heated, its capacity for water is increased; if it be suddenly cooled, the vapour is condensed, having parted with the latent heat which was necessary to preserve its rarefied condition. If, moreover, as soon as any portion of air is saturated or loaded with watery vapour, it is displaced by fresh dry air, the evaporation will be more rapid than under ordinary circumstances. Thus, under the influence of wind, the moisture of the earth is carried off with extreme rapidity. The water which by this process rose upon the wings of the wind in March, as an invisible vapour dissolved in the air, becomes condensed again in April, to fertilize the earth from which it originally proceeded.

Let us verify this by experiment. When the kettle boils we observe that steam or watery vapour issues from the spout. At first the atmosphere doe not dissolve it; and while this is the case it is visible to the eye. Before, however, it has been driven many inches from the vessel the steam disappears, and "vanishes into thin air." After this has gone on for a time, if the vapour be generated fast enough, the air ceases to be able to absorb, and a mist or steam is perceived in the apartment. While the air is yet transparent that is to say, while it retains its power of absorbing watery vapour -the fluid which passed from the kettle may be regained and made visible. A certain portion of heat supplied by the fire to the kettle was required to convert the liquid into vapour; the sensible heat became latent. Since this heat is necessary to the permanence of the vapour, it is plain that if it could be withdrawn the steam would return to its original form, fluid. This may be accomplished as follows:-Place upon the table of the room where the steam has been generated one of the tall cylindrical glasses used by the confectioners, capable of holding rather more than a pint. Take care that the outside is perfectly dry, and that the vessel is cool. Throw into the glass a mixture composed of five ounces of muriate of ammonia (sal ammoniac), five ounces of dry nitrate of potash (saltpetre), and eight ounces of sulphate of soda (Glauber's salts); pour over the powder a pint of the coldest water that can be procured, and stir gently with a glass rod or bone paper-knife. A large amount of heat will be absorbed by the mixture, and the air contiguous to the sides of the vessel will be cooled to such a degree that a portion of the vapour contained in it will be condensed and precipitated upon the sides of the glass, like drops of dew. In the same manner, we may observe that the moisture of heated rooms is condensed upon the window-panes when the air without is cold; and after a thaw, when the air is warmer than the walls of our houses, a similar deposit of water takes place.

The temperature at which the condensation of watery vapour begins is called the dew-point, and many ingenious instruments have been devised to ascertain the quantity of steam contained in the atmosphere at any particular time, by noticing the point on the thermometer at which dew is formed. We say the air is dry when water is quickly dried up, or absorbed by it; on the other hand, we say the air is damp when wet substances dry only slowly. In the former case a greater degree of cold would be required to precipitate the water, or condense the vapour; while in the latter the slightest reduction of temperature would induce the re-formation of water. When the condensation of vapour in the air, under ordinary circumstances, occurs by contact with cold solid bodies, it is called dew; when, on the contrary, the whole body of air is cooled, mists, clouds, or rain are formed. The vapour of which clouds are composed, and which supplies the fluid to

the showers of April, is in a peculiar condition. A scientific traveller on the Alps describes the appearance of a mist by which he was enveloped, and which was almost stagnant. He was greatly astonished at the size of the drops, as he imagined them to be, the more especially when he saw them float along without any tendency to fall to the earth. These bodies, which were of the size of the largest peas, proved, upon investigation, to be vesicles, or small bubbles of water of extreme tenuity. It is considered probable that in clouds and mists the fluid is always in this singular condition, though there may be great differences in the size of the vesicles. If clouds, mists, or fogs consisted of drops, they would immediately fall to the earth; indeed, it has been calculated "that a drop of water, one thousandth part of an inch in diameter, in obedience to the action of gravitation, would acquire a descending velocity equal to nine or ten feet per second; whereas we see clouds hover at a small elevation for hours. It is probable that this vesicular condition of water is produced when two volumes of air of different temperatures, and in different electrical conditions, meet and mix together. If this, however, takes place too rapidly, drops, instead of vesicles, are formed; or when the stratum of air in which the vesicles float is suddenly condensed, the separate globules approach each other and merge, and a fall of rain is the consequence.

