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and outside the focus, its inverted image is seen hanging in the make use of flat mirrors for burning. Hutton says the astonishing air.
philosophico-military exploit of Archimedes has been recorded In Fig. 11 diverging rays proceeding from the hand cd, are by Diodorus Siculus, Lucian, Dion, Zonaras, Galen, Anthemius, made converging when they fall upon the mirror ab, and the in. Tzetzes, and other ancient writers. The account of Tzetzes is so verted image is seen at m, the diverging rays cd being brought particular that it suggested to Father Kircher the specific to a point at o s, where they cross and enter the eye.
method by which Archimedes effected his purpose. "Arthi. It is in this manner that the concave mirror has been medes," says that author, “set fire to the fleet of Marcellus by used, probably from the most
a burning-glass, composed of ancient times, to produce
small square mirrors, moving illusory spectres, and by con.
every way on hinges; and cealing the mirror, and illu.
which, when placed in the sun's minating the object properly,
rays, reflected them on to the very amusing effects may be
Roman fleet, so as to reduce it shown. Nearly every old work
to ashes at the distance of a on optics gives a diagram
bow-shot.” This accountgained and directions for using the
additional probability by tho concave mirror, of which Mr.
effect which Zonaras ascribes Walker's is probably one of
to the burning mirror of Prothe best.
clus, by which he affirms that In Fig. 12 let a be the
the fleet of Vitellius, when bemirror, d the actor concealed
sieging Byzantium, now Conby the cross partition, c, e a
stantinople, was utterly constrong light, also concealed by
sumed. But perhaps no histothe partition i. If d holds a
rical testimony could have book, or any other object, the
gained belief to such extraorFig. 8.
light reflected from it will pass
dinary facts, if similar ones between the screens, or parti
had not been seen in modern tions, e and i, to the mirror, and
times. In the memoirs of the be from thence reflected to .,
French Academy of Sciences where the image of the book
for 1726, p. 172, we read of a will appear so tangible, that
plane mirror of twelve inches the spectator, looking through
square reflecting the sun's rays the opening x, will suppose he
to a concave mirror sixteen could take hold of it. The con
inches in diameter, in the focus federate, d, may actuate vari.
of which bodies were burnt at ous moving figures, as flying i
the distance of 600 paces. The birds, angels, demons, etc., the
great naturalist Buffon coneffects of which at % would be
structed a burning apparatus very surprising.
by combining 168 pieces of lookA concave mirror becomes a
ing-glass six inches by eight, burning mirror when held in the
so that he could, by mesun. The heat at the focus is
chanism connected with each, very powerful. It is not, how.
concentrate the rays of the ever, supposed that this was the form of reflector used by sun to one focus; and by using 224 mirrors he was able to melt Archimedes when he destroyed the fleet of Marcellus by con- plates of silver at a distance of forty feet; with 112 mirrors he centrating the rays of the sun upon his ships. The celebrated set fire to planks covered with wool at a distance of 138 feet; Kircher went to Syracuse, and observed that the Roman ships even with twelve mirrors combustibles could be inflamed at a could not have been at á less distance from the walls of the distance of twenty feet. city than thirty-three paces ; and, as the focus of a concave It was with the concave mirror the ancients re-kindled the mirror is at the distance of half the radius, he calculated that the sacred fire, so carefully watched by the vestal virgins. Plutarch, concave mirror used by Archimedes must have been a portion of in his life of Numa Pompilius, says that the instruments used a sphere of at least forty-six paces radius, and therefore most for this purpose were dishes, which were placed opposite to the difficult, if not in those days) impossible to construct. Vitellio son, and the combustible matter placed in the centre; by which states that Anthemius of Tralles, the engineer
who lived in the it is probable he meant the focus, conceiving that to be at the time of the Emperor Justinian, was the first who proposed to centre of the mirror's concavity.
CORRESPONDENCE IN FRENCH.-VI.
Mets, le 15 Janvier 1865.
