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LESSONS IN CHEMISTRY.-I.
| pieces of the metal from the rest; that is, I have applied a force INTRODUCTION-ATTRACTION OF GRAVITY-FORCE OF
which has overcome the power of cohesion, and therefore certain
particles have been wrenched from their neighbours. Now I COHESION-FORCE OF AFFINITY.
may collect the "filings," and submit them to the greatest The object of Chemistry is to ascertain the nature and proper pressure I can exert, but I cannot bring them back into their ties of the substances of which our world is composed. Of late solid state; no pressure which we at present possess seems to years, the curiosity of the chemist has penetrated beyond the be capable of bringing the particles sufficiently near to each tangible, and by the aid of the “spectrum analysis," of which in other to allow the force of cohesion to come into play. due time we hope to treat, a new chapter has been added to Bat although particles of bodies are bound thus closely the science on “Stellar Chemistry," which gives some insight together, yet in no body do they seem to be in actual contact, into the composition of the great centre of our solar system, for all solids are porous. Two hundred years ago this was and even of the distant stars. In pursuing his investigations, proved in the case of gold by the “Florentine Experiment;" and the chemist submits the bodies under his consideration to expe- if gold, which is almost the densest of metals, can be shown to riment: he operates upon them with various forces-heat, be porous, we may well believe it of the rest. The “ Florentine electricity, etc.-brings them within the action of re-agents, Experiment” is so celebrated that it demands recital. The Fatches their behaviour in all circumstances, and never predicts question was raised concerning the compressibility of water, and a result, but determines all by experiment; hence chemistry is it was determined to try the experiment in the following purely an experimental science,
manner :-A hollow sphere of gold was filled with that liquid; Seeing that we have to do with bodies, let us in this lesson and seeing that a sphere is that solid which possesses the maxi. dwell upon the forces which act upon “substance," and which mum capacity, any alteration in its shape would therefore lessen oppose or assist the chemist in his research.
the quantity of water it could contain. The gold globe was What is body? “That which has weight” is, perhaps, the accordingly slightly flattened, and the water oozed through the least objectionable definition. Gases, although they are so gold, appearing as dew on the outside. The Florentines, there. intangible, and unlike anything solid, are yet bodies; they have fore, declared that water was not compressible-a conclusion weight. The weight of air on every square inch is 14:67 lbs., and they had no right to draw unless they could have collected the when set in motion it becomes wind, which sways the trees, carries dew, and found that it exactly filled the space by which the before it clouds of dust, or in the hurricane devastates a country, pressure had diminished the capacity of the hollow sphere. which it could not do if the air were imponderable. There Water has been proved to be slightly compressible, and the are, however, existences present in the world which have no only use of the Florentine Experiment is to assert that gold is weight. Caloric, which produces the phenomenon of heat; elec porous. tricity; ether, whose waves cause the sensation of light, and the This truth, that the particles of bodies, in spite of the great different forces of attraction—these, not being “bodies," do not force of cohesion, are not in actual contact, may be inferred strictly come within the range of Chemistry: they rather belong from the fact, that all bodies contract when cooled, which they to the domain of the physicist; but it will be necessary to speak could not do if their particles were already in contact. Thus it of them, seeing they take such a prominent part in the decom- would appear that the particles or molecules of bodies are under position and combination of bodies.
two forces-one attracting, the other repelling them; and that The forces of attraction, by which the particles of bodies are the state of the substance, whether it be solid, liquid, or gaseous, bound together, are the attraction of gravity, the attraction of will depend upon the ratio which these two forces bear to each cohesion, the attraction of adhesion, and the force of affinity. other. In the solid state the molecular attraction, or cohesion,
The attraction of gravity is that mysterious power by which is by far the stronger. In the liquid condition the repelling the Creator has linked to each other the suns and worlds which power almost balances the attractive; in a gas it entirely superoccupy space; for he has ordained that all matter should exert sedes it, and the atoms are solely under the influence of “molean attractive force on all bodies in its neighbourhood. This cular repulsion.” When the temperature of a body is raised, force varies with the mass of the bodies and their distances this molecular repulsion is always increased, each atom being from each other.' If a stone be dropped over the edge of a perpen. repelled from its neighbour. The body expands, and at last the dicular cliff into the sea beneath, it will strike the rock before it cohesion is so nearly overcome that the solid becomes a liquid. reaches the water, because the cliff attracts the stone and draws | If the temperature still increase, the atoms are still further it towards it. If, however, the stone be carried away from the repelled, until they cease to have any attraction for each other, cliff, the attractive force decreases. The power which made the and the body becomes a gas. The molecular repulsion is so stone fall was " gravity," that is, the attraction which the earth closely allied to caloric, the one is so intimately dependent upon has for the stone; the force of that attraction we call its the other, that they have been thought to be the same thing. "weight.” That this force decreases with the distance the That the physical condition of a body entirely depends upon stone is taken above the earth, is proved by the fact that the heat may be shown in almost all bodies. Ice becomes, when stone would weigh less on the top of a high mountain than in heated, water-then steam. Put a small piece of zinc in the the valley beneath. Of course, to test this fact a spring balance flame of a blow-pipe : it first becomes red-hot, then melts, and must be used.
