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two coatings of a charged pane, we shall find that there is a i Various batteries of great size and power have thas been small amount of positive electricity on one side un-neutralised made at different times : for all ordinary purposes, however, by induction, and therefore free. The amount of this depends from four to nine jars, holding about five or six pints exch, will on the thickness of the glass.

be amply sufficient. If then we hold the finger to this side, taking care that the It is important to be able to estimate with some degree of other coating is insulated, we shall obtain a small spark from it. accuracy the intensity of the charge in a jar, and different As soon as this has passed, a similar amount of negative elec- means of attaining this end have been devised. The simplest tricity will be set free at the other side, and we can then draw a is by means of the quadrant electrometer A (Fig. 17), which is spark from that; in this way, we may continue drawing off the shown on one of the knobs of the battery. It consists of a charge, drop by drop, as it were, tiil it is all gone. If a Leyden thick brass rod, surmounted by a knob, and bearing on one side jar be placed on an insulating stand, we may discharge it in a a semi-circular graduated scale, usually made of bone or ivory. simila: way.

At the centre of this is suspended a thin wood rod, carrying & Two interesting experiments may be tried as illustrations of pith-ball on its further end. As the charge increases, this ball this-one with the pane, the other with the jar. Make two feet becomes more and more repelled, and the angle shown on the of gutta-percha, or some insulating material, so that the pane graduated arc increases, thereby giving a rough indication of may stand vertically. Having charged it, take a piece of wire the intensity of the charge. It must be remembered, however, and place a pith-ball on each end; then bend it almost round, that it is the intensity, and not the quantity, of the electricity 80 that when it rests on the upper edge of the pane the balls that is indicated. If the same amount of electricity be distrimay each be about an inch from the coating. The side on buted over jars or batteries having double the amount of coated which the excess exists will first attract the ball nearest to it, surface, the electrometer will only show one-half the intensity. and thus part with its excess of electricity; the other ball will still, the instrument is very useful, especially if it is made with then be attracted by

the rod somewhat the other side, and

smaller at the lower in this way the wire

Fig. 16.

end, so that it will will rock backwards

fit into the prime conand forwards till the

ductor or any other charge is dissipated.

piece of apparatus. This is called the

A better way of electric pendulum.

regulating the intenTo show the same thing with a Leyden Fig. 13.

sity of a shock is by

means of Lane's disjar, we must fix a

charging electromebell on the wire just

ter, which is reprebelow the ball, A

sented in Fig. 18. metal support,

It depends for its (Fig. 16), carrying a

action on the fact similar bell at the

Fig. 14.

that the distance same height, must

through which a be fixed on a stand,

charge will dart beand connected with

B

tween the balls, or, as the outer coating of

Fig. 15. D

it is called, the strikthe jar by a piece of

ing distance, is, for wire or tinfoil, B.

small charges, directThe upper part of

ly proportional to this support has a

the intensity of the bent wire fixed to it,

charge; that is, if from which a small

double the amount of ball is suspended

electricity be present by a thread of silk,

on the same surface If now the jar be

the striking distance charged, this ball

will be twice as great. will be alternately attracted and repelled by the bells, and | This distance varies, too, inversely as the amount of surface over thus will continue to ring them till the jar is discharged. which the charge is distributed. Thus, is one jar has twice the

If a jar be charged, and allowed to stand, the electricity in it surface of another, and the same amount of electricity be passed will be slowly dissipated, chiefly owing to the moisture in the into each, the striking distance of the first will be only one-half air, which acts as an imperfect conductor. This may be partly that of the second. These results will easily be understood if we obviated by coating the surface of the glass with shellac recollect that it is always intensity, and not quantity, that is varnish, and thus hindering the deposit of damp which usually shown; just as a thermometer shows the intensity and not tho forms on it. When, however, it is desired to preserve a charge quantity of heat, for there clearly is a larger quantity in a gallon for any length of time, the construction of the jar is slightly of water at the temperature of the body than in a cupful at the altered. The rod is not fixed to the cap, but passes through a boiling-point, and yet the thermometer shows a much higher glass tube fixed in it to the bottom; and when the jar is temperature if immersed in the latter. charged, it may be inverted, and the rod allowed to fall out. The electrometer consists of a metal tube, A, which fits on to When the charge is required, the rod must be carefully dropped the rod of a jar or battery, and carries at one side a curved rod in again. In doing this, however, it is advisable to take the pre- of glass, B. At the end of this is fixed a second tube, c, with a caution of placing it first upon some non-conducting substance. brass wire, terminated at one end in a ball, D, and at the other