It must be admitted, nevertheless, that the exact circumstances which produce the vesicular state of water are not known, nor are scientific men prepared to state positively what conditions are necessary to its permanence, or its change into the form of rain-drops.

Some extraordinary falls of rain have been recorded: on the 25th of October, 1825, a fall of rain equal to the depth of thirty-two inches fell in twenty-four hours at Genoa; on the 9th of October, 1827, there fell at Joyeuse, in the south of France, thirty-one inches in twenty-two hours. A curious circumstance attending the fall of rain is that the quantity collected by rain-gauges, or instruments used for registering the depth of water which falls, varies in an unaccountable degree with the elevation of the instruments. The quantity collected by rain-gauges on the surface of the ground is considerably greater than when the instruments are placed at some elevation above. On an average of thirteen years the quantity of rain which fell annually in the court of the Observatory at Paris was twenty-two inches; while the mean quantity which fell on the terrace, ninety-two feet above the level of the court, was less than twenty inches. A rain-gauge placed at the top of York Minster showed a fall of nearly fifteen inches between February, 1833, and February, 1834; while another perfectly similar instrument on the ground registered nearly twenty-six inches. The cause of these singular discrepancies is not understood, but is supposed to depend upon the currents of wind, which interfere with the perfect actions of instruments elevated from the ground.

The average quantity of rain which falls in a year in any given place depends upon a great variety of circumstances, principally those connected with climate, &c., which have been explained in a previous month.

The sky is usually overcast by a dark cloud before a shower, but instances are on record where rain has fallen from a serene, cloudless sky. This curious phenomenon is said to occur frequently in the island of Mauritius in the evening, when the stars are shining; it has also been observed in Paris, Geneva, and Constantinople.

"The

In tropical regions the rains are periodical, as before mentioned; they fall only at certain seasons, and for an hour or two daily. The drops are said to be larger than those which we are accustomed to see, and owing to their greater weight, strike the earth with considerable violence. morning is clear, the clouds gather towards mid-day, heavy rains fall in the afternoon, and the evening is again clear and fine. At times the sky is unclouded for months together."

Rain is unknown in some parts of the world, viz., the arid deserts of Africa and Arabia, the deserts of Gobi, parts of Mexico and California, and the west of Peru.

From numerous observations it has been proved that the mean or average annual temperature generally occurs on the 24th of April and the 21st of October in the temperate zone.

In England the course of the heat is as follows:-The temperature rises from the middle of January until the middle of July, from which period it diminishes, finally reaching its minimum again in the middle of January.

CHAPTER V.

MAY.

"Fair-handed Spring unbosoms every grace,
Throws out the primrose and the snowdrop first;
The daisy, primrose, violet darkly blue,
And polyanthus of unnumber'd dyes;

The yellow wallflower stain'd with iron-brown,
And lavish stock, that scents the garden round;
From the soft wing of vernal breezes shed,
Anemones; auriculas enrich'd

With shining meal o'er all their velvet leaves,
And full ranunculus of glowing red.

Then comes the tulip race, where Beauty plays
Her idle freaks; from family diffused
To family, as flies the father-dust,

The varied colours run; and while they break
On the charm'd eye, the exulting florist marks,
With secret pride, the wonders of his hand.
No gradual bloom is wanting-from the bud,
First-born of Spring, to Summer's musky tribes;
Nor hyacinths of purest virgin_white,

Low bent, and blushing inwards; nor jonquils
Of potent fragrance; nor narcissus, fair,

As o'er the fabled fountain hanging still;

Nor broad carnations, nor gay spotted pinks;

Nor, shower'd from every bush, the damask rose.