Messieurs Armand Roubot et Cie, à Londres. 22.–LETTER IN REPLY TO AN ORDER FOR AN ARTICLE
Messieurs,-Le porteur de cette lettre, Mons. F. Decretelle, WHICH HAS BEEN SOLD.
de cette ville, est un des nos anciens amis. Il se propose de Bremen, March 19th, 1866.
faire un voyage en Angleterre, et nous prenons la liberté de Messrs. Smith Brothers, London.
vous le recommander. Gentlemen,-I regret extremely to have to inform you that En cas où M. Decretelle aurait besoin de quelque argent the article in question has been sold to Mr. Barton, of your pour ses dépenses de voyage, ayez la bonté de lui compter ce city. Perchance you might come to an understanding with qu'il vous demandera, jusqu'à concurrence de £500 (nous disons him.
cinq cents livres sterling) contre sa traite sur nous à trois jours I have some pretty articles of a different kind (a list of which de vue. Ci-joint nous vous donnons sa signature. I subjoin) that might possibly suit you.
S'il vous est possible de l'aider à atteindre le but de son I am, Gentlemen,
voyage, nous vous en serions très-reconnaissants.
Toujours dévoués à vos ordres en pareille occasion,
Nous vous saluons cordialement,
HENRI DE LA TOUR & FILS. Messieurs Smith Frères, à Londres.
Messieurs,—Je regrette infiniment de vous dire que l'article 25.-LETTER ACKNOWLEDGING RECEIPT AND ADVISING demandé a été vendu à M. Barton, de votre ville. Peut-être
PAYMENT OF BILLS, pourriez-vous vous entendre avec lui à cet effet.
Inyons, October 7th, 1866. J'ai de jolis objets d'un autre genre (dont je vous envoie une Messrs. Reilton, Sons & Co., Bradford. liste) qui, probablement, pourraient vous convenir.
Dear Sirs,--We duly received your favour of the 3rd inst. Agréez, Messieurs,
covering l'assurance de ma parfaite considération,
fr. 200 per 12th inst. J. LEMAITRE.
on St. Etienne.
1,200 17th 23.--LETTER ACCOMPANYING INVOICE OF Goods.
4,000 19th Cognac, May 10th, 1867.
375 15th on Vienna. Mossrs. J. Ellison, Wine Merchants, London.
2,168 14th on Grenoble. Gentlemen, --Agreeable to the order contained in your letter with which we shall do the needful, placing the amounts to your of the 15th of April, and in accordance with the prices and con- credit under advice. ditions laid down, I have bought for your account 20 tierces of Please take note that the following bills have been duly paid: brandy, 27 degrees, and forwarded them to your brother in Paris.
fr. 700 25th ultimo Subjoined you will find the invoice amounting to :
on Grenoble. 30,760 fr., with which I debit you. In conformity with your
2,000 31st wishes, I have drawn on your account, on Messrs. J. Lafitte of
on St. Etienne. Paris, at three months, payable to my order, for the above which amounts we have placed to your credit. amount.
Believe us, dear Sirs, I wrote to you on the subject of your account with me at
Yours truly, length in my last, and have nothing more to add.
M. BERTHOU & Co.
Lyon, le 7 Octobre 1866.
Chers Messieurs,— Nous avons bien reça votre honorée du 3,
Cognac, le 10 Mai 1867. couvrant À Messieurs J. Ellison, Négociants en Vins, à Londres.
fr. 200 au 12 ct. Messieurs, — En exécution de l'ordre contenu dans votre
300 15 honorée du 15 Avril, j'ai acheté aux prix et conditions y fixés,
sur St. Étienne. pour votre compte, 20 tierçons eau-de-vie, 27 degrés, et je les ai
19 expédiés à M. votre frère à Paris. Vous en trouverez ci-joint la
15 sur Vienne. facture s'élevant à :
2,168 14 sur Grenoble. 30,760 francs, portés à votre débit. Pour me conformer à dont nous soignerons le nécessaire à votre crédit sous avis. vos désirs, je viens de disposer pour votre compte, sur MM. J. Veuillez prendre note que les traites suivantes ont été dûment Lafitte de Paris, une traite payable à mon ordre à trois mois payées : pour la somme ci-dessus.
fr. 700 au 25 dernier Je me suis étendu dans ma dernière au sujet de votre compte
sur Grenoble. chez moi, et je n'ai rien à ajouter mes observations.
