ANSWERS

PRACTICAL QUESTIONS AND PROBLEMS

CONTAINED IN

THE FOURTEEN WEEKS COURSES

Physiology, Philosophy, Astronomy, and

Chemistry (Old and New Edition),

BY

;p°DORMAN STEELE, PH.D., F.G.S.,

AUTHOR OF THE FOURTEEN WEEKS SERIES If! PHYSIOLOGY, PHILOSOPHY,
fl ASTRONOMY, AND* (JEOLOGY.

A. S. BARNES & COMPANY,
NEW YORK AND CHICAGO.

THE FOURTEEN WEEKS' COURSES

IN

NATURAL SCIENC

BY

J. DORMAN STEELE, A.M., Pn.D.

Fourteeij Weeks iij Natural Ptylosopty,
Fourteeij Weeks iij Cljenjistry,
Fourteeij Weeks iij Descriptive Astroijonjy,
Fourteeij Weeks iij Popular Geology,
Fourteeij Weeks iij Human Physiology,
Fourteeij Weeks iij Zoology,
Fourteerj Weeks in Botany,

A Key, containing Answers to the Questions
and Problems in Steele's 14 Weeks' Courses,

SERIES,

ON THE PLAN OF STEELE'S 14 WEEKS IN THE SCIENCES.

A Brief hjistory of the United States,
A Brief F|istory of Fraijce,

The same publishers also offer the following standard scientific
works, being more extended or difficult treatises than those of
Prof. Steele, though still of Academic grade.

Peck's Ganot's Natural Philosophy,
Porter's Principles of Chemistry,
Jarvis' Physiology and Laws of Healtfy
Wood's Botanist and Florist,
djanjbers' Elements of Zoology,
tyclij tyre's ^stro$)tfty and
Page's Elenjents of GeologJ, *s

tDUCATJON DEPT.

Entered according to Act of Congress, in the year 1869, by

A. S. BARNES & CO.,

In the Clerk's Office of the District Court of the United States
for the Southern District of New York.

STEELS' s JCPY.

PREFACE.

THIS little work is designed to aid teachers who are using
the Fourteen Weeks Course. The problems contained in
all the books are fully, and, it is thought, accurately solved.
Great pains have been taken to revise and compare them
carefully. The practical questions are answered, often not
in full, yet enough so to give the key to the more perfect
reply. The use of the text-books is presupposed, and the
statements merely supplement, or apply the fuller theories
therein contained and explained. On many points there
may be a difference of opinion. The author often finds in
his own classes a wide diversity. On mooted questions he
has merely advanced one view, leaving the subject open
for the discussion of other theories. Minute directions are
given, pages 71-82 inclusive, for performing a course of
experiments in Chemistry. It is hoped that these may be
of service to teachers who, with incomplete apparatus, are
trying to illustrate to their pupils some of the principles cf
that science. In all cases of doubt or misunderstanding
with regard to the answers or solutions, the author will be
pleased to correspond with any teacher using the Series

ELMIRA, March 19, 1870

ANSWERS

TO THE PEACTICAL QUESTIONS

m THE

FOURTEEN WEEKS COURSE

IN

NATURAL PHILOSOPHY.

|.The bold-faced figures refer to the pages of the Philosophy ; the others to
the number of th«. Practical Questions.]

INERTIA.

26. I. If one is riding rapidly, in which direction will he
be thrown when the horse is suddenly stopped ?

In the same direction in which he is going. He has the
motion of the carriage, and his inertia carries him forward.

2. When standing in a boat, why, as it starts, are we thrown
backward ?

Because the inertia of our bodies keeps them stationary,
while the boat carries our feet forward.

3. When carrying a cup of tea, if we move or stop quickly,
why is the liquid liable to spill?

The inertia of the tea tends to keep it still or in motion, as
the case may be. If we move the cup quickly, the motion is
not imparted to the liquid soon enough to overcome the
inertia. When, therefore, we start, the tea spills out back-
ward; or, when we stop, it spills out forward. We under-
stand this if we can tell why a cup of tea is more liable to spill
than one of sugar.

ANS^JKS TO PRAVT1VAL QUESTIONS

4. Why &>,fofrlo.d$*pfr'r'sued, \cctn we. escape by dodging?
We turn sharply. ' O'ur pursuer, ignorant of our design,

cannot overcome his inertia so as to turn as quickly, and
hence is carried past.

5. Why is a carriage or sleigh , when sharply turning a
corner, liable to tip over f

Because its inertia tends to carry it directly forward. A
puzzling question in this connection is — Why is a sleigh more
liable to tip over than a wagon ?

6. Why, if you place a card on your finger, and on top of it
a cent, can you snap the card from under the cent 'without
knocking the latter off your finger?

Because the friction between the card and the cent is so
slight that, by a quick snap, you can overcome the inertia of
the former without imparting any force to the latter.

7. Why } after the sails of a vessel are furled, does it still
continue to move; and why, after the sails are all spread,
does it require some time to get under full headway?

Its inertia must be overcome in the one case by the resist-
ance of the air and water, and in the other by the force of the
wind.

COHESION.

4O. i . Why can we not weld a piece of copper to one of
iron ?

Cohesion acts only between molecules of the same kind.

2. Why is a bar of iron stronger than one of wood?
Because its force of cohesion is stronger.

3. Why is a piece of iron, when perfectly welded, stronger
than before it was broken f

By the hammering, more particles are brought within the
range of cohesion.

4. Why do drops of different liquids vary in size f
Because they vary in cohesive force.

5. Why, when you drop medicine, will the last few drops
contained in the bottle be of a larger size than the others ?

/2V NATUKAL PHILOSOPHY. 7

The pressure of the liquid in the bottle is less, and therefore*
they form more slowly.

6. Why are drops larger if you drop them slowly ?

There is more time for the adhesive force of the bottle to
act on the liquid, and so a larger drop can be gathered.

7. Why is a tube stronger than a rod of the same weight?
Let a rod supported at both ends be broken in the middle.

We shall see that it yields first on the circumference. So true
is this, that long beams heavily loaded have been broken by a
mere scratch of a pin on the lower side. The particles along
the centre break last. They rather aid in the fracture, since
they afford a fulcrum for the rest of the rod, acting as the long
arms of a lever, to act upon. In a tube the particles at the
centre are removed and all concentrated at the outside, where
the first strain is felt. (See Physiology, p. 20).

8. Why, if you melt scraps of zinc ', will they form a solid
mass when cooled?

The heat overcomes, in part, the attraction of cohesion, so
that the particles flow freely on each other. They now all
come within the range of cohesion, so that when the metal
cools they are held by that force in a solid mass.

9. In what liquids is the force of cohesion greatest?
Mercury, molasses, etc.

10. Name some solids that will volatilize without melting f
Arsenic, camphor.

ADHESION.

47. i. Why does cloth shrink when wet?

By capillary attraction the water is drawn into the pores 01
the cloth. The fibres are thus expanded sidewise and short-
ened lengthwise. The cloth "fulls up" or thickens while it
shortens and narrows (shrinks) in the process.

2. Why do sailors at a boat-race wet the sails ?
The pores being full and expanded make the sails more com-
pact. They will therefore hold the wind better.

8 ANSWERS TO PRACTICAL QUESTIONS

3. Why does not writing-paper blot?

Because the pores are filled with size. (See Chemistry,
p. 161.)

4. Why does paint prevent wood from shrinking?
Because it fills the pores of the wood.

5. What is the shape of the surface of a glass of water and
one of mercury f

Ordinarily the former is concave and the latter convex.

6. Why can we not dry a towel perfectly by wringing ?
Because of the strength of the capillary force by which the

water is held in the pores of the cloth.

x

7. Why will not water run through a fine sieve when the
wires have been greased?

Because the grease repels the water and so prevents capil-
lary action.

8. Why will camphor dissolve in alcohol and not in water?
Because there is a strong adhesion between the alcohol and

camphor, and little, if any, between the water and camphor.

9. Why will mercury rise in zinc tubes as water does in
glass tubes ?

Because of the strong adhesion between zinc and mercury.

10. Why is it so difficult to lift a board out of water ?
Because of the adhesion between the board and the water.

1 1 . Why will ink spilled on the edge of a book extend further
inside than if spilled on the side of the leaves?

Because the capillary pores of the paper are short, being
only the thickness of a leaf, while the capillary spaces between
the leaves are longer and continuous.

12. If you should happen to spill some ink on the edge of
y cur book, ought you to press the leaves together?

No. Because you would make the capillary spaces between
the leaves smaller, and so the ink would rise in them further.

13. Why can you not mix oil and water ?
Because there is no adhesion between them.

IN NATURAL PHILOSOPHY. 9

15. Why will water wet your hand while mercury will not?
Because in the former case there is an adhesion, in the
latter none.

1 6 Why is a tub or pail liable to fall to pieces if not filled
with water or kept in the cellar?

Because the moisture dries out of the pores, and the wood
shrinks so as to let the hoops fall off.

17. Name instances where the attraction of adhesion h
stronger than that of cohesion.

Wood fastened by glue will often split before the glue will
yield. Paper stuck with paste, and bricks with mortar, are also
examples.

GRAVITATION.

63. i. When an apple falls to the ground ^ how much does
the earth rise to meet it?

The earth falls as much less distance than the apple, as its
weight is greater.

2. What causes the sawdust in a mill-pond to collect in large
masses ?

The attraction of gravity which exists between all bodies,
whereby they attract each other. All bodies on the earth
would tend to approach each other, and the big ones would
gather all the little ones around them were they as free to move
as the sawdust floating on water.

3. Will a body weigh more in a valley than on a mountain f
It will, because the attraction of the earth is greater.

4. Will a pound weight fall more slowly than a two-pound
weight ?

They will both fall in the same time, except the slight
difference which is caused by the resistance of the air. Galileo
propounded this view and proved it, in the presence of a vast
crowd, by letting unequal weights fall from the leaning tower
of Pisa.

IO ANSWERS TO PRACTICAL QUESTIONS

5. How deep is a well, if it takes three seconds for a stone to
fall to the bottom of it ?

(2) equation of falling bodies, d = 1W ; hence d = 16 x 3a a 144 feet.

_6. Is the centre of gravity always within a body — as ', for
example, a ring?

It is not. In the case given it is at the centre of the circle.

7. If two bodies, weighing respectively i and 4 pounds, be
connected by a rod 24 inches long, where is the centre of gravity ?

To be In equilibrium the weight of one multiplied by its distance from the
c«:nt-re of gravity must equal the weight of the other multiplied by its distance.
24 -+- 6 = 4 ; hence 4 in. is the unit for each pound. Therefore the centre of
gravity is 8 in. from the larger weight and 16 in. from the smaller.

- 8. In a ball of equal density throughout, where is the centre
of gravity ?

At the centre of the ball.

9. Why does a ball roll down hill?

Because the line of direction falls without the small base of the
ball.

10. Why is it easier to roll a round body than a square one f
Because the base of the ball is so much smaller, and therefore

the centre of gravity need not be raised to bring the line of di-
rection without.

1 1. Why is it easier to tip over a load of hay than one of
stone ?

Because the centre of gravity in a load of hay is very high,
and in a load of stone very low. Therefore the centre of
gravity in the former need not be raised much to bring the
line of direction without the base, while in the latter it must be.

12. Why is a pyramid the stablest of structures ?

Because the base is so broad and the centre of gravity so
low. The centre of gravity must therefore be lifted very high
before the line of direction will fall without the base.

13. When a hammer is thrown, on which end does it always
strike f

On the heavy end or head, because that part is attracted by
the earth more strongly.

IN NATURAL PHILOSOPHY. I J

14. Why does a rope-walker carry a heavy balancing-pole ?
Because in this way he can easily shift his centre of gravity.

15. What would become of a ball if dropped i*ito a hole
bored through the centre of the earth ?

In falling, it would gain a momentum which would carry it
past the centre of the earth. But as it is constantly coming
to a part having a slower axial revolution than itself, it would
scrape on the east side of the hole until it reached the centre ;
beyond that point it would scrape on the west side. This
friction would prevent its reaching the opposite side of the
earth. It would therefore vibrate to and fro, each time through
a shorter distance, until, at last, it would come to rest at the
centre of the earth.

1 6. Would a clock lose or gain time if carried to the top of
J a mountain ?

It would lose time, because the force of gravity would be
lessened. At the North Pole it would gain time, because there
the force of gravity would be increased.

1 7. In the winter, would you raise or lower the pendulum-
bob of your clock ?

I would lower it, since the cold of winter shortens the pen-
dulum, and this movement of the bob would counteract that
change.

1 8. Why is the pendulum-bob always made flat?
To decrease the friction of the air.

19. What beats off the time in a watch f
The vibration of the balance-wheel.

20. Is solved in the book.

21. What should be the length of a pendulum at New YorA
to vibrate half-seconds ?

(1 sec.)» : (Va sec.)2 : : 39.1 in. : x = 9.7 + inches.
To vibrate quarter-seconds ?

(1 sec.)' : (V4 sec.)' : : 39.1 in. : x = 2.4 + inches.
To vibrate hours f

(1 sec.)3 : (3600 sec.)3 : : 39.1 in. : x - 7997.7 miles.*

* Nearly the diametor of the earth.

12 ANSWERS TO PRACTICAL QUESTIONS

22. What is the proportionate time of vibration of two pen*
dulutns^ 1 6 and 64 inches long, respectively ?

According to the third law of pendulums,
Time of vib. of 1st : Time of vib. of 2d : : v/16 : v/64 : : 4 : 8 : : 1 : 2.

23. Why, when you are standing erect against a wall, and
a piece of money is placed between your feet, can you not stoop
forward and pick it up ?

By leaning forward you bring the centre of gravity in front
of your feet, and, as on account of the wall, you cannot throw
any part of your body back to preserve the balance, you fall
forward.

24. If a tower were 198 feet high, with what velocity would
a stone dropped from the summit, strike the ground f

According to equation (3), t>2 = 64 d. t?2 = 64 x 198. 0=112.5 feet.

25. A body falls in 5 seconds : with what velocity does it
strike the ground?

According to equation (1), v = 32 t. v =32 x 5. v =160 feet.

26. How far will a body fall in 10 seconds ?

According to equation (2), d = 16 £2. d = 16 x 102 = 1600 feet.
With what velocity will it strike the ground?

According to equation (1), v = 32 t. v = 32 x 10 = 320 feet.

27. A body is thrown upward with a velocity of 192 feet the
first second ; to what height will it rise ?

Equation (1), v = 32 t. 192 = 32 t. t = Q sec.

(2), d = 16 P. d = 16 x 62=576 feet.

28. A ball is shot upward with a velocity of 256 feet ; to
what height will it rise ? How long will it contin ue to ascend f

Using equations (1) and (2), as in the last problem, we hare :

t = 8 sec.
d = 1024 feet.

30. Are any two plumb-lines parallel?
They are not, since they all point to the centre of the earth.
No two spokes of a wheel can be parallel

IN NATURAL PHILOSOPHY. 13

31. A stone let fall from a bridge strikes the water in three
seconds. What is the height ?

Equation (2), d = 16t\ d = 16 x 39 = 144 feet.

32. A stone falls from a church steeple in 4 seconds. What
is the height?

Equation (2), d = 16*a. d = 16 x 4s = 256 feet.

33. How far would a body fall the first second at a height
of 12,000 miles above the earth's surface?

(16,000 mi.)a : (4000 mi,)2 : : 16 feet : x = 1 foot.

34. A body at the surf ace of the earth weighs 100 tons :
what would be its weight 1 ,000 miles above ?

,(5000 mi.)3 : (4000 mi.)2 : : 100 tons : x = 64 tons.

35. A boy wishing to find the height of a steeple lets fly an
arrow that just reaches the top and then falls to the ground.
It is in the air 6 seconds. Required the height.

Equation (2), d = 16<a. d = 16 x 3* = 144 ft.

36. A cat let fall from a balloon reaches the ground in 10
seconds. Required the distance.

Equation (2), d = 16 x 10a = 1600 ft,

37. In what time will a pendulum 40 feet long make a
vibration f

According 1o the third law of pendulums, and taking the length of a seconds
pendulum as 39 in., we have :

1 sec. : x : : V§9 : 1/40x12 in.

x = 3.5+ sec.

— In what time will a pendulum 52 feet long make a vi«
bration?

14 ANSWERS TO PRACTICAL QUESTIONS

—How long would it take for a pendulum one mile in length
to make, a vibration ?

— How long would it take for a pendulum reac king from
the earth to the moon to make a vibration ?

— Required the length of a pendulum that would vibrate
centuries. ( 70 be solved like problem 20. )

38. Two meteoric bodies in space are 12 miles apart. They
weigh 100 and 200 Ibs. respectively. If they should fall
together by force of their mutual attraction, what portion of
the distance would be passed over by each body ?

The distance passed over by the two bodies is inversely as
their mass; hence one moves 8 miles and the other 4 miles.

39. If a body weighs 2,000 Ibs. upon the surface of the earth,
what would it weigh 2,000 miles above ?

(6000 mi.)2 : (4000 mi.)3 : : 2000 Ibs. : x = 888*/« Ibs.
• How much 500 miles above?

(4500 mi.)2 : (4000 mi.)3 : : 2000 Ibs. : x = 1580+ Ibs.
The weight of bodies below the surface of the earth de-
creases as the distance increases. Ex. : What would the above
body weigh if carried 2 , ooo miles below the surface ? I , ooo Ibs.
— i , ooo m iles below ? i , 5 oo Ibs.

40. At what distance above the surface of the earth will a
body fall, the first second, 2 1 \ inches ?

A body falls 16 ft.* (192 inches) at the surface of the earth. 21 1/3 inches are
:/9 of 192 inches : Now as the attraction is inversely as the square of the dis-
tance, the distance must be v/9, or 3 times that at the surface. Hence the body
must be 12,000 miles from the centre, or 8,000 miles from the surface of the
earth. The problem may be solved directly by proportion, thus :

a2 : 40002 : : 192 inches : 21 Vs inches.

* = 12000 miles (distance from the centre)

12000 miles— 4000 miles =8000 miles.

41. How far will a body fall in 8 seconds? 1,024 ft. — In
the %th second? 240 ft. — In 10 seconds? 1,600 ft. — In th*
30^ second? 944 ft.

* According to the best authorities the distance is more exactly 16l/ir ft.

IN NA TUB A L PHILOSOPHY. I 5

MOTION.

8O. i. Can a rifle-ball be fired through a handkerchief sus-
pended loosely from one corner?

Yes. The wind of the ball will lift the handkerchief somewhat.

2. A rifle-ball thrown against a board standing edgewise
will knock it down j the same bullet fired at the board will
pass through it "without disturbing its position. Why is this?

The ball which is thrown has time to impart its motion to
the board ; the one fired has not.

3. Why can a boy skate, safely over a piece of thin ice, when,
if he should pause, it would break under him directly ?

In the former case there is time for the weight of his body to
be communicated to the ice ; in the latter, there is not.

4. Why can a cannon-ball be fired through a door standing
ajar, without moving it on its hinges ?

Because the cannon-ball is moving so quickly that its motion
is not imparted to the door.

5. Why can we drive on the head of a hammer by simply
striking the end of the handle ?

This can only be done by a quick, sharp blow which will
drive the wooden handle through the socket before the motion
has time to overcome the inertia of the iron head. A slow,
steady blow will be imparted to the head, and so fail of the
desired effect.

6. Suppose you were on a train of cars moving at the rate
oj '30 miles per hour : with what force would you be thrown
forward if the train were stopped instantly?

With the same velocity which the train had, 01 44 feet pet
second. Your momentum would be your weight avoirdupois
multiplied by this velocity.

7. In what line does a stone fall from the mast-head of a
vessel in motion ?

In a curved line, produced by the two forces — gravity and
the forward motion of the vessel.

1 6 ANSWERS TO PRACTICAL qUESTlONS

8. If a ball be dropped from a high tower it will strike the
earth a little east of a vertical line. IV hy is this ?

In the daily revolution of the earth on its axis, from west to
east, the top of the tower moves faster than the bottom, be-
cause it passes through a larger circle. When, therefore, the
ball falls, it retains that swifter easterly motion and so strikes
east of the vertical.

9. // is stated that a suit was once brought by the driver of
a light-wagon against the owner of a coach for damages caused
by a collision. The complaint was that the latter was driving
so fast, that when the two carriages struck, the driver of the
former was thrown forward over the dash-board. Show how
his own testimony proved him to have been at fault.

When the light-wagon was suddenly stopped, its driver went
on by his inertia with the same speed at which the wagon was
moving. That this threw him forward over the dash-board,
proves his speed to have been unusual.

10. Suppose a train moving at the rate of '30 miles per hour ;
on the rear platform is a cannon aimed parallel with the track
and in a direction precisely opposite to the motion of the car.
Let a ball be discharged with the exact speed of the train,
where would it fall?

In a vertical line to the track. The two equal, opposite
motions would exactly destroy each other.

11. Suppose a steamer in rapid motion and on its deck a
man jumping. Can he jump further by leaping the way the
boat is moving or in the opposite direction ?

It will make no difference as long as he jumps on the deck.
Should he jump off the boat, then the effect would be different.

12. Why is a running jump longer than a standing one?
Because the motion gained in running is retained in the

jump and adds to its distance.

13. If a stone be dropped from the mast-head of a vesselin
motion, will it strike the same spot on the deck that it would if
the vessel were at rest ?

It will. It falls with the motion of the vessel, and goes just
as far forward while falling as the vessel does.

IN NATURAL PHILOSOPHY. 17

\

14. Could a party play ball on the deck of the Great Eastern
when steaming along at the rate of 20 miles per hour, without
making allowance for the motion of the ship?

They could. The ball would have the motion of the ship,
and would move with it in whatever direction they might
throw it.

15. Since "action is equal to reaction," why is it not as dan-
gerous to receive the " kick" of a gun as the force of the bullet?

The striking force is as the square of the velocity; and the
velocity with which the gun moves backward is as much less
than that with which the bullet moves forward, as the gun is
heavier than the bullet. For this reason a heavy gun will
kick much less than a light one.

1 6. If you were to jump from a carriage in rapid motion,
would you leap directly toward the spot on which you wished
to alight?

No ; because as one jumps from the wagon he has its for-
ward motion, and will go just as far ahead, while leaping, as
he would if he had remained in the carriage. He should,
therefore, aim a little back of the desired alighting-place.

1.7. If you wished to shoot a bird in swift flight, would you
aim directly at it ?

No. The bird will fly forward while the bullet is going to
it. One should, therefore, aim a little in advance.

1 8. At what parts of the earth is the centrifugal force the
least?

The poles. They simply turn around in 24 hours.

19. What causes the mud to fly from the wheels of a carriage
in rapid motion ?

The centrifugal force.

20. What proof have we that the earth was once a soft mass ?
It is flattened at the poles. This effect is produced upon a

ball of soft clay by simply revolving it on a wire axis.

21. On a curve in a railroad, why is one track always
higher than the other?

1 8 ANSWERS TO PRACTICAL QUESTIONS

The outer track is raised that gravity may balance the cen-
trifugal force.

22. What is the principle of the sling f

The sling is whirled until a strong centrifugal force is
generated ; the string, the centripetal force, is then released,
when the stone flies off at a tangent.

23. The mouth of the Mississippi river is about T.\ miles
further from the centre of the earth than its source. What
causes its water to thus "run up hill?"

The centrifugal force produced by the revolution of the earth
on its axis tends to drive the water from the poles toward the
equator. Were the earth to stand still in its daily rotation, the
Gulf of Mexico would empty its waters back through the Mis-
sissippi to the northern regions.

24. Is it action or reaction that breaks an egg when I strike
it against the table f

The reaction of the table.

25. Was the man philosophical who said ll it was not thr
falling so far but the stopping so quick that hurt him f"

He was.

26. If one person runs against another, which receives the
greater blow f

Action is equal to reaction : hence the blows must be equal.

27. Would it vary the effect if the two persons were running
in opposite directions ?

The blow would then be the sum of both their momenta.

If they were running in the same direction ?

The blow would be equal to the difference of their momenta.

28. Why can you not fire a rifle-ball around a hill? •
Because a single force always produces motion in a straight

line.

29. Why does a heavy gun " kicK" less than a light one?
See problem 15.

30. A man on the deck of a large steamer draws a small

IN NATUBAL PHILOSOPHY. 19

boat toward him. How much does the ship move to meet tht
boat?

The ship moves as much less distance than the boat, as it is
heavier than the boat.

31. Suppose a string, fastened at one end, will just support
a weight of '25 Ibs. at the other. Unfasten it, and let two per-
sons pull ripon it in opposite directions. How much can each
pull without breaking it ?

25 Ibs. The second person, in the latter case, can pull as
much as the nail did in the former.

32. Can a man standing on a platform-scale make himself
lighter by lifting up on himself?

He cannot ; because action is equal to reaction, and in an
opposite direction. As much as he lifts up, so much must he
press down.

33. Why cannot a man lift himself by pulling up on hi\
boot-straps f

See last problem.

34. If from a gun placed vertically, a ball were Jired into
perfectly still air, where would it fall?

It would return into the gun.

35. With what momentum would a steamboat weighing
1,000 tons, and moving with a velocity of 10 feet per second,
strike against a. sunken rock f

1000 tons x 10a = 100,000 tons.

36. With what momentum would a train of cars weighing
loo tons, and running 10 miles per hour, strike against an
obstacle?

The velocity per second is 142/3 ft. 100 tons x (14V,)' = 21,511% tons.

37. What would be the comparative striking-force of two
hammers, one driven with a velocity of '20 feet per second, ana
the other lofeet?

202 = 400. 102 = 100. 400 : 100 . : 1 : 4. Hence one will strike four times as
hard a blow as the other. This principle is of great importance in chopping
wood, splitting rails, and in all cases where percussion is concerned. The
highest attainable velocity is to be sought.

2O AM8WERS TO PRACTICAL QUESTIONS

— There is a story told of a man who erected a huge pair of
bellows in the stern of his pleasure-boat, that he might always
have a fair wind. On trial the plan failed. In which di-
rection should he have turned the bellows f

In the manner adopted at first, of turning the nozzle toward
ihe sails, the action of the wind against the sails and the re-
action of the bellows against the boat just balanced each other.
If the man had turned the nozzle backward he could have
saved the reaction of the bellows to move the boat. This
would, however, have been a most costly and bungling way
of navigation.

— If we whirl a pail of water swiftly around with our hand,
why will the water all tend to leave the centre of the pail ?
Why will the foam all collect in the hollow at the centre ?

THE MECHANICAL POWERS.

90. i. Describe the rudder of a boat as a lever.

The water is the F, the boat the W, and the hand the P.
As the W is between the F and the P, it is a lever of the
second class.

2. Show the change that occurs from the second to the third
class of levers, when you take hold of a ladder at one end and
raise it against a building.

At first the ground is the F at one end, the hand the P at
the other, and the ladder the W hanging between ; hence this
is a lever of the second class. After a little, the F remaining
the same, the P is applied at one end, near the F, and the
ladder is the W hanging at the other ; hence this is now a
lever of the third class.

3. Why is a pinch from the tongs near the hinge more
severe than one near the end f

Because in the former case the tongs are a lever of the first
class — in the latter, of the third. In the first class there is a
gain of power, in the third a loss.

4. Two persons are carrying a weight 0/250 Ibs., hanging

IN NA TURAL PHIL OSOPHT. 2 I

between them from a pole 10 feet in length. Where should it
be suspended so that one will lift only 50 Ibs. ?

One lifts 50 Ibs. ; the other 200 Ibs. The proportionate length of the arms
of the lever should be the same as the proportionate weights— i. «., 1 to 4.
10 •*• 5 = 2, the unit of measure. Hence one arm is 2 feet long and the other
8 feet long. PROOF.— (See Prob. 7, p. 10.) 50 x 8 = 200 x 2. This is the
Bubstance also of the equation P x Pd = W x Wd.

5. In a lever of the first class, 6 feet long, where should tht
F be placed so that a P of \ Ib. will balance a W of 2.3 Ibs. f

6 feet = 72 inches. 72 -*- 24 = 3, the unit of distance. The W must be
placed 3 in. and the P 69 in. from the F. PROOF. 23 x 3 = 1 x 69 (Prob. 4).

6. What P would be required to lift a barrel of pork with a
windlass whose axle is one foot in diameter and handle 3 ft.

long?

P : W : rad. of axle : : rad. of wheol.

a; : 200 Ibs : : Va ft. : 3 ft.
x = 33Vs Ibs.

7. What sized axle, with a wheel 6 feet in diameter, would
be required to balance a W of i ton by a P of 100 Ibs. f

P : W : : rad. of axle : rad. of wheel.

100 Ibs. : 2000 Ibs. : : x : 3 ft.
x = '/ao ft- = the r&d- ; hence the diameter = 8/io ft-

8. What number of movable pulleys would be required to
lift a W of 200 Ibs. with a P of 2$ Ibs. ?

TTT

W— P x twice the no. of mov. pulleys ; hence — = twice the no. of mov. pul's.
200 •+• 25 = 8. 8 -*- 2 = 4 = the no. required.

9. How many Ibs. could be lifted with a system of '4 movable
pulleys, and one fixed pulley to change the direction of the
force, by a P of 100 Ibs. ?

W= P x twice the no. of mov. pulleys.
100 Ibs. x (4 x 2) = 800 Ibs. = the W.

10. What weight could be lifted with a single horse-power
^33,000 Ibs.) acting on the tackle-block? (Fig. 62.)

This block has 3 movable pulleys, and using the equation of the pulleys given
in the last two problems, we have, making no allowance for friction,

33,000 Ibs. x (3x2) = 198,000 Ibs.

22 ANSWERS TO PRACTICAL QUESTIONS

1 1. What distance should there be between the threads of a
screw, that a Po/2$ Ids., acting on a handle 3 //. long, may
lift i ton weight?

F : W : : Interval : Circumference.

25 Ibs. : 2000 Ibs. : : x : 72 in. x 3.1416.

x = 2.83 -in.

12. How high could a P of 11 Ibs., moving i6//. along an
inclined plane, lift a W 'of '96 Ibs.?

P : W : : height : length.

12 Ibs : 96 Ibs. : : x : 16 ft.

x = 2 ft.

13. / wish to roll a barrel of flour into a wagon, the box of
which is 4//. from the ground. I can lift but 24 Ibs. How
long a plank should I get?

P : W : : height : length.
24 Ibs : 196 Ibs. : : 4 ft. : x = 322/3 ft.

14. The " evener" of a pair of whiffletrees is ^ft. 6 in. long ,
how much must the whiffletree be moved to give one horse the
advantage of \ over the other ?

For every 3 Ibs. one horse pulls, the other must pull 4 Ibs. : hence 7 represents
the proportion in which the load is to be divided. 3 ft. 6 in. = 42 inches. 42
in. -*-7 = 6 inches, the unit of measure. Hence one arm of the evener must be
6 in. x 3 = 18 in. long, and the other 6 in. x 4 = 24 in. long. Or, if we prefer, we
may say 21 in. — 3 in. = 18 in. Ions:, and 21 in. + 3 in. = 24 in. long. PROOF.-
(See Prob. 4, p. 20.) 18 x 4 = 24 x 3 = 72.

15. In a set of three horse whiffletrees, having an " evene-r"
5//. long, at what point should the plough-clevis be attached
that the single horse may draw the same as each one of the
span of horses ?

For every Ib. drawn by the single horse the span should draw 2 Ibs. : hence
3 represents the proportion in which the load is to be divided. 60 hi. •+• 3 = 20
in., the unit of measure. 20 in. x 1 = 20 in., and 20 in. x 2 = 40 in. Hence eno
arm mast be 20 in., and the other 40 in. long.

To give \ advantage ?

The single horse should draw 3 Ibs. and each of the others 4 Ibs. : hence the
span should draw 8 Ibs. 60 in. •+- 11 = 56/n in., the unit of measure. 5»/n in.
x 3 = 16«/ii in., and 56/u in. x 8 = 437/n in.

1 6. What W can be lifted with a P of 100 Ibs. acting en a
screw having threads \ of an inch apart and a lever handle 4
//. long?

72V NATURAL PHILOSOPHY. 2)

P : W : : Interval : Circumference.
100 Ibs. : x : : »/4 in. : 96 in. x 3.1416.
x = 120,637 -fibs.

17. What is the object of the big balls cast on the ends of tht
handle of the screw used in copying-presses ?

By their inertia and centrifugal force they make the motion
more uniform and continuous.

1 8. In a steelyard 7. ft. long, the distance from the 'weight-
hook to the fulcrum-hook is i in. How heavy a body can be
•weighed with a I Ib. weight at the further end ?

84 in.— 2 in. = 22 in. 1 Ib. x 22 = 22 Ibs. = P. 22 Ibs. •+- 2 = 11 Ibs. = W.

19. Describe the change from the \st to the ^d class of levers,
in the different ways of using a spade.

When digging, the ground at the back of the spade is the
F ; the ground lifted is the W ; and the hand at the other end
is the P. As the W is at one end, P at the other, and the F
between, this is a lever of the ist class. When throwing
dirt, the left hand at one end of the spade is the F ; the dirt
at the other end is the W, and the right hand between the
two is the P. As the P is between the F and the W, this is a
lever of the 3d class.

20. Why are not blacksmiths' and fire tongs constructed on
the same principle ?

The former are of the ist class, as power is required: the
latter of the 3d class, as rapidity only is necessary.

21. In a lever of the $d class, what W will a P of 50 Ibs.
balance, if one arm is 12 ft. and the other 3 ft. long?

P : W : : Wd : Pd .

50 Ibs. : x : : 12 ft. : 3 ft.
x = 12Va Ibs.

22. In a lever of the id class, what W will a P of 50 Ibs.
balance, with a lever 12 feet long and W ^ feet from the Ff

50 lb«. : x : : 3 ft. : 12 ft.

x = 200 Ibs.

24 ANSWERS TO PRACTICAL QUESTIONS

23. In a lever of the ist class ; what IV will a P of 50 Ibs
balance, with a lever 12 ft. long and the F '3 ft. from the IV?

50 Ibs. : x : : 3 ft. : 9 ft.
x = 150 Ibs.

24. In a wheel and axle, the P=^o Ibs., ^=360 Ibs.,
diameter of axle = 8 in. Required the circumference of thi
•wheel.

P : W :: diameter of axle : diam. of wheel

40 Ibs. : 360 Ibs. : : 8 in. : x - 72 in. = 6 ft., the diameter of wheel.
6 ft. x 3.1416 = 18.85 ft., the circumference of the wheel.

25. In a wheel and axle the P =-20 Ibs., the ^=240 Its.,
and the diameter of wheel = \ft. Required the circumference,
of the axle.

20 Ibs : 240 Ibs :: a? : 48 in.

X = 4 in. (diameter of axle).

4 in. x 3.1416 = 12.56 in. (circumference).

26. Required, in a wheel and axle, the diameter of the wheel,
the diameter of the axle being 10 inches, P = 100 Ibs. and W
— I ton.

100 Ibs. : 2000 Ibs. : : 10 in. : x = 200 in. = 16a/s ft.

27. What P would be necessary to sustain a weight oj
3,780 Ibs., with a system of 6 movable pulleys and one ropef

W = P x twice the no. of mov. pulleys.
3,780 Ibs. = P x (6 x 2). P = 315 Ibs.

28. How many movable pulleys would be required to sustain
i W 0/420 Ibs. with a P of 210 Ibs. f — Ans. I.

HYDROSTATICS.

121. i. Why do housekeepers test the strength of lye, by
trying whether or not an egg will float on it ?

The potash dissolved in the water to form lye increases the
density of the liquid. When enough has been dissolved to
make its specific gravity greater than that of the egg, the egg
will float. This becomes, therefore, a simple means of testing
the amount of potash contained in the lye.

/A AATUHAL PHILOSOPHY. 25

'2. How muck wafer will it take to make a gallon of strong
brine ?

A gallon. The salt does not increase the bulk of the liquid.

3. Why can a fat man swim easier than a lean one ?
Because muscles and bones are heavier than fat. The speci-
fic gravity of a fat man is therefore less than that of a lean one.

4. Why does the firing of a cannon over the water sometimes
bring to the surface the body of a drowned person ?

One answer is given in the Philosophy. It is probable, also,
that the firing of the gun produces a partial vacuum, or in
some way takes off, for an instant, a part of the pressure of the
air on the water. The gases in the body would then expand
and bring it to the top.

6. If we let bubbles of air pass up through a jar of water,
why will they become larger as they ascend?

The pressure of the water is less as they near the top, and
so they expand.

7. What is the pressure on a lock-gate 14 feet high and 10
feet wide, when the lock is full of water ?

14 x 10 x 7 x 1000 oz. = 980,000 oz. = 61,250 Ibs.

5. Will a pail of water weigh any more with a live Jish in
it than without ?

If the pail were full before the fish was put in, then it will
make no difference, since the fish will displace its own weight
of water, which will run over. If the pail is only partially
filled, then, though the fish is upheld by the buoyancy of the
water, since action is equal to reaction, it adds its own weight
to that of the water.

— If a man and a boy were riding in a wagon, and, on com-
ing to the foot of a hill, the man should take up the boy in his
arms, would not that help the horse?

9. If the water filtering down through a rock should collect
in a crevice an inch square and 250 feet high, opening at the
bottom into a closed fissure having 20 square feet of surface,
•whut would be the total pressure tending to break the rock ?

2

26 ANSWERS TO PRACTICAL QUESTIONS

The pressure is proportional to the height and not the size of the column,
hence the pressure ia

20 x 250 x 1000 oz. = 5,000,000 oz. = 312,500 Ibs.

10. Why can stones in water be moved so imtch mort easily
than on land?

Because the water buoys up about one-half of their weight.

11. Why is it so difficult to wade in the water where there
is any current?

Because the buoyant force of the water makes us so light
that we are easily carried away from our footing.

12. Why is a mill-dam or a canal embankment small at the.
top and large at the bottom ?

Because the pressure of the water increases with the depth.

13. In digging canals and building railroads, oiight not the
engineer to take into consideration the curvature of the earth ?

Certainly. If he should build on a true level he would find
his embankment pointing up to the stars.

14. Is the water at the bottom of the ocean denser than that
at the surface f

The immense pressure must condense it very much at great
depths. There is a certain point beyond which divers cannot
penetrate.

15. Why does the bubble of air in a spirit-level move as the
instrument is turned?

Because the air is lighter than the alcohol and rises con-
stantly to the highest point. For this reason, also, the tube
is curved upward at the centre.

1 6. Why can a swimmer tread on glass and other sharp
substances at the bottom of the water with little harm ?

See problem 11.

1 7. Will a vessel draw more water in salt or in fresh water f
In fresh, because its specific gravity is less.

1 8. Will iron sink in mercury ?

No. It will float, like a cork on water.

19. The water in the reservoir in New York is about 80 feel

IN NA TOR A L PHIL OSOPHT. 2 J

above the fountain in the City Hall Park. What is the pres-
sure on a single hick of the pipe at the latter point f

(1000 oz. x 80) •*• 144 = 34.7 Ibs.

20. Why does cream rise on milk ?
Because it is lighter than the milk.

21. If a skip founders at sea, to what depth will it sink ?
Until its specific gravity becomes equal to that of the water ?

22. There is a story told of a Chinese boy who accidentally
dropped his ball into a deep hole, where he ctfuld not reach it.
He filled the hole with water, but the ball would not quite float.
He finally bethought himself of a lucky expedient, which was
successful. Can you guess it ?

He put salt in the water.

23. Which has the greater buoyant force, oil or water?
Water, because its density is greater.

24. What is the weight of '4 cu. ft. of cork ?

1000 oz. = the weight of 1 en. ft. of water

.240 = the spec. grav. of cork.
240 oz. = the weight of 1 cu. ft. of cork.
4

25. How many oz. of iron will a cubic foot of cork float in

water ?

1000 oz. = weight of a cubic foot of water.
.240 = ppoc. grav. of cork.

240 = weight of a cubic foot of cork.
1000 oz. — 240 oz. = 760 oz., the buoyant force of a cubic foot.

26. What is the specific gravity of a body whose weight in
air is 30 grs. and in water 20 grs. ?

30 grs. — 20 grs. = 10 grs.

30 grs. -«- 10 grs. = 3.
The body is three times as heavy as water.

27. Which is heavier, a pail of fresh water or one of salt-
water?

A pail of salt-water is as much heavier than one of fresh-
water as the weight of the salt added to make the brine.

28 ANSWERS TO PRACTICAL

28. The weights of a piece of syenite -rock in air and tn
water were 3941.8 grs. and 2607. 5 grs. Find its spec. grav.

• -Ans. 2.954.

29. A specimen of green sapphire from Siam weighed in
02> 21.45 grs., and in water 16.33 Srs- Required its spec,
grav. — Ans. 4.189.

30. A specimen of granite weighs in air 534.8 grs., and tn
water 334.6 grs. What is the spec. grav. ? — Ans. 2.671.

3 1 . What is the bulk of a ton of iron ?

1000 oz. = weight of 1 en. ft. of water.
7.8 = spec. grav. of iron.

7800 oz. = weight of a cu. ft. of iron.
82,000 oz. (a ton of iron) -H 7,800 (weight of a cu. ft.) = 44/»»

A ton of gold?

1,000 oz. = weight of a cu. ft. of water.
19.34 = spec. grav. of gold.

19,340 oz.* = weight of a cu. ft. of gold.
32,000 oz.* -H 19,340 oz. = 1.6, the no. of cu. ft.

A ton of copper?

1000 oz. x 8.9 = 8900 oz.
32,000 oz. -*• 8900 oz. = 3.6 (nearly) the no. of cu. ft.

32. What is the weight of a cube of gold 4 feet on each

side ?

43 = 64, the no. of cu. ft.
19,340 oz.* (no. of oz. in 1 cu. ft.) x 64 = 77,360 Ibs.

33. A cistern is 12 ft. long, 6ft. wide, and 10 ft. deep
When full of water, what is the pressure on each side ?

On one side, 12 x 10 x 5 x 1000 oz. = 600,000 oz. = 37,500 Ibs.
On one end, 6 x 10 x 5 x 1000 oz. = 300,000 oz. = 18.750 Ibs.