Theoretically, there is no limit to the size of the jar that may in a ring, passing through it. When this is attached to a jar, the be employed. In practice, however, many inconveniences attach ball d may be brought within any desired distance of the knob, to the use of those which are very large. The tension of the and a chain is then attached to the

ring and connected with the electricity frequently becomes so great in them, that if there be outside. When the jar is sufficiently charged, the electricity a flaw or thin place in the glass it will pierce it; and if it be darts between the balls and discharges it. If it be desired to made thick, to guard against this danger, the induction is con- pass this shock through the body, or through any substance, the siderably weakened. The plan therefore adopted

is to employ a two sides of it are connected by brass chain or wire with the ring number of small jars,

and connect them together so as to form and onter coating respectively, and the shock passes as before. a battery. They are usually placed in a tray lined with metal, There are one or two other forms of discharging electrometer so as to connect their exterior

coatings, and a wire is brought which are sometimes used, and which depend on the attraction from this to one of the handles; the

knobs are also connected of the knob of the jar for a balanced metal rod. We need together by wires passing through them. (Fig. 17.)

not, however, stop to explain them here.

[graphic]

In all these the shock is given as soon as the necessary charge reference to Fig. 19, which represents the charge from a battery is communicated; this is sometimes rather a disadvantage, and being passed through a bird by means of this discharger. may be obviated by the use of a unit jar, which consists of a A piece of hard wood is taken, about twenty inches long small Leyden jar exposing about six inches of coated surface on and six inches wide, and in the middle of it there is fixed a each side. This is supported on an insulating stand, so that its small table, which can be adjusted at a convenient height by exterior is in contact with the knob of the jar to be charged. means of a thumb-screw. The top of this table is usually made A rod and ball are also connected with its outside coating, and of a disc of glass fixed on by shellac, or else it has a strip of brought within striking distance of its inner rod. The jar is ivory inlaid across it. At each end of the board is fixed a glass now brought to the conductor of the machine, and as it becomes rod, carrying at the top a revolving cap fitted with a compass filled a corresponding amount of electricity passes from its joint, so that the wire passing through it may be inclined at any exterior into the large jar. This continues till the unit jar is angle. The wires can also be slipped backwards or forwards, so fully charged, when it

that they may easily discharges itself, and

be brought into conthe same process is re

tact with any part of peated. In this way, D

the substance to be by counting the num.

operated upon. These ber of discharges of

wires are pointed at the small jar, we as

B В

the ends, and brass certain the number of

balls are fitted so as units of electricity con

to screw on over the tained in the large

points when required ; one.

but as brass balls are As we now clearly

rather expensive, lead understand the con

bullets may, in most. struction and action of Fig. 18.

cases, be substituted the Leyden jar and

for them, the main difbattery, we may notice

ference being in the some of the effects pro

Fig. 17.

appearance. One of duced by the electric

these instruments will shock. We will look

be found to be of great at the physiological

use to the student, and effects; and the first

he should therefore enwhich we observe is

deavour to procure, or, the peculiar sensation

better still, to make experienced when the

one; for a better know. charge is allowed to

ledge of the principles pass through the body.

of a science may usu. The sensation varies,

ally be obtained by of course, with the in

making apparatus than tensity of the shock,

by merely experiment. and is most strongly

ing with that already felt at the elbows and

Fig. 19.

made. As shown in across the breast. If

the figure, the object the shock of a large

through which the battery be taken dan.

charge is to be passed gerous results may

is placed on the table, ensue, especially if

and the knobs or points the electric fluid pass

of the wires brought through any vital por

into contact with oppotion; but with ordi

site sides of it. One nary charges no ill

wire is then connected effects whatever seem

with the outside of the to be produced ; in Fig. 20.

jar or battery, and the some cases it even ap

other connected with pears to be beneficial.

the knob by means of The effect of a very

the jointed dischargstrong charge is seen

ing rod, contact being when a person is struck

made with the wire of by lightning, death

the discharger first. being frequently

For this purpose, howcaused by it. The ac.

ever, it is necessary tion appears to be

that it should have an mainly on the nervous system. If we pass the shock through insulating handle, as the electricity always chooses the best small animals, such as birds or mice, they will be killed instan. conductors, and if there be any distance between the knobs, or taneously, and larger animals have been killed by shocks from if a badly conducting substance be interposed, the electricity may powerful batteries. There is, however, nothing further to be travel through the body of the operator to the ground instead learnt by these experiments, and it is therefore cruel and need of passing through the discharger less to repeat them.