2,000 31 J'ai l'honneur d', tre, Messieurs,
sur St. Étienne. Votre obéissant serviteur,
dont nous avons passé les montants à votre crédit. FRANÇOIS MARTIN.
Agréez, chers Messieurs,
nos salutations distinguées, 24.-LETTER OF INTROD CTION, AND OF CREDIT.
M. BERTHOU & CIT. Metz, January 15th, 1865, Messrs. Armand Roubot & Co., London,
26.-LETTER FROM AN AGENT ADVISING RECEIPT OF AN Gentlemen,—The bearer of this letter, Mons. F. Decretelle,
ACCOUNT, AND HIS OPERATIONS THEREWITH, of this city, is one of our oldest friends. He purposes visiting
Paris, December 2nd, 1866. England, and we take the liberty of recommending him to your To the Directors of the Western Banking Corporation
(Limited), Manchester. Should M. Decretelle reqnire some funds for travelling Gentlemen, I have herewith the pleasure to inform you that expenses, please to let him have all he wants, to the extent of I have this day received from Mr. Bernard the sum of fr. 250,000, £500, taking his draft on us at three days' sight. Subjoined which, according to your instructions, I have handed over to we send you his signature.
Messrs. Moullyn Bros., requesting them to remit it to you in If you can in any way further the ends for which he has short bills on London at the most favourable rate of exchange, undertaken this journey, we should feel greatly obliged.
or, if it should be more convenient to them, to transfer the above We are at your service on similar occasions,
amount to your credit with one of their London correspondents. And remain, Gentlemen,
I am, Gentlemen,
Your obedient servant,
Paris, le 2 Décembre 1866. herewith beg to inform you that we have to-day received from À Messieurs les Directeurs de la Western Banking Corporation Messrs. Hawkes & Co., of your city, for your account, £4,200, (Limited), à Manchester.
which we place to your credit under to-morrow's date. Messieurs,—J'ai l'avantage de vous informer par la pré
We are, dear Sirs, sente que j'ai reçu aujourd'hui de M. Bernard la somme de
Yours truly, fr. 250,000, que, conformément à vos instructions, j'ai versée
S. BARRETT & Co. chez Messieurs Moullyn Frères, en les priant de vous la remettre en apier court sur Londres au meilleur change
Manchester, 12 Décembre 1866. possible, ou, s'il entrait mieux dans la convenance de ces Messieurs W. Carter et Cie, à Dublin. derniers, de faire transférer ce montant à votre crédit chez un Chers Messieurs,-Sans aucune des vôtres à répondre, nous de leurs correspondants de Londres.
avons l'avantage de vous informer par la présente que nous Recevez, Messieurs, l'assurance
avons reçu aujourd'hui de Messieurs Hawkes et Cie, de votre de ma parfaite estime,
ville, pour votre compte £4,200, que nous passons à votre crédit, FRÉDÉRIC TOURVILLE.
valeur à demain.
Recevez, chers Messieurs,
Nos sincères salutations, 27.-LETTER REFUSING TO SUPPLY GOODS ON CREDIT.
S. BARRETT & CIB. London, January 17th, 1866. Messrs. A. Perrin & Co., Paris.
30.-LETTER ABOUT NON-ACCEPTED BILLS. In answer to your note, I beg to state that it is impossible for
Liverpool, Sept. 28th, 1860. me to open any new accounts. The price of the goods ordered is 570 francs.
Messrs. Costenoble, Lewis & Co., San Francisco. If you will confirm the order, and, as is customary, accompany
Gentlemen,-In answer to your favour of June the 26th, I it by a bank-post bill on London, or a bill payable at sight on
return you the enclosed Bill on Smith Bros. of Paris, I will at once send the articles you desire to your agent.