34. Why does a dead fish always float on its back ?

It has its swimming bladder located just under the spine;
and this is the lightest part of its body, and, of course, comes
to the top as soon as the fish dies.

* In these solutions the student should notice that avoirdupois weight is used
in weighing the gol.l. To be exact, 1,000 oz., the weight of a cu. ft. of water,
should be reduced to Troy weight, and the Ib. gold taken as 12 oz. Troy, when
the ans. would be about 1.36 cu. ft.

IN NATURAL PHILOSOPHY. 29

36. A vessel holds 10 Ibs. of water: how much n.trcury
•would it contain ?

Mercury is 13.5 times heavier than water. Hence the vessel would contain
10 Ibs. x 13.5 = 135 Ibs. of mercury.

37. A stone weighs 70 Ibs. in air and 50 in water. What
is its bulk ?

70 — 50 = 20. 20 x 15 oz. = 320 oz., the weight of water displaced.
320 oz. is %£ of a cu. ft.

38. A hollow ball of iron weighs 10 Ibs. : what must be its
bulk, to float in water?

10 Ibs. = 160 oz. As a cubic ft. of water weighs 1,000 oz., the ball must dis-
place such a part of a ca. ft. of water as 1,000 oz. is contained times in 160 oz
which is .16 en. ft.

HYDRAULICS.

521. i. How much more water can be drawn from a faucet
, than from one 4 feet below the surface of the water in a
cistern ?

y = 2 Vffd ; hence v = 2 V716 x 8 = 2S.6.
v = 2 N/16x4 = 16.

Hence 6.6 cu. ft. more would flow from one than from the
other in each second.

•2. How much water would be discharged per second from
a short pipe having a diameter of 4 inches and a depth of 48
feet below the surface of the water ?

42=16. IP. x .7854=12.57 sq. inches=.087 sq. ft. (area of the tube).

v = &Sgd = 2^16^48 = 55.4

.087 x 55.4 = 4.8 cu. ft.

3. When we pour molasses frojn a jug, why is the stream so
much larger near the nozzle than at some distance from it?

Because, according to the law of falling bodies, the further
the molasses falls the faster it falls. The stream, therefore,
becomes smaller as it moves more swiftly, until, at last, it
breaks up into drops.

3O ANSWERS TO PRACTICAL QUESTIONS

4. Ought a faucet to extend into a barrel beyona the staves *
No ; because cross currents would be produced, which would

interfere with the free passage of the liquid.

5. What would be the effect if both the openings in one of
the arms in Barker's Mill were on the same side ?

It would cease revolving. The pressure in each direction
would then be equal, and the arms would balance.

PNEUMATICS.

14§. i. Why must we make two openings in a barrel of
fider when we tap it ?

One to let out the cider, and one to admit the air.

2. What is the weight of 10 cubic feet of air?

100 cu. in. weigh 31 grs». ; hence 10 cu. ft. will weigh 31 grs. x 172.8 = .7652
Ibs. avoirdupois.

3. What is the pressure of the air on one square rod of land?

272»/4 x 144 x 15 Ibs. = 588,060 Ibs.

4. What is the pressure on a pair of Magdeburg hemispheres
4 in. in diameter, when the air is entirely exhausted ?

3.1416 x 4a x 15 IbP. = 753.9 Ibs.

5. How high a column of water can the air sustain when
the barometric column stands at 28 in. ?

28 in. x l3'/a = 31 Vu feet.

6. If we should add a pressure of two atmospheres, what
would be the bulk of 100 cu. in. of common air?

The pressure is trebled, and according to Mariotte's law, the volume will
be reduced in the same proportion ; hence it will be 100 cu. in. -s- 3 = 331/?
cu. in.

7. If, while the water is running through the siphon, we
quickly lift the long arm, what will be the. effect on the water in
the siphon ?

It will all run back through the short arm into the vessel.

8. If we lift the entire siphon f

The water will all run out the long arm. The reason of this

IN NATURAL PHILOSOPHY. 31

difference is, that when we lift the long arm we make it in
effect the short arm, and the other arm the long one.

8. When the mercury stands at 29^ in. in the barometer,
how high above the surface of the water can we place the lower
pump-valve ?

In theory, 29^ in. X 13^ = 398^ in.; in practice, the distance
is much less than this.

9. Why cannot we raise water, by means of a siphon, to
a higher level?

There is no power in a siphon ; it is only a way of guiding
the flow of water to a lower level.

10. If the air in the chamber of a fire-engine be condensed
to fe its former bulk, what will be the pressure due to the ex-
pansive force of the air on every square inch ? — Ans. 240 Ibs.

1 1 . What causes the bubbles to rise to the surface, when we
put a lump of loaf-sugar in hot tea ?

The bubbles of air contained in the pores of the sugar rise
because they are lighter than the water.

12. To what height can a balloon ascend?

Until its specific gravity is the same as that of the air in
which it floats.

— What weight can it lift?

A weight equal to the difference between its own weight and
that of the air it displaces.

13. Why is the air lighter in foul and heavier in fair
weather ?

This question is answered in the Philosophy. Another
reason may be, that the upward currents of air partly remove
the pressure in foul weather.

14. When smoke ascends in a straight line, is it a proof of
the rarity or density of the air?

Of its density, because it shows that the smoke is much
lighter than the air, and so rises immediately to the top.

it,. Why do we not feel the heavy pressure of the air on out
bodies?

32 ANSWERS TO PRACTICAL QUESTIONS

Because it is equally distributed within and without our
bodies. The pressure on a person of ordinary size is about 16
tons.

1 6. Is a bottle empty when filled with air?
No ; because we must empty the air out before we can fill
the bottle with anything else.

1 8. How does the variation in the pressiire of the air affect
those who ascend lofty mountains?

The outward pressure is there partly removed, and the
inner pressure remaining the same, the blood is often forced
through the ears, nostrils, etc. When one descends into a
deep mine the conditions are reversed : the outer pressure be-
comes in excess of the inner; severe pain is felt in the ear-
drum, and ringing noises in the head become almost intoler-
able. These, however, disappear after a time, where the
equilibrium between the internal and external pressure is
restored. It is said that Humboldt ascended where the mer-
curial column fell to 14 inches, and descended in a diving-bell
where it rose to 45 inches — thus making a variation of 3 1 inches,
or a difference of 31,000 Ibs. pressure on his body.

— If the atmosphere in a diving-bell were of the same density
as that at the surface of the earth, how deep in the water
would it be necessary to sink the bell in order to reduce the
volume of the air one-half, or, hi other words, for the bell to
half fill with water? — Ans. 34 feet.

How 'near would the bell be filled at a depth of 1,020
feet. — Ans. 29/3o.

If the bell were then raised, would the water stay in till it
reached the siirface f

The elasticity of the air would cause it to gradually expand
and drive out the water as it rose.

ACOUSTICS.

1§4. i. Why cannot the rear of a long column of soldiers
keep time fo the music ?

TN NA TURAL PHIL OSOPHY. ' 3 3

Because it takes time for the sound-wave to pass down the
column, and hence those in the rear do not hear the music as
soon as those in front.

2. Three minutes elapse between the flash and the report of a
thunderbolt : how far distant is it ?

If the air is at the freezing point, the, distance is
1090 ft. x 60 x 3 = 196,200 ft.

3. Five seconds expire between the flash and report of a gun :
what is the distance ?

1090ft.x5 = 5450ft

4. Suppose a speaking-tube should connect two villages 10
miles apart. How long would it take a sound to pass that
distance ?

52,800 ft. -f- 1090 ft. = 48.4 (sec.)

5. The report of a pistol-shot was returned to the ear from
the face of a cliff in 4 seconds. How far was it?

1090 ft. x a = 2180 ft.

6. What is the cause of the difference in the voice of man
and woman ?

It may be a difference in the length of the vocal chords, or
in the power of lengthening and shortening them; but it is not
yet fully understood. The difference between a bass and
tenor, as between a contralto and soprano voice, is probably
that of quality only, like that between different kinds of musical
instruments.

7. What is the number of vibrations per second necessary to
produce the fifth tone of the scale of C ?

(p. 176.) Ct = 128 vibrations. G of that scale = 192 vibrations per second.

8. What is the length of each sound-wave in that tone when
the temperature is zero ?

1090 ft.— 32 ft. =1058 ft, 1058 ft. -t- 192=5 ft. 6 -I- in. (the length of each vibration).

9. What is the number of vibrations in the fourth fane above
middle C (CJ ?

f^n

C8 = 256 vibrations . fii _ (the proportionate no. for the 5th of tho scale).

256 x — = 384 (the number of vibrations per second).

2*

34 ANSWERS TO PRACTICAL QUESTIONS

10. A meteor of Nov. 13, 1868, is said to have exploded al
a height oj '60 miles : what time would have been necessary for
its sound to reach the earth ?

5280 ft. x 60 = 310,800 ft.
316,800 ft. -*- 1090 ft. = 290 (sec.) = 4 min. 50 gee.

11. A stone was let*fall into a well, and in 4 seconds was
heard to strike the bottom. How deep was the well?

(See p. 48.) d = 16 x f». d = 16 x 42 = 256 ft.

1 2. What lime would it require for a sound to travel 5 miles
in tke still water of a lake ?

6280 ft. x 5 = 26,400 ft.
26,400 ft. -i- 4700 ft. = 5.0 (sec.)

13. How much louder will be the report of a gun to an
observer at a distance of 20 rods than to one at half a mile?

160 rod? are 8 times 20 rods. The intensity of the sound is inversely as the
square of the distance = 1/64. Hence the sound is 64 times louder to the
observer at 20 rods that to the one at half a mile.

14. Does sound travel faster at the foot or at the top of a
mountain ?

The density and elasticity of the air vary in the same pro-
portion ; hence if the temperature were the same on the top of
a mountain that it is at the foot, the velocity of sound would
be the same, but as it is always colder, the velocity is less.

15. Why is an echo weaker than the original sound?
Because the intensity of the sound-wave is weakened at each

reflection.

1 6. Why is it so fatiguing to talk through a speaking-
trumpet ?

Because so much more air must be set in motion by the
vocal chords. The column of air in the resonant cavity of
the throat is re-enforced by all the air in the trumpet.

• -When we hear a goblet or a wine-glass struck with the
blade of a knife, we can distinguish three sounds, the funda-
mental and two harmonics. *

* Is not the ear the most perfect sense ? A needlewoman will distinguish by
the pound, whether it is silk or cotton that is torn. Blind people recognise

IN NATURAL PHILOSOPHY. 35

OPTICS.

224. i . Why is a secondary bow fainter than the primary /
The primary is produced by one reflection and two refrac-
tions; the secondary, by two reflections and two refractions.
The additional reflection weakens the ray.

Why are the colors reversed?

We can understand this by looking at Fig. 159. In one
bow we see that the rays enter the drops at the top, and are
refracted at the bottom to the eye ; in the other, that the rays
enter at the bottom, and are refracted at the top to the eye.

2. Why can we not see around a house or through a bent tube f
The rays of light move in straight lines.

3. What color would a painter use if he wished to represent
an opening into a dark cellar f

Black.

4.. Is black a color?
No ; it is the absence of color.
Is white f

Yes ; it is the presence of all color — i. e., it is the compound
effect produced on the brain by seven different impressions.

5. By holding an object rearer a light, will it increase or
diminish the size of the shadow ?

It will increase it, because more rays are intercepted.
7. Where do w? see a rainbow in the morning?
In the west.

the age of persons by their voices. An architect, comparing the length o*
two lines separated from each other, if he estimate within the 30th part, we
deem very accurate ; but a musician would not be considered very precise
who only estimated within a quarter of a note. (128-*-30 = 4, nearly.) In a
large orchestra, the leader will distinguish each note of each instrument. We
recognize an old-time friend by the sound of his voice, when the other senses
utterly fail to recall him. The musician carries in his ear the idea of the
musical key and every tune in the scale, though he is constantly hearing a
multitude of sounds. A tune once learned will be remembered when the
words of the song are forgotten. Prof. Pepper tells us that he tuned a fork
which corresponded to 64,000 vibrations per second. The first harmonic ia
produced by one-half the whole cord, the second by one-third, «fec.

36 ANSWERS TO PRACTICAL

8. Can any two spectators see the same rainbow ?

They cannot, because no two persons can be at the right
angle to get the same color from a drop.

9. Why, when the drops of water are falling through the
air, does the bow appear stationary ?

Because the drops succeed each other so rapidly that they
keep a constant impression on the retina.

10. Why can a cat see in the night?

Because the pupils of its eyes are larger, and so admit more
light.

Why cannot an owl see in daylight ?

The pupils of its eyes are large enough to admit of cleai
vision in the night, but they cannot be contracted, and so in
daylight the owl becomes dazzled with the excess of light
received.

12. Why are we blinded when we pass quickly from a dark
into a brilliantly lighted room ?

The pupils of our eyes admit too much light, but they soon
contract to the proper dimensions, and we can then see dis-
tinctly. When we pass out from a lighted room into the dark
street, the conditions are reversed.

* 13. If the light on a distant planet is only^ that which we
receive, how does its distance from the sun compare with ours ?
As the light is inversely as the square of the distance, the
distance is 1/100= 10 times greater than ours.

14. If when I sit 6 feet from a candle I receive a certain
amount of light, how much will I diminish it if I sit back 6
feet further ?

As my distance from the light is doubled, the light is in-
versely as 22, or only \ as bright.

15. Why do drops of rain, in falling, appear like liquid
threads ?

The impression the drop makes on the retina remains until
the drop reaches the ground.

'*>. Why does a to~~'d turn darker when ivetf

IN NATURAL PHILOSOPHY. 37

More of the light is transmitted, and less reflected. We see
this illustrated in greasing a bit of paper. It becomes semi-
transparent because more light passes through it, but looks
darker itself because less light is reflected to the eye.

1 7. Does color exist in the object or in the mind of the ob-
server ?

In the mind. Color in the object can be only a peculiar
property whereby a body absorbs some colors, and reflects or
transmits others.

1 8. Why is lather opaque, while air and a solution of soap
are each transparent ?

By repeated reflections and refractions in passing through
the unhomogeneous mass of lather, the rays are weakened.
The principle is the same as that of deadening floors with tan-
bark. (Phil., p. 161.)

19. Why does it whiten molasses candy to pull it?

Water is given up both in cooking and pulling. This causes
more light to be reflected (Q. 16), while the crystals formed, es-
pecially on the surface, hide the impurities.

20. Why does plastering become lighter in color as it dries ?
Because, as the water evaporates, the mortar transmits less

light, and reflects more light to the eye. .

i 1 . Why does a photographer use a kerosene oil-lamp in the
"dark-ro'om?"

Kerosene oil-flame emits only heat and color, but no actinic
rays. Some ' ' dark-rooms" are lighted with yellow glass windows.

22. Is the common division of colors into "cold" and
"warm" verified in philosophy?

Yes ; red contains more heat than violet.

23. Why is the image on the camera, Fig. 167, inverted?
The rays cross each other at the focus of the double convex

lens

24. Why is the second image seen in the mirror, Fig. 134,
brighter than the firct?

The first is formed by reflection from the glass, and the
second from the mercury. As the latter is a better reflector,

38 ANSWERS TO PRACTICAL QUESTIONS

the second image will be brighter. Each image after that will
be weakened by the repeated reflection.

27. Which can be heard at the greater distance, noise or
music f

Other things being equal, music will penetrate much further
than noise. Boatmen call to each other, at a distance, in a
musical tone. A band is heard above the noise of the rabble.
It seems to be a wise arrangement of Providence that all harsh,
discordant noises should perish as soon as possible, and only
harmonious ones survive.

28. Why are some bodies brilliant, and others dull?

Some reflect the light better than others. A piece of stone
coal lying in the sun's rays will shine so brilliantly that one
will cease to see the coal at all, and will judge it to be a bright
metal.

29. Why can a carpenter looking along the edge of a board
tell whether it is straight ?

If the edge is straight, the light will be reflected uniformly
to his eye from the whole length. Any uneven places will
make dark and light spots.

30. Why can we not see out of the window after we have
lighted the lamp in the evening f

The glass reflects the light of the lamp back to our eyes,
and they adapt themselves to the increased amount.

3 1 . Why does a ground-glass globe soften the light ?
It scatters the rays.

32. Why can we not see through ground-glass or painted
windows ?

They transmit the light irregularly to the eye, and not
uniformly, like a transparent body.

33. Why does the moon's surface appear flat ?

Because it is so distant that the eye cannot detect the dif-
ference between the distance of the centre and the circumfer
ence.

IN NATURAL PHILOSOPHY. 39

34. Why can we see further with a telescope than with the
naked eye ?

Because it furnishes us more light with which to see a dis-
tant object.

35. Why is not snow transparent, like ice?
Because it is unhomogeneous. See problem 18.

36. Are there rays in the sunbeam which we cannot see f
We cannot see the heat or the chemical rays.

37. ( i ) Make two marks on a sheet of white paper, at a
distance of about three inches from each other. Then closing
one eye and looking steadily at one mark (thoiigh we can see
both), move the paper toward the eye. A point will be
reached where the eye can perceive only one of the marks / on
coming nearer, both will be seen again.

38. (2) Prick with a pin, through a card-board, two holes
:loser together than the diameter of the pupil of the eye. Hold-
ing the card pretty near the eyes, look through these holes at
the head of a pin. There will seem to be two pin-heads.

39. (3) Press the finger on one eyeball and we shall see
objects double.

Since an impression is made on the retina of each eye, it
would seem that we ought always to see objects double. The
nerves from both eyes are so joined, however, before they
reach the brain, that this effect is avoided. If, now, we cause
the image on the retina to be made on parts of the eye which
do not correspond to each other, we shall obtain a double image.

40. Why is a rainbow in the morning a sign of foul, and
in the evening of fair weather?

In the morning it indicates a formation of clouds when the
temperature is rising, and therefore shows a determination to
moisture. In the evening it indicates a clearing away when
the temperature is falling, and hence shows a determination
to dryness.

41. Why is a red, lowering sky in the morning a sign, of
rain, and a brilliant red sky at night, of fair weather f

4O ANSWERS TO PRACTICAL QUESTIONS

42. Why does a distant light, in the night, seem like a starf

43. Why does a bright light, in the night, seem so much
nearer than it is ?

44. Why does a ray of light, passed through a small hole,
of any shape, in a card, make a round, bright spot?

45. Why are these spots crescent-shaped during an eclipse ?

46. What color predominates in artificial lights ?
Yellow.

47. Why does yellow seem white, and blue green, when seen
by artificial light ?

Because the white takes on, in the yellow rays, a yellow
hue, and the yellow added to the blue gives a green, hence
there is no white for comparison. So, also, dark blue be-
comes purple, and red has a tawny hue. Magnesium light
possesses all the colors of the spectrum, and hence all objects
.retain their natural appearance when illuminated by it.

48. Why are we not sensible of darkness when we wink ?
Because the impression of the light is retained upon the

retina during the brief interval of darkness.

HEAT.

258. i. Why will one 's hand, on a frosty morning, freeze
to a metallic door-knob sooner than to one of porcelain ?

Because the metal is a better conductor of heat than the
porcelain, and hence conducts the heat from the hand faster.

2. Why does a piece of bread toasting ctirl up on the side
toward the fire ?

The water being expelled from the pores on that side causes
the bread to shrink.

3. Why do double windows protect from the cold?

The non-conducting air enclosed between the window-panes
keeps in the heat and keeps out the cold.

4. Why do furnace-men wear flannel shirts in summer to
keep cool, and in winter to keep warm f

IN NATURAL PHILOSOPHY. 41

In summer the non-conducting flannel keeps out the fur-
nace-heat, and in the winter keeps in the body-heat.

5. Why do we blow our hands to make them warm, and
our soup to make it cool?

Our breath is warmer than our hands, but cooler than our
soup.

6. Why does snow protect the grass ?

The air enclosed between the flakes of snow is a non-con-
ductor. No infant in its cradle is tucked in more tenderly
than the coverlet of snow about the humble grass that nestles
down for its winter's nap on the bosom of mother Earth.

7. Why does water " boil away" more rapidly on some days
than on others f

Because the atmospheric pressure varies.

8. What causes the crackling sound in a stove, when a firs-
ts lighted?

The expansion of the iron by the heat.

9. Why is the tone of a piano higher in a cold room than in
a warm one?

The steel wires lengthen in a warm room, and so lower the
tone.

10. Ought an inkstand to have a large or a small mouth ?
A small mouth, to prevent evaporation.

1 1. Why is there a space left between the ends of the rails on
a railroad track ?

To allow room for the expansion and contraction of the rails
with the changes in temperature.

12. Why is a person liable to take cold when his clothes are
damp ?

The water which evaporates from his clothes, in drying,
absorbs heat from his body.

13. What is the theory of corn-popping?

The air in the ceiis 01 trie corn expands by the heat and
bursts the outer coating of the corn.

42 ANSWERS TO PRACTICAL QUESTIONS

14. Could vacuum-pans be employed in cooking?

They could not, because the heat would not be sufficient to
cook the food.

15. Why does the air feel so chilly, in the spring, when
snow and ice are melting ?

When the ice is passing into the liquid state, it absorbs heat
from all surrounding objects.

1 6. Why, in freezing ice-cream, do we put the ice in a
wooden vessel, and the cream in a tin one ?

The non-conducting wooden vessel prevents the ice from
absorbing heat from the external air, and the conducting tin
vessel enables it to absorb the heat from the cream.

1 7. Why does the temperature generally moderate when the
snow falls ?

The vapor passing into the solid form gives off heat.

19. Why does sprinkling a floor with water cool the air?
The water turning to vapor absorbs heat.

20. How low a degree of temperature can be reached with
a mercurial thermometer ?

Nearly to the freezing point of mercury, —39° F.

21. If the temperature be 70° F., what is it C. f

70*- 32'=38°. S8-*-1.8=21.r C.
— If the temperature be 70° C., what is it F. ?
70* x 1.8=126*. 126" +32°=158* P.

22. Will dew form on an iron bridge f
Yes, because iron is a good radiator.
On a wooden brid&tt f

Not so readily, because wood is a poorer radiator.

23. Why will not corn pop when very dry ?

The pores shrink, and the corn becomes compact; only
porous, tender-celled corn will pop.

24. The interior of the earth being a melted mass, why do
we get the coldest water from a deep well?

IN NATURAL PHILOSOPHY. 43

The well extends below the influence of the sun, and not
deep enough to reach the internal heat of the earth.

25. Ought the bottom of a tea-kettle to be polished?

No, since a polished surface would reflect the heat. We
need a black, rough, sooty surface to absorb the heat rapidly.

26. Which boils the sooner, milk or water?

Milk, because it is so adhesive that the bubbles of steam
which are formed at the bottom of the dish cannot easily
escape. They therefore pile up on top of each other, and the
milk boils over readily.

27. Is it economy to keep our stoves highly polished?

The stove-blacking used is a good radiator, but the surface
should not be highly polished, as that hinders radiation.

28. If a thermometer be held in a running stream, will it
indicate the same temperature that it would in a pailful of
the same water ?

It will. For the same reason that a thermometer, in the
wind, will indicate the same temperature as in the still air.
although the former seems to us much colder.

29. Which makes the better holder, woollen or cotton f
Woollen, because it is so poor a conductor of heat.

30. Which will give out the more heat, a plain stove or one
with ornamental designs ?

The latter, since it has more radiating surface

3 1 . Does dew fall ?

No ; it forms directly where it is found. The vapor merely
collects on the cold surface.

32. What causes the " sweating" of a pitcher?

The vapor of the air condenses on the cold pitcher. It is
often a sign of rain, since it shows that the air is full of vapor
easily deposited.

33. Why is evaporation hastened in a vacuum f
Because the pressure of the air is removed.

44 AX8WEJSS TO PRACTICAL QUESTIONS

34. Does stirring the ground arotind plants aid in the depo-
sition of dew?

It does, since it facilitates radiation.

35. Why does the snow at the foot of a tree melt sooner than
that in the open field?

The dark-colored tree absorbs the sun's heat, and then
radiates it out in slow, dull waves, which are absorbed by the
snow.

36. Why is the opening in a chimney made to decrease in
size from bottom to top ?

Because as the heated air rises it cools and shrinks. If the
chimney did not diminish in size correspondingly, currents of
cold air would set down from the top.

37. Will tea keep hot longer in a bright or in a dull tea-pot *
In a bright one, since a polished surface retards radiation.

39. Why is one's breath visible on a cold day ?

The vapor in the breath is condensed by the cold air.

41. Why is light-colored clothing cooler in summer and
warmer in winter than dark-colored?

It does not absorb the heat of the. sun in summer, nor the
heat of the body in winter; dark- colored clothing has neither
of these desirable properties.

42. How does the heat at two feet from the fire compare
with that at four feet ?

22 : 42 : : 1 : 4.
Hence it is four times greater.

43. Why does the frost remain later in the morning upon
some objects than upon others ?

Those objects which are good absorbers of heat soon become
warm enough to melt the frost upon them : "poor absorbers
heat more slowly, and so retain the frost longer.

44. Is it economy to use green wood ?

It is not, since the sap must be changed to vapor, and watei

IN NATURAL PHILOSOPHY. 45

m turning to vapor renders latent over 900° of heat. This is,
of course, entirely lost to the consumer.

45. Why does not green wood snap ?

The pores are filled with water instead of air. The water
does not expand rapidly enough to burst off the coverings of
the cells, and so simply oozes out gradually and is vaporized.

46. Why will a piece of metal dropped into a glass or porce-
lain dish of boiling water facilitate the ebullition ?

The rougher surface of the metal aids in the formation and
disentanglement of the steam-bubbles. The bubbles cling
longer to a smooth than to a rough surface. This is one
cause of that bumping sound often noticed when liquids are
boiling in glass dishes.

47. Which can be ignited the more easily with a burning-
glass, black or white paper f

Black paper, since it is a much better absorber of heat.

48. Why does the air feel colder on a windy day ?
Because fresh portions of cold air are brought constantly in

contact with our bodies.

49. In what did the miracle of Gideon 's fleece consist ?
The hard threshing-floor was a better conductor of heat

than the porous fleece ; hence, naturally, the dew would
collect on the latter more readily than en the former. In
the miracle, the conditions remaining the same, the results
in the two cases were reversed. (Judges, vi. 37-40.)

50. Could a burning-lens be made of ice ?

Burning-lenses have been made of that material. The rays
have no heating power until the waves of ether are stopped.
They do not elevate the temperature of the medium through
which they pass.

5 1 . Why is an iceberg frequently enveloped by a fog ?
The moisture of the air is condensed upon its cold surface.

52. Would dew gather more freely on a rusty stove than on
a bright kettle?

It would, because the rusty iron surface is a good radiator.

53. Why is a clear night colder than a cloudy one f

46 ANSWERS TO PRACTICAL QUESTIONS

On a cloudy night the clouds reflect the radiated heat of the
earth back again, and thus act as a blanket to keep the earth
warm. On such a night there can be no frost or dew. On a
clear night, the heat which the earth radiates passes out freely
into space, and thus the earth cools rapidly.

• 54. Why is no dew formed on cloudy nights f
See last question.

55. Water boiled at a certain place at 200° F. : what wa*
the height above the sea f

56. On Mont Blanc boiling water is only 84° C. : what is
the height?

57. Why do we use a longer tube of mercury for a barometer
than a thermometer ?

58. Which is the hottest part of a room ?

59. Why is it hotter above a flame than at the side f

60. What is the difference between dew and rain f

6 1 . Why will ashes keep fire overnight ?

62. If a pane of glass and a similar plate of polished steel
were laid upon the ground, in the night, upon which would
the dew form most abundantly ?

The glass is a poor conductor of heat, and so would absorb
little heat from the earth, while the metal would absorb it
freely ; the glass is a better radiator than the polished metal,
and thus would become drenched with dew, while the metallic
surface would be scarcely dimmed.

63. Why is there but little dew formed in cities ?

64. Is an abundant dew a sign of rain f
It is. See question 32.

65. Is there any dew formed out at sea ?

66. Why are gardens in a valley often touched with frost,
while those on the hills escape unharrf.ed /

The cold air settles into the valley; while the warm air rises
to the hills.

IN NATURAL PHILOSOPHY. 47

67. How are hailstones formed?

There are two separate currents of air, one hot and charged
with moisture, the other cold. The former is displaced by
the latter and driven up in the atmosphere. There its vapor
is condensed at the centre of the cloud into snow, and at the
extremities into ice-cold water. In this cloud there is a whirl-
ing motion which collects the snow into little balls, each of
which is the nucleus of a hailstone. Each of these is carried,
alternately, by the whirling currents, into the snow-cloud at
the centre, and the ice-cold water outside. Both give it a
coating, one of snow-like, spongy ice, and the other of trans-
parent ice. This is done with great rapidity, until at last its
weight overcomes the violent upward motion which sustains it
in the air, and the hailstone falls to the ground. When a
hailstone is carefully examined we can see this nucleus, and
these concentric layers, like the coats of an onion. *

68. Why do we have hailstorms in summer, and not in
•winter?

The small spongy hail or sleet of winter has the same origin
as hailstones in summer, but there is not enough vapor in the
cold air to give them the size of summer hailstones.

69. Is the sweating of a pitcher a sign of rain ?
See question 32.

70. Where should ice be applied, to cool water?
At the top, because cold water falls.

71. Why is evaporation hastened in a vacuum?
Because the pressure of the air is removed.

72. Is a dusty boot hotter to the foot than a polished one ?
It is, because it is a better absorber of heat.

* The above theory is that advanced by Prof. Loomis, in his "Treatise on
Meteorology." Th > teacher will find thii work invaluable on all raeteorologi-

cal questions.

48 ANSWERS TO PRACTICAL

(Key, p. 34, Prob. n.) The method adopted in solving
this problem is merely the rough one in common use, and
gives only an approximate result. If an exact answer is de-
sired, we should take in account the time required for the sound
to reach the ear. The following method may be employed :

aj = No. sec. for stone to fall.
4— a = " " sound to reach the ear.
16x2 = (4 — a:)1090.
16a;a = 4360 — 1090a;.

From this, by completing the square, we have

a = 3.7892+ seconds.
Then the equation (2) d = i6/2 gives the depth.

d = 16(3.7892 +)2 = 229 ft. and 8.795 in.,
which is the answer exact within a small fraction.
A second method (more exact) —

d = depth of the well = 16ia.

4— i y/d = No. of sec. for sound to reach the eftZ.
(4-i v/d)l090 =4360 -

_ __ 190Q8SOC.

A N S W E B S

TO THE PRACTICAL QUESTIONS,

AND SOLUTIONS OF THE PROBLEMS,

m THE

FOURTEEN WEEKS COUKSE

IN

CHEMISTRY,

f The bold-faced figures refer to the page of the Chemistry; the others to
th* number of the Practical Questions."]

1. Is it likely that all the elements have been discovered?

It is not, since several have been found lately by means of
spectrum analysis. The ancients held that there are but four
elements — earth, water, air, and fire ; the first representing
the solid form of matter, the second the liquid, the third the
gaseous, and the fourth the force which changes matter from
one form to another. Few of the sixty-five elements are com-
mon. Those italicised, in the table on page 14, are rare.
The remarkable phenomena of allotropism would seem to in-
dicate that, perhaps, what we now consider distinct elements
nay be only allotropic states of the same element. Indeed,
it is possible to conceive that all substances. are only allotropic
forms of one universal essence. In the present state of
chemistry this view cannot be proved, and is only a specula-
t'on as to what may be discovered in the future.

2. What is the origin of the term "gas?"

This word was first used in the iyth century. Explosion^,
strange noises, and lurid flames had been seen in mines, caves,
&c, The alchemists, whose earthen vessels often exploded

2

5<D ANSWERS TO PRACTICAL QUESTIONS

with terrific violence, commenced their experiments with
prayer, and placed on their crucibles the sign of the cross —
hence the name crucible from crux (gen. crucis), a cross. All
these manifestations were supposed to be the work of invisible
spirits, to whom the name gahst or geist, a ghost or spirit,
was applied. The miners were in special danger from these
unseen adversaries, and it is said that their church service con-
tained the petition, ''From geists, good Lord, deliver us!"
The names — spirits of wine, nitre, &c., are a relic of the
superstitions of that time.

3. If the air iv ere pure O, what bodies would escape com-
bustion in a conjlagration ?

The stones, mortar, &c., which being already combined
with O and other elements, and having their chemical affinities
satisfied, are hence termed "burnt bodies."

4. Why will lime added to hard water often soften it ?
The lime will combine with the free carbonic acid absorbed

by the water. This renders the water incapable of holding in
solution as much carbonate of lime as before, which is then
precipitated, and the water thus partly softened.

5. Why will stirring a wood fire quicken the flame, but a
coal fire, will deaden it ?

Stirring a fire lets in more O, which quickens a wood fire
but reduces the temperature of a coal fire below the point of
union between O and coal. It is really based on the fact that
a higher temperature is requisite to burn coal than wood.

6. Why does blowing on a fire quicken the flame, but on a
lamp extinguishes it ?

The same principle applies as in the last question. In ad-
dition, the force of our breath often drives the flame off the
wick mechanically.

7. Why will oyster-shells placed on the grate of a coal Jire
prevent the formation of clinkers?

The lime of the shells forms a flux with the silicates con-
tained in the coal, and thus renders them more fusible.

IN CHEMISTRY. 51

8. What alkali abounds in sea-weed?
Soda.

g. What alkali abounds in land-plants ?

Potash. The former salt is a constituent of sea-water, and the
latter of rocks which decompose to form the soil.

10. How is lime-water made from oyster-shells ?

The oyster-shells, in burning, lose their CO2. This leaves the
lime uncombined ; hence it readily dissolves in water.

1 1. What other tests of lead than HS ?

KI gives a yellow precipitate, NH4S a black, and SO3 a white
one.

12. Will not lime lose its beneficial effect upon soil after a
time ?

Lime acts in various ways to improve the fertility of a soil.
It corrects its acidity, aids in the decomposition of the rocky con-
stituents, hastens the decay of the humus, and also makes the
soil more porous. It does not, however, benefit the growing
plant directly, but works up other materials in the soil. It
therefore loses its effect after a time. The Belgian farmers have

a proverb :

" Much lime and no manure
Make farm and farmer poorer."

13. What is the derivation of the term zinc ?

The name is probably derived from the Germnn zinken, signi-
fying " nails," and is applied to this metal on account of its fre-
quently forming pointed particles somewhat resembling nails,
when melted and suddenly poured into water. (Griffiths.)

14. What is the action of permanganate of potash (chameleon
mineral) as a disinfectant?

It gives up its O to oxydize the organic impurities of the water
in which they collect.

15. Do all fish die when taken out of the water?

No. Some fish have an apparatus for moistening their gills.
They can therefore crawl about in the grass, and even migrate
from one stream to another.

52 ANSWMliS TO PRACTICAL QUESTIONS

1 6. What proof have we that H is a metal?

Besides that given in the Chemistry, the " sodium amalgam"
is thought by some to be an additional proof. Heat moderate-
ly in a test-tube a little mercury with a grain or two of sodium.
The two metals will combine, forming a pasty amalgam.
When cold, pour over it a solution of sal-ammoniac. The
amalgam will immediately swell up to eight or ten times its
original bulk, retaining, however, its metallic lustre. It is
thought that H is the metal which puffs out and combines
with the mercury, since otherwise we would be compelled to
suppose that NH4 is a metallic element, instead of a com-
pound radical, as is generally believed.

17. Why does not frozen meat spoil?

The cold protects from chemical change. The bodies of
mammoths have been found in the frozen soil of Arctic regions
so perfectly preserved that the dogs ate the flesh. How long
the animals had been there we cannot tell, but certainly for
ages. In 1861 the mangled remains of three guides were
found at the foot of the Glacier de Boissons, in Switzerland.
They had been lost in an avalanche on the grand plateau of
Mont Blanc, forty-one years before.

1 8. Give an illustration of the effect of food on the disposi-
tion of animals.

Bears which feed on acorns are mild and tractable, while
those of the polar regions, which live on flesh alone, are fierce
and ungovernable.

19. Compare the chemical action of the animal with that of
the plant.

The animal lives on organized materials, taking up O and
evolving CO2, and other oxydized products. The plant lives
on unorganized materials, CO2, HO, NH,, and salts, organ-
izing them and evolving O. The function of the animal is
oxydation; that of the plant, reduction. The food of the
plant serves merely to increase its bulk ; that of the animal is
employed to replace the material worn out by the active opera-
tions of life. The animal obtains the energy necessary for its

L\ CHEMISTRY. 53

existence from the oxydation of its own body; the plant ob-
tains the energy necessary for the organization of its food di
rectly from the sun.

20. Show how man is made mainly of condensed air.

Science has demonstrated that man is formed of condensed
air ; that he lives on condensed as well as uncondensed air,
and clothes himself in condensed air, that he prepares his
food by means of condensed air, and by means of the same
-agent moves the heaviest weights with the velocity of the
wind. But the strangest part of the matter is, that thou-
sands of these tabernacles formed of condensed air, and going
on two legs, occasionally, and on account of the production
and supply of these forms of condensed air which they re-
quire for food and clothing, or on account of their honor and
power, destroy each other in pitched battles by means of con-
densed air. — LlEBlG.

19. i. In making O from chlorate of potash (KO.CIOJ,
how much can be obtained from two pounds of the salt?

6O=48=equivalent of constituent.
KO.C1O6=122.5= " " compound.

a:=weight of constituent.
21bs.= " " compound.
60 : KO.ClOfi : : x : 2 Ibs.
48 : 122.5 : : x : 2 Iba.

2. In making H, sine is used. How much sulphate of zitic
will be formed from 2. Ibs. of the metal*

Zn = 32.5 = equivalent of the constituent.
ZnO.SO3-f7HO = 143.6= " " compound.

2 Ibs. = weight of the constituent.
x= " " compound.

Zn : (ZnO.SO3+7HO) :: 2 Ibs. : x.

32.5 : 143.6 : : 2 Ib. : x.
a;=8.8 Ibs. (white vitriol, sulp. zinc).

3. How much SO3 will be required to make 50 Ibs. sulphate
of iron (FeO.SO^-jHO) ?

54 ANSWERS TO PRACTICAL QUESTIONS

SO3 = 40 = equivalent of the constituent.
FcO.SO,+7HO = 139 = t4 " compound.

x = weight of the constituent.
50 Ibs. = " *' compound.
SOS : (FeO.SO3-i-7HO) :: x : 50 Ibs.
40 : 139 : : x : 50 Ibs.
x = 14 /'/gibs. (SO 3.)

4. The equivalent of the chloride of sodium -(salt) is 58. 5.
In 10 Ibs. there are 6t rr Ibs. of chlorine : what is the equiva*
lent of Cl?

x = equivalent of the given constituent.
58.5= " " " compound.

6 if 7 Ibs. = weight of the given constituent-
10 Ibs. = " " " compound.
x : 58.5 : : 6 -, f T Ibs. : 10 Ibs.
x = 35.5.

5. In 20 grains of bromide of potassium there are 6^9
grains of potassium : the equivalent of potassium being 39,
what is the equivalent of the bromide of potassium ?

89 = equivalent of the given constituent.
x= " " " compound.

6 ~ffe gre« = weight of the given constituent.
SOgre. = »* " " compound.
39 : x : : 6 -^ grs. : 20 grs.
a? =119.

6. In 14 Ibs. of iron-rust (Fe^O^ how much O?

3O = 24 = equivalent of the given constituent.
PeaO8 = 80 = " " " compound.

* = weight of the given constituent.
14 Ibs. = " " " compound.
24 : 80 : : x : 14 Ibs.
a; = 4 Vilbs. (O).

7. In 20 Ibs. of glass (NaO.SiO^ + CaO.SiOJ how many
tt>s. of sand (SiOJ ?

2 SiO2 = <!0 = equivalent of the given constituent.
(NaO.SiO2 + CaO.SiO2) = 119= " " " coapound.

x = weight of the given constituent.
80 Ibs. = *' '• " compound.
60: 119: : x: 20 Ibs.
X = 10 ^ Ibs. (SiOj)

IN CHEMISTRY. 55

8. In a 25 Ib. sack of salt (NaCl) how many Ibs. of the
metal sodium ?

Na = 23 = equivalent of the constituent.
NaCl = 58.5=. " " compound.

x = weight of the constituent.
25 Ibs. = " " compound.
23 : 58.5 : : x : 25 Ibs.
a; = 9-^- Ibs. (Na).

229. 5. What weight of O is contained in 60 grs. of
KO.CIOJ

,O = 48 = equivalent of constituent.
KO.C106 = 122Va = " " compound.

x = weight of constituent.
60 grs. = " " compound.
48 : 122V3 : : x : 60 grs.
X = 23 |f grs.(O).

6. How much KCl will be formed in preparing 80 grs. of Of
First find how much KO.C1O6 will be required to make 80

grs. «f O, and then subtract the 80 grs. of O from the amount,
and the remainder will be the KCl. The constituent and
compound are the same as in the last problem.

48 : 122 »/a : : 80 grs. : x

x = 204.16 grs.
204.16 grs. — 80 grs. = 124.16 grs. (KCl).

7. How much H can be made from 10 Ibs. of Zn f

First find how much ZnO 10 Ibs. of Zn will form ; second,
subtract the 10 Ibs. of Zn, and the remainder is the O which
came from the water. This O formed f of the water, and
the remaining £ is the H set free.

Zn = 32.5 = equivalent of the constituent.
ZnO = 40.5 = " " compound.

10 Ibs. = weight of the constituent.
x= " " compound.

35.5 : 40.5 : : 10 Ibs. : x.

OS ~ 12.461 Ibs. (ZnO). 12.461 Ibs. ZnO — 10 Ibs. Zn = 2.461 'bs. (O).
2.461 Ibs. H- 8 = .307 Ibs. (H).

8. How much H can be made from 50 Ibs. of water?

56 AJfSWJSRS TO PRACTICAL QUESTIONS

H = 1 = equivalent of given constituent.
HO = 9 = . " " compound.

x = weight of given constituent.
50 Ibs. = " " compound.

1 : 9 : : x : 50 Ibs.
aj = 5»/9 Ibs. (H).

More simply, i of water is H ; hence
50 Ibs. + 9 = 5 »/9 Ibs. (H).

