104 SEVENTEENTH CENTURY. PT. HI. 



true way to cultivate science is to be quite certain of each 

 step before going on further, nor to be satisfied with any 

 general law 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 re- 

 flected ; in fiery meteors, in lightning, in volcanoes, and in 

 all kinds of flame ; in heated solids, in hot springs, in boil- 

 ing 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 heat- 

 ing of damp grass, as in haystacks ; in chemical changes, as 

 when iron is dissolved by acids ; in animals ; in the effects 

 of spirits of \vine ; 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 ilesh 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 rendered a great service to science. 