Dollars 1,950, with the protest for non-acceptance, for the Waiting your reply,
costs of which you will please to credit me with I have the honour to be,
Dollars 3.- I am in a similar position as yourselves, having Gentlemen,
also a bill in hand on the same Smith Bros. of Your obedient servant,
Dollars 1,428, drawn by Jones & Co. of your town, payable LEWIS PRATT. the 20th October, which he has also refused to accept, and
which I enclose, with the protest, requesting you to exact a Londres, le 17 Janvier 1866.
sufficient security from the drawers, and to inform me of the Messieurs A. Perrin & Cie, à Paris.
result. En réponse à votre lettre, j'ai l'honneur de vous informer que occasioning,
Begging you beforehand to excuse the trouble I am je ne puis ouvrir de nouveaux comptes.
I have the honour to be, Gentlemen, Le prix des articles que vous me demandez est de 570 francs.
Your obedient servant, Si vous voulez bien m'en confirmer la demande, et l'accom.
LEWA MARTIN. pagner comme d'usage de son solde en un mandat sur la banque de Londres ou un bon à vue sur Paris, je remettrai aussitôt chez
Liverpool, le 28 Septembre 1860. votre commissionnaire les articles que vous désirez.
MM. Costenoble, Lewis et Cie, à San Francisco. En attendant vos ordres,
Messieurs,-En réponse à votre lettre du 26 Juin, je vous J'ai l'honneur d'être,
renvoie ci-inclus la lettre de change sur Smith Frères de Messieurs,
Doll. 1,950, avec son protêt, faute d'acceptation, dont il Votre obéissant serviteur
vous plaira de me créditer le coût de LEWIS PRATT. Doll. 3.--Je suis dans le même cas que vous-mêmes, ayant
aussi une lettre de change sur ces MM. Smith Frères de 28.--LETTER ACKNOWLEDGING RECEIPT OF REMITTANCES. Doll. 1,428, tirée par Jones et cio, de votre ville, pay.
London, Jan. 22nd, 1864. able le 20 Octobre, dont il a aussi refusé l'acceptation, et Messrs. Daniel Bros., Liverpool.
que je vous envoie ci-incluse avec son protêt, en vous priant Gentlemen,--Your favour of the 7th inst. came duly to hand d'exiger une sûreté suffisante des tireurs et de m'informer du covering your remittances for
résultat. En vous demandant pardon d'avance de l'embarras 148 12 6 pro 18th February
que je vous cause, 225 60 25th
J'ai l'honneur d’être, Messieurs, 420 0 5th March
Votre tout dévoué,
LEWIS MARTIN. £793 18 6 on London, which we place to your credit under usual reserve. We remain, Gentlemen,
LESSONS IN ASTRONOMY.--V.
LATITUDES-MERIDIAN-POLE STAR-GREAT AND LITTLE
Having now given a brief sketch of the history of our science, Messieurs,- Votre honorée en date du 7 courant nous est bien and seen the way in which the most important discoveries in it parvenue couvrant vos remises de
have been effected, we must pass on to the more practical parts 148 12 6 au 18 Février
of the science. We shall, as may be expected, meet with a few 225 6 0 25
difficulties as we advance, and there will be a few definitions 420 0 0 5 Mars
and technical terms that it will be necessary for us to learn ;
but the tax thus imposed on the student will be no very heavy £793 18 6 sur Londres,
one, and the increasing interest which will be felt in the que nous passons à votre crédit sous les réserves d'usage. starry heavens will far more than make amends for any littlo Recevez, Messieurs, nos salutations distinguées, trouble. A. BROWNLOW & CIE. It is usually the best and simplest plan to acquire a general
notion of the scope of any science before entering into its 29,-LETTER ACKNOWLEDGING RECEIPT OF MONEY FROM details—to know the problems which are proposed before we AGENT.
attempt their solution; and so it is best for us to become geneManchester, Dec. 12th, 1866. rally acquainted with some of the phenomena of the stars and Messrs. W. Carter & Co., Dublin.
