NOTES AND REFERENCES.-a. ne s'expliquait pas encore, could not yet understand.-b, dressaient, were erecting.-c. il serait, he would be present.-d. from aller; L. part ii., p. 76; also L. S. 25, R. 1.-. jour, light.-f. se faisant, penetrating; from faire; L. part ii., p. 92-g. L. S. 36, R. 2.-h. L. part ii., § 49. R. (1). SECTION IV. Les deux enfants ne pleuraient pas, tant la catastrophe prochaine qui leur était annoncée, et à laquelle il leur fallait bien croire enfin, jetait leur cœur dans une cruelle stupéfaction. C'était la douleur brûlante et sans larmes, pire cent fois et plus sinistre que la douleur qui s'écoule, quoique lentement, avec les pleurs. Le roi venait de leur donner sa bénédiction pour eux et pour leurs frères et scurs absents, quand le chefs à qui Cromwell avait confié plus spécialement la garde du condamné, soulevant le rideau qui séparait de lui le malheureux père et ses enfants: -Il est temps de vous quitter, leur dit-il; vous avez déjà dépassé l'heure d'entrevue qui vous était accordée. C A cette nouvelle violence, le roi faillite perdre la résignation dont il avait fait preuve jusqu'alors, et il lança un regard d'indignation à son geôlier. Ce ne fut qu'un nuage dans un ciels que plus rien de ce qui tenait à la terre ne devait troubler. Charles éleva ses yeux et ses mains vers le Seigneur qui a soufferts le supplice et l'infamie de la croix pour racheter les hommes, et comme lui, il sembla dire: -Que le sacrifice 10 s'accomplisse! Il laissa arracher ses enfants de ses bras paternels, et il ne s'occupa plus que de se disposer,12 à frapper dignement, comune il disait, à la porte de Dieu. 14 On lui avait aussi accordé, après bien des démarches,13 d'etre assisté dans ses prières par l'ancien évêque de Londres, le vénérable Juxon. Le roi, avec un visage serein, prêta the oreille attentive aux paroles consolatrices de l'évêque, La nuit qui précéda l'exécution, le roi dormit 15 avec le calme d'un homme qui n'avait plus que des rêves célestes. So sommeil ne fut troublé que par le bruit 16 des marteaux qui continuaient à frapper auprès de l'appartement: car, de Dear d'un soulèvement populaire ou d'un enlèvement, on élevait une estrade qui devait conduircis le roi de la fenêtre même de sa chambre à l'échafaud. Charles fut debout au point du jour. Il dit à Herbert son fidèle serviteur, qu'il fallait lui mettre 20 ses plus beaux habits, car il s'apprêtait à aller 21 recevoir une couronne plus celles que les hommes peuvent donner. belle que 12. De quoi s'occupa-t-il ? 15. Comment passa-t-il la nuit qui précéda l'exécution? 16. Par quel bruit son sommeil. fu-til troublé ? 17. Pourquoi élevait-on une estrade? 18. Où devait conduire cette estrade? 19. A quelle heure Charles se 20. Que dit-il à Herbert? NOTES AND REFERENCES.-a. L. part ii., § 65.-b. L. S. 25, R. 2.-c. L. S. 41, R. 8.-d. L. S. 41, R. 1.-e. faillit perdre, nearly lost; from faillir, L. p. ii., p. 92.-f. fait preuve, exhibited.-g. from souffrir; L. part ii., p. 106.-h. L. part ii., § 16, R. (5), 2d.-i. from falloir; L. part ii., p. 92. CORRESPONDENCE. POETRY. DEAR SIR,--Having seen a promise in the P.E. that you intend THE CATARACT OF LODORE. And there it lies darkling; It hastens along, conflicting, strong, Its caverns and rocks among. Rising and leaping, Around and around. With endless rebound; Dizzying and deafening the ear with its sound. Receding and speeding, And shocking and rocking, And thundering and floundering. And gleaming and streaming and steaming and beaming, And thumping and flumping and bumping and jumping, PHONETIC SHORTHAND. Edinburgh, 13, South Charlotte-street, May 29th, 1854. DEAR SIR,-The contents of the shorthand letter you sent me are such a pleasing tribute to the value of the P.E. and to the simplicity of the system of Stenography which I communicated, that I have taken the trouble to transcribe the whole for your inspection. The translation is verbatim-not a word or character has been passed undeciphered. In answering the letter, you should recommend a larger scale of writing, and a more exact attention to the relative sizes of the characters. The writing is beautifully executed. It is, considering the time spent in learning the system, a marvel of neatness and accuracy. Should you publish the letter in extenso, you can tell your readers that the writing occupied but half a page of small note paper, or exactly thirteen square inches. I wish you would let your correspondents know that the system is now published with improvements, and that the Vocabulary of Logograms is in progress in accordance with the new Alphabetic basis. It will, however, be some months yet before the work is published. My professional engagements leave me but little time, and the Shorthand has often to give place to more pressing matters during the little leisure I have. I was very much pleased to see the letter of the Railway Policeman last week. If you give me his address, I will send him a copy of the Pop. Stenography.