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aut. Stuer compound metals, such as compasses, drawing at newISSIER. We all proceed to describe the most auta berwude to snow their application.

her or Straight-edge.--This instrument geneconst. of the bevelled edge of the plane or diagonal scale, coumor Gunters scale, of an ordinary foot rule, or of a pal flat rule made with a fine straight edge, for the Cole purpose of drawing straight lines from one point to another, or through any two points. It is sometimes made in the form of a right-angled triangle (Fig. 1), with a similar edge, to serve the various purposes of drawing straight lines, perpendiculars, rightangled triangles, and parallel straight lines. In the mechanical arts, a straight line is most readily obtained by fixing a well-chalked string firmly at both ends over the place where it is wanted, on a board or stone, raising it, when tense (i.e., stretched), above the same, and then letting it drop suddenly, when the white or chalky trace of the string will be marked on the board or stone as a straight Jine.

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The Parallel Ruler. This very useful instrument is constructed in a variety of forms. Those represented in Figs. 2, 3, and 4, are the most common, and the cheapest. The defect of the construction in Fig. 2 is, that in drawing a parallel to a straight line through a given point, if the latter be at a considerable distance from the former, the ruler may, from its

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lateral motion, pass the point altogether, and render the problem nugatory. This defoot is obviated by the construction in Pigs, 3 and 4, provided they be properly managed; but this management is the result of a little practice.

The triangular ruler represented in Fig. 1 being made to slide against a fixed ruler or straight-edge, as represented in Fig. 5, is frequently employed for the purpose of drawing parallel straight Ps In many cases this apparatus will be found even more Samir for this purpose than the parallel rulers represented em Fr. 3 represents the same triangle in two different positions, and not two separate triangles.

In order to tost the accuracy of a ruler, let it be applied to one eye, and viewed along its edge from one end to, the other; the slightest departure from the straight line will then become visible A good ruler, besides having a straight edge, must be perfectly flat and even, flexible, and made of wellseasoned wood. Some are made of ivory, bone, and metal; these are loss liable to be affected by changes in temperature, or by the humidity of the atmosphere Parallel straight lines are most easily drawn by artists and mechamos, with an For a T mquam, of which the form is distinctly noted by the name

The charm of compasses there are several kinds. This Mnstrument, which mamally consists of two equal legs jointed at VWO ON BVMTEX, in employed for measuring the lengths of straight The daring and laying of distances, and describing eines silva în general The Predix, or compasses with tel in Plan & are chrotte used for dividing equal parts or into parts having any other Anthon The best kind are furnished with ghiening the screw-axle at the joint. Others

are furnished with an arc and tangent screw to fix the legs at any required distance apart.

The Socket Compasses, represented in Fig. 7, are furnished with movable points, or pieces, which can be inserted in the socket at pleasure, according to the use which is to be made of them. It is chiefly employed in describing, that is drawing circles, in ink, or in

Fig. 7.

Fig. 8. Fig. 9. Fig. 10. pencil, or in mere trace. The tracingpoint in Fig. 7 is furnished with a joint and a screw, in order to keep it perpenFig. 6. dicular to the paper when the legs are stretched to a great length. The ink-point, represented in Fig. 8, is furnished with a screw, to admit more or less ink at pleasure, with a joint for the same purpose as the tracer, and with a joint in one of the leaves of the point to admit of its being cleaned. The pencil or crayon-point, represented in Fig. 9, is furnished with a joint for keeping the pencil or crayon perpendicular to the paper, and a socket or case for holding it. The socket compasses are also furnished with a lengthening bar, represented in Fig. 10, which is furnished with a socket exactly the same as that of the leg, in order to admit of the description, that is, the drawing of larger circles than those which can be drawn only by the use of the movable points and legs of the compasses.

The Bow Compasses, so called because in their first construction they could be shut up into a hoop, which served as a handle to them; or the Plug Compasses, represented in Fig. 11, and so called because the stationary leg screws out and in like a plug, are only used for describing circles of a very small size. Such compasses are of the greatest utility to draughtsFig. 11. Imen and engineers in drawing their plans. The plug construction seems to present some advantages over the old bows.

Fig. 12.