The next class of effects we notice are the luminous. As The electric fluid, in its passage through living or dead bodies, already seen, whenever the spark traverses air a line of light also causes convulsive contractions of the muscles. Its physio- is seen ; when the two electricities from the opposite sides of logical effects will, however, be seen much more clearly when we a jar unite, the spark is much more luminous, being thicker come to treat of Voltaic Electricity, and we may therefore leave and denser, because of the passage of a much greater amount further notice of the matter till then

of the fluid. This spark is almost instantaneous, so that if a In studying the effects produced by electricity, we need some dark room be suddenly illuminated by it, a rapidly revolving method of conveniently holding an object while the shock is wheel in it will appear to be at rest. So instantaneous is it, passed through it, and this is afforded us by a very useful piece that a printed bill has been fixed on to a wheel, and made to of apparatus , known as Henley's

Universal Discharger. The revolve several hundred times per minute, and yet a distinct construction and mode of using this will be understood by photograph of it has been taken by means of the light from

[graphic]

y = 12.

and y.

the spark, the time required for its passage being so short that Transposing y in the 1st equation, gives a = 36 - y. the light has faded before the wheel has moved through an Transposing y in the 2nd equation,

x= 12+y. appreciable space.

Making these values of & equal, 12+y= 36 - y. if the points be made nearly to touch, and the thumb Transposing, etc., pressed down upon them, it will appear to be rendered semi Substituting the value of y,

x=12+12= 24. transparent, and the shook will not be felt. In a similar way Hence, 24 and 12 are the values required. the shock may be passed through eggs, oranges, etc., illumi. nating them. Some substances, too, remain luminous for some

EXERCISE 36. time after the charge has passed through them.

1. Given 2x + 3y = 28, and 3x + 2y = 27; to find the valaes of x and y. If we fix a ball to the plate of an air-pump, and connect it 2. Given 4x + y = 43, and 5x + 2y = 56; to find the values of x and y. with the exterior of a jar, and then place over it an open re 3. Given 4x-2y = 16, and 6x = 9y; to find the values of x and y. ceiver with a similar ball and rod passing air-tight through a

4. Given 41---2y = 20, and 4x + 2y = 100; to find the values of : plate at its upper end, we shall find that the spark will pass & much greater distance. In a long exhausted tube it will some- 5. Given 5x + 8 = 7y, and 5y + 32 = 72; to find the values of x and times appear to dart along like a ball of light.

EXAMPLE (1).-To find two numbers such that their sum Similarly, if we exhaust a large globe having a wire and ball shall be 24; and the greater shall be equal to five times the less. fixed tightly in each end, and connect the upper one B (Fig. 20) Here, let æ be the greater; and y the less. with the prime conductor, we shall find that, instead of the elec

Then, x+y= 24, tricity passing along in a series of thin sparks, it will spread out

And D=5y. and form a large faintly luminous space, having a violet tinge.

Whence, 5y +y=by = 24, On again gradually admitting the air by means of the stopcock,

And this space will grow smaller and smaller, till at last the narrow

Therefore, 20. Ans. 20 and 4. but bright sparks pass as before. Many similar experiments of great beauty may be performed by means of voltaic eleo

EXAMPLE (2).- Find two quantities whose sum is equal to h; tricity, and it is believed that th beautiful phenomena of and the difference of whose squares is equal to d. the aurora borealis, or northern lights, so frequently seen in Letæ and y be the two quantities. high latitudes, may be attributed to a similar cause.

And ** =a} per question.

From the first equation we have, by transposition, LESSONS IN ALGEBRA.-XXII.

a = h - Y,
SIMPLE EQUATIONS.

And, by squaring both sides, we have,
TWO UNKNOWN QUANTITIES.

aa = h - 2hy + ym. In our former Lessons on Simple Equations we gave the rules From the second equation, we have, by transposition, for solving those which contain only one unknown quantity;

202 = ga + d. and, with the exception of one or two, the whole Centenary of

Now, by equating the two values of **, we have, Problems were solved by means of these rules. We proceed now to show how to resolve equations which contain two un

yo+d=ha — 2hy + ya ; known quantities.

