7 Argus, ẞ Lyræ, &c., show the lines of hydro- | gen bright instead of dark, as though surrounded by hydrogen glowing with a heat more intense than that of the central orb itself around which the hydrogen exists. Secchi's observations were comparatively rough, and the inference that particular lines, as those of hydrogen for example, are really present depended in his case simply on the general correspondence of a set of lines with the set belonging to the element. But Huggins and Miller, in Eugland, showed, by the direct comparison of stellar with terrestrial spectra, that certain elements exist in particular stars. Thus they found in the spectrum of Aldebaran lines corresponding with those of hydrogen, sodium, magnesium, iron, tellurium, calcium, bismuth, antimony, and mercury. In the spectrum of Betelgeuse they recognized the lines of sodium, magnesium, iron, bismuth, and calcium, but found those of hydrogen wanting. They discovered that (at least in the instances examined by them) the colors of the double stars are due to the existence of stellar atmospheres exercising an elective absorption. For example, the spectrum of the orange component of the well known double star Albirco shows dark bands in the blue and violet; while the spectrum of the blue component shows many strong lines in the orange and red.-The nebulæ show

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sunlight. Tempel's comet (1866) was the first analyzed with the spectroscope, by Huggins in England. Winnecke's (1868) was the first to which careful analysis was applied, with the curious result of observing that the bands agree in position with those obtained as the spectrum of carbon, by passing the electric spark through olefiant gas. Huggins obtained the same result (which was confirmed by Professors Harkness and Young in America) from the study of Encke's comet in 1872. The first large and long-tailed comet studied with the spectroscope was Coggia's comet of 1874. Huggins gives the following account of the spectroscopic analysis of this comet: "When the slit of the spectroscope was placed across the nucleus and coma, there was seen in the instrument a broad spectrum, consisting of the same three bright bands exhibited by comet II., 1868, crossed by a linear continuous spectrum from the light of the nucleus. On the continuous spectrum of the nucleus I was not able to distinguish with certainty any dark lines of absorption, or any bright lines, other than the three bright bands. Besides these spectra, there was also present a faint broad continuous spectrum between and beyond the bright bands. When the slit was moved on to different parts of the coma, the bright bands and the faint continuous spectrum were found

two orders of spectra. One class, including the clusters, resolvable and suspected resolvable nebulæ, besides other nebula which probably are resolvable into stars though no signs of the fact can be detected with the telescope, show a spectrum resembling the stellar spectrum in general characteristics, though usually too faint to be assigned to any given order of stellar spectra. The other class, which includes all the irregular and planetary nebulæ, besides most of the elliptic irresolvable nebulæ, the ring nebula in Lyra, the dumb-bell nebula, and others, presents the remarkable phenomenon of a spectrum of three bright lines (in a few cases four lines are seen). Fig. 5 is the spectrum of the nebula known as H 4,374. This is a small but bright object, and it is the nebula to which Huggins in 1864 first directed his telespectroscope. One line agrees in position with a hydrogen line, another with a nitrogen line, but the third line has not yet been shown to coincide with a line of any known element.-Comets show a mixed spectrum, the nucleus, coma, and tail each giving a combination (though in varying proportions) of a discontinuous or band spectrum, and a continuous spectrum due probably to reflected

to vary in relative intensity. When the slit was brought past the nucleus on to the commencement of the tail, the gaseous spectrum became rapidly fainter, until, at a short distance from the nucleus, the continuous spectrum predominated so strongly that the middle band only, which is the brightest, could be detected on it."-The planets, shining by reflected light, can only reveal under the spectroscope the possible presence of absorptive vapors in their atmosphere. (See MARS.)

SPECULUM (Lat., mirror), a term commonly applied to concave metallic reflectors, such as are used in reflecting telescopes for concentrating the rays of light from distant luminous bodies, and presenting the image of these in their focus. Their perfection consists in large surface, whereby they collect the greatest quantity of light; in the highest possible polish, whereby it is reflected with least loss; and in the most exact parabolic curvature, rendering the image distinct and precise. In a speculum of 6 ft. diameter, a variation even at its edge from the true parabolic curvature, so minute as to escape detection with any except the most refined means of measurement, may render the whole useless. The metallic alloy best adapted for the requirements of specula was first employed for this purpose by Sir Isaac Newton, and is similar to that used by the ancient Egyptians for mirrors.

