ページの画像
PDF
ePub

-en or 11.
-en or n.

LESSONS IN GERMAN.-LII. The distinctive difference between Leute and Männer may be $ 14.-THE NEW DECLENSION.

forcibly shown by reference to the words Eheleute and Chemänner :

Eheleute means married people ; Ehemänner signifies married men, TERMINATIONS.

i.e., husbands. Singular.

Plural.

(2.) Some have no plural, according to the following heads :Nom.

-en or 11.

a. Generic names of material substances; as :-Daß Onli, Gen.

-en or 11.

gold; Silber, silver; Eisen, iron, etc. Dat.

en or 11.

b. General terms and those expressive of abstract ideas; as:Acc. -en or n.

-en or n.

Raub, pillage; Ruhm, glory; bas Diek, cattle; Vernunft, reason; NOTE.—When the singular ends in e, el, or er, the plural Stolz, pride ; Kälte, colă, etc. takes n only.

c. Some names of plants; as :-Der Rohl, the cabbage; Hopfen, EXAMPLES

hóps; Ktesse, cresses, etc. Singular.

Plural.

à. All infinitives employed as nouns, as also all neuter adjec. Nom. Der Graf, the count. Die Grafen, the counts.

tives so employed; as leben, life; Berlangen, wish ; das Weiß, Gen. Des Grafen, of the count. Der Grafen, of the counts. white, etc. Dat. Dem Grafen, to the count. Den Grafen, to or for the counts. e. Nouns denoting quantity, number, weight, or measure; Acc. Den Grafen, the count. Die Grafen, the counts.

as :-Bund, bundle; Dußend, dozen; Orad, degree; Pfund, pound;

Zoll, an inch, etc. Nom. Der Falfe, the falcon. Die Falfen, the falcons.

Thus, in German, we say, neun Klafter, nine fathoms; þuntert Gen. Det Falfen, of the falcon. Der Falfen, of the falcons. Grad, a hundred degrees, etc. Feminines ending in e and words Dat. Dem Falfen, to the falcon. Den Falfen, to the falcons. denoting periods of time, as also the names of coins, are, in Acc. Den Falfen, the falcon. Die Falfen, the falcons.

general, excepted from this rule. (L.) Feminine nouns which are indeclinable in the singular,

(3.) Some, in the plural, have two forms; conveying, in geneare, for the most part, of this declension. Those ending in the ral, different, though kindred significations; as in the following suffix in in the singular, double the n in the plural.

examples :-
Singular.

Plural.
EXAMPLES
Singular.

Plural.

Das Band, Bande, bonds, fetters. Bänder, ribbons. Nom. Die Schuld, the debt. Die Schulden, the debts.

Die Banf, Bänke, benches.

Banken, banks of comGen. Der Schuld, of the debt. Der Schulden, of the debts.

merce. Dat. Der Schulb, to the debt. Den Schulden, to the debts. Der Bogen, Bogen, sheets of paper. Bögen, arches, bows. Acc. Die Scult, the debt. Die Schulden, the debts.

Das Ding, Dinge, things in general. Dinger, little creatures.

Der Dorn, Dornen, thorn-bushes. Dörner, thorns (more than Nom. Die Hirtin the shep. Die Sirtinnen, the shepherdesses.

one).
herdess.

Der Fuß,
Füße, feet.

Fuße, feet (as measures). Gen. Der Hirtin, of the shep. Der Sirtinnen, of the shep- Das Gesicht Gesichte, visions, sights. Gesichter, faces. herdess. herdesses.

Das Horn, Horne, sorts of horn. Hörner, horns (more than Dat. Der Hirtin, to the shep- Den Hirtinnen, to the shep

one).
herdess.
herdesses.

Das Holz, Holze, sorts of wood. Hölzer, pieces of wood. Acc. Die Birtin, the shep. Die Hirtinnen, the shepherdesses. Der laden, Laden, shutters.

Läden, shops. herdess.

Das Land, Lande, regions.

Länder, states. Mutter, mother, and Tochter, daughter, are in the plural Der Mann, Männer, men.

Mannen, vassals. Mütter and Töchter. They add n to the dative.