And, by transposition and cancelling, we have, Cases indeed frequently occur in which two unknown quan

2hy=ha - d; tities are necessarily introduced into the same calculation.

h* -d

Whence, y= EXAMPLE.-Suppose the following equations are given,

2h

h-dha +d (1.) «+y=14,

Therefore, z=h

21. (2.) -y=2.

EXAMPLE (3).-Given ax + by = h, and < +y=d; to find Hero, if y be transposed in each, they will become

the values of cand y. (1.) 2 = 14 - Y,

Here, from the first equation, we have, by transposition, (2.) a= 2 + y.

ax=h--by, Now, the first member of each of the equations is æ, and the second member of each is equal to 3. But according to the

And a=

h-by axiom that quantities which are respectively equal to another quantity, are equal to each other ; therefore we have

Again, from the second equation, we have, by transposition,

a=d—y, 2+y=14 - Y; whence y=6. Lastly, by substituting the value of y in the 1st equation, we

h- by Whence,

=dy; have a +6=14; and a = 8. Therefore, 8 and 6 are the values of a and y.

Or, hby = ad- ay, In solving the preceding problem, it will be observed that

And ay-by=ad - h. we first found the value of the unknown quantity æ in each

From this equation, by separating the left-hand member into equation ; and then, by making one of the expressions denoting factors, we have the value of x equal to the other, we formed a new equation,

(a--b)y=ad-h; which contained only the other unknown quantity y. This pro

adh cess is called extermination or elimination.

Whence, y = In the resolution of equations there are three methods of extermination, viz., by comparison, by substitution, and by

ad- --bd

Consequently, « = d addition and subtraction.

b -6 CASE I.—To exterminate one of the two unknown quantities The rule given above may be generally applied for the exterby comparison.

mination of unknown quantities. But there are cases in which RULE.--Find the value of one of the unknown quantities in other methods will be found more expeditious. cach of the equations, and form a new equation by making one of EXAMPLE (4).-Given x=hy, and ax + bx=ya; to find tho these values equal to the other. Find the value of the unknown values of æ and y. quantity in this equation, by the rules formerly given. Then As in the first of these equations « is equal to hy, we may in substitute this value of the one unknown quantity in either of the the second equation substitute this value of x for # itself. Tho other equations, and resolving it by the same rules, the other second equation will then become, ahy + bhy = ya. ven known quantity will be found.

The equality of the two sides is not affected by this alters EXAMPLE.-Given x +y = 36, and m y= 12; to find the tion, because we only change one quantity ~ for another which values of t and y.

is equal to it. By this means we obtain an equation which

viz,

2h

a

[ocr errors]

a

a

y = 4.

[ocr errors]

2+1

[ocr errors]

a

contains only one unknown quantity. Whenco, y=ah +bh, add them together if the signs are unlike; the result will be an and x = ah + bh'.

equation containing only one unknown quantity, which is to be This process is called extermination by substitution.

resolved as before. CASE II.-To exterminato an unknown quantity by sub It must be kept in mind that both members of an equation stitution.

are always to be increased or diminished alike, in order to preRule.— Find the value of one of the unknown quantities, in one serve their equality. of the equations, in terms of the other unknown; and then in the EXAMPLE (9).-Given 2x + 4y= 20, and 4e + 5y = 28; to other equation SUBSTITUTE this value for the former unknown find the values of æ and y. quantity. From this equation, find the value of this unknown Here, multiplying the first equation by 2, we have, quantity, as before.

4x + 8y = 40. EXAMPLE (5).-Given x + 3y=15, and 4x + 5y=32; to find Subtracting the second equation from this, we have, the values of æ and y.

3y = 12; Hore, transposing 3y in the first equation, we have,

Whence, y=4, and a=2. = 15 - 3y.

In the solution of the succeeding problems, either of the three Substituting the value of x in the second equation, we have,

rules for exterminating unknown quantities may be used at 60 -- 12y + 5y = 32;

pleasure. That quantity which is the least involved should be the Whence, by transposition, etc.,

one chosen to be first exterminated.

