this tube in the vertical position with the closed end down-are inversely proportional to their densities. On the other wards, fill it completely with mercury; then, closing the open end c with the finger or thumb, invert the tube and immerse this end in a cup nearly full of mercury. Withdrawing then the finger from the tube at B, and supporting it with the other hand at A, the column of mercury in the tube will sink two or three inches, and then become stationary at a height AB of about 30 inches above the mereury in the cup, when the experiment is performed at the level of the sea, and during a mean state of the atmosphere. hand, if the weight of the atmosphere increases or diminishes from any natural cause, in any given place, it is evident that the length of the mercurial column will increase or decrease accordingly. Pascal's Experiments.-The celebrated Pascal, wishing soon after, to prove for himself that the force which supported the mercury in the tube of Torricelli was really the pressure of the atmosphere, had recourse to the two following experiments, which placed the fact beyond a doubt. First, foreseeing that In order to explain the nature of this experiment, we observe, the column of mercury ought to descend in the tube in proporthat as the pressure of the atmosphere acts with great regu- tion as it was raised in the atmosphere, because that then its larity on the superficial stratum of liquids placed in an open pressure would be diminished, he requested a relation living in vessel, it does not in general disturb the horizontality of such the province of Auvergne, in France, to repeat, on the mounsurfaces. But if by any means a limited portion of this stra-tain called Puy-de-Dome (4,846 feet high) the experiment of tum be protected from the atmospheric pressure, the equili-Torricelli. Here the column of mercury was diminished in brium will be destroyed, and the liquid will rise up to fill the height by a quantity which was between three and four inches vacuum produced above it, to a determinate height depending in length; this proved that it was really the weight of the aton the nature of the liquid. This is indeed what takes place mosphere which sustained the mercury in the tube; because, when we immerse the one extremity of a tube in water, and as this weight decreased, so did the column of mercury. withdraw the air by suction at the other extremity. By this Secondly, Pascal repeated the experiment of Torricelli, at process, we only diminish the pressure within the tube; but Rouen, in 1646, with another liquid instead of mercury. He in the Torricellian experiment the pressure of the air is com- took a tube of about fifty feet long, closed at one end and pletely removed, and there is a complete vacuum at the top of it open at the other; he filled it with water, and inverting it, when inverted. We have seen, that on the moment of the placed it in a reservoir full of water; he then observed that the inverted end becoming free, the mercury in the tube descends to water in the tube sunk to the level of about thirty-four feet a level about 30 inches above that of the mercury in the open above the level of the reservoir. Now the altitude of the cup; this level is always the same whatever be the length of column of water being about 13'6 times that of the column of mercury, and the density of mercury being about 13.6 times the tube, its shape, or its inclination. that of water, the weight of the column of water in this experiment is equal to the weight of the column of mercury in the Torricellian experiment; hence it is justly inferred again, that it is the pressure of the atmosphere which equally supports both of the liquid columns. In this experiment the elevated column in the interior of the tube presses on the part of the cup on which it stands, with a force which replaces that of the atmosphere; but the latter still continues to press with the same force on the rest of the surface of the mercury in the cup; and the particles of the liquid, yielding to this pressure, would have been forced up the tube to the same height, supposing that it had been a perfect vacuum, on its immersion. In fig. 70, where a section of the tube and Fig. 70. LESSONS IN GREEK.