NOVUM ORGANUM. 313 



is warranted by the time of year, as is the case when the east or north 

 wind blows ; just as seasons of an opposite character occur when the 

 south and west winds prevail. So a tendency to rain (especially during 

 whiter) accompanies a warm season ; while, on the other hand, frost 

 accompanies cold weather. 



To the Twelfth. 



18. Is subjoined, ns negative, air confined in caverns during summer. 

 But concerning confined air a diligent inquiry must by all means be 

 made. For, in the first place, doubt arises, and not without cause, as 

 to what is the nature of air, as regards heat and cold, in its own proper 

 nature. Now air receives its heat from the impression of the heavenly 

 bodies, and its cold perhaps from the evaporation of the earth ; and 

 again in the mid region of the air (as it is called) from cold vapours 

 and snows, so that no opinion can be formed as to the nature of air 

 from the examination of portions of it which are at large and exposed, 

 but a truer judgment might be formed by examining it when confined. 

 Hut it is also necessary that the air should be confined in a vessel of 

 such material as shall neither itself imbue the air with heat or cold of 

 its own nature, nor easily admit the influence of the external atmo 

 sphere ; and therefore let experiment be made in an earthen jar 

 wrapped in several folds of leather to protect it from the external air ; 

 let it remain for three or four days in a vessel carefully closed ; and 

 on the opening of the vessel, the result may be tested either by the 

 application of the hand, or by means of a glass properly graduated. 



To the Thirteenth. 



19. There exists a similar doubt whether the warmth in wool, skins, 

 feathers, and the like, arises from some slight degree of heat inherent 

 in them, inasmuch as they arc animal excretions, or from a certain 

 fatness and oiliness, which is of a nature akin to warmth, or simply 

 from the confinement and separation of the air, as was mentioned in 

 the last article. For all air, when cut off from communication with the 

 external atmosphere, seems to have in it some warmth. And so let 

 experiment be made on fibrous substances made of linen, but not of 

 wool, feathers, or silk, which are animal excretions. It must abo be 

 remarked that all powders (in which air is clearly enclosed) are less 

 &amp;lt; old than the bodies before they are pulveri/ed, as also we think that 

 all foam (as containing air) is less cold than the liquid itself. 



To the Fourteenth. 



20. To this no negative is subjoined. For nothing is found among 

 us, either tangible or spiritual, which when put to the fire does not 

 take up heat. There is, however, this difference, that some things 

 take up heat more quickly, as air, oil, and water ; othcss more slowly, 

 as stone and metals. But this belongs to the Table of Degrees. 



To the Fifteenth. 



21. The only negative subjoined to this Instance, is that it should 



