174 NOVUM ORGANUM. 



distance, certainly act within definite distances, which are 

 well ascertained by nature : so that there is a limit depend 

 ing either on the mass or quantity of the bodies, the vigour 

 or faintness of the powers, or the favourable or impeding 

 nature of the medium, all of which should be taken into 

 account and observed. We must also note the boundaries 

 of violent motions, such as missiles, projectiles, wheels, 

 and the like, since they are also manifestly confined to 

 certain limits. 



Some motions and virtues are to be found of a directly 

 contrary nature to these, which act in contact but not at a 

 distance ; namely, such as operate at a distance, and not in 

 contact, and again act with less force at a less distance, and 

 the reverse. Sight, for instance, is not easily effective in 

 contact, but requires a medium and distance ; although I re 

 member having heard from a person deserving of credit, that 

 in being cured of a cataract (which was done by putting a 

 small silver needle within the first coat of the eye to remove 

 the thin pellicle of the cataract, and force it into a corner 

 of the eye), he had distinctly seen the needle moving across 

 the pupil. Still, though this may be true, it is clear that 

 large bodies cannot be seen well or distinctly, unless at the 

 vertex of a cone, where the rays from the object meet at 

 some distance from the eye. In old persons the eye sees 

 better if the object be moved a little farther and not nearer. 

 Again, it is certain, that in projectiles the impact is not so 

 violent at too short a distance as a little afterwards.^ Such 

 are the observations to be made on the measure of motions 

 as regards distance. 



There is another measure of motion in space which must 

 not be passed over, not relating to progressive but spherical 

 motion ; that is, the expansion of bodies into a greater, or 

 their contraction into a lesser sphere. For in our measure 

 of this motion we must inquire, what degree of compres 

 sion or extension bodies easily and readily admit of, accord 

 ing to their nature, and at what point they begin to resist 

 it, so as, at last, to bear it no further ; as when an inflated 

 bladder is compressed, it allows a certain compression of 

 the air, but if this be increased, the air does not suffer it, 

 and the bladder is burst. 



We have proved this by a more delicate experiment. We 

 took a metal bell, of a light and thin sort such as is used 

 for salt-cellars, and immerged it in a basin of water, so as 



* Query. 