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small specula had previously been successfully polished. The principles of the arrangement of Mr. Lassell were so mathematically exact, that, as stated by Mr. Nasmyth, "a speculum having a decidedly hyperbolic figure may be corrected and brought to a perfect parabola, or to a spherical curve, or the same may be done in the reverse order at pleasure." The test of the polishing consists in observing through an eye piece the reflection of the dial of a watch set directly over the speculum, in the case of Lord Rosse's operations at the height of 90 ft. The success of the polishing was dependent on the state of the atmosphere as regards temperature and moisture, both of which required at times to be artificially regulated. The tools for first smoothing the face of the speculum are made up of pieces of gritstone, cemented together in a frame and dressed on the face to the proper degree of convexity. The next are disks of cast iron, their face also of the exact curvature, and grooved by two lines of furrows a quarter of an inch wide and the same deep, crossing each other at right angles. These are fed with sharp quartz sand, and afterward with emery and water. When the work has proceeded to the use of very fine emery the scratches disappear, and the rubber is in perfect and uniform contact with the speculum. For polishing, the cast-iron rubber was used by Lord Rosse, counterpoised and provided with circular grooves in addition to the rectilinear ones. Its face was coated with a thin layer of pitch, with another upon this of rosin and flour, which serves as the bed for the polishing powder or rouge to imbed itself. Mr. Lassell's polisher was of pine wood in two layers, the grain crossing, and the face coated with pitch above. The preparation of these polishers involves nice operations, which may not be neglected without great risk of failure. The largest specula when polished ought never to be removed from their supports; for how ever carefully lifted, the figure would be almost certain to lose its accuracy by change of pressure in the mass. Even one of 9 in. diameter, when supported by the pressure of springs against three stops bearing on its edges, loses its defining power. Sir John Herschel laid the speculum upon folds of woollen cloth, packing others closely all around it, filling the space between its edges and the box that contained it; but this is not sufficient to preserve the form of the specula of 6 ft. diameter and as many inches thick, and the contrivances for this are a most complicated system of bearings, springs, and levers.-Specula exhibit some peculiarities in their forms and applications to use, according to the kind of reflecting telescope for which they are designed. It is evident that as they reflect images as mirrors, the observer cannot be placed directly in front, and it is not obvious how he can take his position at the opposite end of the telescope, as in using those of the refractory kind. This is accomplished in the reflecting telescope of Dr. James

Gregory, known as the Gregorian telescope, by an aperture through the centre of the speculum, and the introduction of a small concave speculum in the centre of the great tube, facing the large speculum, and a little in advance of its focus. Back of the great speculum the tube is extended of reduced diameter, and in its extremity is a magnifying eye piece, by which the image reflected from the small speculum through the aperture of the large one reaches the eye. In Sir William Herschel's great telescope, with its 4-ft. speculum and 40-ft. focal length, the disk was entire, and the image was reflected direct to an eye piece at the mouth of the tube and near one side of it, so as not to intercept too much light. This was effected by a slight inclination of the plane of the speculum. In Sir Isaac Newton's telescope the disk was also entire, and a small plain speculum reflected the cone of rays sent from it, before meeting in the focus, to the eye piece placed in the upper side of the tube. Cassegrain's telescope differs from Gregory's in the small reflector being convex instead of concave.-Specula have recently been made of polished silver surface, which has the advantage over that of the speculum metal of reflecting 91 per cent. of the incident light, instead of 67 per cent. The silver, after the method of M. Léon Foucault, is laid in a very thin uniform coating upon a speculum of glass, figured and polished to a true parabola. This is done by Drayton's process of precipitating the metal from the solution in nitric acid by oil of cassia. The precipitated silver is polished by gentle rubbing with a skin lightly tinged with oxide of iron, and soon acquires a very brilliant lustre without material change of figure. This, however, was questioned by Mr. Grubb, when the subject was under consideration before the British association at Dublin, who asserted from his own experience that the removal of a thickness of 10.00 or 0.7 of an inch might seriously impair the accuracy of the defining power of the speculum. M. Foucault had preserved the silver mirrors for eight months without their being injured by tarnishing; but whenever this might occur they were easily polished again, and the silver itself could be at any time renewed. Mr. Browning of London has carried to a high degree of perfection the construction of silvered-glass reflectors; and the experience of those acquainted with instruments constructed on his plan is strongly in favor of the method. In America the reflecting telescope has not hitherto met with much favor; though the success with which Dr. H. Draper of New York has constructed large reflecting telescopes, and employed them even in the delicate work of lunar photography, promises before long to enlist American ingenuity in the improvement of a class of telescopes which must probably always have the preference over refractors for observations requiring very great space-penetrating power.-The subject of the speculum, in its