Der Mond, Monden, months.

Monde, planets. Feminine nouns were originally in the singular declined ac

Der Ort, Orte, places (any). Derter, places (particular). cording to the New Declension. These old inflected forms are

Đic oai, Sauen, wild boars.

Säue, swine. still preserved in certain phrases. Thus : mit or in Ehren, with Die Schnur Schnüre, tapes.

Schnuren, daughters-inor in respect or honour-Ehren, from Ehre ; auf Erden, on earth

law, Erten, from Erte; mit Freuden, with joy-Freuden, from freute; Der Strauß, Sträuße, nosegays. Straußen, ostriches. von or auf Seiten, on the part of—Seiten, from Seite; meiner Frauen Das Wort, Wörter, words unconnected Worte, words (in a soul. Schwester, my wife's sister.

(as in a dictionary). tence). Der Zoll, Zolle, inches.

Zölle, tolls. § 15.-OBSERVATIONS ON THE DECLENSION OF COMMON NOUNS.

$ 16.–FOREIGN NOUNS. (1.) Some have no singular, as in the following list :

(1.) Some nouns introduced from foreign languages retain Aeltern (Eltern), pa- | Fußstapfen, footsteps. / Masern and Rötheln, their original terminations; as: Der Mericus, a physician; plur. rents. Gebrüder, brothers. measles.

Medici, physicians; Factum, deed ; Facta, deeds. Ahnen, ancestors. Geschwister, brothers Molfen, whey.

(2.) Some masculines and neuters from the French and the Alpen, alps.

and sisters. Dstern, Easter. Beinfleiter, small Gliermaßen, the limbs. Pfingsten, Whitsun. in all the cases of the plural ; as, nom. der Lord, the lord; gen.

English merely affix $ to the genitive singular, which is retained clothes.

Händel, quarrels. tide. Blattern, smallpox.

def Lords, of the lord; plur. die Porbe, the lords, etc.; der Chef

, the Hosen, trousers. Rånfe, tricks. Briefschaften, letters, Insignien,

chief; gen. des Chefs, of the chief ; plur, dic Chefs, the chiefs, eto.

marks, Repressalien, reprisals. papers.

badges.

Tråber Ireber, $ 17.- FOREIGN NOUNS OF THE OLD DECLENSION. Einkünfte, revenue. Kosten and Unfosten, husks, less. Fasten, Lent, fasts. costs.

Trümmer, ruins.

(1.) Foreign nouns of the neuter gender, as also most of the Ferien, holidays. Leute

, people, folks. Weinachten, Christmas masculines, are of the Old Declension. NOTE.—Leute merely expresses plurality of persons. In this of persons ending in the following terminations :

(2.) Among the masculines must be noted those appellations it differs from Menschen (human beings), which has regard to the kind or species, as also from Männer (men), which denotes parti

al; as, Kardinal, cardinal. cularly the sex. Those compounds, however, of which, in the

ar; as, Notar, notary. singular, Mann forms the last part, take generally, in the plural,

an; as, Kastellan, castellan. Peute instead of Männer ; thus :

To which may be added Abt, abbot; Propft, provost ; Part Singular.

Plural.

pope ; Bischof, bishop; Bürgermeister, mayor; Spion, spy; Patret Arbeitsmann, workman. Arbeitåleute, workpeople. patron ; Offizier, officer. Gbelmann, nobleman. Grelleute, noblemen.

(3.) Some have, in the plural, the form e (c+t); as --Hobie Kaufmann, merchant. Kaufleute, merchants. tal, hospital ; Spital

, hospital; Kamisol, waistcoat; Regiment

, regiLandmann, countryman. Landleute, country people. ment; plur. Hospitaler, hospitals; Spitäler, hospitals, etc.

