NOVUM ORGAN UM. 157 



This momentary nature either arises from the cessation of 

 the cause which first produced it, as in light, sounds, and 

 violent motions as they are termed, or flame may be ca 

 pable by its own nature of duration, but is subjected to 

 some violence from the contrary natures which surround it, 

 and is destroyed. 



We may, therefore, adopt the following instance of the 

 cross. We see to what a height the flames rise in great 

 conflagrations ; for as the base of the flame becomes more 

 extensive, its vertex is more lofty. It appears, then, that 

 the commencement of the extinction takes place at the sides, 

 where the flame is compressed by the air, and is ill at ease. 

 But the centre of the flame, which is untouched by the air, 

 and surrounded by flame, continues the same, and is not 

 extinguished, until compressed by degrees by the air at 

 tacking it from the sides. All flame, therefore, is pyramidal, 

 having its base near the source, and its vertex pointed from 

 its being resisted by the air, and not supplied from the 

 source. On the contrary, the smoke, which is narrow at 

 the base, expands in its ascent, and resembles an inverted 

 pyramid ; because the air admits the smoke, but compresses 

 the flame ; for let no one dream that the lighted flame is 

 air, since they are clearly heterogeneous. 



The instance of the cross will be more accurate, if the 

 experiment can be made by flames of different colours. 

 Take, therefore, a small metal sconce, and place a lighted 

 taper in it, then put it in a basin, and pour a small quan 

 tity of spirits of wine round the sconce, so as not to reach 

 its edge, and light the spirit. Now the flame of the spirit 

 will be blue, and that of the taper yellow ; observe, there 

 fore, whether the latter (which can easily be distinguished 

 from the former by its colour, for flames do not mix imme 

 diately as liquids do), continue pyramidal, or tend more to 

 a globular figure, since there is nothing to destroy or com 

 press it. If the latter result be observed, it must be consi 

 dered as settled, that flame continues positively the same, 

 whilst inclosed within another flame, and not exposed to 

 the resisting force of the air. 



Let this suffice for the instances of the cross. We have 

 dwelt the longer upon them in order gradually to teach and 

 accustom mankind to judge of nature by these instances, 

 and enlightening experiments, and not by probable reasons. 



37. We will treat of the instances of Divorce as the fifteenth 

 of our prerogative instances. They indicate the separation 

 of natures of the most common occurrence. They differ, 

 however, from those subjoined to the accompanying in- 