planets before fully inquiring into the causes of those pheDear Sirs,— Without any of your favours to reply to, we
To accomplish this, let the student on the first clear
night seat himself at a window commanding an extensive view at all, but to remain constantly fixed in the same place, while of the heavens ; or, better still, let him go out in some place all the others revolve around it. This star is called the pole where his view of the sky is as extensive as possible, and watch star, and is well known, for before the discovery of the mari. for a short time the movements of the stars. If the night be ner's compass it was used by sailors as their guide, being situated dark and clear, comparatively few will at first be seen, as the due north. Very frequently, however, cloudy or dull weather pupil of the eye is contracted by the bright light of the room would hide this star, sometimes for many days together, and which has just been left. In a few minutes, however, the eye hence they were unable to go far out of sight of land, and becomes accustomed to the light, and then the whole arch of consequently navigation was but little practised in those days. heaven is seen to be thickly studded with stars. These differ If the student does not know this star, it is important for very greatly in brightness
and size, so that he will soon be able him to find it at once, as it will be of great assistance to him in to fix on a few of the more conspicuous, and turn his main learning the names and positions of others. The difficulty attention to them.
which at first sight strikes us of learning the names of the A compass should now be referred to, so as to ascertain the true constellations soon disappears if we become familiar with a few north and south points, and an imaginary curve passing vertically of the brighter ones, as by referring to them we shall soon be overhead should be traced across the sky between these points. able to identify the rest. Further on in the course of these This line is called the meridian; and it will aid the student at first lessons we shall give illustrations of the position of the stars in if some prominent objects, as, for instance, trees or buildings, can the most important constellations. It will, however, be a great be fixed on to indicate permanently its position. Failing these, assistance to procure a complete set of maps of the stars, or, some poles may be placed in the ground. In observatories, one better still, a celestial globe; and a few hours' observation with telescope is usually mounted on its axis in such a way that it can the aid of either of these will soon enable us to find any star, only be directed to parts of the sky bordering upon this line, and or turn our attention to any part of the heavens which we may this is then known as the transit instrument. Its mode of con- desire. struction and uses will be fully explained by-and-by.
The constellation of the Great Bear (Ursa Major)—or, as it is If now the position of any bright star be noticed, as may be sometimes called, Charles' Wain, or the Plough-is well known done by watching it against some fixed object, like the corner to most, it being a very conspicuous one, and one of those of a house or the trunk of a tree, we shall soon find that it which never set in this latitude. There are & considerable appears to be in motion; and further observation will show number of stars in this constellation, but seven of them are that nearly all the stars appear to be similarly in motion, especially bright, and are arranged as shown in the lower part though the rates at which they travel seem to vary slightly. of the accompanying figure. Four of them seem to form an
Let us now face towards the south, and we shall soon see irregular square, while the other three, situated in the tail of that the stars on our left hand--that is, towards the east-are the Bear, are arranged in a curved line going from one of the rising higher and higher above the horizon; and if we could corners of the square. map out their courses, or imagine them to leave threads of light Careful examination on a clear night will show that the behind them, we should see that all these tracks would be arcs middle star of the tail is in reality double, consisting of two of circles, and would be parallel to one another.
stars so close together as apparently almost to touch one These stars rise higher and higher till they come to the another. They are called respectively Mizar and Alcor. A meridian, and here they are at their greatest elevation above telescope reveals a similar fact with regard to the first star in. the horizon, They then commence to descend towards the west, the tail. We shall find as we further examine the sky many and it will be found that exactly the same time elapses between of these double stars, and a telescope often shows them to be the rising of any star and its coming to the meridian that there of different colours, so that they are' very beautiful objects. is between this period and its setting in the west.
The two stars in the quadrangle which are farthest from the The point in the path of a star or planet on any given day tail are called “the Pointers,” because, if a straight line be which is most elevated above the horizon is called its culminat- drawn on a map so as to join them, and then be prolonged to ing point, and this point is always on the meridian. Hence any about five times the length, it will almost pass through the of the heavenly bodies is said to culminate when it comes to Pole Star, which is the star at the tip of the tail of the Little the meridian of any place. The term meridian signifies mid. Bear (Ursa Minor). This constellation, which is shown in the day, and the line is so called because, when the sun attains its upper part of the figure, is almost exactly the same shape as greatest altitude and crosses the meridian of any place, it is the one we have described, but it is turned in the opposite mid-day there.
