FRANCIS BACON 7 



so as to have its bottom parallel with the surface of the water; it 

 thus carried down with it to the bottom of the sea all the air con- 

 tained in the tub. It stood upon three feet (like a tripod), being of 

 rather less height than a man, so that, when the diver was in want 

 of breath, he could put his head into the hollow of the tub, breathe, 

 and then continue his work. We hear that some sort of boat or 

 vessel has now been invented, capable of carrying men some distance 

 under water. Any bodies, however, can easily be suspended under 

 some such vessel as we have mentioned, which has occasioned our 

 remarks upon the experiment. 



Another advantage of the careful and hermetical closing of bodies 

 is this — not only the admission of external air is prevented (of which 

 we have treated), but the spirit of bodies also is prevented from 

 making its escape, which is an internal operation. For anyone 

 operating on natural bodies must be certain as to their quantity, and 

 that nothing has evaporated or escaped, since profound alterations 

 take place in bodies, when art prevents the loss or escape of any 

 portion, whilst nature prevents their annihilation. With regard to 

 this circumstance, a false idea has prevailed (which if true would 

 make us despair of preserving quantity without diminution), namely, 

 that the spirit of bodies, and air when rarefied by a great degree 

 of heat, cannot be so kept in by being enclosed in any vessel as not 

 to escape by the small pores. Men are led into this idea by the com- 

 mon experiments of a cup inverted over water, with a candle or 

 piece of lighted paper in it, by which the water is drawn up, and 

 of those cups which, when heated, draw up the flesh. For they 

 think that in each experiment the rarefied air escapes, and that its 

 quantity is therefore diminished, by which means the water or flesh 

 rises by the motion of connection. This is, however, most incor- 

 rect. For the air is not diminished in quantity, but contracted in 

 dimensions, nor does this motion of the rising of the water begin till 

 the flame is extinguished, or the air cooled, so that physicians place 

 cold sponges, moistened with water, on the cups, in order to increase 

 their attraction. There is, therefore, no reason why men should fear 

 much from the ready escape of air : for although it be true that the 

 most solid bodies have their pores, yet neither air, nor spirit, readily 

 suffers itself to be rarefied to such an extreme degree ; just^as-^ater 

 will not escape by a small chink. /vS^ ^-'4/ 



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