finally goes away in vapour, which burns with a bright white The force of cohesion, which has more claim upon our attention, flame, into the oxide of zinc. There is the strongest evidence differs from “ gravity" chiefly in this, that “gravity" acts upon that all bodies are capable of assuming these three states. bodies at a distance, whereas the force of cohesion only begins Solids may be gases under certain circumstances; and gases, by to operate when the particles of matter are brought into the sufficiently reducing their temperatures, may become, first liquids, closest contact.
then solids. In future lessons we shall find many examples of It is due to this force that bodies possess solidity, and it this interesting fact. would seem that in liquids "cohesion” was very weak, and had no Adhesion is a force which binds two bodies together by means existence at all in gases.
of some adhesive substance, such as gum, glue, etc. If I file a piece of iron, the teeth of the file separate small! The force of affinity. This is eminently a chemical force. VOL. II.
But before it can be understood, we must explain what is we can easily separate them again by throwing the powder into I T t an otom. Suppose we had the power of dividing a water ; the heavier, copper, will sink to the bottom first. But if
Fruit of iron an unlimited number of times, it is believed that we apply heat the whole will begin to glow, and a black substance ui last a particle would be reached, which would defy all power will be the result, in which the microscope is unable to discern ertner to divide it, or change it in any way. This would be an any copper, for another substance has been formed—the sulcim (unable to be divided). These ultimate and unchange- phide of copper--which is as different in its properties from able particles were formed at the creation, and they will exist sulphur and copper as they are from sand. The glow which unaltered until the Creator wills otherwise. We have no power passed over the mixture when heat was applied, is an example to change or destroy them.
of a universal law-namely, that whenever chemical combination The most minuto particle, which even the microscope can only takes place heat is always developed. just discern, may contain millions of these atoms, so that they In summing up this chapter, it appears that the three forces, are far beyond the reach of the recognition of our senses.
gravity, cohesion, and affinity, act thus :A molecule (a little mass) will bear a definito meaning in these Gravity attracts masses of matter at any distance. pages-namely, the least particle which is capable of existing by Cohesion attracts particles generally of the same kind, and itself. In fact, it is the ultimate particle of a compound body. comes into play only at very limited distances. Thus, we shall find that water is composed of two atoms of Affinity attracts atoms of different substances, producing new hydrogen and one atom of oxygen; hence the molecule of water bodies, and its action is infinitely more close and intimate than would be a group of these three atoms.
