As this table is constructed for the Centigrade scale, it will be useful to show how to adapt it to the scale used in this country. By removing the decimal point in each of the numbers of the table two places to the right, these numbers will then represent the whole amount of expansion which each bar of metal undergoes when heated from 0° to 100° Centigrade, or from 32° to 212° Fahrenheit. By dividing each of these numbers by 180 (the number of degrees from 32° to 212°), the being k, the elongation corresponding to t degrees is t times k or kt for a single unit, whence it is 7 times kt or ktl for I units of length. The length of the bar which was at 0° Centigrade, is therefore + ktl at t degrees; whence = 1 + ktl (1). By putting into the form of a common factor, we have l (1 kt) (2) This formula will give the length l at to when the length at 0° Centigrade is known, By dividing both members of the preceding equation by (1 kt), we have l (3). This formula will give the 1 + kt = ľ Fig. 175. D quotients will become the co-efficients of expansion according to Fahrenheit's scale; that is, the quantities by which each bar of metal will be elongated when its temperature has risen by 1° Fahrenheit between the freezing and the boiling points of water. Thus, the co-efhcient of expansion for glass, by the Centigrade scale, is 0-000008613; therefore, glass expands 0 0008613 of its length at 0° Centigrade, when heated from that point to 100° Centigrade, or from 32° to 212° Fahrenheit; now, dividing 0-0008613 by 180, we have 0 000004785 for the co-efficient of expansion, according to Fahrenheit's scale. As it may be useful to many of our readers, we give the By denoting the volume of a body at 0° Centigrade by unity or 1, and its cubic expansion by k, the volume at t degrees will be 1+kt; but the density of a body is in the inverse ratio of the volume which it takes on expansion, we have, 1 therefore, ; whence, d'=. 1+kt All these formulæ and rules will apply to examples in Fahrenheit's scale, if 32° Fahrenheit be put for 0° Centigrade, and t 32° for t; also, if the Table of the Co-efficients of Expansion according to Fahrenheit's scale, be used instead of that according to the Centigrade scale. d Examples. I. If a bar of iron be exactly twelve feet long at 0° Centigrade, what will be its length at 80° Centigrade, the coefficient of linear dilatation being 0 000012204 according to the Centigrade scale? Here, by formula (2), we have — 12 (1+0.000012204 × 80) 12 01171584 feet, or twelve feet and of an inch nearly. II. If a bar of iron be twelve feet long at 32° Fahrenheit, what will be its length at 176° Fahrenheit, the co-efficient of linear dilatation being 0.00000678 acccording to Fahrenheit's scale? Here, by formula (2), we have '12 (1+0-00000678 X 144)=12-01171584 feet, or twelve feet and of an inch nearly, as before. III. If a bar of copper be fifteen feet long at 90° Centigrade, what will be its length at 0° Centigrade, the co-efficient of linear dilatation being 0.000017182 ? Here, by formula (3), we have 7 = 15 10-000017182 × 90 14.96685 feet, or 14 feet 11 inches nearly. Applications.-The expansion of solids presents numberless applications in the arts. The iron gratings of furnaces, for instance, should not be too accurately fastened at their extre mities, but left free at one end at least; otherwise they will displace the stones of the fire-place by their expansion. If on railways the iron rails are in contact, the force of expansion will make them either become curved, or will break their chairs. When a glass vessel is heated or cooled too suddenly, Fig. 177. it breaks in pieces; because glass being a bad conductor of caloric, the sides of the vessel are irregularly heated, and consequently expand unequally, which produces the disruption of the parts. Compensation Pendulum.—The unequal expansion of different Fig. 178. ठे 95 metals has received an important application in the compensation pendulum. This name is given to a pendulum in which the elongation of the rod when the temperature is raised is compensated for in such a manner that the distance between the centre of suspension and the centre of oscillation remains constant, which is necessary according to the laws relating to the pendulum formerly explained, in order that its isochronism may be preserved, and that it may be employed as a clockregulator. Various methods have been proposed for this purpose; but that which is represented in fig. 177 has been generally adopted. In this method, the bob L, instead of being supported by a single rod, is supported by