direction, and the stars in it are much fainter, the pole star If now we look quite to the south, we shall find that the being the brightest of them all. stars there only describe very small arcs, rising but a little way We spoke of the pole star as remaining at rest; this is not, above the horizon, and setting again in a very short time not however, perfectly correct, as it is not situated exactly at the far from the same point, the highest altitude attained at any pole, but about one and a half degrees from it, and hence it time not being more than a few degrees.
appears to describe a circle of about three degrees in diameter. Now let us turn half round, so as to face the north instead This, however, is so small that it is only by the use of good of the south, and, as before, observe the stars. We shall soon instruments that we can ascertain the fact, and in ordinary use be struck with the difference in the phenomena exhibited. We we may look upon the star as indicating the place of the pole shall row see that some of the stars never set, but describe or imaginary axis round which the whole starry concave appears small circles, crossing the meridian twice in the course of the to revolve. twenty-four hours. We cannot, however, trace them completely As we shall have frequent occasion in our lessons to speak of round their paths, as during a part of the time they are hidden degrees, it is as well for us to clearly understand at once what from the naked eye by the brilliancy of the sun's light. Even we mean by a degree, and the mode in which we may measure by day, however, they may be seen with the aid of a good tele- it. It is clearly necessary for us to have some means of scope, if the means are possessed of directing it to them. It is measuring the apparent distances of the heavenly bodies from said, too, that at the bottom of a well or mine any bright stars one another, and this can only be done by measuring the angle which happen to bo vertically over the mouth may be seen, and which imaginary lines drawn from them to our eyes subtend. some have even seen stars during the day by looking up a If we think a moment, we shall see that it is in the same way chimney. In either case, the rays of the sun are to a great that we fornı our estimate of the dimensions of ordinary objects extent cut off by the walls or sides, and thus the faint light of around us, and hence, when we bring them nearer to the eye the star reaches the eye. It is, of course, only the brighter they appear larger, because the rays drawn from their extremes stars that can be seen in this way, and as the number of stars to the eye contain a larger angle. Now, we want some means of the first and second magnitudes visible at any one time does of measuring and expressing in words the angle thus contained, not exceed fifty, it will easily be understood that it will only be and this we do by means of degrees and fractions of a degree. on rare occasions that these effects will be witnessed.
A degree, then, is the 360th part of a circle-i.e., if we draw a If now we look to a point on the meridian situated about large circle on paper, and divide its circumference into 360 equal fifty-one degrees above the horizon, or rather more than half. parts, and then draw straight lines from these divisions to the way from the horizon to the zenith, as the point directly over centre of the circle, the angle contained between any two adja. head is called, we shall find a star which appears not to move cent lines will be just one degree. On any circle we can drait
on paper these divisions will necessarily be very small; when, similar distance of the south pole never rise at all in our latihowever, we deal with a globe of the size of the earth, we find tude, and hence are never seen. that a degree at the equator measures about sixty-nine miles. This may easily be understood if the student possesses a celes
In a right angle there are, of course, ninety degrees, and if tial globe. Ho has only to elevate the north pole as many we make a triangle with three equal sides, each angle will con. degrees above the horizon as his place of observation is north. tain just sixty degrees. A degree is divided into sixty parts, of the equator, and then, as he turns the globe on its axis, he called minutes; each of these is divided into sixty parts, called will see that the circumpolar stars (as those round the north seconds; and in more accurate observations each of these is pole are called) are constantly above the horizon, while as he again divided into sixty parts, which are called thirds. These looks more towards the south pole, many only just rise for a divisions are usually expressed by the following signs-degrees short time and then set again, and those still nearer the pole (°), minutes (1), seconds ("), thirds (""); thus—13° 28' 5" 12". will never appear above the horizon.
