These examples show that our sensations are not always a true test of temperature; and thus, if we wish to measure heat and cold accurately, we must have some instrument made for the purpose. Such an instrument we have: it is called a thermometer, a word which means heat-measurer.

It was long ago noticed that bodies expand, or swell out, when they are heated; and that they contract, or shrink into less bulk, when they are cooled. This observation led to the construction of the thermometer; for to measure the expansion or contraction of a substance is the same as to measure the quantity of heat that has produced this effect. The thermometer consists of a small glass tube of very

4

60°

400

82

fine bore and ending in a hollow bulb. The bulb is entirely filled with a fluid metal, called mercury, or quicksilver, which rises or falls in the tube according as it is heated or cooled. The space in the tube above the mercury is empty: it does not even contain air; for in preparing the instrument, sufficient heat is applied to the bulb to make the fluid, by expansion, fill the whole tube, which is then closely sealed at the upper end by melting the glass: the mercury sinks as it cools, and leaves the space empty.

The tube is fastened to a metal or Thermometer. Wooden plate, marked so as to measure the expansion of the mercury. This is called the scale, and the divisions upon it are called degrees. The degrees are counted upwards from the bottom, and are expressed by placing a small circle over the number. There are three different scales in use: that commonly used in this country is called Fahrenheit's scale, from the name of the inventor.

When the tube of the thermometer is immersed in melting ice or freezing water, the upper surface of the mercury stands always at the same point, which is called the freezing point of water. On Fahrenheit's thermometer Again, when the bulb is held

this point is marked 32°. in the steam of boiling water, the mercury rises to a fixed point, which is called the boiling point of water, and is marked 212°. All bodies that are as hot as boiling water raise the mercury to 212°; and all bodies that are as cold as freezing water, make the mercury shrink to 32°. The space between these two points is divided into 180 equal parts, each being called a degree. Similar equal divisions are carried below the point marked 32°, till 0° is reached, and this last point is called zero.

The tube of the thermometer may contain some other fluid than mercury; but, as this metal is in every respect well fitted for the purpose, it is most generally used in the construction of the instrument.

The thermometer is one of the most useful inventions of science. It enables travellers to compare the climates of different countries, and to give us, who stay at home, a distinct idea of them. It is also necessary in the arts: it enables workmen to apply the exact amount of heat required in delicate operations, where a little excess might spoil the whole work.

Fahrenheit the inventor (in 1720) of the thermometer which bears his name, was born at Dantzic, in Prussia, and afterwards lived in Holland.

Ze'ro-cipher; nothing: the point in a thermometer or barometer at which its scale commences.

Science-the knowledge of causes and effects, and of the laws o nature.

Art-the application of this knowledge to practical purposes. Climate-the prevailing temperature and moisture of a country. We speak of a cold climate, a dry climate, a healthy climate, &c."

QUESTIONS.

How do all substances affect us when we touch them? What is meant by temperature? Is the temperature of the same substance invariable? Give an example of variable temperature. How do we commonly judge of heat and cold? Is this method accurate? Show that two persons may have different notions of the same temperature. How may temperature be accurately measured? What effect has heat on bodies? and cold? State the principle upon which the thermometer is con

structed. What does the thermometer consist of? What fluid is used? Explain why the space above the mercury contains no air. Who was Fahrenheit? What is the freezing point of water in his thermometer? the boiling point of water? How are these points ascertained? Why is mercury used? What is climate? How do we get a distinct idea of the climate of other countries? What is meant by science? by art? Of what use is the thermometer in the arts?

What adverbs in the lesson are formed from gradual, accurate, entire, close, common? Parse less in "less warm," and in "less bulk."

'DICTATION.

Water begins to freeze at 32° of Fahrenheit's thermometer. Is your coat made of frieze? That confession frees you from punishment. The wild boar seized the melon, and bore it to his lair. This glass tube has a very fine bore. He bored a hole quite through the board. Thyme has a pleasant smell. Have you time to finish your seam? Your niece seems to be careless.

XXVIII.-KING

Brook, bear, endure.
Con-fess'ed, acknowledged.
Con-temp'-tu-ous-ly, scornfully.
Co'ur-tiers, nobles of the court.
De-fi'ed, braved, set at naught.
For-bea'r, cease.

Fo'r-ged, formed (by hammering)
Kind'-ling, flashing with anger.
Man'-date, command.

Me'ed, reward, recompense.

Mood, frame of mind."

CANUTE.

Pro-ces'-sion, a train of persons
moving in order.
Re'-gal, royal, kingly.
Scor'ned, despised.

Se'a-ward, towards the sea.
Sen'se-less, foolish.
Ser-vile, slavish, fawning.
Sta'te, pomp, dignity.
Swa'y, control, empire.
Un-de-ter'red, not frightened.
Up-bra'id-ing, reproving.

[CANUTE the Great reigned in England from 1017 to 1036. He was king also of Denmark and Norway, and was one of the wisest and best monarchs of his time. His courtiers, wishing to please him, ascribed to him unlimited power, asserting that even the sea would obey him. To reprove their foolish flattery, he took them to the beach one stormy day, and addressing the advancing tide, commanded it to approach no nearer nor dare to wet the feet of its sovereign. Heedless of the mandate, the waves continued to advance. Then, turning to his courtiers, Canute upbraided them for their senseless lie, saying that omnipotence belongs only to Him whom both earth and sea are ever ready to obey.]

UPON his royal throne he sat,

In a monarch's thoughtful mood;
Attendants on his regal state

His servile courtiers stood,

And strove with flatteries false and vain To win his smile, his favour gain.

Not so thought he, their noble king,
As his course he seaward sped,—
And each base slave, like a guilty thing,
Hung down his conscious head:
He knew the ocean's Lord on high;
They knew he scorned their senseless lie.

His throne was placed by ocean's side,
He raised his sceptre there,
And bade, with tones of kingly pride,
The waves their strife forbear;
And, while he spoke his royal will,
All but the winds and waves were still.

Louder the stormy blast swept by
In scorn of his idle word;
The briny deep its waves tossed high,
By his mandate undeterred,
And threatened in its angry play
To sweep both king and court away.

The monarch, with upbraiding look,
Turned to the courtly ring;

But none the kindling eye could brook
Even of his earthly king:

For in that wrathful glance they see
A mightier Monarch wronged than he!

Canute! thy regal race is run;

Thy name had passed away,
But for the meed this tale hath won,
Which never shall decay:
Its meek, unperishing renown
Outlasts thy sceptre and thy crown.

The Persian, in his mighty pride,
Forged fetters for the main,
And, when its waves his power defied,

Inflicted stripes as vain;

But it was worthier far of thee

To know thyself, than rule the sea.-Barton.