[ocr errors]

(4.) Some, in the plural, soften the radical vowels; as :-Abt, tube-dweller, lulled into a false security, stretch forth its abbot; Altar, altar; Bischof, bishop; Chor, choir ; Choral, choral. tentacles to meet the welcome wave, and a pointed head is song; Hospital, hospital ; Spital, hospital ; Kanal, canal; Caplan, adroitly insinuated. The mouth effects its tenacious grasp on chaplain ; Kardinal, cardinal; Kloster, cloister ; Marso, marsh ; the yielding tissues, and the tenant of the tube becomes food for Morast, morass ; Palast, palace; Papst, pope; Propít, provost; the Nemertes Borlasii, for such is the name of this cord-like freeplur. Aebte, abbots; Altäre, altars; Bischöfe, bishops, etc.

booter. Mr. Kingsley appears to have taken more than ordinary

interest in the habits of this strange creature. Speaking of it, $ 18.-FOREIGN NOUNS OF THE NEW DECLENSION.

he inquires, “Is it alive? it hangs helpless and motionless, a (1.) To the New Declension belong all foreign nouns of the mere velvet string, across the hand. Ask the neighbouring feminine gender, and nearly all masculines which are the appel. annelids, and the fry of the rock fishes; or put it in a vase at lation of persons ; as :--Der Student, the student; der Jurist

, the home, and see. It lies motionless, trailing itself among the lawyer; der Elephant, the elephant; der Dufat, the ducat; der gravel. You cannot tell where it begins or ends. It may be a Komet, the comet; der Planet, the planet; der Konsonant, the conso- strip of dead sea-weed-Himanthalia lorea perhaps, or Chorda nant; ber Prinz, the prince; der Tyrann, the tyrant, etc. filum-or even a tarred string. So thinks the little fish who $ 19.-FOREIGN NOUNS PARTLY OF THE OLD AND

plays over and over it, till he touches at last what is too surely PARTLY OF THE NEW DECLENSION.

a head. In an instant a bell-shaped sucker mouth has fastened

to its side ; in another instant, from one lip, a concave double (1.) These are, first, neuters ending in fiv; as :-Das Pasīv, proboscis, just like a tapir's (another instance of the repetition the passive; gen. Passivs, of the passive; plur. Passiven, the pas. of forms), has clasped him like a finger. And now begins the sives; secondly, titles of males in or; as :-Doctor, a doctor; struggle, but in vain. He is being 'played with such a fishing. gen. Doctors, of a doctor; plur. Doctoren, doctors; thirdly, neuters rod as the skill of a Wilson or a Stoddart never could invent; a ending in al, il, and um, which also often have i before the living line, with elasticity beyond that of the most delicate fly. en of the plural; as :-Kapital, a capital; plur. Kapitalien, capi- rod, which follows every lange, shortening and lengthening, tals; Fossil, a fossil; plur. Fossilien, fossils ; Studium, study; plur. slipping and twisting round every piece of gravel and stem of Studien, studies ; fourthly, the following masculines :-Fasan, sea-weed with a tiring drag, such as no Highland wrist or step pheasant; Rapaun, capon; Konsul, consul; Pantoffel, slipper; Prās could ever bring to bear on salmon or trout. The victim is tired feft, prefect; Pialm, psalm ; Rubin, ruby ; Staat, state; Traktat, now, and slowly yet dextrously his blind assailant is feeling and treatise ; to which add Insekt

, insect; Atom, atom ; Pronom, pro- shifting along his side till he reaches one end of him; and then noun ; Statut, statute; and Verb, verb; which are neuters.

the black lips expand, and slowly and surely the curved finger begins packing him end foremost down into the gullet, where he

sinks inch by inch, till the swelling which marks his place is RECREATIVE NATURAL HISTORY. lost among the coils, and he is probably macerated into a pulp SOME LAND, SEA, .AND FRESHWATER SHELLS—WORMS, AND

long before he has reached the opposite extremity. Once safe

down, the black murderer contracts again into a knotted heap, TUBE-DWELLERS (continued).