a series of frames, of which the vertical rods are made alternately of iron and brass. In the first frame abde, the rods ƒƒ are made of iron, and are soldered to two bars a b and c d, which, as well as the bar o i, may be made of any metal whatever. In the interior frame the two rods ce are made of brass, and are soldered to the bars oi and ed. The middle rod which supports the bob is made of iron. It is fixed only to the bar oi, and passes freely through a hole in the middle of the bar ed. This app ratus operates as follows: when the temperature rises, the iron rods ƒƒ are lengthened downwards and tend to lower the bob. The brass rods cc, on the contrary, fixed at the bottom, can only be lengthened upwards; therefore, they raise the bar oi and consequently raise the bob. By this means the bob is kept at a constant height, provided the elongation of the brass rods in the one direction be equal to the total elongation of the iron rods in the other direction. This effect is obtained by giving to the iron and brass rods such lengths in the frames as are in the inverse ratio of the co-efficients of expansion of these two metals. Another method of compensating for the elongation of the pendulum rod, is by means of compensating laminæ or bars. It consists of two bars, one of brass and one of iron soldered together, and fixed to the rod of the pendulum, as shown in fig. 178. The bar of brass, which is more expansible than the bar of iron, is placed below it. When the temperature is lowered, the rod of the pendulum is shortened, and the bob rises; but then the compensating bars become curved, as shown in fig. 179, because the brass contracts by cold more than the iron. In this manner, two metallic balls placed at the extre mities of the compound bar are lowered; and if they have been points which are nearer to the centre of suspension and those properly adjusted, they establish a compensation between the which are farther from them, and thus the centre of oscillation is not displaced. If the temperature is raised, the bob descends; but the balls are raised, as shown in fig. 180, and compensation takes place by a similar operation. oxide of manganese and common salt (about equal parts by weight)-five or six table-spoonfuls will suffice for our wants; place the mixture in a Florence flask, to which a cork and bent tube have been securely adapted, add sufficient of a mixture of oil of vitriol and water (equal parts by measure) to reduce the oxide of manganese and salt to the consistence of a paste; apply heat, and proceed to collect by means of the prismatic trough as usual. A few preliminary words expressive of certain cautions to be observed in the development of this gas will not here be out of place. First of all, it is not sufficient merely to pour the dilute acid upon the manst he well incorporated by shaking, otherwise the flask will most probably break on the first appli- | the extent of the decomposition,-reducing it to very narrow cation of heat. The great object of well incorporating the limits-by taking care that no unnecessary amount of water powder and the fluid is to cause a wetting of the bottom and enter, and that the store bottles be of black or deep blue glass. sides of the flask. If a spirit-lamp flame be applied to dry The manipulation to be followed, in order to obviate the glass, that is to say, retained dry by the interposition of a imprisonment of water, thus to speak, with the chlorine is powder, the glass is almost certain to be ruptured. The this. second caution to be mentioned has reference to the danger (or inconvenience to say the least) attendant upon the escape of chlorine, which is a gas most irritating to the lungs and air passages. Not one bubble, therefore, should be allowed to escape, consequently, in addition to the bottles or jars designed to store the pure gas, the first portions which come over, and which are necessarily mixed with atmospheric air, should be collected in spare bottles, placed ready on the shelf of the pneumatic trough for that purpose. Our experiments, presently to be gone through, will require five or six bottles full of chlorine; half-pint wide-mouthed bottles will suffice, or even smaller ones; but whatever the size, their stoppers and mouths, whilst yet dry, should be well smeared with stiff pomatum. As regards the water of the pneumatic trough, it should be-whatever certain books may say-cold. I state this pointedly, in consequence of directions very frequently given, that chlorine should be collected over warm water, in order that no portion of the gas