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,