-No. XX. THE NUMERAL ADVERBS DENOTE how many times a number is to be taken, as "six times six make thirty-six;" here six times is a numeral adverb; thus diç signifies twice, Tous three times. The termination of the numeral adverbs is in general κις (ακις, τακις), which is annexed to a cardinal, as τεσσαράκις, έξακις, ἑκατοντακις. 10 δεκακις 11 ένδεκακις 13 rpiçkaidrakkig 100 ἑκατοντακις 2000 διςχιλιάκις 14 τέτταρεςκαιδεκακις οι τεσσαρ. 1000 χιλιάκις cup is shown, it will be observed, that when the mercurial 17 ἑπτακαιδεκακις 10,000 μυριάκις RECAPITULATORY EXERCISES FROM THE CLASSICS. If we perform the same experiment with any other liquid 1. Ανάχαρσις κρειττον έλεγεν, ένα φίλον ἔχειν πολλού άξιον, instead of mercury, we must have recourse to much longer tubes, in order to produce the vacuum at the top of the column. η πολλους μηδενος αξίους. 2. Αννων, ὁ πρεσβύτερος, εκ της The heights to which different liquids rise, in such experiments, | Λιβυης επέρασε μεγαλην δύναμιν εις Σικελιαν, πεζων μυριάδας EXTRACTS FROM THE NEW TESTAMENT. εντε, ἱππεις δε ἑξακιςχιλίους, ελέφαντας δε έξηκοντα. 3. Τους Ξηρας ἱστορούσι μέχρι τριακοσίων ζην ετων, και τους Χαλδαίους ύπερ τα έκατον ετη βιοῦν λογος (εοτι). 4. Αργανθώνιος, 1. Είπε δε ὁ Ιησους, Ποιησατε τους ανθρώπους αναπέσειν. ὁ Ταρτησσιων βασιλευς, πεντηκοντα και έκατον ετη βίωσαι Ην δε χορτος πολύς εν τῳ τοπῳ. Ανέπεσον ουν οἱ ἄνδρες τον λέγεται. 5. Ο Πλάτων ετελευτησε τῳ πρωτῳ της ογδοης και αριθμον ώσει πεντακισχίλιοι. (John vi. 10). 2. Πολλοι δε των ἑκατοστης Ολυμπιάδος, βιους ετος ἐν προς τοις ογδοηκοντα. 6. ακουσαντων τον λογον επιστευσαν και εγενήθη ὁ αριθμός των Δημήτριος τις ειπε τῳ Νέρωνι συ μεν απειλεις εμοι τον θάνατον, ανδρων ώσει χιλιαδες πέντε. (Acts iv. 4). 3. Και είδον και σοι δε ή φυσις. 7. Σχολαστικός απόρων, τα βιβλια αύτου ήκουσα φωνην αγγελων πολλων κυκλῳ του θρόνου και των επιπρασκε, και γραφων προς τον πατερα έλεγε, συγχαιρε ἡμιν, ζωων και των πρεσβυτερων και ην ὁ αριθμός αυτων μυριάδες πατερ, ηδη γαρ ήμας τα βιβλια τρέφει. 8. Ανάχαρσις ὁ μυριάδων και χιλιαδες χιλιαδων, λέγοντες φωνῇ μεγάλη, Αξιον Σκύθης ερωτηθεις ὑπό τινος, τί εστι πολεμιον ανθρωποις; εστι το αρνιον το εσφαγόμενον λαβειν την δύναμιν και πλουτον αυτοι, έφη, ἑαυτοις, 9. Σχολαστικος οικιαν πωλων, λιθον απ' και σοφίαν και ισχυν και τιμήν και δόξαν και ευλογίαν, (Rev. αυτής εις δειγμα περιέφερε. 10. Κριτης ων, αει ταύτα περί των v. 11, 12). 4. Ο έχων νουν ψηφισάτω τον αριθμόν του θηρίου" αυτών γιγνωσκε, ουδεν τρος χαριν ποιων. 11. Ψυχης επιμελου αριθμος γαρ ανθρωπου εστι, και ο αριθμός αυτού (sc. εστιν) της σεαυτού. 12. Βουλου αρεσκειν πασι. 13. Παντων μαλιστα χές. (Rev. xiii. 18). 5. Ο δε Ιωαννης διεκώλυεν αυτόν, σαυτον αισχυνου. 14. Ραστον άπαντων εστιν αὐτον εξαπατᾶν. λεγων, Εγω χρειαν ἔχω ὑπο σου βαπτισθήναι, και συ ερχῇ προς 15. Ο αγαθε, μη αγνοει σεαυτόν. 16. Ιφικρατης σκυτοτόμου μεν υἱος ην, ενδοξότατος δε. Ούτος είπε προς τινα των ευγενών το μεν εμον γενος απ' εμου αρχεται, το δε σον εν σοι 17. Θαλης ερωτηθεις, τι κοινότατον; απεκρίνατο ελπις και γαρ οἷς αλλο μηδεν, αὑτος παρεστιν. 18. Οἷον το αθος έκαστου τοιουτος ὁ βιος. 19. Φερεται ὁ Νειλος απο των Αιθιοπικών όρων μέχρι της εις θαλασσαν εκβολης σταδια μυρια και δισχιλια. 20. Τα δις πεντε δέκα εστιν. 21. Εντευθεν εξελαύνει σταθμούς δυο, παρασαγγας πεντε, επι τον Σαρον ποταμον, οὗ ην ευρος τρια πλεθρα. παύεται. VOCABULARY. 1. αξιος, α, ον, worth, worthy; πολλ. αξ, of great value. 2. Αννων, ωνος, ο, Hanno, the Carthaginian general, επερασε (from περας, beyond), transported, carried over; πεζων (from πεζος), of foot soldiers; ἱππεῖς ἱππευς) horsemen, cavalry. 