may be absorbed. True, warm water prevents absorption of the gas, but its employment gives rise to a far more serious evil. It causes the gas to expand, to enter the receiving vessels in a rarefied condition, and finally the bottles being stoppered and allowed to grow cold, and the gas contracting, the stopper frequently becomes obstinately fixed by the agency of external atmospheric pressure. This very serious evil more than compensates for the non-absorption of the gas by hot water: nor indeed is the absorption of chlorine by cold water sufficiently great to prove inconvenient, except under the condition of the water being agitated, a condition altogether unnecessary, save and except the agitation referrible to transmission of the gas bubbles themselves. PHYSICAL AND CHEMICAL CHARACTERISTICS OF 1) Its Smell.-No specific experiment need be performed in illustration of this quality. Notwithstanding all the precautions indicated-all the care taken-most probably some will have escaped, and rendered itself manifest to the olfactory sense. At any rate, beware how you proceed to smell it deliberately, for when breathe d even considerably diluted, it gives rise to most painful sensations. (2) Its Colour.-The peculiar tint of chlorine is almost distinctive of this gas or some of its gaseous combinations. It is rendered very evident by placing as a foil, behind the bottle containing it a sheet of white paper. (3) Its Solubility in Water.-This property of chlorine has already been noticed whilst discussing the best method of collecting it; let us now direct our attention to the special demonstration of that property. For this purpose, take a halfpint bottle full of chlorine, and whilst yet inverted on the shelf of the pneumatic trough, seize it underhand thus, fig. 34, and Fig. 34. maintaining its orifice below the water-level, agitate by a sort of rotatory motion. Gradually the water will be seen to rise in the bottle, and an aqueous solution of chlorine will result, similar to the gas itself in colour, smell, and many chemical properties. This solubility of chlorine gas in water is a very important function, of great practical utility in several manufacturing operations, more especially those of bleaching. A gas, more particularly an irritating gas like chlorine, is a very intractable agent to deal with, being devoid of that amount of condensed or local The 97 LESSONS IN ITALIAN GRAMMAR.-No. XXIII. energy so necessary in manufacturing operations. absorption of chlorine by water gives rise to a liquid agent, which the manufacturer can easily apply; but there are other absorptive agents, especially lime, even preferable to water in of the University of Pavia, and Professor of the German and Italian this respect. They will come under our notice hereafter. Languages at the Kensington Proprietary Grammar School. ADJECTIVES. ITALIAN adjectives either terminate in o or in e; e. g. pô-ve-ro, and become feminine by changing o into a. κόσμο man don-na The poor Le pó-ve-re mn don-ne Chlorine as a Bleaching Agent.-Chemists of a bygone era, misled concerning the nature and analogies of chlorine, considered it as an acid, which they denominated "Orymuriatic Acid," that is to say, a compound of muriatic acid plus oxygen. It remained for Sir Humphry Davy to demonstrate that it was neither an acid nor did it contain oxygen, but that it was a simple chemical element. He termed it chlorine. The exact line of demonstration pursued by that great chemist we are not quite in a condition to follow; but we can at least show that it is devoid of two of the most general properties of an acid, being neither sour to the taste nor having the property of reddening litmus paper. That it is not acid to the taste may be The poor recognised by bringing in contact with the tongue a little of its which immediately follows it; e. g. il sub-li-me e-sêm-pio, The article is determined by the initial letter of the word watery solution. That it does not (permanently) redden re-sem-pio sub-li-me, the sublime example; i sub-li-mɩ e-sêmlitmus paper, may be demonstrated by dipping a slip of moistened litmus paper into a bottle containing chlorine, or a stret-to, lo stret-to á-bi-to, the tight dress; l' im-pré-sa pe-ri-copj, gli e-sem-pj sub-li-mi, the sublime examples; l'a-bi-to bottle of its aqueous solution. At first there is a redness pro-ló-sa, la pe-ri-co ló-sa im-pré-sa, the hazardous undertaking, duced, not due to chlorine, however, but to the presence of hydrochloric acid developed by the reaction of chlorine on aqueous moisture; soon, however, the redness disappears, and the paper is bleached. If, instead of litmus paper, a sprig of green vegetable, such as parsley, be employed, or a strip of indigo, dyed cloth, or cloth dyed Turkey-red, or generally any coloured vegetable or animal body, bleaching will equally result. Hence we may conclude that bleaching is a general function of chlorine. (4) Solvent Action.