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LESSON CII.

Influence of the Moon on the Human Body.

FORMERLY there were imputed to the moon certain influences upon the body, which were only calculated to raise superstition and groundless fears. The gardener would not plant till he had consulted the moon. The ploughman deferred sowing till he was certain of its happy influence. Sick people attended, with superstitious exactness, to the changes of the moon; and the physicians themselves observed it in their prescriptions. By degrees these prejudices have been removed ; and it is our duty to make it still more universal, and to endeavour to banish, as much as we can, the superstition of old times. In regard to the influence of the moon on our bodies, the safest way is to preserve a medium: for as it would be irrational to attribute to that planet too great a power over the human body, so it would be no less rash to deny it any effect. It must in reality be allowed, that the moon occasions great changes in the air, and of course may produce some in our bodies. The moon causes such considerable alteration and motion in the higher atmosphere, that earthquakes, winds, heat, cold, vapours, and fogs, result from thence; and in that case, the health of our body will, in some measure, depend on the influence of the moon. The power this planet has over the human body, is founded on an undeniable principle, which is, that our health greatly depends on the weather, and the sort of air we breathe; and it is certain that the moon causes many alterations in the atmosphere. Perhaps there may be even a flux and reflux in the human body occasioned by the moon, like that in the air and sea.

In general, it is a principle we ought to admit

to the glory of our Creator, that throughout all. natural things there are certain connexions which influence, in different ways, the animal economy. There are, without doubt, many wonders in the atmosphere, still remaining unknown to us, which cause many considerable revolutions in nature. Who knows if some of the phenomena of the natural world, which we do not think of, or which we attribute to other causes, may not depend on the moon ? Perhaps the light it affords us in the night is one of the least of the purposes for which the Almighty formed this planet. Perhaps its being so near our earth was to produce certain effects on us, which the other celestial bodies, from their distance, could not do. It is at least certain, that every thing in the universe has relation, more or less, to our globe; and this is what renders the world a master-piece of the Divine Wisdom.

LESSON CIII.

The Ignis Fatuus. The Ignis Fatuus are little light flames which play in the air, only a few feet from the ground, and appear to go here and there, and every where, These fires seem sometimes to disappear and go out all at once, probably when bushes or trees conceal their light; but they kindle again immediately in other places. They are not common in cold coun tries; and it is said that in winter they chiefly appear in marshy places. In Spain, Italy, and other hot countries, they are known at all seasons, and neither rain nor wind extinguishes them. They are frequently seen where there are putrid plants, or animal matter, as in church-yards, shores, and in marshy grounds. There have been two few experiments made on these sorts of ethereal fires, to determine precisely as to the nature of them. But the places where they are generally seen, may give rise to probable conjectures; for as they scarcely ever appear but in marshy countries, it is natural to suppose them sulphureous vapours which take fire. It is known that carcasses and rotten plants sometimes cast out light. Perhaps vapours 'condensed by the cold of the night take the appearance of the Ignis Fatuus. Perhaps it may be the effect of a slight electricity, produced by the interior motion of the vapours which rise in the air. Horses, dogs, cats, and even men, may become so, electrical as to cast out sparks of fire, when they are rubbed, or other wise put in motion. May not this be the case with some parts of the earth? It may so happen, that in some circumstances, a field shall be electrified in some parts of it, and then it is not surprising that it should appear luminous. Even the air may occasion the Ignis Fatuus, when it is electrified to a certain degree. If the manner of their being produced is still doubtful, we are certain, at least, that they proceed from natural causes, and consequently are not obliged to have recourse to superstition, What may have given rise to this superstitious idea, is the observing that the Ignis Fatuus follows all the ways of the wind, and thus flies from those who pursue it: and, on the contrary, follows those who try to avoid it, and fixes on carriages which go swiftly. But the reason of this phenomenon is very evident: for the person who pursues this flame drives the air, and consequently the fire, before him: whereas the person who flies, leaves an empty space, which the ambient air fills up continually. This produces a current of air between him and the fire, and of course draws it after him. This is the reason we observe it stop when the person ceases to

run. We might spare ourselves many fears, if we would take the trouble to examine the objects which frighten us, and seek for their natural causes.

LESSON CIV.

Of Minerals.

In order to provide mankind wholesome and convenient dwellings, they require many materials. If these materials had been spread over the surface of the earth, it would have been entirely covered with them, and there would not have been room for the animals and plants. Our earth is happily free from such incumbrance. The ground is left free to be cultivated and enjoyed by its inhabitants.

Minerals may properly be divided into four classes of very distinct characters. The first includes fossils. We give that name to minerals which cannot be dissolved either in water or oil, and are not malleable, and which bear the fire without losing any substance in it. To this class belong not only the simple earths, but the stones also which are composed of them. There are two sorts of stones, the precious and the common stones. The latter are very numerous, and present as masses different in form, size, colour, and hardness, according to the earth, sulphur, &c. of which they are composed. Precious stones also differ very much. Some are perfectly transparent, and appear to be most simple. Others are more or less opaque, according as they are composed more or less of heterogeneous particles. The salts form the second class of minerals. It comprehends bodies which water dissolves, and which

produce a relish. 6? They are divided into acids, which are sharp and sour: "and into alkalies, which leave an acrid, burnt, lixivius taste on the tongue. These have the property of changing into green the blue juice or dyes of vegetables. From the just and exact mixture of these two different salts, tempered by each other, proceed the neutral or middling salts: such as the common kitchen salt, which is either taken out of the earth, or prepared with sea-water, or obtained by the evaporation of salt-water boiled in great caldrons. All these salts together are one of the chief causes of the vegetation of plants. They possibly serve also to unite and fix them, as well as all the other compound bodies, and they occasion fermentation, the effects of which are so numerous and different. The third class of minerals comprehends inflammable bodies, to which are given the name of bitumens. They melt in the fire; and when they are pure, they dissolve in oil, but never in water. They are distinguished from other minerals by the inflammable substance they contain more of than any other, and which renders combustible the bodies they mix with, if in sufficient quantity. The fourth class of minerals is the metals. They are much heavier than the rest, and become Auid in the fire, but resume their solid state when cold. They are bright, and are capable of being distended under the hammer. There are some metals, which, though melted in the fire, do not diminish in weight, or un dergo any other sensible alteration. This gives them the name of perfect metals. There are two of this order, viz. gold and silver. The metals called imperfect are reduced more or less quickly by fire, and generally change into a calx. One of these (lead) has the property of changing into glass, and of vitrifying also all the other metals, except gold and silver 29 There are five of the imperfect metals : quicksilver, n lead, copper, iron, and tin. Lastly, there are bodies which differ from these metals by

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