with the kind of vessel, and state of its surface; but the temperature of the steam or yet uncondensed vapor freely arising from it does not vary with these latter conditions, but in strict relation with the pressure merely. Hence, to find the boiling point, the instrument is next immersed, not in boiling water, but within the steam freely escaping from it (the best apparatus for the purpose being that of Regnault), and when the barometer shows a fixed atmospheric pressure of 29.92 inches of mercury. In this also the instrument remains until the glass and mercury have throughout acquired the temperature of the steam; then, their expansions being completed, and the column ceasing to vary, the height is marked as before. If the barometer indicates any other pressure than that above given, a correction must be made, and the true boiling point marked higher or lower than that shown at the time; the correction being by a space corresponding to 1° F. for every .59+ inch of the barometer. The different thermometric scales are readily reducible to each other; rules for the reductions most commonly required, representing any given number of Fahrenheit degrees by F°, of centigrade degrees by C°, &c., are thus briefly expressed: To reduce

Co.

Fahrenheit to Centigrade....... 5 (F-82) Centigrade to Fahrenheit....... C° +32 Fahrenheit to Réaumur........ 4 (F° -32) Réaumur to Fahrenheit........ 4 R° +82 = Fo. -The principal sources of error in the mercurial thermometer, and inseparably connected with the instrument, however accurately constructed, arise from the inequality of caliber of the tube, and of the expansions of the mercury and glass. The caliber probably always varies slightly in different parts of the tube, beside that, from the usual method of drawing out the tubes, it is likely to be in form a very much elongated hollow cone. Hence, to make a standard or highly perfect thermometer, it becomes necessary in the outset to place the tube upon the carriage of a dividing engine for rectilinear scales (briefly alluded to under DrVIDING ENGINE, and of which that by Duboscq, of Paris, is the best now made), and moving through the tube a short column of mercury, to mark on it, by means of a small microscope with cross wires, and the graver of the instrument, the lengths of this column in the different parts. This process is the calibration of the tube. Dividing all these lengths with reference to some arbitrarily assumed number of degrees, or rather parts, a new and wholly arbitrary, but (for the caliber) perfect scale, is obtained; exposing to the vapor of hydrofluoric acid, the marks of the graver are more plainly etched upon the tube; and it is then verified by recurring to the use of the engine. The arbitrary degrees are then to be reduced to degrees of the scale required, and these being properly marked, and of course differing in length in different parts, a standard instrument is obtained. For a more full statement of the

mode of calibration, see Professor J. P. Cooke's "Chemical Physics," vol. i. (Boston, 1860), or the original memoirs of Regnault, Mémoires de l'institut, vol. xxi. pp. 239, 328. Still, the rise observed in a thermometer tube is not the absolute expansion of the mercury, but the relative expansion, or difference between the increase of volume of the mercury and of capacity of the bulb and tube. Mercury expanding about 7 times more than glass, its relative is about less than its absolute expansion. Again, in view of the fact merely that mercury expands more rapidly at higher temperatures, the lengths of the degrees forming the scale should increase slightly from zero up, in order that these may correspond with equal variations of actual temperature. In thermometers generally, the marked degrees are of the same length throughout the scale; or they are of equal length between certain points ascertained by a standard, and correspond mathematically, not thermally, for all temperatures beyond the highest and lowest points so found. The error arising even from equal division between freezing and boiling points is very slight, since the degree has a mean length, a little too long below and too short above; but carrying the same divisions above boiling and below freezing point, it results that in the former part of the scale the temperature indicated is always higher, and in the latter part lower, than the actual temperature. Again, generally, the rate of expansion of glass increases about equally with that of mercury; and this fact sometimes nearly or quite corrects, or even over-compensates the variation in the volume of the mercury. But such correction cannot be relied on, since the rate of expansion differs much in different kinds or manufactures of glass, and even in the same tube under different circumstances. A result is, that two thermometers constructed with the greatest care seldom continue to agree through points much above or below the fixed points; and the uncertainty concerning the behavior of the glass must render absolute accuracy unattainable, and must introduce the question of possible variation into all scientific data collected from observations with two or more of these instruments. For the rates of variation in expansion of different kinds of glass, as determined by Regnault, see the works above referred to. It may be remarked, however, that good flint glass is best for the tubes, as most nearly and uniformly compensating the change in the mercury; while common or crown glass is irregular and less trustworthy. For the more accurate, or standard thermometers, the scale should be engraved on the tube itself, since the unequal expansion of a metal or ivory case or strip may introduce new sources of error; this effect is very nearly obviated, in the careful manufacture of the better class of common instruments, if time enough be allowed the tube, mercury, and case to acquire throughout the same temperatures, and the marking be carefully done. The length of the degree on

