compound-flowered, in which many florets are collected into one head, as the thistle, sowthistle, hawkweed, &c. The lily is one of the principal ornaments of gardens in this month; and, with its delicate white flowers, gives an agreeable sensation of coolness to the eye.

The animal creation seem oppressed with languor during this hot season, and either seek the recesses of woods, or resort to pools and streams, to cool their bodies and quench their thirst.

The insect tribe, however, are peculiarly active and vigorous in the hottest weather. These minute creatures are for the most part annual, being hatched in the spring, and dying at the approach of winter they have therefore no time to lose in indolence, but must make the most of their short existence; especially as their most perfect state continues only during a part of their lives. All insects undergo three changes, in each of which they are transformed to a totally different appearance. From the egg, they first turn into caterpillars or maggots, when they crawl upon many feet, and are extremely voracious; many kinds of them doing much mischief in the gardens, and sometimes devouring the leaves of the trees, and even the herbage on the ground. This is their state in the spring. They next become aurelias, or chrysalides, when they resemble an infant closely wrapt in swaddling clothes, being motionless, taking no nourishment, and, indeed, having no appearance of living creatures. From this state they burst forth into the perfect insect, shining in all its colors, furnished with wings, full of activity, capable of propagating its species, and feeding, for the most part, on thin liquid aliments, such as the honey of flowers and juices of animals. Most of them continue thus but a short time. The male impregnates the female; she lays her eggs; and they both die.

This is a favorite season for the entomologist. Large copper and other but terflies are very active during this period -the large tiger and lacky moths are also to be found.

The luxury of cooling shades is now peculiarly grateful; and, indeed, is scarcely desired in this climate longer than a few weeks at the height of summer.

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Bathing, too, is a delightful amusement at this season; and happy is the swimmer who is able to enjoy the full pleasure of this healthful exercise. The power of habit to improve the natural faculties is in nothing more apparent than in the art of swimming. Man, without practice, is utterly unable to support himself in the water. In these northern countries, the pleasant bathing being short, few in proportion can swim at all; and even to those who have acquired the art, it is a laborious and fatiguing exercise. Whereas, in the tropical countries, where from their very infancy both sexes are continually plunging into the water, they become a sort of amphibious creatures, swimming and diving with the utmost ease, and for hours together, without intermission.

The excessive heats of this period of the year cause such an evaporation from the surface of the earth and waters, that, after some continuance of dry weather, large heavy clouds are formed, which at length let fall their collected fluid in extremely copious showers, and these frequently beat down the full-grown grain, and sometimes deluge the country with sudden floods. Thunder and lightning generally accompany these summer storms. Lightning is a collection of electric fire drawn from the heated air and earth, and accumulated in the clouds, which, at length overcharged, suddenly let go their contents in the form of broad flashes or fiery darts. These are attracted again by the earth, and often intercepted by buildings, trees, and other elevated objects, which are shattered by the shock. Thunder is the noise occasioned by the explosion, and therefore always follows the lightning; the sound travelling slower to our ears than the light to our eyes. Just the same thing happens when a gun is fired, at a distance. When we hear the thunder, therefore, all danger from that flash of lightning is over; and thunder, though so awful and tremendous to the car, is of itself entirely harmless.

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The effects of the great heat on the human body are agrecably allayed by the various wholesome fruits which Providence offers at this season for the use of man. Those which are now ripe are of all the most cooling and refreshing; as currants, gooseberries, raspberries, strawberries, and cherries. These are no less salutary and useful, than the richest products of the warmer climates.

Fowls moult, or lose their feathers, during this month. The smaller birds do not moult so early; but all renew their plumage before winter, when they are in their finest and warmest clothing.

feelings of honor and public virtue among all classes, without exciting their fanaticism, may truly be termed national.

CLASSIFICATION OF ROCKS.

PRIMARY FORMATIONS.

MOUTH.