-Yours, very truly, R. Wallace, Esq., Dalston. ALEX. MELVILLE BELL, The following is the Letter referred to by Mr. Bell :— the two following days, which almost set my mind at ease, as I saw Gibraltar, 4th May, 1854. Str,-Having hitherto been a subscriber for the POPULAR and BIBLICAL EDUCATOR, the former I feel convinced is a work that cannot be too fully appreciated amongst all classes of people; being, in fact, notwithstanding the rapid march of intellect and civilization of which England may boast, a wonder of the age. I have read and studied several lessons on different subjects attentively, for the express purpose, not only of learning from its pages myself, but of endeavouring to find out that its foundation is laid down with such a systematic principle, that all who wish to avail themselves of the opportunity of acquiring knowledge may do so, by applying their mind studiously and industriously to any part of it; and in which, I feel called to announce from my humble position in life, that it surpas es any work hitherto published. I feit very much puzzled when I commenced upon the French Lessons, owing, no doubt, to my entire ignorance of foreign languages at the time. However, I relinquished the French for a time, and made an effort to learn the Spanish language (which I have attained tolerably well for the time I applied myself to it), considering that it would facilitate the study of other languages; but it does not, further than, perhaps, giving me a knowledge of a foreign articulation, so that I felt nearly as much puzzled afterwards as before; and I would have been entirely so, had I not kept the first lesson brooding in my mind during the short time that I left it off. As I could not shake off the puzzling difficulty that had become seat d in my mind, which was as though it urged me to apply my mind industriously to the task that I might surmount it, I took up the book again, and after three hours close study, I felt convinced that I could overcome it; I then did the same May 29th, 1854. Translated from the Shorthand by Alex. Melville Bell. dence, and we hope that it will encourage our readers to try Mr. [We have much pleasure in inserting the preceding corresponBell's system developed in our pages, Vol. iii. P.E. The perseverance of the author in the acquisition of French, even to the pronunciation, deserves all praise, and every one's imitation.ED.] LITERARY NOTICES. Now Ready, CASSELL'S FRENCH DICTIONARY In Two Parts:-1. French and English; 2. English and French. The French Department carefully edited by Professor DE LOLME, and the English Department by Professor WALLACE and H. BRIDGEMAN, Esq. In one large handsome Octavo Volume, price 9s. 6d. strongly bound. CASSELL'S LESSONS IN FRENCH. Parts I, and II.-By Professor FAS the Exercises. Price 18. paper covers, or ls. 6d. cloth. A COMPLETE MANUAL OF THE FRENCH LANGUAGE.--By Professor DE A SERIES OF LESSONS IN FRENCH, on an entirely Novel and Simple Plan. Reprinted in a revised form from "The Working Man's Friend." Price od by post 7d. Nearly 30,000 copies of this work have been sold. Now Ready, CASSELL'S GERMAN PRONOUNCING DICTIONARY: CASSELL'S LESSONS IN GERMAN PRONUNCIATION: consisting of easy The First Three ON PHYSICS, OR NATURAL PHILOSOPHY. No. XXXIX. (Continued from page 175.) HYGROMETRY. THE object of the science of Hygrometry (moisture-measuring), is to determine the quantity of the vapour of water contained in a determinate volume of air, or in the atmosphere. This quantity is very variable; but the air is seldom saturated with the vapour of water in our climate; and it is never completely free of that vapour; for, if we expose hygrometric substances to the action of the air, these substances absorb the vapour of water at all times. By hygrometric substances here, we mean those which have a great affinity for water, as chloride of calcium, sulphuric acid, etc. Hygrometric State.-The air not being in general saturated with vapour, the hygrometric state, or the fraction of saturation of the air, is the ratio of the actual quantity of the vapour of water which it does contain, to the quantity which it would contain if it were saturated, the temperature being the same in both cases. Now Mariotte's law applies to vapours not saturated as well as to gases; whence, it follows, that at an equal temperature and volume, the weight of the vapour in a space not saturated, increases with the pressure, and consequently with the tension of that vapour. We may, therefore, instead of the ratio of the quantities of vapour, substitute that of the corresponding elastic forces; consequently, the hygrometric state of the air may be defined as the ratio of the elastic force of the vapour of water which it contains, to the elastic force of the vapour which it would contain, at the same temperature, if it were saturated. As a consequence of this second definition, it is important to observe, that when the temperature varies, the air may contain the same quantity of vapour, and yet not be in the same hygrometric state. Thus, when the temperature is elevated, the elastic force of the vapour which the air would contain in the state of saturation increases more rapidly than the elastic force of the vapour which actually exists in the air, and then the ratio of these forces, that is, the hygrometric state, becomes less. The weight of the vapour contained in a given volume of air may be deduced from its hygrometric state, as will be shown at the conclusion of this lesson. Hygrometric Instruments.