and lies like a boa with a stag inside him, motionless and blest." On the eggs deposited at the bottom of the thorn-coated tube Our illustration represents the living line in the act of capby the oiketicus grub giving forth their tiny brood, the young turing its prey. worms immediately crawl forth, and at once proceed to spin Here, then, to his siesta and the enjoyment of his ruthlessly silken sheaths for themselves. These they bear with them as gained spoils we will leave the Nemertes Borlasii, and see what convenient overcoats as they travel through the tangled and that long-eared, brown, odd-looking, slug-like creature is, which thorn-decked twigs and branches of the tree, feeding and we observe crouching like a hare in its seat just above the gathering together such thorns as may be found adapted to home of our greedy friend the worm. This is the sea-hare, or castle-building purposes. These, as they are gleaned, are sea-cow (Aplysia punctata). The terms “hare" and "cow” arranged in order, point downwards and side by side ; a power- have been given to it in consequence of the two horn or earfully adhesive fluid and a layer of silken filaments completing like appendages to the head. It is curious sometimes to note the union. The growth of the worm is rapid, and it soon how strangely appropriat some of these trivial designations becomes large enough to fully occupy its bayonet house, and are found to be. In this case the resemblance to a grasscarry out the destiny we have already shown it as fulfilling. feeding and ruminating animal extends beyond the mere fanciful Of worms dwelling without the protection afforded by sheaths contour of the creature's external form. The interesting rewe shall find numerous examples in the earth, the river's bed, searches of Professor Grant have brought to light the fact that the sea's bottom, and in the tissues and cavities of living the Aplysia punctata, like its fur-clad and horned namesake, the organisms.

cow, has three stomachs, the first being formed by an opening Let us pay a visit to the clear, shell-strewn rock pools, and out or dilatation of the bottom of the gullet. This food-sack is open stretches of tide-deserted sand, and should good fortune of a curved form, not unlike the air-chamber of a set of bag. favour us, we shall find food for observation and research ; and pipes; and in it is generally found the particles of freshlyas we peer down into the clear water, or lift some weed-grown gathered sea-weed on which our tiny cow has been feeding. The pebble or fragment of broken rock, some beautiful and marvel- next or centre stomach is the smallest of the three, and performs lously perfect examples of the Creator's wisdom will be brought much the same kind of duty as the gizzard of a bird; being, in to light. Strange, weird, grotesque, and anomalous as some fact, a sort of internal grinding mill, in which, by the aid of a of these ocean creatures may, to the heedless or casual observer, set of hard, dense, and tooth-like processes, the food is commiappear, they only require the investigation of the observant and nuted, crushed, and pressed until in a fit condition to pass on to thoughtful to prove them worthy of our keenest interest and the third receptacle, which is of most curious construction, being deepest admiration.

furnished within with a rake or comb-like arrangement of teeth Down amongst the sea-weed stems and pointed rocks we or spiculæ, which card and rake the ground-up substances, and perceive a long, black, tangled string, like a giant's leather boot-fit them for the action of the gastric fluids and final digestion lace set to soak; let us trace it in its various folds and twists, and assimilation. and disentangle some of it; we shall then have in hand a tough, Few marine productions have had a greater number of odd slippery, india-rubber-like substance, which might well be pro- and wild superstitions associated with them than the Aplysia nounced a sea string, and classed with the long trailing weeds punctata. Some of these have no doubt arisen from the fact of amongst which we have found it. A sea string it is, but not a its pouring out from its tissues, when placed in a goblet of weed; in fact, a living lasso, capable of consuming the prey it water, a large quantity of a most peculiar fluid, which tinges! encloses within its treacherous folds. From twenty to thirty the surrounding water of rich full purple tint; this, although feet is no uncommon length for this artful animated fishing-line beantiful to a degree, has been found to be too unstable and to reach, but its diameter rarely exceeds an eighth of an inch. liable to change to admit of its being successfully made use of It has a mouth, however, capable of considerable distension and as an artist's colour. The term depilans has been conferred on holding power. What can appear more innocent than this one kind of sea-hare, from an idea which prevailed amongst the delicate-looking creeper trailing here and there as the heaving ancients, and is still in force amongst the coral-finders and water wells and flows as the tide comes in? Let an unwary fishermen of the Mediterranean, that wherever the duid exuded

[ocr errors]

by it touches the human head, the hair, being at once destroyed, red linear marking, as though drawn beneath the skin with a red falls off, leaving a bare spot; added to this, a variety of ailments, crayon. Mark its action closely, and you will see, at intervals more or less formidable, were supposed to fall to the lot of any of a few seconds of time, that it gradually fades from the sight, person rash enough to handle the much dreaded hare.