either of the two other forces. Of the extreme minuteness of these atoms we may gain some idea, by the extent to which we can subdivide matter by mochanical means. If a bar of silver be gilded and then
LESSONS IN GREEK.-I. drawn out into a wire, the thread may be so fine that the gold covering one foot weighs less than all of a grain; an inch
INTRODUCTION. of this wire will contain of a grain ; this may be divided THE Greek Language is the language of the Hellenes, or ancient into 100 parts, each visible to the eye, and each being covered Greeks. The ancient Greeks were early divided into three great by own of a grain of gold. Under a microscope magnifying races, each of which originally used a different dialect both in 500 times, cach of these pieces may be subdivided by the eye poetry and in prose. The Ionic dialect was spoken by the Ionic into 500 parts, the gold retaining its original appearance, and race in Asia Minor and in Attica, and latterly passed into the showing no signs of dividing into its separate atoms; and yet Attic dialect. The Æolic dialect was spoken by the Æolians in the particle visible to the eye, that which covers the upper part parts of Asia Minor, Boeotia, and Thessaly. The Doric dialect of the wiro, is wowwo of a grain,
was spoken by the Dorians, chiefly in Northern Greece, in the One hundred cubic inches of a solution of common salt will Peloponnesus, as well as in Crete, Sicily, and Magna Græcia by be rendered milky by adding to it a cube of silver, each side the Dorian colonists. The Greek language and the Latin lanof which menkurek i of an inch, dissolved in nitric acid. The guage form what are termed the classical languages. By the atoms of silver have found their way into every particle of term classical languages we designate those languages in which water, and there with the salt formed the white chloride of are written the works which, in modern times, learned men silver, which rendered the solution milky; that is, the small have agreed to regard as classical ; that is, works that stand cube of metal has divided itself into at least 100 billion parts, in the first or highest class of the productions of the human a number which the seconds' pendulum of a clock would beat in mind. The Greek language is a branch of the great family of 31,688 years! and even yet we are not sure that we have ap- languages which, under the name of Indo-Germanic, is DOW proached the measure of an atom of silver--we have only known to have extended from Scandinavia to the Indus, om. reached the limit of our own powers of subdivision.
bracing, as its two principal components, the Sanscrit, or ancient Afinity is that force, in virtue of which two or more of these language of the Brahmins, on the East; and on the West, the atoms combine to form a molecule of a compound body. This Teutonic, including the German, the Dutch, and the English. It body exhibits properties very different from those possessed by is thus seen that the Greek is allied to our own tongue. It is the combining atoms, and is said to be a chemical compound. allied to the English in regard to structure. What is more
We say, then, that chemical composition takes place when two obvious to the beginner is, that the Greek is allied to the English or more bodies so unite as to form a compound body, which in words: thus, for example, our word one is the Greek év (hen); differs in its properties from its components. For example, if two is the Greek dvo (du'-o); three is the Greek Tpels (trice). The we take a piece of chalk and pat it in a glass of water, in due English pronoun 1 is only an abbreviated form of the Greek equ time it will become softened, and if we stir the water the chalk '(egro), which signifies I. Our verb know is the Greek you (10 will render it milky, but no change has taken place, for if we let in the verb prywkw, to know; the sound being identical, and it stand the chalk will sink to the bottom, or if we evaporate the variation existing only in the letters. Many instances of the water we shall reover the chalk unaltered. But had we identity between words in English and Greek will appear in the added a little nitric acid to the water, bubbles of gas would have course of these instructions. At present, it is sufficient to state riven to the surface, acl the water would have become clear. the general fact. Here a che nich has taken place. The chalk vis com- With the Latin the Greek is connected more intimately than
mell of it and a call carbonic acid, held together by with the English. So much in common have the two, both m ** 2 * *);" kat tte Ditric arid had a stronger affinity for the words and in the inflection of words, that a knowledge of the one
E21 armir Bid posued, therefore it display the affords great assistance in the study of the other. In general, ** W
a rmin bilbles, and with the lime formed the indeed, a thorongh acquaintance with any one language conduces ** z-trate of 1.2m which is soluble in water, hence the water to the attainment of others. But here the relationship is so close became cear; and if we now evaporate, we shall find no longer that the aid is special. That aid may extend its operation to chalk, but a transparent crystallised substance-the "nitrate of the whole class of languages known as the Indo-Germanec; lime" -very different from either the lime or the nitric acid, of that those who become familiar with Greek thereby acquire which it is composed. Here, then, chemical combination has ' facilities for studying not only Latin, but also Sanscrit, German, taken place.
and English, The observing reader will have gathered from this experiment The Greek is a very old language. Homer's works go back that bodies differ in their affinities; some have strong inclination to nearly a thousand years before the birth of Christ, and at the to combine with each other, while others exhibit little or no time when they were produced the Greek language was already desire to do so. It is this fact which enables us to carry on' a settled tongue; and it must have existed and have been spoken chemical investigations. The difference between a mechanical by persons of no small culture for centuries. Under the name mixture and a chemical combination is so important, that we of the Romaic, the Greek language a good deal modified select another illustration.
still spoken and written, being the vernacular or native tougue Tf we take some flowers of sulphur and copper filings, and mix of the modern Greeks, who are the descendants of the ancient
ether, we shall produce a greenish powder, looking at Greeks, and dwell on the same soil.