9. How much saltpetre will be required to make 18 lot,
of aquafortis ?

NO5 = 54 = equivalent of given constituent.
KO.NOB = 101 = " " compound.

18 Ibs. = weight of given constituent.
x = " " compound.

54 : 101 : : 18 Ibs. : x.
x = 33 V8 Ibs. (saltpetre).

10. How much oil of vitriol will be required to decompose 6
Ibs. of saltpetre ?

First find how much KO in 6 Ibs. of KO.NO6, next how
much KO.SO, that amount of KO will make, and lastly sub-
tract the KO from the KO. SO3, and the remainder will be the
SO,. In both cases we neglect the HO combined in the salts
and the acid.

KO : KO.NO5 : : x : 6 Ibs.

47 : 101 : : x : 6 Ibs.

'x = 2.79 Ibs. (KO).

KO : KO.S03 : : 2.79 Ibs : x.

47 : 87 : : 2.79 Ibs. : x.

x = 5.16 Ibs. (KO.SO8).

6.16 IDS. (KO. S08) — 2.79 Ibs. (KO) = 2.37 Ibs. (SO8).

II. How much HO will be decomposed by one drachm of
K, and how much KO will be formed?

First find how much KO I dr. of K will form, then sub-
tract from the KO the drachm of K, and the remainder is the
0, which must be 5 of the water from which it is obtained.

IN CHEMISTRY. 57

K : KO : : 1 dr. : x.

39 : 47 : : 1 dr. : x.
x = Igg drs. (KO).

1^% drs. — 1 dr. = fy dr., the amount of O.
The HO is 9/e of 8/3» dr. = Vis dr. (HO). 9

12. What weight of nitrous oxyd will be formed from the
decomposition of 6 oz. of nitrate of ammonia ?

2 NO : NH4O.N06 : : x : 6 oz.
aj = 38/j0oz. (NO).

13. How much sal-ammoniac would be required to make 2
Ibs. of NH^ ?

NH, : NH4C1 : : 2 Ibs. : x.

17 : 53.5 : : 2 Ibs. : x.
jc = 6Vi7 Ibs. (sal-ammoniac).

14. How much CO* will be formed in the combustion of 30
grs. of CO f

CO : C0a : : 30 grs. : x.
14 : 22 : : 30 grs. : x.
a = 47V7grs.(COa).

15. What weight of carbonate of soda (sal-soda) would be
required to evolve 12 Ibs. of CO^f

CO, : NaO.COa : : 12 Ibs. : x.

22 : 53 : : 12 Ibs. : x.
X = 28 'Vii Ibs. (NaO.CO,).

1 6. What weight of bicarbonate of soda (Na
"soda") would evolve 12 Ibs. of CO9 ?

2COa : Na0.2CO3 : : 12 Ibs. : x.

44 : 75 : : 12 Ibs. : x.
x = 20 Vu Ibs. (" soda").

17. What weight of C is there in a ton of CO9 f

G : CO3 : : x : 2000 Ibs.
6 : 22 : : x : 2000 Ibs.
»=545Vii Ibs. (C).

1 8. How much O is consumed in burning a ton of C?

3*

58 ANSWERS TO PRACTICAL QUESTIONS

C : C0a : : 2000 lbs. : x.

6:2-2:: 2000 Ibs. : x

X = 7333 V3 lbs. (COa).

7333 1 /s — 2000 lbs. = 5333 Vs lbs- (O)«

More simply: —

C : 2O : : 2000 lbs. : a:.

19. In burning a charge of 10 /&?. #/" gunpowder, find thi
weight of the several products formed.

(See page 107.) (1.) KS: (KO.NO3 + S+3C) :: x : 10 Ibs.
55 : 135 : : x : 10 lbs.
a; = 4 VST H». (KS).

(2.) N : (KO.NO6 + S+3C) :: x : 10 llw.
14 : 135 : : x : 10 lbs.

x = 1 VST Ibs. (N).

(3.) 3C03 : (KO.N06 + S+3C) : : x : 10 lbs.
66 : 135 : : x : 10 lbs.

* 20. Ff%zl weight of common salt would be required to fonn
25 /fo. of muriatic acid (HCl ) ?

Cl : HCl : : a; : 25 lbs.
35.5 : 36.5 : : x : 25 Ibs.

a; = 24.3 Ibs. (Cl).
Cl : NaCl : : 24.3 lbs. : x.
85.5 : 58.5 : : 24.3 Ibs. : x.
x = 40.044 Ibs. (NaCl).

21. HCl of a specific gravity 0/1.2 contains about 40 per
cent, of the acid. This is very strong commercial acid. What
•weight of this acid could be formed by the HCl acid gas pro-
duced in the reaction named in the preceding problem ?

If 25 lbs. = 40 per cent., then 100 per cent. = 2.5 times 25 lbs. = 62 >/s lbs-

22. What weight of hydriodic acid (HI) is formed from
a drachm of iodine ?

I : HI : : 1 dr. : x.
126.8 : 128.8 : : 1 dr. : a.
. (Hi).

IN CHEMISTRY. 59

23. What weight of Glauber salt can be formed from 100
Ibs. of oil of vitriol? *

SOS : NaO.SOg : : 100 Ibs. : x.

40 : 71 : : 100 Ibs. : x.
x = 177.5 Ibs. (NaO.S03).

24. What weight of S is there in 10 grs. of sulphide of
hydrogen ?

S : HS : : x : 10 grs.

16 : 17 : : x : 10 grs.

z = 9Vn grs. (S).

25. How much O is required to change a Ib. of SO^ to
SOJ

S02 : S03 : : 1 Ib. : x.

32 : 40 : : 1 Ib. : x.

x = 1 J/4 Ib. (SO3).

!V4lb.— llb. = V4 Ib. (O).

26. How much phosphorus in 40 Ibs. of phosphate of limet

(See page 245.) P : 3CaO.PO8 : : <B : 40 Ibs.

31 : 155 : : x : 40 Ibs.
x = 8 Ibs. (P).

27. How much P in 40 Ibs. of the superphosphate of lime ?

P : CaO.PO5 : : x : 40 Ibs.
31 : 99 : : x : 40 Ibs.
x = 12 "/•• Ibs. (P).

28. How much phosphate of lime will an oz. of P make ?

P : 3CaO.P06 :: loz. : x.
31 : 155 : : 1 oz. : x.
x = 5 oz. (3CaO.PO6).

29. How many Ibs. of HO in 186 Ibs. of SO^HO f

8HO : S03.3HO : : x : 186 Ibs.
27 : 67 : : x : 186 Ibs.
a; = 74«V67 Ibs. (HO).

* In this, as in the other problems, the HO contained in the acid and In
the salt is neglected, since it is a variable quantity, and the examples are
merely for practice.

60 ANSWERS TO PRACTICAL QUESTIONS

30. How much CO9 is formed in the combustion of I ton

of C?

C : C03 : : 2000 Ibs. : x.
C : 22 : : 2000 Ibs. : x.
x = 7333 Vs Ibs. (COa).

31. What weight of S is there in a ton of iron pyrites f

2S : FeS3 : : x : 2000 Iba.
32 : 60 : : x : 2000 Ibs.

32. What weight of copperas could be made from 500 Ibs.
of iron pyrites ?

In forming FeO.SO, from FeSa only one atom of S is re-
quired ; hence the 500 Ibs. of iron pyrites really contain but
366 Vs Ibs. of FeS, which will, at a single reaction, form cop-
peras ; by oxydation from the air, the remaining atom of S
would doubtless be used afterward. The problem might be
solved as well, perhaps, by taking either the Fe or the S alone
as the constituent.

FeS : (FeO.S08+7HO) :: 366 a/s Ibs. (FeS) : x.

44 : 139 :: 366 2/3 Ibs. : x.
35=1158.3 Ibs. (FeO.SO3 + 7HO).

33. What weight of H is there in a pound of heavy car*

buretted hydrogen ?

4H : C4H< : : x : 1 lb.

4 : 28 : : x : : 1 lb.

a: = V7lb. (H).

34. How miich O would be required to oxydize the metallic
»opper which could be reduced from its oxyd by passing over
it, when white-hot, 20 grs. of H gas?

The same amount of O would be required to oxydize the
copper that was taken from it when it was reduced from its
oxyd. The H passing over it when white-hot takes out its O
and forms HO. H is always £ of the HO. The H = 20 grs.;
hence the HO =9 times 20 grs. = 180 grs. 180 grs. (HO)
— 20 grs. (H) = 1 60 grs. (O).

35. How much O would be required to oxydize the metallic
iron which could be reduced in the same manner by 10 grs. of
H %as ?

IN CHEMISTRY. *>I

Following the same reasoning as in the last problem, we
have

H = 10 grs. ; hence the HO = 9 times 10 grs. = 90 grs.
90 grs. (HO) — 10 grs. (H) = 80 grs. (O).

}6. What weight of N is there in 10 Ibs. of NH^.HO f

N : NH8.HO : : x : 10 Ibs.
14 : 26 : : x : 10 Ibs.
x = 5 6/i» Ibs. (N).

37. How much KO. ClOb would be required to evolve suffi-
cient O to burn the H produced by the decomposition of ?, Ibs.
of HO?

f of HO is O ; hence i Ibs. of HO will produce, when de-
composed, i$ Ibs. O. The problem is, then, how much
KO.C1O, would be required to furnish i$ Ibs. O ?

60 : KO.C105 : 1.77 Ibs. : x.

48 : 122.5 : : 1.77 Ibs. : x.

a; = 4.51 Ibs. (KO.C1O6).

(If the common fractions are used in solving this problem,
the answer is 4!! Ibs.)

38. How much H must be burned to produce a ton of
water?

H : HO : * : 2000 Ibs.
1:9 : : x : 2000 Ibs.
a; = 2222/» Ibs. (H).

39. How much S is there in a Ib. of SO3 f

S : S0a : : x : 1 Ib.

16 : 32 : : x : 1 Ib.

x = Va H>- (S).

40. Find how much "soda" is formed from 500 Ibs. of
salt.

41. Find the amount of Glauber salt produced in the first
step, with the charge just named.

42. Find the amount of HCl produced.

43. Find how much sulphuret of sodium is formed in the
second step.

02 ANSWERS TO PRACTICAL QUESTIONS

44. Find how much sulphuret of calcium is madt

45. Find how much sulphur could be saved (if none were
lost) from the CaS.

The following reactions show the chemical changes which
take place in the various stages :

(1) NaCl + S03HO = NaO.SO, +HC1.
NaO.SO, + 2C = NaS + 2COa.
NaS + CaO.C02 = CaS+NaO.CO,.

From the (i) reaction we find how much Glauber salt will
be made from 500 Ibs. of common salt. To do this we first
find how much Na there is in 500 Ibs. NaCl; and, secondly,
how much NaO.SO3 that amount of Na will make.

Na : NaCl : : x : 500 Ibs.
23 : 58.5 : : x : 500 Ibs.
x = 196 frV Ibs. (Na).
Na : NaO.SO, : : 196 -ft\ Ibs. : «.
23 : 71 :: 196-^ : x.
Ibs. (NaO.SO,). Ans. to tostpnto.

Na : NaO.CO3 : : 196 -ftV Ibs. (Na) : *.

23 : 53 : 196 -£fo Ibs. : x.
Ibs. (NaO.C03, " Soda"). Ans. to 40th pnk

Cl : NaCl : : x : 500 Ibs.
85.5 : 58.5 : : x : 500 Ibs.

a- = 303 -f^y Ibs. (Cl).
Cl : HC1 :: 303 -^Ibs. : x.
85.5 : 36.5 :: 303^ Ibs. : *.

AM. to 4Sd pnb.

Na : NaS :: 196 -j6^ Ibs. (Na) : *.

23 : 39 :: 196-^rVlbB. : x.
s 333 Va Ibs. (NaS). Ans. to 4M proo.

888 «/• «». (NaS) — 196 -ffr Ibs. (Na) = 136 /ft- Ibs. (S). Ant. to I»ro6. 15.

S : CaS : : 136 -^f n». (s) • *•
x = 307 Vw Ibs. (CaS). Ans. to 4Mk prob

Itf CHEMISTRY. 63

46. How many Ibs. of HCl would be required to neutralize
sufficient carbonate of ammonia to form a 30 Ib. cake of sat-
ammoniac (NHV Cl) ?

First find how much Cl there is in a 30 Ib. cake of sal-
ammoniac ; second, how much HCl would contain that amount
of CL

Cl : NH4C1 : : x : 30 Ibs.
85.5 : 53.5 : : x : 30 Ibs.

x = 19.9 Ibs. (Cl).

Cl : HCl : : 19.9 Ibs. : x.

35.5 : 36.5 : : 19.9 Ibs. : x.

x = 20.4 Ibs. (HCl).

47. How much S is there in a ton of plaster (gypsum) f

S : CaO.SO, : : x : 2000 Ibs.

16 : 68 : : x : 2000 Ibs.

x = 470.58 Ibs. (S).

48. How much aluminum is there in a ton of clay t

2A1 : AlaO3.SiO3 : : x : 2000 Ibs.

27.4 : 81.4 : : x : 2000 Ibs.

» = 673.2 Ibs. (Al).

49. How much K is there in 10 Ibs. of alum f

K : (KO.S08+A12O,.3SO,+£1HO) : x : 10 Ibs.

39 : 474.4 : : x : 10 Ibs.

x = .82 Ib. (K).

50. How much white-lead (PbO.COJ could be made from
I Ib. of litharge 1

Pb : PbO : : x : 1 Ib.

103 : 111.6 : : x : 1 Ib.

« = .92 Ib. (Pb) in 1 Ib. of litharge.

Pb : PbO.C02 : : .92 Ib. : x.

103 : 133 : : .92 : x.
x = 1.1 Ib. (PbO.COa).

51. How many Ibs. of C would be required to reduce 40
tons of brown hematite (-zFe^O^HO) ?

In the intense heat of the furnace the 3 HO would be de-
composed, and so only sufficient C would be required to burn

64 ANSWERS TO PRACTICAL QUESTIONS, &c.

the 6 atoms of O in the 2FetO,. In 40 tons of brown hema-
tite there are 34.22 of the base.

6O : 2Fe2O3 : : x : 34.22 tons.

48 : 160 : : x : 34.22 tons.

x = 10.26 tons (O).

Eight-elevenths of COa is O ; if 10.26 tons is -fr, it would
require 3.84 tons of C to burn 10.26 tons of O, and thus
reduce 40 tons of hematite.

52. In 60 Ibs. of heavy spar (sulphate of baryta} how much

S is there ?

S : BaO.SO3 : : x : 60 Ibs.

16 : 116.5 : : x : 60 Ibs.

x = 8.2 Ibs. (S).

$3. How much alum can be made from i cwt. of potash f

KO : (KO.SOs -f AlaO3.3S03+24HO) : 100 Ib. : c.
47 : 474.4 :: 100 Ibs. : x.
s = 1009.3 + Ibs (alum).

ANSWERS

TO THE PRACTICAL QUESTIONS

IN THE

FOURTEEN WEEKS COURSE

IN

DESCRIPTIVE ASTRONOMY.

: . Did Tycho Brake have a telescope f
No. Galileo invented the telescope.

2. Suppose one should watch the sky, on a winter's evening,
from 6 P. M. to 6 A. M. , what portion of the celestial sphere,
•would he see ?

All that is ever seen in his latitude.

3. How do we find what proportion of the sun's heal
reaches the earth ?

Calculate the surface of a sphere whose radius is the dis-
tance of the earth from the sun, and then estimate what pro-
portion of that area the earth occupies.

4. How many real motions has the sun ?

Two. One around its axis, and one with the solar system
around (he Pleiades.

5. How many apparent motions has the sun ?

Three.. One along the ecliptic, — its yearly motion; one
through the heavens, — its daily motion ; and one N. and S.

6. How many real motions has the earth ?

Three. One on its axis ; one around the sun ; an<i i *h;rd
its "wabbling motion," which causes Precession.

66 4.NSWERS TO PRACTICAL QUESTIONS

7. Can any inferior planet have an elongation of '90° f
No. Venus recedes only 48° from the sun.

8. How do we know the heat of the surfs rays at any planet?
The intensity of the heat and light vary inversely as the

square of the distance.

9. Can yon give any other proof than that named in thf
book, of the rotundity of the earth ?

Aeronauts, when at a proper height, can distinctly see the
curving form of the earth's surface.

10. In what way is the force which acts on a spinning-top
opposite to that which produces precession (p. 125) ?

Gravity^acting on the top, tends to draw C P (Fig. 34) ./>*"»
the perpendicular. The attraction of the sun, acting on the
bulging mass of the earth's equator, tends to draw C P toward
the perpendicular.

1 1 . Why is the Tropic of Cancer placed where it is ?
Because it is the farthest place north where the sun is evei

seen directly overhead.

12. Why is the Tropic of Cancer so called?

When named, the sun was probably in that constellation at
the time of the summer solstice. Now, owing to the preces-
sion of the equinoxes, the sun is in the constellation Gemini,
and to be exact, it should be called the Tropic of Gemini. It
is still, however, the sign Cancer, as before. The same reason-
ing applies to the Tropic of Capricorn, which is now in the
constellation Sagittarius.

13. In Greenland ', at what part of the year will the mid-
night sun be seen due north ?

At the summer solstice.

14. How do we know that the moon has little if any atmos-
phere?

Because when the moon occults a star, there is no refraction
of the star's true place.

15. When is the moon seen high in the eastern sky in the
afternoon, lotig before the ?un sets ?

IN DESCRIPTIVE ASTHOXOMY 67

During the second quarter before it comes into opposition.

1 6. Why is the Ecliptic so called ?
Because eclipses always occur within it.

17. Why is it that the sun in summer shines on the north
side of some houses both at rising and setting, but in 'winter
never does f

Since at the summer solstice the sun rises and sets north of
the E. and W. points, it will rise and set on the north side of
a house which stands exactly N. and S. At the winter solstice
the sun rises and sets S. of the E. and W. points

TABLE OF THE MINOR PLANETS.

Wo.

Name.

Date of Discovery.

Discoverer.

Siderml
Revolution
(Days.)

1

Cores

1801, January 1

Piazzi .

1680

2

Pallas

1802, March 28

Olbers

1682

3

J'ino

1804 Sept 1

Harding

1596

4

Vesta

1807, March 29

Gibers?

1326

5

A^tnea

1845, December 8

Hencke

1512

6

Hebe

1847, July 1

Hencke . .

1379

7

Iris

1847 August 13

Hind

1346

8

Flora

1847, October 18

Hind

1193

9

Metis

1848, April 25

Graham . .

1346

10

Hygieia .

1849, April 12

Gasparis

2043

11

1850, May 11

Luther

1403

12

Victoria

1850, Sept. 13

Hind . ..

1303

13

Egeria. . .

1850, Nov. 2

Gasparis

1511

14

Irene

1851, May IS)

Hind

1519

15

Kunomia

1851, July 29

Gap par is

1570

16

Psyche . . .

1852, March 17

Gasparis

1828

17

Thetis

1852, April 17

Luther

1421

18

M elpomene

1852, June 24

Hind

1271

19

Fortuua

1852, August 22

Hind ... .

1393

20

Massalia. .

1852, Sept. 19

Ga-'paris

1365

21

Lutetia

1852 Nov 15

Goldschmidt

1388

22

Calliope

1852, Nov. 16

Hind

1813

23

Thalia

1852, Dec 15

Hind

1556

24

Themis

1853, April 5

Gasparis

2036

25

Phocaea

1853, April 7

Chacornac

1358

26

Proserpina . . .

1853, May 5

Luther

1580

27

Euterpe

1853, Nov 8

Hind

1313

28

Bellona

1854, March 1

Luther

1692

29

Amphi trite

1854, March 1

Marth

1492

80

Urania

1854, July 22

Hind

1329

31

Euphrosyne

1854, Sept. 1

Ferguson

2048

32

Pomona

1854, October 26

Goldschmidt '. . . . .

1521

33

Polyhymnia

1854, October 28

Chacoruac

1778

34

Circe

1855, April 6

Chacornac

1609

35

Leucothea

1855, April 19

Luther

19U3

36

Atalanta . . .

1855, October 5

Goldschmidt .

16(>4

37

Fides

1855 October 5

Luther

1569

38

Leda

1856, January 12

Chacornac

1657

39

Laetitia

1856, February 8

Chacornac

1684

40

Harmonia

1856 March 31

Goldschmidt

1247

41

Daphne . . .

1856, May 22

Goldschmidt

1C81

42

Isis

1856, May 23

Pogson . . .

1392

43

Ariadne

1857 April 15

Poison

1195

44

Nysa

1857, May 27

Goldschmidt

1379

45

Eugenia

1857, .Tune 27

Goldschmidt

1638

46

Hestia

1857, August 16

Pogrson

1470

47

Aglaia

1857 Sept 15

1788

4S

Doris

1857, Sept. 19

Goldschmidt

20^3

49

Pales

1857, Sept. 19

Goldschmidt ...

I'^S

50

1857, October 4

Ferguson

1576

51

1858 January 22

1338

52

Europa ....

1858, February 4

Goldschmidt

1993

5:i

Calypso

1858, April 4

Luther

1548

54

1858 Sept. 10

Goldschmidt

1634

55

Pandora

1858, Sept. 10

Searle

1674

TABLE OF THE MINOR PLANETS.

No.

Name.

Date of Discovery.

i
Discoverer.

Sidercul
Revolution
(Days.)

56

Melete*

1857 Sept 9

Goldschmidt

152C

57

16£'9 Sept 22

Luther

204.)

58

1860 March 24

Luther

1615

59

Elpis

lf->60 Sept 12

Chacornac

1634 •

60

Echo

18tiO, Sept. 15

Ferguson

1353 '

61

1860 Sept 9

Golaschmidt

1902

62

Erato

I860' Sept 14

Forster and Lesser.

2023 '

63
64

Ausonia

1861, February 10
1861 March 4

Gasparis

Tempel

1355 ' |
1601

65

Cybele

18(51 March 8

Teinpel

2311

66

Maia

1S61 April 9

Tut,tle

1588

67

Asia

1861, April 17

Pogson

1375

68

Leto

1861 April 29

Luther

1695

69

Igiil April 29

Schiaparelli

1893

70

71

Panopea
Niobe

186!, May 5
1861 August 13

Goldschmidt
Luther

1542
1671

72

Feronia

1861, May 29

Peters and Safford.

1245

73

Clytie

1862 April 7

Tattle

1590

74

1862' August 29

Tempel

1691

75

186/ Sept 22

Peters

1594

76

Freia

1862, October 21

d'Arrest

2080

77

FritT^a

1862, Nov. 12

Peters

1596

78

Diana

1863 March 15

Luther . . .

1554

79

1863 Sept 14

Watson

1399

80
81

Sappho

1864, May 2
1864 Sept 30

Pogson

Tempel.

1270
Ifi93

8'i

Alcmene

1864, Nov. 27

Luther

1659

83

1865 April 5<6

Gasparis

l:;8t

84

Clio

1865, August 26

Luther

1330

85

lo

1865, Sept. 19

Peters

1583

86

1866 January 4

Tietjen

1983

87

Sylvia

1866 May 16

Poijson

2384

88

Thisbe

1866, June 15

Peters

1675

89

Julia

1866 August 6

Stephan

1472

90

Antiope

1866, Ocfober 11

Luther

^031

91

^jjViiia

1866, Nov. 4

Mephan

1495

92

Uudina

1867, July 7

Peters

2086

93

Minerva .

1867, August 24

Watson

1669

94

1867 Sept. 6

Watson

2050

95

1867 Nov 23

Luther

1964

96

Jj>le

1868, February 17

Coggia

1950

97

Clotho

1868 February 17

Tempel

1592

98

lanthe

1868 April 18

Peters

1607

99
100

Dike
Hecate

1868, May 28
1868 July 11

Borelly
Watson

1892

101

1868 August 15

Watson

1508

lOv

M i riam

1868, August 22

Peters

1587

103

Hera

1868 Sept. 7

Watson

1622

104

Clymene

1868, Sept. ]3

Watson

2071

105

Artemis

1868, Sept. 16

Watson . . ..

1341

106

Dione

1868 October 10

Watson

2092

107

Camilla .

1868, Nov. 17

Pogson

108

Hecuba

1869, April 2

Luther

2104

109

Felicitas

1869 Oct 9

Peters

1615

•Goldschmidt at first believed it to be Daphne (41), but Schubert finding its perioa
different, called it Pseudo-Daphne. It was not seen from 1857 to 1861, wLea Lullw
rediscovered it, and named it Mdete.

The numerical order is that adopted by the authority of the Berlin Epfacmeru.

TABLE OF THE MINOR PLANETS.

No.

Name.

Date of Disr:overy.

Discoverer.

Log. a.*

110

Lydia.

1870 April 19

Borelly

0 4371°G

111

Ate

1870, August 14

Peters

0 413183

112

Iphigenia .

1870, Sept. 19

Peters

0 386324

113

Amalthea

1»71 March 12

Luther

0 375971

114

Cassandra

18 Tl July 23

Peters

0 427422

115

1871, August 6

Watson

0 376540

116

Sirona

1871, Sept. 8

Peters .

0 441912

117

118

Lomia
Peitho

1871, Sept. 12
1872, March 15

Borelly

Luther . . .

0.475643

0 386977

119

1872, Anril 3

Watson

0.410304

120

Lachesis

1872 April 10

Borelly

0 495810

121

1872 May 12

Watson

0 538%7

122

Gerda . ..

1872, July 31

Peters.

0 508118

123

Brunhilda

1872 July 31

Peters.

0 430151

124

Alcesto

1872 \ivu«t 23

Peters

0 419063

125

1872, Sept 11

Prosper Henry

0 48219

126

1872 Nov. 5

Paul Henry

0 386778

127

1872, Nov. 5

Prosper Henry. . .

0.44377 ;

128

1872, Nov. 25

Watson

129

Antigone.

1873 Feb 5

Peters . . .

0 457822

130

Electra

1873, Feb. 17

Peters

* Log. a i
sun as unit

logarithm of inyjr seinlaxis of orbit, taking the earth s distance from th«

SIMPLE DIRECTIONS

TO A BEGINNER

FOR

PERFORMING THE EXPERIMENTS

IN THE

FOURTEEN WEEKS COUKSE

IK

CHEMISTRY.

(OLD NOMENCLATURE.)

[The large figures refer to the paere of the Chemistry, and the small ones to
the number of the experiment. Read for additional directions, Chemistry,
pp. 235-248, and new edition, pp. 245-267.]

11. I. Put as much chlorate of potash (potassic chlorate)
as will lie upon the point of a knife-blade, and half as much
sulphur, into the mortar. Grind them slowly with the pestle
until the ingredients are thoroughly mixed and distributed
over the bottom of the mortar. Hold the mortar so that the
loose particles cannot fly into your eyes, nor the flame burn
your clothes, and then grind heavily with the pestle, when
rapid detonations will ensue. The mixture will last for days.
After use, clean out the mortar carefully for other experi-
ments. The powder can be wrapped with paper into a hard
pellet and exploded on an anvil by a sharp blow from a ham-
mer. Sometimes small bits of phosphorus are used instead
of sulphur. Great care is then necessary, as the particles of
burning phosphorus are apt to fly to some distance.

12. i. Two teaspoonfuls of common carbonate of soda and
one of tartaric acid should be dissolved separately in a wine-
glass of water. On being poured together in a larger glass,
they will violently effervesce. Use a glass large enough to

72 DIRECTIONS FOR PERFORMING

prevent any running over upon the table. Neatness in ex-
periments is essential to perfection, and often to success.

15. i. The cabbage solution is made by steeping p.urple cab-
bage leaves in water. A little lemon-juice or vinegar will turn
it to a bright red, and a little of the potash solution to a deep
green. Add a little alcohol to the red solution, to keep it
from freezing, and bottle it for use. Dissolve a little of the
dry litmus in water, filter and bottle it. These are to be used
in testing the alkalies and acids. Dissolve also a stick of the
potash in water, filter and bottle. Fill two test-tubes nearly
full of water ; color one with the cabbage and the other with
the litmus solution. Add a few drops of the potash solution
and of the sulphuric acid alternately to each. The color can
be changed at pleasure.

Take a small bit of tubing, and heating the ends in the
flame of the spirit-lamp (the greatest heat is near the tip of
the flame), seal up the opening. This will be useful to dip
into the acid or alkali, as it will remove a drop more readily
than by dropping from the bottle.

2O. Pulverize an ounce of the potassic chlorate very care-
fully; stir in it one-fourth of its weight of the black oxyd of
manganese and place the mixture in the copper retort, at-
tach the tubing and gas-bag as shown in the figure of p.
234 ; or in the Florence flask, attaching a delivery tube, as
shown in figure on p. 20. The glass tubing may be heated
in the flame of the alcohol-lamp «and bent to the desired
shape, or it can be broken into short lengths by simply start-
ing the break in the tube by a mere scratch with a three-cor-
nered file and then connecting the pieces of glass tubing with
a short bit of the small rubber tubing, as in the figure on
p. 20. The gas may be passed off from the gas-bag, or di-
rectly from the retort into the pneumatic cistern, C, across
which is placed a jhelf perforated, to permit the gas to bubble
up into the receiver, J. The pneumatic cistern may consist
of a tub of water. The bottles for collecting the gas are sunk
into the water until filled, inverted, and then lifted up on
the shelf, carefully keeping the lower edge of the bottle be-
neath the water. A large tin pan, without any shelf, may be
used as a cistern by filling the bottles full of water in a deep

EXPERIMENTS IN THE CHEMISTRY. 73

pail, and then slipping a plate underneath each one, as shown
in the second figure on p. 22, leaving enough water on the
plate to cover the edge of the bottle ; it may then be lifted
out and placed in the cistern. In the same way the bottles,
when filled with gas, may be remc ved and kept for use. Gas
may be passed from one bottle to another by inverting one
over the other beneath the water in the pneumatic cistern,
or in a large pail, when the gas will bubble up from the lower
one into the upper one.

Apply the heat to the glass retort very carefully at first,
holding the lamp in the hand and moving it around so that
the flame may strike all the lower part of the flask, and thus
expand it uniformly. Be careful also that there is no draft of
cold air to strike against the heated retort. With the cop-
per retort no care of this kind is necessary. When the gas
ceases to come off, remove the stopper or lift the end of the
tube out of the water; otherwise, as the retort cools and a
vacuum is formed, the water in the cistern will set back into
the flask, and, if of glass, will break it. An ounce of the salt
will make over six quarts of oxygen gas. When the retort is
oartly cooled, pour in some warm water to dissolve the residu-
um, which may then be poured out and the retort drained and
set away for future use. In order to test the purity of the
materials, and thus avoid any danger of an explosion, place a
little of the mixture for making oxygen in an iron spoon and
aeat it over the spirit-lamp. If the gas passes off quietly, no
langer need be apprehended.

22. i. The experiment with the candle can be performed
•nost strikingly by filling a common fruit-jar with nitrogen
vsee page 32) and another with oxygen. The covers will pre-
5erve the gases until wanted for use. The covers may then
be laid loosely on top cf the jars, and the lighted candle
passed quickly from one jar to the other. It will be ex-
anguished in one and relighted in the other. With care, it
may be passed and repassed a dozen times. This strikingly
illustrates the difference between oxygen and nitrogen. Test
the carbonic acid, in this as in all similar experiments, with
the blue litmus and the green cabbage, or a slip of blotting-
paper wet with the litmus solution. A few drops of the solu-

74 DIRECTIONS FOR PERFORMING

tion may be poured into the jar, and then the jar shaken, so
as to permit the water to absorb the gas. The candle may be
simply stuck upon the end of a bent wire, but it is much
neater to have the tinsmith fit a little cup for its reception, as
shown in the figure.

2. The worn-out watch-springs which can be obtained
gratis of any jeweller, may be easily straightened by draw-
ing them between the fingers. If the end of each spring be
heated and then pounded with a hammer on any smooth
hard surface, the temper may be thoroughly drawn and the
edge sharpened. Make a slit with a knife in the side of a
match, :nto which insert the edge of the spring. Take a
piece of zinc or tin large enough to cover the mouth of the
jar containing the oxygen, and make a hole through it with
a nail. Pass the other end of the spring through this hole,
and then through a thin cork. The spring is now ready for
burning. The metal cover will prevent the flame from roming
out of the jar and burning one's hand, and the cork will hold
the spring in its place. When the match is ignited, and then
lowered into the jar of oxygen, the spring should not reach
more than half-way to the bottom, and should be pushed
down as it burns. If a specie-jar be used, do not fill it quite
full of gas, as a little water left in the bottom will prevent the
melted globules of iron from breaking the glass.

23. I. If brimstone be used in this experiment, and it fails
to light readily, pour upon it a few drops of alcohol, and then
ignite it.

2. If you have not a deflagrating spoon to contain the phos-
phorus, one may be readily extemporized. Hollow, a small
piece of chalk and attach it to a wire, which may then be se-
cured to a metal top, as in the case of the watch-spring.
This need not be pushed down into the jar as the burning
progresses. , At the close of the experiment, test for the acid
formed in the combustion. The fumes are very disagreeable,
and should not be inhaled or allowed to escape into the room.

3. If a piece of bark charcoal be ignited, and then lowered
into a jar of oxygen, it will deflagrate with bright scintilla-
tions.

31. I. Put in an evaporating-dish a little starch; cover if

EXPERIMENTS IN TUK CHEMISTRY. 75

with water in which a few crystals of iodide of potassium have
been dissolved, and heat. Stir the liquid, to prevent lumps.
When cooked, immerse in the paste slips of blotting-paper.
Use while moist. Be careful not to heat the glass tube too
hot, lest the ether vapor may ignite. Keep the jar well rilled
with vapor by frequently shaking it. Lower into the ozone a
bit of silver-leaf moistened with water ; it will quickly crumble
into dust, the oxyd of silver.

34. i. To make the iodide of nitrogen, cover a few scales
of iodine with strong aqua ammonia. After standing for a
half-hour, pour off the liquid and place the brown sediment in
small pieces on bits of broken earthenware to dry. This will
require several hours. They may then be taken to the class-
room very carefully and exploded by a slight touch of a rod,
or even a feather.

37. I. For making NOB a special apparatus is necessary
for complete success. The Florence flask may, however, be
used, and the heat of the spirit-lamp will be sufficient. The
fumes may be caught in the evolution flask, which is kept
cool by a towel frequently wet. When the retort is partially
cooled, at the conclusion of the process, pour in a little warm
water, to dissolve the sulphate of potash, otherwise the retort
may break by the crystallization of the salt.

2. Mix equal parts of nitric acid and oil of vitriol (perhaps
a teaspoonful of each), and pour the mixture on hot finely-
powdered charcoal, or on a little oil of turpentine. It will
be oxydized with almost explosive violence. This should be
performed out of doors.

3. Bits of tin may be obtained of any tinsmith. Put them
in a tumbler and nearly cover them with the NO6. In using
copper, the apparatus shown on page 39 is excellent. The
acid may be turned in gradually through the funnel tube.
Before putting in the acid pour into the flask warm water to
cover the lower end of the funnel tube, which should nearly
reach the bottom of the flask. When a jar is filled with the
NO, it may be lifted out of the water and inverted, when the
NO4 will pass off in blood-red clouds. If the jar be left in
the cistern and one edge be lifted so as to admit a bubble of
air, red fumes will fill the jar. By standing a moment the

7 6 DIRECTIONS tfOlt PERFORMING

water will absorb the red vapor. This process can be re-
peated several times with the remaining gas.

4O. I. The finely-powdered sal-ammoniac and lime may
be mixed in an evaporating-dish. The escaping ammonia
should be tested with a glass rod or tube wet with hydrochloric
acid.

2. Heat a little aqua ammonia in the Florence flask. Col-
lect the vapor in an inverted bottle, to which is fitted a cork
and tube, with the inner extremity drawn to a fine point over
the spirit-lamp. Insert the cork, and then plunge the bottle
into a vessel of water. The water which passes in first will
absorb the gas so quickly as to make a partial vacuum, into
which the water will rush so violently as to produce a minia-
ture fountain.

42. i. In making H, the directions given on pages 236-7
should be carefully observed. For purifying the gas a solu-
tion of potash should be placed in the flask d (page 42). If a
junk bottle be used the acid should be added slowly, as the
heat generated is liable to break the bottle. Pour the water
into the flask a until the lower end of the funnel is covered,
before adding the acid. The flow of gas may be regulated
by additions of acid, as may be wanted. One part of acid to
ten or twelve of water will liberate the gas very rapidly. If
it comes off very fast, the liquid is liable to froth over. The
philosopher's lamp, page 237, is very interesting. The jet
may be a straight glass tube drawn to a fine point over the
spirit-lamp. Large glass tubes or the beaks of broken re-
torts, held over this flame, will produce the singing tones,
though not as well as the apparatus figured in the book. The
tone may be regulated by the size of the flame, z. <?. the rapid-
ity with which the gas comes off, the size of the jet as well aa
the length and size of the tubes. The H can be collected
over the pneumatic cistern, or, since it is lighter than air, in
inverted bottles. As soon as the bottles are turned right side
up the gas will escape. To measure the H and O for the
" mixed gases," a receiver, with a stop-cock on top, which
may be connected by rubber tubing with the gas-bag, is very
useful. The oxygen may be passed directly into the gas-bag,
however, as on page 234, until it is about one-third full, when

EXPERIMENTS IN THE CHEMISTRY. 77

the bag may be removed and attached to the hydrogen ap-
paratus to be filled.

5O. I. In lieu of a small crucible, fill a common tobacco-
pipe with crystals of blue vitriol, and heat them over the
lamp or in a common fire until the water of crystallization is
expelled. Alum may be rendered anhydrous in the same
manner.

56. i. Small paste-diamonds may be obtained of a jewel-
ler, to illustrate the forms of cutting the diamond.

6O. i . Place a filtering paper in the glass funnel, and in it
a couple of ounces of bone-black or finely-powdered charcoal.
Filter through it water colored with ink, litmus, or any other
impurities. In pouring the liquid into the filter hold a glass
rod against the edge of the pouring vessel, so as to direct the
stream into the funnel. The funnel may be placed in the
nozzle of a bottle, but must not fit closely. A bit of wood or
a thread inserted between the stem of' the funnel and the
nozzle will leave an opening sufficient for the egress of the air.

64. i. Break some marble into small bits ; place them care-
fully in the evolution-flask, and, inserting the cork and tube,
pour in HC1 slowly. The gas, on account of its weight, may
be passed directly into a bottle or jar.

2. Lower a lighted candle into a jar of the gas, or, lowering
the candle into an empty jar, pour the gas into the jar, as if it
were water. Test the acid with litmus paper.

3. Place a piece of lime as large as an egg in a pint of wa-
ter; let it stand overnight; pour off the clear liquid — it is
lime-water. Place a little in a tumbler and breathe through it
by means of a tube, or pass a current of CO, from the evolu-
tion-flask until the liquid, at first milky, clears.

4. Breathe through a tube into an empty bottle. Lower
into it a lighted candle — it will be immediately extinguished.
Pour in some lime-water, shake it thoroughly and it will be-
come milky.

5. Twist a wire around the neck of a small wide-mouthed
vial, to answer as a bucket. Lower it by the wire into a jar
of COa, our ideal well foul with the gas. Raise it again, and
test for the CO, by means of a lighted match. The bucket
will be found to be full of the gas.

78 DIRECTIONS FOR PERFORMING

6. Fill a jar with hydrogen, and in a similar way dip the
gas downward and burn it over a lamp. This shows in a very
striking manner the difference between H and CO3 in respect
to specific gravity. The one, we see, is dipped upward, the
other downward.

7. Balance a large paper bag or box on a delicate pair of
scales, or in any simple manner one's ingenuity may suggest.
Empty into the box a large jar of CO3, and the box will quickly
descend.

8. Arrange little wax-tapers in a wooden or pasteboard
trough, as on page 65. Light them, and then pour in at the
top a bottle of carbonic acid gas. If the proper slant is given
to the trough, all the candles will be extinguished.

72. i. Olefiant gas may be made by heating in the flask one
part, by measure, of alcohol and two parts of sulphuric acid.
Pass it through a smution of potash, as shown on page 88, and
then collect in the gas-bag. Fit a piece of glass tubing, drawn
to a fine point at one end, to the stop-cock of the gas-bag by
means of a bit of the rubber tubing. On turning the stop-
cock and forcing out the gas it may be ignited, when it will
burn with a clear white light.

2. Fill a tall jar one-third full of olefiant gas, and the re-
mainder with chlorine gas. On lighting, the mixture will
burn with a dense cloud of smoke. HC1 is the product of the
combustion.

3. Mix with oxygen ana explode in soap-bubbles. It pro-
duces a greater noise even than the " mixed gases." Great
care must be taken not to let the light approach the gas-bag
containing the mixture.

4. Fit a large test-tube with a cork and a piece of glass
tubing, drawn to a fine point at the outer end. Fill the tub
with fine dry pine-shavings. On heating, the gases from the
wood will pass off, and can be ignited at the jet- tube. The
test-tube can be held by a strip of twisted paper or wire.

5. At the close of the ist exp. perform the one figured on
page 79. A small piece of wire-gauze, 4 or 6 inches square,
for this purpose can be purchased of any tinsmith. If you do
not force the gas out too rapidly, you will be able to burn it
on either side of the gauze at pleasure.

EXPERIMENTS IN THE CHEMISTRY. 79

79. Place on top of the gauze a bit of camphor-gum. Ig-
nite it, and the flame will not pass through to the lower side.
Then ignite on the lower side, and extinguish the flame on the
upper side.

77. The carbonic acid of a burning candle may be passed
through lime-water in the following manner. Take a bottle
arranged with tubes, as in the middle one shown in the figure
on page 87. From the tall tube at the left suspend a glass
funnel with the stem coupled to the tube by means of a piece
of rubber tubing. Place under this funnel a burning candle.
Partly fill the bottle with lime-water. Then placing the mouth
to the right-hand tube, draw out the air from the bottle. This
makes a draft over the candle, and draws its invisible smoke
through the funnel, down the long tube, and up through the
lime-water, which soon becomes milky.

