Nor is the distance known between any two stars, however close they appear to one another. You would think, if you judge by mere ocular demonstration, that the Pleiades almost touch one another. There is a star which seems to rest on one of the stars forming the tail of the Great Bear; you can hardly, with the mere eye, discern that part of the heavens which divides them; they make together, as it were, but one double star; yet, if the most skilful astronomers cannot, with all their art, find out the distance between these stars, how far asunder must two stars be which appear remote from each other, and how much farther yet the two polar stars.[885] How prodigiously long must be that line which reaches from one to another! How immense the circle of which this line is the diameter! And how can we fathom what cannot be fathomed, and represent to ourselves the volume of the globe, of which this circle is but a section? Shall we still wonder that these stars, of such immensurable size, seem no larger to us than so many sparks? Shall we not rather admire that from such a height the least appearance of them should reach our eye, and that they can be discerned at all? And, indeed, the quantity of stars which escape our vision is countless. It is true, we limit the number of the stars, but that is only of stars visible to us, for how should we number those we cannot see; those, for example, which constitute the Milky Way,—that luminous tract, which, on a clear night, can be observed in the sky from north to south,—and which, by their immensurable height, cannot be distinguished individually by our optics, and at most produce but a white mark in that part of the heavens where they are placed?[886]