English personal pronouns together. Thus the Greek yw, through the Latin ego, is clearly the English I (also the Gerinan ich and the French je). Look at the Greek accusative μe, the Latin me, and the English me. Again compare the Greek v, the Latin tu, and the English thou; also the accusatives, namely σe, te, thee. The (the e 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 man who. my father. good soldier. ten soldiers. tenth legion. this man. that man. the same man. the man himself. some men. which man? εyw, I; σv, thou; ov, of himself. together with. together with since. from; of. OBSERVATIONS. LESSONS IN GERMAN.-No. LXXXI. Anstatt, or statt, Oberhalb, Troy, between. $ 116. Unfern, Binnen, diesseits, Ungeachtet, Gegenüber, 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, der Knabe läuft in den Garten, the boy runs into (motion towards) the garden; der 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. S 117. THE CONJUNCTIONS. (1) Conjunctions are words used in connecting sentences. As, however, there are various kinds of connections existing among sentences, it has been customary to classify the conjunctions according to the nature of the connection which they are employed, to indicate. Hence we have (among other classes) the following: Copulatives: as, und, and; auch, also, as, denn, for; weil, since, because. Conclusives: as, barum, therefore; daher, hence; teßhalb, therefore. Concessives: as, obwohl, obschon, obgleich, wenn; although. Finals: as, daß, that; auf daß and bamit, in order that; um zu, in order to. (2) We give below a list of the conjunctions that most commonly occur in German: premising only that some of the words here set down as conjunctions are also employed as adverbs; for it will of course be kept in mind, that the office performed by a word determines its name and character. For numerous examples illustrating their uses, see Sect. C. Also, so then; consequently; also. Nur, but; only. Db, whether; if. Obgleich, though; although, Ohne, without; except. Ungeachtet, notwithstanding. Wenn, if; as. 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 deseribing 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: 0008 Fig. No. 1. 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 (i.e. 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. ask for it under the name of oxymuriate of potash, he will be more successful. 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 biade 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 generating oxygen will frequently be required in the course of future experiments, and students who do not possess a gasometer must prepare the gas little by little as it may be required. (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. (3.) Take a splinter of wood, such as a bit of lath, or a long brimstone match, ignite the end, wait for a few seconds until an incandescent coal has formed; blow out the flame and plunge the glowing though not flaming extremity into a bottle of oxygen gas. Immediately the wood bursts into flame, thus indicating the presence of a gas different from any already 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. Pour about a tea-spoonful of the mixture into the test tube, 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, "a permanently elastic Auid," 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. 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 purity, without any halo surrounding it; a reddish halo, however, envelopes the flame which is generated under similar treatment in protoxide of nitrogen, or laughing gas. Moreover, oxygen gas is devoid of taste, whereas, protoxide of nitrogen is perceptibly sweet. Although we have succeeded in finding the characteristics which distinguish oxygen from all other gases, it is far too important an element to be discussed in this one lesson. In my next I shall describe another series of experiments, having for its object the teaching of the various relations of oxygen to other bodies. This lesson I shall terminate with an examination of the changes which ensue in the mixture of oxide of manganese and chlorate of potash, as causes, concomitants, or 1esults of the evolution of oxygen gas. 66 h m 8. From subtract b - h+d Ans. + h hijd y 139. To subtract an integer from a fraction, or a fraction from an integer. 138. Fractions may also be subtracted, like integers, by First, then, let me remark, that although peroxide of man-setting them down, when the sign of the subtrahend is ganese contains, as its name indicates, a great deal of oxygen; changed, one after the other, without reducing them to a although it is frequently employed alone as an oxygen-yielding common denominator. material; yet, used as we have used it in combination with chlorate of potash, it does not undergo the slightest change. There are some instances of chemical decomposition determined or aided by mere contact with a body that undergoes no change in itself. Chemists designate this sort of action саtalytic;" they might as well term it "incomprehensible" at once. However, not to weary you with mere names, remember that the oxide of manganese determines, we know not why or how, an evolution of oxygen gas from chlorate of potash at a much lower temperature than would otherwise be necessary. Chlorate of potash, if heated alone, evolves all its oxygen, provided the temperature to which it is exposed be sufficiently high but it is almost too high for glass to bear; hence, the advantage of mixing the chlorate with oxide of manganese. In the following diagram I shall leave out the oxide of manganese altogether. Change the sign of the subtrahend, and write it after the minuend; or, put the integer into the form of a fraction, and ther proceed according to the general rule for subtraction of fractions. 10. From h subtract m. Ans. m or h-my 1 Chlorate of potash 124 12. From 1+ subtract Ans. 1+ 1 Potash =36 of potassium =76 LESSONS IN ALGEBRA.-No. IX. (Continued from p. 118.) C ac-cx-bd-by be SUBTRACTION OF FRACTIONS. 137, RULE.-Change the sign of the subtrahend, that is, of the fraction to be subtracted; and then proceed as in addition of fractions. 16. From a с ad+ay—be+cx take Ans. bd+by-de-ay 3d 17. From a- take Here, reducing the fractions to a common denominator, they x2—y2—10a-106 10x+10y bm |