82.  Of these visible points we see at all times an equal number.  It is every whit as great when our view is contracted and bounded by near objects as when it is extended to larger and remoter.  For it being impossible that one Minimum VISIBILE should obscure or keep out of sight mote than one other, it is a plain consequence that when my view is on all sides bounded by the walls of my study see just as many visible points as I could, in case that by the removal of the study-walls and all other obstructions, I had a full prospect of the circumjacent fields, mountains, sea, and open firmament:  for so long as I am shut up within the walls, by their interposition every point of the external objects is covered from my view:  but each point that is seen being able to cover or exclude from sight one only other corresponding point, it follows that whilst my sight is confined to those narrow walls I see as many points, or minima VISIBILIA, as I should were those walls away, by looking on all the external objects whose prospect is intercepted by them.  Whenever therefore we are said to have a greater prospect at one time than another, this must be understood with relation, not to the proper and immediate, but the secondary and mediate objects of vision, which, as hath been shown, properly belong to the touch.

83.  The visive faculty considered with reference to its immediate objects may be found to labour of two defects.  First, in respect of the extent or number of visible points that are at once perceivable by it, which is narrow and limited to a certain degree.  It can take in at one view but a certain determinate number of minima VISIBILIA, beyond which it cannot extend its prospect.  Secondly, our sight is defective in that its view is not only narrow, but also for the most part confused:  of those things that we take in at one prospect we can see but a few at once clearly and unconfusedly:  and the more we fix our sight on any one object, by so much the darker and more indistinct shall the rest appear.

84.  Corresponding to these two defects of sight, we may imagine as many perfections, to wit, 1st, that of comprehending in one view a greater number of visible points. 2DLY, of being able to view them all equally and at once with the utmost clearness and distinction.  That those perfections are not actually in some intelligences of a different order and capacity from ours it is impossible for us to know.

85.  In neither of those two ways do microscopes contribute to the improvement of sight; for when we look through a microscope we neither see more visible points, nor are the collateral points more distinct than when we look with the naked eye at objects placed in a due distance.  A microscope brings us, as it were, into a new world:  it presents us with a new scene of visible objects quite different from what we behold with the naked eye.  But herein consists the most remarkable difference, to wit, that whereas the objects perceived by the eye alone have a certain connexion with tangible objects, whereby we are taught to foresee what will ensue upon the approach or application of distant objects to the parts of our own body, which much conduceth to its preservation, there is not the like connexion between things tangible and those visible objects that are perceived by help of a fine microscope.