Beam Compasses are employed for describing circles of very large radius, and such as are far beyond the reach of a case of mathematical instruments. They consist of a long beam or bar, carrying two brass cursors, that is, pieces on which it runs. One of these is fixed at one end, and the other slides along the beam, and is furnished with a screw to fix it at any required distance. To the cursors may be screwed points of any kind, whether steel tracers, pencils, or crayons, or ink points. This apparatus is represented in Fig. 12. To the fixed cursor there is sometimes applied an adjusting or micrometer screw, as seen in the figure, to enable a given distance or radius to be taken with the greatest nicety.

In a case of mathematical instruments are also contained a Por and Pong Pen, for drawing straight lines in trace, or in ink. These two are usually joined in one instrument, the tracing point being screwed into the drawing pens this instrument is represented in Fig. 13, where the ink-point is constructed exactly on the same principle as that of the socket compasses. In choosing a drawing pen, it is better to select one which has an ink-point made of German stiver. The steel ink-points are apt to get rasty if they are not kept carefully wiped and lines Fig. 13. drawn in red ink with a steel-pointed drawing pen soon get discoloured, owing to the action of the ink on the metal while in the pon

ANIMAL PHYSIOLOGY.—III.

THE EYE (concluded).

THE eyes of the animals lower than fish, none of which have a backbone, and which are called invertebrate animals, are closely related to their powers of moving from place to place. If an animal can dart rapidly about, more especially if it can move swiftly for some time at a stretch, its eyes are usually very perfect; but if it can only crawl sluggishly, its eyes are of an inferior structure.

If we omit those lowest of all animals, which Cuvier classed together as radiate, because their parts were disposed like the spokes of a wheel, the rest are divided into two great subkingdoms. The type of the one, called mollusca, is the snail; and of the other, named articulata, the honey-bee is the representative.

It is impossible to say which of these two sub-kingdoms is the highest, but they are very different. That of which the insect is the type is noted for the swiftness and agility of the movements of the animals that form it; while the other is equally remarkable for the sluggishness of the species which compose it. Indeed, the word just used is derived from this peculiarity in the slug.

These peculiarities are, however, but general ones, applying to most, but not all the species of each sub-kingdom; for each sub-kingdom contains several thousands of different kinds of animals. Thus we find some insects more inert than most slugs, and some of the slug class as active as many insects.

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outside. The rest of the slugs and snails, which creep on their bellies, have eyes somewhat similar, and similarly situated; but while the garden-snail has four horns, some water-snails have only two, and the eyes are placed on the outside of these, halfway up, while the whip-like extremities act as feelers, as the short horns of the garden-snail do. The lower orders of the mollusca, such as the oyster, etc., have eyes inferior even to these, though they are sometimes numerous and curiously placed; thus, the kind of oyster which occupies the fan-shell, and is called a pecten, has a row of eyes running round the edge of the two sides of the animal's cloak, which lines the two shells that enclose it.

The highest class of mollusca have greater power of motion than any of the rest, and swim rapidly through the sea, both backwards and forwards, seizing their prey with long, whip-like arms: and these creatures have large and elaborate eyes, not unlike those of animals, but even more complex in some respects; for there is not only a thin retina to receive the light, backed, as the retina always is, by a black membrane, but behind this choroid is another expanded retina, as though this had some other office

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In accordance
with what has
been written, the
eye of the garden-
anail is evidently
an organ not at
all comparable to
eyes we have de-
scribed as those of
the higher classes. This eye is situated at the end of the longer
and upper pair of horns, and is only exposed when these are at
their longest. Even when so exposed its sense of sight is so
obtuse that it seems only conscious of light and darkness, as our
skin makes us conscious of heat and cold, and has no knowledge
of images. The organ seems little better than a refined organ of
touch, for garden-snails will withdraw their eyes far sooner if
blown upon, or the hand be placed between them and the light,
than when threatened by the fingers. Nevertheless, the eye
has a spherical lens, sclerotic, choroid, and retina, but all of
very simple structure. The most remarkable circumstance con-
nected with this eye is that it can be retracted by drawing
it down through the tubular horn, as one might draw the end of
the finger of a glove down through the rest of the finger; and
this is done by a special muscle, which is a slip of the great
muscular band, with which the snail draws in, not only its horns,
but its whole head, strongly though slowly.

