NOW At ORGANUAf. 319 



20. A very great interval is found to exist between the heat of 

 animals and even of the rays of the heavenly bodies (as they come to 

 us), on the one hand, and flame, though of the mildest kind, and all 

 ignited bodies, and liquids, and air itself, when highly heated by fire, 

 on the other. For the flame of spirit of wine, which is especially rare 

 when uncondenscd, can still inflame straw, linen, or paper ; which the 

 heat of animals, or of the sun, can never do without the aid of burning 

 lenses. 



21. Now of Flame and Ignited Substances there arc very many 

 degrees as to strength and weakness of heat. But on these points no 

 diligent inquiry has been made, so that we must perforce pass lightly 

 by them. But among flames that of spirit of wine seems to be the 

 mildest, unless, perchance, ihe ignis fa/uus, and flames or coruscations 

 arising from the perspiration of animals, be milder. Next to this we 

 think, comes flame derived from vegetables which are light and porous, 

 such as straw, reeds, and dry leaves ; from which the flame of hair or 

 feathers differs but little. iNicxt, perhaps, comes flame from wood, 

 especially those kinds which have not much resin or pitch, excepting 

 that flame from small-sized wood (such as is commonly tied up in 

 faggots) is gentler than that from the trunks and roots of trees. And 

 this may be tried in the common furnaces for smelting iron, in which 

 fire made with faggots and boughs of trees is not very useful. Next 

 comes (as we think; flame from oil, tallow, wax, and such like oily and 

 fatty substances, which have no great sharpness. But the strongest 

 degree of heat is found in pitch and resin, and above all in sulphur, 

 camphor, naphtha, petroleum, and salts (after their raw matter has been 

 voided), and in their compounds, as gunpowder, (Ireck fire (which they 

 commonly call wild fire), and its different kinds, which possess so 

 obstinate a heat as not easily to be extinguished by water. 



22. We think also that flame which results from some imperfect 

 metals is very powerful and severe. But of all these let further inquiry 

 be made. 



23. The flame of destructive lightning appears to exceed all the 

 foregoing, so that it has sometimes melted wrought iron itself into 

 drops, a thing which these other flames cannot do. 



24. In ignited substances, again, there are different degrees of heat, 

 about which no diligent inquiry has been made. We think that the 

 weakest heat is that arising from tinder, which we use to kindle flame, 

 and likewise that of spongy wood, or fine dry tow, which is employed 

 ito fire cannon. Next to this comes ignited wood and coal, and 

 -also bricks heated to redness, and the like. But the most vehement 

 .heat we think to be that of ignited metals, such as iron, copper, &c. 

 .But concerning these, also, further inquiry must be made. 



25. Some substances in a state of ignition arc found to be far hotter 

 than some kinds of flame. For ignited iron is much hotter and more 

 consuming than the flame of spirit of wine. 



26. Of those substances which are not ignited, but only heated by 

 ifire, as boiling water, and air shut up in rcvci beratories, some are found 

 to surpass in heat many flames and ignited substances. 