HE Nelson monument at Yarmouth is a fluted column, 130 feet in height, erected on the South Denes, between the barracks and the mouth of the

haven. The monument may be distinguished at sea by the distant mariner: there would scarcely be a more appropriate landmark. In the foundation-stone a plate was placed, on which was engraved an inscription in Latin. It is so rarely that these compositions are calculated to touch the heart and imagination, that their absence is scarcely to be regretted. Their brevity at least would be deserving of commendation. Unless, however, there exist popular sentiments shared in by all ranks, from the palace to the fisherman's cabin, it is in vain that even monuments are raised, for they can excite no adequate and appropriate interest. The truest fame is that which gives feeling of pride to the humblest man, who thus feels himself a partaker in it. It is this which strengthens the heart of a nation, nerves it in the hour of danger, and gives that confidence which leads to actions in which feelings of selfvanish, and men become heroic, whether it be on the field of battle or in civil contests. A monument which cherishes high

ties. In the other, they are viewed as produced at successive periods, and classed according to their age. The latter is evidently best adapted to geology, considered as a history of the earth and of those revolutions it has undergone, and is now generally adopted in all cases where the relative age of the various formations can be determined. This, however, is not always the case, when the former must be chosen, and the rocks named simply as mineral compounds.

Some rocks are stratified, or divided into beds of great length and breadth compared to their thickness; others formed irregular masses of no determinate shape. This is the foundation of the first great division of rocks into stratified and unstratified; the former supposed to have been deposited from water, the latter to have been produced by igneous agency. Some rocks, it also appeared, were crystalline in their structure, others uncrystalline, and composed of fragments. Dividing the rocks on this principle, the classification is found nearly to correspond with the former; the igneous or massive rocks having in general a crystalline structure, the stratified being, on the other hand, mostly fragmentary. There is, however, a class of rocks participating in both characters, being stratified in form but crystalline in structure. These are supposed to have been originally strata consisting of fragments like the others, but

to have been exposed to intense heat, which has altered their structure and arranged the materials of which they were composed in new forms. On this account they are named metamorphic rocks, as having been metamorphosed or changed

in their forms.

Of these three classes, only the stratified rocks occur in a certain known chronological order. Having been deposited from water, at the bottom of lakes or the sea, the oldest or first-formed beds are necessarily the lowest, and are covered successively by newer and newer strata. Hence, where these rest on each other in an undisturbed position, there is no difficulty in discovering the order of time in which they were formed, and what is obscure in one place is often cleared up in another. But in the igneous rocks no such order is discoverable. They have been produced in every period, and exhibit few, if any, certain marks by which their relative age can be determined. This is also true of the metamorphic formations, which have been produced at various times, and from strata of very different ages. From their mode of formation, however, they are usually found in the lowest position, and covered by all the other strata which may be present, and hence have been named primitive or primary rocks by the Wernerians, and supposed to constitute part of the original structure of the globe.

These three classes of rocks are generally distinguished in all systems of geology. The varieties of the igneous and metamorphic rocks, to which particular names have been assigned, are also very nearly the same. More diversity prevails in the division and classification of the stratified rocks, almost every author altering the system of his predecessors to suit his own views. The arrangement of Werner, the celebrated German mineralogist, is still the best known, and, with a few modifications from recent discoveries, the most suitable for our purpose, and we shall consequently adopt it here. According to this, there are five divisions of stratified rocks. The first, or primary, corresponds to those classed above as metamorphic. The second division, or the transition rocks, includes the oldest

unaltered beds, and was so named as forming a passage from the crystalline to the fragmentary formations. In these, animal remains begin to appear, though in less profusion than in the third or secondary beds, which are also more truly fragmentary in structure. These are followed by the tertiary formations, with still more abundant remains of animals and vegetables, belonging also to species more closely allied to those now existing on the earth. The fifth and last class are the recent or alluvial formations, produced by causes now in actual operation on the globe. To these we shall successively advert, noticing, at the same time, the igneous rocks connected with them in nature. Though it might seem more scientific to have described the latter by themselves, yet this arrangement appears better adapted for popular illustration, and even for giving correct notions of the structure of the earth.

It

In examining a district of primary rocks, like the Highlands of Scotland, or the similar parts of other countries, an arrangement of this kind is often seen. In the highest and central part of the district are granite mountains, enclosed by zones of gneiss, quartz rock, mica-slate, clay-slate, limestone, and other primary strata. was at one time believed that these followed each other in the order now stated, but further investigation has shown that, though very common, this arrangement is by no means invariable. The order is not only reserved, but the rocks alternate or are mixed with each other in various ways.