-Into a bottle containing chlorine introduce a slip of gold leaf attached to a glass rod. aqueous solution of chlorine introduce another piece of gold leaf. In either case the chlorine will rapidly act on the metal; in the latter case completely dissolving it. This is a very important test, not merely indicating the presence of chlorine generally, but that the chlorine is free or uncombined. Into an The poor women The adjectives terminating in e are used for the masculine the plural; e. g. as well as for the feminine gender. They change e into i in vér-de hat vér-de leaf. I cap-pêl-li vér-di The green hats Le fo-glie vér-di The green leaves man Il cap-pêl-lo The green La fo-glia The green Nouns terminating in the masculine in tó-re, and in the feminine in tri-ce, frequently stand for adjectives following a substantive; e. g. u mo vin-ci-tó-re, victor (i. e. conqueror); dón-na vin-ci-tri-ce, victress (i. e. womanconqueror) belong or refer, in gender and number, when they stand Italian adjectives must agree with the nouns to which they immediately before or after these nouns, and even when they (5) Chlorine as a Supporter of Combustion.-Viewed under this uo-mo dot-to e ra-gio-né-vo-le, a learned and sensible man; uôare separated from them by verbs or other words; e. g. un aspect, chlorine is a very extraordinary substance. Its rela-mi ni dot-ti e ra-gio-né-vo-li, learned and sensible men; ú-na tions to combustion are far too numerous and of too great importance for summary discussion in this lesson. We will treat fully concerning this subject in our next meanwhile prepare the following experiments. Procure a piece of wood charcoal, of such dimensions that it can easily be immersed in a bottle full of chlorine gas. Fig. 35. dón-na sa-via e pru-den-te, a wise and prudent woman; quél-le don-ne só-no sá-vie e pru-den-ti, those women are wise and prudent; gió-va-ni pa-sto-rél-le, quan-to siê-te fe-li-ci! young shepherdesses, how happy you are! singular, either agrees with the nouns or remains unaltered. It Méz-zo, when it means la me-tà, the half or moiety, in the must remain unaltered in the plural; e. g. un ó-ra e mêz-za or un ó-ra e méz-zo, one hour and a half; ú-na lib-bra e mêz-za or ú-na líb-bra e mêz-zo, one pound and a half; dú-e lib-bre e mez zo, two pounds and a half. Mez-zo, when it is used as an adverb before an adjective or participle, also remains unaltered; e. g. ê-ra mêz-zo môr-ta perlo spa-vên-to, she was half-dead with fright. Of adjectives connected with and following each other, only the last agrees with the noun in gender and number; e. g. os-ser-va-zió-ni stô-ri-co - cri-ti-che, historical and critical remarks; stu-dj po-li-ti-co-le-gd-li, political and legal studies. An adjective which refers to two nouns of different genders, takes the plural number and the masculine gender; e. g. ľ tôi mo ela dinna só-no sog-gêt-ti al-le stes-se pas-sin-ni, man and woman are liable to the same passions; gli ál-be-ri e le vi-ti fú-ron di-s'rút-ti dál-la gra-gnuô-la, the trees and the vines were destroyed by the hail. An adjective which refers to more than two nouns of different genders, generally takes the gender of the majority of the nouns to which it refers; e. g. il pá-dre, la zi-a e le cu-gi-ne só-no-par-ti-te, the father, the aunt, and the (female) cousins have departed; le so-rél-le, il pá-dre ed i fra-têl-li sé-no an-dá-tỉ gone out to take a walk. Wind round about it, as represented, some fine copper wire, a pas-seg-giá-re, the sisters, the father, and the brothers have thus made to enclose the charcoal tightly in a sort of cage, and mount the wire on a perforated zinc disc and cork, in the manner already followed during our experiments on oxygen. The adjectives bêl-lo, beautiful; grán-de, great, large; sản-to, holy; and the masculine pronoun quél-lo, that; sometimes drop the last syllable. With regard to this abbreviation, the following rules must be adhered to: Les louanges refusées savent bien revenir avec plus de force, et il syllable when they precede a noun. 1. The above-mentioned words can only drop their last est peut-être aussi modeste de leur laisser leur cours naturel en ne les prenant que pour ce qu'elles valent.-Fontenelle. 