Ugnifying glass, the particles of copper will be seen The Greek language, as developed and perfected in its Am
in the world. No modern tongue, except the German, can example, the word bronchitis. Now I have never studied mediendare a comparison with the Greek. The Greek language cine, yet, from my knowledge of Greek, I know that bronchitis is owes its superiority to the richness of its vocabulary, the a disease whose seat is in the Bporxia, (bron'-ki-a), that is, the variety of its inflections, its power of forming compounds, extremity of the wind-pipe. its expressiveness, its adaptability, and its harmony. It was In proceeding to the study of Greek, you are stopped at the said of old that if the gods were to descend to earth, they would very threshold, for the characters of the letters are not the speak the language of Plato, the famous Greek philosopher. same as those of your native tongue. The diversity, however, The spirit of the saying is borne out by fact. The Greek is a is in appearance more than in reality. In fact, the English wonderful and beautiful instrument of human thought.
alphabet was derived from the Latin, and the Latin alphabet Bat the study of Greek is worthy of attention, if only as a was derived from the Greek. It may be added, that the means of self-discipline. Self-discipline is the true end of edu- Greek letters can be traced back to the Phænician. Thus we cation. Nothing better can be given to any mortal than a well- learn from this statement that the English and the Phænician cultivated mind. The man whose facalties are in their highest alphabets are related to each other. In the descent of the state of development, and their greatest degree of activity and letters, however, from age to age, and in their passage from one productiveness, stands at the summit of humanity, and now en. people to another, they underwent considerable changes; so joys what he has reached, namely, the perfection of his earthly that, at least in some instances, it is only a practical eye that, being.
by supplying the intermediate forms, can discover the idenPre-eminently fitted is the study of the Greek to educate our 'tity. Yet scarcely is the difference in any case much greater mental powers. All linguistical studies are useful for that pur- | than exists between what we call Old English or Black Letter, pose. Looking at their effects in their several bearings, I am and the letters now employed in ordinary printing; or those free to declare that the study of languages is of all studies tale : you see when you compare a written with a printed composition. most useful. But the Greek has the special recommendation of I have made these remarks in order not only to state an being more subject to rule than other languages. The Greek, important fact, but to induce you to compare the forms of the too, deals with wider reaches of intellect and subtler distinc- Greek letters with the corresponding English forms. By so tions of thought than most other tongues can comprise or define. doing you will be much aided in becoming familiar with the
But there is a recommendation of the study of Greek which Greek letters. throws all others into the shade, for in Greek are the Scriptures
THE GREEK ALPHABET. of the New Testament written. Strange is it that, in a Chris.
English tian country, the records of salvation should be so little read in
Small Equivalents Name in
Name in their originals. What a privilege is the power to do so! How Capitals. Letters. in Sound. English,
Greek. much better are the teachings of the Apostle to the Gentiles un
Alpa. derstood, when the student applies his mind to the very words
Bnta. which fell from his lips or flowed from his pen! How much
g (hard) Gamma
Γαμμα. more easily, and how much more thoroughly, do we enter into
Δελτα. the spirit, and feel at once the beauty and the power of the
e (short) Epsilon
Εψιλον. lessons of the Divine Master, when we have thrown aside the
Zyra. veil of a translation, and reverently with our own eyes look upon his sacred presence!
Onta. In connection with the study of theology, we may observe
Iwta. that the word "theology," and almost all onr ecclesiastical and
Kaa. theological terms, are derived from the Greek. The English
Λαμβδα. Words bishop, baptism, atheist, liturgy, diocese, cathedral, with
Mu a host of others, are all drawn from the Greek. •
Nu While, however, the Greek language commends itself very
EL. specially to the attention of all who seek an acquaintance with
o (short) Omicron Ouikpoy. Divine truth, and offers its aid for the general culture and im.