-Instruments employed to determine the hygrometric state of the air, are called Hygrometers. Many instruments of this kind have been invented; but they may be classed under four principal kinds. Chemical hygrometers, absorption hygrometers, condensation hygrometers, and psychrometers. The latter kind is founded on the rapidity of the vaporisation of water in air. be very small; but when it is freed from all greasy matter, it rapidly lengthens in passing from a state of dryness to a state of humidity. The hair e is supported at its upper end by a catch a, fastened by a screw d. This catch is raised or lowered by means of a screw b, to which the nut is fixed. If the hair be knotted, a torsion will arise, which will render its lengthening irregular. At the lower end, it is wound on a pulley o, to which it is fixed. This pulley has two grooves, on one of which the hair is fastened; and on the other, in a direction contrary to that of the hair, is fixed a silk thread, which supports a small weight p. The axis of the pulley carries a small index, which moves over a graduated scale. When the hair is shortened, the traction which it exerts raises the index; when it lengthens, the weight p causes the index to descend. To graduate the scale, that point is marked 0° where at the ordinary temperature, the index stands in perfectly dry air; and that with vapour; the interval is then divided into 100 equal parts, point is marked 100° where it stands in air completely saturated which are the degrees of the hygrometer. placing the hygrometer under a bell-glass, in which the air is The zero, or point of extreme dryness, is determined by dried by enclosing with it substances having a great affinity for water, as chloride of calcium, or calcined carbonate of Chemical Hygrometers.Every substance which possesses a consequently the hair shortens and causes the pulley and the potassa. The air of the bell-glass loses its humidity, and great affinity for water is a chemical hygrometer. A substance index to move round, but very slowly. At the end of fifteen of this kind, such as chloride of calcium, is introduced into a U-shaped tube; this tube is then put into communication with indicates that the air of the glass is completely dried. On the or twenty days only, does the index become stationary, which an exhauster, filled with water, like the vessel a, fig. 202. As scale, 0° is then marked at the point where the index stands. soon as the water is allowed to run out of the exhauster, the The point of extreme humidity is obtained by removing the air rushes into it, through the tube which contains the desic-desiccating substances from the bell glass, and wetting its cating substance, and all the vapour which the air contains sides with distilled water. This liquid, by its vaporisation, is absorbed by this substance. If, therefore, the tube and its soon saturates the air of the glass, and the hair rapidly lengthens. contents be weighed both before and after the experiment, the The small weight suspended by the silk thread, and wound increase of the latter weight gives the quantity of the vapour on the pulley in a direction contrary to that of the hair, now of water contained in a volume of air equal to that of the causes the index to turn round in a direction opposite to that exhauster. From this weight, we can then deduce, by calcu- of zero. lation, the hygrometric state of the air. This process is the the point where the index stands, is marked 100°. According In less than two hours, it becomes stationary; and most exact, but it is not sufficiently simple for meteorological to Saussure, a hair stretched by a weight of about five grains Absorption Hygrometers.-Organic substances which lengthen of a light or flaxen colour is that which lengthens in the most is lengthened, between 0° and 100°, by of its length. Hair when they become humid, and shorten when they become regular manner. dry, are called absorption hygrometers. Several hygrometers the variations of temperature are neglected, because it has been The expansion which the hair undergoes by of this kind have been invented. The one most employed in observed that for a difference of 33° Centigrade or 914 Fahmeter, from the name of the inventor. practice, is that called the hair hygrometer or Saussure's hygro-renheit, the lengthening of the hair does not alter the index composed on which a hair e is sion being omitted, it is observed that whatever may be the This instrument is more than of a degree on the hygrometer. This small expanstretched, after having