the scale, and hence the delicacy or minuteness of indication of temperatures, depending on the relative capacities of bulb and tube, there is a gain in this respect from making the bulb large and the tube exceedingly fine. But, again, the large bulb is liable sensibly to reduce the temperature of the very medium or mass tested, and especially when the volume of the latter is small; while for sensibility in the way of quick response, also, the smaller the bulb the better. Hence, the effort is directed rather to securing smallness of caliber in the tube; and to allow of this, the back of the tube is enamelled white to show the column by contrast, and the bore is flattened or made elliptical, a broader side standing toward the eye. In the most delicate scales, the subdivision is seldom carried beyond 20 parts to the centigrade degree; a practised eye will then read to hundredths of the degree. The eye in careful reading should always be at the level of the top of the column; and the aid of a small telescope may be employed. In using a standard thermometer, both bulb and stem should be immersed in the medium; if this be impossible, a correction must be made for the length of column in the tube unacted on; and when the mass of the bulb itself must sensibly abstract from the temperature to be observed, a further correction for this error is ⚫ required. Mercurial thermometers are liable to error from still other and more singular conditions. Owing to some change in the glass, either due to continued pressure of air, or more likely to slow rearrangement of the particles following the molecular disturbances by melting and blowing of the glass, the zero point slowly rises through a year or more, and sometimes to an extent of 1° or 2°. Hence, the tubes must never be used immediately after making, but laid aside at least 10 or 12 months before sealing and graduation. Despretz finds that this change may continue for an indefinite period. But sudden variations also occur, and either transient or permanent. As an example of the former, if a thermometer used for some time for ordinary temperatures have its zero point verified, and be then exposed for very little time to a heat at or above 212°, upon testing the zero point immediately after, it will be found (probably through permanence in degree of the expansion of the glass) lowered by .1° to .2°; and it may be some weeks in recovering its former position. In view of all these circumstances, it becomes necessary frequently to verify anew the 0 point in instruments for accurate observation. The utmost attainable accuracy is however secured only by use of a perfect air thermometer. (See Regnault's, in Cooke's "Chemical Physics," p. 534.) The common, cheap thermometers serve very well for such uses as observing the temperature of a room or a bath; but, as graduated with less precision, by comparison with a standard in a water bath, they are necessarily inaccurate, and differ much from each other, especially below 0° F. or much above the boiling