Infinite numbers, delicacies, smells,

With hues on bues expression cannot paint

The breath of Nature, and her endless bloom."-THOMSON.

"In April come the double white violet, the wallflowers, the stock-gilliflowers, the Cowslip, and lilies of all natures; rosemary flowers, the tulip, the double peony, the pale daffodil, the French honeysuckle, the cherry-tree in blossom, the damascene, and plum-trees in blossom, the white thorn in leaf, and the lilac-tree."-BACON.

THE wisest and best of men have ever entertained a passionate love of flowers. The poet-king of the Hebrews was evidently an ardent lover of nature, and familiar with the phenomena passing around him. "Let no flower," he exclaims, "let no flower of the spring pass by us: let us crown ourselves with rosebuds before they are withered!' And his writings teem with illustrations derived from the beauties of nature around him. modern times we find philosophers and poets with the same love of the exquisite productions of the early year-the flowers of May. With what joy old Spenser seems to write:

"Then came fair May-the fairest maid on ground-
Deckt with all dainties of her season's pride,
And throwing flowers out of her lap around."

And Herrick, too:

"Oh, May, with all thy flowers and thy greene,
Right welcome be thou, fair fresh May!"

In

To quote from Shakespeare would be truly "love's labour lost;" for every page is redolent with "the breath of flowers," which, as Bacon observes,

comes and goes like the warbling of music." How the mighty Milton, "from his eminence aloft," sweetly discourses of the denizens of the meadow and the wood, and rejoices over—

"The flowery May, who from her green lap throws

The yellow cowslip and the pale primrose!"

And lesser poets, down to Wordsworth, Tennyson, and Longfellow, revel in their love of flowers.

Our Lord and Master sought in the flowers and fields the poetical illustrations of the arguments which he wished to enforce, and in so doing appealed to a strong perception and love of the beautiful, which is common in every land where Nature is prodigal of floral beauty. "Consider the lilies of the field," said he, "how they grow; they toil not, neither do they spin: and yet I say unto you, that Solomon in all his glory was not arrayed like one of these."

Since May is the festival of flowers, the gay-day of the vegetable kingdom; and since all, from the youngest to the oldest, never think of the time apart from its blossoms and sunshine, leaves and fragrance, we shall, in this chapter, "consider the lilies of the field, how they grow.' A greater familiarity with the denizens of the meadow and the wood will not diminish the love we have hitherto felt for them, but will add to our list dear acquaintances whose faces will greet us as in our solitary walks, peeping from the hedge-side, or by the forest path, to remind us of the ever-watchful care which strewed the waste ground with flowers, and covered the desert island, and even the rock, with life and beauty.

The

It is manifest, as plants are not exactly alike, that it is convenient to name them differently; but it is also plain that as in some points certain plants resemble each other very closely, it is desirable to group such plants together, and give them names which imply their relationship. This nominal division of the vegetable kingdom into families and orders is necessary, if we seek to gain any general idea of its parts, because it would be quite impossible for any one person to have a detailed knowledge of each individual plant, separately considered, without its relations to others. A similar kind of division is found convenient in almost everything. country is divided into counties, hundreds, &c.; the legislative body into Lords and Commons; the school into classes and divisions. The surface of the world is artificially divided into sections, by lines of latitude and longitude; the stars are considered in groups. Knowledge is divided into arts and sciences; and science, again, is subdivided into geology, geography, &c. Division and arrangement are necessary to the consideration of every part of the vast field of nature, and as the vegetable kingdom consists of upwards of 100,000 species, it is especially convenient to those seeking to become better acquainted with inanimate life.

In calling attention, then, to flowers and their growth as the most remarkable phenomena of the months of May and June, we propose to consider the best method of becoming acquainted with their nature and properties; or, in other words, what system of classification it is best to adopt in the study of botany.* But to do this we must possess some information with

* The word is derived from ẞoravn, a plant; the root of the Greek word signifies "to feed."