Try to measure that distance! Contemporary science is beginning to penetrate a little into this invisible world, and you know that it has just calculated the vibrations below 458 billions (these are the caloric invisible rays) and the vibrations above 727 billions (these are the chemical rays, also equally invisible to the human eye). Scientific methods can enlarge the sphere of the perceptions but a little; you remain isolated in the midst of infinitude. Moreover, an endless number of other vibrations exist in nature which have no _correspondence_ with your organisation, and therefore cannot be received by you, _consequently you remain for ever utterly ignorant of them_. Did you possess other strings to your lyre--ten, a hundred, a thousand--the harmony of nature could more completely translate itself to you, each of the myriad vibrations according to their kind. You would perceive a number of facts which are certainly passing around you, whose very existence you cannot even now guess, and in place of two dominant notes you would be conscious of the grand concert of harmonies everywhere about you. But although thus ignorant, you are unconscious of it, because all around you are equally ignorant, and therefore it is impossible to compare your limited faculties with those of beings much more highly organised. [Sidenote: Were the eye a combined spectroscope and telescope, it would see the chemical elements composing bodies.] The senses you do possess suffice, however, to indicate the existence of other senses, not only more powerful, but of a totally different order. By the sense of touch, for example, you can, it is true, feel the sensation of _heat_; but it is easy to conceive the existence of a special sense, analogous to that by which light reveals to you the aspect of exterior objects, and which would render man capable of judging of the form and substance of an object, its interior structure, and other qualities, by the action of the caloric waves radiating from it. The same reasoning would hold good on the subject of _electricity_. You could equally well conceive the existence of a sense, endowing the eye with the powers of a spectroscope and telescope in one, thus enabling it to see the _chemical_ elements, of which bodies are composed. Thus already, from a scientific point of view, you have sufficient ground for imagining modes of perception, quite different from those which characterise human beings. These faculties exist in other worlds, and there are endless ways of perceiving the action of the forces of nature. [Sidenote: Our terrestrial senses are limited.]