mathematical and mechanical details, is treated in various memoirs in the English scientific journals, from the time of Newton's paper in the "Philosophical Transactions" of 1672 to the present day. Lord Rosse's papers are contained in the "Edinburgh Journal," vol. ix., 1828, and vol. ii. (new series), 1829, and in the Philosophical Transactions," 1840 and 1850. The mechanical details are fully described in Holtzapffel's "Mechanical Manipulations." For Lassell's process, see "Transactions of the Royal Astronomical Society," 1849.

SPEKE, John Hanning, an English traveller, born in Somersetshire, May 4, 1827, died near Bath, Sept. 15, 1864. He served as a captain in the British army in the Punjaub under Lord Gough (1849), and subsequently made scientific explorations in the Ilimalaya. In 1854 he set out with Burton for the Somauli country, where they were attacked and Speke was wounded. He next enlisted in the Turkish army in the Crimea shortly before the close of the war. He gained a wide celebrity by his joint expedition with Burton (1856) to Africa, and the discovery of Lake Tanganyika. (See BURTON, RICHARD FRANCIS.) On July 30, 1858, he discovered alone the Victoria N'yanza lake, and in 1862 he explored its western and northern margin together with Capt. J. A. Grant. (See NILE, and N'YANZA.) Capt. Speke was killed by the accidental discharge of a gun while hunting. His principal work is his Journal of the Discovery of the Source of the Nile" (2 vols., London, 1863).

SPELMAN, Sir Henry, an English antiquary, born at Congham, near Lynn, Norfolkshire, in 1562, died in London in 1641. He was educated at Cambridge, and devoted himself to historical and antiquarian studies. He served as sheriff of his county, and was knighted by James I. and appointed commissioner to determine disputed claims to lands and manors in Ireland. In 1612 he settled in London. He wrote Glossarium Archaiologicum (A to L, 1626; completed from his manuscripts, 1664; best ed., 1687); Concilia, Decreta, Leges, Constitutiones, in Re Ecclesiastica Orbis Britannici (2 vols., 1639-'64); and Villare Anglicanum (1656). The Reliquia Spelmanniana (fol., Oxford, 1698) is a collection of his papers relating to the laws and antiquities of England. SPENCE, Joseph, an English author, born at Kingsclere, Hampshire, April 25, 1699, drowned at Byfleet, Surrey, Aug. 20, 1768. educated at Oxford, entered holy orders, and was elected professor of poetry. He published in 1726 "An Essay on Pope's Odyssey," and made a tour through France and Italy in 1730-'33. In 1731 he published a biography of Stephen Duck, afterward prefixed to an edition of Duck's poems, and in 1736 reproduced with a preface at Pope's request Sackville's tragedy of "Gorboduc." In 1742 he was presented by his college to the rectory of Great Horwood, and appointed professor of modern history at Oxford. His most in

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teresting production is "Anecdotes, Observations, and Characters of Books and Men," collected from the conversation of Pope and others, and valuable with reference to the literary history of his time. It was published, with notes and a biography, by S. W. Singer (London, 1820; new ed., 1858).

