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One admirable feature in Rome is its fountains. They are really splendid. Soon after leaving the railway station you come to one representing Moses striking the rock, and the water gushes out in abundance. It is no mere spurt, but a stream two yards wide. Many of the others are still more striking. One has the form of a ship with water spouting out in all directions; another like a great rock with water flowing out of every part. On a warm day it gives a sense of cool delight to look at them. Then the two in the approach to St. Peter's, like the two in the Place de la Concorde at Paris, are things of beauty and of joy of which you never tire.
The baths of Old Rome cannot be too highly admired and commended; the modern city has entirely fallen away in that respect. Those whose remains are visible at the present day are those which were attached to Imperial palaces, but the whole people used to bathe very freely. The ruins of the baths of Caracalla on the Appian Way are still stupendous. They are about 300 yards long, 100 wide, and a 100 feet high. The walls, which are of the usual narrow bricks of Roman manufacture, are as strong as castle walls. They were cased inside with marble. The space was divided for three baths-cold, tepid, and warm. Noble pillars and statues adorned each bath, of which you see the feet and many remains. The water was brought 18 miles, and you see the aqueduct by which it came.
This was a creation of power and luxury; but what one could do then, surely many might achieve now, and it would be a benefit of immense value if every young person in this country could wash all over at least once a week, and learn to swim. The advance in health and in safety would be unspeakably great, and if I might in any way add to the disposition to do this, it would amply repay me for a visit to Old Rome.
The catacombs of Rome have formed of late years an extremely interesting feature of the ancient city. In the second and third centuries, when the Christians were subjects of annoyance, and sometimes of persecution, they withdrew to underground passages formed in old sandpits and quarries, and there held their worship secure from insults, and there buried their dead. These passages are miles in length.
This condition of subterraneous habitation continued until the time of Constantine, when Christianity became the religion of the state, and when the necessity for hiding ceased.
After the sixth century, when Rome for ages became the scene of fierce struggles, often besieged and often taken, the catacombs got their entrances covered up, and were forgotten. In the sixteenth century they were re-discovered, and since then have been re-opened and explored from time to time. Thousands of epitaphs have been rescued, and are now fixed up in a gallery at the Vatican, in the Lateran Museum, and in other accessible positions; very few remain now under ground.
The interest of these epitaphs is very great, since they indicate the kind of Christianity which prevailed in the second and third centuries.
Having been covered up for more than a thousand years, they had been kept free from the corruptions which had been going on above ground.
We can touch this subject but briefly on account of the length of this article; but a few salient particulars will no doubt be felt to be important.
First, The Lord Jesus Christ is the only representation of the Deity that occurs, and He is commonly exhibited as the Good Shepherd.
Secondly, There is no figure of a crucifix; showing that it was the Saviour glorified and triumphant rather than the Saviour suffering, that was the object of meditation and adoration to the early Christians.
Thirdly,-There is no representation of the Virgin anywhere, in marked contrast with the way in which she has been magnified in after centuries, and obtruded in Papal countries everywhere as a semiDeity.
Fourthly,-The memorial slabs usually have a dove with an olive leaf in its mouth upon them, and often two doves, indicating that Christianity was a religion to produce the dove-like spirit, and to lead to peace, both on earth and in heaven.
Fifthly, There is no reference, so far as I know, to the resurrection of the body. Every expression on them indicates continued and exalted life, no coming up of the body.
We cannot close this paper without an expression of our admiration of the Divine Providence, which, right under the central seat of the Papacy, has preserved a record of purer ages and of better things; and thus in this instance, as in many others, enabled the New Dispensation to show that the Kingdom of God is like unto an householder that brought out of his treasures things new and old.
THE HISTORY OF A MOLECULE.
THE Scientific facts referred to in this note may be found stated more fully, and with beautiful clearness, in an address by Professor ClerkMaxwell, published in Nature, September 25, 1873.
A gallon of water may be divided into 70,000 drops, each weighing one grain. Each of these drops may be subdivided into parts of undetermined number and minuteness. Let us imagine that we have
as last arrived at our final step in the subdivision, and that we have found the droplet that is the smallest possible quantity of water. This is a molecule of water.
Divide it once more, and it ceases to be water, it resolves itself into three atoms, two of hydrogen and one of oxygen, and if it be true that hydrogen and oxygen are really elementary, then these atoms are finally indivisible.
The atomic theory, then, of Democritus of Abdera (2200 years ago), asserts that all matter is composed of elementary indivisible bodies called atoms. All compounds are now said to be composed of molecules, which are indivisible except by resolution into their elementary atoms, either separate or otherwise compounded. One example of this has already been given; as another, take a molecule of chalk. This is Ca, CO,, and on being divided resolves itself into a molecule of lime (Ca, O), and one of what is commonly called carbonic acid (CO). These molecules may again be resolved into two atoms of the metal calcium, two of oxygen, and one of carbon.
Lucretius maintained that atoms (the molecules of elementary substances) were in a state of everlasting unrest. This doctrine is now revived and extended to the molecules of compound bodies. Every molecule in a stationary block, say of granite, is continually in motion, though the motion of each is confined within less than microscopic limits. In liquids the molecular motion is not so limited; each molecule works its way throughout the whole mass. A lump of sugar at the bottom of a tumbler of water at rest, slowly dissolves, and then slowly, but surely, sweetens the whole liquid. This travelling of molecules (in this case, of sugar) throughout the whole of a fluid is called diffusion. Diffusion is very rapid in the case of gases and vapours, as is seen in the swiftness with which odours permeate the whole air of a room free from aërial currents. This process of diffusion, which goes on in gases, liquids, and some solids, is a convincing proof of the motion of molecules.