The mineral characters of rocks, unless where they can be illustrated by specimens, are not very interesting, and we shall therefore avoid entering into details. Granite, as formerly stated, is a compound of quartz, felspar, and mica, sometimes also containing hornblende. Its varieties are very numerous, two, three, or all the four minerals above, being mixed in almost every degree of relative abundance; but that of quartz, felspar, and mica, is by far the most common, and is that most usually understood by this name. with it in composition, in almost every respect, but is divided into beds or strata, and has often a slaty structure.

Gneiss agrees

Mica

slate consists of quartz and mica, arranged in distinct layers, and, consequently, divides into very thin beds, which are often curiously bent and contorted. Sometimes quartz is found alone, composing quartzite or quartz-rock. Clay-slate is well known as the common roofing slate with which houses are covered. Limestone is not very abundant, but is remarkable as furnishing the various statuary and ornamental marbles of commerce, the former being pure white, the latter various shades of gray, yellow, green, red, or black. With these rocks, other beds of less importance oc casionally occur, which it is unnecessary to mention.

The manner in which these rocks have been formed has given rise to much controversy, and the theory of them stated above is only partially received. Werner supposed that the whole materials of this globe were originally dissolved in the waters of a primeval ocean, which gradually deposited the various substances it contained. First of all, the granite rocks were thrown down in vast beds extending over the whole globe. Then the gneiss followed, succeeded in turn by mica-slate, clay-slate, and the other primary formations, investing the earth in successive shells, almost like the coats of an onion. His opponents soon pointed out the inconsistency of this theory with facts, and the impossibility of finding a mass of water capable of dissolving these rocks, and his aqueous chaos is now almost forgotten'. Some, however, seem inclined to put an igneous one in its place. They affirm that the solar system was originally a nebula, like one of those which astronomers still observe in the heavens. That it was then a mass of intensely-heated vapor, which, cooling down, condensed and threw off the various planets which surround the sun; that the earth was then a fluid mass of molten rocks, and thus acquired its present form; continuing, however, to cool, first the granite rocks, and next the gneiss, with its associated beds, formed on the surface, while the interior, still retaining its heat and fluidity, produces earthquakes and volcanoes, with changes in the elevation of the land, and dislocations in the strata, by contracting as it cools still more. This theory is supported by many ingeni

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ous analogies in astronomy, but only its geological bearing can be here considered.

Dr. James Hutton, a singular, eccentric, but profound philosopher, who lived in Edinburgh in the end of the last century, has the merit of proposing the true theory of these rocks. He considered that granite was an igneous production, similar to lava, but differing from this in consequence of having been formed in the interior of the earth, below other rocks, and not like the latter on the surface. He also thought that many of the peculiarities in the primary beds were owing to their being in contact with this rock, which had hardened them and given them their crystalline aspect. He had long looked for some confirmation of this opinion in nature, but geology then was little understood in Scotland, and no description of its rocks, or the places where they were found, existed. At last, when on a visit in Perthshire, he examined the phenomena of Glen Tilt, a wild romantic glen which runs down from the central mountains of the Grampians to the valley of the Garry at Blair-Athol. The hills on the southeast side of the Tilt consist of quartz rock, mixed near the bottom with limestone, while on the northeast are granite mountains. Here Hutton found what he had long looked for, veins of granite running into the strata above, and was so delighted with this confirmation of his speculations as to shout loud for joy, so that his companions thought him out of his senses. In Glen Tilt the changes on the stratified rocks near the granite are very interesting, and fully confirm the Huttonian view of their origin. There seems little doubt that the marble, of green, yellow, white, or gray colors, quarried near the foot of this glen, is only a limestone altered by the vicinity of the igneous rocks. Even the fine white statuary marble of Carrara is now known to be a recent limestone changed by heat. The quarries lie in a wild desolate valley, at some distance from the town, on the western declivity of the Apennines; and the marble has probably been produced by the igneous agency elevating these mountains. In many other places, similar rocks, once believed to be the oldest on the earth, are found to have been formed at a period which, geologically considered, is very