Il.. provement of human intelligence, it is not without a claim
Rho which, though more humble, may with some persons be more
Sigma valid. That claim it lays before all who study or propose
Tav. to study the sciences. Though some of the sciences existed
Tyidov. not, even in rudiments, during the classical days of Aristotle,
Phi and though other sciences have been carried far beyond the
Chi (like ki) X.. boundaries where they were left by Euclid and by Galen, yet in
Y.. general the language of science is Greek ; for such is the readi
Sueya. ness with which the Greek lends itself to combination, that the moment a new science is elaborated-nay, the moment a new Of these five columns the first gives the Greek letters in capifact iş ascertained, or a new elementary substance is discovered tals; the second gives the same letters in small forms; the third -that moment some form or forms of words are produced from gives the corresponding English letters, that is, the forms in Greek elements, which exactly set forth the novelty. Hence English which have sounds similar to the several Greek letters; these scientific names are so many definitions, and being defini- the fourth gives the Greek name of the letters; and the fifth tions they describe the objects which they are used to designate; / gives the same name in Greek characters. The names, as they they, I say, describe those objects to such students as are fami- appear in the last column, are the designations which you are biur with Greek, Take photography as an instance. This word to assign to the Greek letters; that is, you are to call a not a, is made up of two Greek words, ows (phose), light, and ypaon but alpha; B not b, but beta, and so on. (graph'-phee), a painting, and so means light-painting ; that is, a Before you can advance another step, you must make yourself painting made by the solar rays. If the student will take the thoroughly familiar with these characters-with their names and trouble of turning to the Greek stems as set forth in the lessons their values or sounds. In general, you may follow your ordion the English language pitblished in the POPULAR EDUCATOR, nary English methods of pronunciation ; one or two exceptions he will find many illustrations of the fact that, in English, Greek will be pointed out immediately. Your present business is to is the language of science.
acquire a facility of transferring the Greek characters into correAs the language of science, Greek is of special service to sponding English characters, and to read the former in the all men of science; in particular is it of great service to sounds of the latter. In the requisite application I advise you medical men. A vast number of the words with which they to employ a slate and pencil. Write the alphabet several times have to do in their studies are of Greek origin. Those words, merely in Greek. Then compare together such Greek characters to persons ignorant of the Greek tongue, are so many unknown as resemble each other, and carefully mark wherein they differ. terms, the meaning of which has to be learnt as a mere matter | Having become familiar with the mere forms, associate with of routine ; but to the proficient in Greek they define themselves, each its own name. Then study the sounds, that is, pronounce and so describe the objects which they represent. Take, as an each Greek letter in the corresponding English sound. These
ose Too East go over again and again, until you are per. In printed Greek books you will see several marks of accen.
221 the whole, and can from memory write down tuation over the letters. These I shall for the most part omit, e EU Tb all its forts and parts, as here given. I as the study of them would embarrass the beginner, and as a Der T
a ke great pains in this matter, and not to pass knowledge of them is not necessary to either the understanding LE IN Tu hare thoroughly accomplished this task. Your or the pronunciation of Greek. When you have mastered the Itin
e ns recommendation will save you a world of trouble. real and inevitable difficulties of the language, you will readily Es the sourcensement, you will do well to confine yourself to acquire an acquaintance with these now almost useless signs. que son actm; having acquired them, you will readily za y ef fumbiar with the capitals.
Is the sea waaracters, you will at once discover similarities LESSONS IN GEOGRAPHY.-XIV. Cosmo tie Gresk and the English forms. The Greek a and
ASTRONOMICAL PRINCIPLES OF GEOGRAPHY, x Den 4 zre otrrisasly the same. The English e and the SUPPOSE that you were elevated in the heavens, or in the vast sarre r ak are very nearly alike. The two b's differ little. | space in which roll all the stars, to a point millions of miles above Tie , 'er Sentical, so are the two o's (o short); and the the sun; and that you were furnished with a telescopic eye so
ela luis pothing but two short o's (oo) put together. I powerful, that from that point you could observe the magni. 1x W... notice, in the Greek, two forms of the small letter s. tudes, motions, and distances of all the bodies in the Solar T utoforma are a and s. Of these, the first occurs at the System—that is, the bodies or planets which revolve round the
ning and in the body of a word; the second stands at sun in consequence of the laws of attraction and tangential this end te word. This form of the sigma, namely, s, may also impulse-you would perceive among them a highly-favoured be found in the middle of compound words, when the first of the planet called the Earth, accompanied by a satellite (an attend. wrath which the compound is formed ends in 8 : for example : ant) in its course, called the Moon. (n14.no, Myma Sigma at the end. Sigma in Compounds.
