difficulty of performing this problem will appear to be considerable, if not insurmountable; yet the little architects, by patiently examining their stones and turning them round on every side, never fail to accomplish their plans. This, however, is only part of the problem, which is complicated with another condition, and which we have not found recorded by former observers, namely, that the under surface shall be flat and smooth, without any projecting angles which might impede its progress when dragged along the bottom of the rivulet where it resides. The selection of the stones, indeed, may be accounted for, from this species living in streams where, but for the weight of its house, it would to a certainty be swept away. For this purpose, it is proba ble that the grub makes choice of larger stones than it might otherwise want; and therefore also it is that we frequently find a case composed of very small stones and sand, to which, when nearly finished, a large stone is

Sand Nest balanced with a Stone.

added by way of ballast. In other instances, when the materials are found to possess too great specific gravity, a bit of light wood, or a hollow straw, is added to buoy up the case.

Nest of Caddis-Worm balanced with Straws.

It is worthy of remark, that the cement, used in all these cases, is superior to pozzolana* in standing water, in which it is indissoluble. The grubs themselves are also admirably adapted for their mode of life, the portion of their bodies which is always enclosed in the case, being soft like a meal-worm, or garden caterpillar, while the head and shoulders, which are for the most part projected beyond the door-way in search of food, are firm, hard, and consequently less liable to injury than the protected portion, should it chance to be exposed.

We have repeatedly tried experiments with the in

A cement prepared of volcanic earth or lava.
3

VOL. II.

abitants of those aquatic tents, to ascertain their mode of building. We have deprived them of their little houses, and furnished them with materials for constructing new ones, watching their proceedings from their laying the first stone or shell of the structure. They work at the commencement in a very clumsy manner, attaching a great number of chips to whatever materi als may be within their reach with loose threads of silk, and many of these they never use at all in their perfect building. They act, indeed, much like an unskilful workman trying his hand before committing himself upon an intended work of difficult execution. Their

main intention is, however, to have abundance of materials within reach: for after their dwelling is fairly begun, they shut themselves up in it, and do not again protrude more than half of their body to procure materials; and even when they have dragged a stone, a shell, or a chip of reed within building reach, they have often to reject it as unfit.

VEGETABLE SUBSTANCES-THE CORK TREE.

The Cork Oak is not so large a tree as the common oak. There are several varieties: a broad leaved and a narrow leaved, which are evergreens; beside other varieties which shed their leaves. The broad-leaved evergreen is, however, the most common, and it is the one from which the cork of commerce is chiefly obtained.* It is mentioned by Theophrastus, Pliny, and some other ancient naturalists as being well known in the days of the Greeks and Romans,-the latter of whom used it for a variety of purposes, and among the rest for the stopping of bottles. They used it for floats to their nets and fishing tackle; for buoys to their anchors; and when Camillus was sent to the Capitol, through the Tiber, during the siege by the Gauls, he had a life-preserver of cork under his dress.

The Cork Oak is indigenous, or at least abundant, in Portugal, Spain, part of the south of France, and Italy; on the opposite coast of the Mediterranean, and the Levant. Spain and Portugal supply the greater portion of the cork which is consumed in Europe. The cork

is the bark which the tree pushes outwards, as is common to all trees; but here the outer bark is of a larger quantity, and is more speedily renewed. When removed, there is a liber, or inner bark, below it, and from this the cork is re-produced in the course of a few years,while the tree is said to live longer, and grow more vigorously, than if the cork were not removed. The

first time that the cork is taken off, is when the tree is about fifteen years old. That crop is thin, hard, full of fissures, and consequently of little value; and the second, which is removed about ten years after, is also of an inferior quality. After this, the operation is repeated once in eight or ten years, the produce being greater in quantity, and superior in quality, each successive time. According to Duhamel, a cork tree thus barked will live a hundred and fifty years. The months of July and Augus are those which are chosen for removing the cork.

The bark is cleft longitudinally, at certain intervals, down to the crown of the root, with an axe, of which the handle terminates in a wedge; and a circular incision is then made from each extremity of the longitudinal cuts. The bark is then beaten, to detach it from the liber; and it is lifted up by introducing the wedged handle, taking care to leave sufficient of the inner laminæ upon the wood, without which precaution the tree would certainly die. The bark being thus removed, it is divided into convient lengths; and it is then flattened, and slightly charred, to contract the pores. This substance is the rough cork of commerce; and it is thus fit to be cut into floats, stoppers, shoe-soles, and other articles of domestic use, by the manufacturer. The cork of the best quality is firm, elastic, and of a slightly red colour Cork burned in vessels of a particular construction gives the substance called Spanish black.

MUSIC.

If there is a charm on earth, which, more than any other, serves to elevate the affections, to tranquilize the mind, and to enrapture the feelings, it is music. We speak of music as it should be, in its purest and most exalted sense; and not of those unhallowed strains, in the use of which music is polluted and degraded, by being made the vehicle and the stimulant of earthly and unholy passions. Music, in its best exercise, is a heavenly science, suited to the purest, the most evangelical and seraphic natures. As we look abroad into creation, we find every thing constructed on the most harmonious scale, and in many instances, melodies are continually breaking forth from the perfect works of God. The whisper of the breeze, and the roaring of the storm-the tinkling of the sea shells, as they are agitated by the regularly returning waves, and the dashing of the impetuous cataract-the song of the robin and the shriek of the eagle-all these, and a thousand other voices of animated existence, are full of melody and song. To the Poet of Nature, and the Worshipper of God, all things appear full of harmony, and seem

to be graduated to the most perfect scale of music. As a great poet has beautifully said—

From harmony, from heavenly harmony,
The universal scale began;

From harmony to harmony

Through all the compass of the notes it ran,
The diapason closing full in Man.

In an age so generally well informed as the present on most subjects, we deem it a waste of time and talent to employ any argument to prove that music is an elevated study, worthy of the cultivation of every pure, devout, and intelligent mind. No one who has read the Bible with an understanding heart-no one who has felt the exalting influence of music on his own mind-no one who has a heart attuned to melody, and capable of appreciating the harmony of existencies can doubt the propriety of cultivating music as a useful science-a valuable art. Referring to it only in its social relation, it possesses a property of elevation and refinement, which has power to soften obdurate feelings, and win the soul to the sympathies of gentle life. As a bard of social feelings has said—

Music! oh, how faint, how weak,

Language fades before thy spell!

Why should feeling ever speak,

When thou canst breathe her soul so well?

Friendship's balmy words may feign,

Loves are e'en more false than they;

Oh 'tis only music's strain

Can sweetly soothe, and not betray!

But music has a higher, a more enduring power. It is employed by the purest spirits in the worship of a Being worthy of the exercise of the most exalted feelings and capacities of the human and angelic mind.The Church, in all ages, under the old and new dispensations, has practised it-the universal testimony of devout hearts has given it a sanction and it has formed the employment of angelic beings in past existence, and we are taught to believe will constitute the exercise of purified spirits in future eternity.