The student will find it a useful exercise to solve every And, from the first equation,

example by each of the several methods, and carefully to observo a = 15 -- 12 = 3.

which is the most comprehensive, and the best adapted to There is a third method of exterminating an unknown quantity

different classes of problems. from an equation, which, in many cases, is preferable to either added to the namerator,

the fraction will be equal to $; but if a

EXAMPLE (10).-To find a fraction such that, if a unit be of the preceding.

EXAMPLE (6).—Given x + 3y=a, and x-3y=0; to find the unit be added to the denominator, the fraction will be equal to values of & and y.

Let x = the numerator, and y=the denominator. Here, if we add together the first members of these two equa

Here, by the first condition, we have tions, and also the second members, we shall have,

y 2x = a + b,

And by the second, we have an equation which contains only the unknown quantity x. The

y+1 other, having equal co-efficients with contrary signs, has disap.

Whenco, a = 4, the numerator; peared. Still the equality of the sides is preserved, because we

And y=15, the denominator. have only added equal quantities to equal quantities.

Therefore, it is the required fraction.
Whence, a=

a + b
2

EXERCISE 38.
5
And

1. Given 2c + y = 16, and 3x – 3y = 6; to find the values of x and y. 3 6

2. Given 4x + 3y = 50, and 3x – 3y = 6; to find the values of cand y. EXAMPLE (7).--Given 3:+y= h, and 2c +y=d; to find the

3. Given 3x + y = 38, and 5x + 4y = 68; to find the values of x and ya values of a and y.

4. Given 4x - 40 = ~4y, and 6x - 63 = -7y; to find the values of x Here, if we subtract the second equation from the first, we 5. The numbers of two opposing armies are such, that the sum of shall have a h-d, where y is exterminated, without affecting both is 21,110; and twice the number in the greater army, the equality of the sides. Whence, y = 3d - 2h.

added to three times the number in the less, is 52,219. What EXAMPLE (8).--Given -2y = 0, and x +4y=b; to find

is the number in each army ? the values of æ and y.

.6. The sum of two numbers is 220, and if three times the less be

taken from four times the greater, the remainder will be 180. Here, multiplying the first equation by 2, we have,

What are the numbers ? 2x - 4y= 20;

7. The mast of a ship consists of two parts; one-third of the lower Then, adding the second and third equations, we have,

part added to one-sixth of the upper part, is equal to 28 feet;

and five times the lower part, diminished by six times the upper 6 + 2a;

part, is equal to 12 feet. What is the height of the mast ? Whence, {=}(b + 2a),

8. What two numbers are those, whose difference is to their sum as 2 And y=3(6-a).

to 3; and whose sam is to their product as 3 to 5 ?

9. To find two numbers such that the product of their sum and This process is called extermination by addition and sub difference shall be 5, and the produci of the sum of their traction,

squares and the difference of their squares shall be 65. EXERCISE 37.

10. To find two numbers whose sum is 32, and whose product is 210. 1. Given 8x + y = 42, and 2x + 4y = 18; to find the values of u and y.

11. To find two numbers whose sum is 52, and the sum of their 2. Given 2x + 8y=81, and 4+ 6y = 63; to find the values of 2 and y,

squares 1,421. 3. Given 3x + 3y = 72, and 4x + 5y = 116; to find the values of r

12. A certain number consists of two digits or figures, the sum of

which is 8. If 36 be added to the number, the digits will be 4. Giveu 4x + 10y = 124, and 2x + 9y = 134 ; to find the values of x

inverted. What is the number? and 3.

13. The united ages of A and B amonut to a certain number of years, 3. A privateer in chase of a ship 20 miles distant, sails 8 miles, while

consisting of two digits, the sum of which is 9. If 27 years the ship sails 7. How far will each sail before the privateer will

be subtracted from the amount of their ages, thọ digits will overtake the ship ?

be inverted. What is the sum of their ages ? 6. "The ages of two persons, A and B, are such that seven years ago A 14. A merchant having mixed

a quantity of brands and gin, found it was three times as old as B; and seven years hence, A will be

he had put in 6 gallons more of each, the comiponnd would have twice as old as B. What is the age of each ?

contained 7 gallons of brandy for every 6 of gin; but if he had 7. There are two numbers, of which the greater is to the less as 3 to.

put in 6 gallons less of each, the proportions would have been 2; and their sum is the sixth part of their product. What are

as 6 to 5. How many gallons did he mix of each ? the numbers? CASE III.—To exterminate an unknown quantity by addition

KEY TO EXERCISES IN LESSONS IN ALGEBRA. and subtraction.