I. VERTICAL SECTION OF THE EYE OF AN INSECT. II. THE LENSES AND CONES ENLARGED. III.
FRONT OF HEAD OF DRAGON-FLY, SHOWING THE POSITION OF THE COMPOUND EYES. IV. FRONT
OF HEAD OF WASP, SHOWING THREE SIMPLE AND TWO COMPOUND EYES. V. SIDE OF CATER-
PILLAR'S HEAD, WITH THREE EYES.

Ref. to Nos. in Figs. I., II.-1, surface lens; 1', layer of paint (iris); 2, cone, vitreous humour;
3, special optic nerve; 4, common pigment; 5, common retina; 6, secondary optic nerves;
7, main nerve.

The eye is exposed by a successive contraction of the circular muscles which are round the horn, beginning at the base and ending at the top; this action has the same effect on the parts of the tube, and finally upon the eye, as driving a coin into the end of an old-fashioned purse by the aid of a ring which slides on the

VOL I

than to receive impressions. Perhaps some process analogous to the development of the image in the dark room of the photographer is effected in this singularly

organ.

situated The creature whose large have just

eyes

now been mentioned has been introduced as & prominent character in Victor Hugo's "Toilers of the Sea," and the description is probably about as faithful as the description of brigands and other horrors described by novelists usually are.

Turning now to the articulate subkingdom, we find in it eyes of the most remarkable description. They are best explained by the diagram.

If we examine the head of a wasp or bee, we find on the top of the head, looking towards the sky, three eyes set in a triangle. These eyes are simple, and not unlike the eyes of other creatures; but besides these, on the side of the head, stretching almost from its crown to the jaws beneath, are two compound eyes, which, under the microscope, are seen to present innumerable six-sided spaces, which look like the ends of the cells of a honeycomb. On dissection, each of these sixsided faces is found to be the outer surface of a double convex lens, behind which is a layer of black paint, which is comparatively thick at the edges of the lens, but thin towards the centre, where a hole is left through its middle. This hole is the pupil. Behind the pigment is a cone of transparent matter, whose point is directed inwards, and embracing this point is the end of a nerve thread. The threads from each eyelet run inwards to a sheet of nervous matter common to the whole eye, and from this sheet other nerve cords, but much fewer in number than the first, run to the main thick optic nerve. The space between the nerve cords is filled up with black paint, so that each can only receive impressions from its end. An insect, therefore, one would think, receives thousands of distinct pictures; but whether it so harmonises them in its common

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gumas set by spare only one, as we are though we have

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200 Moyen A 12mere seem to be used for distant objects, w pinud over with red sealing-wax dissolved in so to blind them, the insect has no power of mt gut, but towers straight upward towards the sky. Fox compound eyes must be used, therefore, for near kata and me they stretch round the head and look every way, yaset wave the in sect much trouble in turning the head as it in and out the bells and tubes of flowers searching for honey and pollen. Lobsters and crabs, belonging to another order of the jointed ermale, have similar oyes, but they are set on a two-jointed stem, and the facets are squaro, and not six-sided.

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To's kind of eye, however, is by no means found in all animals of this sub kingdom. The whole tribo of spiders has only simple eyca; but there are usually eight of them set in two kows on the front part of the head.

It is singular to find also that caterpillars, though they exhibit beneath the skin of the head indications of the compound øye, which as butterflies they afterwards possess, have totally different temporary eyes, six on each side placed in a half ofrolo just above the jaws,

Home of the lower families of jointed animals have but one eyo, in the middle of their heads, and this of peculiar structure, intermediate between a simple and a compound eye. One of thono is honoo called cyclops,

Among the animals of lower grade than those of the soft slugliko and the jointed sub-kingdom, little has been made out about the organ of vision. In many of them spooks of colour with a norve running to them are found; but as we cannot ask these animals what their sensacions are, and their intelligence is of low an order that we can infer but little from their movements, ww can only conjecture them to be eyes,

As I wish to make everything clear as we proceed, I will enter here a little more into this matter.

