THE CIRCULATION OF WATER.

THE simplest form of the 'circulation of matter is that which is presented by the watery vapour contained in the atmosphere. From this vapour the dews and rains are formed which refresh the scorched plant and fertilize the earth. The depth of dew which falls we cannot estimate. On summer evenings it appears in hazy mists, and collects on leaf and twig in sparkling pearls; but at early dawn it vanishes again unmeasured-partly sucked in by plant and soil, and partly dispelled by the youngest sunbeams. But the yearly rain-fall is easily noted. In Britain it averages about thirty inches in depth; and in Western Europe generally, it is seldom less than twenty inches. Among the Cumberland mountains, in some places a fall of two hundred inches a year is not uncommon; while among the hills near Calcutta, as much as five hundred and fifty inches sometimes falls within six months.

Now, as the whole of the watery vapour in the air, were it to fall at once in the form of rain, would not cover the entire surface of the Earth to a depth of more than five inches, how 'repeated must the rise and fall of this watery vapour be! To keep the air always duly moist, and yet to maintain the constant and necessary descent of dew and rain, the invisible rush of water upwards must be both great and constant. The ascent of

water in this invisible form is often immediate and 'obvious, depending solely upon physical causes; but it is often also indirect, and being the result of physiological1 or of chemical causes, is less generally perceptible. Thus :

1. Water circulates abundantly between earth and air through the agency of purely physical causes. We see this when a summer shower falling upon our paved streets is speedily licked up again by the balmy winds, and wafted towards the region of clouds, ready for a new fall. But this form of circulation takes place on the greatest scale from the surface of the sea in equatorial regions, heated through the influence of the sun's rays. Thence streams of vapour are continually mounting upwards with the currents of ascending air; and with these they travel north and south, till colder climates 'precipitate them in dew, rain, or snow. Returned to the arctic or the temperate seas by many running streams, these precipitated waters are carried back again to the equator by those great sea-rivers which mysteriously traverse all oceans; and, when there, are ready to

rise again to repeat the same revolution. How often, since time began, may the waters which cover the whole Earth have thus traversed air and sea, taking part in the endless movements of inanimate nature!

2. Again: physiological causes, though in a less degree than the physical, are still very largely 'influential in causing this watery circulation. Thus the dew and rain which fall sink in part into the soil, and are thence drunk in by the roots of growing plants. But these plants spread out their green leaves into the dry air, and from numberless pores are continually 'exhaling watery vapour in an invisible form. From the leafy surface of a single acre in crop, it is calculated that from three to five millions of pounds of water are yearly exhaled in the form of vapour, in Britain; while, on an average, not more than two and a half millions fall in rain. Whether the surplus thus given off be derived from dews or from springs, it is plain that this evaporation from the leaves of plants is one of the most important forms which the circulation of water assumes.

Animals take into their stomachs another portion of the same water, and, as a necessary function of life, are continually returning it into the air from their lungs and their insensibly reeking hides. About two pounds a day are thus discharged into the air by a full-grown man; and larger animals probably give off more, in proportion to their size. Multiply this quantity by the number of animals which occupy the land surface of the globe, and the sum will show that this also is a form of watery circulation which, though less in absolute amount than the others I have mentioned, is yet of much importance in the 'economy of nature.

3. But water circulates also, in consequence of unceasing chemical operations, in a way which, if less obvious to the uninstructed, is, if possible, more beautiful and more interesting than the mere physical methods above described. The main substance of plants-their woody fibre-consists in large 'proportion of water. The same is true of the starch and sugar which are consumed by an animal. When the plant dies and 'decomposes in the air, the water is again set free from its woody stem. When the animal digests the starch and sugar, the water which these contain is discharged from its lungs and skin. Thus the living plant works up water into its growing substance, which water the decaying plant and the breathing animal again set free; and thus a chemical circulation continually goes on, by which the same water is caused again and

again to 'revolve. Within a single hour it may be in the form of starch in my hand, be discharged as watery vapour from my lungs, and be again absorbed by the thirsty leaf to add to the substance of a new plant!

JAMES F. W. JOHNSTON.

evaporation, disper'sion in

va pour.

exhaling, breath'ing out.
function, du'ty.
inan'imate, life'less.
influen'tial, op'erative.
maintain, uphold'.
men'tioned, named.
mysteriously, strange'ly.

1 Physiological, that is, pertaining to the functions of organic bodies, both vegetable and animal. Thus evaporation and condensation in the air constitute a physi

obvious, ev'ident.
oc'cupy, inhab'it.
perceptible, apparent.
precip'itate, throw
down.

proportion, degree'.
repeat'ed, fre'quent.
revolve, cir'culate.
scorched, with'ered.
uncommon, unu'sual.

cal cause, inhalation and exhalation by
plants and animals form a physiological
cause, decomposition of matter forms a
chemical cause, of the circulation of water.