SO. The compound blow-pipe with gasometers, as shown on
page 238, is the most serviceable. If gas-bags are used, the
one for hydrogen should be twice the size of the one for oxy-
gen. A board should be laid on each bag, upon which weights
may be placed, when ready for use, so as to force out the gas
steadily. Turn the stop-cock so that the H will pass out
twice as fast as the O. Always ignite the H first, and then
turn on the O slowly until the best effect is produced. If gas-
ometers are used, press the inner receivers down to the bottom,
and then pour in water till it reaches nearly the top. The rub-
ber pipes may then be attached to the hydrogen or oxygen
apparatus, and the gases passed directly into the gasometers.
Proper pressure is produced, when the jet is to be ignited, by
unloosing the strings from the inner receivers, and thus taking
off the " lift" of the weights which equipoise them. Additional
pressure is secured by bearing down upon the receivers. All
the metals burn in the blow-pipe flame with their character-
istic colors. Narrow slips should be prepared for this purpose.
A mirror, and a cup for holding the chalk, are necessary to
show the lime-light. A piece of hard chalk or lime, whittled
to about the size of a pencil, may be held in the flame to illus-
trate the principle.

87. Put in the flask two ounces of common salt and an
ounce and a half of black oxyd of manganese. Pour on

8o DIRECTIONS FOR PERFORMING

enough water to reduce the mixture to a thin liquid. Shake
the flask until the whole interior is moistened. Insert the cork
and delivery-tube ; the middle bottle shown in the figure is not
necessary. Fill the pneumatic cistern with warm water, using
just as small a quantity as possible, since water absorbs the gas.
Pour in an ounce of the oil of vitriol through the funnel-tube, or
directly at the nozzle, by removing the ground stooper, if a
kind of flask be used which has one. The gas will come ofi
at once, even before the heat is applied. Collect the gas in
bottles and use directly, if convenient, otherwise put corks in
them and rub the nozzles well with tallow. Pass the gas
through cold water, as shown on page 88, or more simply,
through a tumbler of water. This will form chlorine water,
which should be bottled and kept in a dark place.

2. Fill a test-tube nearly full of pure rain or snow watei,
and let fall into it a drop or two of the nitrate of silver solu-
tion. A drop of HC1 will form a cloudy white precipitate.

91. i. Place on a clean white dish a few scales of iodine
and a bit of phosphorus as large as a pea. It will soon ignite.

2. Fill three test-tubes nearly full of soft water. Pour in
one a few drops of a solution of bichloride of mercury, into
the second of sugar of lead, into the third of subnitrate of
mercury (formed by pouring NO6 on mercury). Add to each
of these a few drops of the solution of iodide of potassium.
The first especially will produce a brilliant color (iodide of
mercury) ; the rapid change from yellow to red is very marked.
On continuing to add the iodide of potassium, the red precip-
itate will be dissolved and disappear.

3. Make an additional quantity of the iodide of mercury,
as in the 2d exp. Let it settle. Pour off the liquid, and
then spread the sediment on a piece of heavy card-board,
making a red spot as large as a silver dollar. Dry it care-
fully. Then heat very strongly, when it will turn yellow.
Rub over the yellow spot the point of a knife several times,
bearing on very firmly, and a red mark can be seen. Lay away
the paper for a day or two, and the red color will spread ovei
the whole spot.

4. Dissolve a few scales of iodine in fifteen or twenty times
its bulk of alcohol. Pour a few drops of this solution on a

EXPERIMENTS IN THE CHEMISTRY. Si

freshly -cut potato or apple. Blue specks will show the pres-
ence of starch.

96. I. Melt a quantity of sulphur, either the flowers or
brimstone, in a test-tube. It is at first thick and dark-colored,
but after continued heating becomes thin and dark-colored.
Pour it now into water and it will form an elastic gum, which
can be moulded into any desired form.

2. Heat a piece of brimstone in a test-tube. After a little
the sulphur will sublime and collect in the upper part of the
tube as flowers of sulphur.

3. Fill a cup with brimstone and melt it with a gentle
heat. Set it aside to cool. When a crust has formed on
top, break it and pour out the liquid contents. If the cup
be broken, the bottom will be found covered with crystals of
sulphur.

1OO. Place in the evolution-flask half an ounce of sulphuret
of iron. Cover this with water, and then pour in oil of vitriol
through the funnel until the gas comes off freely. It may
be passed through a glass of cold water. This solution must
be bottled and closely corked. The gas may be tested di-
rectly; see page 137.

1O2. i. Cover a stick of phosphorus with dry, fine-pow-
dered charcoal. It will soon ignite.

2. Put in a vial half an ounce of sulphuric ether and a half-
dozen pieces of phosphorus not larger than grains of wheat.
Thoroughly shake and then set away. Repeat the shaking
often. When the phosphorus is dissolved, pour a little of the
solution on the hands, and when briskly rubbed together in a
dark place they will glow with a ghostly light.

3. Pour some of the solution on a lump of loaf-sugar. Drop
this in hot water, when the ether will catch fire.

4. Place in a wine-glass a few crystals of chlorate of potash
and a small bit of phosphorus. Fill the glass nearly full of
water. By means of a funnel-tube, pour a little oil of vitriol
to the bottom of the glass. A violent deflagration will imme-
diately take place, and, in a daik room, flashes of green light
will be seen.

119. Cut off three or four inches of magnesium ribbon, and
holding one end with a pair of pincers, thrust the ot-bf-r into

82 DIRECTIONS FOE PERFORMING, ETC.

the flame of the spirit-lamp. The metal will almost instantly
ignite, when it may be removed and held up to the view of the
class until the Mg is consumed.

124. To make a saturated solution of alum, drop crystals
of the salt into boiling water, until a drop of the liquid taken
out on the end of a glass rod and put on a bit of glass will
crystallize as soon as it cools.

134. Fill a test-tube nearly full of water. Pour in it a few
drops of the solution of sulphate of copper. Add ammonia,
and a blue precipitate will be formed. Notice the change from
green to blue. The sulphate of copper may be readily made
for this experiment by covering a copper cent with dilute oil of
vitriol. This experiment may be made to show the divisibility
of matter by weighing the cent, then seeing what proportion of
the whole solution you use, and then experiment to find what
quantity of water can be taken and yet have the blue color
perceptible in the ammonia test.

185. Fill a test-tube one-sixth full of sweet oil, add a little
ammonia, and nearly fill with water. The constituents remain
separate. Shake thoroughly, and they will combine, forming
a thin, soapy liquid. Add an acid, and they will dissolve part-
nership at once.

SUGGESTIONS.

Melted snow, or very clear rain-water, will answer the place
of distilled water in making solutions, &c., for experiments.
Whenever corks leak gas they may be wrapped with thin strips
of wet paper to make them fit more tightly, or the entire
nozzle may be smeared with tallow, or covered with sealing-
wax, if heat is not used. In that case a little plaster of paris
may be wet up and quickly applied. The experimenter will
find a retort-stand for holding the retorts, a test-tube holder, a
set of tin cork-borers, several Florence flasks of different sizes,
the copper retort for making oxygen, and the gas-bag, with
its tubing and connectors, almost indispensable. After these,
the compound blow-pipe is of the greatest value. A few drops
of a solution of magenta (i dr. in a gill of HO) will color the
water beautifully, and add to the effect of certain experiments.

KEY

TO

CHEMISTRY ip PHYSIOLOGY,

ANSWERS

TO THE

PRACTICAL QUESTIONS AND PROBLEMS

IN THE

FOURTEEN WEEKS IN CHEMISTRY,

REVISED EDITION,
WITH NEW NOMENCLATURE.

[The large figures refer to the page of the Chemistry^ and the small ones
to the number of the Question^

24. — i. In a 2$-lb. sack of common salt, how many
pounds of the metal sodium ?

Na = 23 = atomic weight of the given element.
NaCl = 58.5 = molecular weight of the compound.

x = weight of the given element.
25 Ibs. = " " compound.

Na : NaCl : : x : 25 Ibs.
23 : 58.5 : : x : 25 Ibs.
58.5 x = 575 Ibs.

x = 9rVT Ibs. (Na).

2, In 14 Ibs. of iron rust (Fe2O3), how much O?

Os = 48 = atomic weight of the given element.
FeaO3 = 160 = molecular weight of the compound.

x = weight of the given element.
14 Ibs. = w u compound.

O8 : FeaOs : : x : 14 Ibs.
48 : 160 : : x : 14 Ibs.
160 x — 672 Ibs.
x = 4£ Ibs. (O).

86 ANSWERS TO PRACTICAL QUESTIONS

3. How much S is there in 2 Ibs. 0/SO2 ?

S = 32 = atomic weight of the given element.
SO a = 64 = molecular weight of the compound.

x = weight of the given element.
2 Ibs. = " u compound.

S : SOa : : x : 2 Ibs.
32 : 64 : : x : 2 Ibs.
644 = 64 Ibs.
x = i lb. (S).

4. How much S is there in 2 Ibs. oj H2SO4 ?

S : H2SO« : : x : 2 Ibs.
32 : 98 : : jr : 2 Ibs.
98 x = 64 Ibs.
JT = SJ lb. (S).

5. .#bw w^ O is there in 5 Ibs. o/HNO3 ?

O3 = 48 = atomic weight of the given element.
HNO3 = 63 = molecular weight of the compound.

x = weight of the given element.
S Ibs. = " " compound.

O, : HNO3 : : x : 5 Ibs.
48 : 63 : : x : 5 Ibs.
63 x = 240 Ibs.
x = 3tf Ibs. (O).

6. How much H is there in 6 Ibs. of HC1 ?

H : HCl : : x : 6 Ibs.

i : 36.5 : : JJT : 6 Ibs.

36.5 x = 6 Ibs.

•* = A0. = I! lb. (H).

K2O tfw/;/ be made from 3 /Ar. ^/ K?

K, : KaO : : 3 Ibs. : x.

78 : 94 : : 3 Ibs. : x.

78 x — 282 Ibs.

* = 3r8s Ibs. (K.O).

40. — I. Are all acids sour ?

(See Chemistry, page 22, note, and also page xia)

IN CHEMISTRY. 87

2. What is the difference between an -ate, an -ite, and an
-ide compound?

An -ate compound is a union of an -ic acid with a base ;
an -ite compound is a union of an -ous acid with a base;
and an -ide compound is a union of two elements, a
binary compound. EXAMPLES. — Iron sulphate, FeSO4 ;
calcium sulphite, CaSO3 ; potassium chloride, KC1.

3. Why does not canned fruit decay ?
Because the O of the air is excluded.

4. Where is the higher oxide formed, at the forge or in
the pantry ?

(See Chemistry, page 33, note.)

5. Why is the blood red in the arteries and dark in the
veins ?

When specimens of venous and of arterial blood are
subjected to chemical examination, the differences pre-
sented by their solid and fluid constituents are found to
be very small and inconstant. As a rule, there is rather
more water in arterial blood, and rather more fatty mat-
ter. But the gaseous contents of the two kinds of blood
differ widely in the proportion which the carbonic acid
gas bears to the oxygen ; there being a smaller quantity
of oxygen and a greater quantity of carbonic acid, in
venous than in arterial blood. And it may be experi-
mentally demonstrated that this difference in their gaseous
contents is the only essential difference between venous
and arterial blood. For if arterial blood be shaken up
with carbonic acid, so as to be thoroughly saturated with
that gas, it loses oxygen, gains carbonic acid, and acquires
the hue and properties of venous blood ; while, if venous

88 ANSWERS TO PRACTICAL QUESTIONS

blood be similarly treated with oxygen, it gains oxygen,
loses carbonic acid, and takes on the color and properties
of arterial blood. — HUXLEY'S Lessons in Physiology.

6. Why do we need more oxygen in winter than in summer ?

Because there is a brisker fire going on in our cor-
poreal stoves.

7. Which would starve sooner ; a fat man or a lean one 1

(See Chemistry, page 35, note.)

A superabundance of flesh, in a time of scarcity, is
taken up by the absorbents and thrown into the circula-
tion, thus supplying the place of food in nourishing the
body.

8. How do teamsters warm themselves by slapping their
hands together ?

To produce the motion, additional O is supplied, and
increased oxidation is the result. This liberates heat to
warm the body. Besides, the blood sets to the arms and
the general circulation becomes more rapid. This extra
supply, both by its presence and the friction of the swiftly
moving currents, furnishes heat, and thus raises the tern
perature of the body.

9. Could a person commit suicide by holding his breath ?

Respiration is entirely independent of consciousness,
as is seen in sleep, coma, etc. It may be interrupted fot
a few minutes, but no effort of the will can enable one to
hold his breath until life is extinct. The desire for O,
the besoin de respirer, or the respiratory sense, as it is
called, becomes at last so great that the strongest reso-
lution yields the struggle.

IN CHEMISTS Y. 89

10. Why do we die when our breath is stopped1}

" In asphyxia it is difficult to say which destroys life,
the absence of oxygen or the presence of carbonic acid."
— FLINT. There is an absence of oxygen, so essential
to every vital operation, and also an accumulation of
carbonic acid * in the system.

1 1. Why do we breathe so slowly when we sleep ?

(See Chemistry, page 35.)

Because so little muscular action is going on in the
body.

12. How does a cold-blooded animal differ from a warm-
blooded one ?

In the imperfection with which the blood is oxygenated.
The lungs are often of small capacity, and loose texture,
and are sometimes wanting entirely. In reptiles a por-
tion of the blood is not sent to the heart, and hence in
the vessels there is a mixture of arterial and venous
blood. The breathing is therefore slow, the motions are
languid, and there is little heat.

13. Why does not the body burn out like a candle?

Because it is renewed by the processes of assimilation
and nutrition as rapidly as it is destroyed by the waste
of oxidation. Whenever the former are in excess we
gain flesh, when the latter, we grow poor.

14. Do all parts of the body change alike?

* This gas remains fixed in the blood-corpuscles, and renders them inca-
pable of furnishing any oxygen to the system. CO is a deadly poison,
because it clings to the disks more tenaciously.

9° ANSWERS TO PRACTICAL QUESTIONS

The rate of change varies with the amount of oxida-
tion, and that depends on the use of the organ. The
right arm of the blacksmith must be transformed much
more rapidly than the left.

15. What objects would escape combustion ?

Burnt bodies, i. e., those which are already combined
with oxygen.

1 6. How much oxygen can be obtained from 6 oz. of
KClOo ?

0:, : KC103 : : x : 6 oz.

48 : 122.5 • : x '• 6 oz.

122.5 x — 288 oz.

x = 2.35 oz. (O).
Or (see Chemistry, page 28), £& x 6 oz. = 2 £?s oz. (O).

17. How much KC1O3 would be needed to produce 2
Ibs. 0/O?

O, : KC1O3 : : 2 Ibs. : x.

48 : 122.5 : : 2 ^bs. : jr.

48 x = 245 Ibs.

x = SiV Ibs. (KC1O,).

1 8. How much KC1 would be formed in preparing i
Ib. o/O

(See Chemistry, page 28, diagram.)

If i Ib. is sW of a compound, what are ^f ?
Ans. -V<f Ibs. = ifc| Ibs. (KC1).

19. Name a substance from which the O can be set free
by the stroke of a hammer.

Potassium chlorate.

20. Name one from which it is liberated with great
difficulty.

Sand, carbonic anhydride. (See C/tem,, p. 98, note.)

IN CHEMISTRY. 91

21. Is .it probable that all the elements have been dis-
covered ?

(See Key, page 49, Question i.)

22. Is heat PRODUCED by oxidation ?

(See Chemistry, pages 36 and 100.^

All forms of force — electricity, heat, muscular energy,
chemical attraction, gravitation, etc., are now considered
as movements of molecules ; the particles being in con-
tinuous, undulatory motion, the swiftness and width of
the vibrations determining the character of the force.
These forces are interchangeable, but cannot be created
or annihilated, increased or diminished.

23. What is the difference between dynamic and potential
force?

A potential force is one that is latent ; a dynamic, one
that is sensible. The former is hidden ; the latter is in
full action. Potential force is a weight wound up, a loaded
gun, a river trembling on the brink of a precipice, a giant
waiting the word, an engine with the valve closed.
Dynamic force is the weight falling, the river tumbling,
the giant striking, the engine flying along the track.

24. Why does running cause panting?

As soon as we begin to perform any unusual exercise,
we commence breathing more rapidly — showing that, in
order to do the work, we need more O to unite with the
food and muscles. In very violent labor, as in running,
we are compelled to open our mouths, and take in deep
inspirations of oxygen.

25. How does O give us strength ?

(See Chemistry, page 35.)

9 2 ANSWERS TO PRACTICAL QUESTIONS

Our muscles, as well as the food from which they are
formed, consist of complex molecules, and the tension of
the forces is very great. When they oxidize, the potential
force becomes a dynamic one.

26. Does the plant PRODUCE force'!

(See Chemistry, page 100.)

It only gathers up the solar force.

27. If 'we burn an organic body in a stove,, it gives off
heat ; in the body it produces also motion. Explain.

The force set free by the oxidation of the muscles, and
food within the body is, by the principle of the correla-
tion of forces, converted into muscular energy.

28. In preparing N a thin, white cloud remains in the
Jar for a long time. What is it ?

Probably an antozone cloud.

49. — i. How could you detect any free O in ajar 0fN ?

By passing into the jar a bubble of NO, and watching
for the production of the red fumes of NO2.

2. How would you remove the product of the test?
By letting the jar stand over water.

3. In the experiment shown in Fig. 1 1, why is the gas red
in the flask, but colorless when it bubbles up into the jar ?

Because the NO2 formed by the air present in the flask
is absorbed by the H2O in the pneumatic tub.

4. How much H3N can be obtained from 3 Ibs. of sal-
ammoniac ?

IN CHEMISTRY. 93

(z). H,N : H4N,C1 : : x : 3 Ibs.
17 : 53.5 : : x : 3 Ibs.
53-5 •*" = 5* Ibs.

x = m lb. (H3N).

(2). From the formulae it is seen that any amount of sal-ammoniac will
yield |5f its weight of ammonia: hence, 3 Ibs. will give 3 Ibs. x ||f = fgf
lb. (H,N).

5. flow much H2O will be formed in the process'}

By examining the reaction given in the Chemistry ', page
48, it will be seen that \ of the H in each molecule of
H4N,C1 goes to form H2O. Hence, find (i) how much
H there is in 3 Ibs. of sal-ammoniac, and (2) how much
H2O would be formed by J- that amount of H.

(i) H4 : H4N,C1 : : x : 3 Ibs.
4 : 53-5 : : * V 3 Ibs.
53.5 jr = 12 Ibs.

x = T<& lb. (H).

(2) T%V lb. + 4 = T^T lb. T§T lb. x 9 * = T°5V lb. (HaO).

6. ^?z£/ wwr/^ CaO will be needed?

Find (i) how much O there is in -ffe lb. of H2O ;
and (2) how much CaO would be needed to furnish that
amount of O.

(i) TS5V lb. x I * = T«587- lb. ; hence, there are ^r lb. of O in the water pro-
duced.

(2) O : CaO : : TVr lb. : x.
16 : 56 : : T4587 lb. : x.
16 x = -\9oV8--

x - 1.57 + Ibs. (CaO).

7. In separating N, how much air will be needed to fur-
nish a gallon of the gas ?

About f of the atmosphere is N : hence, J of a gallon
of common air would be required to furnish one gallon

of N.

* See Chemistry \ page 24.

94 ANSWEB8 TO PRACTICAL QUESTIONS

8. How much N2O can be made from i Ib. of ammonium
nitrate ?

N8O : H4N,NO3 : : x : i Ib.

44 : 80 : : x : i Ib.

80 x = 44 Ibs.

x = ii Ib. (N20).

9. ^?a/ #zz/^ «//r*f #«V/ <:#« be formed from 50 /&r. of
sodium nitrate (NaNO3) 1

Find (i) how much N there is in 50 Ibs. of sodium
nitrate (Chili saltpetre), and (2) how much HNO3 could
be made from that amount of N.

(1) N : NaN03 : : x : 50 Ibs.
14 : 85 : : x : 50 Ibs.

85 x — 700 Ibs.
x = 8rV Ibs. (N).

(2) N : HNO. : : 8fy Ibs. : x.
14 : 63 : : 8TV Ibs. : x.

14 x = 518,4 Ibs.

x = 37Ty Ibs. (HN03).

10. What causes flesh to decompose so much more easily
than wood ?

It is partly owing to the greater complexity of its mole-
cule, and partly to the presence of the fickle N.

11. If a tuft of hair be heated in a test tube, the liquid
formed will turn red litmus-paper blue. Explain.

Ammonia is formed by the decomposition of the hair,
and this acting on the red litmus-paper turns it blue.

12. Why should care be used in opening a bottle of strong
H3N in a warm room ?

The volatile gas sometimes drives out the liquor am-
moniae with great force.

7^ CHEMISTRY. 95

13. What weight of N is there in 10 Ibs. <7/"HNO3 ?

N : HNO3 : : x : to Ibs.
14 : 63 : : jr : 10 Ibs.
63 .*• = 140 Ibs.
-r = 2g Ibs. (N).

14. ./iftw much sal-ammoniac would be required to make
2 Ibs. <7/-H3N?

HSN : H4N,C1 : : 2 Ibs. : or.
17 : 53.5 : : 2 Ibs. : x.
17 x = 107 Ibs.

x = 6T5f Ibs. (H4N,C1).

15. Give illustrations of the replacement of the H in an
acid by a metal.

(See Chemistry, page 44, note ; page 51, reaction ; and page 128, note.)

1 6. What is the difference between liquid ammonia and
liquor ammonia ?

Liquid ammonia is the gas condensed into a liquid by
cold: liquor ammonias is a solution of the gas in H2O.

63. — i. Why, in filling the hydrogen gun, do we use 5
parts of common air to 2 of H, and only one part of ' O to

2

Because the air is only \ oxygen, and hence 5 parts of
common air are equivalent to i part oxygen.

2. Why are coal cinders often moistened with H2O before

using ? (See Chemistry, page 57, note.)

The H2O being decomposed by the heat of the fire
increases the combustion.

3. What injury may be done by throwing a small quan-
tity 0/HzOon afire ?

" No more heat is produced by the action of the H2O,

96 AN8WEES TO PRACTICAL QUESTIONS

but it is in a more available form for communicating heat.
The steam in contact with incandescent charcoal is
decomposed — the O going to the C to form CO2, and
the H being set free. If the C is abundant, and the heat
high, the CO2 is also decomposed, and double its volume
of CO formed. The inflammable gases, H and CO,
mingled with the hydrocarbons always produced, are
ignited, making the billows of flame which sweep over
a burning building." — S. P. SHARPLES.

4. Why does the hardness of water vary in different
localities ?

The hardness of the water will necessarily vary with
the solubility of the minerals in different localities.

5. What causes the variety of minerals in the ocean ? Is
the quantity increasing ?

The ocean contains the washings of the land. Every
mineral soluble in water is borne to the sea. The quan-
tity of mineral matter in the ocean would therefore seem
to be increasing, yet there is a compensation in the return
to the soil, of guano, marine plants, and fish, which are
driven on shore by winds and waves, or carried by the
industry of man.

Analysis of sea-water (Schweitzer) :

Water 963-74

Sodium chloride 28.05

Potassium chloride .76

Magnesium chloride 3-66

Magnesium bromide .02

Magnesium sulphate 2.29

Calcium sulphate i-4°

Calcium carbonate -03

Iodine traces

Ammonia traces

IN CHEMISTEY. 97

6. Is there not a compensation in the sea-plants, fish, etc.,
which are washed back on the land ?

(See Answer to Question 5.)

7. Since " all the rivers flow to the sea" why is it not
full?

Because of the constant evaporation from its surface.

8. What is the cause of the tonic influence of the sea
breeze ?

There are traces of certain minerals which probably
give to the sea breeze a bracing influence. The air from
the ocean is also, doubtless, highly ozonized. Persons
with delicate lungs, therefore, find the sea breeze too
corrosive. In England, rheumatic and other inflammatory
diseases are more abundant near the coast than inland.

9. When fish are taken out of the water, and thus
brought into a more abundant atmosphere, why do they die ?

Fish inhale O through the fine silky filaments of their
gills. When a fish is drawn out of H2O, these dry up,
and it is unable to breathe, although it is in a more
plentiful atmosphere than it is accustomed to enjoy.

10. Do all fish die when brought on land?

(See Key, page 51, Question 15.)

11. What weight of water is there in 100 Ids. of sodium
sulphate (Na2SO4,ioH3O), or Glauber's salt1}

ioHaO : Na2SO4,ioH2O : : x : zoo Ibs.
180 : 322 : : x : 100 Ibs.

322 x — 18000 Ibs.

x = 55.9 Ibs. (H..O).

5

9 AN8WE&8 TO PRACTICAL QUESTIONS

12. What weight of water in a ton of alum (KA1,2SO4,
i2H2O)?

iaH2O : KA1,2SO«, i2H2O : : x : 2000 Ibs.
216 : 474-5 '. : x \ 2000 Ibs.

474.5 x = 432000 Ibs.

x — 910.4 Ibs. (HaO).

13. How much water would it require to furjiish enough
H to change 5 Ibs. of nitric anhydride to nitric acid?

Find (i) how much HNO3 could be made from 5 Ibs.
• of N2O5 (see Chemistry, page 44, note); (2) how much
H2O is contained in that amount of HNO3. The differ-
ence between the weight of the nitric anhydride and that
of the nitric acid will show the amount of water required
to furnish the H.

(i). N2O5 : 2(HNO.) : : 5 Ibs. : x.
108 : 126 : : 5 Ibs. : x.
108 x — 630 Ibs.

x = 5.833 Ibs. (HNO3).

(i). 5-833 Ibs. (HNO3) - 5 Ibs. (NaO.) = .833 Ib. (HaO).

14. How does the air purify running water?

The O contained in the air absorbed by the H2O
oxidizes the organic substances, which are the most
dangerous impurities.

15. What is the action of potassium permanganate as a
disinfectant ?

It gives up its O to oxidize the organic impurities.

1 6. Why does lime sometimes soften hard water when
added to it ?

(See Key^ page 50, Question 4.)

17. What weight of H can be obtained from a gallon
of water 1

ZiV CHEMISTRY. 99

The standard gallon of the United States weighs
8.3389 Ibs. of distilled water.

Ha : H2O : : x : 8.3389 Ibs.
2 : 18 : : x : 8.3389 Ibs.
9 x = 8.3389 Ibs.
x = .9265 Ib. (H).

1 8. In decomposing H3O, 65 parts by weight ofZn yield
2 parts by weight 0/~H. How much Zn must be employed
to obtain 100 Ibs.

If we look at the equation

H2SOt + Zn = ZnSO4 4- H2,

we see that

H3 signifies 2 parts by weight of hydrogen,

H2O 18

S " 32

ZnSO,

Ot " 64 ' " oxygen,

H2SO4 u 98 " ' " sulphuric acid,

Zn " 65 " l " zinc,

41 water,
' " sulphur,

zinc sulphate.

The equation, therefore, shows that 98 parts by weight
of sulphuric acid added to 65 parts of zinc will form 161
parts of zinc sulphate, and, decomposing 18 parts of
water, liberate 2 parts of hydrogen. For every part of
H we must have $£- parts of Zn : hence, to obtain 100
Ibs. of H we should need 100 Ibs. x *£• = 3250 Ibs. Zn.
In a similar way we can find the amount of each of the
other constituents needed.

19. How much KC1O3 would be required to evolve suf-
ficient O to burn the H produced by the decomposition of 2
Ibs. ^H2O?

(See Key, page 61, Question 37.)

100 ANSWERS TO PRACTICAL QUESTIONS

20. How much O would be required to oxidize the metallic
Cu which could be reduced from its oxide by passing over if,
when white-hot, 20 gr. ofH gas ?

(See Key, page 60, Question 34.)

21. How much O would be required to oxidize the metallic
Fe which could be reduced in the same manner by 10 grs.
of 'H gas?

(See Key, page 61, Question 35.)

22. Why are rose-balloons so buoyant ?

They are filled with hydrogen or coal-gas, which is
lighter than common air.

23. How much H must be burned to produce a ton of
water ?

Find how much H is contained in 2000 Ibs. of water.

(i). Ha : HaO : : x : 2000 Ibs.
2 : 18 : : x : 2000 Ibs.
18 x = 4000 Ibs.

X = 222| IbS. (H).

zd Method. — One-ninth of any weight of water is hydrogen ; hence,
2000 Ibs. -4- 9 = 222 1 Ibs. (H).

94. — i. Why does not blowing cold air on a fire with a
bellows extinguish it ?

More heat is liberated by the O which combines with
the fuel than is withdrawn from the fire by the current of
cold air. Yet the temperature of the fire must be suffi-
cient to elevate that of the O to the point of union with
C and H, else the fire will be extinguished.

3. Why is fire-damp more dangerous than choke-damp ?
Fire-damp, or marsh-gas, is inflammable, while choke-
damp, or " carbonic acid," is not.

IN CIIEMISTRY. 10 1

4. Represent the reaction, tn\'ifrdkfag CO $,'?. bowing the

atomic weights, as in the £>r£pqrajion of^Q on page 28.

In this experiment the acid' exchanges its Tiydrogen for
the calcium, producing calcium chloride (CaCl2) on the
one hand, and carbonic acid (H2CO3) on the other.
But the carbonic acid is so unstable that it immediately
becomes decomposed into water, which remains behind,
and into carbonic anhydride, which comes off as a gas
with brisk effervescence. The decomposition may be
represented as follows :

CaCO3 + 2HC1 = CaCl2 + H2O + CO2.

(Calcium Car- ) , j (Hydrochlo- ) _ j (Calcium I /Wa^r\ , j (Carbonic
bonate) ] + \ ric Acid) \~\ Chloride) f+ + 1 Anhydride)

Ca C O3 2(H CD Ca Cla + H2 O + C O3

40 + 12 + 3x16 2(1+35.5) 40 + 2(35.5) 2 + 16 12 + 2x16

The CO liberated = Tys of the materials used ; the HaO = rV8s, and the
CaCl3 = HI-

5. Should one take a light into a room where the gas is
escaping ?

Great care should be used, since coal-gas is combus-
tible, and when mixed with O in the proper proportion
explodes with great violence. Severe accidents frequently
occur from a neglect of this precaution.

6. What causes the difference between a No. i and a No. 4
pencil?

(See Chemistry, page 67.)

7. Why does it dull a knife to sharpen a pencil1!

(See Chemistry, page 67.)

102 ANSWERS TO PRACTICAL QUESTIONS

8. Why *V s/ate found fetwcm- seams of coal ?

{See-Geotogfr page 150.)

The* 'cbai' represents a period of vegetation, and the
slate, one of convulsion. During the former, a deposit of
the leaves, branches, trunks of trees, etc., was made ;
during the latter, one of gravel, sand, etc., accumu-
lated.

9. Why was the coal hidden in the earth ?

It is natural to think that one object was to protect it
from accidental combustion.

10. Where was the C, now contained in the coal, before
the Carboniferous age ?

(See Geology, pages 150-1.)

In the atmosphere, which was then so full of CO2 that,
according to certain authorities, it contained 7 to 8 parts
in 100.

1 1. Must the air have then contained more plant food ?

(See Chemistry, page 71, and Geology, page 150.)

12. What is the principle of the aquarium ?

The inter-dependence of animals and plants, whereby
each supplies the wants of the other. The aquarium is a
microcosm — a world in miniature.

* I have read somewhere a beautiful Persian fable in which a nightingale
and a rose are represented as being confined in a cage together, and being
dependent upon each other for life. The fable is truth symbolized. The idea
has now become more practical, but not less beautiful. In the modern
aquarium , or drawing-room fish-pond, we see the world in miniature. It is a
self-regulating, self-subsisting establishment, and is constructed on the most
perfect principles of chemical economy.

" Before this truth of compensation between animals and plants was dis-
covered, many attempts were made to keep fish in small glass globes. As

IN CHEMISTRY. 1 03

13. What test should be employed before going down in an
old well or cellar ?

A lighted candle should be lowered. If that is dimmed
or extinguished it is not safe for one to descend.

14. What causes the sparkle of wine and the foam of
beer ?

The CO 2 formed in the process of fermentation.

15. What causes the cork to fly out of a catsup bottle?
The CO 2 which is produced when the catsup ferments.

they soon exhausted the oxygen, and impregnated the water with carbonic
acid, it was necessary to change it daily. In this operation they suffered the
most intense fear. For a few weeks they would drag out a dubious exist-
ence, seemingly anxious only to find out before they died where they were and
how they got there. Finally, but a few years since, it was discovered that
plants evolve oxygen and consume carbonic acid in the water as well as in
the air. Starting out with this idea, about the year 1850, a Mr. Warrington,
an Englishman, set about breeding fish and mollusks in tanks by the aid of
marine plants. He succeeded admirably for a few days, but after a time, a
change came over his little world. Without apparent reason, the water
became suddenly impure and the fish died. Here was a new agency at work.
With the aid of a microscope, Mr. Warrington explored his tank for the
poison that was evidently latent there. He soon discovered that some of his
plants had reached maturity and, in obedience to the law of nature, had died.
The decaying matter was the poison of which he was in search. How was
this to be counteracted ? In nature's tanks — seas, rivers, and ponds — reflected
Mr. Warrington, plants must die and decay, yet this does not destroy animal
life. We must see how nature remedies the evil. He hastened to a pond in
the vicinity and examined its bottom with care. He found, as he had antici-
pated, an abundance of vegetable matter decayed. He likewise found
swarms of water-snails doing duty as scavengers, and devouring the putre-
fying substances before they had time to taint the water. Here was the
secret ; so beautiful a contrivance that it is said Mr. Warrington, with the
emotion of a true man of science, burst into tears when it flashed upon him
like a revelation.

" He, however, quickly dried his eyes, gathered a quantity of snails, and
threw a handful into his little tank at home. In a single day the water was
clear and pure again. The fish throve and gamboled, grew and multiplied ;
the plants resumed their bright colors, and the snails not only rollicked in an
abundance of decaying branches, but laid a profusion of eggs, on which the
fish dined sumptuously every day."

104 ANSWERS TO PRACTICAL QUESTIONS

1 6. What philosophical principle does the solidification of
CO g illustrate?

(See Philosophy^ page 242.)

That evaporation is a cooling process. A portion of
the liquid CO2 turns to vapor, and thus abstracts so much
heat from the remainder as to freeze it.

1 7. Why does the division in the chimney shown in Fig. 28
produce two currents ?

For a few moments there is an uncertainty — a condi-
tion of unstable equilibrium. The heated air is endeavor-
ing to rise, and the cold air trying to come in to supply
its place. The situation of the candle in the jar deter-
mines the length of time before the currents start. If the
candle be placed on one side of the jar they will be
established almost instantly.

1 8. What causes the unpleasant odor of coal-gas ? Is it
useful?

Impurities which it contains. Olefiant gas has a faint
sweetish odor, while carbonic oxide and hydrogen, when
pure, are inodorous. The disagreeable smell is due in
part to acetylene (C2H2). The unpleasant odor warns
us of the presence of coal-gas.

19. What causes the sparkling often seen in a gas-light?

Particles of lime taken up mechanically in the process
of purification.

20. Why does H in burning give out more heat than C ?

i Ib. of H burned in O emits heat sufficient to melt
315.2 Ibs. of ice; and 12 Ibs. of carbon converted into
CO 2 enough to melt 700 Ibs. of ice. (This subject is

IN CHEMISTRY. 105

quite fully treated in Miller's Chemical Physics, page 294,
et seq.) The cause is not as yet fully determined, although
it is perhaps safe to say that in ordinary combustion the
heat depends on the amount of O which enters into com-
bination with the fuel. " Thus hydrogen in burning takes
up three times as much O,as C does, and hence gives off
three times as much heat." — YOUMANS.

2 1. Why does blowing on afire kindle it, and on a lighted
lamp extinguish it ?

(See Key, page 50, Question 6.)

22. Why can we not ignite hard coal with a match ?
Because it is a good conductor of heat.

23. What causes the dripping of a stove-pipe ?

The condensation of the water formed in the combus-
tion of the fuel.

24. Why will an excess of coal put out afire ?

Because it will absorb the heat, and thus reduce the
temperature of the fire below the combining point of C
andO.

25. Why do not stones burn as well as wood?
Because they are already burned, i. e., combined with O.

26. Why does not hemlock make good coals ?

Because (i) of its lack of C, and (2) its porous struc-
ture.

27. What adaptation of chemical affinities is shown in a
light ?

If O had the same affinity for C that it has for H, they
would be consumed at once, with little light. The fact

106 ANSWERS TO PRACTICAL QUESTION'S

that the H burns first, and thus heats up to the lumi-
nous point the particles of C as they float outward to
the air, causes the illuminating power of the hydro-
carbons.

28. Is there a gain or a loss of weight by combustion ?

The products of combustion weigh as much as the fuel
and the O which enters into combination with it.

29. Why does snuffing a candle brighten the flame ?

Because it removes the charred wick, which diminishes
the heat of the flame both by conduction and radiation.

30. Why is the flame of a candle red or yellow ', and that
of a kerosene oil-lamp white ?

(See Philosophy, page 225.)

The heat of a candle-flame is much less than that of
kerosene, and thus the colors characteristic of a lower
temperature are produced.

31. Why does blowing on a light extinguish it?

Because it lowers the temperature of the flame below
the point of union between O and C.

32. Why will water put out afire?

(See Chemistry, page 93.)

Partly by absorbing the heat of the fire, and partly by
shutting out the O.

33. What should we do if a person's clothes take fire t

The best course is to wrap the person in a blanket,
carpet, coat, or even in his own garments. This smothers
the fire by shutting out the O.

IN CHEMISTRY. 107

34. Ought we to leave open the doors or windows of a
burning house ?

(See Chemistry, page 93.)

No. Open doors or windows will make draughts of air
to feed the flame.

35. Why does a street gas-light burn blue on a windy
night ? Is the light then as intense ? The heat ?

O is mingled with the flame in sufficient quantities to
burn the H and C simultaneously. Thereby the heat is
increased, but the light diminished. The principle is that
of Bunsen's burner.

36. Why does not the lime burn in a calcium-light?
Lime is a burned body; its symbol is CaO.

37. Why is a candle-flame tapering?

(See Chemistry, page 88.)

The currents of air rushing toward the flame from all
sides give it the conical form.

38. Why does a draught of air cause a lamp to smoke ?

It lowers the heat of the flame below the point of union
between C and O, and thus the C is precipitated.

39. What makes the coal at the end of a candle-wick ?

The wick at the edge of the flame comes in contact
with the O of the air, and therefore burns.

40. Which is the hottest part of a flame?

Toward the point of the cone, where the gaseous en-
velopes meet and make a solid flame.

IO ANSWERS TO PRACTICAL QUESTIONS

41. Why does not a candle-wick burnt
There is no O at the centre of the flame.

42. How does a chimney enable us to burn highly car-
boniferous substances like oil without smoke ?

(See Chemistry, page 88.)

It keeps out the cold air, and elevates the temperature
of the O, which supplies the flame. Thus more C can be
consumed.

43. How much CO 2 in 200 Ibs. of chalk?

CO, : CaCO3 : : x : 200 Ibs.
44 : 100 : : x : 200 Ibs.

100 x — 8800 Ibs.

x = 88 Ibs. (CO2).

44. What weight of CO % in a ton of marble 1

CO2 : CaCO3 : : x : 2000 Ibs.
44 : 100 : : x : 2000 Ibs.

zoo x — 88,000 Ibs.
x = 880 Ibs. (CO3).

45. What is the difference between marble and chalk ?

Marble is a compact, crystallized carbonate of lime,
while chalk is a porous kind of limestone.

46. Why does not a cold saucer held over an alcohol flame
blacken, as it does over a candle or gas-light ?

There is less C in alcohol than in tallow or in coal-gas.

47. Could a light be frozen out, i. e., extinguished, by
merely lowering the temperature ?

It is said to have been done in Arctic regions.

IN CHEMISTRY. IO9

48. How much CO2 is formed in the combustion of one
ton of Cl

C : COa : : 2000 Ibs. : x.

12 : 44 : : 2000 Ibs. : x.

12 x = 88,000 Ibs.

* = 7333-33+ Ibs. (CO2).

49. What weight of C is there in a ton of CO8 ?

C : COa : : x : 2000 Ibs.

12 : 44 : : x : 2000 Ibs.

44 x — 24,000 Ibs.

^ = 545-45 + Ibs. (C).

50. How much O is consumed in burning a ton ofCJ

In any quantity of CO2, -fj- of the compound is O, and
^ C. If -j^- = 2000 Ibs. (CO2), then -^ = f of 2000 Ibs.
= 5333-33 + Ibs. (O).

51. What weight of sodium carbonate (Na2CO3, ioH2O,
" carbonate of soda ") would be required to evolve 12 Ibs.
<?/C02?

COa : NaaCO3, ioHaO : : 12 Ibs. : x.
44 : 286 : : 12 Ibs. : x.

44 x = 2432 Ibs.

x = 50.72 Ibs. (NaaCO3,ioHaO).

52. How much CO 2 will be formed in the combustion of

CO : COa : : 30 grs. : x,

28 : 44 : : 30 grs. : x.

28 x = 1320 grs.

x = 47.14 grs. (COa).

5 3 . What weight of hydrogen sodium carbonate ( H NaCO 3 ,
" bi-carbonate of soda ") would be required to evolve 12 Ibs.

C0a : HNaC03 : : 12 Ibs. : x.
44 : 84 : .- 12 Ibs. : x.
44 x = 1008 Ibs.

x = 22.9 Ibs. (HNaCO,).

HO ANSWERS TO PRACTICAL QUESTIONS

54. Write in double columns the different properties of
carbonic anhydride and carbonic oxide.

1. COS.

2. Atomic weight — 44.

3. Specific gravity— 1.529.

4. Will not burn.

5. A negative poison.

6. Liquefies at 32°, and a pressure

of 38.5 atmospheres.

7. Freely soluble in H2O.

8. Forms salts.

&c., &c.

1. CO.

2. Atomic weight — 28.

3. Specific gravity — .967.

4. Burns with a blue flame.

5. A direct poison.

6. Has never been liquefied.

7. Sparingly soluble in water.

&c., &c.