A proposition is the enunciation or statement of a thought or a fact. Thus, fire burns; you are good; boys love play, are each a proposition. Of course the statement must be complete, or there is no proposition. What you say must make sense in itself, or there is no proposition, but only one word or more. Thus, if, instead of saying fire burns, you say merely fire, or burns, you do not utter a proposition, for you do not make a statement. If you affirm you are, I naturally ask, what? for you have left the sentence unfinished. So if you declare that boys love, the question arises, what? and only when you have added the word play, do you finish the sentence by making the sense complete.

Now, of the three propositions given above, the first is the shortest. It is indeed a specimen of the simplest proposition there is, or can be. Less than two words, then, cannot in

English form a proposition. But of what does this proposition consist? It consists of the noun fire, and the verb burns. Hence you learn that in every sentence there must be at least a noun or pronoun, and a verb. The noun, you see, is the subject of the proposition, for it is the agent or the cause of action. In grammar, we have also a designation for the verb; we say the verb burns is the predicate. By the predicate of a proposition, we mean that which is asserted or declared of the subject. What is here asserted? this, namely, that fire burns; burns, then, is the predicate.

In this case, the predicate is one word, a verb. Sometimes the predicate consists of two words. It may even comprise several words. In the instance given above, you are good, the predicate is, are good. Hence, the predicate consists of the verb soare, and the adjective good. The former predicate, burns, was a siple predicate; this predicate is a compound predicate. Now, this compound predicate has two parts; first, the verb are, which is called the copula, or link; and the adjective good, which is called the att ute, or that quality which is ascribed to the subject you. Thus explained, the sentence stands as follows:

Than, the star fish has spooks at the ends of its rays, and the rador may have noticed the beautiful blue knobs which appear rond the outside of the base of the arms of the common sea #momone when it has fije oponed. The great floating jelly-fish, ***, ** It is seen from a ship, reminds one of an animated; no bavila has spàs nund the eion where the whalebone Anim shoaid be All those and a thousand other structures

Subject.

You

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Predicate.

Attribute. good.

A be made in rofonoe to light; but probably the impres #5 Toy Pay MANiro, arm as faint and dall compared to the vivid Yon will easily see how this sentence may receive additions pocrv pental to the age of the higher animals, as the saxat which loh brings to the intant, whose ere is not yet. By adding it to arc, you make it a seget sentence. You to modify the sense. It is as it stands, an firmative sentence. à là d'aostai to garde us wandering har is, is crade when AMOM MENN Poslans which are prosental to the mind of a TN pane w mnvas leht, its marrello: De qm and its yet more marvellous interpret, e--the

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may also qualify the attribute good by prefixing an adverb, as,
very good. If you wish to make it intermipative, you have only
to convert the ella and the subject, and say, are y a good?
In the third of the instances given above, there is a rather
different kind of sentence, his four ping-

Ner, sovring to what I have just sail, boys is the subject, Tore the orpula or verò, and pin the object. The difference here is, that instead of an attribute in the predicate, you have an ook. The proposao, nemad logically, stands thus:

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But here we have a compound sentence, a complex or double proposition. As it stood before, it was a single sentence. A single sentence is the statement of one fact or one thought. Two facts are mentioned in the last state of the sentence. Those two facts are these, I mentioned some boys, and boys love play. And these two facts are so stated that the sense of the one is not complete without the sense of the other, for you do not say merely I mentioned some boys, and boys love play; but the boys whom I mentioned love play. You thus see that the one proposition is intimately connected with the other. Consequently, a compound sentence, such as I have now presented to you, is a sentence within a sentence. Of these two sentences, the one is the principal, the other the subordinate one. The subordinate sentence is that which is introduced by the relative pronoun whom; the principal sentence is that into which the subordinate sentence is introduced; as you see in this diagram:

Principal

The bad boys

Subordinate Sentence. whom I mentioned.

Revert now to the single sentence.

Subject.

The dog

and turn the sentence, thus :

Subject.

The man

Latin they do undergo a change; and that change is at the end of the adjective, as it is at the end of the noun. A change for another purpose takes place at the end of nouns and adjectives in Latin. By such changes gender or sex is denoted. In English, you know, we say, good bride, good bridegroom; that is, good is the same whether it qualify a feminine or a masculine noun. Not so in Latin. In Latin, good in the former instance would be bona; in the latter, bonus. So sponsus, bridegroom, becomes in the feminine, sponsa, bride.