This earth and her satellite, like all the other planets and δρασμος Bgvinu
their satellites which you would behold in this bird's-eye view, δυσγενης
receive both their light and their heat from the sun; the in
fluences of light and heat being invariably distributed to all denomos
the planets in the same ratio as the power of attraction which Gamma, y, has tho sound of n before y, k, x, si thus, keeps them revolving in their orbits (tracks or paths); that is, fwrrnin pronounced gan'.ghoos; OVYKOTY is pronounced sune'. | in the inverse ratio of the squares of their distances; or, to ke 2, Kerxplos, kasn'-kri-ox; and napvy, lar-unx.
express it more clearly, the power of the attraction, the light Chh, x, lisan a guttural wound, and so differs from kappa, K. and heat of the sun on one planet, is to that on another planet, '1', urxiu never pronounced like our ch in church, but always as the square of the distance of the latter is to the square of in a way resembling our k in kita, kitchen, kick.
the distance of the former. Wer voweli, e in beta, in epsilon, oto., this mark · will be In your elevated position you would next perceive that the erbrieved, 16 in need to donoto a long vowel. The force of it planets, in their various revolutions, would at some times be yeni inay vive by throwing the strons of the voice on the vowel nearer to the sun than at other times; and that if the orbit of in myllable over which it is plnood. Thus omicron is to be pro- each were traced by a white line in space, it would appear to your www ma' krom. The opposite of is ", as in oméga; the eye, if rightly placed, to have the form of an oval nearly, being mache denoton n short syllable; nccordingly, omega is pronounced in fact, what is called in mathematics, an ellipse. Lun, a' mal, with the strons on the 0. A vowel of doubtful In order that you may understand the nature of this curve, rre Tamil is marked thumm X. When two vowels come together, shall explain it by means of a diagram. Thus, in Fig. 1, if you the former le grenerally short, as Ilov, -la-un, Diphthongs, how
fix two pins on a board, at the points F and
см AYT, are long that is on them you must throw the stress, as
F', and fasten a string F M F, of any conautovw, 'z at.no, Syllables are short or long, as they contain a
venient length, but greater than the disshort or long vowel, Syllables containing a diphthong are long.
tance between the two points, by its extreYou may ascertain whether you have mastered the letters, by F0F mities, at these points; and if you take a protining yourself in the following
crayon or chalk pencil, and press it on the
string horizontally at m, so as to keep it EXERCISE FOR ProxCSCIATION.
always tense (i.e. stretched), and parallel to N.B. - Every vowel in Greek, w
Fig. 1. hat at the end of a word or
the board, moving the pencil round and wwt, in pronounced as a separate sgiate.
round at the same time, from one side to the other, you will Ra, ke, kn, KI, KO, KU, KW.
describe the curve A C B D, which is called an ellipse. It is re, 70, m, yw, ga, y. X», xa.
evident that the limits of the form of this curve are the circle Ta, T6, TO. Ae, on. On, Cl, Bea, Onta. Ni, Tw, tas. Balla. and the straight line. If the two points F and F' are bronght close pi, pepw. Za, cov, oiyn. Purn, quy. Matep, uelos. Yo together, the curve will be a circle ; if they be separated as mnch l'aona. Enta, Entew, C7790S; Eavtos; NUKTES ; Xowy.
as the string will allow, the curve will become a straight line. The Anetaropos, Aulus. aanv, keavos. putos. Vavuus,
two points F and F are called the foci (the plural of the Latin VoMMetixos. Blas. In, ravkos, roprn. Xapites, Xdpılaos.
word focus) of the curve; the straight line A B drawn through
them, and terminated both ways by the curve, is called the wkeus, kiw, puyes. "Topa, "Travis, Twios. Aloy,
major aris; and the straight line c d drawn at right angles to Alvisos, ALOskovpor. Epis. Zakuvos, Zeutis. Hiektpa, Hxw, this axis from its middle point o, and terminated both ways by Hws. Kijapou. Avola, Nurias, Aokpus, Sakedaiwy. Ninn. | the curve, is called its minor axis. If a straight line be drawn Muws. O vunOS. Dataia, MittăKOS. Larawis, Laras, Ekvola.
from F to c, it will be equal to the straight line A o, or half the TATOES. 'Podos, 'Pwun, 'Pryloy. Eavdos.