point. Owing also to the very rapid contraction of mercury near its point of congelation, 39° F., the temperatures shown by any mercurial thermometer much below 0° F. are deceptive, being apparently lower than in reality; and such errors have even arisen as that of supposing that in some instances the mercury itself had not congealed until reaching -44° or-46°. Alcohol, commonly used where temperatures much below 0° F. are to be observed, is liable at such range to much variation, although it does not freeze even at -132° F.; and Capt. Parry, in his arctic voyages, observed differences of full 10° C. between alcohol thermometers by the best makers. For measurement of temperatures considerably above the boiling point of water, see PYROMETER. Bréguet's metallic thermometer is an application of the unequal expansions of different metals; a compound bar of platinum, gold, and silver is rolled into an extremely thin ribbon, which is coiled into a spiral, the platinum outermost, one end being fixed and the other acting on an index moving over a circular scale; the silver, expanding most with heat, tends to unbend the spiral, and moves the index. This thermometer is both exceedingly sensitive and accurate, and can be used for very high temperatures. Mr. Victor Beaumont, of New York, constructs a cheap and serviceable metallic thermometer, on the principle of the compound metallic bar carrying an index; the necessity of transmitting the movement through several pieces is likely to introduce inequalities of indication, but probably no more than in good mercurial thermometers; while advantages of these instruments are, that they are portable, prompt, and easily read, and may be used to measure temperatures ranging from below -39° to 1,200° F. A differential thermometer is a modification of the air thermometer, in which two large glass bulbs above are connected by a glass tube bent twice at right angles; the horizontal and parts of the upright tubes are filled in the common form with a colored liquid, which is depressed on either side as the corresponding bulb is more heated; thus the instrument indicates differences of the temperatures to which the two bulbs may be exposed. It is very sensitive; and by a scale the results it affords are comparable with each other.-It is often important to have means of knowing the highest or lowest temperatures, or both, occurring during a period when, or in situations such that, the observer cannot be present; and for this purpose, the registering instruments known as maximum and minimum thermometers have been devised. One of the simplest and best known is Rutherford's maximum and minimum. Two thermometers are affixed upon the same plate, their tubes bent at right angles just above the bulbs and placed horizontally, each with its scale. The maximum thermometer has in front of the mercury column a short piece of iron wire, which is pushed along by the ad

vancing column, and left at the point where this begins to recede. For a new observation, the wire can be brought back to the column by moving a magnet near the tube, without. This wire, or index, is in transportation or handling liable to enter the mercury, and cannot usually be recovered without returning the instrument to the makers for refilling; so that many other forms of maximum have been devised to obviate this liability. Rutherford's minimum, however, sufficiently answers the desired purpose; it is filled with colored alcohol, and contains floating in this a small enamel cylinder, with beads on its ends nearly of the size of the bore. The alcohol in expanding readily passes this index, but in contracting, by adhesion it draws it back along with the head of the column, and thus leaves it at the lowest point reached. For a new observation, it is only necessary to tilt down the tube, when the index moves along to the head of the alcohol column again. As an improvement of the maximum thermometer, Prof. Phillips, of England, detaches a small portion of the mercury column by an interposed bubble of air, to serve as the index; while the instruments of Six and Walferdin are capable of great accuracy, and without risk of derangement, but require considerable trouble in their management. In Negretti and Zambra's maximum, in a short, obliquely ascending portion of the tube, between the bulb and the horizontal part, is fixed a small enamel rod, which, though it does not close the tube against the force of the expanding mercury, presents obstruction sufficient to break the column, if kept horizontal, when it begins to return; the column thus preserves almost exactly the greatest advance made, and shows the highest temperature to which it has been exposed. To prepare for a new observation, the instrument is held vertically and shaken, when the mercury returns; this operation, however, may lead to accident. Mr. James Green, of New York, appears (1860) to have removed the objections to the previous forms of maximum thermometer, and produced a highly simple and perfect instrument. In this the tube is straight throughout, but the bore is for a short space just above the bulb contracted to very small size—this being readily accomplished with the elliptical bore by compressing the tube upon the posterior side; and the size is made such that, while expansion forces the mercury through in regular and minute pulses or globules, the space upon the mercury's tending to return proves so small that the cohesive forces give to the liquid, as in the last named, the globular surface (usually ascribed to repulsion of the glass), and so break the column, leaving it to show, as above, its highest point. The instrument is provided with a suitable support, from a pin upon which it can be safely swung with a pendulous or revolving movement, when the centrifugal force suffices to return the mercury, as required for a new observation. For an account of Mr. S.