been freed from its natural grease by temperature, the index of the hygrometer returns exactly to 0° immersion in water containing one-hundredth part of its in air perfectly dry, and to 100° in saturated air. The fixity eight of sub-carbonate of soda. If the hair be not thus puri- of the latter point shows that in saturated air, the air always Red, it will absorb very little vapour, and its lengthening will absorbs the same quantity of water, whatever may be its tem observations. TOL, T. perature, and consequently, whatever may be the density of the vapour. never falls so low as 100°, even after the greatest rains. During the greatest droughts, it rarely rises about 30°. When we rise in the atmosphere, with this instrument, the index generally marches towards 0°. In the aerostatic ascent of Gay-Lussac, to the height of 22,966 feet, the hygrometer stood at 26°, a number which nearly corresponds to the hygrometric state. Experience has shown that hair hygrometers only agree with each other, when the hairs employed are of the same kind, and are prepared in the same manner; so that in order to obtain exact indications, à particular table must be constructed for each hygrometer. Condensation Hygrometers.-The object of the condensation hygrometers is to show, by the reduction of the temperature in the air, at what point the vapour which it contains would be sufficient to saturate it; such is the principle on which are founded the hygrometers invented by Mr. Daniell and M. Regnault. The hygrometer of Daniell is composed of two glass bulbs connected by a double bent tube, fig. 201. The Fig. 201. Hair hygrometers present many inconveniences in their con- TABLE OF HYGROMETRIC STATES OF THE AIR, TEMPERATURE OF 50° FAHRENHEIT. bulb A is about two-thirds full of ether, in which is immersed This table shows that at 72°, the air is only half saturated. As it is at this point that the index of the hygrometer generally stands at the surface of the ground, it is evident that, at a mean, the air contains the half of the vapour which it would contain were it saturated. In our climate the hygrometer Greek), invented by Professor August, enables us to ascertain The Psychrometer.-The psychrometer (cold measure, from the the tension of the vapour contained in the atmosphere, the dew-point, the point at which the atmosphere would be saturated, and the absolute weight of the vapour contained in very delicate thermometers, whose degrees exactly correspond any particular volume of air. This instrument consists of two with each other, and are divided into fifths or tenths of degrees, the scales ranging from about -25° Centigrade or -13° Fahrenheito 40° Centigrade or 104° Fahrenheit. These thermometers are vertically fixed in a frame, at the distance of about three inches from each other. The bulb of the one is covered with muslin; which is kept continually moistened by means of a cotton thread attached to it, the other end of the thread being kept in a vessel or cup full of distilled water; the bulb of the other is kept dry. As the water imbibed by the muslin surrounding the one bulb evaporates, the mercury in the thermometer begins to sink, and the drier that the air is, the more rapid will be the evaporation, and the more sensible the descent of the mercury. When the air around the bulb is saturated with moisture, the mercury will become stationary, and the point at which it rests will be the dew-point or condensation-point. The greater that the difference is between the heights of the two thermometers, the more dry must be the state of the air, and the further is the vapour it contains from being at its maximum density. The difference between the heights of the two thermometers will be zero, if they are placed in an atmosphere containing aqueous vapour at its greatest density. From the degrees of heat shown by the two thermometers, the elastic force of the vapour in the air, and its amount per cent., can be determined. The humidity or hygrometric state of the air varies at all hours, we might indeed say, at all minutes of the day. It is at its maximum before sun-rise, and at its minimum in the middle of the day. It varies in the different months of the year. In December, the air is the most humid; and in July and August, the most dry; yet, it can be proved that in these two latter months the air contains the greatest quantity of the vapour of water in evaporation of them contains a very sensible thermometer fastened by means sea-coasts, the air, other things being equal, is more humid than In these cups are fixed two glass tubes and B. Each of stagnant water on the earth's surface being mote active. On the of a cork. The cork of the tube D, is traversed by a tube A in the interior of the continent. In the steppes, deserts, and The tube is also put in communication, by means of the bottom the air has sometimes an extraordinary dryness; but at of the stand and a leaden pipe, with an exhauster a full of mean, it is more humid there than in the plains. The relati |