again dilates, ebbing and flowing as the tide of minute life Bohadsch describes a most oppressive vapour or exhalation, wells through it. This is the creature's grand central blood. which he says he found given off by the Aplysia when laid on a tube, or heart, conveying and propelling the red or arterial plate for investigation. Darwin speaks of his finding some of blood from behind forwards, whilst beneath the body another the hare family at the Cape Verd which possessed the power duct, equal in importance but not so plainly seen, conveys the of causing a sharp stinging sensation to the fingers when blood through the system in the opposite direction. In addition brought in contact with the secretions they threw off. Amongst to these two great longitudinal blood channels, there are four the ancient Romans the sea-hare was held in the most dire others, so arranged that one traverses above the intestinal dread, and nothing was too baneful to lay to its door. It is canal, one below it, one on the right side, and another on the related of Locusta that she made use of the sea-hare as one of left. These are all placed in communication by branching or her most potent ingredients in the preparation of the poisons" anastomising" vessels, running like the centre line in the destined to remove the secret enemies and plotters against Nero, I letter 1. Here, then, in this apparently insignificant worm, we

[graphic][ocr errors][ocr errors][merged small]

and that at length, when fully conversant with the qualities of a have a beautifully perfect form of double circulation. Added to hare potion, she prepared an extra strong one for the especial this, we find that the Nereis margaritacea is possessed of two delectation of royalty itself. It will also, perhaps, be borne in pairs of eyes of a deep, rich blue colour ; a pair of singularly mind that Domitian was openly charged with having given formed and ball-tipped horns, and eight delicately fine and sensea-hare poison to his brother Titus. Rigid laws were enacted sitive feelers, or whiskers, between which is situated a flexible prohibiting even the search after this dreaded slug of the and retractile proboscis, or snout, by the aid of which food is sea, whose formidable qualities existed only in the fertile and gathered from holes and crevices too small for the admission of perverted imaginations of those who preferred dread to inves- the body of the worm. tigation, and mythical romance to plain reality.

As we travel onwards, where the ripple mark left by the As we wander on, and prosecute our stone-mining operations, receding tide still holds a silken thread of sea-water between we shall scarcely fail to uncover one or more members of an its waved grooves, we shall see before ns tiny heaps of sand exquisitely beautiful class of annelids, known as the pearly cast up, as though some diminutive mole of moist habits had nereis (Nereis margaritacea). These curious creatures in form been at work below. Most of these will be found to be the somewhat resemble small centipedes, but a little close scrutiny work of a much larger member of the family of annelids, in will serve to bring under the

observation of the investigator a form and habits closely resembling the lumbricus, or earth-worm rich and varied collection of tints, pearl, opal, violet, and of our fields

and gardens; but we must reserve a consideration of metallic green. Look closely along the line where, in a verte- them and their sea cousins, whose works we have just been brated animal, the back bone should be, and you will see a deep examining, until our next lesson.

95

LESSONS IN ASTRONOMY.--VI. some this may seem a question pertaining rather to geography

than to astronomy. It is, however, intimately connected with THE SUN AND MOON-MOTIONS OF THE EARTH-ITS FIGURE

both sciences; and, as the earth is our stand-point of observa-FLATTENING AT THE POLES——PROOFS THAT THE EARTH tion, it is of paramount importance to understand something IS ROUND-HOW SUPPORTED IN SPACE-RATIONAL AND about it first of all. SENSIBLE HORIZONS.

The form of the earth, then, is almost spherical, but not THE great apparent size of the sun and moon, as compared with absolutely so; for it is somewhat flattened at the poles, so that a the rest of the heavenly bodies, often leads us to overlook them section passing through them would be slightly elliptical instead when we think or speak of the stars, and to regard them as of circular. This deviation from the spherical form is, however, belonging altogether to a different class. Hence we usually very slight; so slight, indeed, that it would not be seen in any look upon astronomy as a science to be studied only by night, model that we could make. Suppose, for instance, we made a when in reality the star on which we are most dependent, and globe with a diameter of thirty inches, the difference would only whose movements with regard to us are of the greatest import- be to of an inch, too small for even the keenest eye to detect. ance, is the sun whose presence causes our day. We use the The real dimensions are almost as follows: term "star" here advisedly, for the sun is in reality to be classed as one of the fixed stars, the reason of its great apparent