The study of molecular motion has been diligently prosecuted by many most distinguished physicists, and is still commanding the attention of the ablest experimentalists.
The flying molecules beat against every object placed among them, hence the pressure of the air and other gases. From any vessel remove one-half the contained air, and the strokes of the molecules against the sides will be reduced in number to one-half, so the pressure upon the sides will be diminished in the same proportion. This is Boyle's law of gaseous pressure. By heating a body the velocity of its atomic motion is increased and its molecules traverse longer paths. Hence bodies when heated expand; or, if confined, exert a greater pressure on the walls of the containing vessel. On this depends Charles's law, that solids expand when heated, liquids expand more, and gases expand most and uniformly, an equal expansion being produced in them by an equal increase of temperature. Were we to go
on stating, even thus concisely, the scientific importance of molecular motions, this article would become ill-adapted to the pages of this Magazine, and the narrow limits of our available space would not contain those reflections for the sake of which we write. We limit ourselves therefore to the mere statement of conclusions.
Dr. Joule calculates that the molecules of hydrogen travel at a velocity of 1859 metres (above 2000 yards) per second. If the molecules travelled all in the same direction they would produce a wind whose force would exceed that of the wind from a cannon's mouth. But they travel in different directions, and meeting us on every side, we are able to support ourselves. Moreover, they clash continually, and have their direction changed; their actual progress is therefore slow, though their pace is great. The actual length of path of the molecules of a gas is, roughly speaking, about one-tenth of a wave-length of light. Their collisions amount to thousands of millions
A cubical vessel whose side measures one centimetre (two-fifths of an inch) will contain, at the ordinary pressure, nineteen million million millions of molecules of any gas.
Now, compare in one or two particulars the molecules of hydrogen and oxygen. The molecule of hydrogen weighs about 7-100,000,000, 000,000,000,000ths of one grain, that of oxygen weighs exactly sixteen times as much. Ascertaining the velocity of the former, we find that that of oxygen is one-fourth as great. The length of the mean path of the former is to that of the latter as 965 is to 560.
These statements will suffice to illustrate the statement that throughout the universe each molecule bears the stamp of a metric system, so simple, so perfect, so beneficent in its results, as to compel our agreement with Professor Clerk-Maxwell, when he declares the molecules to have all the marks of manufactured articles; of articles, we add, manufactured evidently by a Being of fathomless wisdom, of infinite goodness, and of power whose resources are unrestricted. No wonder that Professor Tyndall should say, "In his manufactured articles, Professor Maxwell finds the basis of an induction which enables him to scale philosophic heights considered inaccessible by Kant, and to take the logical step from the atoms to their Maker."
There is only one more fact we have space for; the molecule, though indivisible, or conceived to be so, is not necessarily simple. Thus it is not a rigid body, it is the scene of perfectly characteristic internal motions, and by these it produces those effects which enable us by the use of the spectroscope to distinguish and identify the
several elements. Sodium has in every molecule two distinct motions, one slightly more frequent than the other, and these cause the double yellow band of sodium, or when they show themselves by absorption, they produce the double velvet-like band in the solar spectrum known as D. We wonder at such minute and frequent motions in a mere atom, and our wonder becomes adoration when we find that an iron molecule is a manufactured article, the scene of perpetual motions, so varied as to produce distinctive bands by hundreds, no one of which belongs to the spectrum of any other element. These internal molecular motions, moreover, are always present. Hydrogen just released from water, hydrogen pervading the solar atmosphere and forming the storm-tossed chromosphere, and hydrogen brought by meteorites from star-depths, and liberated in the laboratory from its iron fetters; in a word, hydrogen always has the same properties and the same internal molecular constitution. Each molecule has been made subject to the same conditions, and has been made by no process which we can call natural.
Some reader, perhaps, will fear for our orthodoxy, and ask, Does not Swedenborg tell us that the belief in monads or atoms rests on a fallacy of the senses? (A. C. 5084.) The reply to this is simple and complete. The opinion of the untaught and of many ancient philo-` sophers, that the sun moves daily around this earth is another of the "fallacies of sense" condemned in the same paragraph. But for all that, the phenomenon is familiarly spoken of, and now is by most men rightly understood. So when we are told that it is an error, that there are simple substances, and these are monads and atoms, the error is in the word simple. As Swedenborg points out in D. P. 6, "It is acknowledged by many that there is only one substance, which is also the first from which all things are; but it is not known what that substance is. It is thought to be so simple that nothing can be simpler, and that it can be compared to a point which has no dimensions, and that from an infinite number of such points the forms of dimension exist. This, however, is a fallacy, originating from the idea of space," etc. This condemned opinion is not the one we state. The molecular philosophy does not look back to the first substance, but merely to the first known substances, and finds them "the more full and complete" in proportion to their being "simpler and purer," and that "in a certain image," after a certain analogy and correspondence, "the Divine is in every one" of these first known created things. In his treatise on the Infinite, Swedenborg accepts the belief