Little being known to Swedenborg, as indeed little is known to the astronomers of our own time, about Mercury, we find little in the visions relating to that planet which possesses any scientific interest. He asked the inhabitants who were brought to him in visions about the sun of the system, and they replied that it looks larger from Mercury than as seen from other worlds. This of course was no news to Swedenborg. They explained further, that the inhabitants enjoy a moderate temperature, without extremes of heat or cold. 'It was given to me,' proceeds Swedenborg, 'to tell them that it was so provided by the Lord, that they might not be exposed to excessive heat from their greater proximity to the sun, since heat does not arise from the sun's nearness, but from the height and density of the atmosphere, as appears from the cold on high mountains even in hot climates; also that heat is varied according to the direct or oblique incidence of the sun's rays, as is plain from the seasons of winter and summer in every region.' It is curious to find thus advanced, in a sort of lecture addressed to visionary Mercurials, a theory which crops up repeatedly in the present day, because the difficulty which suggests it is dealt with so unsatisfactorily for the most part in our text-books of science. Continually we hear of some new paradoxist who propounds as a novel doctrine the teaching that the atmosphere, and not the sun, is the cause of heat. The mistake was excusable in Swedenborg's time. In fact it so chanced that, apart from the obvious fact on which the mistake is usually based—the continued presence, namely, of snow on the summits of high mountains even in the torrid zone—it had been shown shortly before by Newton, that the light fleecy clouds seen sometimes even in the hottest weather above the wool-pack or cumulus clouds are composed of minute crystals of ice. Seeing that these tiny crystals can exist under the direct rays of the sun in hot summer weather, many find it difficult to understand how those rays can of themselves have any heating power. Yet in reality the reasoning addressed by Swedenborg to his Mercurial friends was entirely erroneous. If he could have adventured as far forth into time as he did into space, and could have attended in the spirit the lectures of one John Tyndall, a spirit of our earth, he would have had this matter rightly explained to him. In reality the sun's heat is as effective directly at the summit of the highest mountain as at the sea-level. A thermometer exposed to the sun in the former position indicates indeed a slightly higher temperature than one similarly exposed to the sun (when at the same altitude) at the sea-level. But the air does not get warmed to the same degree, simply because, owing to its rarity and relative dryness, it fails to retain any portion of the heat which passes through it.
It is interesting to notice how Swedenborg's scientific conceptions of the result of the (relatively) airless condition of our moon suggested peculiar fancies respecting the lunar inhabitants. Interesting, I mean, psychologically: for it is curious to see scientific and fanciful conceptions thus unconsciously intermingled. Of the conscious intermingling of such conceptions instances are common enough. The effects of the moon's airless condition have been often made the subject of fanciful speculations. The reader will remember how Scheherazade, in 'The Poet at the Breakfast Table,' runs on about the moon. 'Her delight was unbounded, and her curiosity insatiable. If there were any living creatures there, what odd things they must be. They couldn't have any lungs nor any hearts. What a pity! Did they ever die? How could they expire if they didn't breathe? Burn up? No air to burn in. Tumble into some of those horrid pits, perhaps, and break all to bits. She wondered how the young people there liked it, or whether there were any young people there. Perhaps nobody was young and nobody was old, but they were like mummies all of them—what an idea!—two mummies making love to each other! So she went on in a rattling, giddy kind of way, for she was excited by the strange scene in which she found herself, and quite astonished the young astronomer with her vivacity.' But Swedenborg's firm belief that the fancies engendered in his mind were scientific realities is very different from the conscious play of fancy in the passage just quoted. It must be remembered that Swedenborg regarded his visions with as much confidence as though they were revelations made by means of scientific instruments; nay, with even more confidence, for he knew that scientific observations may be misunderstood, whereas he was fully persuaded that his visions were miraculously provided for his enlightenment, and that therefore he would not be allowed to misunderstand aught that was thus revealed to him.
'It is well known to spirits and angels,' he says, 'that there are inhabitants in the moon, and in the moons or satellites which revolve about Jupiter and Saturn. Even those who have not seen and conversed with spirits who are from them entertain no doubt of their being inhabited, for they, too, are earths, and where there is an earth there is man; man being the end for which every earth exists, and without an end nothing was made by the Great Creator. Every one who thinks from reason in any degree enlightened, must see that the human race is the final cause of creation.'
The moon being inhabited then by human beings, but being very insufficiently supplied with air, it necessarily follows that these human beings must be provided in some way with the means of existing in that rare and tenuous atmosphere. Tremendous powers of inspiration and expiration would be required to make that air support the life of the human body. Although Swedenborg could have had no knowledge of the exact way in which breathing supports life (for Priestley was his junior by nearly half a century), yet he must clearly have perceived that the quantity of air inspired has much to do with the vitalising power of the indraught. No ordinary human lungs could draw in an adequate supply of air from such an atmosphere as the moon's; but by some great increase of breathing power it might be possible to live there: at least, in Swedenborg's time there was no reason for supposing otherwise. Reason, then, having convinced him that the lunar inhabitants must possess extraordinary breathing apparatus, and presumably most powerful voices, imagination presented them to him accordingly. 'Some spirits appeared overhead,' he says, 'and thence were heard voices like thunder; for their voices sounded precisely like thunder from the clouds after lightning. I supposed it was a great multitude of spirits who had the art of giving voices with such a sound. The more simple spirits who were with me derided them, which greatly surprised me. But the cause of their derision was soon discovered, which was, that the spirits who thundered were not many, but few, and were as little as children, and that on former occasions they (the thunderers) had terrified them by such sounds, and yet were unable to do them the least harm. That I might know their character, some of them descended from on high, where they thundered; and, what surprised me, one carried another on his back, and the two thus approached me. Their faces appeared not unhandsome, but longer than those of other spirits. In stature they were like children of seven years old, but the frame was more robust, so that they were like men. It was told me by the angels that they were from the moon. He who was carried by the other came to me, applying himself to my left side under the elbow, and thence spoke. He said, that when they utter their voices they thunder in this way,'—and it seems likely enough that if there are any living speaking beings in the moon, their voice, could they visit the earth, would be found to differ very markedly from the ordinary human voice. 'In the spiritual world their thunderous voices have their use. For by their thundering the spirits from the moon terrify spirits who are inclined to injure them, so that the lunar spirits go in safety where they will. To convince me the sound they make was of this kind, he (the spirit who was carried by the other) retired, but not out of sight, and thundered in like manner. They showed, moreover, that the voice was thundered by being uttered from the abdomen like an eructation. It was perceived that this arose from the circumstance that the inhabitants of the moon do not, like the inhabitants of other earths, speak from the lungs, but from the abdomen, and thus from air collected there, the reason of which is that the atmosphere with which the moon is surrounded is not like that of other earths.'