3. Σηρας (Σηρ, ος) the Seres, an Indian people who produced silk ; ζην (infin. of ζαω. I live), to live; Χαλδαίους, the Chat deans ; τα έκατον ετη literally, above the hundred years ; so with either number the article is used when a whole is contemplated in construing into English you must drop the article in such cases : βιουν (from βιοω, I live, βιος, life), to live. 4. βίωσαι, to have lived; λεγεται, is said. 5. ετελεύτησε (from τέλος, an end), came to an end, died, Ολυμπίας, άδος, ή, an Olympiad, a period of five years, the Greeks reckoned time by Olympiads as we date from the birth of Christ, A.D. ; βίους, having lived; ετος έν, &c., one year to eighty, that is 81 years. 6, είπε, said ; Νερών, ωνος, δ, the Roman emperor Nero; απειλεις (from απειλεω, I threaten), threatenest. 7. Σκολαστικός, ου, o, an idler, a willing, απόρων, being in straights ; επιπρασχε, sold. 8. ερωτηθεις (ερωταω, I ask), being asked, εφη, said, από swered. και με. (Μatt. iii. 14). 6. Αλληλων τα βαρη βασταζετε, ούτως αναπληρώσατε τον νομον του Χριστοῦ. (Gal. vi. 2). 7. Η γαρ καυχησις ήμων αύτη εστι, το μαρτυριον της συνειδήσεως ήμων, ότι εν ἁπλοτητι και ειλικρινεια Θεού, ουκ εν σοφις σαρκική αλλ' εν χαριτι Θεου, ανεστράφημεν εν τῷ κόσμῳ, περισσότερως δε προς ύμας. (2 Cor. i, 12). 8. Ει τις ουν παράκλησις εν Χριστῳ, ει τι παραμυθιον αγαπης, ει τις κοινωνια πνευματος, ει τινα σπλαγχνα και οικτριμοι, πληρώσατε μου την χαραν, ίνα το αυτό φρονητε, την αυτην αγαπην έχοντες, συμψυχοι, το έν φρονουντες, μηδεν κατα ερίθειαν η κενοδοξίαν, αλλά τη ταπει νοφροσύνη αλληλους ἡγουμενοι ὑπερέχοντας έαυτων, μη τα ἑαυτῶν ἑκαστος σκοπούντες, αλλα και τα έτερων έκαστος. (Philippians ii. 1-4). VOCABULARY. 1. Ιησους, Jesus ; ποιήσατε (ποιεω, I make, do), male, cause to; αναπέσειν (πιπτω, I fall), to sit down, χορτος, ου, o, grass ; ανεπεσον, they sat down; τον αριθ, as to number, that is, in number, or to the number; ώσει, about. 2. των ακουσαν. (ακουω, I hear), of those who heard, επιστευσαν (πίστις, faith), believed; εγενήθη (γινομαι, I become), was, rose to. 3. ειδον (είδος, appearance, shape), I saw ; ηκουσα, I heard, αρνιον, ου, το, lamb ; εσφαγομενον (σφάγιον, α victim). 4. Ο έχων νουν, let him who has mind; ψηφισάτω (ψήφος, a bean ; the Greeks reckoned with beans, as the Latins did with pebbles, calculi, whence calculate), calculate. 5. διεκώλυε (κωλύω, I hinder), tried to hinder ; βαπτισθήναι, to be baptized, βαπτω, I dip; ερχη, comest thou 6. βαστάζετε (βαστάζω, I carry), bear ; ούτως, thus ; αναπλη. (ανα, up, πλροω, I fill), fill up, fulfil. 7. καυχησις, εως, ή, boasting, συνειδησις, εως, ή, conscience ; απλότης, ητος, ή, simplicity ; ειλικρίνεια, ας, ή, sincerity; σαρκικος (σαρξ, Mesh), fleshly, ανεστράφ. we have behaved (conducted) ourselves, we have acted; περισσοτερως (περι, denoting abundance), more exceedingly. 8. παράκλησις, εως, ή, exhortation, comfort, παραμυθιον, ου, το, solace, soothing ; κοινωνία, ας, ή, community ; πνεύμα, ατος, spirit; σπλαγχνον, ου, το, δοκείς; οικτριμος, ου, o, pity; πληρώσατε (πληροω, Ifill), fulfil; φρενητε (φρενες, the mind), that ye desire, aim at, love, συμψυχοι (ψυχη, the soul), being of the same soul, of one soul; ερίθεια, ας, ή, strife, κενοδοξία, (κενος, empty), vainglory; ταπεινοφροσύνη, ης, ή (ταπεινός, humble), lowliness of mind ; ήγουμενοι, thinking, considering ; ὑπερέχειν, to be superior; σκοπουντες (σκοπειν, to look, hence επισκόπειν, to overlook, whence our word bishop). REMARKS. The pronouns are among the oldest words in every language. Consequently, if in two languages the pronouns are found to have strong marks of resemblance, we may safely conclude that those two languages are akin to each other. Such marks of resemblance may be found by comparing the Greek and the English personal pronouns together. Thus the Greek eyw, through the Latin ego, is clearly the English I (also the Gernan ich and the French je). Look at the Greek accusative μɛ, the Latin me, and the English me. Again compare the Greek cu, the Latin tu, and the English thou; also the accusatives, namely oe, te, thee. The è (the & aspirated and so made he) is obviously our he. Similar remarks may be made with