XXXIX

Among Prerogative Instances I will put in the sixteenth place Instances of the Door or Gate, this being the name I give to instances which aid the immediate actions of the senses. Now of all the senses it is manifest that sight has the chief office in giving information. This is the sense, therefore, for which we must chiefly endeavor to procure aid. Now the aids to sight are of three kinds: it may be enabled to perceive objects that are not visible; to perceive them further off; and to perceive them more exactly and distinctly.

Of the first kind (not to speak of spectacles and the like, which serve only to correct or relieve the infirmity of a defective vision, and therefore give no more information) are those recently invented glasses which disclose the latent and invisible minutiae of bodies and their hidden configurations and motions by greatly increasing their apparent size; instruments by the aid of which the exact shape and outline of body in a flea, a fly, a worm, and also colors and motions before unseen, are not without astonishment discerned. It is also said that a straight line drawn with a pen or pencil is seen through such glasses to be very uneven and crooked, the fact being that neither the motion of the hand, though aided by a ruler, nor the impression of the ink or color, is really even, although the unevenness is so minute that it cannot be detected without such glasses. And here (as is usual in things new and wonderful) a kind of superstitious observation has been added, viz., that glasses of this sort do honor to the works of nature but dishonor to the works of art. The truth however is only this, that natural textures are far more subtle than artificial. For the microscope, the instrument I am speaking of, is only available for minute objects. So that if Democritus had seen one, he would perhaps have leaped for joy, thinking a way was now discovered of discerning the atom, which he had declared to be altogether invisible. The incompetency however of such glasses, except for minutiae alone, and even for them when existing in a body of considerable size, destroys the use of the invention. For if it could be extended to larger bodies, or to the minutiae of larger bodies, so that the texture of a linen cloth could be seen like network, and thus the latent minutiae and inequalities of gems, liquors, urine, blood, wounds, etc., could be distinguished, great advantages might doubtless be derived from the discovery.

Of the second kind are those other glasses discovered by the memorable efforts of Galileo, by the aid of which, as by boats or vessels, a nearer intercourse with the heavenly bodies can be opened and carried on. For these show us that the Milky Way is a group or cluster of small stars entirely separate and distinct, of which fact there was but a bare suspicion among the ancients. They seem also to point out that the spaces of the planetary orbits, as they are called, are not altogether destitute of other stars, but that the heaven begins to be marked with stars before we come to the starry sphere itself, although with stars too small to be seen without these glasses. With this instrument we can descry those small stars wheeling as in a dance round the planet Jupiter, whence it may be conjectured that there are several centers of motion among the stars. With this the inequalities of light and shade in the moon are more distinctly seen and placed, so that a sort of selenography can be made. With this we descry spots on the sun, and similar phenomena — all indeed noble discoveries, so far as we may safely trust to demonstrations of this kind, which I regard with suspicion chiefly because the experiment stops with these few discoveries, and many other things equally worthy of investigation are not discovered by the same means.

Of the third kind are measuring rods, astrolabes, and the like, which do not enlarge the sense of sight, but rectify and direct it. And if there are other instances which aid the remaining senses in their immediate and individual actions, and yet are of a kind which add nothing to the information already possessed; they are not to the present purpose, and therefore I have omitted to mention them.