But, in proportion as we compare the impressions made upon our organs of sight with the impressions made on the other senses, we come gradually to connect with the objects we see the idea of distance. I put out my hand, and find at first that an object of my sense of sight is not within the reach of my hand. I put out my hand farther, or by walking advance my body in the direction of the object, and I am enabled to reach it. From smaller experiments I proceed to greater. I walk towards a tree or a building, the figure of which presents itself to my eye, but which I find upon trial to have been far from me. I travel towards a place that I cannot see, but which I am told lies in a certain direction. I arrive at the place. It is thus, that by repeated experiments I acquire the idea of remote distances. To confine ourselves however to the question of objects, which without change of place I can discover by the sense of sight. I can see a town, a tower, a mountain at a considerable distance. Let us suppose that the limit of my sight, so far as relates to objects on the earth, is one hundred miles. I can travel towards such an object, and thus ascertain by means of my other senses what is its real distance. I can also employ certain instruments, invented by man, to measure heights, suppose of a tower, and, by experiments made in ways independent of these instruments, verify or otherwise the report of these instruments. The height of the Monument of London is something more than two hundred feet. Other elevations, the produce of human labour, are considerably higher. It is in the nature of the mind, that we conclude from the observation that we have verified, to the accuracy of another, bearing a striking analogy to the former, that we have not verified. But analogy has its limits. Is it of irresistible certainty, or is it in fact to be considered as approaching to certainty, because we have verified an observation extending to several hundred feet, that an observation extending to ninety-five millions of miles, or to the incredible distances of which Herschel so familiarly talks, is to be treated as a fact, or laid down as a principle in science? Is it reasonable to consider two propositions as analogous, when the thing affirmed in the one is in dimension many million times as great as the thing affirmed in the other? The experience we have had as to the truth of the smaller, does it authorise us to consider the larger as unquestionable? That which I see with a bay of the sea or a wide river between, though it may appear very like something with which I am familiar at home, do I immediately affirm it to be of the same species and nature, or do I not regard it with a certain degree of scepticism, especially if, along with the resemblance in some points, it differs essentially, as for example in magnitude, in other points? We have a sensation, and we enquire into its cause. This is always a question of some uncertainty. Is its cause