1 1 8. — i. If chlorine water stands in the sunlight for a
time, it will only redden a litmus-solution. Why does it not
bleach it?

Hydrochloric acid is formed, which reddens the lit-
mus.

2. Why do tinsmiths moisten with HC1, or sal-ammoniac,
the surface of metals to be soldered ?

It dissolves the coating of oxide and leaves the surface
of the metal free for the action of the solder.

3. How much HC1 can be made from 25 Ibs. of common
salt ?

Find (i) how much Cl there is in 25 Ibs. of NaCl, and
(2) how much HC1 that amount of Cl would make.

(i). Cl : NaCl : : x : 25 Ibs.
35-5 : 58.5 :: x : 25 Ibs.
58.5 » = 887.5 Ibs.

x = 15.17094 Ibs. (Cl).

(2). Cl : HC1 : : 15.17094 Ibs. : x.
35-5 : 36-5 : : i5-i7°94 Ibs. : x.
35-5 x - 553-73931 Ibs.

x - 15.5980056-1- Ibs. (HC1).

IN CHEMISTRY. Ill

4. What weight of NaCl would be required to form 25
Ibs. of muriatic acid ?

(See Key^ page 58, Question 20.)

5. HC1 of a specific gravity of 1.2 contains about ^ per
cent, of the gas. This is very strong commercial acid.

What weight could be formed by the HC1 acid gas produced
in the reaction named in the preceding problem ?

(See Key, page 58, Question 21.)

6. What is the difference between sublimation and distilla-
tion ?

A body is said to sublime when it rises as vapor and
condenses in the solid form ; when it condenses as a liquid
it is said to distil.

7. Why do eggs discolor silver spoons ?

The sulphur of the egg combines with the Ag, forming
silver sulphide — the black sulphuret of silver.

8. Explain the principle of hair-dyes.

The two principal chemicals used for dyeing the hair are
lead and silver nitrate. The S in the hair combining with
the Ag makes silver sulphide, or with the Pb, lead sul-
phide, either of which stains the hair : the former colors
the skin as well as the hair, while the latter is absorbed
through the skin, causing colics and other diseases such
as are common among painters. The "golden yellow
color" lately in fashion is produced by a solution of ar-
senic with the hydrosulphate of ammonia. In order to
dye the lighter tints, it is necessary to bleach the hair
with an alkaline solution. See Fireside Science, page 77.

112 ANSWERS TO PRACTICAL QUESTIONS

9. Why is new flannel apt to turn yellow when washed ?

New flannels, washed in strong soap, turn yellow, be-
cause the alkali of the soap unites with the SO2 used in
bleaching the cloth, and thus sets free the original color.

10. Is it safe to mix oil of vitriol and water in a glass
bottle ?

The heat produced by the combination of the two will
be liable to break the glass.

11. What is the color of a sulphuric acid stain on cloth ?
How would you remove it?

It is generally red, especially on black cloth. The
color may be restored by a few drops of a solution of
common "soda."

12. What causes the milky look when oil of vitriol and
water are mixed ?

Pb from the stills in which the acid is condensed, and
which is soluble in strong H2SO4, is precipitated when
the acid is diluted with HSO.

13. What is the relation between animals and plants ?
Which perform the office of reduction, and which that of

oxidation ?

(See AVy, page 52, Question 19.)

14. How many pounds of S are contained in 100 Ibs. of
H2SO4?

S : H2SO4 : : x : 100 Ibs.
32 : 98 : : x : 100 Ibs.
98 x = 3200 Ibs.
x = 32-Jf Ibs. (S).

IN CHEMISTRY. 113

15. How much O and H2O are needed to change a ton
of SO2 /*H8SO4?

One ton of SO2 will make i£f tons of H2SO4 : of
which -fa is H, Jf is S, and £f is O. i of this O, or ^
comes from the air, and i = ^ ^rom ^e water- (See pro-
cess of manufacture, Chemistry, p. 116.) Hence -fa (O)
and j^. (H) = -£§ of the acid was furnished by the water —
-fs of i-y- tons = -^g- ton (H2O). The process of reason-
ing may be seen more clearly, perhaps, by preparing the
formulae as in Question 18, page 99, of this Key.

1 6. How much O in a Ib. <?/~H2SO4 ?

f f- of any quantity of sulphuric acid are O ; -fa is
H ; and £f are S. Hence in i Ib. of H2SO2 there are

17. State the analogy between the compounds qfO and S.

o

HaO

H2O2 (hydrogen dioxide)

C03

S

H2S

H2Sa

CS2

The corresponding compounds possess not only an an-
alogous composition, but also similar chemical proper-
ties.

146. — i. In the experiment with Na2SO4, on page 133,
an accurate thermometer will show that in making the solu-
tion^ the temperature of the liquid will fall, and in its solidi-
fication, will rise. Explain.

(See Philosophy, page 233.)

The solid salt passing into a liquid takes up heat,
and, in returning from a liquid to a solid again, gives
up heat. The latter is illustrated in next question.

H4 ANSWERS TO PRACTICAL QUESTIONS

2. If, in making a solution of Na2SO4, we use the salt
which has effloresced, and so become anhydrous, the tempera-
ture will rise instead of falling as before. Explain.

This is because a solid hydrate is formed before the
salt dissolves in the H2O. The same holds true of other
anhydrous bodies, as the chlorides of Zn, Fe, and Cu.

3. Why is KNO3 used instead of NaNO3 for making
gunpowder ?

Sodium nitrate is imported from Chili in large quanti-
ties, and attempts have been made to use it for making
gunpowder,*' but its tendency to attract moisture has
frustrated the plan. It is now extensively used as a fer-
tilizer, and is said to be the cheapest form in which N
can be furnished the soil.

4. Why is a potassium salt preferable to a sodium one in
glass-making ?

Sodium salts give a greenish tint to the glass.

* Gunpowder is an intimate mechanical mixture of about i part nitre, i part
sulphur, and 3 parts charcoal. These proportions, however, vary somewhat
in different countries, as well as in different sorts of powder. More charcoal
adds to its power, but also causes it to attract moisture from the air, which of
course injures its quality. For blasting rocks, where a sustained force, rather
than an instantaneous one, is required, the powder contains more sulphur,
and is even then often mixed with sawdust to retard the explosion. The
nitre, sulphur, and charcoal, having been ground and sifted separately, are
thoroughly mixed and then made into a thick paste with water. This is
ground for some hours under edge-stones, after which it is subjected to im-
mense pressure between gun-metal plates, forming what is known as press-
cake. These cakes are then submitted to the action of toothed rollers, where-
by the granulation of the powder is effected. The grains thus formed are
sorted into different sizes by means of a series of sieves, and thoroughly dried
at a steam heat. The last operation, that of polishing, is accomplished in re-
volving barrels, after which the powder is ready for market. The heavier
the powder, the greater is its explosive power. Good powder should resist
pressure between the fingers, giving no dust when rubbed, and have a
slightly glossy aspect.— YOUMANS.

IN CHEMISTRY. 11$

5. What is the glassy slag so plentiful about a furnace ? *

A silicate of lime or some other base contained in the
ore.

Ordinary Slag from Blast Furnace (Bloxani).

Silica 43.07

Alumina 14-85

Lime 28.92

Magnesia 5.87

Oxide of iron 2.53

Oxide of manganese -. 1-37

Potash 1.84

Sulphide of calcium 1.90

Phosphoric acid trace

100.35

6. State the formula of nitre, saleratus, carbonate and
bicarbonate of soda, plaster, pearlash, saltpetre, plaster of
Paris, gypsum, carbonate and bicarbonate of potash, sal-soda*
and soda.

Nitre, saltpetre KNO3.

Saleratus, pearlash HKCOS.

Carbonate of soda, sal-soda. NaaCO3.

Bicarbonate of soda, "soda".... HNaCO3.

Plaster, gypsum CaSO4,2HsO.

Plaster of Paris CaSO«.

7. Explain how ammonium carbonate is formed in the
process of making coal-gas.

Nitrogen exists in small quantities in coal, and when
that is distilled at a high temperature, the elements in
their nascent state combine to form this compound.

* The slag is commonly employed for road-making in the neighborhood of
the iron-works. Some attempts have been made to turn the slag to account
by employing it as a manure for soils deficient in potash, of which it will be
seen that the above slag contains nearly s\jth of its weight, in a form which
would be easily rendered available for plants by the combined action of air
and moisture. When the slag is run into water, or blown into a frothy con-
dition by the blast, it resembles pumice-stone, and is easily ground to a pow-
der fit for applying to the soil.

Il ANSWERS TO PRACTICAL QUESTIONS

8. Upon what fact depends the formation of stalactites ?

Water containing carbonic acid in solution will dissolve
carbonate of lime freely, but when, on exposure to the
air, the gas escapes, the carbonate is deposited.

9. Why is HF kept in gutta-percha bottles ?

Because it will dissolve silica, and so destroy a glass
bottle.

10. Explain the use of borax in softening hard water?

It softens hard water by uniting with the soluble salts
of lime or magnesia, and making insoluble ones which
settle and form a thin sediment in the bottom of pitchers
in which it is placed.

1 1 . How are petrifactions formed ?

Certain springs contain large quantities of some alka-
line carbonate ; their waters, therefore, dissolve silica
abundantly. If we place a bit of wood in them, as fast
as it decays, particles of silica will take its place — atom
by atom — and thus petrify the wood. The wood has
not been changed to stone, but has been replaced by stone.

12. In what part of the body, and in what forms , is
phosphorus found ?

As a phosphate if is the principal earthy constituent of
the bones. It is also a never-failing ingredient of the
brain and nervous system. The susceptibility of phos-
phorus to oxidation especially adapts it to the rapid
changes incident to the structure and offices of the
brain.*

* Phosphorus is an element which can imperceptibly and quickly pass from
a condition of great chemical activity to one of equal chemical inertness. In

IN CHEMISTRY. 1 17

13. Why are matches poisonous ? What is the anti-
dote?

(See Physiology, page 209.)

Because of the phosphorus in the match.

virtue of this character, it u may follow the blood in its changes, may oxidize
in the one great set of capillaries, and be indifferent to oxygen in the other ;
may occur in the brain, in the vitreous form, changing as quickly as the
intellect or imagination demands, and literally flaming that thoughts may
breathe and words may burn ; and may be present in the bones in its amor-
phous form, content like an impassive caryatid, to sustain upon its unwearied
shoulders the mere dead weight of stones of flesh. And what is here said of
the brain as contrasted with the bones, will apply with equal or similar force
to many other organs of the body. All throughout the living system, we
may believe that phosphorus is found at the centres of vital action in the
active condition, and at its outlying points in the passive condition. In the
one case it is like the soldier with his loaded musket pressed to his shoulder
and his finger on the trigger, almost anticipating the command to fire ; in the
other it is like the same soldier with his unloaded weapon at his side standing
at ease."

" Further, phosphorus forms with oxygen a powerful acid, capable even of
abstracting water from sulphuric acid, and yet perfectly unirritating to the
organic textures. Taking up varying quantities of water, phosphoric acid
assumes no fewer than three distinct forms, which will unite with one, two,
or three atoms of alkali respectively, giving an acid, neutral or alkaline reac-
tion. Thus it is available for the most varied uses in the body. A child is
beginning to walk, and the bones of its limbs must be strengthened and
hardened ; phosphoric acid, accordingly, carries with it three units of lime to
them, and renders them solid and firm. But the bones of its skull must
remain comparatively soft and yielding, for it has many a fall, and the more
elastic these bones are, the less will it suffer when its head strikes a hard
object ; so that in them we may suppose the phosphoric acid to retain but two
units of lime, and to form a softer, less consistent solid. And the cartilages
of the ribs must be still more supple and elastic, so that in them the phos-
phoric acid may be supposed to be combined with but one unit of base. On
the other hand, its teeth must be harder than its hardest bones, and a new
demand is made on the lime-phosphates to associate themselves with other
lime-salts (especially fluoride of calcium), to form the cutting edges and
grinding faces of the incisors and molars. All the while, also, the blood must
be kept alkaline, that oxidation of the tissues may be promoted, and albumen
retained in solution ; and yet it must not be too alkaline, or tissues and albu-
men will both be destroyed, and the carbonic acid developed at the systemic
capillaries will not be exchanged for oxygen when the blood is exposed to
that gas at the lungs. So phosphoric acid provides a salt containing two

Il8 ANSWERS TO PRACTICAL QUESTIONS

14. Will the burning phosphorus ignite the wood of the
match ?

It does not give off enough heat in its oxidation to
raise the temperature of the wood to the igniting point.
Many, however, claim the true reason to be that, in burn-
ing, it produces an ash (P2O5) which covers the wood as
with a varnish and so protects it from oxidation.

15. What philosophical principle is illustrated in the
ignition of a match by friction ?

(See Philosophy, page 230.)

The conversion of motion into heat.

1 6. How much H2O would be required to dissolve a
pound of "KNO3 ?

3 £ Ibs. of cold water and \ Ib. of hot water.

17. What causes the bad odor after the discharge of a
gun?

The potassium sulphide gradually gives up its S to
form HgS.

1 8. Write in parallel columns the properties of common
and of red phosphorus.

units of soda and one of water, which is sufficiently alkaline to promote
oxidation, dissolve albumen, and absorb carbonic acid, and yet holds the lat-
ter so loosely, that it instantly exchanges it for oxygen when it encounters
that gas in the pulmonary capillaries. Again, the flesh juice must be kept
acid (perhaps in opposition to the alkaline blood, as affecting the transmission
of the electric currents which traverse the tissues), and phosphoric acid pro-
vides a salt, containing two units of water and one of potash, which secures
the requisite acidity."— DR. G. WILSON, Edinburgh Essays, 1856.

IN CHEMISTRY.

Common phosphorus.

i. Specific gravity— 1.83.
a. Burns at iu°.

3. Odor of garlic.

4. Soluble in CS2.

5. Colorless,, or straw-yellow.

6. A deadly poison.

Amorphous phosphorus.

1. Specific gravity— 2.14.

2. Burns at 500'.

3. Odorless.

4. Insoluble in CSa.

5. Red often rivalling vermilion.

6. Harmless.

19. What causes the difference between fine and coarse
salt?

(See Chemistry, page 132.)

The rapidity of evaporation in the process of manu-
facture.

20. Why do the figures in a glass paper-weight look larger
when seen from the top than from the bottom ?

The form of the glass acts like a convex lens to mag-
nify the apparent size of the figures.

21. What is the difference between water-slacked and air-
slacked lime ?

The former is simply calcium hydrate, CaO, H2O, while
the latter is hydratecl calcium carbonate, CaO, CO2,
H80 (?).

22. Why do oyster-shells on the grate of a coal- stove pre-
vent the formation of clinkets ?

The lime of the shells acts as a flux with the iron in
the coal, thus dissolving the clinkers, if any form.

23. How is lime-water madej/om oyster-shells ?

The shells are burned, driving off the CO3 combined
with the CaO in the CaCO3, and the lime thus formed is
slightly soluble in water.

120 ANSWERS TO PRACTICAL QUESTIONS

24. Why do newly plastered walls remain damp so long?

The plaster or mortar in drying gives off the water the
lime took up in slacking.

25. Will lime lose its beneficial effect upon a soil after
frequent applications ?

(See Key, page 51, Question 12.)

26. What causes plaster of Paris to harden again after
being moistened ?

(See Chemistry , page 139.)

It recombines with the water which was driven off in
the process of its manufacture.

27. What is the difference between sulphate and sulphite
of lime'}

The former is a compound of sulphuric acid ; the lat-
ter of sulphurous acid.

28. What two classes of rays are contained in the mag-
nesium light?

(See Philosophy, page 206.)

The actinic or chemical, and the colorific or luminous
rays.

29. What rare metals would become useful in the arts, if
the process of manufacture were cheapened ?

Magnesium, aluminum, sodium, etc.

30. What is the rational formula for calcium carbonate ?
Calcium sulphite ? Calcium sulphate ?

1. CaCO3 = CaO,CO2.

2. CaSO3 = CaO,SO2.

3. CaSO4 = CaO,SO3.

IN CHEMISTRY. 121

31. Why is lime placed in the bottom of a leach-tub I

The potash of the ashes is generally in the form of a
carbonate, the acid neutralizing in part the strength of the
alkali. The lime combines with the CO2.

32. Is saleratus a salt of K or of Na ?

It should be a carbonate of K, but, on account of its
cheapness, the corresponding salt of Na is often sold in-
stead.

33. Why will Na burst into a blaze when thrown on hot
water ?

The heat of the water raises the hydrogen to the ignit-
ing point. This catches fire, and the volatilized Na colors
the flame.

34. Why are certain kinds of brick white ?

They contain no iron, this being the substance which
by its oxidation gives the color to common brick.

35. Illustrate the force of chemical affinity.

The tremendous force of chemical affinity forms with O
half the crust of the earth. Yet when the chemist sets the
O free from its prison-house, it comes before him a transpa-
rent, invisible gas, and he cannot condense it to a solid or
liquid state by any mechanical process.

176. — i. Pb is softer than Fe ; why is it not more mal-
leable?

The facility with which a mass of metal can be ham-
mered or rolled into a thin sheet without being torn, must
depend partly upon its softness, and partly upon its tena-
city. If it depended upon softness alone, lead should be

122 ANSWEES TO PRACTICAL QUESTIONS

the most malleable of ordinary metals ; but, although it is
easy to hammer a mass of lead into a flat plate, or to
squeeze it between rollers, any attempt to reduce it to an
extremely thin sheet fails from its want of tenacity, which
causes it to be worn into holes by percussion or friction.
On the other hand, if malleability were entirely regulated
by tenacity, iron would occupy the first place, whereas, on
account of its hardness, it is the least malleable of metals
in ordinary use ; whilst gold, occupying an intermediate
position with respect to tenacity, is the most malleable,
which appears surprising to those who are only acquainted
with gold in its ordinary forms of coin and ornament, in
which it is hardened and rendered much less malleable
by the presence of copper and silver.

I.— Relative Malleability of the Metals.

1. Gold. 4. Tin. 7. Zinc.

2. Silver. 5. Platinum. 8. Iron.

3. Copper. 6. Lead.

II.— Relative Tenacity of the Metals.

Lead

i

Silver

12*

Tin...

i|

Platinum

Zinc

2

Copper . .

.... 18

n>

Iron

27i

Gold...

.. 12

Steel . . .

.. 42

III.— Relative Ductility of the Metals.

1. Gold. 5. Copper. 8. Zinc.

2. Silver. 6. Palladium. 9. Tin.

3. Platinum. 7. Aluminum. 10. Lead.

4. Iron. — BLOXAM.

2. What is the cause of the changing color often seen in
the scum on standing water ?

(See " Interference of Light," Philosophy, page 209.)

The thin pellicles of iron-rust on standing H2O pro-

IN CHEMISTRY. 123

duce a beautiful iridescent appearance, the color changing
with the thickness of the oxide. A soap-bubble exhibits
in the same way a play of variegated colors according to
the thickness of the film in different parts.

3. How can the spectra of the metals be obtained?

(See Astronomy, page 285.)

By looking through a prism at a flame containing min-
ute portions of the volatilized metal.

4. Ought cannon, car-axles, etc., to be used until they break
or wear out ?

Cannon are condemned and recast after being fired a
certain number of times, even though they show no flaw,
as the jarring to which they are exposed causes the iron
to take on a crystalline form and become less fibrous and
tough. A cast-iron gun of lo-inch bore or less, ought to
stand 1000 rounds ; larger calibres, a smaller number.

5. Why is " chilled iron" used for safes ?

The iron being cooled so instantaneously, the crystals
are exceedingly small, and the metal is correspondingly
harder than when cast in the ordinary way.

6. Does a blacksmith plunge his work into water merely
to cool it ?

The metal is harder when cooled quickly and therefore
resists wear longer.

7. What causes the white coating made when we spill
water on zinc ?

The oxide of zinc which is formed on the surface of the
metal through the favoring influence of the water.

124 ANSWERS TO PRACTICAL QUESTIONS

8. Is it well to scald pickles , make sweetmeats, or fry cakes
in a brass kettle ?

(See Chemistry, page 159.)

9. What danger is there in the use of lead pipes ? Is a
lining of Zn or Sn a protection ?

(See Chemistry, pages 156 and 160, and Fireside Science, page 149.)

Zinc and tin are corroded by oxygen, though less read-
ily than Pb, and, while their salts are poisonous, the lead
is soon laid bare, and this also oxidizes.

10. Is water which has stood in a metal-lined ice-pitcher
healthful?

(See Chemistry, page 157.)

The dissimilar metals fastened with solder which cor-
rodes in the presence of water, develop a galvanic current
which hastens the oxidation. The salts thus formed are
very dangerous.

11. If you ask for " cobalt" at a drug-store, what will
you get ? If for " arsenic ? ' '

Impure metallic arsenic is sold as "cobalt," while
arsenious anhydride is called "arsenic."

12. What two elements are fluid at ordinary tempera-
tures ?

Bromine and mercury.

13. Should we touch a gold ring to mercury ?

The mercury will form with the gold an amalgam.

IN CHEMISTRY. 125

14. Why does silver blacken if handled?

The perspiration of the body contains S, which combin-
ing with the metal forms silver sulphide — the black sul-
phuret of silver.

15. Why does silver tarnish rapidly where coal is used
for fires ?

S, which is present in coal, is set free by combustion
and forms a silver sulphide.

1 6. Why is a solution of a coin blue?

From the Cu which is contained in silver coin.

17. Why will a solution of silver nitrate curdle brine ?
A white, curdy precipitate of silver chloride is formed.

1 8. Why does writing with indelible ink turn black when
exposed to the sun, or to a hot iron ?

By the decomposition of the silver salt contained in the
ink, and consequent production of AgsO, which stains
organic matter black.

1 9. What alloys resemble gold ?
Oreide, aluminum-bronze, etc.

20. Why does a fish-hook " rust out " the line to which it
is fastened ?

Ferric oxide and ferric hydrate act as conveyers of O,
absorbing it from the air and giving it up to organic
bodies with which they are in contact.

21. Why do the nails in clap-boards loosen ?

(See Question 20.)

126 ANSWEE8 TO PRACTICAL QUESTIONS

22. Show that the earths crust is mainly composed of
burnt metals.

(See Cooke's Religion and Chemistry?)

It consists largely of potassium, magnesium, calcium,
aluminum, sodium, etc., in combination with O. These
compounds are the products of combustion.

The elements O, Si, Al, Mg, Ca, K, Na, Fe, C, S, H,
Cl and N — 13 in all — probably make up 19^r of the earth's
crust.

23. What kind of iron is used for a magnet? For a
magnetic needle ?

Steel.

24. Why does a tin pail so quickly rust out when once the
tin is worn through ?

The iron rusts rapidly in the presence of water, which
favors oxidation.

25. Why is the zinc oxide found in New Jersey red, when
zinc rust is white ?

The oxide in New Jersey is colored by compounds of
iron and manganese.

26. Should we filter a solution of permanganate of potash
through paper ?

(See Chemistry ', page 155, note.)

No. The salt will give up O and corrode the filter.

27. Why is wood, cordage, etc., sometimes soaked in a
solution of corrosive sublimate ?

This salt possesses strong antiseptic properties.

IN CHEMISTRY. 127

28. Why does the white paint around a sink turn black ?

H2S is set free, which, acting on the paint, forms lead
sulphide — the black sulphuret of lead.

29. Why is aluminum, rather than platinum, used for
making the smallest weights ?

Because of its bulk as compared with that of platinum.

30. How would you detect the presence of iron particles in
black sand ?

By a magnet.

31. Which metals can be welded "t

(See Philosophy, page 37.)
Iron and platinum.

32. When the glassy slag from a blast-furnace has a dark
color, what does it show ?

It might be anticipated that the appearance of the slag
would convey to the experienced eye some useful infor-
mation with respect to the character of the ore and the
general progress of the smelting operation. A good slag
is liquid, nearly transparent, of a light grey color, and has
a fracture somewhat resembling that of limestone. A
dark slag shows that much of the oxide of iron is escap-
ing unreduced. Streaks of blue are commonly found
when ores containing sulphur are being smelted, possibly
from the presence of a substance similar to ultramarine,
the constituents of which are all present in the slag.
Again, the slags obtained in smelting ores containing tita-
nium generally present a peculiar blistered appearance. —
BLOXAM.

128 ANSWERS TO PRACTICAL QUESTIONS

33. In welding iron the surfaces to be joined are some-
times sprinkled with sand. Explain.

The silica acts as a flux with the oxide upon the sur-
face and lays bare the metal for welding.

34. What is the difference between an alloy and an amal-
gam ?

An amalgam is composed of mercury and some other
metal. An alloy consists of any metals whatever.

35. Steel -articles are blued to protect from rusting, by
heating in a sand-bath. Explain.

A thin coating of oxide is. formed on the surface of the
metal.

36. Give the rational formula for copperas and white lead.

1. FeSO4 = FeO,SO3.

2. PbCO3 = PbO,CO2.

37. Why is Hg used for filling thermometers!

(See Philosophy \ page 235.)

Because it is fluid at all ordinary temperatures.

38. What oxide is formed by the combustion 0/"Na, K,
Zn, S, Fe, Pb, Cu, P, etc. ? Which are bases ? Acids ?
Give the common name of each.

(i). Na2O is formed when Na oxidizes in dry air, or
oxygen at a low temperature. This takes up water with
great avidity, forming HNaO (NaHO), sodium hydroxide.
Na2O2 is made when Na is heated to 200° C. HNaO is
the caustic soda of commerce, and is an alkaline base.

IN CHEMISTRY. 129

(2). K in a similar manner, depending upon the tem-
perature, forms K2O, K2O2, and K2O4. The first, with
water, forms the ordinary caustic potash, HKO, of com-
merce. It is an alkaline base.

(3). ZnO is the only known oxide of zinc. It forms
salts.

(4). Seven compounds of S and O are known, but only
two are of interest — the familiar anhydrides, SO2 and
S03.

(5). The oxides of iron are four in number: (i) the
monoxide, or ferrous oxide, FeO, from which the green
ferrous salts are derived ; (2) the sesquioxide, or ferric
oxide, Fe2O3, yielding the yellow ferric salts; (3) the
magnetic or black oxide, Fe3O4, which does not form any
definite salts ; (4) ferric acid, H2FeO4, a weak acid, form-
ing colored salts with potassium.

(6). Pb forms two oxides, the monoxide and the di-
oxide. The former is the well known litharge, which is
the base of the lead salts.

(7). Cu has two oxides — the cuprous (Cu2O) and
cupric (CuO), both of which form salts, thus giving rise
to two series, the cuprous and the cupric salts. The two
oxides are commonly known as the red and the black.

(8). Phosphorus forms two oxides, phosphorous anhy-
dride (P2O3) and phosphoric anhydride (P2O5).

39. Is charcoal lighter than H2O ?

Charcoal appears at first sight to be lighter than
water, as a piece of it floats on the surface of this liquid ;
this is, however, due to the porous nature of the charcoal,
for if it be finely powdered it sinks to the bottom of the
water. — ROSCOE.

13° ANSWERS TO PRACTICAL QUESTIONS

40. Name the vitriols.

The compounds of sulphuric acid and oil of vitriol,
commonly called " the vitriols," are as follows :

1. Sulphate of iron, Green vitriol.

2. Sulphate of copper, Blue vitriol.

3. Sulphate of zinc, White vitriol.

41. Is Mg a monad or a dyad ? Zn.?

Mg belongs to the zinc class of metals which comprises
magnesium, zinc, cadmium, and indium. These are all
dyads.

42. Name some dibasic acid.
Sulphuric acid, carbonic acid, etc.

43. Name a neutral salt. An acid salt.

(See Chemistry, page 128, note.)

44. Calculate the percentage of water contained in crystal*
lized copper sulphate. Sodium sulphate. Calcium sulphate.
Alum.

(i). CuSO«, sH.O = 249.5.

5HaO = 90.
Hence, ,V9°B = .36 = 36 % of copper sulphate is water.

(2). NaaSO,, ioHaO = 322.
ioH2O = 180.
Hence, ||§ = .55 = 55 % of sodium sulphate is water.

(3). CaSO4, 2HaO = 172.
2H2O = 36.
Hence, rys = -20 = 20 % of gypsum is water.

(4). AlaKs, 4SO4 + 24HaO = 949.
24H3O = 432.
Hence, -JJf = .45 = 45 % of potash alum is water.

IN CHEMISTRY. 1 3 l

45. What is the test for Ag ? Cu ?

Ag can be easily detected when in solution by the pre-
cipitation of the white curdy chloride, insoluble in H2O
and HNO3, and soluble in H3N : the metal can be
obtained in malleable globules before the blowpipe, and
is reduced from its solutions by Fe, Cu, P, and Hg. Ag
is estimated quantitatively either as the chloride or as
the metal.

Copper may be tested (i) by the black insoluble sul-
phide ; (2) by the blue hydrate turning black on heating;
(3) by the deep blue coloration with ammonia ; (4) by
the deposition of red metallic copper upon a bright sur-
face of iron placed in the solution.

46. What weight of crystallized "tin salts" (SnCl2,
2H2O) can be prepared from one ton of metallic tin?

Sn : SnCla, 2HaO : : 2000 Ibs. : x.

118 : 225 : : 2000 Ibs. : x.

118 x = 450000 Ibs.

•*• = 3813-56 Ibs. (SnCla,2HaO).

47. ioo parts by weight of silver yield 132.8+ parts of
silver chloride. Given the combining weight of chlorine,
required that of silver.

x : 35.5 : : ioo : 32.8 + .
328 x = 3550.
x - 108 + .

48. What is the composition of slacked lime 1

(See Chemistry, page 137.)

CaO,H2O.

49. How is ferrous sulphate obtained ? How many tons
of crystals can be obtained by the slow oxidation 0/230 tons
of iron pyrites containing 37.5 per cent, of sulphur ?

(See Chemistry, page 155, and Key, page 60 ; Question 33.)

I32 ANSWERS TO PRACTICAL QUESTIONS

Find (i) how much S there is in the given weight of
iron pyrites ; (2) how much ferrous sulphate could be
made from that amount of S, if it were all oxidized,
(i). 230 tons x .375 = 86.25 tons (S).

(2). S : FeSO4, 7HaO : : 86.25 tons : x.
32 : 278 : : 86.25 tons : x.

32 x = 23977.5 tons.

x = 749.296 tons (FeSO«, 7HaO).

50. Required $w tons of soda crystals ; what will be the
weight of salt and pure sulphuric acid needed'}

Find (i) how much Na there is in 500 tons of " soda,"
and (2) how much NaCl would be needed to furnish that
amount of the metal in case all were utilized.

(i). Naa : NaaCO3,ioHaO : : x : 500 tons.
46 : 286 : : x : 500 tons.

286 x = 23,000 tons.

x = 80.42- tons (Na).

(2)- sis °f any amount of NaCl is Na ; hence, to furnish 80.42 tons of Na
would require ||§ x 80.42 tons = 204.546 tons (NaCl).

(3). By comparing the atomic weights of the substances it will be seen
that for 46 parts of Na there must be 98 of pure HaSO«.. ff x 204.546 tons =
435.771 tons (H,SO«).

51. Describe the uses of lime in agriculture.

(See Key, page 51, Question 12.)

52. How many tons of oil of vitriol, containing 70 per
cent, of pure acid (H2SO4), can be prepared from 250 tons
of iron pyrites, co?itaining 42 per cent, of sulphur 1 •

(i). (See Question 49.) 250 tons x .42 = 105 tons (S).

(2). S : H2SO4 : : 105 tons : x.
32 : 98 : : 105 tons : x.
32 x = 10290 tons.

x = 321.56 tons (H2SO«).

(3). If 321.56 tons (H2SO«) is 70 % of the given oil of vitriol, the entire
amount would be 321.56 tons x Vr = 459-28 tons (oil of vitriol).

IN CHEMISTRY. 133

1. How would you prove the presence of tannin in teal

By adding a few drops of a solution of ferrous sulphate.
This would form a dark precipitate of iron tannate.

2. How would you test for Fe in a solution ?

(See Miller's Inorganic Chemistry^ page 525.)

A solution of nutgalls will give a bluish-black, inky pre-
cipitate. The ferrous- or proto-salts are distinguished by
their light green color, and by their solutions giving (i) a
white precipitate, with caustic alkalies ; (2) a light blue
precipitate, with potassium ferrocyanide, which rapidly be-
comes dark : whilst the ferric- or per-salts are yellow-col-
ored, and their solutions yield (i) a deep reddish-brown
precipitate, with the caustic alkalies; and (2) a deep blue
precipitate (Prussian blue), with potassium ferrocyanide.

3. Why can we settle coffee with an egg ?

The albumen of the egg coagulates by heat, and en-
tangling the particles of coffee, mechanically carries them
to the bottom.

4. How would you show the presence of starch in a
potato ? ^

A solution of iodine will form the blue iodide of starch.

5. Why is starch stored in the seed of a plant?
For the growth of the young plant.

6. Why are unbleached cotton goods dark-colored?

Because of the dirt gathered in the process of manufac-
ture. The cotton balls are snowy white.

134 AN8WEBS TO PRACTICAL QUESTIONS

7. Why do beans, rice, etc., swell when cooked'}
By the bursting of the starch granules.

8. Why does decaying wood darken ?

By the formation of humus which contains carbon in
excess.

9. Why does smoke cure hams ?

The creosote of the smoke has powerful antiseptic
properties.

10. How would you show that C exists in sugar1}

By the experiments described in the Chemistry on page
117, note ; page 190, note ; and page 191 in the formation
of caramel.

1 1. Why do fruits lose their sweetness when over-ripe ?

(See Miller's Organic Chemistry, page 875.)

The vegetable acid contained in the fruit when green,
oxidizes as the ripening process continues, O being ab-
sorbed and CO 2 evolved. If this continues too long, the
sugar itself becomes oxidized.

12. Why does maple-sap lose its sweetness when the leaf
starts ?

The sugar of the sap is applied to the wants of the
growing tree.

13. Should yeast-cakes be allowed to freeze ?
A cold of 32° will kill the ferment.

IN CHEMISTRY. 135

14. Why will wine sour if the bottle be not well corked ?

The presence of air will cause the continuation of the
oxidizing process into the second or acetic stage.

15. Why can vinegar be made from sweetened water and
brown paper ?

The paper acts as a ferment, while the sugar or mo-
lasses is oxidized into alcohol and thence into acetic acid.

1 6. Why should the vinegar-barrel be kept in a warm
place ?

Heat promotes chemical change.

17. Why does " scalding" check the "working" of pre-
serves ?

The ferment which causes the fermentation is killed by
the heat.

1 8. Is the oxalic acid in the pie-plant poisonous ?

It is neutralized by the alkaline base, with which it is
combined in the plant.

19. How may ink-stains be removed1!

By a solution of oxalic acid, forming an iron oxalate
which is soluble in water, and hence may be washed out.

20. Why is leather black on only one side ?

(See Chemistry^ page 211.)

The solution of copperas, which blackens the leather, is
applied on only one side.

136 ANSWERS TO PRACTICAL QUESTIONS

21. Why do drops of tea stain a knife-blade ?

(See Chemistry, page 211.)

The tannic acid of the tea combines with the iron,
forming an iron tannate.*

22. Why will not coffee stain it in the same way ?

(See Miller's Organic Chemistry, page 549.)

The modification of tannin contained in coffee, unlike
that in tea, turns a solution of ferrous sulphate green,
and will not precipitate one of gelatin.

23. Why does writing-fluid darken on exposure to the
air?

(See Chemistry, page 262.)

It absorbs O, the iron changing to ferric oxide.

24. What causes the disagreeable smell of a smoldering
wick ?

A volatile substance, termed acrolein, is produced in
the decomposition of the oil.

25. Why does ink corrode steel pens ?

The free sulphuric acid of the ink combines with the
iron of the pen.

26. How does a bird obtain the CaCO3/0r its eggshells ?

(See chemistry of a hen's egg in Fireside Science.)

A common hen's egg is 95 per cent, carbonate of lime,

* The tannic acid of the tea tans the albumen of the milk used in seasoning
the tea, forming flakes of real leather. It has been calculated that an average
tea-drinker, in this way, makes and drinks enough leather each year to make
a pair of shoes. The albumen of milk uniting with the tannin acid of tea.
softens its flavor. This is generally preferred to the harsh, clear beverage.

IN CHEMISTRY. 137

one per cent, phosphate of lime and magnesia, and two
per cent, animal matter. The shell would weigh over
100 grains, so that a hen laying 100 eggs in a season
would require nearly i J Ibs. of CaCO3. The hen must
in part secrete this from her food, and in part gather it
from the sand, pebbles, etc., she picks up amid her inces-
sant scratching and searching.

27. Why will tallow make a harder soap than lard?
Tallow contains more palmitin, and less olein, than lard.

28. Why does new soap act on the hands more than old ?

The spent lye, which contains the excess of alkali,
gradually separates from the soap, leaving only the salts
in which the alkali is neutralized by the fatty acids. Also
a more complete combination takes place, whereby some
free alkali is taken up by the acids, perhaps before un-
combined. The former statement is especially true in
the case of soft or home-made soap.

29. What is the shiny coat on certain leaves and fruits ?
A species of wax secreted by the plant.

30. Why does turpentine burn with so much smoke ?
Because it contains an excess of carbon.

31. Why is the nozzle of a turpentine bottle so sticky ?

The turpentine on exposure to the air oxidizes, turning
to rosin.

32. Why does kerosene give more light than alcohol?

It contains more carbon, which, when heated in the
flame of the burning H, gives out a white light.

I38 ANSWESS TO PRACTICAL QUESTIONS

33. What is the antidote to oxalic acid ? Why ?
Magnesia or chalk, forming an insoluble oxalate.

34. Would you weaken camphor spirits with water ?

(See Chemistry, page 117.)

No ; since camphor is insoluble in dilute alcohol. The
principle is the same as that of the precipitation of lead
from dilute oil of vitriol.

35. WJiat is the difference between rosin and resin ?

Rosin is an oxidized resin. Rosin is a species, and
resin a genus.

36. Why does skim-milk look blue and new milk white ?

The globules of butter contained in new milk reflect
the light, and so make it look white ; but when they are
removed, by the separation of the cream, more light is
transmitted, and only the blue is reflected to the eye.

37. Why does an ink-spot turn yellow after washing with
soapl

The free alkali of the soap combines with the tannic
acid of the ink, leaving the oxide of iron (ferric oxide),
which stains the cloth yellow.

140

ANSWERS TO PRACTICAL QUESTIONS

IN CHEMISTRY.

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ANSWERS

T O T'H E

PRACTICAL QUESTIONS

IN THE

FOURTEEN WEEKS IN HUMAN PHYSIOLOGY.

38. — i. Why does not a fall hurt a child as much as it
does a grown person ?

The bones of a child are largely cartilaginous, and so
do not transmit a shock, or readily yield to a blow. They
are also well padded with fat.

2. Should a young child ever be urged to stand or walk ?

No ; bow-legs are often caused by the premature use
of the lower limbs in standing or walking. Nature is the
best guide in such matters.

3. What is meant by " breaking one's neck ? "

The dislocation of the vertebrae and consequent injury
of the spinal cord.

4. Ought chairs or benches to have straight backs ?

The backs should conform to the natural shape of the
spine. This tends to prevent curvatures and other dis-
tortions of the vertebral column.

144 ANSWERS TO PRACTICAL QUESTIONS

5. Ought a child's feet to dangle from a high chair ?

The position is as unnatural and painful for a child as
for a grown person.

6. Why can we tell whether a fowl is young by pressing
on the point of the breast-bone ?

Because that part of the breast-bone is not ossified in
a young fowl.

7. What is the use of the marrow in the bones ?

It contains the blood-vessels carrying material for the
growth of the bone, and also diffuses any shock which
the bone may receive.

8. Why is the shoulder so often put out of joint ?

Because of the shallowness of the socket in the
scapula.

9. How can you tie a knot in a bone ?

By removing the mineral matter and thus softening a
rib-bone, a knot can be easily tied in it.

10. Why are high pillows injurious?

They elevate the head, and so give an unnatural posi-
tion to the spine. For the pads between the vertebrae to
assume their proper shape during the night they should
be relieved of all pressure.

11. Is the " Grecian bend" a healthy position ?

The natural position is the only healthy one. The
distortion known as the " Grecian bend " contracts the
chest, changes the outline of the spine, and diminishes
the vitality of the system.

IN HUMAN PHYSIOLOGY. 145

12. Ought a boot to have a heel-piece ?

A low and broad heel-piece probably aids in walking :
a narrow or high one weakens and enlarges the ankle,
produces bunions, corns, etc., by throwing the weight for-
ward upon the toes, and makes the gait exceedingly
ungraceful.

13. Why should one always sit and walk erect ?

Because then all the organs are in their natural
position.

14. Why does a young child creep rather than walk ?

(See Physiology, page 50.)

Its bones not yet being fully ossified, nature teaches it
not to bear its weight upon them. Besides, it has not yet
learned the difficult art of balancing itself.

56. — i. What class of lever is the foot when we lift a
weight on the toes ?

The third class. The ankle-joint is the fulcrum, the
weight is at the toes, and the power is in front of the
ankle, where the muscle which lifts the toes (the extensor
digitorium) is attached to the foot.

2. Explain the movement of the body backward and for-
ward, when resting tipon the thigh-bone as a fulcrum.

The weight is at the center of gravity of the head and
trunk, high above the hip joints, where the fulcrum is
situated. The flexor muscles of the thigh are the power,
and act close to the fulcrum. The weight is sometimes
directly over the fulcrum, and may be on any side of it.

146 ANSWERS TO PRACTICAL QUESTIONS

This seems to the author to be an example of the first or
second class of lever. Huxley gives it as an illustration
of the third class.

3. What class of lever do we use when we lift the foot
while sitting down ?

The third class. The fulcrum is the knee-joint ; the
weight is at the center of gravity of the foot and leg, and
the power is applied by the ligament which passes over
the patella.

4. Explain the swing of the arm from the shoulder.

(See Physiology, page 48.)