SPENCE, William, an English entomologist, born in 1783, died in London, Jan. 6, 1860. In 1805, while engaged in business at Hull, he presented a few specimens of insects to the Rev. William Kirby, with whom he afterward wrote "Introduction to Entomology, or Elements of the Natural History of Insects" (4 vols., 1815-26; 7th ed., 1 vol., 1858). It consists of 51 letters, of which 9 were written by Mr. Spence, 20 by Mr. Kirby, and 22 by them conjointly. He was for a time a member of parliament. He removed in 1826 to the continent, and visited the principal European capitals during the next eight years, returned to England and settled in London.

SPENCER. I. A N. county of Kentucky, intersected by Salt river; area, 280 sq. m.; pop. in 1870, 5,956, of whom 1,479 were colored. The surface is hilly and the soil fertile. The chief productions in 1870 were 105,211 bushels of wheat, 16,470 of rye, 436,875 of Indian corn, 35,885 of oats, 1,852 tons of hay, 5,500 lbs. of tobacco, 15,385 of wool, 119,748 of butter, and 8,488 gallons of sorghum molasses. There were 3,018 horses, 538 mules and asses, 1,935 milch cows, 3,252 other cattle, 4,530 sheep, and 17,724 swine; 6 flour mills, and 4 distilleries. Capital, Taylorsville. II. A S. W. county of Indiana, bordering on the Ohio river, bounded E. by Anderson's creek and W. by Little Pigeon creek; area, 390 sq. m.; pop. in 1870, 17,998. The surface is hilly in the W. part and level in the S., and the soil is fertile. Bituminous coal is abundant. The chief productions in 1870 were 123,663 bushels of wheat, 682,374 of Indian corn, 98,510 of oats, 79,597 of potatoes, 7,878 tons of hay, 3,019,970 lbs. of tobacco, 21,416 of wool, and 49,006 gallons of sorghum molasses. There were 4,892 horses, 683 mules and asses, 3,711 milch cows, 5,720 other cattle, 14,054 sheep, and 23,506 swine; 5 manufactories of carriages and wagons, 5 of furniture, 2 of tobacco and snuff, 10 flour mills, 6 saw mills, and 3 planing mills. Capital, Rockport.

SPENCER. İ. Ambrose, an American jurist, born at Salisbury, Conn., Dec. 13, 1765, died at Lyons, N. Y., March 13, 1848. He graduated at Harvard college in 1783, studied law, and commenced practice in Hudson, N. Y. In 1793 he represented Columbia co. in the state legislature; in 1795 and for seven consecutive years he was a state senator; in 1802 he was appointed attorney general, in 1804 made a justice of the supreme court, and in 1819 chief justice. He was a member of the constitutional convention of 1821, and was the author of the law abolishing the punishment of death in all cases except treason and murder. He resigned the office of chief justice in 1823, and

resumed practice at Albany. He was for some years mayor of that city, and also represented the Albany district in congress. In 1839 he retired to Lyons. II. John Canfield, an American jurist, son of the preceding, born in Hudson, N. Y., Jan. 8, 1788, died in Albany, May 18, 1855. He graduated at Union college in 1806, and in 1807 became private secretary of Gov. Tompkins. He was admitted to the bar in Canandaigua in 1809, was master in chancery and district attorney, a member of congress 1817-'19, and several times of the state assembly and senate. In 1827 he was appointed one of the revisers of the statutes of the state, and in 1839 secretary of the state of New York. President Tyler in 1841 appointed him secretary of war, and in 1843 transferred him to the treasury department. He resigned in 1814, from opposition to the annexation of Texas. He served on many state commissions, and aided in the organization of the asylum for idiots and the improvement of the common school system. He edited De Tocqueville's "Democracy in America," with an original preface and notes (New York, 1838).