Greater or Equatorial Diameter

7925} miles. Lesser or Polar

7899 size and brilliancy being merely that it is very much nearer to ns than any of the rest, its distance being reckoned by millions showing a difference of a little over twenty-six miles. of miles only, while that of even the nearest fixed star requires Several important effects arise from this. The surface of the billions to express it.

earth near the equator is, of course, farther from the centre The moon, though ranking next to the sun in its importance than the surface near the poles; and as the attraction of gravitato us, is in reality the smallest of all our neighbours in space tion diminishes with the increase of distance, it is weaker at the which can be detected by the unaided eye. It will, however, be equator than it is further north or south. at once understood that both it and the sun will, on account of If a pendulum be accurately adjusted so as to beat seconds in their importance to us, claim a large share of our attention. the latitude of London, and then be moved further south, it Now, as we have already stated, the

will, from this cause, beat more slowly. sun, the moon, and all the stars appear

So likewise, if a spiral sprirg be susto be in constant revolution around us,

pended from a hook and a weight hung and most of the phenomena we referred

from its lower end so as just to touch to in our last lesson would be explained

the stand, it will be found, if we convey by imagining all these bodies to be fixed

it carefully, that as we approach the to the inner surface of a hollow sphere

equator the spring will be somewhat in the centre of which the earth was

Fig. 5.

shortened, and the weight will no longer situated, and then sapposing this sphere

touch the stand as it did before; the to be in constant rotation. One

weight, in fact, appears to be less end of the axis on which it 忠

than it was in the higher latitude. tarned would in this case be

A little consideration will soon close against the pole-star, and

Fig. A

show us the cause of this flattenthe other in the part of the sky

ing of the earth. If we suspend diametrically opposite to it. This

a child's pail, filled with water, was, accordingly, for a long time

by a piece of string, and then by the received notion, and it is the one

twisting the string cause it to turn which would naturally strike an observer

round rapidly, we shall at once see the at first, for the earth seems to be at

liquid leaving the centre and becoming rest, nor can we in any way by our

heaped up against the sides, and, if the senses discover that this is not the case.

motion be sufficiently rapid, a portion The reason of this is that motion is to us

will be thrown off and scattered from & relative idea, and if we ourselves and

the edge. A similar but more concluthe objects around us are moving along together at exactly the sive experiment may be tried with a common hoop, which for same rate, we do not observe the motion. If, for example, we this purpose should be made as thin as possible. Let it have are seated in the cabin of a boat when the water is perfectly calm two holes drilled through its sides opposite to one another, and the vessel is being propelled at a uniform rate, we are quite and let it be placed vertically on a pivot in such a way that it unconscious of the movement. If, however, the motion be not can be caused to rotate rapidly; the upper side, however, uniform, but consist of a succession of jerks and shakes, as when must not be fastened to the pivot. On spinning it rapidly, it travelling in a railway train, or if we look on the fixed and stationary will at once be seen that the hoop becomes longer and flatter objects around, we shall soon become conscious of the fact that from the action of centrifugal force upon it. we ourselves are being carried along. Now, as the motion of The same reasoning applies to the earth. It is a body in rapid the earth is perfectly uniform, and all terrestrial objects, includ. rotation on its axis, and hence there is a tendency in all the ing the air, move with it, it is only by looking to the stars that particles of matter composing it to become heaped up at the we become conscious of our movement.

