second membrane, much thicker and stronger, adheres to the internal surface of the cranium; and between these is a third membrane, so very delicate and transparent, as to be scarcely perceptible. Besides these parts, each of which has a determinate place, there are others which are dispersed over the whole body, such as bones, arteries, veins, lymphatic vessels, muscles, and nerves. The bones are united together by joints, and serve to support the body, to render it capable of motion, and to preserve and protect the softer parts. Veins and arteries circulate the life-sustaining blood throughout the body. The nerves, of which ten principal pair are enumerated, are small white cords; they proceed from the brain, are distributed to every part of the body, and are the organs of sensation and motion. The whole body is full of pores, so small as to be imperceptible to the naked eye; and through these is continually exuding a subtile matter called the insensible perspiration. No less wisdom is manifested in the fluid than in the solid parts of the body. The blood, chyle, lymph, bile, marrow, and the different kinds of viscous and glutinous humours secreted by various glands; their different properties, their destination, effects, and the manner in which they are separated and prepared; their circulation and renovation; all bespeak the most astonishing art and the profoundest wisdom.

Let us now recapitulate all the excellencies of our structure. The bones, by their solidity and their joints, form the foundation of this beautiful superstructure; the ligaments are tendinous cords, which unite different parts together; the muscles are fleshy substances, which perform their functions like elastic springs; the nerves, which extend to the most distant parts of the body, communicate the power of sensation, and enable the different organs to perform their functions; whilst the arteries and veins, like inexhaustible rivulets, pour the life streams to every part. The centre of circulation is the heart, from and to which all the blood proceeds; and respiration is performed by means of the lungs. The stomach and intestines are the organs where the food undergoes those changes which are necessary for the support of life. The brain is the common centre from which the nerves proceed to communicate sensation to the body, and enable the senses to receive the impressions which they convey to the soul.

Adorable Creator! how wonderfully hast thou formed us! Though the heavens, which so magnificently display thy glory, were not to exist, though I was the only being upon the face of the earth, the admirable structure of my body alone would suffice to assure me of the immensity of thy power, and convince me of thy immeasurable wisdom! Let us, then, as often as we meditate upon this wonderful organization of our bodies, praise Him who has so formed us, and offer up our thanksgiving for his manifest goodness.

JUNE XXV.

ELECTRICITY.

From the numerous experiments which have been made upon the subject of electricity, no one can doubt the existence of a matter which, from its singular effects, has excited the attention of Europe. for more than half a century. It appears that this fluid is equally diffused through all bodies, but is so extremely subtile that we cannot perceive it, and we only know it to be present from the effects it produces when put in motion it rushes from one part to another to restore the interrupted equilibrium. It is necessary to distinguish two kinds of electric bodies; those in which the electric fluid may be excited by means of friction, and those which receive their electric power by communication with the former. The principal substances which compose the first class are glass, pitch, resin, sealing-wax, hair, silks, and air; to the second class belong water, metals, &c. Bodies of the first kind may be made capable of preserving the electric matter collected in them, whilst those of the second class lose it as soon as they receive it.* Machines have been invented, in which, by means of a wheel, a rapid rotation is given to a glass globe, or cylinder, upon which is placed a cushion of silk, against which, whilst whirling round, it rubs. By this friction the globe preserves its electric virtue, which may be extended to any distance by means of metallic bars, or chains which communicate with the glass. If, while the machine is working, we touch the chain, we immediately receive a shock; and, if the room is darkened, a luminous spark will be perceived. Let any number of persons join hands and form a circle, and by means of the chain make a communication with the machine; and they will all receive a shock at the same time, which may be made more or less violent. The electric fluid may be accumulated to such a degree as to kill by its discharge the largest animals.

This experiment is performed with several glass jars nearly filled with water, and which, connected together by chains, communicate with the glass globe before described. The water communicates to the internal surface of the jars a great quantity of electric matter, their external surface at the same time losing an equal quantity by means of its communication with some conducting body. A vivid flash, loud explosion, and a violent agitation, ignition of combustible matter, and the death of the subject of the experiment, are the consequences of this experiment.

Those substances mentioned in the first class, to which may be added diamonds, balsamic and bituminous bodies, as amber, sulphur, &c. the coverings of animals, as feathers, wool, bristles, silk, vitrified bodies, and all substances that, when rubbed, attract light bodies, are called electrics or non-conductors. Those on the contrary in which, when friction is employed, the electric fluid is not excited or put in motion, are called conductors or non-electrics; and they consist chiefly of metals, minerals, aqueous and spirituous liquids, living creatures, and animal and vegetable substances, as trees, plants, bones, shells, &c.

There are other effects which are common to all experiments of this kind; such as a sulphureous smell, an agitation in the air, a sudden flash, and the electric matter acquiring a new property. Some experiments have failed because the metallic rods which served as conductors were too angular and pointed. It has been suspected that the electric fluid in such cases was dissipated by means of the points; and this was confirmed when, on approaching the face or hand to the point of the rod, a copious stream of electric fluid emanated from them; it was also conjectured, that these points, which throw off the electric fluid, might attract it, and a number of experiments have since established it as a truth.

Electricity has been applied by physicians in many complaints with great success; and a still greater advantage which we derive from its investigation is the analogy which naturalists have discovered between electricity and lightning, which has given rise to new conjectures upon the nature of thunder; and has taught us to secure our buildings, by means of metallic rods, from the destruction they often suffer during a storm.

Thus we are continually receiving new solutions of the mysteries contained in the great works of nature; and from the success of these investigations we should be excited to more industry, and to pay greater attention to the works of the creation daily offered to our view.