KEY TO EXERCISES IN LESSONS IN LATIN.-III.
EXERCISE 5.-LATIN-ENGLISH.

1. Thou owest (oughtest). 2. He teaches. 3. He is exercised. 4. We flourish. 5. You rejoice. 6. They are bitten. 7. We move. 8. You move. 9. They move. 10. Thou fearest. 11. He fears. 12. He is frightened. 13. You are frightened. 14. I owe (that is, I ought) to obey. 15. If you obey you are praised. 16. If we are silent we are praised. 17. Thou art taught and art educated. 18. They are silent always love much play. and are praised. 19. I am bitten and am wounded. 20. If thou woundest thou art blamed. 21. They are held.

Predicate.

Copula. bit

Predicate.

Copula. bit

Sentence.

Object.

a man,

Object. a dog.

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Hence you learn that the subject and the object are, in Latin, marked by different terminations in the nouns and the adjectives.

Diversities of termination are used in Latin to mark number in nouns and adjectives. In English we say good boy and good boys, denoting the plural by adding s to a noun, but leaving the adjective the same in the plural as it is in the singular. In Latin, however, both adjective and noun undergo a change in passing from the singular into the plural, thus :

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Plural. boni pueri good boys,

where, observe, us has become i, and r has become ri. You thus see that there are two ways of forming the plural in Latin; first, by changing the termination, as us is changed into i; or by adding to the termination, as r becomes ri, by the addition of i. If, instead of operating on us, you operate on the stem bon, then the plural in both cases is formed by addition, and in both by the addition of i. Instead of i, sometimes es, and sometimes us is added to form the plural. But that which I now particularly wish you to mark is, that while in English adjectives undergo no change in standing before nouns in the plural, in the

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1. Thou deceivest. 2. He is deceived. 3. We are deceived. deceive and am blamed. 5. He yields. 6. Thou readest. 7. He writes. 8. He reads well. 9. Thou deceivest greatly. 10. If he is loved he rejoices. 11. We are pricked. 12. Thou conquerest. 13. We are conquered. 14. They are conquered. 15. He falls. 16. Thou slayest. 17. If thou slayest thou art blamed. 18. He reminds (advises) well. 19. Thou art badly educated. 20. We are greatly injured. 24. You defend. 25. They are defended. 26. I am loved. 21. We dance and rejoice. 22. He is injured. 23. You are

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1. Thou guardest. 2. He is supported. 3. He comes. sleepest thou? 5. He sleeps well. 6. He is instructed. prickest. 8. He slays. 9. Thou deceivest greatly. 10. He is heard. 11. If thou sleepest much thou art punished. 12. He finds. thou instructest well thou art praised. 14. He is bound. 15. Why art thou silent P 16. He is silent and is punished. 17. They are found. 18. Thou art clothed. 19. They are well clothed. 20. If you are clothed well you are delighted. 21. They are badly instructed. 22. If thou art conquered thou art bound.

EXERCISE 10.-ENGLISH-LATIN.

1. Cur occidis. 2. Custoditur. 3. Custodiunt. 4. Si custodimini vincimini. 5. Vituperat et punit. 6. Audit et eruditur. 7. Bene educamini. 8. Valde dormis. 9. Legunt. 10. Si saltatis delectamini. 11. Fulcitur. 12. Cur puniuntur? 13. Audiuntur. 14. Male vestior. 15. Feriuntur et monentur.

EXERCISE 11.-LATIN-ENGLISH.

5. They bite. 1. I yield. 2. Thou readest. 3. We move. 4. Thou art exercised. 8. Why dost thou read badly? 6. They flourish and rejoice. 7. He tries to read. 9. He sleeps badly. 10. Thou art much loved. 11. You are conquered. 12. They write well. 13. If you paint well you are praised. 14. We are defended. 15. We strike. 16. Why do you punish? 17. We are clothed. 18. We bind. 19. We are conquered. 20. We are bound. 21. You conquer. 22. Thou art guarded. 23. He is adorned. 24. They are praised.

