loa SEVENTEENTH CENTURY. PT. ill. 



f 



until you have exhausted all the facts which it is supposed 

 to explain. 



For example, if you require to understand what heat is, 

 and how it acts, you must not be satisfied, he says, by merely 

 making a few experiments on the heat of the sun and that 

 of fire, and trying from these to lay down some general rule 

 of how heat works. * No, you must examine it in the sun's 

 rays both when they fall direct and when they are reflected ; 

 in fiery meteors, in lightning, in volcanoes, and in all kinds 

 of flame ; in heated solids, in hot springs, in boiling liquids, 

 in steam and vapours, in bodies which retain heat, such as 

 wool and fur ; in bodies which you have held near the fire, 

 and in bodies heated by rubbing ; in sparks produced by 

 friction, as at the axles of wheels ; in the heating of damp 

 grass, as in haystacks ; in chemical changes, as when iron 

 is dissolved by acids ; in animals ; in the effects of spirits of 

 wine ; in aromatics, as for example pepper, when you place 

 it on your tongue. In fact, you must study every property 

 of heat down to the action of very cold water, which makes 

 your flesh glow when poured upon it When you have 

 made a list,' says Bacon, * of all the conditions under which 

 heat appears, or is modified, of the causes which produce 

 it, and of the effects which it brings about, then you may 

 begin to speak of its nature and its laws, and may perhaps 

 have some clear and distinct ideas about it' 



You will see at once that this method of Bacon's had 

 been followed already to a great extent by Copernicus, Tycho 

 Brahe, Galileo, and Kepler ; but Bacon was the first to insist 

 upon it as the only rule to follow, and in doing this he ren- 

 dered a great service to science. 



Descartes' Condemnation of Ignorant Assertion. 

 - Ren Descartes, by his philosophy, assisted science in 

 another way. He was a Frenchman, born in Touraine in 