equator, for the motion there is manifestly more rapid than at We cannot here go into all the reasons which prove that this the other parts of its surface. Careful calculation confirms this is the case, but we can easily see enough to satisfy any thought- theory, by showing that the difference between the two diameters ful mind. We have only to look at the earth as a globe about of the earth is just the amount that would be produced by this 8,000 miles in diameter, and to remember that the diameter of cause. the sun is 111 times as great, and that all the stars are large There are many familiar proofs of the rotundity of the earth. globes situated at enormous distances from us, and then ask One of the simplest of these is afforded by watching the deparwhich is the more probable, that these mighty orbs should all | ture of a vessel from a seaport town. As a large objort is travel at an utterly incredible speed around this small globe on always visible at a greater distance than a small one, we should which we live, or that the earth should itself turn round on its naturally expect that the masts and rigging would disappear first axis? If the former is true, the more remote stars must dash in the distance, while the hull would be the last thing to fade through billions of miles in a single second of time, and all the from sight. Observation, however, soon shows us the contrary. Test must be in rapid motion, round a body very much smaller The whole ship remains visible till it has left the shore some than themselves ; by the latter theory, all this is done away little distance, and then it seems to be gradually sinking; the with, and we simply see the earth rotating so that a spectator lower part of the hull being the first to disappear, and then the on its surface is turned in the course of a day and night towards bulwarks, while the tops of the masts are the last things hidall parts of the sky.

den, as seen in Fig. 5, which is, however, purposely exaggerated Having thus settled in our minds the fact of the motion of The reason of this evidently is that something is the earth on its axis, we must next inquire as to its shape. To between the observer and the vessel, and that somet

11

VOL. IV.

bulge or curve of the earth's surface. When the hull has just object some distance above its surface, a support of some kind begun to disappear from a person standing on the surface of the must be used to resist this attraction, ground, the whole will be visible to an observer on an elevated Now the only body which exerts a sufficiently powerful building ; and if there be a lofty mountain near by, the vessel influence on the earth to have much effect is the sun: to it, will be seen from this after every portion of it is hidden from accordingly, the earth would speedily fall were it not that ita those on the beach. This shows that the surface of the earth is own momentum in its orbit is just sufficient to overcome this curved, and, in fact, a rough estimate of the size of the earth attraction. These two forces are so beautifully balanced that may be formed in this way. We have only to fix upon two ele- under their joint influence the earth moves evenly round in its vations of equal height-as, for instance, marked places on the elliptical orbit. At a certain part of the year-namely, in the masts of two vessels-and ascertain the exact distance at which middle of winter—the earth is nearer the sun than at any other they are hidden from one another by the curvature of the earth. time; and, as we saw in our lessons on Mechanics, attraction We must know also the elevation of the places on the masts increases inversely as the square of the distance, the attraction above the level of the sea, and then by a simple proportion we of the sun is therefore greater at this period, and we should at shall obtain the diameter of the earth. The question will be first expect that since this is the case, the carth would approach. stated thus :- As the height of the station of observation is to it nearer and nearer with ever-increasing speed, till at last the the distance of the visible horizon (which is half the distance momentum would be quite overcome, and it would fall into the between the two stations), so this distance is to the diameter of sun and be consumed. the earth.

No such result, however, happens, for as soon as the earth There are considerable difficulties attending this plan, which begins to approach the sun, it is, as it were, rolling down hill; prevent our arriving at very accurate results by it. When it is its speed, therefore, increases, and with this its momentum, so tried at sea, there is great difficulty in ascertaining the exact as to more than overcome the increased attraction; and thus distance of the vessels, as well as in choosing a day when the the earth, having passed the end of the ellipse, begins to recede surface of the water is sufficiently smooth ; and on land it is again. During the next half of its orbit it is receding from seldom that a large tract can be chosen sufficiently level to the sun, which is therefore drawing it back, and checking its answer the purpose, as, even in large plains, there are frequently speed; so that gravitation again becomes the more powerful undulations or slopes which would materially interfere with the force, and the earth commences again to approach the sun. In accuracy of the results. In addition to this there is another this way the two forces alternately preponderate, and by their cause of error introduced by the action of the air on the rays of joint action the earth constantly keeps to its orbit. light, or, as it is termed, refraction. The effect of this is, as Let us, then, all through our lessons bear in mind these facts will shortly be seen, to bend the rays out of their straight that the earth is an almost spherical body, rotating constantly course, and thus to render the object visible when in reality the on its axis, and that it is suspended freely in space, while it curvature of the earth intervenes between it and the observer. describes its journey round the sun in the course of a year. It enables us, in fact, to see to a certain extent round the bend. As we have several times spoken of the horizon, it will be