2. The initial letter of this noun must be a consonant which is not the s impure. 3. They take the apostrophe before nouns commencing with a vowel. 4. They must never be abbreviated before nouns beginning with the impure. 5. Bél-lo and quel-lo only drop the last syllable in the singular and before nouns of the masculine gender, 6. Grán-de also drops the last syllable in the singular and before nouns of the masculine gender; but, in addition to this, it may lose its last syllable before a noun of the feminine gender, and also in the plural before nouns of both genders. 7. San-to only drops the last syllable before a proper name of the masculine gender and singular number, but not before an appellative or common name. It must also immediately precede the proper name; e. g. U'-no drops the final vowel before any word commencing with a consonant which is not the s impure. Buô-no only drops its final vowel when immediately preceding a noun of this description; e. g. un giar-dí-no, a garden; un pô-co, a little; buôn fi-glio, good son; un buô-no ed o-ne-sto vec-chio, a good and honest old man. Adjectives very frequently are used in the place of nouns, and in such cases have the article before them; e. g. il vér-de ná-sce da ú-na com-po-si-zió-ne del giál-lo e del tur-chi-no, the green colour springs from a mixture of (the) yellow and (the) blue; en pô-co di bê-ne, un pô-co di ma-le, a little of what is good, a little of what is bad." them; e. g. un véc‐chio ra-gio-né vo-le, a sensible old man; ú-na dón-na gra-zió-sa, a graceful woman; un libro pô-co ú-ti-le, a not very useful book; un o dór mól-to grá-to, a very agreeable od ur; un ui-mo trập-po pe-ri co-có-so, a too dangerous man; ú-na ma-ri-na bên im-por-tan-te, a very considerable navy; un bô-sco co-si fól-to, so dense a wood. 4. When participles are used in the place of adjectives ; e.g. ú-no sguár-do com-mo-vên-te, a moving look; un uô-mo e-ru-di-to, let-te-rd-to, a learned man. 5. When adjectives denote natural qualities perceivable by the olfactory organs, by the sense of tasting, or by any other of the senses, or when they express bodily defects and infirmities or official employments and rank; e. g. pán-no fi-no, fine cloth; êr-ba a-ma-ra, bitter herb; lé-gno séc-co, dry wood; pan fré-sco, new bread; l'a-mór ciê-co, blind love; a piè zop-po, with a lame foot; il man-to im-pe-ri-le, the imperial mantle; il consi-glie-re aú-li-co, the aulic counsellor; il giar-dí-no_im-perid-le, the imperial garden. Where common usage has assigned to an adjective a place Un ga-lint uô-mo, an honest man. E'-gli a-vé-va pro-prio ve-sti-to, he had his own dress. Un gen-til uô-mo, a gentleman by birth, a nobleman. L'uô-mo pô-ve-ro, the poor man (opposed to rich). Un dol-ce son-no, a soft or calm sleep. Un tém-po dol-ce, a mild season (or mild weather.) news. cular prepositions after them; e. g. in, per, etc. In most cases, emphasis or euphony will be the best guide for deciding whether an adjective is to be placed before or after a noun; e. g. con ver-gó-gna e-têr-na or con e-tér-na ver-gó-gna, with eternal dishonour; un ca-vál-lo bel-lis-si-mo or un bel-lis si-mo ca-val-lo, a very beautiful horse; un con-té-gnu pre-gid-sci-ta e co-stu-mi, noble by birth and in his manners; in-nobi-le or un pre-giá-bi-le con-té-gno, an estimable appearance. In the following cases, however, the learner will do best, at least in prose, strictly to adhere to the practice of placing the adjective after the noun : 1. When adjectives are derived from proper names of nations, countries, and towns; e. g. la let-te-ra-tu-ra in-glé-se, English literature; l'ac-ca-de-mia fio-ren-ti-na, the Academy of Florence; il pó-po-lo spa-gnuô-lo, the Spanish people. 2. When adjectives express the form or colour of a thing; e. g. ú-na piáz-za ro-tón-da, a round market-place; ú-na fi-gu-ra qaa-drú-ta, a quadrangular figure; in-chio-stro ne-ro, black ink;-gi di cit-ta-di-no, deprived of civil rights; ê-su-le dál-la pdber-rét ta rós-sa, red cap; d-bi-to tur-chi-no, blue dress. 3. When adjectives have more syllables than their nouns, or the words po-co, little; mól-to, much; as-sd-i, enough, much, greatly, very; trop-po, too much, too, excessively; be-ne, well, justly, rightly, right; co-si, so, thus ; and similar adverbs before que su-per-sti-zio-ne, immu-ne da ogni gra-vét-za, free from tria, exiled from one's native country; e-sin-te da qua-lunevery superstition, from every burden; stan-co dal viag. gio, tired by the journey-vir-tuo-so nel cán-to, accomplished in singing; va-len-te, ec-cel-len-te in poe-si-a, skilful, excellent, |