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1. Cedunt. 2. Si ceditis vincimini. 3. Si vincimini vincimini. Fulcior. 5. Dormiunt. 6. Cur puniunt ? 7. Cur puniuntur ? 8. Male vestimini. 9. Vincis. 10. Vinceris. 11. Vincis. 12. Vincíris. 13. Pungunt. 14. Punguntur. 15. Cur moves?

EXERCISE 13.-LATIN-ENGLISH.

1. We are good. 2. He is good. 3. Thou art good. 4. I am not good. 5. He is blind. 6. He is not blind. 7. They are very learned. 8. You are safe. 9. You are not safe. 10. I am unlearned. 11. Yon

are unlearned. 12. He is not unlearned. 13. Thou art very learned. 14. Why art thou bad? 15. I am not bad. 16. We are good. 17. He is unlearned. 18. Why art thou unlearned ? 19. I am not unlearned. 20. We are safe. 21. Safe are we. 22. Thou art learned and safe. EXERCISE 14.-ENGLISH-LATIN.

1. Doctus sum. 2. Non sum doctus. 3. Doctus est. 4. Docti sunt. 5. Mali estis. 6. Non estis mali. 7. Bonus es. 8. Boni sunt. 9. Non sunt boni. 10. Cur boni non sunt? or, Cur non sunt boni? 11. Cæcus est. 12. Non est cæcus. 13. Cur est cæcus ? 14. Non es indoctus. 15. Cæcus es et non salvus, or, Cæcus et non salvus es. 16. Cæci sunt. 17. Boni et salvi estis. 18. Valde indoctus est.

AMERICA.

LESSONS IN GEOGRAPHY.—IV. ARABIAN NOTIONS-EUROPEAN TRAVELS-DISCOVERY OF FROM the time of Ptolemy down to the tenth century of the Christian era, no geographical work appeared, either to supply the place of his, or to add to the knowledge which it conveyed. The invasion of the Roman empire by the northern hordes, the general anarchy which followed, and the seclusion into which literature was driven, produced a retrogression of all the arts and sciences, and especially of geography. A proper judgment may be formed of the ignorance which prevailed in this science immediately anterior to the time of the crusades, by inspecting a map of the world published at that period. The sea, as in the age of Homer, is made to surround the world, which is divided into three parts, Europe, Asia, and Africa. Asia is as large as the other two parts; Africa is joined to Asia on the south, and the Indian Ocean is made an inland sea. On the east, there is a small place indicating the position of the garden of Eden, by the words Hic est paradisus. Europe and Asia are separated from Africa by a very long canal, which some believed to be the Nile, others the Hellespont, and others again the Indian Ocean. Africa is considered the country of fable and mystery; its northern part only is seen, the rest is unapproachable on account of the torrents of flame poured on it by the sun. After the discovery of the Canary Isles and Cape Bojador, geographers represented in one of these islands the figures of colossal statues brandishing formidable clubs to warn navigators that they must not go beyond this point.

A fantastic dream, filled with chimeras and ridiculous sights, hovered over the world during the middle ages. The cosmological theories then rife, were inferior to the happy notions which prevailed in pagan antiquity. Light, however, had begun to dawn. At the commencement of the eighth century, pious monks had retired into Ireland and the Faroe Isles. In A.D. 795 Christian missionaries had visited Iceland, which was considered as the ancient Thule of Pytheas. In A.D. 855 the Norwegians landed on this island; proceeding farther west, they reached Greenland, and enlarged the boundary of geographical knowledge. Certain writers have advanced the opinion that the problem of a communication between the Atlantic Ocean and the great ocean, now called the Pacific, was really current among the maritime people of that period. It is nevertheless an historical fact that America had been discovered by the Scandinavians at this remote period. Yet the discovery of Greenland detracts nothing from the glory of Columbus. The hardy adventurers of Norway were the first who penetrated into the midst of the mountains of ice which bristle round the confines of the polar countries. We are equally struck with wonder and admiration at their daring courage, in reading the history of the eighth, ninth, and tenth centuries, when we find that all the known seas were during this period covered with the vessels of the Scandinavians. The conquests of these pirates in Europe are well known. Their voyages in the icy regions are almost unknown to the general reader.