EXERCISE 34. Rule.- Multiply or divide the equations, if necessary, by such

1. ds + 5a'h + 100'l' + 100?h' + 5d1* + ho. factors that the term which contains one of the unknown quantities

2. b* + A*-y + Bb - Sy? + CUP - Syö + D6*-*y* + eto., in which shall be the same in both equations. Then subtract one equalion

the co-efficients which are here represented by A, B, C, etc., are n-1 n-1n

etc. from the other, if the signs of this unknown quantity are alke, or

respectively ,

and y.

3a

aud y.

2

3

- 2ab + b.

in-2,*-345 +, etc.

3

4

19

3

m

3. 729x* + 2916x®y + 4860x*y* + 4320x* y& + 2160c”y* + 576xy* + 64y®. fishery. The Galapagos Islands are situated on the equator,

about 750 miles west of the state called Ecuador, to which thes 5. a - 3a*b + 3ab' -*.

belong. The Lobos Islands and the Chinca Islands, celebrated 6. a* - 4a'b + 6a'b' -4ab' +6.

for their guano, lie off the west coast of the state of Peru, to 7. 20 - 64*y + 15x*y' - 20.xoy® + 15x*y* - 6xy + yo.

which they belong. The island of Juan Fernandez lies nearly 400 8. a – nar-b + n^-^-^ ^ - n.

miles off the west coast of the State of Chili. The Patagonian 9. a -49% + 60% + 60 + 1.

Archipelago, including the islands of Chiloe, Chonos, Wellington, 10. 1-By + 15yo – 20y + 15y* - 6y + yo.

Madre de Dios Archipelago, Hanover, Adelaide, etc., lies west

of the country or region from which it receives its name. 11, 1 + na + n. 28+, etc.

North-east of Cape St. Roque, the easternmost point of Brazil, 6bxy

lie the islands of Fernando Noronha and Rocas; and near the 12. a' + a +

14.
+ 9x®y.

twentieth parallel of S. latitude, about 700 miles from the 36

coast, lie the islands of Trinidad and Martin Vaz. North of 13, - ba +

15.

abc + 4a76%.
49
7

the entire continent lie the West Indies, in the Caribbean Sea,
as described in a former lesson.

Seas, Gulfs, Bays.-Of inland seas in this continent there are LESSONS IN GEOGRAPHY.-XXXIX. none; and the gulfs and bays are small and unimportant. At

the north-west corner, where it joins North America, are found, SOUTH AMERICA.

on the Pacific side, the Bay of Panama and the Gulf of St. SOUTH America has on the map the appearance of the vertical Miguel; on the Atlantic side, and to the north of it, are the section of an irregularly shaped pear. The stalk end is broken Gulf of Darien, the Gulf of Maracaybo, the Gulf of Triste, the off at the island of Tierra del Fuego, where it meets the junction Galf of Paria, the estuary of the Orinoco, the estuary of the of the Atlantic and Pacific Oceans, on the south. The projec- Amazon, and the estuary of the Maranham. On the east of the tion of a map of this continent is to be made in the same continent are the bays of Todos Santos (or All Saints Bay), manner as a projection for a map of Africa, namely, by drawing Espirito Santo, the estuary of the Rio de la Plata, the Gulf of the parallels of latitude as horizontal straight lines, parallel to San Antonio, and the Bay of St. George. On the west, the each other, and equidistant by a space assumed to represent 5° Gulf of Penas, the Bay of Morena, the Bay of Pisco, the Gulf of or 10°, and the meridians as curved lines on either side of a Guyaquil, and the Bay of Choco. perpendicular, representing the meridian of 55° or 60° W. longi Mountains. The most remarkable natural feature in the contade, the curves being regulated by the comparative length of tinent of South America is, with one exception, the grand range the degree under each parallel of latitude laid down, as shown of mountains called the Cordillera de los Andes, or Chain of by a diagonal scale made for the purpose. The latitudes and the Andes, which run nearly parallel and comparatively close longitudes of places may be obtained from the index to any to its western shores. The commencement of this range is good atlas.