212; mercury, 662°.

Melting points: Tin, 442°; lead, 594°; silver, 2,283°; cast iron, 8,479°.

THERMOPYLE, or simply PYLE (from Sepμos, hot, and Tuλn, gate), a celebrated defile between Thessaly and Locris, the only passage for an enemy from northern into southern Greece, situated between Mt. Eta and an inaccessible morass forming the edge of the Maliac gulf. Between these two was a road wide enough only for a single wheel track, which formed the western gate. At about a mile to the eastward Mt. Eta again approached the sea in a similar manner, and the passage there formed the eastern gate. The space between these two gates was wider, but full of warm springs, which, many years before Leonidas occupied the pass, the Phocians had so conducted over the ground as to render the pass impracticable. They had also built a wall near the western gate to prevent the incursions of the Thessalians, which was in ruins when the Lacedæmonians came. The present appearance of Thermopyla is different, owing to the change made in the configuration of the road and the course of the rivers. The Maliac gulf has been rendered smaller by the accumulation of deposits made by the rivers; the mountain is not now near the sea; the course of the Spercheus has been changed, emptying now into the sea S. of Thermopyla instead of N. of the pass, as it did in the time of Herodotus; the rivers Dyras, Melas, and Asopus, which when Herodotus wrote reached the sea between Thermopyla and the mouth of the Spercheus, have now become affluents of the latter; and the level of the soil has been raised by the deposit from the warm springs. The defence of this pass made by Leonidas has immortalized its name. (See GREECE, vol. viii. p. 442.) It has also been since that time the scene of several memorable actions. Through the neglect

of the Athenians, and against the earnest remonstrances of Demosthenes, Philip was allowed to occupy it, and thus gain a foothold in southern Greece. Here the Greeks assembled in 279 B. C. to repel Brennus and the Gauls, and in 191 Antiochus the Great of Syria ineffectually labored to prevent the Romans from passing the defile. Several severe contests also took place here during the late Greek war of independence. On the heights above Thermopyla the remains of three Hellenic fortresses are still to be found.

THEROIGNE DE MÉRICOURT, ANNE JOSEPH, or LAMBERTINE, a noted woman in the French revolution, born at Méricourt, in the vicinity of Liége, in 1759, died in 1817. Though the daughter of poor peasants, she received an excellent education, but had to leave her native village on account of her dissolute life. Becoming acquainted with the Prussian baron so famous as 66 Anacharsis Clootz," she removed with him to Paris, became known as a courtesan, was on terms of intimacy with several of the revolutionary leaders, and took a large share in all insurrectionary movements. She was instrumental in bringing about the popular manifestation of Oct. 5 and 6, 1789, was loud in her denunciations of the queen, and entered Paris in triumph at the head of the dreadful procession which brought the royal family from Versailles to the Tuileries. On July 17, 1791, she figured in the mob dispersed in the Champ de Mars by the national guard under Lafayette and Bailly. Having visited her native country with a view to revolution, she was arrested, taken to Vienna, and imprisoned, but at the end of a few months sent back to France, where she assisted in the insurrections of June 20 and Aug. 10, 1792. On the latter day she mercilessly murdered Suleau, the editor of the Actes des Apôtres, who had ridiculed her in his paper, cut off his head and put it on the top of a pike, while trampling his corpse under her feet. She also shared in the massacres of September. A little later, being suspected of acting in behalf of the duke of Orleans and conspiring with the Girondists, she lost her popularity; and having once undertaken to vindicate Brissot in the Tuileries garden, she was seized by a number of enraged women, who stripped her and publicly whipped her. She became a raving maniac, and was confined in La Salpêtrière, where she remained insane for years.

