What has not man effected by the boldness of his conceptions and the adventurousness of his spirit? The achievements of human genius have appeared so incredible, till they were thoroughly examined, and slowly established their right to general acceptance, that the great heroes of intellect were universally regarded by their contemporaries as dealers in magic, and implements of the devil. The inventor of the art of printing, that glorious instrument for advancing the march of human improvement, and the discoverer of the more questionable art of making gunpowder, alike suffered under this imputation. We have rendered the seas and the winds instruments of our pleasure, "exhausted the old world, and then discovered a new one," have drawn down lightning from heaven, and exhibited equal rights and independence to mankind. Still however it is incumbent on us to be no less wary and suspicious than we are bold, and not to imagine, because we have done much, that we are therefore able to effect every thing. As was stated in the commencement of this Essay, we know our own sensations, and we know little more. Matter, whether in its primary or secondary qualities, is certainly not the sort of thing the vulgar imagine it to be. The illustrious Berkeley has taught many to doubt of its existence altogether; and later theorists have gone farther than this, and endeavoured to shew, that each man, himself while he speaks on the subject, and you and I while we hear, have no conclusive evidence to convince us, that we may not, each of us, for aught we know, be the only thing that exists, an entire universe to ourselves. We will not however follow these ingenious persons to the startling extreme to which their speculations would lead us. But, without doing so, it will not misbecome us to be cautious, and to reflect what we do, before we take a leap into illimitable space. SECTION II. "The sun," we are told, "is a solid body, ninety-five millions of miles distant from the earth we inhabit, one million times larger in cubic measurement, and to such a degree impregnated with heat, that a comet, approaching to it within a certain distance, was by that approximation raised to a heat two thousand times greater than that of red-hot iron." It will be acknowledged, that there is in this statement much to believe; and we shall not be exposed to reasonable blame, if we refuse to subscribe to it, till we have received irresistible evidence of its truth. It has already been observed, that, for the greater part of what we imagine we know on the surface or in the bowels of the earth, we have, or may have if we please, the evidence of more than one of our senses, combining to lead to the same conclusion. For the propositions of astronomy we have no sensible evidence, but that of sight, and an imperfect analogy, leading from those visible impressions which we can verify, to a reliance upon those which we cannot.