regard to the numerals. Obviously in structure, as well as in individual numbers, the Greek numeral system is the same as our own. The student, if he has well attended to these lessons, may Low rejoice in having made some considerable progress; and ine progress he has made he may in a measure estimate by the comparative ease with which he has just read passages from the Greek New Testament. General View of what has been set forth. Noun Substantive used to name objects, as, erpariwrns, soldier (a soldier). Article used to determine nouns, as ò orpariwrns, the soldier. out; out of. without; outside Nach, after; to; nc cording to. of. Bei, by; near; with. Binnen, Entgegen, Gegenüber, Gemäß, some men. which man? the man who. my father. Mit, relative possessive Pronoun εyw, I; ov, thou; où, of himself. LESSONS IN GERMAN.-No. LXXXI. $ 108. TABLE OF THE PREPOSITIONS. (1) Prepositions construed with (2) Prepositions construed with An, $ 115. PREPOSITIONS CONSTRUED WITH THE DATIVE OR ὁ άμθρωπος ός, ὁ εμός πατερ, Auf, on; upon. Unter, under; among. behind. Bor, before. in, or into. Zwischen, betwixt ; Neben, beside. between. Db, $ 116. These prepositions govern either the accusative or the dative; but not without a difference of signification: for, when motion towards, that is, motion from one point to another, is indicated, the accusative is required: when, however, motion or rest in any given place or condition is signified, the dative is used; thus, ter Knabe läuft in den Garten, the boy runs into (motion towards) the garden; ter Knabe läuft in dem Garten, the boy runs in (motion within) the garden. This is the general principle; which will be found, with more or less distinctness, everywhere to prevail in the use of the prepositions of this class. D6, whether; if. Obgleich, though; although. Ohne, without; except. Ungeachtet, notwithstanding. Wo, if. Wofern, if; in case that. INTERJECTIONS. LESSONS IN CHEMISTRY.-No. XVI. which yield yellow or white precipitates with hydrosulphuric HAVING finished our preliminary consideration of the metals acid, or hydrosulphate of ammonia, I purpose now leaving the metals for a time, and discussing the chemical properties of certain non-metallic elements. Oxygen shall be the subject of discussion and experiment in the present lesson. When I inform you that oxygen constitutes, at least, threefourths of the crust of the globe and its living inhabitants, you will admit that it must be an important element. Oxygen, by combination with other bodies, may assume the condition of solid, liquid, or gas, but obtained separately, it is always gaseous; therefore we shall have to obtain it and examine it under the form of oxygen gas. There are several methods of generating oxygen gas, but only one capable of being followed by a student who is unsupplied with special instruments. This process I shall describe with a view to its adoption; the others I shall afterwards mention, with the object of making their theory understood. First, let us begin by describing the instruments necessary. You will require either a large test tube, about half or threequarters of an inch in diameter, made by preference of German glass, as being more infusible than our own; a bent glass tube, and a pneumatic trough, or its substitute, and a receiver. You will require, in point of fact, an arrangement like the following: Fig. No. 1. 008 or such a substitute for it as your ingenuity, stimulated by your necessities, will easily supply. I need scarcely indicate that your distillatory apparatus being small (ie. the test tube), your receiving bottle must be small also. In the present case, ounce or ounce-and-a-half phials will be of sufficient dimensions. Scarcely more necessary is it to remark, that the distillatory apparatus, as indicated above, will require some sort of support not represented in the diagram, and that the regular pneumatic trough may be dispensed with, by using a basin instead, the receiving bottle being prevented slipping by