major axis. The point o is called the centre of the ellipse, and
the ratio of Foto A —that is, of the distance between the You will find in the ensuing lessons these three marks or centre and the focus to half the major axis—is called the eccen. accents, namely,' above the letter (or to the left of it in capitals), tricity of the ellipse. The distance from the focus F to any point as in iva ; 1 under the letter, as in won; and “above the letter, m in the curve is called the radius vector of the ellipse ; it is as in ous. The first is called the spiritus asper, or rough breathing, least at A, and greatest at B. With these explanations, while being equivalent to our aspirated h; pronounce, then, as with an you are supposed to be looking at the orbit of a planet from h syllables before which this aspirate is placed, as 'Ains, Hades. your elevated position in space, you will now be able to comThe second mark is called iota subscript i underuritten), so prehend the fundamental principles of Astronomy,-namely, tormed because the letter , instead of appearing at the end, as Kepler's Laws. in oyw, is written or placed under the w as in Loyu : this The eminent German astronomer just mentioned, who flou. paul is commonly disregarded in pronunciation. The third is rished at the close of the sixteenth century and the beginning of
circumflex, being made up of the acute accent' and the seventeenth, discovered by laborious observations and calcu-
1. That the planets all revolve in elliptic orbits, situated in
planes passing through the centre of the sun; the sun itself hangeth the earth upon nothing" (Job xxvi. 7). This passage being placed in one of the foci of the ellipse.
is singularly true in regard to the first sentence as well as to the 2. That the radius vector, or straight line drawn from the second, for the axis of the earth is inclined to the plane of its centre of the sun to the centre of the planet, passes over equal orbit, at an angle of 66 degrees 32 minutes, that is, rather areas in equal times in every part of the orbit; that is, whether more than two-thirds of a right angle; so that literally and truly the planet be in its aphelion, or farthest from the sun, in its “the north is stretched over the empty place,” and not over the perihelion, or nearest to the sun, or at its mean distance from body of the earth itself, in either of its motions, whether axial the sun.
or orbitual. This inclination is preserved during the whole of its 3. That the squares of the periodic times of the planets—that motion in its orbit, and is the cause of the variation of the is, of the times of a complete revolution in their orbits-are pro- seasons; the preservation of the inclination of this axis has been portional to the cubes of their mean distances from the sun ; in not inaptly called the parallelism of the earth's axis. other words, that the square of the periodic time of one planet is! Before explaining the effect of this parallelism and inclination to the square of the periodic time of another planet, as the cube of the earth's axis in producing the seasons, it will be proper to of the mean distance of the former from the sun is to the cube of explain what is meant by tangential impulse. In Fig. 2, let AC B the mean distance of the latter from it.
represent the orbit of the earth, which is nearly Into the full explanation of these laws we cannot enter until circular; let D represent the place of the sun, we treat of astronomy; in the meantime it is necessary to give and a the place of the earth at the moment some explanation of the law which we have marked first, though when it began its revolution in its orbit. At B it is generally accounted the second, in order to clear up some this moment the force of the sun's attraction points connected with phenomena relating to the earth, and the would begin to act on the earth in the direction circles drawn on the globe, which is the only true representation A D, and had this alone been allowed to ope
Fig. 2. of the earth's surface. Supposing, then, the ellipse in Fig. 1 to rate, would have drawn it rapidly towards the represent the earth's annual orbit round the sun, and the focus sun in a straight line, until it had come finally in contact with o the place of the sun's centre; then the point A will represent the sun itself; but at the same moment an original impulse the position of the earth's centre at mid-winter, when it is was, or is supposed to have been given to the earth in the direcnearest the sun, or in its perihelion ; B will represent its posi- tion A E, which is that of a tangent, or straight line touching tion at mid-summer when it is farthest from the sun, or in its the circle at the point A ; so that the earth, which under the aphelion ; C will represent its position at the spring or vernal action of the former force would in a certain time have been equinor, when it is at its mean distance from the sun; and d its found at some point in A D, and under that of the latter force position at the harvest or autumnal equinox, when it is also at would, in the same time, have been found at the point F in A E, its mean distance from the sun.