THESEUS, the great legendary hero of Attica, was according to the commonly received legends the son of gens, king of Athens, and Ethra, daughter of Pittheus, king of Trozen. Egeus upon his departure from Trozen hid his sword and shoes under a stone, and charged Ethra if she gave birth to a son to send him to Athens as soon as he was able to roll away the stone. When he arrived at maturity his mother informed him of his parentage, and taking possession of the tokens he set out for Attica by land instead of sea, as the

country was infested with robbers, and he was anxious to signalize his prowess. On the road he destroyed various robbers and monsters, and arriving at Athens was recognized by his father, but narrowly escaped death from the hands of Medea. He also engaged in a war with the Pallantids, the sons and grandsons of Pallas, the brother of Egeus, in regard to the succession to the throne, and was victorious. His first great exploit was the capture of the Marathonian bull, which had ravaged the neighboring country. In this same enterprise Androgeos, son of Minos, king of Crete, had perished; and in return the Athenians had been compelled to send to Crete every 9 years a tribute of 7 young men and 7 maidens to be given up to the Minotaur, who were offered to him in a labyrinth constructed by Dædalus, from whose numerous passages no one could escape. When the third period for sending the victims arrived, Theseus came forward and offered himself, with the intention of slaying the monster. Arriving at Cnossus, he gained the affections of Ariadne, daughter of the king of Crete, and was furnished by her with a sword and a clue of thread, with which he killed the Minotaur and escaped from the labyrinth. Hereupon he quitted Crete with his companions, carrying off Ariadne, whom however he left behind at the island of Naxos. It had been agreed that in case the expedition should be successful, Theseus on his return should hoist white sails instead of the black ones which this vessel was in the habit of carrying; but this arrangement was forgotten, and Ægeus, imagining his son was destroyed, threw himself into the sea. Theseus now ascended the throne, and was engaged in a war against the Amazons, who had not recovered from the losses sustained by them from the attack of Hercules. He invaded their territory, defeated them, and carried off their queen Antiope. In revenge these formidable women crossed the Cimmerian Bosporus on ice, entered Attica, and marched to Athens itself, and were finally vanquished after a long and bloody battle in the streets of that city. Beside these there are but few of the ancient heroic enterprises in which Theseus does not figure. He was one of the Argonauts, was engaged in the Calydonian hunt, fought with Pirithous and the Lapithæ against the Centaurs, and also assisted Adrastus in regaining the bodies of those slain before Thebes. Aided by Pirithous, he carried off Helen from Sparta when she was only 9 years old. Attica was in consequence invaded by Castor and Pollux. Menestheus incited the Athenians to rise against their ruler; and Theseus, finding it impossible to sustain himself, retired to the island of Scyros, where he was destroyed by the treachery of King Lycomedes. In 476 B. C. the oracle directed his bones to be brought from the island to Athens, but it was not until 469, when Scyros was taken by Cimon, that it was pretended the body was found. His bones were laid in the interior of the city, and the

temple called the Theseum, built over the spot, served as a sanctuary for poor men in dread of the powerful, and for slaves in case of cruel treatment. At the battle of Marathon Theseus was reported to have been seen armed and aiding the Athenians against the barbarians. Festivals in his honor were celebrated on the 8th day of each month, and the festival termed Oschophoria was said to have been originated by him after his arrival from Crete. To him was popularly ascribed the origin of the Pyanepsia and the re-institution of the Pythian games. Thucydides states that the great political revolution, by which the petty independent states of Attica were consolidated into a united body with Athens at its head, was believed to have been effected by him; but there is no more historical proof of this than that he was actually a living person. The account of him throughout is entirely legendary, although the later writers endeavored to give it a historical coloring.