As a general guide to us in estimating approximately the Among the most brilliant of the constellations thus hidden distances of the stars, it will be useful to remember that the from us is the Southern Cross, and when travellers are going apparent diameter of the sun or moon is about half a degree, southward, the first appearance of this constellation is generally whže the distance between the Pointers is about six degrees, anxiously awaited. As the observer approaches the tropics, the and that between the pole and the Pointer nearer to it (Dubhe) pole star seems to sink lower and lower in the sky, and the is about twenty-four degrees. By means of a carefully gradu- number of stars which never set become less and less, till when ated semicircle, we can easily measure any angle, and ascertain he reaches the equator the pole is in the horizon, and all the the number of degrees it contains.
stars are seen rising in the east, remaining visible exactly twelve We will not at present pursue our
hours, and then sotting in the study of the constellations, but as
western horizon. They all appear soon as we have completed our gene
likewise to travel in perfectly ral idea of the movements of the stars
straight lines instead of in curves we will deal more particularly with
as they do in other latitudes, and those that are intimately associated
hence the general appearance of the with us as members of our system,
sky is very different from that seen and then return to consider the more
in England. remote stars.
By placing the artificial globe so As we continue to survey the
that its axis is horizontal, and its heavens for several evenings, we shall
pole in the horizon, we shall obtain soon discover that the stars remain in
a representation of these phenothe same relative position with regard to one another. Just after
If now we could transfer ourselves the new moon, before its light is
to the poles, the whole scene would bright enough to obscure the light
again vary. This has not yet been of the stars around it, we shall
actually done, but some Arctic trabe able to observe its place among
vellers have penetrated very nearly them. Let us carefully note this, and
to the north pole, so that the moveagain examine the spot on the follow
ments of the stars as seen by them ing evening. We shall now find that
were almost exactly as we are about the moon seoms to have been left
to describe. behind by the stars, and instead of
No stars are now seen to rise or appearing in the same position as
set, but all travel in circular paths before, it is some twelve or thirteen
parallel to the horizon around the degrees distant, and thus we learn
pole star, which appears directly that the moon has a motion indepen
overhead.. Hence it is clear that all dent of the rest of the stars.
the stars which are seen at any one On further observation, too, we
time remain constantly visible, while shall detect one or two bright stars
one-half of the entire sky is conwhich in a similar way change their
stantly hidden from their view. position, and hence are called planets,
In a similar way, the changes of or wanderers (for such is the meaning
day and night, of such great importe of the word “planet”). Jupiter is the most conspicuous of these, and
ance to us, are unknown at the poles.
At the commencement of their sum. Venus—sometimes known as the
mer the sun is seen at first only partly Morning Star, and sometimes as the Evening Star, according to elevated above the horizon, but travelling round to all parts of the time when it is visible—is another of them. These planets the sky in the twenty-four hours, while at the same time his appear so bright on account of their comparative nearness to altitude is slowly increasing ; and thus he remains constantly us; they are, however, very different from the fixed stars, as visible for the space of six months, and then, for the remainder they do not shine by their own light, and are greatly inferior to of the year, he never rises above the horizon. The year, therethem in point of size.
fore, consists of but a single day and night. The long night is, There is one other fact with regard to the general appearance however, greatly relieved by twilight, which continues about two of the sky which the student can likewise verify for himself. months after the disappearance of the sun, and is seen a similar Having fixed upon any bright star, let him observe carefully period before his rising. The Aurora Borealis or Northern on any evening the exact time of its passing the meridian, or of Lights, likewise, is seen in great brilliancy. its disappearance behind some conspicuous object. Observe The whole appearance of the Arctic sky is thus seen to be it again on the following evening, and again after the lapse of a altogether different from that of ours. All these varied phenofew more days, and it will at once be found that the star is a mena, however, will be found to admit of one simple explana. little earlier every day in arriving at the place. Thus, if it be tion. on the meridian at nine o'clock one day, it will be there about When we have thus been gazing on the stars and their ceasefour minutes before nine on the next day, and so on.
less motions, many questions come crowding into the mind about It is owing to this that we see different constellations at their distances and sizes, the objects they serve, and the laws different seasons of the year. Many of those which shine they obey. And then our thoughts go further still as we
a winter's night are above the horizon in the sum attempt to inquire what they are, and whether they, like our mer during the daytime, and hence are invisible. In this way world, are inhabited. To some of these questions Astronomy We see by far the larger portion of the stars at some time or furnishes the answers; and as to the rest, though it can give other of the year ; but just as those stars within about fifty no direct information, it furnishes us with a number of facts on degrees of the north pole never set to us, so those within a which we can base our speculations.