From these causes, this plan of measuring the earth has not well for us distinctly to know what we understand by it, as been fully carried out. Roughly, however, we shall find that sometimes there is a little confusion on this matter. two places elevated ten feet become hidden from one another at The rational or true horizon is an imaginary plane drawn a distance a little under eight miles; that is, a straight line through the centre of the earth, so that the line where it cuts drawn from one of these to the other would just touch the earth the surface is everywhere equidistant from the observer. If we midway between them. The curvature, then, may be set down take an orange or an apple, and divide it into two equal poras ten feet in three miles and seven-eighths, and we state our tions, or place a ring round it as shown in Fig. 6, so that it sum in the following way

is midway between the eye and the stalk, it will represent the As 10 feet : 31 miles :: 31 miles : diameter of the earth.

horizon. In an ordinary celestial globe, if the pole be elevated

to the latitude of the place, the situation of the wooden horizon We shall find that this gives us about 8,000 miles as the will correspond with that of the rational horizon to the observer. diameter of the earth, which is not far from correct. The more Thus it will be seen that if this plane be extended on all sides accurate mode of ascertaining its dimensions is by measuring an to the sky, it will divide it into two exactly equal hemispheres, arc of the meridian in a way that will shortly be explained. one of which will be visible to the observer.

There is another very conclusive proof of the rotundity of the There is, however, another sense in which the word horizon is earth which should just be referred to-namely, that afforded used. On ascending any height a line will be seen all round us, by the shape of its shadow. The earth is an opaque body, and where the earth and sky appear to touch, and this is called the must therefore throw a dark shadow ; but the shape of this can sensible or visible horizon. only be seen when there is some object on which it can be At sea, or on a level plain, this line will be seen to be a per. thrown. Now, there is only one object which ever comes near fect circle; on land, the elevations of the country usually interenough to us to receive this, and that is the moon. We must fere with the outline : still we can perceive that it is of a circular wait, therefore, till the moon comes directly in a line with us form, and that our point of observation is situated exactly in and the sun, and then we shall see the shadow. Now when this the middle of it. happens, it is called a lunar eclipse; and if we watch the moon The size of this circle increases with our elevation above the as it enters the shadow of the earth, and again as it leaves it, earth. Hence, when a sailor wants to know if any ve uzel is in we shall find that the dark line is always curved to an arc of a sight, he ascends to the mast-head, where his view is much more circle. The earth, therefore, must either be a globe or a flat extensive than if he had remained on the deck of the vessel. circular disc; and at first sight we might incline to the latter In the same way, if we ascend any lofty mountain, we gain a view, and imagine, with some of the ancients, that we dwelt on very extensive view of the country round. If we could be a flat surface like the top of a round table. When, however, we placed at a great distance from the earth-as, for instance, on notice that, in whatever position we happen to be with regard to the surface of the moon-we should see just one-half of the the sun at the time of an eclipse, the shadow is always circular, globe, and the rational and sensible horizons would then exactly we soon are assured that the earth must be globular, as no other coincide. This, of conrse, cannot be, and the highest elevation figure would always cast a circular shadow.

over yet reached by man, or that in all probability ever will be Having clearly realised the fact of the earth’s rotundity, we attained, is so small in comparison with the diameter of the have next to look upon it as a body suspended freely in space earth, that only a small portion of the earth has ever been without any support. According to ancient ideas, Atlas bore visible at once. The largest amount over thus seen was by ap the world on his shoulders ; and many of the Hindoos of the Messrs. Coxwell and Glaisher

, when they attained in a balloon present day assert that it is supported by a serpent and a an elevation of about six and a-half miles, and then about sales tortoise. It is clear, however, that these attempted solutions of of the surface of the globe was in sight. the difficulty only remove it one step further, for we should The following general rule will enable us to calculate approxi

. have to seek some support for the man or the serpent. The mately the distance of the visible horizon when the height of real difficulty arises from our not clearly understanding that the the station of observation is known:-Express the height in reason why a body falls to the

earth is simply because the earth feet and increase it by a half, then extract the square root, and has an attraction for it. Hence, if we want to sustain any this will give

the distance in miles. Thus, if & tower be 18

« 前へ次へ »