The third class. The fulcrum is the shoulder-joint ;
the weight is at the center of gravity of the arm and
hand, and the power is applied by the biceps or triceps
muscle at its attachment near the elbow.

5. What class of lever is used in bending our fingers ?

The fulcrum is at the junction of the finger with the
palm ; the weight is at the center of gravity of the finger,
and may play about the fulcrum as stated in second
question. It is the third class of lever, especially when
force is exerted at the extremity of the fingers.

6. What class of lever is our foot when we tap the ground
with our toes ?

(See Physiology, Fig. 14, £.)

The first class. The weight is at the toe when the
force is exerted ; the fulcrum is at the ankle ; and the
power is applied by the gastrocnernius muscle at its
attachment to the heeh

IN HUMAN PHYSIOLOGY. 147

7. What class of lever do we use when we raise ourselves
from a stooping position ?

The third class. See second question. If we are
attempting to lift a heavy burden, the bones act on the
principle of the toggle-joint. " When one stoops to take
a heavy weight upon his back or shoulder, he puts both
the knee and the hip-joints into the condition that the
toggle-joint is when it is bent; and then as he straightens
up, the weight is raised by an action of the joints pre-
cisely similar to that of the toggle-joint in machinery.
In the case of the knee, the straightening of the joints is
done by the muscles on the front part of the thigh, that
draw up the knee-pan with the tendon attached to it.
This is using the principle of the toggle-joint in pressing
upward. It is also sometimes used in pressing downward.
In crushing anything with the heel, we give great force to
the blow on the principle of the toggle-joint, by flexing
the knee and straightening the limb as we bring down the
heel upon the thing to be crushed. In pushing anything
before us, we bend the elbow as preparatory to the act,
and then thrust the arm out straight, thus exemplifying
the toggle-joint. The horse gives great force to his kick
in the same way. The great power exerted by beasts of
draught and burden is to be referred very much to the
principle of the toggle-joint. When a horse is to draw a
heavy load, he bends all his limbs, especially the hinder
ones, and then as he straightens them, he starts the load.
In this case the ground is the fixed block of the mech-
anism, the body of the horse to which the load is attached
is the movable one, and his limbs are so many toggle-
joints. By this application of the principle, we see
draught horses move very heavy loads." — HOOKER'S Physi-

14- ANSWEMS TO PRACTICAL QUESTIONS

ology. " So (admitting fable to be fact), when the farmer,
in answer to his petition for assistance, was commanded
by Hercules to exert himself to raise his wagon from the
pit, he placed his shoulder against the wheel, and draw-
ing his body up into a crouching attitude, whereby all his
joints were flexed, and making his feet the fixed points,
by a powerful muscular effort, he straightened the toggle-
joints of his limbs, and the wheel was raised from its bed
of miry clay. His horses at the same moment extending
their joints, the heavily laden wagon was carried beyond
the reach of further detention." — GRISCOM.

8. What class of lever is the foot when we walk ?

•
In the first stage it is clearly the second class. (See

Physiology, page 47, Fig. 18.) The fulcrum is the ground
on which the toes rest ; the power is applied by the gas-
trocnemius muscle (see Fig. 14, k] to the heel ; the
resistance is so much of the weight of the body as is
borne by the ankle-joint of the foot, which of course lies
between the heel and the toes.

9. Why can we raise a heavier weight with our hand
when lifting with the elbow than from the shoulder ?

Because we bring the fulcrum nearer the power. In
the former case it is at the elbow ; in the latter, at
the shoulder.

10. What class of lever do we employ when we are hop-
ping, the thigh-bone being bend up toward the body and not
used?

In this case the fulcrum is at the hip-joint. The power
(which may be assumed to be furnished by the rectus

IN HUMAN PHYSIOLOGY. 149

muscle * of the front of the thigh) acts upon the knee-
cap ; and the position of the weight is represented by
that of the center of gravity of the thigh and leg, which
will lie somewhere between the end of the knee and the
hip. — HUXLEY.

n. Describe the motions of the bones when we are using
a gimlet.

The radius rolls on the ulna at the elbow, while the
ulna rolls on the radius at the wrist. The two combined
produce a free, rotary motion.

12. Why do we tire when we stand erect ?

(See Physiology, page 49.)

Because so large a number of muscles must be in con-
stant action to maintain this position.

13. Why does it rest us to change our work ?

We thereby bring into use a new set of muscles.

14. Why and when is dancing a beneficial exercise ?

When dancing is performed out-of-doors, or in a well-
ventilated room and at proper hours, it is doubtless a
beneficial exercise, since it employs the muscles and
pleasantly occupies the mind. Late at night, in a heated
room, with thin clothing and exciting surroundings, it is
simply a dangerous dissipation, ruinous to the health, alike
of body and soul.

* This muscle is attached above to the haunch-bone or ileum, and below
to the knee-cap. The latter bone is connected by a strong ligament with the
tibia.

15° ANSWERS TO PRACTICAL QUESTIONS

15. Why can we exert greater force with the back teeth
than with the front ones ?

(See Physiology, page 49.)

The lower jaw is a lever of the second class. In the
former case the resistance to be overcome, /". e., the
weight, is situated much nearer the power.

1 6. Why do we lean forward when we wish to rise from
a chair?

(See Philosophy, pages 57-8.)

In order to bring the center of gravity over the feet.

17. Why does the projection of the heel-bone make walking
easier ?

(See Frontispiece, and also Fig. 18 in Physiology?)

It brings the power further from the fulcrum or weight.

1 8. Does a horse travel easier over a flat than a hilly
country 1

No. The variety of travel in a hilly country, other
things being equal, tends to rest the horse, and enable
him to better endure the fatigue of the journey.

19. Can you move your upper jaw?

All the bones of the face, except the lower jaw, are
firmly and immovably articulated with one another and
with the cranium. — LEIDY.

20. Are people naturally right or left-handed?

•Many persons are naturally either right or left-handed ;
but most can and should learn to use either hand with
equal facility.

IN HUMAN PHYSIOL OGY. IS1

21. Why can so few persons move -their ears by if he
muscles ?

Perhaps, because of lack of practice ; more probably,
however, the muscles (see Physiology, p. 65 and Fig. 14)
are developed in few persons.

22. Is the blacksmith's right arm healthier than the left?

By no means. Strength is not essential to health.
The right arm may be stronger, but the functions of the
left may be as active and well-performed.

23. Boys often, though foolishly, thrust a pin into the
flesh just above the knee. Why is it not painful 1

The muscles of the leg there end in tendons, which are
insensible.

24. Will ten minutes practice in a gymnasium answer for
a day's exercise ? .

Spasmodic or violent exercise is not beneficial. It
should be comparatively quiet, gentle, and continuous to
produce the best effect. Moreover, the vitalizing influ-
ences of the sun and pure air demand that we should
exercise out-of-doors.

25. Why would an elastic tendon be unfitted to transmit
the motion of a muscle ?

Force would be lost by its transmission through an
elastic medium.

26. When one is struck violently on the head, why does
he instantly fall ?

The body is kept erect only by the constant exercise

152 ANSWERS TO PRACTICAL QUESTIONS

of many muscles. These perform their functions through
the unconscious action of the brain and spinal cord. A
blow paralyzes the nervous system, the muscles at once
cease to act, and the body falls by its weight.

27. What is the cause of the difference between light and
dark meat in a fowl?

The amount of blood which circulates through differ-
ent parts of the body. The organs of a fowl which are
used the most become the darkest.

79. i. If a hair be plucked out, will it grow again ?

Yes. A new hair will always grow out so long as the
papilla at the bottom of the follicle remains uninjured.

2. What causes the hair to " stand on end" when we are
frightened?

(See Physiology, page 65.)

" Many of the unstriated muscular fibres from the true
skin pass obliquely down from the surface of the dermis
to the under side of the slanting hair-follicles. The con-
traction of these fibres erects the hairs, and by drawing
the follicles to the surface and drawing in a little point
of the skin, produces that roughness of the integument
called "goose-skin," or Cutis Anserina. The standing
on end of the hair of the head, as the result of extreme
fright, may be partly due to the contraction of such
fibres, as well as to the action of the occipito-frontalis
muscle." — CUTTER.

3. Why is the skin roughened by riding in the cold?

(See Physiology ', page 65 ; also Answer to Question 2.)

IN HUMAN PHYSIOLOGY. 153

4. Why is the back of a washer-woman's hand less
water-soaked than the palm ?

The difference depends upon the relative abundance
of the oil-glands in different parts of the body.

5. What would be the length of the perspiratory tubes
in a single square inch of the palm, if placed end to end?

(See Physiology, page 72. 2,800 x TV in. =2££e in.= 14 ft. 7 in.— Answer.)

6. What colored clothing is best adapted to all seasons ?

Light-colored clothing is cooler in summer and warmer
in winter.

(See Physiology, page 77 ; Natural Philosophy, page 246.)

7. What is the effect of paint and powder on the skin ?

They fill the pores of the skin, and thus prevent the
passage of the perspiration. Moreover, they often con-
tain substances which are poisonous, and being carried
in by the absorbents cause disease.

(See Physiology, page 73.)

8. Is water-proof clothing healthful for constant wear ?

No. It retains the insensible perspiration by which
waste matter is being constantly thrown off from the
system.

9. Why are rubbers cold to the feet ?

They retain the insensible perspiration. The moisture
which gathers absorbs the heat of the feet, and readily
conducts it from the body.

154 ANSWERS TO PRACTICAL QUESTIONS

10. Why does the heat seem oppressive when the air is
moist ?

In the moisture-laden atmosphere, the evaporation of
the insensible perspiration from the surface of the body
goes on slowly. The heat, which would otherwise pass
off through the pores, is retained in the system.

1 1. Why is friction of the skin invigorating after a cold
bath?

The friction produces heat, expands the veins, etc., on
the surface, and, calling the blood in that direction, pro-
duces a vigorous circulation. In other words, it causes a
reaction.*

(See Physiology, page 75.)

12. Why does the hair of domestic animals become rough-
ened in winter ?

(See Question 2.)

The effect is beneficial, since more air — a non-conduc-
tor of heat — is retained by the hair, and thus the rough

* " Strength in the living body is maintained by the full but natural exercise
of each organ ; and as we have seen, the actions of these portions of the ner-
vous system is made dependent upon influences conveyed to them by the
sensitive nerves distributed over the various parts of the body. And among
these the nerves passing to the skin are the chief. The full access of all
healthful stimuli to the surface, and its freedom from all that irritates or im-
pedes its functions, are the first external conditions of the normal vigor of this
nervous circle. Among these stimuli, fresh air and pure water hold the first
place. Sufficient warmth is second. The great, and even wonderful advan-
tages of cleanliness are partly referable to the direct influence of a skin
healthily active, open to all the natural stimuli, and free from morbid irrita-
tion, upon the nerve-centres of which it is the appointed excitant. This influ-
ence is altogether distinct from those cleansing functions which the healthy
skin performs for the blood ; and in any just estimate of its value is far too
important to be overlooked."— HINTON.

7JV HUMAN PHYSIOLOGY. 155

winter-coat of an animal is warmer than its smooth sum-
mer-coat.

13. Why do fowls shake out their feathers erect before
they perch for the night ?

(See Question 12.)

This is a wise provision of Nature to protect the fowl
against the chilliness of the night. More air is confined
by the roughened feathers, and thus the internal heat of
the bird is prevented from radiating.

14. How can an extensive burn cause death by congestion
of the lungs ?

The insensible perspiration is stopped upon the burned
surface, and the excretions are sent to the lungs, which
are overworked and overloaded by the excess.

(See Physiology, page 74.)

15. Why do we perspire so profusely after drinking cold
water ?

The vital organs being chilled for an instant, the blood
is sent to the surface, a reaction is produced, the skin
acts more vigorously as an excretory organ, and the
insensible perspiration is thrown off more rapidly.

1 6. What are the best means of preventing skin diseases,
colds, and rheumatism ?

The skin should be kept in a healthy state by bathing,
rubbing, etc. Exposure to sudden changes of tempera-
ture should be avoided as far as possible. Flannel

156 ANSWERS TO PRACTICAL QUESTIONS

worn next the skin, in all seasons of the year, is an
excellent precaution against unavoidable exposure.

17. What causes the difference between the hard hand of
a blacksmith and the soft hand of a woman ?

The varying thickness of the cuticle.

(See Physiology, page 62.)

1 8 . Why should a painter avoid getting paint on the palm
of his hand?

(See Physiology, page 73.)

19. Why should we not use the soap or soiled towel at a
hotel?

Because of the danger of contracting disease through
the absorbents 01 the skin. (See Physiology, p. 73.)
There is a similar danger in using a hair-brush or a
comb at a barber shop.

20. Which teeth cut like a pair of scissors ?

The "back-teeth," as we commonly call them, when
moved laterally, cut somewhat in this way. In chewing
the food all the "tront teeth" act like scissors, as may
be readily seen by noticing their movements.

2 1 . Which like ct chisel ?

The incisors, or four front teeth of each jaw, have
knife edges ; the canine teeth have wedge-shaped edges ;
the bicuspids and molars have broader crowns. We can
work the jaws so as to make the front-teeth either pierce
like wedges or cut like scissors.

IN HUMAN PHYSIOLOGY. 157

22. Which should be clothed the warmer, a merchant or
a farmer ?

The merchant is liable to more sudden and violent
changes of temperature, and his body is less likely to be
hardened by exposure and habit to resist them.

23. Why should we not crack nuts with our teeth ?

The brittle enamel is very liable to crack, and once
broken can never be restored.

24. Do the edges of the upper and lower teeth meet1}

(See Question 21.)

25. When fatigued, would you take a cold bath ?

Certainly not. The system is not vigorous enough to
produce a reaction, and the effect might be dangerous.

26. Why is the outer surface of a kid glove finer than the
inner ?

This illustrates the difference in texture between the
cutis and cuticle ; the dermis and epidermis.

27. Why will a brunette endure the sun's rays better than
a blonde ?

(See Physiology, page 63.)

The skin is perhaps of a coarser texture, and not so
sensitive to heat. May it not be also that the black pig-
ment absorbs the heat and radiates it again rather than
transmits it directly to the internal organs ? It has also
been suggested that there is an increased flow of blood
in the darker skin, and hence increased perspiration.

158 ANSWERS TO PRACTICAL QUESTIONS

28. Does patent-leather form a healthful covering for the
feet?

No. The pores of the leather are partly rilled, and
hence the insensible perspiration is largely restrained.

29. Why are men more frequently bald than women ?

This is the effect of the close, unventilated head-cover-
ing commonly worn by men.

30. On what part of the head does baldness commonly
occur ?

On that part most fully covered by the hat or cap.

31. What does the combination in our teeth of canines
and grinders suggest as to the character of our food?

That we are to eat a mixed diet of vegetable and ani-
mal food.*

* u The question of the use of animal or vegetable food may well be re-
mitted to the arbitrament of nature, as expressed in the desires ; by which it
would be victoriously decided, in all such climates as ours, in favor of the
flesh-eater. But the sufficiency of vegetable food, if widely varied, to main-
tain health and even strength, is not to be questioned, for those who like it.
When we hear that the ancient Persians lived a good deal on water-cress, we
naturally connect in our minds their physical inferiority with the poverty of
their diet ; but finding, on the other hand, that the Romans, in the best period
of the Republic, largely sustained themselves on turnips, and that degeneracy
came in as turnips went out, we are compelled to reconsider our opinion. In
brief, an exclusively vegetable food may be best suited to those by whom it
really is preferred. Children in this respect exhibit the greatest difference ;
some, with manifest advantage, eat meat in large quantity — others can hardly
be prevailed on to taste it, and yet retain perfect vigor. Similar differences,
in all probability, exist among adults; but a vegetarianism self-imposed
against the promptings of desire, would tend, as a vigorous writer says, to
make us l not the children, but the abortions of Paradise.' "— HINTON.

IN HUMAN PHYSIOLOGY. 159

32. Is a staid, formal promenade suitable exercise?

No. There is an intimate relation between the brain
and the muscles. The mind should be pleasantly em-
ployed to obtain the full effect of any exercise. The
sports of children are often the very perfection of health-
ful gymnastic exercises ? *

33. Is there any danger in changing the warm clothing of
pur daily wear for the thin one of a party ?

Very great. The body is not as well protected as
usual against a sudden change of temperature, as in
going from a heated-room to the carriage, and a cold is
often the consequence. This may lay the foundation of,
or prepare the way for, fatal disease.

34. Should we retain our overcoat, shawl, or furs, when
we come into a warm room ?

No. The body will become over-heated, the pores be
opened, and the skin be rendered susceptible to the
change of temperature when we return into the open
air.

35. Which should bathe the oftener, students or out-door
laborers ?

* " The mental operations, like all others, are connected with changes in
the material of the body. In all our consciousness the chemical tendencies
of the substance of the brain come into play, and thus a chain of action is set
up which extends throughout the system. The influence of these brain-
changes is felt wherever a nerve travels, and modifies, invigorates, or de-
praves the action of every part. Experience gives ample proof of this fact to
every one, as in the sudden loss of appetite a piece of bad news will cause, or
in the watering of the mouth excited by the thought of food. And the history
of disease abounds in evidence of a similar kind : hair becoming gray in a
single night from sorrow, milk poisoning an infant from an attack of passion
in the nurse, permanent discoloration of the skin from terror, are among the
instances on record."— HINTON.

l6o ANSWERS TO PRACTICAL QUESTIONS

This depends entirely on circumstances — the amount
of exercise, freedom and character of perspiration, state
of the system, etc. Each case must be decided by it-
self.

36. Is abundant perspiration injurious ?

No. It removes impure matter from the system, and
hence may be beneficial. It may, however, weaken the
body, and frequent hot baths should therefore be taken
only on suitable medical advice.

99. — i. What is the philosophy of the "change of voice"
in a boy ?

Up to the age of fourteen or fifteen, there is little or
no difference in point of size between the larynx of a
boy and that of a girl; but subsequently the former
grows proportionately larger, so that at last, in the adult
male, the vibrating parts or vocal cords are necessarily
longer than in the female. They are also undoubtedly
thicker, perhaps even coarser in structure. From all these
circumstances the adult male voice is stronger, louder, and
of lower pitch than the weaker and higher vocal range
accomplished by the female larynx.

The cause of the difference in quality of the voice,
known as its timbre, is not well known ; but it must
undoubtedly be dependent on physical, that is to say,
structural peculiarities in some part of the laryngeal
apparatus.

The production of the different notes within the com-
pass of any one individual depends upon alterations in
the length and state of tension of the vocal cords, and on
their degree of proximity or separation from one another

IN HUMAN PHYSIOLOGY. id

The higher notes require the vocal cords to be compara-
tively shorter, tighter, and more closely approximated
together; whilst the lower notes demand opposite condi-
tions. A high note, furthermore, implies greater rapidity
in the movement of the air through the glottis ; but the
quantity of air passing is larger during the production of
a low note.

The volume or loudness of the voice depends mainly
on the combination of quantity of air with greater force
of expulsion. Loudness, with clearness, also demands a
peculiar resonance up in the nasal cavities and sinuses.
Lastly, the unnatural or falsetto voice seems also to be
produced by some tensive change effected in the upper
part of the pharynx at the back of the nose : hence it is
called by singers the head voice, in contradistinction to the
ordinary, or chest voice. — MARSHALL.

2. Why can we see our breath on a frosty morning?
The vapor of the breath is condensed by the cold air.

3. When a law of health and a law of fashion conflict,
which should we obey ?

It depends, of course, whether we prefer to be fashion-
able or to be healthy, to obey man or God. With too
many people the former is of far greater importance, and
in selecting an article of dress, few ask or think about
the latter. The consequence is seen in the weakened
frame, the prevalence of disease, and the shortened life.
God's laws written in our bodies cannot be violated with
impunity.

4. If we use a " bunk " bed, should we pack away the
clothes when we first rise in the morning ?

No. They should first be thoroughly aired.

1 62 ANSWERS TO PRACTICAL QUESTIONS

5. Why should a clothes-press be well ventilated ?

The clothes naturally contain the products of the
insensible perspiration, which passing off, pollute the
air of the closet.

6. Should the weight of our clothing hang from the waist
or the shoulder ?

From the shoulder, so as to avoid the constriction of
the compressible organs in the abdomen.

7. Describe the effects of living in an over-heated room.

(i). The body becomes more sensitive to change, and
the susceptibility to colds is greatly increased : (2) the
dry, heated air abstracts the moisture from the skin, ren-
dering it dry, hard, and incapable of performing its nor-
mal functions.

8. What habits impair the power of the lungs ?

Above all others, those qf a leaning posture, tight-
lacing, and ill-ventilation.

9. for full, easy breathing in singing, should ' > we use the
diaphragm and lower ribs or the upper ribs alone ?

Nearly all the inspirations are effected by the move-
ments of the diaphragm and the inferior ribs only. From
time to time a deeper and more complete inspiration
causes the thorax to rise, not simultaneously, but succes-
sively at the base, then at the apex. In the first case the
respiration is diaphragmatic ; when the lower and middle
ribs are raised, it is termed lateral; and lastly, when the
first rib and clavicle take part in the movement, it is

IN HUMAN PHYSIOLOGY. 163

costo-superior or clavicular. In diaphragmatic respira-
tion, as M. Mandl has observed, the larynx is immovable,
the inspiration is easy, without effort, and permits exer-
tion in singing or in gymnastics for a long time and
without fatigue. On the contrary, persons who respire
principally by the upper ribs are easily fatigued, and very
soon out of breath. This is seen in women when the
corset compresses the base of the chest, and in singers
who adopt, on erroneous principles, the bad habit of
clavicular respiration. In this last method of inspiration
the larynx is drawn down by the contraction of the
external muscles, and its action becomes painful. The
effort of the inspiratory muscles rapidly induces fatigue,
and the inspiration, always incomplete, becomes also
more frequent. Diaphragmatic respiration is practised
by mountaineers, gymnasts, and skilful singers — a habit
induced either by instinct, or a well-directed education. —
Wonders of the Human Body.

10. Why is it better to breathe through the nose than the
mouth ?

The air passing through the nostrils becomes filtered
of its coarse impurities, and the chill is taken off before it
strikes against the tender, mucous surfaces of the larynx.

1 1. Why should not a speaker talk while returning home
on a cold night after a lecture ?

The cold air will strike against the vocal apparatus
when inflamed and peculiarly sensitive.

12. What part of the body needs the loosest clothing ?

The abdomen ; because of the delicate organs within,
unprotected by a bony covering.

1 64 ANSWERS TO PRACTICAL QUESTIONS

13. What part needs the warmest ?

The feet, because they are furthest from the center of
heat and motion and most exposed to cold and wet : and
the neck and shoulders, since here are located the deli-
cate organs of voice and respiration.

14. Why is a " spare bed " generally unhealthy ?
Because it is apt to be damp and unventilated.

15. Is there any good in sighing?

(See Physiology, page 91.)

It probably brings up the " arrears " of respiration.

1 6. Ought a hat to be thoroughly ventilated ? How ?

Certainly, as the heated, foul air is injurious. A single
hole at the top is quite insufficient for ventilation.
Several openings should be made on the sides near the
band.

1 7. Why do the lungs of people who live in cities become
of a gray color.

Probably because of the deposition of carbonaceous
particles which penetrate the substance of the tissues.
The coloring is permanent, like tattooing, where india-
ink is pricked beneath the skin.

1 8. How would you convince a person that a bed-room
should be aired ?

Take him from the fresh, pure, invigorating out-door
atmosphere into the close, depressing air of the bed-room,
when first vacated in the morning, and his sense of smell
will satisfy him of the need of ventilation.

IN HUMAN PHYSIOLOGY. 1 65

19. What persons are most liable to scrofula, consump-
tion, etc.

(See Physiology, pages 94-98.)

The victims of lung-starvation.

20. If a person is plunged under water, will any enter
his lungs ?

No. The epiglottis will close involuntarily and pre-
vent the admission of water.

21. Are bed-curtains healthy 1

No. They prevent the free circulation of the air and
confine the waste products thrown off from the body.

22. Why do some persons take "short breaths" after a
mean

The distention of the stomach prevents the free action
of the lungs. If such persons are not given to gluttony,
the lungs are small or the other organs misplaced.

23. What is the special value of public parks ?

They bring fresh air, sunshine, green grass and trees
within the reach of all. They are truly the " breathing-
holes of a city." They are thus of incalculable benefit
both on account of their sanitary and moral influence.

24. Can a per son become used to bad air, so that it will
not injure him ?

The system may come to endure without complaint, but
never fails to inflict full punishment for the infraction of
nature's laws.

1 66

ANSWERS TO PRACTICAL QUESTIONS

25. Why do we gape when we are sleepy ?

(See Question 15.)

The stretching of the nerves may perhaps serve to
restore the equilibrium of the nervous influence, disturbed
by the attention being fixed during the day upon some
absorbing occupation.

26. Is a fashionable waist a model of art in sculpture or
painting ?

The Venus of Milo, in the Louvre at Paris, is the beau-
ideal of symmetry and beauty, yet the form indicates not
a "wasp-waist," but the full, free, flowing outlines of
nature. The sculptor and painter in copying the human
figure can make no improvement on its Divine maker.

27. Should a fire-place be closed*?

(See Physiology, page 100.)

No. It is a most efficient means of ventilation.

28. Why does embarrassment or fright cause a stammerer
to stutter still more painfully ?

Stuttering is mainly a nervous disorder, and hence any
excitement tends to increase the impediment of the
speech.

29. In the organs of voice, what parts have somewhat the
same office as the case of a violin and the sounding-board of
a piano?

(See Philosophy, page 176.)

The pharynx, the mouth, and the nasal passages all act
by resonance to modify the voice.

/2V HUMAN PHYSIOLOGY. 167

129. — i. Why does a dry, cold atmosphere favorably
affect catarrh ?

It tends to diminish inflammation in the mucous mem-
brane lining the nose and nasal passages.

2. Why should we put on extra covering when we }ie
down to sleep ?

The respiration and the circulation are then less active.
The fire in our corporeal stoves being low, we need extra
covering to preserve the warmth of the body.

3. Is it well to throw off our coats or shawls when we
come in heated from a long walk ?

No. We rather need to put on extra clothing at such
times to keep the body from cooling too rapidly. The
best hygienic teachers commend the throwing of a shawl
about the shoulders whenever we sit down to rest after
fatiguing labor.

4. Why are close-fitting collars or neck-ties injurious ?
They impede both respiration and circulation.

5. Which side of the heart is the more liable to inflam*
mation ?

The left ; since that contains the red blood just oxygen-
ated in the lungs.

6. What gives the toper his red nose ?

(See Physiology, pages 125 and 173.)

The congested state of the capillaries.

1 68 ANSWERS TO PRACTICAL QUESTIONS

7. Why does not the arm die when the surgeon ties the
principal artery leading to it ?

The anastomoses of the arteries enable a collateral
circulation to be established, whereby blood is supplied
to the arm.

8. When a fowl is angry, why does its comb redden ?

Because an extra quantity of blood is thrown into that
part of the body.

9. Why does a fat man endure cold better than a lean
one?

Fat is a good non-conductor of heat, and helps to pre-
serve the uniform temperature of the body.

10. Why does one become thin during a long sickness ?

By absorption, the fat of the body is taken up and
used to supply the wants of the system. The old flesh
being renewed with new, vigorous material, after such a
wasting sickness, a person often has better health than
previous to it.

11. What would you do if you should come home "wet
to the skin ?"

One should (i) go into a warm room; (2) remove all
wet garments ; (3) if chilled, take a hot, full- or foot-bath,
and by gentle friction restore the circulation ; (4) put on
dry clothing.

12. When the cold air strikes the face, why does it first
blanch and then flush ?

IN HUMAN PHYSIOLOGY. 169

The muscles and blood-vessels of the surface are con-
tracted by the cold, and the blood is driven back toward
the heart. The reaction which ensues forces the blood
again toward the skin, and this flushes with the incoming
tide. The face is therefore first whitened and then red-
dened.

13. What must be r'he effect of tight lacing upon the circu-
lation of the blood ?

It must, by contracting the blood-vessels, impede the
flow of the blood, and by decreasing the quantity fur-
nished the various organs, injure their action. Thus,
finally, it will impair the quality of the blood.

14. Do you know the position of the large arteries in the
limbs, so that in case of accident you could stop the flow of
blood i

These can be located by examining the cut in Physi-
ology, page 104, or any good chart of the circulation.

15. When a person is said to be "good-hearted" is it a
physical truth ?

The expressions, large-hearted, good-hearted, etc., are
remains of the old idea that the affections are located in
the heart rather than in the brain — the seat of the mind
and all its attributes.

16. Why does a hot foot-bath often relieve the headache1}

(See Physiology, pages 127-8.)

It withdraws blood from the head, and so relieves the
congested state of that organ.

17° ANSWERS TO PRACTICAL QUESTIONS

17. Why does the body of a drowned or strangled person
turn blue ?

The blood is not purified in the lungs, and so blue or
venous blood fills the vessels.

1 8. What are the little " kernels " in the arm-pits ?

(See Physiology, page 123.)

They are the lymphatic glands which sometimes become
swollen.

19. When we are excessively warm, would the thermom-
eter show any rise of temperature in the body ?

(See Physiology, page 119, note.)

Probably not. In health, the average temperature of
the body does not vary more than 2°.

20. What forces besides that of the heart aid in propelling
the blood ?

(See Flint's Physiology— The Circulation ; Cutler's Analytic Anatomy^ etc..
page 166, et seq.)

The elasticity of the arteries and the veins, the force
of capillary attraction in the capillaries, etc-

2 1. Why can the pulse be felt best in the wrist ?

It is, in general, a mere matter of convenience. We
can feel it not only in the radial artery at the wrist, but
in the carotid of the neck, the temporal of the forehead,
the popliteal * in the inner side of the knee, etc.

* If the hollow of the knee of one leg be allowed to rust upon the knee ol
the other one, it may be remarked that the point of the suscended foot moves
visibly up and down at each beat of the pulse.

IN HUMAN PHYSIOLOGY. *7X

22. Why are starving people exceedingly sensitive to any
jar?

The marrow of the bones is absorbed, and hence the
shock of ajar is unbroken. The nervous system is also
weakened by the general prostration.

23. Why will friction, an application of horse-radish
leaves, or a blister relieve internal congestion 1

They bring the blood to the surface of the body, and
so relieve the internal organ.

24. Why are students very liable to cold feet ?

Because the tendency of the blood is toward the head
to supply the waste in that part of the body.

25. Is the proverb that "blood is thicker than water"
literally true ?

(See Draper's Human Physiology^ page 112.)

The specific gravity of the blood varies from 1.050 to
1.059.

26. What is the effect upon the circulation of "holding
the breath ?"

The blood is not oxygenated, the products of waste
accumulate in the system, the circulation is impeded, the
blood-vessels become distended and are liable to burst,
while all the delicate organs, especially the brain, are
oppressed by congestion.

27. Which side of the heart is the stronger ?

The left, which drives the blood to the extremities.

I?2 AtfSWEXS TO PRACTICAL QUESTIONS

28. How is the heart itself nourished ?

The coronary arteries springing from the aorta just
after its origin, carry blood to the muscular walls of the
heart : the venous blood comes back through the coronary
veins, and empties directly into the right auricle.

29. Does any venous blood reach the heart without com-
•Ing through the vena cavcz ?

(See Question 28.)

155. — i. How do clothing and shelter economize food ?

The force which would be converted into heat to pre-
serve the temperature of the body, is saved. The food
needed to supply this amount of force may be reserved
or changed into flesh, or into other forms of force.

2. Is it well to take a long walk before breakfast ?

(See Physiology, page 53.)

A vigorous person in good health and in a healthy
region may do so, but one in ill health, or a malarious
district, needs to be braced with food before taking any
except very light exercise.

3. Why is warm food easier to digest than cold?

Heat favors the chemical change whereby the food is
prepared for assimilation.

4. Why is salt beef less nutritious than fresh ?

(See Physiology, page 155, note.)

The salts and juices of the meat are extracted by the
brine.

IN HUMAN PHYSIO L OGY. 173

5. What should be the food of a man recovering from a
fever?

It should be that which is nutritious, easily digested,
and not over-stimulating. Beef-tea or essence* is gener-
ally commended. As soon as the patient will bear it,
beefsteak, tender, broiled, and not over-done, is most
beneficial.

6. Is a cup of black coffee a healthy close to a hearty
dinner ?

The tannic acid contained in tea and coffee (see Chem-
istry, pp. 211, 215) is neutralized by the milk generally
used with these beverages. In cafe noir, black or
clear coffee, the tannic acid acts unfavorably on the
mucous membrane lining the stomach. Besides, the
coffee, like a dessert, is superfluous, the appetite being
already satisfied. It therefore, both actively and nega-
tively, tends to delay the digestion of the meal. The
glass of wine sometimes taken to aid digestion merely
deadens the sensibility of the stomach, so that the food is
hurried, half-digested, out into the intestines.!

7. Should ice-water be used at a meal ?

Only a person in robust health can endure the shock

* Dr. Martindale gives the following recipe for making this essence :
Cut a quantity of lean beef into small pieces, put it into a strong bottle,
without water, cork it loosely so that the steam can escape, and immerse the
bottle to its neck in a vessel of cold water. Place on the fire and boil for two
hours ; then pour off the essence.

t Mix some bread and meat with gastric juice ; place them in a phial, and
keep that phial in a sand-bath at the slow heat of 98 degrees, occasionally
shaking briskly the contents to imitate the motion of the stomach ; you will
find, after six or eight hours, the whole contents blended into one pultaceous
mass. If to another phial of food and gastric juice, treated in the same way,
you add a glass of pale ale or a quantity of alcohol, at the end of seven or eight
hours, or even some days, the food is scarcely acted upon at all.

174 ANSWERS TO PRACTICAL QUESTIONS

of drinking ice-water at a meal. Indeed, drinking of ice-
water under any circumstances is dangerous and hurtful.
If used at all, it should be carefully and slowly sipped, a
little at a time.

8. Why is strong tea or coffee injurious ?

The tannic acid acts unfavorably on the coatings of
the stomach.* The nervous system is over-stimulated,
and, when the reaction occurs, becomes correspondingly
depressed and weakened. The constant decay of the
body, so essential to its highest activity, is greatly re-
tarded. Wakefulness is often induced, and thus the
organs are deprived of that rest which is absolutely es-
sential.

9. Should food or drink be taken hot ?

The pepsine of the gastric juice, in order to produce its
effect, must have a moderately warm temperature, neither
too hot nor too cold. The gastric juice will not act upon
the food when near the freezing point of water, neither
will it have, any effect if raised to the neighborhood of a
boiling temperature. It must be intermediate between
the two; and its greatest activity is about 100 degrees
Fahrenheit, which is exactly the temperature of the in-
terior of the living stomach. — DALTON'S Physiology, p. 103.

10. Are fruit-cakes, rich pastry, and puddings healthful?

(See BLACK'S Ten Laws of Health, p. 83, et seq.)

They are too concentrated. They are not easily pene-
trated by the juices of the system, and hence are not
quickly digested. They stimulate the appetite, and so

* Tea contains from 14 to 16 per cent, of this astringent substance, and
coffee not over 6 per cent.— YOUMANS.

IN HUMAN PHTSIOL OOT. 175

lead to gluttony. They supply the system with an over-
abundance of nutrition, for which the blood has no use,
and so lead to biliousness and other diseases of the blood
and digestive organs.

1 1. Why are warm biscuit and bread hard of digestion ?

They form a pasty mass,, which the juices of the diges-
tive organs penetrate very slowly.

12. Should any stimulants be used in youth ?

No. The system is then vigorous, and all its* functions
promptly performed. If stimulants are ever used, it
should be when the body needs forcing, as when recover-
ing from disease, or languid with the decay of the natural
powers in old age.

13. Why should bread be made spongy ?

(See Question n.)

14. Which should remain longer in the mouth, bread or
meat?

Bread, since the pepsin is essential to the conversion
of starch into sugar ?

15. Why should cold water be used in making soup, and
hot in boiling meat ?

In the former case, we desire to extract the juices of
the meat ; in the latter, to retain this by quickly coagu-
lating the albumen on the surface of the meat

1 6. Name the injurious effects of over-eating.

(See Physiology, page 151.)

17. Why do not buckwheat cakes, with syrup and butter,
taste as well in July as in January ?

In the winter, the system craves highly carbonaceous

I76 ANSWERS TO PRACTICAL QUESTIONS

food ; in the summer, it relishes cooling, acid drinks, and
an unstimulating diet.

1 8. Why is a late supper, injurious ?

The system is wearied with the clay's labor, and the
stomach is unfitted to undertake the task of digesting a
meal as much as the body is to begin a new day's task
unrefreshed by sleep.*

* " Being allowed for once to speak, I would take the opportunity to set
forth how ill, in all respects, we stomachs are used. From the beginning to
the end of life, we are either afflicted with too little or too much, or not the
right thing, or things which are horribly disagreeable to us ; or are otherwise
thrown into a state of discomfort. I do not think it proper to take up a
moment in bewailing the Too Little, for that is an evil which is never the
fault of our masters, but rather the result of their misfortunes ; and, indeed,
we would sometimes feel as if it were a relief from other kinds of distress if
we were put upon short allowance for a few days. But we conceive our-
selves to have matter for serious complaint against mankind in respect of the
Too Much, which is always an evil voluntarily incurred. What a pity that in
the progress of discovery we cannot establish some means of a good under-
standing between mankind and their stomachs ; for really the effects of their
non-acquaintance are most vexatious. Human beings seem to be, to this day,
completely in the dark as to what they ought to take at any time, and err
almost as often from ignorance as from depraved appetite. Sometimes, for
instance, when we of tfie inner house are rather weakly, they will send us
down an article that we could deal with when only in a state of robust health.
Sometimes, when we would require a mild vegetable diet, they will persist in
the most stimulating and irritating of viands.

" What sputtering we poor stomachs have when mistakes of that kind occur !
What remarks we indulge in regarding our masters ! " What's this, now ? "
will one of us say ; " ah, detestable stuff ! What a ridiculous fellow that man
is ! Will he never learn ? Just the very thing I did not want If he would
only send down a bowl of fresh leek soup or barley broth, there would be
some sense in it :" and so on. If we had only been allowed to give the
slightest hint now and then, like faithful servants as we are, from how many
miseries might we have saved both our masters and ourselves !

" I have been a stomach for about forty years, during all of which time I have
endeavored to do my duty faithfully and punctually. My master, however,
is so reckless, that I would defy any stomach of ordinary ability and capacity
to get along pleasantly with him. The fact is, like almost all other men, he,
in his eating and drinking, considers his own pleasure only, and never once
reflects on the poor wretch who has to be responsible for the disposal of
everything down stairs. Scarcely on any day does he fail to exceed the strict

IN HUMAN PHYSIOLOGY. 177

19. What makes a man " bilious ? "

(See Hall's Health by Good Living, p. in, et seq.)

The liver strains the bile out of the blood. This waste
matter is not withdrawn when the liver is inactive, and
hence the face and eyes become yellow — the cclor of bile,
and the functions all become torpid.

rule of temperance ; nay, there is scarcely a single meal which is altogether
what it ought to be. My life is therefore one of continual worry and fret ; I
am never allowed to rest from morning till night, and have not a moment in
the four-and-twenty hours that I can safely call my own. My greatest trial
takes place in the evening, when my master has dined. If you only saw what
a mess this said dinner is — soup, fish, flesh, fowl, ham, rice, potatoes, table-
beer, sherry, tart, pudding, cheese, bread, all mixed up together. I am ac-
customed to the thing, so don't feel much shocked ; but my master himself
would faint at the sight. The slave of duty in all circumstances, I call in my
friend Gastric Juice, and we set to work with as much good-will as if we had
the most agreeable task in the world before us. But, unluckily, my master
has an impression very firmly fixed upon him that our business is apt to be
vastly promoted by an hour or two's drinking ; so he continues at table
among his friends, and pours down some bottle and a half of wine, perhaps of
various sorts, that bothers Gastric Juice and me to a degree which no one can
have any idea of. In fact, this said wine undoes our work almost as fast as
we do it, besides blinding and poisoning us poor servants into the bargain.
On many occasions I am obliged to give up my task for the time altogether ;
for while this vinous shower is going on I would defy the most vigorous
stomach in the world to make any advance in its business worth speaking of.
Sometimes things go to a mu ch greater length than at others ; and my master
will paralyze us in this manner for hours, not always, indeed, with wine, but
occasionally with punch, one ingredient of which — the lemon — is particularly
odious to us. All this time I can hear him jollifying away at a great rate,
drinking healths to his neighbors, and ruining his own.

" I am a lover of early hours, as are my brethren generally. To this we are
very much disposed by the extremely hard work which we usually undergo
during the day. About ten o'clock, having, perhaps, at that time got all our
labors past, and feeling fatigued and exhausted, we like to sink into repose,
not to be again disturbed till next morning at breakfast-time. Well, how it
may be with others I can't tell ; but so it is, that my master never scruples to
rouse me up from my first sleep, and give me charge of an entirely new meal,
after I thought I was to be my own master for the night. This is a hardship
of the most grievous kind. Only imagine me, after having gathered in my
coal, drawn on my night-cap, and gone to bed, called up and made to take
charge of a quantity of stuff which I know I shall not be able to get off my
hands all night ! Such, O mankind, are the woes which befall our tribe i*
8

178 ANSWERS TO PRACTICAL QUESTIONS

20. What is the best remedy ?

Diet to give the organs rest, and active exercise to
arouse the secretions and the circulation.

2 1. What is the practical use of hunger ?

To prompt us to furnish the body with sufficient food.

22. How can jugglers drink when standing on their
heads ?

Because water does not fall into the stomach by its
own weight, but is conveyed thither from the mouth by
the contraction of the muscular bands of the oesophagus.

consequence of your occasionally yielding to the temptations of " a little
supper." I see turkey and tongue in grief and terror. Macaroni fills me
with frantic alarm. I behold jelly and trifle follow in mute despair. O that
I had the power of standing beside my master, and holding his unreflecting
hand, as he thus prepares for my torment and his own ! Here, too, the old
mistaken notion about the need of something stimulating besets him, and
down comes a deluge of hot spirits and water, that causes me to writhe in
agony, and almost sends Gastric Juice off in the sulks to bed. Nor does the
infatuated man rest here. If the company be agreeable, one glass follows
another, while I am kept standing, as it were, with my sleeves tucked up,
ready to begin, but unable to perform a single stroke of work.