THESIGER, SIR FREDERIO (Lord Chelmsford), an English statesman and jurist, born in London in July, 1794. In 1803 he entered the navy as midshipman on board of a frigate, and in 1807 was present at the bombardment of Copenhagen; but on the death of his elder brother he left the navy and entered the profession of law, and in 1818 was called to the bar at Gray's Inn. He rapidly acquired great reputation, especially in the conduct of election cases, and in 1834 was appointed a king's counsel. He entered parliament in 1841 as member for the borough of Woodstock, and held a seat for different constituencies till 1858; his first speech was made in opposition to the war with China. In 1844 he was made solicitor-general in the administration of Sir Robert Peel, and knighted, and in 1845 succeeded Sir W. A. Follett as at torney-general, but the year following resigned on the retirement of his party. While a member of this government he strongly supported the free trade policy. In 1852 he was reappointed attorney-general in the administration of the earl of Derby, which in November gave place to that of Lord John Russell. On the return of Lord Derby to power in March, 1858, he was made lord chancellor and raised to the peerage as Baron Chelmsford, retiring with the rest of the cabinet in April, 1859.

THESPIS, the founder of Greek tragedy, a native of Icarus in Attica, flourished in the time of Pisistratus. The ancient traditions represent him as the inventor of tragedy, and to him is also ascribed the invention of masks. According to one account, probably a misconception, though sanctioned by Horace, Thespis was in the habit of travelling through Attica at the time of the festival of Dionysus in a wagon, and upon this portable stage performed comic plays. Another statement is that he found tragedy already existing in Athens, but that he made in it the simple and important alteration of introducing an actor for the sake of giving rest to the chorus. Of VOL. XV.-28

the character of his tragedies there is also doubt, some maintaining that they were wholly satyric in their nature, others again that he wrote serious compositions. His tragedies have all perished, but the titles of 4 have been preserved. Of the personal history of Thespis scarcely any thing is known except that his first representation was in the year 535 B. C. THESSALONIANS, EPISTLES TO THE, two canonical books of the New Testament, addressed to the church at Thessalonica by the apostle Paul. They are expressly referred to by Irenæus, Clement of Alexandria, and Tertullian. In modern times the authenticity of both epistles, and especially of the second, has been doubted by J. E. Ch. Schmidt (in his "Introduction to the New Testament"), by Baur (Paulus der Apostel Jesu Christi, p. 485 et seq.) and the entire Tübingen school, by Weisse (Philosophische Dogmatik, vol. i. p. 146), and many others; against whom special treatises in support of their authenticity have been written by W. Grimm (Die Echtheit der Briefe an die Thessalonier, 1850), Reiche (Authentia posterioris ad Thessalonienses Epistola Vindicia, Göttingen, 1830), Lünemann (in the introduction to his commentary on the two epistles), and others. The first epistle to the Thessalonians is, according to the common opinion, the first of all the Pauline epistles in point of time, and is supposed to have been written soon after the foundation of the church during Paul's first sojourn at Corinth, when Silas and Timothy had returned from Macedonia, about A. D. 52 or 53. The immediate occasion for this epistle seems to have been the favorable report which Timothy had brought of the faith of the Thessalonians, and the desire of the apostle to strengthen this faith. It consists of two parts: the first (chap. i. to iii.) contains an expression of the feelings of the apostle respecting the religious condition of the Thessalonians, and the reception which the apostle found with them; the second part contains an exhortation to holiness (iv. 1-12), an instruction on the fate of the dead at the expected return of Christ (iv. 13-18), an admonition to be always prepared for that event (v. 1-11), several other admonitions, and the conclusion. The second epistle was written soon after the first, in the year 53 or 54, and was evidently designed to correct some mistakes into which the church had fallen, especially respecting the coming of Christ. The apostle commends the Thessalonians for their patience and faith in their persecutions, and announces that those who trouble them will be punished (ch.i.); he shows that the arrival of Christ was not near at hand, but must be preceded by a great apostasy and the appearance of the Antichrist (ii. 1-12), and gives them appropriate admonitions (ii. 13-17, and iii.).-There are special commentaries on these epistles by Flatt (Tübingen, 1829), Schott (Leipsic, 1834), Jowett (London, 1856), Lünemann (Göttingen, 1859), Ellicott (2d ed., 1862), and others.