314 NOVUM ORGANISM. 



be carefully noted that sparks are not elicited from flint and steel, or 

 any other hard substance, except when some particles are struck out 

 of the substance of the stone or metal ; and that the attrition of air 

 itself never generates sparks, as it is commonly thought ; and more 

 over that these sparks themselves, owing to the weight of the ignited 

 body, tend downward, rather than upwards, and on extinction turn 

 into a kind of sooty matter. 



To the Sixteenth. 



22. There is, we think, no negative subjoined to this Instance. For 

 no tangible body is found among us which does not clearly grow hot 

 under attrition, insomuch that the ancients imagined that the heavenly 

 bodies possessed no other power or means of generating heat than the 

 attrition of the air during their rapid and energetic rotation. But 

 under this head it must be further inquired whether bodies discharged 

 from machines (as cannon-balls) do not contract some degree of heat 

 from the percussion thereof, so as, after they have fallen, to be found 

 somewhat hot. But air in motion cools rather than heats, as in the 

 case of wind, blowing with bellows, and from the partially closed 

 mouth. But motion of this kind is not sufficiently rapid to excite 

 heat, and acts throughout the whole body, and not by particles, so 

 that it is not wonderful that it does not generate heat. 



To the Seventeenth. 



23. About this Instance a more diligent inquiry must be made. 

 For herbs and green and moist vegetables seem to have in them 

 some latent heat. But this heat is so slight as not to be perceived 

 by the touch when they are single, but only when they are collected 

 and confined, so that their spirits cannot escape into the air, but 

 rather cherish each other : whence there arises manifest heat, and 

 sometimes flame, in suitable matter. 



To the Eighteenth. 



24. About this Instance also a more diligent inquiry must be made. 

 For it appears that quick-lime, when sprinkled with water, conceives 

 heat, either from the condensation of the heat which was previously 

 dispersed (as was mentioned above in the case of confined herbs), or 

 from the irritation and exasperation of the fiery spirit by the water, so 

 as to occasion a kind of conflict and reaction. But which is the real 

 cause will appear more readily if oil be substituted for water. For oil 

 will serve as well as water to combine the enclosed spirit, and will not 

 irritate it. Moreover the experiment must be extended over a wider 

 field, by calling into use the ashes and cinders of different bodies, and 

 by applying different liquids. 



To the Nineteenth. 



25. To this Instance is subjoined the negative of other metals which 

 are softer and more reducible. For gold leaf, dissolved by means of 

 aqua regia, gives out no heat to the touch during solution ; nor does 