" I feel that the strength which I ought to have at my present time of life has
passed from me. I am getting weak, and peevish, and evil-disposed. A com-
paratively small trouble sits long and sore upon me. Bile, from being my
servant, is becoming my master ; and a bad one he makes, as all good ser-
vants ever do. I see nothing before me but a premature old age of pains and
groans, and gripes and grumblings, which will, of course, not last over long ;
and thus I shall be cut short in my career, when I should have been enjoying
life's tranquil evening, without a single vexation of any kind to trouble me.
Were I of a revengeful temper, it might be a consolation to think that my
master — the cause of all my woes — must suffer and sink with me ; but I don't
see how this can mend my own case ; and, from old acquaintance, I am rather
disposed to feel sorry for him, as one who has been more ignorant and im-
prudent than ill-meaning. In the same spirit let rne hope that this true and
unaffected account of my case may prove a warning to other persons how
they use their stomachs ; for, they may depend upon it, whatever injustice
they do to us, in their days of health and pride, will be repaid to themselves in
the long-run — our friend Madame Nature being a remarkably accurate ac-
countant, who makes no allowance for ignorance or mistakes."— CHAMBERS'
Memoir of a Stomach.

IN HUMAN PHYSIOLOGY. 179

23. Why do we relish butter on bread ?

Butter supplies the carbonaceous element in which
bread is lacking.

24. Is chewing tobacco more injurious than smoking?

(See Cutler's Physiology, pages 242-4.)

It is not only more filthy, but also more detrimental to
the health, as thereby a greater proportion of the poison-
ous alkaloids of the tobacco is carried into the system.
Among the too frequent evil effects of this powerful
narcotic are an impaired nutrition, a poisoned circulation,
a stupefied mind and conscience — evils which end not with
the parent but are transmitted many-fold to the child.

25. Why should ham and sausage be thoroughly cooked ?

The trichina, which frequents pork, is only destroyed
at a high temperature.

26. Why do we wish butter on fish, eggs with tapioca, oil
on salad, and milk with rice ?

To supply the elements of food lacking in the compo-
sition of fish, tapioca, etc.

27. Explain the relation of food to exercise.

Their relation is exceedingly intimate. If we eat much
we should take more exercise, and if, on the contrary, we
labor more, we desire additional food. Violent exercise,
directly after a hearty meal, is injurious ; but a gentle,
quiet half-hour's saunter will greatly benefit the digestion.

28. How do you explain the difference in the manner of
eating between carnivorous and herbivorous animals ?

Meat requires less saliva to aid in its digestion, and

l8o ANSWERS TO PRACTICAL QUESTIONS

henc i it is mainly digested in the stomach ; while vege-
table food needs to be thoroughly masticated and incor-
porated with the salivary mucus.

29. Why is a child 's face plump and an old marts
wrinkled ?

In the child the processes of nutrition are more active
than those of waste. The reverse is the case in old age.

30. Show how life depends on repair and waste.

(See Chemistry, page 34, et sey. ; and Physiology, page 120.)

31. What is the difference between the decay of the teeth
and the constant decay of the body ?

The particles of the teeth lost by decay are not
renewed, while in the body they are replaced as fast as
worn out.

32. Should biscuit and cake containing yellow spots of
soda be eaten ?

Certainly not. The alkali neutralizes the acids of the
alimentary juices, and thus impairs their functions, while
it corrodes and irritates the delicate mucous lining of
the digestive organs.

33. Tell how the body is composed of organs, organs are
made up of tissues, and tissues of cells.

(See Physiology, page 154, note.)

34. Why do we not need to drink three pints of water
per day ?

(See Physiology, page 133.)

The amount of water one needs depends upon the

IN HUMAN PHTSIOL OGT. I 8 1

character of his food, the nature of his labor, and the
activity of the three eliminating organs — the skin, the kid-
neys, and the lungs. One perspiring freely, or eating dry
food, needs more drink than one whose skin is inactive,
or whose food consists, in part, of soups or watery vege-
tables.

35. Why, during a pestilence, are those who use liquors
as a beverage the first, and often the only victims ?

The nervous system becomes impaired, the digestion
weakened, and the blood impoverished : hence, the func-
tions of the body being disturbed, its ability to resist
disease is greatly impaired. It is said that the alcohol
hardens the albuminous matter of the brain and the mem-
branous lining of the lungs, and hence clogs the action
of these organs.

36. What two secretions seem to have the same general
use?

The saliva and the pancreatic juice both change starch
into sugar. They have other important uses, however, in
the process of digestion. The former softens the food
and aids in the work of mastication, while the latter

emulsifies the fats.

37. How may the digestive organs be strengthened?

The digestive organs, like the other organs, are strength-
ened by judicious labor. The stomach is a muscle, and
like muscle, generally grows strong by use and weak by
disuse. The same laws should govern one in his daily
exercise of every organ — brain, hand, and stomach.

1 82 ANSWERS TO PRACTICAL QUESTIONS

175. — i. Why is the pain of incipient hip-disease fre-
quently felt in the knee ?

The sensation of pain is located by the mind, at the
part of the body where the injured nerve takes it rise.

2. Why does a child require more sleep than an aged
person ?

The processes of nutrition are going on rapidly, and,
in youth, much rest is required to repair the losses of
each day ; in age, waste predominates, and the repairs
made are of a temporary character. The building is soon
to be torn down, and little effort is taken to beautify or
strengthen that which is to be used for so short a time.

3. When you put your finger in the palm of a sleeping
child, why will he grasp it ?

The unconscious action of the near nervous centers
produces a contraction of the muscles.

4. How may we strengthen the brain ?

By judicious, habitual, but not exhaustive employment.
The life of the brain is in change. Monotony is stagna-
tion, and stagnation is decay.

5. What is the object of pain ?

Pain is monitory in its character. It guards against
danger and warns us of the presence of dfrease, z. e., the
want of ease. Were it not for this, we should lose the
use of the more delicate organs. A child might gaze at
the sun until its eyesight was ruined. The author knew
of a man who had lost the sense of feeling in one leg

IN HUMAN PHYSIOLOGY. 183

because of the sensory nerve being severed. He was
constantly bruising and burning that limb until he ruined
it entirely.

6. Why will a blow on the stomach sometimes stop the
heart?

By sympathy. The pneumogastric or tenth pair of
nerves supply the stomach and the heart.

7. How long will it take for the brain of a man six feet
high to receive news of an injury to his foot, and to reply ?

The nervous force has been estimated to travel at the
rate of 100 feet per second, although authorities vary
much. Taking this figure, it would require about one-
eighth of a second.*

8. How can we grow beautiful ?

If one is penurious, selfish, or hard-hearted, his face
will betray the fact to every passer by. Purity of thought
and nobleness of soul, the simple habit of cherishing high
and generous purposes, refine and spiritualize the coun-
tenance, making, at last, the homeliest features to glow
with a beauty that will be a true "joy forever."

9. Why do intestinal worms ever affect a child's sight ?
Through the action of the sympathetic system of nerves.

10. Is there any indication of character in physiognomy 1

(See Question 8 ; also Physiology, page 171.)

* A bare-footed boy steps on a thorn. If he had to wait for news of the
injury to be sent to his brain, and an order to be telegraphed back to remove
the foot, much time would be lost. As it is, with the first prick, the nearer
nerve-centers act and order the foot off almost before the brain has heard o*
the accident.

184. ANSWERS TO I'RACTICAL QUESTIONS

1 1. When one's finger is burned, where is the ache ?

All pain is in the brain. It is located, however, by the
mind, at the place of the injury.

12. Is a parlor generaHy a healthy room ?

No. It is generally ill-ventilated, and, to preserve the
furniture, kept dark, and hence damp.

13. Why can an idle scholar read his lesson and at the
same time count the marbles in his pocket ?

The duality of the brain may, perhaps, account for this.

(See Physiology, page 162, note.)

14. In amputating a limb, what part, when divided, will
cause the keenest pain ?

When a surgical operation is performed, the most pain-
ful part of it is the incision through the skin ; the muscles,
cartilage, and bone being comparatively without sensa-
tion. Hence, if we could benumb the surface, certain of
the lesser operations might be undergone without great
inconvenience. This is, in fact, very successfully accom-
plished by means of the cold produced by throwing a
spray of ether, or of some other rapidly evaporating liquid,
upon the part to be cut.

1 5. What is the effect of bad air on nervous people ?

The nerves connect all the organs of the body. They
are therefore especially sensitive to a derangement in the
function of any organ. Bad air causes impure blood, de-
ranged nutrition, and hence a disturbance of the entire
economy.

IN HUMAN PHYSIOLOGY. 185

1 6. Is there any truth in the proverb that "he who sleeps •,
dines V

The proverb expresses the fact that the nourishment of
the brain and other parts goes on actively during sleep,
they being controlled by the sympathetic nerves

17. What does a high, wide forehead indicate ?

It suggests a large brain and a high intellectual
power.

1 8. How does indigestion frequently cause a headache 1
Through the action of the sympathetic system.

19. What is the cause of the f oof s being " asleep ? "

(See Physiology, page 176, note.)

20. When an injury to the nose has been remedied by
transplanting skin from the forehead, why is a touch to the
former felt in the latter ?

The mind refers the sensation to the place where the
nerve naturally had its origin — /'. e., the part over which
its tiny fibres were originally distributed.

21. Are closely-curtained windows healthy ?
No. They keep out the sun and the fresh air.

22. Why, in falling from a height, do the limbs instinc-
tively take a position to defend the important organs ?

The reflex action of the spinal cord moves the limbs
into a position of defence, the brain having no time to
act.

1 86 ANSWERS TO PRACTICAL QUESTIONS

23. What causes the pylorus to open and close at the right
time ?

The reflex action of the nerves which preside over that
organ. In a similar way, a tickling in the throat excites
coughing.

24. Why is pleasant exercise most beneficial'}

A chief condition of keeping the brain healthy is to
keep the unconscious nervous functions in full vigor, and
in natural alternations of activity and repose. Thus it is
that (besides its effect in increasing the breathing and the
general vigor of the vital processes) muscular exercise
has so manifest a beneficial influence on a depressed or
irritable state of mind. The bodily movement, by afford-
ing an outlet to the activity of the spinal cord, withdraws
a source of irritation from the brain ; or it may relieve ex-
citement of that organ by carrying off its energy into a
safe channel. — HINTON.

25. Why does grief cause one to lose his appetite ?
Through the action of the sympathetic system.

26. Why should we never study directly after dinner ? .

The blood then sets toward the stomach, and the whole
strength of the system is needed to properly digest the
food.

27. What produces the peristaltic movement of the
stomach ?

The presence of the food which, through the sympa-
thetic system, acting involuntarily, sets in motion the
complicated apparatus of digestion.

IN HUMAN PHYSIOL OGT. 187

28. Why is a healthy child so restless and full of mis-
chief?

Nature prompts it to exercise all the muscles in its body
in order to their proper development.

29. Why is a slight blow on the back of a rabbit's neck
fatal?

. The medulla oblongata is not defended with thick
muscles as in man.

30. Why can one walk and carry on a conversation at
the same time ?

(See Question 13, page 176.)

3 1. What are the dangers of over-study ?

(See Hinton's Health and its Conditions, page IQS, et seq., and Cutler's
Analytical Anatomy, page 248.)

Exhaustive mental labor overstrains the delicate nerve-
cells of the brain, and the condition of the blood-vessels
of the entire body, especially of the vital organs, is regu-
lated, moment by moment, by its changing moods. Even
the supply furnished the brain is subject to the same
influence. Hence results deranged nutrition, impaired
circulation, and weakened brain and body. Whenever
we consume vital energy faster than it can be replaced,
we encroach upon the capital, and thus cause an irrepar-
able injury.

32. What is the influence of idleness upon the brain ?

If we would have healthy bodies we must have active
brains, that the streams of force may flow into every
organ from a full, fresh, energizing source. " The perfect

1 88 ANSWERS TO PRACTICAL QUESTIONS

health of a man is not that of an ox or a horse." The
proper exercise of the brain is an essential element of
real life.

33. State the close relation which exists between physical
and mental health and disease.

" A partial cultivation of the mental faculties is incom-
patible not only with the highest order of thought, but
with the highest degree of health and efficiency. The
result of professional experience fairly warrants the
statement that in persons of a high grade of intellec-
tual endowment and cultivation, other things being equal,
the force of moral shocks is more easily broken, tedious
and harassing exercise of particular powers more safely
borne, than in those of an opposite description, and dis-
ease, when it comes, is more readily controlled and cured.
The kind of management which consists in awakening a
new order of emotion, in exciting new trains of thought,
in turning attention to some new matter of study or
speculation, must be far less efficacious, because less
applicable, in one whose mind has always had a limited
range than in one of larger resources and capacities. In
endeavoring to restore the disordered mind of the clod-
hopper who has scarcely an idea beyond that of his
manual employment, the great difficulty is to find some
available point from which conservative influences may
be projected. He dislikes reading, he never learned
amusements, he feels no interest in the affairs of the
world ; and unless the circumstances allow of some kind
of bodily labor, his mind must remain in a state of soli-
tary isolation, brooding over its morbid fancies, and
utterly incompetent to initiate any recuperative move
ment" — Dr. RAY.

IN HUMAN PH T8IOL OGY. 189

34. In what consists the value of the power of habit ?

It saves the " wear and tear " of our principles. We
can perform an act a few times, though with difficulty,
and then ever after it becomes a habit. We resist evil
once, and thenceforth it is easier. We can become
accustomed to do good, so that the chances will all be
in favor of our well-being in any emergency. By as much
' as the power of habit is thus pregnant with good, by so
much is it susceptible of terrible evil.

35. How many pairs of nerves supply the eye ?

(See Physiology^ page 167.)

Three ; the motores oculi.

36. Describe the reflex actions in reading aloud.

The body is kept erect, the hand holds the book, the
eyes are directed to the page, the vocal organs pronounce
the words, the features express the sentiments, and the
other hand makes corresponding gestures — yet all the
time the mind is intent only upon the thought conveyed.

37. Under what circumstances does paralysis occur'}

When the nerve leading to any part of the body is
injured or fails to keep up communications between that
portion and the mind.

38. If the eyelids of a profound sleeper were raised, and a
candle bt ought near, would the iris contract1}

It would, by reflex action.

19° ANSWERS TO PRACTICAL QUESTIONS

39. How does one cough in his sleep ?

By the reflex action of the near nervous centers. A
tickling in the throat, or some other cause, acts as the
stimulus to excite their action.

40. Give illustrations of the unconscious action of the
brain.

(See Physiology, page 225.)

194. — i. Why does a laundress test the temperature of her
flat-iron by holding it near her cheek ?

The sense of warmth is very keen in the palms of the
hand, the cheek, etc. This sensation is much less deli-
cate in the lips and the back of the hand.

2. When we are cold, why do we spread the palms of our
hands before the fire ?

(See Question i.)

3. What is meant by a ''''furred tongue ? "

In health, the tongue has hardly a discernible lining,
but in disease, the epithelium, or scarf skin, accumulates,
and gives a white, coated appearance. This covering is
likely to be of a yellowish shade when the liver is dis-
turbed, and brown or dark in blood diseases. One's oc-
cupation often colors it Thus it is said the tongue of a
tea-taster has a curious orange-tint.

4. Why has sand or sulphur no taste ?
They are insoluble in the saliva.

5. What was the origin of the word palatable I

The mistaken notion that the palate, or roof of the
mouth, is the seat of the taste.

IN HUMAN PHYSIOLOGY. IQI

6. Why does a cold in the head injure the flavor of our
coffee?

Because the sense of taste is so dependent on that of
smell.

7. Name some so-called flavors which are really sensations
of touch.

Taste is not a simple sense. Certain other sensations,
as those of touch, temperature, smell, and pain, are
blended and confused with it ; and certain so-called tastes
are really sensations of another kind. Thus an astrin-
gent taste, like that of alum, is more properly an astrin-
gent feeling, and results from an impression made upon
the nerves of touch, that ramify in the tongue. In like
manner, the qualities known as smooth, oily, watery, and
mealy tastes, are dependent upon these same nerves of
touch. A burning or pungent taste is a sensation of pain,
having its seat in the tongue and throat. A cooling taste,
like that of mint, pertains to that modification of touch
called the sense of temperature. — HUTCHISON'S Phy-
siology, p. 190-1.

8. What is the object of the hairs in the nostrils ?

They prevent the entrance of dust and other impurities.
They are also exceedingly delicate in all sensations of
touch.

9. What use does the nose subserve in the process of respi-
ration ?

It warns us of noxious gases, sifts out impurities, and
tempers the air before it enters the delicate respiratory
organs.

I92 ANSWEHS TO PRACTICAL QUESTIONS

10. Why do we sometimes hold the nose when we take
unpleasant medicine ?

(See Question 6.)

11. Why is the nose placed over the mouth ?

As a sentinel at the gateway to the stomach and the
lungs.

12. Describe how the hand is adapted to be the instrument
of touch.

Its isolation at the extremity of the movable arm, the
mobility of its different parts, and the delicacy of the sen-
sation at the tips of the fingers, exquisitely adapt the
hand to be the instrument of touch.

13. Besides being the organ of taste, what use does the
tongue subserve ?

It aids in the mastication of the food and in speech.

14. Why is not the act of tasting complete until we
swallow ?

Because the organ of taste is located especially in the
back part of the tongue and the soft palate.

15. Why do all things have the same flavor when one's
tongue is "furred" by fever ?

They are really tasteless. The tongue is then dry, and
there is no saliva to dissolve and carry particles of the
food into the cells covering the nerves of taste.

1 6. Which sense is the more useful — hearing or sight?

(See Wonders of the Human Body, page 201.)

"The sight speaks more directly to the intelligence ; it

IN HUMAN PHYSIOLOGY. 193

enlarges the field of thought, it gives birth to precise no-
tions of light, of form, of extent ; and it permits the com-
munication of thought by conventional signs. Hearing is
a necessary condition of articulate language ; without it
man lives alone, affection and confidence lose their most
precious forms of expression, and friendship cannot exist.
Auditory sensations act upon the nervous system with
more force than visual sensations. We are carried away
by rhythm, or it adapts itself to our ideas and our passions ;
music plunges us into an ideal world, and holds us by an
indefinable charm ; in a word, if sight speaks more es-
pecially to the intellect, hearing addresses itself to the
affections. Sight is certainly more necessary to man than
hearing, but still the blind are generally gay and commu-
nicative, while the deaf seem inclined to melancholy. As
to the relative influence of these two senses on the devel-
opment of the intellect, we know that the education of the
deaf is slow, but may be complete, while that of the blind
is, on the contrary, rather rapid, but is almost always very
limited ; many ideas cannot be acquired by them, and, as
has been remarked by M. Longet, their minds rarely
attain maturity."

17. Which coat is the white of the eye ?
The sclerotic.

1 8. What makes the difference in the color of eyes ?

The varying shade of the pigment deposited in the iris
of the eye.

19. Why do we snuff the air when we wish to obtain a
distinct smell?

As muscular actions are called into play to aid the
sense of taste, as in smacking the tongue and lips, so the

J94 ANSWERS TO PRACTICAL QUESTIONS

act of " sniffing," which is a mixed respiratory and nasal
muscular effort, is used to bring odorous substances more
surely and extensively into contact with the upper and
proper olfactory region of the nose, besides causing a
larger amount of them to pass over the mucous surface in
a given time. — -MARSHALL.

20. Why do red-hot iron and frozen mercury (—40°)
produce the same sensation ?

The sensation in both cases is that of pain, not that of
touch.

21. Why can an elderly person drink tea which to a child
would be unbearably hot ?

The sensation of touch has become impaired, and is
much less delicate.

22. Why does an old man hold his paper so far from his
eyes?

" Far sight " is common among elderly people, and is
remedied by convex glasses. In old age the power of
adjusting the crystalline lens is lost.

23. Would you rather be punished on the tips of your
fingers than on the palm of your hand ?

The sense of touch is much keener in the tips of the
fingers than in the palm of the hand.

24. What is the object of the eyebrows ? Are the hairs
straight ?

They serve to prevent the perspiration of the forehead
from running down into the eye. They act, in a measure,
with the eyelashes, also to screen the eye from the dust

% IN HUMAN PHYSIOLOGY. 195

and glaring light. The hairs of the eyebrows overlap
each other and are set obliquely outward.

25. What is the use of winking?

It serves to wash the eyeballs, and thus keep the " win-
dows of the soul " clean. The necessity for winking is
shown by the great effort required to restrain it even for
a short time. First discomfort, then congestion of the
mucous membrane, and then a profuse watering of the
eye follow any attempt at stopping this necessary act. It
is an obscure sense of discomfort, not usually noticed by
the consciousness, that excites this movement, the objects
of which are periodically to cleanse the exposed part of
the eyeball, to moisten and lubricate it with the secretions
from the neighboring glands, and probably in this way to
aid in the preservation of the polish and translucency of
the epithelial layer on the transparent portion of the
globe. At the same time it carries towards the inner
corner all foreign bodies, and directs the residual secre-
tions towards the lachrymal ducts. Finally it allows a
brief but periodical rest to the levator muscle of the upper
eyelid. — MARSHALL.

26. When you wink, do the eyelids touch at once along
their whole length ? Why ?

In winking, both lids move, but the upper one much
the more extensively. Moreover, they do not come in
contact all along their margins at the same instant of
time, but meet first at the outer corner and then rapidly
inwards as far as the lachrymal papillae on which the lach-
rymal ducts are situated. By this sweeping movement, all
foreign bodies are carried to the lachrymal lake. — MAR-
SHALL.

196 ANSWEMS TO PRACTICAL QUESTIONS *

27. How many rows of hairs are there in the eyebrows ?

The eyelashes, or cilia, consist of two, and opposite the
middle of the eyelid, of three rows of finely-curved hairs
— those of the upper lid being more numerous, thicker,
and longer than those of the lower lid. " Those of the
upper lid are curved upward, those of the lower lid are
curved downward ; and when the lids are brought near
together, these two ranges of hairs stand like so many
crossed sabres, or a kind of chevaux-de-frise, guarding
the entrance to the eye." — DALTON'S Physiology, p. 330.

28. Do all nations have eyes of the same shape ?

No. Witness the almond-shaped eyes of the Chinese.
" The greater or less extent of the opening of the lids
makes the eye appear larger or smaller ; the conforma-
tion of the palpebral muscles and the tarsal cartilages
gives to the eye an elongated and languishing form as in
the East, or round and bold as among the Occidentals ;
but the dimensions and form of the globe are the same in
all countries and in all individuals." — Wonders of the
Human Body.

29. Why does snuff-taking cause a flow of tears ?
Because of the action of the sympathetic system.

30. Why does a fall cause one to " see stars ?"*

Whenever a nerve is excited in any way, it gives rise
to the sensation peculiar to the organ with which it com-

* u On the occasion of a remarkable trial in Germany, it was claimed by a
person who had been severely assaulted on a very dark night, that the flashes
of light caused by repeated blows upon the head enabled him to see with
sufficient distinctness to recognize his assailant. But the evidence of scien-
tific men entirely refuted this claim, by pronouncing that the eye, under the
circumstances named, was incapacitated for vision."— HUTCHISON.

IN HUMAN PHYSIOLOGY. 1 97

municates. Thus, an electric shock sent through the eye
gives rise to the appearance of a flash of light ; and pres-
sure on any part of the retina produces a luminous image,
which lasts as long as the pressure, and is called -a.phos~
phene. If the point of the finger be pressed upon the
outer side of the ball of the eye, a luminous image —
which, in my own case, is dark in the centre, with a bright
ring at the circumference (or, as Newton described it, like
•the "eye" in a peacock's tail) — is seen; and this image
lasts as long as the pressure is continued. — HUXLEY.

31. Why can we not see with the nose, or smell with the
eyes ?

Each set of nerves is adapted to transmit to the brain a
peculiar class of sensations alone.

32. What causes the roughness of a cat's tongue ?

The sharpness and strength of the papillae upon its
tongue. This is a peculiarity of the lion tribe.

33. Is the cuticle essential to touch ?

Yes. If the cuticle be removed, as in case of a blister,
contact with the exposed surface produces pain rather
than a sense of touch.

34. Can one tickle himself 1

It is said not ; but the author has found persons who
averred that they could produce this sensation upon them-
selves. The sense, it is noticeable, is present only in those
parts where that of touch is feeble.

35. Why does a bitter taste of ten produce vomiting?
The 5th pair of nerves, which supplies the lip and sides

19** ANSWERS TO PRACTICAL QUESTIONS

of the tongue, and perceives especially sweet and sour
substances, ramifies over the face, and hence an acid will
"pucker" the features ; while the gth pair, at the base of
the tongue, which is sensitive to salt and bitter tastes, is
distributed also to the throat, and is in sympathy with the
internal organs, since it seems to be " a common nerve of
feeling for the mucous membrane generally."

36. Is there any danger of looking "cross-eyed" for
fun?

The muscles used thus in sport may become perma-
nently distorted.

37. Should school-room desks face a window ?

No. The light should be admitted so as to fall over
the shoulder upon the book. Many school-rooms are
arranged to accommodate the teacher only, while a blind-
ing flood of light pours directly into the faces of the
pupils.

38. Why do we look at a person to whom we are listening
attentively ?

One sense instinctively aids another.

39. Do we really feel with our fingers ?
No. All sensation is in the mind.

40. Is the eye a perfect sphere ?

No. The front projects somewhat, while, at the back,
ihe optic nerve is attached like the stem to a fruit.

IN HUMAN PHYSIOLOGY. 199

41. How often do we wink ?
Five or six times a minute.

42. Why is the interior of a telescope or microscope often
painted black 1

To absorb the scattered rays of light which would
confuse the vision. For the same reason, the posterior
'surface of the iris, the ciliary processes and the choroid
are covered with a layer of dark pigment.

43 . What is " the apple of the eye ?"
The pupil.

44. What form of glasses do old people require ?

(See Question 22.)

45. Should we ever wash our ears with cold water?
Rarely, if ever, lest we chill this sensitive organ.

46. What is the object of the winding passages in the
nose?

To furnish additional surface on which to expand the
olfactory nerve.

47. Can a smoker tell in the dark, whether or not his
cigar is lighted?

Sight often seems to be essential to perfect what we
call a sensation of taste.

48. Will a nerve re-unite after it has been cut ?
Nerve-fibre seems to re-unite as readily as muscle-fibre.

200 ANSWERS TO PRACTICAL QUESTIONS.

49. Will the sight give us an idea of solidity ?

(See Physiology, page 196, note.)

50. Why can a skillful surgeon determine the condition of
the brain and other internal organs by examining the in-
terior of the eye ?

(See Physiology, page 196, note.)

51. Is there any truth in the idea that the image of the
murderer can be seen in the eye of the dead victim ?

When the flame of a taper is held near, and a little on
one side of, a person's eye, any one looking into the eye
from a proper point of view will see three images of the
flame, two upright and one inverted. One upright figure
is reflected from the front of the cornea, which acts as a
convex mirror. The second proceeds from the front of
the crystalline lens, which has the same effect ; while the
inverted image proceeds from the posterior face of the
lens, which, being convex backwards, is, of course, con-
cave forwards, and acts as a concave mirror. — HUXLEY.
The images formed upon the retina are as fleeting as light
itself, from the nature of the case, and disappear as soon
as the object is removed.

ANSWERS

TO THE

PEACTICAL QUESTIONS AND PEOBLEMS

IN THE

FOURTEEN WEEKS COURSE IN PHYSICS,

MOTION AND FORCE. *

37. — 1-37. (See pp. 15-19 of this Key for Answers to
these Questions.)

38. If a 100 horse-power engine can propel a steamer 5
miles per hour, will one 0/200 horse-power double its speed?

By no means. Resistance is proportional to zf*. (See
Physics, p. 26.) To double the velocity would require
over 400 horse-power. (See note, p. 27.)

39. Why is a bullet flattened if fired obliquely against
the surface of water ?

" Because the particles of the ball which strike the
water are impeded in their course by the particles of
water with which they come in contact, and are driven
back upon those lying next to them, before the motion of
the ball can be imparted to the water " — A. B. Watkins.

202 ANSWERS TO PRACTICAL QUESTIONS

40. Why are ships becalmed at sea of ten floated by strong
currents into dangerous localities without the knowkdge of
the crew ?

As there are no fixed objects with which to compare
their motion, the officers are not sensible of any move-
ment, and so are often drifted far out of their course.

41. A man in a wagon holds a $o-lb. weight in his hand.
Suddenly the wagon falls over a precipice. Will he, while
dropping, bear the strain of the weight ?

No. While on solid ground, his hand resisted the
tendency of the weight to fall toward the earth's centre
of gravity ; but all are now descending freely under the
influence of gravity, and he no longer feels the pressure.

42. Why are we not sensible of the rapid motion of the
earth ?

Because all the objects around us are moving in the
same direction with the earth, and there is nothing at
hand with which to compare.

43. A feather is dropped from a balloon which is im-
mersed in and swept along by a swift current of air. Will
the feather be blown away, or will it appear to a person in
the balloon to drop directly down ?

It will seem to drop directly downward, as if in a dead
calm. Its fall is vertical, however, only as regards the
balloon, and not as regards the earth.

(See Stewart's Physics, p. 18.)

44. Suppose a bomb-shell, flying through the air at the
rate of 500 feet per second, explodes into two parts of equal
weight, driving one-half forward in the same direction as

IN PHYSICS. 203

before, but with double its former velocity. What would
become of the other half?

One half will go forward with a double velocity
(=1000 feet per sec.), and the other half will be checked
and will fall directly to the ground.

(See Stewart's Physics, p. 37.)

45 . Which would have the greater penetrating power, a
small cannon-ball with a high velocity, or a large one with
a low velocity ?

The former would penetrate, while the latter would
crush an obstacle.

46. There is a story told of a man who erected a huge
pair of bellows in the stern of his pleasure-boat, that he
might always have a fair wind. On trial, the plan failed.
In which direction should he have turned the bellows ?

(See Key, p. 20.)

47. If a man and a boy were riding in a wagon, and,
on coming to the foot of a hill, the man should take up the
boy in his arms, would that help the horse ?

No change would be produced in the weight of the
entire establishment drawn by the horse, as no readjust-
ment of the load would modify the attraction of gravity
which produces the weight. Also, action =: reaction ; so
the man would press down on the wagon an amount
equal to the weight of the boy.

48. Why does a bird, as it begins to fly, always, if pos-
sible, turn toward the wind ?

For the same reason that a boy, wishing to raise a kite,
runs against the wind. The greater the velocity of the
wind, within certain limits, the greater the lifting force.

(See note, p. 32.)

204 ANSWERS TO PRACTICAL QUESTIONS

49. If we whirl a pail of water swiftly around with
our hands, why will the water tend to leave the centre of the
pain

This is generally attributed to the action of the cen-
trifugal force. More correctly, the inertia of the water,
i.e., its tendency to continue to move in the straight
line in which it is at each moment passing, overcomes
the weak force of cohesion, and the molecules fly off
from the centre of motion and collect against the outside
of the pail.

50. Why will the foam collect at the hollow in the
centre ?

The foam, being lighter than the water, has less mo-
mentum, and is forced back by the heavier particles.

51. If. two cannon-balls, one weighing 8 Ibs. and the
other 2 Ibs., be fired with the same velocity, which will go
the further1}

The former has much less surface in proportion to its
weight and consequent momentum. It will therefore go
much further against the resistance of the air.

52. Resolve the force of the wind which turns a common
wind-mill, and show how one part acts to push the wheel
against its support, and one to turn it around.

(See Arnott's Physics, p. 226.)

The toy-mill shown in Fig. 14, p. 32, illustrates the
principle perfectly. The vanes turn in a direction con-
trary to that in which they are inclined. Let GH, in Fig.
10, p. 31, represent the face of the vane, and the descrip-
tion in the text will then apply.

IN PHYSICS. 205

53. Why is a gun firing blank cartridges more quickly
heated than one firing balls ?

In the one case, the energy of the burning powder is
changed to heat ; in the other, largely to the motion of
the ball.

54. When an animal is jumping or falling, can any
exertion made in mid-air change the motion of its centre of
gravity ?

The centre of gravity falls steadily 16.08 feet (see
P- 54)> whatever other force may act on the body.

(See Second Law of Motion.)

55-60. (See Answers under Questions i to 7, on pages
5 and 6 of this Key.)

61. Why is a " running jump " longer than a " standing
jump "?

This is generally spoken of as an illustration of inertia.
It is really an example under the first law of motion.
The momentum of the person when running (m x v) is
added to the force with which he finally springs from the
ground for the jump.

62. Why, after the sails of a vessel are furled, does it
still continue to move ? and why, after the sails are spread,
does it require some time to get it under full headway ?

This illustrates the tendency of matter to continue in
its present state, whether of rest or of motion, i. e., its
inertia. For the former part of the question, apply the
first law of motion, and for the latter, the first paragraph
on p. 28 of the Physics. If, on starting with a heavy
load, the horses leap suddenly forward, they will break

206 ANSWERS TO PRACTICAL QUESTIONS

the harness; but, by a steady, constantly-increased
draught, they will overcome the inertia of the mass.

63. Why can a tallow candle be fired through a board?

Because it pierces the board so quickly that the par-
ticles have no time to yield. Its slight cohesion, multi-
plied by its velocity, is greater than the cohesion of the
board.

COHESION.

46. — i-io. (See Answers to these Questions under
Cohesion, pp. 6 and 7 of this Key.)

1 1 . Why can glass be welded ?

Because, like iron, it becomes viscous before melting.

ADHESION.

51. — 1-17. (See Answers to these Questions under
Adhesion, pp. 7 to 9 of this Key.)

1 8. Why does the water in Fig. 22 stand higher inside
of the tube than next the glass on the outside ?

There is the influence of a larger surface of glass in
proportion to the quantity of water to be lifted.

19. Why will clothes-lines tighten and sometimes break
during a shower ?

The rope absorbs water and expands transversely.
This shortens it with so much force as often to break it.
The shrinking of new cloth when wet illustrates the same
principle.

IN PHYSICS. 207

20. Show that the law of the diffusion of gases aids in
preserving the purity of the atmosphere.

(See New Chemistry, p. 96.)

Foul gases do not remain for any length of time in one
place, but tend to spread through the adjacent atmos-
phere. Fresh air also seeks to creep into noisome
localities.

21. In casting large cannon, the gun is cooled by a stream
of cold water. Why ?

The object of this is to cause the iron to cool more
quickly and so not give the molecules time to arrange
themselves in crystals.

(See p. 45.)

22. Why does paint adhere to wood? Chalk to the
blackboard ?

These are illustrations of the force of adhesion.

23. Why does a towel dry one's face after washing1}

The capillary pores of the cloth absorb the water on
the face.

24. Why will a greased needle float on water ?

The repulsion between the grease and the water is
sufficient to support the slight weight of the needle.

2 5 . Why is the point of a pen slit ?

The ink rises in the capillary space of the slit, and is
there held for use. When the pen is pressed on the
paper, the space is widened and the ink descends.

26. Why is a thin layer of glue stronger than a thick
one?

208 ANSWERS TO PRACTICAL QUESTIONS

The adhesion between the glue and the wood is
stronger than the cohesion between the particles of
glue ; hence the thinner the layer of glue the fewer the
particles acted upon only by the latter or weaker force.

GRAVITATION.

62. — 1-41. (See the Answers to these Queries on pp.
9 to 14 of this Key.)

42. How long would it take for a pendulum one mile in
length to make a vibration ?

(See Key, p. 13, Problem 37.)

According to the second law of pendulums (Physics,
P- 59),

i sec. : x : : A/39 : ^5280 x 12 in.
x — 40 -f sec.

43. How long would it take for a pendulum reaching
from the earth to the moon to make a vibration ?

i sec. : x : : A/39-i in. : \/24o,ooo x 5280 x 12 in.
x = 5 hrs. 28 -+- minutes.

44. Required the length of a pendulum that would
vibrate centuries.

(i sec.)2 : (100 x 365.25 x 24 x 60 x 60)^ : : 39.1 in. : x.
x = 6,145,674,053,727,272 + miles.

— SOLOMON SIAS.

45. What would be the time of vibration of a pendulum
64 metres long ?

(i sec.)2 : x* : : i metre (nearly) : 64 metres.
x = 8 seconds (nearly).

PHYSICS.

209

46. A ball is dropped from a height of 64 feet. At the
same moment a second ball is thrown upward with sufficient
velocity to reach the same point. Where will the two balls
pass each other ?

At the end of one second. The first ball would fall
64 feet in 2 seconds ; the second would rise for 2 sec-
onds, and they would pass in i sec.

47. Two bodies are successively dropped from the same
point with an interval of \ of a second. When will the
distance between them be one metre ?

Let / = time of descent of 2d body.
Then /-f .2 = time of descent of ist body.

Since the space passed over equals 4.9 m. (16 ft.) mul-
tiplied by the square of the time, we have

4.9 /2 = space passed over by 2d body.
4.9(/ + -2)2 = 4-9'2 + 1-96' + .196

= space passed over by ist body.

The difference between the 2 spaces being i m., we

have

4.9/2 + i.96/ + .196 — 4.9/2 = i m.

i.96/ = .804.

/ = .4102 sec. = time of descent of 2d body.
.6102 sec. = time of descent of ist body.

Therefore they will be i m. apart when the ist body has
fallen for .6102 sec., or the 2d body for .4102 sec.

PROOF. — 4.9 x .6io22 — 4.9 x .4io22 — i (nearly).

— WM. H. TAYLOR.

48. Explain the following fact : A straight stick loaded
with lead at one end, can be more easily balanced vertically

210 ANSWERS TO PRACTICAL QUESTIONS

on the finger when the loaded end is upward than when it
is downward.

When the loaded end is upward a slighter motion is
needed to bring the line of direction within the base.
The principle is similar to that of the balancing pole of
the gymnast.

49. What effect would the fall of a heavy body to the
earth have upon the motion of the earth in its orbit?

If its line of fall was exactly opposed to the direction
of the earth's motion, it would, by its momentum, tend
to retard the earth. If its line of fall was exactly in the
direction of the earth's motion, it would increase the
earth's velocity. If its line of fall was transverse to
the direction of the earth's motion, it would deflect the
earth from its orbit. All of these changes would, of
course, be infinitesimal in amount.

50. If a body weighing i Ib. on the earth were carried
to the sun, it would weigh 27 Ibs. How much would it
attract the sun ?

Ans. 27 Ibs.

5 1. Why does watery vapor float and rainfall?

(See Physics, p. 116, Question 13.)

The vapor of water is lighter than water itself, as the
particles are pushed so far apart by the repellent force —
heat.

52. If a body weighs 10 kilos, on the surface of the earth,
what will it weigh 1,000 km. above?

x: 10 kilos. :: (6,366 *)2: (7.366)2
x — 7.5 kilograms.

* The radius, or semi-diameter of the earth, is given by French astronomers
at 6,366 km.

IN PHYSICS. 211

53. A body is thrown vertically upward with a velocity
of 100 metres. How long before it will return to its

original position ?

Ans. 20.4 seconds.

54. How long will be required for a body to fall a
distance of 2,000 metres ?

Equation (6) d = \gt 2. 2,000 = -— 1\
.*. / = 20.2 seconds.

55. If two bodies weighing respectively i kilo, and i
demi-kilo. are connected by a rod 9 decimetres long, where is
the centre of gravity ?

Ans. 6 dm. from one body and 3 dm. from the other.

(See Key, p. 10, Question 7.)

ELEMENTS OF MACHINES.

79. — 1-26. (See Answers on pp. 20 to 24 of this
Key.)

27. Why is the rim of a fly-wheel made so heavy ?

The heavier the wheel, the greater its inertia ; and the
further the weight is from the centre of motion (or axle),
the greater its inertia or centrifugal force.

(See Physics, p. 78.)

28. Describe the hammer, when used in drawing a nail,
as a bent lever, i. e., one in which the bar is not straight.

If a lever is bent, or if, when it is straight, the bar is
not at right angles to the lines of action of the P and
the W, it is necessary to distinguish between the arms of

212 ANSWERS TO PRACTICAL QUESTIONS

a lever' and the arms of the P and the W, regarded as
forces which have moments around the F. In the latter
sense, the arms are the perpendiculars, dropped from the
F to the lines of action of the P and the W.

(See Everett's Text-book of Physics, p. 23 ; and Todhunter's Natural
Philosophy for Beginners, Vol. I, p. 78, where there is an excellent diagram.)

HYDROSTATICS.

96. — 1-38. (See pp. 24-29 of this Key.)

39. Suppose that Hiertfs crown was an alloy of silver
and gold, and weighed 22 ozs. in air and 20 \ ozs. in water.
What was the proportion of each metal?

" Multiply the specific gravity of each ingredient by
the difference between it and the specific gravity of the
compound. As the sum of the products is to the respec-
tive products, so is the specific gravity of the body to the
proportions of the ingredients. Then, as the specific
gravity of the compound is to the weight of the com-
pound, so is each of the proportions to the weight of its
material. ' ' — American Cyclopcedia.

Second method :

Let A — mass of crown = 22
" B = sp. gr. " = 14.66
" * = mass of gold
" #' = sp. gr. " = 19.26
" y = mass of silver

" / = sp. gr. " = 10.5
then

A = # +

IN PHYSICS, 213

and since

mass
volume —

specific gravity '
we have

A _ * , y_.

B ~ x + / '
whence we find (approximately),

Gold = 13.95
Silver = 8.05

40. Why will oily which floats on water, sink in alco-
hol ?

The specific gravity of absolute alcohol is only .79 ;
hence even the dilute alcohol of commerce is lighter
than water.

41. A specific-gravity bottle holds 100 gms. of water and
1 80 gms. of sulphuric acid. Required the density of the
acid.

Ans. 1.8.

42. What is the density of a body which weighs 58 gms.
in air and 46 gms. in water ?

Ans. 4f.

43. What is the density of a body which weighs 63 gms.
in air and 35 gms. in a liquid of a density of 3>$ ?

Ans. 1.9125.