south of the Isthmus of Darien, and its termination is at the Boundaries. It is bounded by the Caribbean Sea on the Strait of Magellan, its whole extent being about 4,500 miles, north; by the Strait of Magellan on the south ; by the Pacific but varying considerably in altitude as well as in name. The Ocean on the west ; and by the Atlantic Ocean on the east. It mountains of this range, indeed, take their names according to is connected with the North American continent at the north the countries through which they pass ; hence we have the west point by the Isthmus of Panama, and includes the nar- Columbian, the Peruvian, the Bolivian, the Chilian, and the rowest portion of that isthmus, which forms the State of Patagonian Andes. The average height of the Columbian Panama, in the Granadian Confederation. The most northerly Andes is about 12,000 feet above the level of the sea, and the point of this continent is Point Gallinas, in New Granada, very highest peak is Chimborazo, which is 21,425 feet above the nearly in lat. 12° 30' N., and long. 71° 53' W.; the most same level. Antisana, Pichincha, Tolima, Cotopaxi, and others, sontherly point, including Tierra del Fuego, or the “ land of are little inferior in altitude to the “giant of the western fire," and the adjacent islands, is Cape Horn, in lat. 55° 59' S. world," and the last is reckoned the most tremendous volcano and long. 67° 12' W.; the most westerly point is Parina Point, on the face of the globe. The average height of the Peruvian near the Lobos Islands, in lat. 4° 43' $. and long. 81° 11' W.; and Bolivian Andes is greater than that of the Columbian and the most easterly point is the entrance to the River Goyana, chain, being about 14,000 feet; their highest peaks, Sorata and near Olinda, in lat. 7° 31' S. and long. 34° 47' W.

Illimani, reach the respective elevations of 21,190 feet and Length, Breadth, and Superficial Area. The length of this con- 21,150 feet above the level of the sea; and many of the passes tinent from north to south is about 4,800 miles; and its greatest across the chain of Upper Peru are about 16,000 feet above the breadth about 3,300 miles. The surface of South America, same level. The Chilian Andes have a less average elevation including its adjacent

islands south of the equator, is about than any of the former; but the peak of Aconcagua, which is 6,700,000 square miles; and the population is about 23,000,000; 23,910

feet above the level of the sea; overtops all the high hence this continent contains, on an average, about 3} inhabi- peaks already mentioned, and forms the culminating point of tants to every square mile.

South America. The Patagonian chain is very considerably Islands. The islands considered as belonging to South lower than any of the preceding, its average height being only America are few and unimportant. The largest, namely, Tierra 3,000 feet, and its highest peaks only 9,000 feet above the level del Fuego, is considered sterile, and scarcely habitable. Between of the sea. In Venezuela are the mountains of Parimé, the the continent and this island, and Clarence and Desolation culminating peak of which is Maravaca, about 10,500 feet above Islands to the west of it, lies the long, narrow, and winding the level of the sea. Along the southern frontier of Guiana strait, called by the name of Magellan, or Magalhaens, the runs a mountain range called the Sierra Acary, while Brazil is navigator who first sailed through it and discovered the passage traversed from north to south by several ranges parallel to each to the Pacific Ocean. Of the southern coast of Tierra del other, and of ro great altitude when compared to the Andes, Fuego lie Londonderry, Hoste, and Wollaston Islands, with the the principal of these being the Sierra del Espinhaço and the small islets, on the south of which is the famous headland Cordillera Grande. called Cape Horn, or Hoorn, after its discoverer. The islet, it Table-lands. The plateaus or table-lands of South America should be said, bears the same name. Staten Land is an island are formed of the elevated intervening

groands between the of small size, lying off its eastern coast, and separated

from it chains or ridges of its mountains just described, and they rival by the Strait of Le Maire. About 350 miles east of the entrance in elevation

those of the continent of Asia. The principal of to this strait lie the Falkland Islands, one of which is called these plateaus are those of Quito, Pasco, and Titicaca. The the East Falkland, and the other the West, between which runs elevation of the plateau of Quito, above the

sea-level, is about the Falkland Sound; besides these, this group consists of 200 9,600 feet; of Pasco, 13,700 feet; and of Titicaca, 12,850 feet. smaller islands, the area of the whole being about 13,000 square Rivers. The vast plains of South America give rise to miles. About 800 miles south-east of these islands lies the system of rivers unparalleled in the rest of the world for magni South Georgian group, the largest of which, South Georgia, tude and extent. The great central plain of this continent is from which the group takes its name, is 90 miles long by 10 divided into three large portions, which receive their names miles broad, and forms a useful depôt for the

seal and whale from the immense rivers which run through them respectively,

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