means of some heavy material, such as lead, brick, &c., placed in the basin, and indicated by the letter в in our sketch. So much then for the apparatus. Fig. No. 2. Here we close our Lessons in German in these pages. But we beg to inform our readers that a continuation of themcomprising a Syntax of the Language, at once popular and complete may be found in CASSELL'S LESSONS IN GERMAN, Part II.; a publication which also contains all the lessons upon Systematic Grammar which have appeared in the POPULAR EDUCATOR; that is to say, those from No. XLIX. to the present. The substance we shall require as the oxygen-yielding material, is a mixture of two parts by weight of the salt termed chlorate of potash, and one part by weight of peroxide (black oxide) of manganese; the substance procurable in commercial circles, under the simple name "manganese." If the student should by chance live in a remote place, where old chemical terms still dominate, the druggist will inform him that he does not keep such a material as chlorate of potash; if the s* more successful. ask for it under the name of oxymuriate of potash, he will be (1.) Having uncovered a bottle full of the gas, pour into it a little transparent lime-water, and agitate; not the slightest change results. (2) Immerse in another bottle a slip of moistened litmus paper, and another of moistened turmeric paper; not the slightest discoloration of either slip takes place, thus demonstrating that oxygen gas is neither acid nor alkaline. The mixture of chlorate of potash and black oxide of manganese should be effected, if possible, by rubbing the two together in a mortar; mere incorporation, however, with the blade of a knife will answer sufficiently well. You will not do amiss by preparing at least an ounce of this mixture, and preserving it properly labelled in a bottle. The operation of gene(3.) Take a splinter of wood, such as a bit of lath, or a long rating oxygen will frequently be required in the course of brimstone match, ignite the end, wait for a few seconds until future experiments, and students who do not possess a gaso-an incandescent coal has formed; blow out the flame and meter must prepare the gas little by little as it may be re- plunge the glowing though not flaming extremity into a bottle quired. of oxygen gas. Immediately the wood bursts into flame, thus Pour about a tea-spoonful of the mixture into the test tube, indicating the presence of a gas different from any already replace the cork, arrange the apparatus, and apply heat. Oxy-noticed in these lessons. It is thus proved by this experiment gen gas will come over rapidly, but the first portions being necessarily contaminated with atmospheric air previously existing in the apparatus, must be thrown away; all subsequently collected is pure oxygen gas. Collect six or seven bottles full of it, and before proceeding to try any experiments, follow me in discussing the theory of its production, and the nature of gases generally. What, then, is a gas? I know of no definition which is logically distinctive. The definition long received was, 66 a permanently elastic fluid," but it is incorrect. Nevertheless, the expression permanently elastic fluid, although not sufficiently general in its significance to comprehend all gases, indicates the most salient property of so many, and applies so perfectly to the gas under consideration, that we may profitably discuss its meaning. I have therefore to inform you that oxygen gas is permanently elastic; that is to say, neither cold nor pressure, nor both combined, nor, in short, any other agency, has yet succeeded in condensing oxygen gas into a liquid or a solid condition. Now many gases equally transparent and colourless as oxygen have been condensed into liquids, and even solids. I dare say, most people have observed the bubbles which escape from ginger-beer, soda-water, champagne, &c. These bubbles are due to the presence of a transparent, colourless gas, named, carbonic-acid; it