HYDRAULICS OR HYDRODYNAMICS.
103.— 1-5. (See Key, pp. 29, 30.)

214 ANSWERS TO PRACTICAL QUESTIONS

PNEUMATICS.
116. — 1-18. (See Key, pp. 30-32.)

19. Explain the theory of " sucking cider" through a
straw.

The air in the straw being exhausted, the pressure of
the air on the cider in the vessel forces the liquid through
the straw.

20. Would it make any difference in the action of the
siphon if the arms were of unequal diameter ?

It would change the relative weight of the columns of
liquid in the two arms, and so increase or diminish the
difference of pressure which forces the liquid through
the long arm. Now, the heavier cd and the lighter ab^ in
Fig. 105, the faster the flow.

21. If the receiver of an air-pump is 5 times as large as
the barrel, how many strokes of the piston will be needed to
diminish the air nearly one-half!

One-fifth of the air in the receiver is removed at each
stroke. After the third stroke there would remain in the
receiver -ff^ of the original atmosphere.

22. What would be the effect of making a small hole in
the top of a diving-bell while in use ?

The air would escape at the top, and the water would
ascend and fill the bell.

ACOUSTICS.
144.— 1-16. (See Key, pp. 32-34.)

IN PHYSICS 215

17. Why will the report of a cannon fired in a valley be
heard on the top of a neighboring mountain, better than one
fired on the top of a mountain will be heard in the valley ?

A sound always has the intensity given it by the
density of the atmosphere where it originated, and not of
that where it is heard.

(See Tyndall's Lectures on Sound, p. 40.)

1 8. Why do our footsteps in unfurnished dwellings sound
so startlingly distinct t

In furnished rooms, the chairs, carpets, pictures, etc.
break up the echoes. Then, also, our footsteps are
louder on an uncarpeted floor.

19. Why do the echoes of an empty church disappear
when the audience assemble ?

The audience break up the echoes which interfere with
the original sound. Wires strung across a lofty room
often serve the same purpose.

20. What is the object of the sounding-board of a piano ?

By its vibrations and those of the body of air which
it encloses, it reinforces the sound of the wires.

21. During some experiments, Tyndall found that a
certain sound would pass through twelve folds of a dry silk
handkerchief, but would be stopped by a single fold of a wet
one. Explain.

(See Tyndall's Lectures on Light, p. 325, for a series of experiments
showing the action of moisture in propagating the sound-waves.)

22. What is the cause of the musical murmur often
heard near telegraph lines ?

2l6 ANSWERS TO PRACTICAL QUESTIONS

It is produced by the vibration of the wires. These
are thrown into motion by the wind and other causes.

23. Why will a variation in the quantity of water in the
goblet, when caused to sound as in the experiment described
on page 123, make a difference in the tone /

It changes the length of the vibrating portion of the
glass.

24. At what rate (in metres) will sound move through
air at 20° CJ

Sound moves at the rate of 1,090 feet at o° C. The
difference is nearly 2 feet for each degree C.

1090 feet + 40 feet =1130 feet.

OPTICS.

177.— 1-25. (See Key, pp. 35-39.)

26. What is the principle of the kaleidoscope?

27. Which will be seen at the greater distance, a yellow
or a gray body ?

The yellow, since it is brighter.

28. Look down into the glass of water shown in fig. 145,
and at a certain angle you will see two spoons, one small
and having the real handle of the spoon, though apparently
bent, and the real spoon with no handle. Explain.

In trying the experiments here alluded to, the glass
should be looked into at all possible angles, and the
spoon be turned about in the goblet. The glass of water
acts as a convex lens to magnify objects ; the concave

IN PHYSICS. 217

upper surface of the water, when one looks down into it,
as a concave lens to minify objects ; and the upper sur-
face of the water, when one looks up at it, as a total
reflector of the light. These facts, together with the
phenomenon of refraction, as shown in the apparent
breaking of the handle where it enters the water, will
account for all the curious modifications which may be
noticed. The experiment is worth hours of examina-
tion.

29. When a star is near the horizon, does it seem higher
or lower than its true place?

It seems higher, since the rays of light are bent
downward to the eye, and the object is seen in the line
of the ray as it enters that organ.

30. Why can we not see a rainbow at midday ?

Because the sun is not in the right position. To pro-
duce the ordinary rainbow it must be toward the eastern
or western horizon.

31. What conclusion do we draw from the fact that
moonlight shows the same dark lines as sunlight /

That its light has the same source as that of the sun,
and is, indeed, sunlight.

32. Why does the bottom of a ship seen tinder water
appear flatter than it really is ?

Because, by refraction, the bottom of the ship is
apparently elevated above its true place.

33. Of what shape does a round body appear in water?

It appears to be flattened ; and hence a round body
looks like an oval one.

2l8 ANSWERS TO PRACTICAL QUESTIONS

34. Why is rough glass translucent while smooth glass is
transparent ?

. The minute protuberances scatter the rays of light
and do not allow them to pass freely to the eye of the
observer.

35-42. (See Key, pp. 38, 39 ; Questions 28-35.)

43. Are there rays in the sunbeam which we cannot
perceive with the eye ?

(See Physics, pp. 163, 164.)

The calorific and actinic rays are invisible.

44. Why, when we press the finger on one eyeball, do we
see objects double ?

" Each retina possesses regions of symmetry with the
other, and on this fact singleness of vision depends;
each point of the outer portion of the retina of the right
eye has its point of symmetry in an inner portion of the
left, and when from a distant object rays fall on these
symmetrical points, that object will be seen single ; but
if, by the pressure of the finger or otherwise, we compel
the image in one of the eyes to fall upon another
and non-symmetrical point, the object at once becomes
double."

(See Draper's Human Physiology^ p. 395.)

45. Why does a distant light, in (lie night, seem like a
star?

The light radiating in every direction produces the
star-like effect, and we cannot see the surrounding objects
by which to correct the impression. Hence one often
mistakes a fire on a distant hill for a star rising.

IN PHYSICS. 2 1 9

46. Why does a bright light, in the night, seem so much
nearer than it is ?

We judge of the distance of an object by its magni-
tude, by its distinctness of outline, and by the size, etc.,
of intervening objects with which we compare it. In the
night, the brightness of a light confuses us by its vivid-
ness, seeming to be near at hand. Moreover, we cannot
see the neighboring objects, whose distance we know or
could estimate in the daylight. Our error is therefore
one of judgment. A firo at night thus seems near at
hand, and persons often run toward it for great distances,
expecting every moment to reach it.

(See Question 54.)

48, 49. (See Key, p. 40 ; Questions 47, 48.)

50. Why is the lens of a fish's eye (seen in the eye-socket
of a boiled fish) so convex ?

The difference of density between the water and the
eye is not so great as that between the air and the eye.
Hence, to refract the light sufficiently to bring it to a
focus on the retina requires a more convex lens.

(See Dudgeon, on the Human Eye ; and Physics, p. 268, note.)

51. When do the eyes of a portrait seem to follow a
spectator to all parts of a room ?

This is noticed only in a full-face portrait. In that
case the spectator, when he goes to either side, fails to
see the side of the eyeballs, and hence the effect is that
of looking directly into the eye. " A rifleman, portrayed
as if taking aim directly in front of the picture, appears
to every observer to be pointing at him specially."

5 2 . Why does the dome cf ike sky seem flattened ?

220 ANSWEHS TO PRACTICAL QUESTIONS

" Because the light from above, having to pass through
a less amount of air, is less obstructed than that which
comes horizontally. It is therefore more vivid."

53. Why do the two parallel tracks of a railroad appear
to approach in the distance ?

This depends upon what is known in painting as the
vanishing point. " Suppose two long rows of pillars, 100
feet apart, and an observer standing at one end looking
down the rows. Evidently, for the same reason as the
space between the top and bottom of the pillars, that is
to say their height, becomes apparently less and less as
their distance from the eye increases, so will the space
between each pillar and its opposite in the ether row
become apparently less, and the lines of pillars will, at a
certain distance (viz., where 200 feet are apparently
reduced to a poinO, seem to join. Beyond that spot,
known as the vanishing point, none of the pillars can be
seen."

(Read Arnott's Physics, pp. 616-622.)

54. Why does a fog magnify objects ?

The fog diminishes the intensity of the light. The
visual angle, however, remains the same. " An object at
two miles, subtending the same angle as an object at one
mile, is twice as broad, and the conclusion is drawn that
the dim object is large. Thus, a person in a fog may
believe that he is approaching a great tree fifty yards
distant, when the next instant throws him into a low
bush that has deceived him. A boy on the stage, with
a thin gauze screen before him, will look to the audience
like a man in the distance."

(See Arnott's Physics, p. 6a8.)

IN PHYSICS. 221

It is not the refraction of the rays of light, as is com-
monly supposed, which makes an object seem larger
when seen through a mist. It really appears to us in its
proper size. The mist, however, dims the color and the
outline, giving it the indistinctness belonging to a mile
in distance, while it has the magnitude of half a mile.
Dr. Wayland relates that, as he was sailing through
Newport harbor early one morning, in a dense fog, he
observed on the apparently distant wharf some very tall
men. While he was remarking upon their extraordinary
size, he was astonished to see them jumping about like
children, and otherwise behaving in a most unaccountable
manner. Presently, as the sun dispersed the fog, he
found that he was close to the wharf, and that the
gigantic men were really a party of small boys amusing
themselves with play.

The opposite mistake is made when the atmosphere is
more transparent than that to which we are accustomed.
Foreign travellers in Switzerland, who have started on
foot to visit a glacier or a mountain-peak which seemed
within easy distance, have often been surprised to find,
after two or three hours of brisk walking, that the object
of their desire seemed as far away as at first. So in
looking across a sheet of water, where there are no
intervening objects, distance is always underrated.

When we throw a stone at an object in the water we
find that our eye has deceived us, and the stone falls far
short of the mark. For the same reason, objects seen
on the shore from the water seem much less than their
natural size. The fact is, they appear of the magnitude
which belongs to the distance, but we suppose the distance
less than it is ; and, associating this magnitude with dimin-
ished distance, they appear to us less then they really are.

222 ANSWERS TO PRACTICAL QUESTIONS

In order to form these judgments correctly, one of
these elements must be fixed. From this we learn to
institute a comparison, and thus form an accurate
opinion. If we know the magnitude of an object, the
change in its color and outline will teach us its distance.
If we know its distance, we can judge of its magnitude.
Hence, painters, in order to give us a correct idea of an
object which they represent, always place in its vicinity
something with whose real magnitude we are familiar.
Thus, to show the size of a pyramid, an Arab with his
camel may be drawn at its foot. If the pyramid were
represented by itself, its intended size might be mistaken ;
but every one knows the size of a camel, and from this
he would judge of the magnitude of a pyramid. — Way-
land1 s Intellectual Philosophy, p. 78, et seq.

55. If you sit where you cannot see another person's
image, why cannot that person see yours ?

The angle of incidence is equal to the angle of reflec-
tion under all circumstances. If a ray from the other
person is not reflected at the right angle to reach your
eye, then a ray from you is not reflected at the right
angle to reach the other person's eye.

56. Why can we see the multiple images in a mirror
better if we look into it very obliquely ?

More light is then reflected to the eye.

(See Physics ) p. 151, 2d note.)

57. Why is an image seen in water inverted'}

(Examine Fig. 140, in Physics.)

58. Why is the surfs light fainter at sunset than at mid-
day?

(See Physics, p. 149, note.)

IN PHT81C8. 223

59. Why can we not see the fence-posts when we are
riding rapidly ?

There is not time for the rays of light to produce a
distinct impression on the retina.

(See Physics, p. 177, line 13.)

60. Ought a red flower to be placed in a bouquet by an
orange one ? A pink or blue with a violet one ?

(See Physics, p. 167.)

These are not complementary colors, and so weaken
rather than strengthen each other.

6 1. Why are the clouds white while the clear sky is blue1}

Prof. Tyndall has shown that the larger particles of
vapor scatter light of all colors, /. e., white light ; while
the smallest particles, only the blue rays. In accordance
with this fact the clouds are white and the sky is blue.
If the air were absolutely pure and free from all foreign
matter, it is thought that the azure of the sky would not
be seen and the heavens would appear black : the illu-
mination of objects would be strong and glaring on one
side, and on the opposite side the shadows would be
deep and unrelieved by the diffused , light to which we
are accustomed. The minute particles of vapor in the
air serve to scatter the direct rays of the sun and to
turn them around corners and into places not in the
direct line of the sunlight.

(See a full and interesting discussion in Tyndall's Lecture on Light, page
152, et seq.)

62. Why does skim-milk look blue and new milk white?

The fatty globules of the new milk reflect all the
colors of the spectrum to the eye ; but when deprived

224 ANSWEES TO PRACTICAL QUESTIONS

of the cream the milk reflects the blue light in excess
of the others.

63. What would be the effect of filling the basin, in the
experiment shown in Fig. 147, with salt water!

The water would be made denser and its refractive
power would be correspondingly increased.

(Compare Physics, p. 268, note.)

64. Why is not the image of the sun in water at mid-
day so bright as near sunset ?

(See Physics, p. 151, ad note.)

65. Why is the rainbow always opposite the sun ?

(See Physics, p. 166.)

HEAT.

203. — 1-54. (See Key, pp. 40-47.) With regard to
Question 23 there is much difference of opinion. Many
authorities think that temperature, and not moisture, is
the chief factor in producing barometric changes.

(See Muller, Komische Physik, 637.)

55. Why will "fanning" cool the face?

It brings in contact with the face a current of fresh
and generally cooler air.

(See Physics, p. 191.)

56. How are safes made fire-proof 1

By filling the space between the inner and the outer
iron-plates with a non-conducting material, as plaster,
etc., the safe is rendered nearly fire-proof. In one form

IN PHYSICS. 225

of safe> pipes of water are used, which absorb the heat
and render it latent.

57. Why can you heat water quicker in a tin than a
china cup ?

Because the metal is a better conductor of heat than
the china.

58. Why will" a woollen blanket keep ice from melting?
The woollen is a non-conductor of heat.

59. Does dew form under trees ?

The trees reflect back the heat radiated by the earth,
grass, etc., and so prevent the temperature, in general,
from sinking to the dew-point.

60. What is the principle of heating by steam ?

(See P&yszcs, p. 206.)

6 1. Why is a gun firing blank cartridges more heated
than one firing balls ?

(See Key, p. 207, Question 53.)

62. What is the cause of " cloud-capped" mountains ?

(See Physics, p. 197.)

63. Show how the glass in a hot-house acts as a trap to
catch the sunbeam.

(See Physics, p. 194.)

64. Does the heat of the sun come in through our win-
dows ?

(See Physics, p. 194.)

65. Does the heat of our stoves pass out in the same
way?

(See Pkysics, p. 194.)

226 ANSWERS TO PRACTICAL QUESTIONS

67. Is a dusty boot hotter to the foot than a polished one ?

(See Physics^ p. 194.)

68. The top of a mountain is nearer the sun ; why is it
not warmer ?

(See Question 62.)

72. Can we find frost on the windows and on the stone-
flagging the same morning ?

It requires a much intenser cold to produce the former
effect than the latter, as glass is a poorer conductor of
heat than stone. We frequently find frost on the flagging
early in the fall, but frost on the window is a sign of very
severe winter weather.

73. Why will not snow "pack" into 'balls except in mild
weather ?

The snow must be very near the melting-point for the
pressure of the hand to be sufficient to melt enough of
it to produce the phenomena of regelation. (Physics,
p. 202, ist note; also Tait's Recent Advances in Physical
Science, p. 129, and TyndalFs Forms of Water, p. 163.)
This principle involves the theory of Glaciers. "The
masses of snow cannot rest on the steep slopes of
Alpine summits. The pressure upon the under layers is
too great to allow them to remain upon their sloping
beds, and they are forced to descend. This descent is
accomplished in two forms-: that of an avalanche, one of
the most awful and imposing spectacles to witness ; or of
a glacier, which is really an avalanche of ice of extremely
slow motion. But the glacier differs from the ordinary
avalanche not only in that its motion is so slow, but in
that it consists of ice, thick, firm, and hard. The prin-
ciples involved in this transition of the loose, flaky

IN PHYSICS. 227

snow which first falls upon the mountain-top into the
solid ice of the glacier, are very well illustrated, as Helm-
holtz has remarked, in the manufacture of the school-
boy's snow-ball or snow-man. Very cold snow is always
light and flaky, and cannot be made by the pressure of
the hands into a cohesive mass ; in order to succeed in
that operation, snow is always employed which is already
at the melting-point, or only so far below this temperature
that the warmth of the hand suffices to bring it to the
required temperature, and then, by dint of pressure and
moulding, an icy ball may be easily produced. So with
the formation of the glacier ice. A process of almost
simultaneous melting and freezing goes on among the
under layers of snow, and under an immense and ever-
constant pressure from the weight of the snow above j
thus solid ice is formed. That this ice conforms itself to
the various windings, constrictions, and dilatations of its
rocky channel during its downward march is a fact not
less familiar than wonderful."

74. Why is the sheet of zinc under a stove so apt to
become puckered ?

When zinc cools after expansion it does not return
quite to its former dimensions, and so becomes " puck-
ered," as it is called.

75. Why does a mist gather in the receiver of the air-
pump as the air becomes rarefied ?

"The remaining air, cooled by rarefaction, absorbs
heat from the invisible vapor in combination with it, and
renders the water visible. The mist may be removed by
continued action of the machine, or by readmitting the
normal quantity of air."

(See Arnott's Physics, p. 448.)

228 ANSWERS TO PRACTICAL QUESTIONS

76. Why are the tops of high mountains in the tropics
covered with perpetual snow I

(See Question 62.)

MISCELLANEOUS QUESTIONS AND -PROB-
LEMS FOR REVIEW.

1. Does a plumb-line point to the earth's centre of figure
"*• Centre of gravity ?

2. In a dark room, let the light of a candle pass through
a small hole in a card, and the image of the candle on the
opposite wall will be inverted. Explain.

3. Why does drift on the Mississippi accumulate for the
most part on the west bank ?

4. How many times heavier is the earth than an equally
large globe of water ?

5. Why does the arc of a rainbow seem a part of an
ellipse instead of a circle ?

6. Why does a rocket ascend into the air ?

7. Is the water at the foot of Niagara Falls warmer
than that in the river above ?

8. What causes wheel fire-works to rotate ?

9. A brass-rod covered tightly with thin paper may be
held some time in a fiame without the paper being scorched ;
while, if the rod be of wood, the paper will scorch at once.
Why is this difference ?

10. How would it affect the action of a siphon if it were
carried up a mountain ?

IN PHYSICS. 229

11. If a vessel of water containing a floating body be
placed under the receiver of an air-pump, and the air
gradually exhausted, what will be the effect on the floating
body?

12. How will it change the height of the column of
mercury in a barometer to incline the tube ?

13. In the image of a written page seen in a mirror, why
does the writing seem to slope to the left ?

14. Why does a coin placed in a tumbler look i*r&jr
when the glass is full of water than when it is empty ?

15. Two bodies of different bulks weigh the same in
water; which will weigh the more in mercury, the larger or
the smaller ?

1 6. flow does the wind drift sand, snow, etc. ?

1 7. Why does oil " still troubled waters " ?

•

1 8. Why does crouching down at the highest points in a
swing, and standing up at the lowest point, increase the
velocity ?

19. What difference would it make in the guinea-and-
feather experiment to force into the tube additional air,
instead of exhausting it, as ordinarily done ?

EXPLAINING MIRRORS AND LENSES.

The author has met with the best success in explaining
mirrors and lenses to his pupils, by using the following
method.

A Concave Mirror. — Holding up before his eye the fore-
finger of each hand, he represents to the pupil how the rays
of light enter his eye converging ; how he then sees the ob-
ject on diverging rays : thus the ^visual angle being increased,
the apparent size of the object is correspondingly increased.
By crossing his two forefingers before his eye he represents
the focus, and shows how diverging rays then enter the eye ;
the object is seen on converging rays, the visual angle is de-
creased, and the apparent size of the object correspondingly
decreased.

A Convex Mirror. — Using the fingers in the same way, he
illustrates how diverging rays enter the eye, the object is seen
on converging rays, the visual angle is diminished, and the
apparent size of the object correspondingly diminished. The
rays of light are not brought to a focus, hence the second ef-
fect of a concave mirror cannot be seen.

The same illustration can be used in explaining lenses,
remembering that the effect of a convex lens is like that of a
concave mirror, and of a concave lens that of a convex mirror.

At the close of the explanation and illustration with the
fingers, the following formula is put on the blackboard, and
the pupil applies it to each class of mirrors and lenses :

CONVERGING (diverging) RAYS ENTER THE EYE, THE

OBJECT IS SEEN ON DIVERGING (converging) RAYS ; HENCE
THE VISUAL ANGLE IS INCREASED (decreased), AND THE
IMAGE IS LARGER (smaller) THAN LIFE.

THE NATIONAL SERIES OF TEXT-BOOKS.

THE NATIONAL READERS.

By PARKER & WATSON.

No. i. — National Primer, 6t.pp.,i6mo,

No. 2. — National First Reader, . . . f28pp.,?6mo,

No. 3. — National Second Reader, . . 224. pp.,

No. 4. — National Third Reader, . . 288pp.,

No. 5. — National Fourth Reader,*. . £32 pp., /2mo,

No. 6. — National Fifth Reader, . . . 600 pp., f2mo,

National Elementary Speller, . . . feo pp., f6mo,
National Pronouncing Speller, . . . 188pp., t2mo,

THE INDEPENDENT READERS.

By J. MADISON WATSON.

The Independent First (primary) Reader, so pp., f6mo,

The Independent Seconcf Reader, . 16O pp.,

The Independent Third Reader, . . 2&o pp.,

The Independent Fourth Reader, . . 26!,. PP., I2mo,

The Independent Fifth Reader, . . 336pp., f2mo,

The Independent Sixth Reader, •. . tflpp., t2mo,

The Independent Complete Speller, . 162 pp.,

The Independent Child's Speller (Script), so pp.,
The Independent Youth's Speller (Script), tea pp., f2mo,

National Series of Standard School-Sootes.

ENGLISH GRAMMAR.

CLARK'S DIAGRAM SYSTEM.

Ciark's Easy Lessons in Language,

Published 1874. Contains illustrated object-lessons of the moet attractive charac.
ter, and is couched in language freed as much as possible from the dry technicalities
of the science.

Clark's Brief English Grammar,

Published 1872. Part I. is adapted to youngest learners, and the whole forms a
complete •' brief course " in one volume, adequate to the wants of the common
school.

Clark's Normal Grammar,

Published 1870, and designed to take the place of Prof. Clark's veteran "Prac-
tical" Grammar, though the latter is still furnished upon order. The Normal is
an entirely new treatise. It is a full exposition of the system as described below,
with all the most recent improvements. Some of its peculiarities are— A happy
blending of SYNTHESES with ANALYSES ; thorough Criticisms of common errora
in the use of our Language ; and important improvements in the Syntax of Sen-
tences and of Phrases.

Clark's Key to the Diagrams,

Clark's Analysis of the English Language, •

Clark's Grammatical Chart,

The theory and practice of teaching grammar in American schools is meeting
with a thorough revolution from the use of this system. While the old method*
offer proficiency to the pupil only after much weary plodding and dull memorizing,
this affords from the inception the advantage of practical Object^ Teaching, address-
ing the eye by means of illustrative figures ; furnishes association to the m2mory,
Its most powerful aid, and diverts the pupil by taxing his ingenuity. Teachers
who are using Clark's Grammar uniformly testify that they and their pupils find it
the most interesting study of the bchoo! course.

Like all great arid radical improvements, the system naturally met at first with
much unreasonable opposition. It has not onty outlived the greater part of this
opposition, but finds many of its warmest admirers among those who could not
at first tolerate so radical an innovation. All it wants is an impartial trial to con-
vince the most skeptical of its merit. No one who has fairly and intelligently,
tested it in the school-room has ever been known to go back to the old method.}
A great success is already established, and it is easy to prophecy that the day is
not far distant when it will be the only system of teaching English Grammar. A»
the SYSTEM is copyrighted, no other text-books can appropriate this obvious nni
great improvement.

Welch's Analysis of the English Sentence,

assif
Leon

10

Remarkable for its new and simple classification, its method of treating conneo.
«vea, its explanations of the idioms and constructive laws of the language, etc.

The National Series of Standard ScAool-'Boofcs.

GEOGRAPHY.

NATIONAL GEOGRAPHICAL SYSTEM.

THE SERIES.

/. Monteith's First Lessons in Geography,
II. Monteith's New Manual of Geography,
II. McNally's System of Geography,

INTERMEDIATE OR ALTERNATE VOLUMES.

I*. Monteith's Introduction to Geography,

2*. Monteith's Physical and Political Geography,

ACCESSORIES.

Monteith's Wall Maps 2 sets (see page 15),
Monteith's Manual of Map- Drawing (Allen's System)
Monteith's Map-Drawing and Object-Lessons,
Monteith's Map-Drawing Scale,

1, PRACTICAL OBJECT TEACHING^ The infant scholar is first Introduce^
to a picture whence he may derive notions of the shape of the earth, the phenom
ena of day and night, the distribution of land and water, and the great natural
divisions, which mere words would fail entirely to convey to the untutored inind.
Other pictures follow on the same plan, and the child's mind is called upon to grasp
QO idea without the aid of a pictorial illustration. Carried on to the higher
books, this system culminates in Physical Geography, where such matters as
climates, ocean currents, the winds, peculiarities of the earth's cruet, clouds and
rain, are pictorially explained and rendered apparent to the most obtuse. The
illustrations used for this purpose belong to the highest grade of art.

2, CLEAR, BEAUTIFUL, AND CORRECT MAPS, In the lower numbers the
maps avoid unnecessary detail, while respectively progressive, and affording the
pupil new matter for acquisition each time he approaches in the constantly en-
larging circle the point of coincidence with previous lessons in the more ele«
mentary books. In tiie Physical and Political Geography the maps embrace many
new and striking features. One of the most effective of these is the new plan for
displaying on each map the relative sizes of countries not represented, thus obvi-
ating much confusion which has arisen from the necessity of presenting maps iq
tiie same atlas drawn on different scales. The maps of " McNally" have long been
celebrated for their superior beauty and completeness. This is the only school-
book in which the attempt to make a complete atlas also clear and distinct, ha»
been successful. The map coloring throughout the eeries is also noticeable.
Oelic&te and subdued tints take the place of the startling glare of Inharmonious
colors which too frequently in such treatises dazzle the eyes, distract the atten-
tion, and serve to overwhelm the names of towns and the natural feature* of tb»

The National Series of Standard

GEOGRAPHY-Continued,

MONTEITH'S INDEPENDENT COURSE.
Elementary Geography
Comprehensive Geography (with 103 Maps)

These volumes are not revisions of old works— not an addition to any

series— but are entirely new productions— each by itself complete, independent,
comprehensive, yet simple, brief, cheap, and popular ; or, taken together, the most
admirable " series " ever offered for a common-school course. They present the
following features, skillfully interwoven — the student learning all about one country
at a time.

LOCAL GEOGRAPHY, or the Use of Maps. Important features of
the Maps are the coloring of States as objects, and the ingenious system for laying
down a much larger number of names for reference than are found on any other
Maps of same size— and without crowding.

PHYSICAL GEOGRAPHY, or the Natural Features of the Earth,
Illustrated by the original and striking Relief Maps, being bird's-eye views or
photographic pictures of the Earth's surface.

DESCRIPTIVE GEOGRAPHY, including the Physical ; with some
account of Governments, and Races, Animals, etc.

HISTORICAL GEOGRAPHY, or a brief summary of the salient
ooints of history, explaining the present distribution of nations, origin of geo-
graphical names, etc.

MATHEMATICAL GEOGRAPHY, including ASTRONOMICAL.
which describes the Earth's position and character among planets ; also the Zones.
Parallels, etc.

COMPARATIVE GEOGRAPHY, or a system of analogy, con-
necting new lessons with the previous ones. Comparative sizes and latitudes arc
ehown on the margin of each Map, and all countries are measured in the "frain*

TOPICAL GEOGRAPHY, consisting of questions for review, an<J
testing the student's general and specific knowledge of the subject, with sugges-
tions for Geographical Compositions.

ANCIENT GEOGRAPHY. A section devoted to this subject, with
Maps, will be appreciated by teachers. It is seldom taught in our common schools,
because it has heretofore required the purchase of a separate book.

GRAPHIC GEOGRAPHY, or MAP-DBAWTNG by Allen's "Unit oi
Measurement" system (now almost universally recognized as without a rival) is
introduced throughout the lessons, and not as an appendix.

CONSTRUCTIVE GEOGRAPHY, or GLOBE-MAKING. With eacX
book a set of Map Segments is furnished, with which each student may make hia
own Globe by following the directions given.

RAILROAD GEOGRAPHY, with a grand Map illustrating route*

af travel in the United States. Also, a " Tour in Europe."

14

The National Series of Standard School-Sco&s.

MATHEMATICS.

DAVIES' NATIONAL COURSE.

ARITHMETIC.

!l. Davies' Primary Arithmetic,

2. Davies' Intellectual Arithmetic,

3. Davies' Elements of Written Arithmetic, .

4. Davies' Practical Arithmetic,

5. Davies' University Arithmetic.

TWO BOOK SERIES.
I. First Book in Arithmetic, Primary and Me^taL
2. Complete Arithmetic.

ALGEBRA.

1. Davies' New Elementary Algebra.

2. Davies' University Algebra,

3. Davies' New Bourdon's Algebra.

GEOMETRY.

1. Davies' Elementary Geometry and Trigonometry,

2. Davies' Legendre's Geometry,

3. Davies' Analytical Geometry and Calculus,

4. Davies' Descriptive Geometry,
4. Davies' New Calculus,

MENSURATION.

I. Davies' Practical Mathematics and Mensuration,

2. Davies' Elements of Surveying,

3. Davies' Shades, Shadows, and Perspective,

MATHEMATICAL SCIENCE

Davies' Grammar of Arithmetic,

Davies' Outlines of Mathematical Science,

Davies' Nature and Utility of Mathematics, '

Davies' Metric System, t

Oavies & Peck's Dictionary of Mathematics,

17

The National Series of Standard School-Books.

MATHEMATICS— Continued.

PECK'S HIGHER COURSE.

Peck's Manual of Algebra,

Bringing the methods of Bourdon within the range of the Academic Course.

Peck's Manual of Geometry,

By a method purely practical, and unembarrassed by the details which rather
confuse than simplify science.

Peck's Practical Calculus,
Peck's Analytical Geometry^
Peck's Elementary Mechanics,
Peck's Mechanics, with Calculus,

The briefest treatises on these subjects now published. Adopted by the great
Universities; Yale, Harvard, Columbia, Princeton, Cornell, &c.

ARITHMETICAL EXAMPLES.
Reuck's Examples in Denominate Numbers,
Reuck's Examples in Arithmetic,

These volumes differ from the ordinary arithmetic in their peculiarly practical
character. They are composed mainly of examples, and afford the most severe and
thorough discipline for the mind. While a book which should contain a complete
treatise of theory and practice would be too cumbersome for every-day us«», the
insufficiency of practical examples has been a source of complaint.

HIGHER MATHEMATICS.

Macnie's Algebraical Equations,

Serving as a complement to the more advanced treatises on Algebra, giving spe-
cial attention to the analysis and solution of equations with numerical coefficients.

Church's Elements of Calculus,
Church's Analytical Geometry,
Church's Descriptive Geometry, 2 vols..

These volumes constitute the "West Point Course" in their several department*.

Courtenay's Elements of Calculus,

A standard work of the very highest grade.

Hackley's Trigonometry,

With applications to navigation and surveying, nautical and practical geometry
and geodesy.

The National Series of Standard School-

HISTORY-Continued,

BARNES' ONE-TERM HISTORY
A Brief History of the United Stales,

This is probably the MOST ORIGINAL SCHOOL-BOOK published for many years
in any department. A few of its claims are the following:

1. Brevity.— The text is complete for Grammar School or intermediate
classes, in 290 12mo pages, large type. It may readily be completed, if desired, ia
one term of study.

2. Comprehensiveness,— Though so brief, this book contains the pith of all
the wearying contents of the larger manuals, and a great deal more than the mem-
ory usually retains from the latter.

3. Interest has been a prime consideration. Small books have heretofore
been bare, full of dry statistics, unattractive. This one is charmingly written,
replete with anecdote, and brilliant with illustration.

1 Proportion Of Events. -It is remarkable for the discrimination with
which the different portions of our history are presented according to their im-
portance. Thus the older works being already large books when the civil war
took place, give it less space than that accorded to the Revolution.

5. Arrangement. — In six epochs, entitled respectively, Discovery and Settle-
ment, the Colonies, the Revolution, Growth of States, the Civil War, and Current
Events.

6. Catch Words. — Each paragraph is preceded by its leading thought in
prominent type, steading in the student's mind for the whole paragraph.

7. Key Notes. — Analogous with this is the idea of grouping battles, etc.
about some central event, which relieves the eameness go common in such de-
scriptions, and renders each distinct by some striking peculiarity of its own.

8. Foot Notes.— These are crowded with interesting matter that is not
strictly a part of history proper. They may be learned or nbt, at pleasure. They
are certain in any event to be read.

9. Biographies of all the leading characters are given in full in foot-notes.

10. Maps.— Elegant and distinct Maps from engravings on copper-plate, and
beautifully "colored, precede each epoch, and contain all the places named.

11. Questions are at the back of the book, to compel a more independent use
of the text. Both text and questions are so worded that the pupil must give in.
telligrent answers IK HIS OWN WORDS. " Yes" and *'No" will not do.

12. Historical Recreations.— These are additional questions to test the stu-
dent's knowledge, in review, as : " What trees are celebrated in our history ?"
" When did a fog save our army ? " " What Presidents died in office ? " " When
was the Mississippi our western boundary ? " " Who said, ' I would rather be
right than President ? ' " etc.

13. Th3 Illustrations, about seventy in number, are the work of pur best
artists and engravers, produced at great expense. They are vivid and interest-
ing, and mostly upon subjects never before illustrated in a school-book.

11 Dates.— Only the leading dates are given in the text, and these are so
associated as to assist the memory, but at the head of each page is the date of the
event first mentioned, and at the close of each epoch a summary of events and dates.

15. The Philosophy Of History is studiously exhibited— the causes and
effects of events being distinctly traced and their interconnection shown.

16. Impartiality. — All sectional, partisan, or denominational views are
avoided. Facts are stated after a careful comparison of all authorities without
the least prejudice or favor.

17. Index.— A verbal indent at the close of the book perfects it as a work of
reference.

It will be observed that the above are all particular? <n which School Fl^tories
have been signally defective, or altogether wanting. Many other claims t« Ifcvoi
U shares in common with its predecessors.

24

The National Series of Standard School- 33ooks.

NATURAL SCIENCE.
"FOUKTEEN WEEKS" IN EACH BRANCH,

By J, DORMAN STEELE, A.M.

Steele's 14 Weeks Course in Chemistry (New Ed.)
Steele's 14 Weeks Course in Astronomy

Steele's 14 Weeks Course in Philosophy

Steele's 14 Weeks Course in Geology

Steele's 14 Weeks Course in Physiology

Steele's 14 Weeks Course in Zoology

Steele's 14 Weeks Course in Botany

Our Text-Booki in those studies are, as a general thing, dull and uninteresting.
They contain from 400 to 600 pages of diy facts and unconnected details. Tl^y
abound in that which the student cannot learn, much less remember. The paj'ii
commences the study, is confused by the fine print and coarse print, and neither
knowing exactly what to learn nor what to hasten over, is crowded through the
single term generally assigned to each branch, and frequently comes to the clooe
without a definite and exact idea of a single scientific principle.

Steele's Fourteen Weeks Courses contain only that which every well-informed
person should know, while all that which concerns only the professional scientist
is omitted. The language is clear, simple, and interesting, and the illustrations
bring the subject within the range of home life and daily experience. They give
such of the generaf principles and the prominent facts as a pupil can make famil-
iar as household words within a single term. The type is large and open ; there
is no fine print to annoy ; the cuts are copies of genuine experiments or natural
phenomena, and are of fine execution.

In fine, by a system of condensation peculiarly his own, the author reduces each
branch to the limits of a single term of study, while sacrificing nothing that is es-
sential, and nothing that is usually retained from the study of the larger manuals
in common use. Thus the student has rare opportunity to economize his time, or
rather to employ that which he has to the best advantage.

A notable feature is the author's charming " style," fortified by an enthusiasm
over his aabject in which the student will not fail to partake. Believing that
Natural Science is full of fascination, he has moulded it into a form that attracts
the attention and kindles the enthusiasm of the pupil.

The recent editions contain the author's " Practical Questions " on a plan never
before attempted in scientific text-books. These are questions as to the nature
and cause of common phenomena, and are not directly answered in the text, the
design being to test and promote an intelligent use of the student's knowledge of
the foregoing principles.

Steele's General Key to his Works, . . . . . $1.00

This work is mainly composed of Answers to the Practical Questions, and Solu-
tions of the Problems, in the author's celebrated "Fourteen Weeks Courses " in
the several sciences, with many hints to teachers, minor Tables, &c. Should be
on every teacher's desk.

34

The Natio?tal Series of Standard School-Books *

ELOCUTION.

Thwing's Vocal Culture.

A Drill- Book for voice and gesture, by Eev. Prof. Thwing, of Brooklyn Tabernacle
Lay College. Price 50 cts.

Taverner Graham's Reasonable Elocution,

Based upon the belief that true Elocution is the right interpretation of THOUGHT,
and guiding the student to an intelligent appreciation, Instead of a merely uechaii-
ical knowledge, of its rules.

Zachos1 Analytic Elocution.

All departments of elocution— such as the analysis of the voice and the sentence,
phonology, rhythm, expression, gesture, etc. — are here arranged for instruction iu
classes, illustrated by copious examples.

Sherwood's Self Culture.

Self-culture in reading, speaking, and conversation— a very valuable treatise to
those who would perfect themselves in these accomplishments.

SPEAKERS.

Northend's Little Orator, . &0.40 Child's Speaker, . $0.40

Two little works of the same grade but different selections, containing simple and
attractive pieces for children uuuer twelve years of age.

Northend's Young Declaimer, $0.50 National Orator, . 70

Two volumes of Prose, Poetry, and Dialogue, adapted to intermediate and gram-
mar classes respectively.

Northend's Entertaining Dialogues, ...'.... 70
Extracts eminently adapted to cultivate the dramatic faculties, as well as entertain.

Oakey's Dialogues and Conversations, 60

For School Exercises and Exhibitions, combining useful instruction.

James's Southern Selections for Reading and Oratory, 1.10

Embracing exclusively Southern literature.

Swett's Common School Speaker, 90

Raymond's Patriotic Speaker, 1.25

A superb compilation of modern eloquence and poetry, with original dramatic ex-
ercises. Nearly every eminent modern orator is represented.

COMPOSITION AND RHETORIC.
Brookfield's First Book in Composition, . . . . . $0.35

Making the cultivation of this important art feasible for the smallest child. By a
new method, to induce and stimulate thought.

Boyd's Composition and Rhetoric, 1.00

This work furnishes all the aid that is needfal or can be desired in the various de-
partments and styles of composition, both in prose and verse.

Day's Art of Rhetoric, 00

Noted for exactness of definition, clear limitation, and philosophical development
of subject ; the large share of attention given to Invention, as a branch of Rhetoric,
mid the unequalled 'analysis of style.

38

National Series of Standard

PUNCTUATION.
Cocker's Hand-Book of Punctuation ...... $0.50

With Instructions for Capitalization, Letter-Writing and Procf-Reading. Most
works on this subject are so abstruse and technical that the unprofessional reader
finds them difficult of comprehension ; but this little treatise is so simple and com-
prehensive that persons of very ordinary intelligence caii readily understand and
apply its principles.

MIND AND MORALS.
Mahan's Intellectual Philosophy ....... 1.25

The subject exhaustively considered. The author has evinced learning, candor,
and independent thinking.

Mahan's Science of Logic ......... 1.40

A profound analysis of the laws of thought. The system possesses the merit of
being intelligible and self-consistent. In addition to the author's carefully elabo-
rated views, it embraces results attained by the ablest minds of Great Britain, Ger-
many and France, in this department.

Boyd's Elements of Logic ......... 0.90

A systematic and philosophic condensation of the subject, fortified with additions
from Watts, Abercrombic, Whately, &c.

Watts on the Mind ........... 0.35

The Improvement of the Mind, by Isaac Watts, is designed as a guide for the at-
tainment of useful knowledge. As a text-book it is unparalleled ; and the disci-
pline it affords cannot be too highly esteemed by the educator.
— »t •» ••» —

Peabody's Moral Philosophy .... ..... 0.90

A short course ; by the Professor of Christian Morals, Harvard University— for
the Freshman Class and, for High Schools.

Alden's Text-Book of Ethics ......... 0.40

For young pupils. To aid in systematizing the ethical teachings of the Bible, and
point out the coincidences between the instructions of the sacred volume and the
sound conclusions of reason.

Wil lard's Morals for the Young . . . ..... 0.50

Lessons in conversational style to indicate the elements of moral philosophy.
The study is made attractive by narratives and engravings.

GOVERNMENT.
Howe's Young Citizen's Catechism 0.50

Explaining the duties of District, Town, City, County, State, and United States
Officers, with rules for parliamentary and commercial business.

Young's Lessons in Civil Government 0.90

A comprehensive view of Government, and abstract of the laws showing the
rights, duties, and responsibilities of citizens.

Mansfield's Political Manual „ . 0.90

This is a complete view of the theory and practice of the General and State Gov-
ernments, designed as a text-book. The author is an esteemed and able professor of
constitutional law, widely known for his sagacious utterances in the public press.

Martin's Civil Government . . 0.90

Emanating from Massachusetts State "Normal School. Historical and statistical.
Each chapter summarized by a succinct statement of underlying principles on which
good government is based.

Gallaudet's International Law 0.90

Published 1879, and the only work bringing the subject within the compass of a
convenient text-book,

39

35767

896271

THE UNIVERSITY OF CALIFORNIA LIBRARY