JUNE XXVI.

MANNER IN WHICH THUNDER IS FORMED.

Formerly, and even to the beginning of the eighteenth century, it was commonly supposed that thunder was occasioned by the agitation of saline, sulphureous, and other substances contained in the air. It was imagined that there was the greatest resemblance between the effect of fire-arms and that of thunder and lightning. But all the means by which men endeavoured to explain and establish this system were not sufficient to do away the difficulties that presented themselves, nor to account for the fact. Since that period, however, the phenomena produced by the electric fluid have been more attentively observed, and a very different cause has been assigned to the formation of thunder. The great resemblance between it and electricity has convinced naturalists that they are produced by the same causes, and that electricity is in our hands what thunder is in nature. It will not be difficult to demonstrate this, even to those who are ignorant of natural philosophy, if they will only take the trouble to compare the effects of thunder with those of electricity.

The effects of thunder are known by peals heard at a greater or less distance, and by flashes of fire; buildings struck by it are often consumed by flames; men exposed to it become black, and appear

scorched, though there is sometimes no trace of fire, the violence of the stroke having killed them: their clothes are torn, they are thrown to some distance from the place in which they were, and frequently the part of the body which was struck is pierced with holes. Sometimes large stones are broken by the thunder, and its ravages are easily discoverable on the ground where it strikes.

Electricity presents us with similar effects, but in a less degree. When by means of water its force is increased, the electric flash is followed by a very evident commotion: the most compact bodies are perforated, birds and other small animals are deprived of life, and each flash is succeeded by a report. The stream of fire also, which passes from the points of electrified bodies with a hissing noise, is one of the phenomena observable in lightning; and with respect to velocity, there is still greater resemblance between thunder and electricity. If during a storm a sword or chain is suspended in the air by silken strings, they become electrified; and if the finger is advanced near them, sparks proceed from them with more or less force and brilliancy, according to the violence of the storm, and the distance of the electric cloud; in short, every effect of electricity is produced during a thunder-storm. From all these circumstances, we can no longer doubt that the air during a storm is highly electric, and that thunder and lightning are merely the effects of a violent electric fire.*

Thus all that appears supernatural in these phenomena, and the terror that they consequently excite, will be done away as we become better acquainted with the laws of nature. This should induce every one to acquire at least the first principles of natural philosophy. We should then no longer see fear and superstition enervate the mind, and paralyze our exertions in the investigation of nature. Let us employ the little light we have to dispel the fear which troubles us at the approach of a thunder-storm; and, amid the lightning's flash and the roaring of the tempests, we shall regard with a tranquil bosom the God of all, who rides in the whirlwind and directs the storm.' For however we inay be able to assign the causes of thunder upon just and invariable principles, drawn from natural philosophy, the phenomena are not less remarkable, and present some circumstances which are inexplicable, even to the most enlightened mind. It is sufficient for us to know that the nature of the air, and the peculiar properties of the surrounding atmosphere, render this phenomenon necessary that these storms are essential to the fertility of the earth, and should therefore excite us to render our tribute of praise and thanksgiving to the all-bountiful Creator.

* Lightning, then, is nothing more than the electric fluid contained in the clouds passing into other bodies, and thus interrupting the equilibrium, and producing concussions in the air, or that noise which we call thunder; and the reason that lightning is seen before the thunder is heard, is that light travels with a velocity inconceivably greater than sound.-E.

JUNE XXVII.

HERRINGS.

In this season of the year the herring-fishery begins on the coasts of England and Scotland; by which we shall soon receive a great abundance of fish, which supply the inhabitants with food during a considerable part of the year. Let us examine what is most important in the natural history of these fish.

An innumerable multitude of herrings live in the Icy sea, near the arctic pole; at a certain time they quit this abode, and arrive in shoals upon the coasts of England and Holland. The cause of this emigration is not yet ascertained: some suppose it is to escape from the whale, and other great fish of the Icy sea; others imagine that the prodigious multiplication of herrings is the cause of their taking these long voyages; that finding themselves too numerous under the northern ice, they are obliged to detach colonies to other places, that they may have a sufficiency of food for their support. Perhaps it is the desire of propagating their species, and a particular instinct, which leads them to places more favourable for their increase and preservation.

Whatever cause influences their motions, it is certain that immense shoals of herrings proceed from the north in the beginning of the year; for as early as the month of March the western wing of this aquatic army reaches the coasts of Iceland; they are there so extremely numerous, that upon plunging the bucket, with which they water the sails of the vessel, into the sea, they draw up great numbers of these fish. The eastern wing advances farther into the Baltic sea; one part of it stretches towards the North Cape, descends to the coast of Norway, and then enters the Baltic through the Sound. Another division steers for the northern point of Jutland; and afterwards enters into the Zuyder-zee, and passes thence into the Baltic, to return to its former station. The most numerous detachment of the eastern wing proceeds to the western coasts, and arrives at the Orkney islands, where the Dutch go to catch them. About the eighth of June the sea is there filled with them; they afterwards shape their course towards England and the coasts of Scotland, and fill all the bays and harbours with their fry. They then disappear, and those which have escaped the nets of the fishermen, and the numero large fish which prey upon them, most probably return northward to the place from whence they emigrated.

A single herring deposits at least ten thousand eggs in the sea upon the British coast, and this great fruitfulness of a single fish, among so many millions, makes what is reported of the Dutch fishery credible; they are said to take annually about two hundred millions of herrings, by which a great number of people are supported, and more than twenty millions of crowns added to the Dutch revenue.