has not come under our notice yet, but it speedily will. By the application of intense cold and pressure, this gas may be converted into a solid, having the aspect of snow. A similar result has been accomplished in the instance of many other gases; therefore, it follows that the neatly turned definition, formerly accepted as characteristic of gases, is no longer admissible. Oxygen gas, however, has resisted every attempt at liquefaction or solidification; yet analogy leads us to suppose that, if we could apply sufficient cold and sufficient pressure, a similar result would ensue. Abandoning all logical definition of a gas as hopeless, it is still in our power to entertain a good, general appreciation of the leading characteristic of gases, by remembering that persistent elasticity, under common circumstances, is the special feature by which they are contradistinguished from vapours; the latter being readily condensed. For example, steam, or aqueous vapour, is the result of the application of heat to water. We all know that steam is elastic, or else what would be the use of expansion gear in a steam engine? But it is not permanently elastic under ordinary circumstances, for immediately on coming into contact with the air, or any material sufficiently cold, it condenses into water. When thus condensed, it fills a position analogous with a liquefied gas; and when, on the further application of cold, ice results, we have a condition analogous to that of a solidified gas. Perhaps some such question as this occurs to you. How am I to reconcile the apparently incongruous statements that oxygen can only be procured as a gas, and that three-fourths of the material elements of our globe are composed of it? There is no contradiction involved in these statements; as a constituent of the solid and liquid matters of the globe, oxygen is combined, and chemical combination, you are well aware, produces wonderful changes. Both clay and flint contain a vast amount of oxygen, the latter nearly fifty per cent; but the oxygen existing in combination, its solidity is attributable to that circumstance. Experiments with Oxygen Gas.-Proceeding to examine systematically the properties of oxygen gas, attend to the following directions. that oxygen gas is a supporter-a very powerful supporter-of combustion. It is moreover proved by the same experiment that oxygen gas is not a combustible, because, although causing the stick to burst into flame, itself does not. Remember how diametrically opposed these qualities are to those of hydrogen. If the mouth of the receiving bottle be large enough, the preceding arrangement may be varied as follows. Fig. No. 3. Instead of a slip of wood use a piece of wax taper, attached, as represented in the accompanying diagram, to a bent piece of copper or brass wire. Proceed in other respects exactly as in the experiment just detailed. Fig. No. 4. two bottles full of oxygen, and open them. Place one to (4.) Perform the following comparative experiment: take stand during a few seconds open upon a table-mouth upwards of course. Hold the other for a similar period open, and inverted, as represented in the diagram; finally, by means of an ignited stick, test either bottle for the presence of oxygen. The upright bottle will be found still to contain it; from the other it will have departed; thus we prove that oxygen gas is specifically heavier than the atmosphere. Nevertheless, it is only heavier by a very slight amount; calling atmospheric air one or unity, the specific gravity is one and onetenth and a little more-how much this "little more may be, chemists are not agreed upon. The experiments just performed-indeed one of them, the flame-ignition of the wood, or taper-are sufficient to distinguish oxygen gas from all other gases, save one, the protoxide of nitrogen, or " laughing gas." By observing the character of flame produced, we may, without further trials, distinguish between these two. Oxygen gas yields a flame of exquisite |