SPENCER. I. George John, second Earl Spencer, an English bibliophile, born Sept. 1, 1758, died Nov. 10, 1834. Under the courtesy title of Viscount Althorp, he was first lord of the admiralty from 1794 to 1801, and subsequently home secretary. On the death of his father in 1821 he took his seat in the house of lords. He possessed one of the largest and most remarkable private libraries in Europe, the nucleus of which he acquired in 1789 from the Hungarian baron Reviczky. See Dibdin's Bibliotheca Spenceriana (4 vols. 8vo, 1814 '15), and Edes Althorpiana (2 vols., 1822). II. John Charles, third Earl Spencer, an English statesman, son of the preceding, born May 30, 1782, died at Wiseton hall, Nottinghamshire, Oct. 1, 1845. He served in the house of commons as Viscount Althorp, during the whig administration of 1806-'7 was junior lord of the treasury, and afterward a leader of the whig opposition until the return of the whigs to power in 1830, when he was appointed chancellor of the exchequer, and became ministerial leader in the house of commons, through which he was instrumental in carrying the reform bill and the poor-law amendment bill. He resigned with his colleagues in November, 1834. About the same time he succeeded his father as Earl Spencer, and devoted himself to farming. He was the first president of the royal agricultural society.

SPENCER, George (Father Ignatius of St. Paul), an English clergyman, youngest son of John George, second Earl Spencer, born in London, Dec. 21, 1799, died at Carstairs, Scotland, Oct. 1, 1864. He graduated at Cambridge in 1819, took orders, and became rector of the family living of Brington in 1825. He joined the Roman Catholic church at Leicester in 1830, was ordained priest in 1832, and took charge of the missions of West Bromwich and

Dudley. In 1839 he was appointed to an office in Oscott college, became soon afterward its rector, entered the order of Passionists in 1846, and contributed very much toward the extension of his order in Great Britain and Ireland, filling high offices therein till his death. He was chiefly distinguished for his extraordinary zeal in ministering to the spiritual wants of the laboring population, and for his efforts in establishing an association of prayers for the return of England to communion with the church of Rome. For this purpose, from 1838 till 1857, he repeatedly visited Ireland and the Roman Catholic countries on the continent, preaching and lecturing everywhere on this subject. He wrote "Account of my Conversion" (1831), an autobiography and journal embodied by Father Pius in his "Life of Father Ignatius of St. Paul, Passionist" (Dublin and London, 1866), and a "Life of St. Paul of the Cross" (London, 1875).

SPENCER, Herbert, an English philosopher, born in Derby, April 27, 1820. His father was a teacher. Herbert was fond of keeping insects and watching their transformations, and for years the finding and rearing of caterpillars, the catching and preserving of winged insects and making drawings of them, were his regular occupations. He also assisted his father in philosophical experiments. At the age of 13 he was sent to study with his uncle, the Rev. Thomas Spencer, rector of the parish of Hinton. Here he remained three years, and made special progress in mathematics. Returning home, he studied perspective with his father, on the principle of independent dis. covery, the successive problems being put in such order that he was enabled to find out the solutions himself. This was a favorite mode of teaching with his father, who is the author of a valuable little work entitled "Inventional Geometry," on this plan. At 16 IIerbert devised a new and ingenious theorem in descriptive geometry, which was published with the demonstration in the "Civil Engineers' and Architects' Journal." At 17 he accepted an engagement under Charles (afterward Sir Charles) Fox as a civil engineer, and began work on the London and Birmingham railway. In 1841 he declined a further appointment, returned home, and spent two years in mathematical and miscellaneous studies. He made a botanical press and a herbarium, and practised drawing and modelling. All the time he had in progress some scheme of invention, improvements in watchmaking, machinery for the manufacture of type by compression of the metal instead of casting, a new form of printing press, and the application of electrotype to engraving, afterward known as the glyptograph. In the spring of 1843 he went to London in quest of literary occupation, but did not succeed, and resumed engineering. His earliest literary contributions were made to the "Civil Engineers' and Architects' Journal," the "Philosophical Magazine," the "Zoist," and the "Noncon