The expeditions we have now referred to were turned to some advantage by the geographers of the period, but all the light they were calculated to give was not rendered available. The learned writers of the tenth, eleventh, and twelfth centuries still believed the Frozen Ocean, the Baltic Sea, the White Sea, and the Caspian Sea to be united. They believed that all the northern regions formed only one island. Then the Amazons, those famon whose country antiquity had placed to the nor were now removed to the countries of Europe. Scandinavia became

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their birthplace and their residence. "The fiction of the Ama zons," says M. Humboldt, "has travelled over all the zones; it belongs to a complete circle, which proceeds from the reveries and ideas in which the poetic or religious imagination of all races of men, and of all periods, instinctively performs its evolutions."

The Arabians, by a series of brilliant conquests under the successors of one of the greatest impostors the world ever saw, had reached a state of comparative ease and power, and had devoted themselves during the dark ages of Christianity to the study of the exact sciences, in as far as they had escaped the ravages of one of their own princes, who destroyed the library of Alexandria, which contained the treasures of the remotest ages. Geography, in connection with astronomy, was one of the most interesting subjects of their investigation. But their cosmological system was scarcely less absurd than that of the ancients. They divided the world into seven climates, and each climate into a certain number of regions. Although some of the Arabs had made long voyages, and one of their geographers had actually explored Africa as far as the Niger, or Joliba, and the region in which is situated the famous Timbuctoo, still their knowledge of this continent was very incomplete. They always made the Indian Ocean an inland sea; and although they were familiar with the use of the astrolabe (an instrument similar to a quadrant) and the mariner's compass, they were afraid to navigate the open seas, a fact which contributed to their continued ignorance. One of the most learned Arabian geographers of the twelfth century, Edrisi by name, the same who constructed for Roger, king of Sicily, the famous silver planisphere which weighed 800 marcs (about 400 lb.), had the most singular ideas of the terrestrial globe. He fancied that all the people of the world lived in the northern regions; that the southern regions were desert on account of the sun's heat; that the latter were situated in its lower part; and that, conse. quently, all the waters were dried up, and that no living being could exist in those regions. He asserted that the ocean entirely enveloped the globe like a circular zone, so that only one part appeared like an egg partly immersed in water in a vessel. He placed Africa in the first climate, which commenced at the western sea, called the Sea of Darkness; and beyond this all existence became impossible. He speaks of the two islands called the Fortunate Islands (the Canaries), from which, as the first meridian, Ptolemy reckoned his longitudes. Such was the state of geographical knowledge among the most learned of the Arabians.

The call to arms against the infidels, in the various crusades or holy wars which extended over the greater part of the thirteenth century, drew the attention of Europe to the East. This was the epoch of the travels of Carpini, of Rubruquis, and of Ascelin in Tartary. These adventurers, after they had travelled along the shores of the Caspian Sea to its northern extremity, reached Karakorum, the capital of the empire of Cathay (China), situate on the Orchou, a tributary of the Selinga. The narratives of Ascelin and Carpini reveal the existence of numerous tribes in a part of the world hitherto believed by geographers to be occupied by the ocean. "Eous," says a modern historian, "that fabulous sea of antiquity, the bed of Aurora, disappeared for ever, and hordes of savages, as well as nations of powerful and warlike people, emerged at once from its imaginary waters."

The celebrated travels of Marco Polo took place towards the end of the thirteenth century, from 1271 to 1297. They made known the centre and the eastern extremity of Asia, Japan, part of the islands of the Eastern Archipelago, and of the con tinent of Africa, and the large island of Madagascar. Among the descriptions of the illustrious Venetian, that of China was the most curious and important; it was a complete disclosure of that empire, which had been hitherto almost an enigma to Europe. After long and continued suspicions of exaggeration in his narrative, the assertions of Marco Polo have been, after careful examination, acknowledged to be correct and agreeable to fact. It is with justice, therefore, that this traveller has been styled the founder of the modern geography of Asia. A very considerable time elapsed before any addition was made to the brilliant discoveries of the Venetian; but the testimony of other travellers was not long wanting to confirm his original statements. Oderic, of Portenau, visited India and China from 1320 to 1330; Schiltberger, of Munich, accompanied Tamerlane

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