QUESTIONS.-What proves the frequency with which the rise and fall of watery vapour must take place? To what three causes is the ascent of water into the atmosphere due? Give an example of the circulation of water due to purely physical causes. Show how physiological causes operate. Give an example of the chemical operations which cause water to circulate.

GINEVRA.

IF thou shouldst ever come to Mod'ena,1
Stop at a palace near the Reggio Gate,
Dwelt in of old by one of the Orsini.2
Its noble gardens, 'terrace above terrace,
And numerous fountains, statues, 'cypresses,
Will long 'detain thee; but before thou go,
Enter the house-prythee, forget it not-
And look a while upon a picture there.

"Tis of a lady in her earliest youth;—
She sits inclining forward as to speak,

Her lips half open, and her finger up,

As though she said, "Beware!" her vest of gold
Broidered with flowers, and clasped from head to foot—
An emerald stone in every golden clasp;

And on her brow, fairer than alabaster,
A coronet of pearls. But then her face,
So lovely, yet so arch, so full of mirth,
The 'overflowings of an 'innocent heart-
It haunts me still, though many a year has fled,
Like some wild melody!—Alone it hangs

Over a mouldering 'heir-loom, its companion,
An oaken chest half eaten by the worm.

She was an only child; from infancy
The joy, the pride, of an 'indulgent sire.
Her mother dying of the gift she gave,
That precious gift, what else remained to him?
The young Gine'vra was his all in life;
Still as she grew, for ever in his sight.
She was all gentleness, all 'gaiety,

Her pranks the favourite 'theme of every tongue.
But now the day was come, the day, the hour;
And in the lustre of her youth, she gave
Her hand, with her heart in it, to Francesco.

Great was the joy; but at the 'bridal feast,
When all sat down, the bride was wanting there--
Nor was she to be found! Her father cried,
""Tis but to make a trial of our love!"

And filled his glass to all; but his hand shook,
And soon from guest to guest the panic spread.
"Twas but that instant she had left Francesco,
Laughing and looking back, and flying still,
Her ivory tooth imprinted on his finger.
But now, alas! she was not to be found;
Nor from that hour could anything be guessed,
But that she was not! Weary of his life,
Francesco flew to Venice, and forthwith
Flung it away in battle with the Turk.
Orsini lived; and long mightst thou have seen
An old man wandering as in 'quest of something,
Something he could not find-ĥe knew not what.
When he was gone, the house remained a while
Silent and 'tenantless, then went to strangers.

Full fifty years were past, and all forgot,
When on an idle day, a day of search
'Mid the old lumber in the gallery,

That mouldering chest was noticed; and 'twas said By one as young, as thoughtless, as Ginevra, "Why not remove it from its lurking-place?" 'Twas done as soon as said; but on the way It burst-it fell; and lo, a skeleton ! And here and there a pearl, an emerald-stone, A golden clasp, clasping a shred of gold. All else had perished-s -save a 'nuptial ring, And a small seal, her mother's legacy, Engraven with a name, the name of both

"GINEVRA.” There, then, had she found a grave!
Within that chest had she concealed herself,
'Fluttering with joy, the happiest of the happy;
When a spring-lock, that lay in ambush there,
Fastened her down-for ever!

1 Mod'ena, capital of the

in'nocent, guile less.
legacy, bequest'.
lus'tre, brilliancy.

ROGERS. (')

province of | western extremity of which is the "Reggio Gate," where the Way passes on to Reggio. 2 Orsi'ni, a celebrated Roman family during the Middle Ages. It yielded two popes, and a great number of cardinals.

Æmilia, in the north of Italy, the former Duchy of Modena. The Emilian Way (Rimini to Piacenza) passes through it, and forms its principal street; at the northQUESTIONS. To what family did Ginevra belong? Why was she very precious to her father? How was her marriage interrupted? What was her fate? When was it discovered? What became of Francesco? What is the starting point of the poem?

GOD THE AUTHOR OF NATURE.

THERE lives and works

A soul in all things, and that soul is God.
The beauties of the wilderness are his,
That make so gay the solitary place,

Where no eye sees them. And the fairer forms,
That cultivation glories in, are his.

He sets the bright procession on its way,
And marshals all the order of the year;

He marks the bounds which Winter may not pass,
And blunts his pointed fury; in its case,
Russet and rude, folds up the tender germ
Uninjured, with inimitable art;

And, ere one flowery season fades and dies,
Designs the blooming wonders of the next.
The Lord of all, himself through all diffused,
Sustains, and is the life of all that lives.

COWPER.