would, by the combined action of both forces, be found near the We think we hear some of our readers exclaiming, notwith point c in the curvilinear orbit A C B. This original impulse, standing the elevated position in which we have supposed them the effect of which remains to this day unaltered by the action of to be placed, “What! Will you tell us that the sun is the cause attraction (seeing it has met with no resistance in empty space, of light and heat on the earth's surface, and yet you assert that and has been so balanced against the force of attraction as to the earth is nearer to the sun in winter than in summer? How retain the earth in its orbit), is called the tangential impulse or can this be ?” Paradoxical as this may seem, it is nevertheless force, which was imparted to it when it began its orbitual revotrue; and the reason we shall now give. As you are supposedlution. Young, in his “Night Thoughts," alluding to this tenet to be looking from a great distance, and to be able to discern of the Newtonian philosophy, asksall the motions of the planets, if you look narrowly at the earth, | “Who rounded in his palm those spacious orbs ? you will perceive that besides its orbitual or annual motion round Who bowled them flaming through the dark profound ?". the sun, it has a revolving or diurnal motion on its own axis.
Night IX. By aris here is meant that imaginary straight line passing Let us now consider the effect of the inclination of the earth's through the globe of the earth, on which its rotation is supposed axis to the plane of its orbit. In Fig. 1 we have supposed the to take place, and which is aptly represented in artificial globes sun to be at the focus F', while the earth is at the point A in by the strong wire passing from one side to the other, at the mid-winter. Now, at this point, you would see from your suppoints called the poles (that is, pivots), which are the extremities posed elevated position, that the northern half of the earth's of the axis.
axis is inclined to the major axis A B at an angle of 113 degrees This revolving motion on its own axis may be likened to the 28 minutes, the supplement of its angle of inclination to the spinning of a top, a motion which continues while the top is plane of the orbit; so that the North Pole, with the space on driven forward in any direction from one place to another. In the earth's surface around it to a considerable extent, is prefact, the analogy would be so far complete independently of the vented from receiving the rays of the sun, and consequently the causes of the motion, if the top, while it is spinning or revolving heat of those rays; while the South Pole, with the space around as it were on its own axis, were made to run regularly round in it to the same extent, is made to receive these rays and to enjoy an oval ring on the ground, under the lash of the whip. Thus, their heat. Hence, while it is winter in the northern or arctic the earth has two motions ; one on its own axis, performed once regions of the earth, it is summer in the southern or antarctic every twenty-four hours; and one in its orbit, performed once regions. While the earth is still in this position, the rays of every 365 days 6 hours. We have stated these periods in round the sun fall more obliquely upon the illuminated portions of the numbers, in order that they may be easily remembered; but northern hemisphere than they do upon the southern hemisphere, the exact period of the earth's daily revolution on its axis is and thus have less power to produce heat than if they fell per23 hours, 56 minutes, 4 seconds, and 9 hundredth parts of a pendicularly; just as a person sitting at the side of a fire-place second; and the exact period of the earth's annual revolution in with a good fire in it, feels less heat than a person who sits ita orbit is 365 days, 5 hours, 48 minutes, 49 seconds.
exactly in the front of it. The analogy of the motions of the top, however, to the mo- On the other hand, if you consider the earth from your tions of the earth, as thus described, is incomplete in respect of elevated position, when it is at the point B in mid-summer, the the position of their axes. The axis of the spinning top is in reverse of all this takes place. The northern half of the earth's general upright or perpendicnlar to the ground, which may be axis is inclined to the major axis (or line of apsides, as it is called the plane of its orbit, that is, of the oval ring in which it sometimes called ; that is, the line of junction of the two oppois supposed to move; but the axis of the earth in its daily motion site points A and B) at an angle of 66 degrees 32 minutes, which is not perpendicular to the plane of its orbit, or the ellipse in which is its angle of inclination to the plane of its orbit; so that the its annual motion is performed. In speaking of the plane of the North Pole, with the space on the earth's surface around it, earth's orbit our analogy fails, for there is nothing to represent above-mentioned, is made to receive the sun's rays, and consethe ground on which the motion of the spinning top takes place. quently their heat; while the South Pole, with the similar space The mere attraction of the sun, coupled with the effect of an origi- around it, is prevented from receiving those rays and enjoying nal impulse in the direction of a tangent to its orbit, is sufficient their heat. Hence, while it is summer in the northern or arctic to preserve the earth in its orbitual motion in empty space. Hence regions, it is winter in the southern or antarctic regions. While the sublimity and truth of the ancient passage in the book of the earth remains in this position, the rays of the sun fall more Job: “He stretcheth out the north over the empty place, and directly upon the northern hemisphere than they do upon the