In his intercourse with spirits from Jupiter, Swedenborg heard of animals larger than those that live on the earth. It has been a favourite idea of many believers in other worlds than ours, that though in each world the same races of animals exist, they would be differently proportioned; and there has been much speculation as to the probable size of men and other animals in worlds much larger or much smaller than the earth. When as yet ideas about other worlds were crude, the idea prevailed that giants exist in the larger orbs, and pygmies in the smaller. Whether this idea had its origin in conceptions as to the eternal fitness of things or not, does not clearly appear. It seems certainly at first view natural enough to suppose that the larger beings would want more room and so inhabit the larger dwelling-places. It was a pleasing thought that, if we could visit Jupiter or Saturn, we should find the human inhabitants there
In bigness to surpass earth's giant sons;
but that if we could visit our moon or Mercury, or whatever smaller worlds there are, we should find men
Now less than smallest dwarfs, in narrow room
Throng numberless, like that pygmæan race
Beyond the Indian mount; or fairy elves,
Whose midnight revels, by a forest side
Or fountain, some belated peasant sees,
Or dreams he sees.
Later the theory was started that the size of beings in various worlds depends on the amount of light received from the central sun. Thus Wolfius asserted that the inhabitants of Jupiter are nearly fourteen feet high, which he proved by comparing the quantity of sunlight which reaches the Jovians with that which we Terrenes receive. Recently, however, it has been noted that the larger the planet, the smaller in all probability must be the inhabitants, if any. For if there are two planets of the same density but unequal size, gravity must be greater at the surface of the larger planet, and where gravity is great large animals are cumbered by their weight. It is easy to see this by comparing the muscular strength of two men similarly proportioned, but unequal in height. Suppose one man five feet in height, the other six; then the cross section of any given muscle will be less for the former than for the latter in the proportion of twenty-five (five times five) to thirty-six (six times six). Roughly, the muscular strength of the bigger man will be half as great again as that of the smaller. But the weights of the men will be proportioned as 125 (five times five times five) to 216 (six times six times six), so that the weight of the bigger man exceeds that of the smaller nearly as seven exceeds four, or by three-fourths. The taller man exceeds the smaller, then, much more in weight than he does in strength; he is accordingly less active in proportion to his size. Within certain limits, of course, size increases a man's effective as well as his real strength. For instance, our tall man in the preceding illustration cannot lift his own weight as readily as the small man can lift his; but he can lift a weight of three hundred pounds as easily as the small man can lift a weight of two hundred pounds. When we get beyond certain limits of height, however, we get absolute weakness as the result of the increase of weight. Swift's Brobdingnags, for instance, would have been unable to stand upright; for they were six times as tall as men, and therefore each Brobdingnag would have weighed 216 times as much as a man, but would have possessed only thirty-six times the muscular power. Their weight would have been greater, then, in a sixfold greater degree than their strength, and, so far as their mere weight was concerned, their condition would have resembled that of an ordinary man under a load five times exceeding his own weight. As no man could walk or stand upright under such a load, so the Brobdingnags would have been powerless to move, despite, or rather because of, their enormous stature. Applying the general considerations here enunciated to the question of the probable size of creatures like ourselves in other planets, we see that men in Jupiter should be much smaller, men in Mercury much larger, than men on the earth. So also with other animals.
But Swedenborg's spirit visitors from these planets taught differently. 'The horses of our earth,' he says, 'when seen by the spirits of Jupiter, appeared to me smaller than usual, though rather robust; which arose from the idea those spirits had respecting them. They informed me that among them there are animals similar, though much larger; but that they are wild, and in the woods, and that when they come in sight they cause terror though they are harmless; they added that their terror of them is natural or innate.'[28] On the other hand the inhabitants of Mercury, who might be thirteen feet high yet as active as our men, appeared slenderer than Terrene men. 'I was desirous to know,' says Swedenborg, 'what kind of face and person the people in Mercury have, compared with those of the people on our earth. There therefore stood before me a female exactly resembling the women on that earth. Her face was beautiful, but it was smaller than that of a woman of our earth; she was more slender, but of equal height; she wore a linen head-dress, not artfully yet gracefully disposed. A man also was presented. He, too, was more slender than the men of our earth; he wore a garment of deep blue, closely fitted to his body without folds or flowing skirts. Such, I learn, were the personal form and costume of the humans of that earth. Afterwards there was shown me a species of the oxen and cows, which did not indeed differ much from those on our earth, except that they were smaller, and made some approach to the stag and hind species.' We have seen, too, that the lunar spirits were no larger than children seven years old.