments, 5 were located in Pennsylvania, 3 each in Illinois, Massachusetts and New York, 2 in Michigan and 1 each in California, Connecticut and New Jersey. The output comprised 142,438,000 pounds reported as aluminum sulphate, valued at $1,277,836; 23,338,000 pounds of alum cake, valued at $251,186; 42,562,000 pounds of concentrated alum, valued at $450,730; 22,629,000 pounds of burnt alum, valued at $364,656; 12,765,000 pounds of potash alum, valued at $219,968; 13,995,000 pounds of soda alum, valued at $254,477, and 55,985,000 pounds of other alums, designated as porous alum, excelsior alum, pearl alum, ammonium alum and chloride of alumina, valued at $649,116.

Alum Poisoning. This poisoning may be acute or chronic, the latter being much more common. In the acute variety, often the result of accidental drinking of a gargling solution, the symptoms are nausea, vomiting, purging, cold clammy skin, small thready pulse, thirst, muscular tremor, followed by a rise in temperature in those that have recovered. The treatment pursued in the case of alum poisoning is to wash out the stomach and use the white of eggs as a chemical antidote.

Alum being so widely employed as a preservative, as a means of clarifying water and as an adulterant in baking-powders, the question of chronic alum poisoning becomes of great importance. The symptoms that have been most frequently observed in such poisoning are disturbances of digestion and constipation. The question as to its harmful action

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ALUMBAGH

on the kidneys is not yet decided, but it would seem to be harmful rather than the reverse.

ALUMBAGH, a domain in India formerly belonging to one of the princes of Oudh, about four miles south of Lucknow, near the road to Cawnpore. It comprised a beautiful palace, a mosque, a temple and other buildings surrounded by a garden, all in the centre of a magnificent park enclosed by a lofty wall with turrets at each angle. On the outbreak of the Indian mutiny this place was occupied by the revolted Sepoys and converted into a fort. On 23 Sept. 1857 it was captured by the British, then on their way to relieve Lucknow. Leaving a garrison of 300 European troops, together with the sick and wounded and about 4,000 native camp-followers, the main body, under Outram, Havelock and Neil, pushed on to Lucknow. These generals were unable to send reinforcements, but at the end of November the place was relieved by Sir Colin Campbell. The latter left Sir James Outram, with a force of 3,500 men, to hold the Alumbagh, a task which he successfully accomplished, though repeatedly attacked by overwhelming numbers of the rebels. In March 1858 the garrison was finally relieved. At the foot of a tree within the grounds Sir Henry Havelock was buried.

ALUMINA (Al2O3), the only oxide of the metal aluminum. As found native, crystallized, it is only second to the diamond in hardness. The transparent varieties are the sapphire and ruby, the opaque are corundum and emery, only the corundum being pure. In combination with silica it is one of the most widely distributed of substances, ranking in this respect next to oxygen and silicon. It enters in large quantity into the composition of granites, traps, slates, schists, clays, loams and other rocks. The hydrated oxide, Al2O3. H2O, occurs as disapore, and with ferric oxide as bauxite. Various aluminates occur in certain gems, as in spinel and chrysoberyl. Alumina may be obtained by adding a solution of ammonium hydrate to purify alum dissolved in 20 parts of water, thoroughly washing the very gelatinous precipitate formed, and then drying it carefully. It may also be prepared by igniting powdered aluminum in air or oxygen. Alumina is a white powder, without taste or smell, and infusible except in the oxyhydrogen flame. It is the basis of porcelain, pottery, bricks and crucibles; and it has a strong affinity for oil and coloring matter, which causes it to be employed in the state of clays as a cleansing powder, and in a state of purity in the preparation of the colors called lakes, in dyeing and calico-printing. It combines with the acids, and forms numerous salts, the most important of which are the sulphate (see ALUM) and the acetate. The latter salt is formed by digesting strong acetic acid (vinegar) with the newly precipitated earth; but for the use of the manufacturer, by decomposing alum with acetate of lead (sugar of lead), or more economically with acetate of lime, a gallon of which, of the specific gravity, 1.050, is emploved for every 234 pounds of alum. The sulphate of calcium formed falls to the bottom, and the acetate of aluminum remains in solution with an excess of alum, which is necessary to prevent its decomposition. It is of extensive use in calico-printing and dyeing, as a

mordant, and is employed in the place of alum, to which it is generally preferred.

ALUMINITE, a mineral having the composition of a hydrous aluminum sulphate, Al:O3. SO..9HO, occurring in white reniform concretions in beds of clay in Germany, England and other European countries. It is opaque, of earthy lustre and. fracture, and is sift and light.

ALUMINO-THERMICS, a term designed to embrace the processes of reduction of metals by taking advantage of the intense affinity for earthy lustre and fracture, and is soft and light. temperatures.

The principal industrial applications of these. processes are: (1) The welding of iron and steel in place as in the uniting of railroad rails, and in repairing broken shafting and the like; (2) the production of pure metals and alloys free from carbon, nitrogen and other common impurities; (3) in foundry practice for reviving or increasing the temperature of molten iron or steel in the ladle before pouring; (4) in the manufacture of small castings and repairing flaws in large ones; (5) in surface softening of hardened steel to permit tooling or boring and the cutting of large openings.

In the welding process the aluminum is reduced to a powder or granulated and mixed with a metallic oxide, in most cases the oxide of iron. This mixture has been given the commercial name "thermit."

The chemical reaction, which consists in oxidizing the finely divided aluminum, is started by producing the high temperature necessary at only one point in the thermit. This is accomplished by a priming powder composed preferably of metallic magnesium and barium peroxide. The primer is ignited by a fiercely burning storm match or by touching it with a red-hot iron rod. The reaction then spreads spontaneously and with great rapidity and with considerable violence. In a few seconds the entire mass is a white-hot fluid at a temperature estimated to be about 5400° F.

In the crucible after the reaction there are two layers. The bottom one is pure metal of equal weight to, but occupying only one-third of the space of, the top layer, which is now oxide of aluminum, so-called corundum.

The most commonly employed of the welding processes is the one by which a continuous rail—a desideratum in modern trolley-road construction is simply, cheaply and effectively obtained. The marked advantage enjoyed by this system is the freedom from bulky equipment; a crucible, a mold box and, in instances where a complete butt weld of the head of the rail is desired, a rail-clamp is all that is required. All these materials, including the necessary quantity of thermit, can easily be moved on a hand truck. Each weld, according to the section, requires from 15 to 20 pounds of thermit, and the metal welded around the joint will only weigh, therefore, from 8 to 10 pounds.

The thermit reaction takes place in a crucible which rests on a simple iron stand that can be attached to the rails or rail-clamps where such are used. The crucible consists of a sheet-iron mantle lined with magnesia or corundum slag, which is tamped round a sheet-iron conus suspended in its middle. The bottom is formed by a hard magnesia stone provided with a replaceable outlet which will stand 9 or 10 runs.